Plug Power (PLUG) 10-K 14 May 21 2020 FY Annual report Financial data

Document and Entity Information

Document and Entity Information - USD ($)	12 Months Ended
	Dec. 31, 2020	May 06, 2021	Jun. 30, 2020
Document and Entity Information:
Document Type	10-K
Document Annual Report	true
Document Transition Report	false
Document Period End Date	Dec. 31, 2020
Entity File Number	1-34392
Entity Registrant Name	Plug Power Inc
Entity Incorporation, State or Country Code	DE
Entity Tax Identification Number	22-3672377
Entity Address, Address Line One	968 ALBANY SHAKER ROAD
Entity Address, City or Town	LATHAM
Entity Address, State or Province	NY
Entity Address, Postal Zip Code	12110
City Area Code	518
Local Phone Number	782-7700
Title of 12(b) Security	Common Stock, par value $.01 per share
Trading Symbol	PLUG
Security Exchange Name	NASDAQ
Entity Current Reporting Status	No
Entity Interactive Data Current	No
Entity Filer Category	Large Accelerated Filer
Entity Small Business	false
Entity Emerging Growth Company	false
ICFR Auditor Attestation Flag	true
Entity Shell Company	false
Entity Common Stock, Shares Outstanding		568,317,504
Current Fiscal Year End Date	--12-31
Document Fiscal Period Focus	FY
Document Fiscal Year Focus	2020
Entity Central Index Key	0001093691
Amendment Flag	false
Entity Well-known Seasoned Issuer	No
Entity Voluntary Filers	No
Entity Public Float			$ 2,733,184,540

CONSOLIDATED BALANCE SHEETS

CONSOLIDATED BALANCE SHEETS	Dec. 31, 2019USD ($)
Current assets:
Cash and cash equivalents	$ 139,496,000
Restricted cash	54,813,000
Accounts receivable	25,768,000
Inventory	72,391,000
Prepaid expenses and other current assets	21,192,000
Total current assets	313,660,000
Restricted cash	175,191,000
Property, plant, and equipment, net	14,959,000
Right of use assets related to finance leases, net	1,714,000
Right of use assets related to operating leases, net	63,266,000
Equipment related to power purchase agreements and fuel delivered to customers, net	67,769,000
Goodwill	8,842,000
Intangible assets, net	5,539,000
Other assets	8,573,000
Total assets	659,513,000
Current liabilities:
Accounts payable	40,376,000
Accrued expenses	14,409,000
Deferred revenue	11,691,000
Operating lease liabilities	9,428,000
Finance lease liabilities	226,000
Finance obligations	24,667,000
Current portion of long-term debt	26,461,000
Other current liabilities	6,704,000
Total current liabilities	133,962,000
Deferred revenue	23,170,000
Operating lease liabilities	50,937,000
Finance lease liabilities	2,011,000
Finance obligations	119,422,000
Convertible senior notes, net	110,431,000
Long-term debt	85,708,000
Other liabilities	2,818,000
Total liabilities	528,459,000
Stockholders' equity:
Common stock, $0.01 par value per share; 750,000,000 shares authorized; Issued (including shares in treasury): 473,977,469 at December 31, 2020 and 318,637,560 at December 31, 2019	3,186,000
Additional paid-in capital	1,506,953,000
Accumulated other comprehensive income	1,288,000
Accumulated deficit	(1,350,307,000)
Less common stock in treasury: 15,926,068 at December 31, 2020 and 15,259,045 at December 31, 2019	(31,216,000)
Total stockholders' equity	129,904,000
Total liabilities, redeemable preferred stock, and stockholders' equity	659,513,000
Series C Redeemable Convertible Preferred Stock
Redeemable preferred stock:
Preferred stock	709,000
Series E Convertible Preferred Stock
Redeemable preferred stock:
Preferred stock	$ 441,000

CONSOLIDATED BALANCE SHEETS (Pa

CONSOLIDATED BALANCE SHEETS (Parenthetical) - USD ($) $ in Thousands	Dec. 31, 2020	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019
Common stock, par value (in dollars per share)	$ 0.01	$ 0.01	$ 0.01	$ 0.01	$ 0.01	$ 0.01	$ 0.01	$ 0.01
Common stock, shares authorized	750,000,000				750,000,000
Common stock, shares issued	473,977,469				318,637,560
Common stock in treasury, shares	15,926,068				15,259,045
Series C Redeemable Convertible Preferred Stock
Redeemable convertible Preferred Stock, par value (in dollars per share)	$ 0.01			$ 0.01	$ 0.01	$ 0.01	$ 0.01	$ 0.01
Redeemable convertible Preferred Stock, shares authorized	10,431			10,431,000	10,431	10,431,000	10,431,000	10,431,000
Redeemable convertible Preferred Stock, shares issued	0			2,620,000	2,620	2,620,000	2,620,000	2,620,000
Redeemable convertible Preferred Stock, shares outstanding	0			2,620,000	2,620	2,620,000	2,620,000	2,620,000
Redeemable convertible Preferred Stock, aggregate involuntary liquidation preference (in dollars)	$ 16,664			$ 16,664	$ 16,664		$ 16,664	$ 16,664
Series E Convertible Preferred Stock
Redeemable convertible Preferred Stock, par value (in dollars per share)	$ 0.01				$ 0.01
Redeemable convertible Preferred Stock, shares authorized	35,000				35,000
Redeemable convertible Preferred Stock, shares issued	0				500
Redeemable convertible Preferred Stock, shares outstanding	0				500

CONSOLIDATED STATEMENTS OF OPER

CONSOLIDATED STATEMENTS OF OPERATIONS - USD ($) $ in Thousands	3 Months Ended								6 Months Ended		9 Months Ended		12 Months Ended
	Dec. 31, 2020	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Jun. 30, 2020	Jun. 30, 2019	Sep. 30, 2020	Sep. 30, 2019	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Net revenue:
Net revenue	$ 309,099	$ 107,048	$ 67,995	$ 40,819	$ 91,607	$ 59,392	$ 57,466	$ 21,510		$ 78,976		$ 138,368
Net revenue		107,048	67,995	40,819	91,607				$ 108,814		$ 215,862		$ (93,237)	$ 229,975	$ 174,215
Cost of revenue:
Total cost of revenue		135,632	68,010	50,522	83,861	54,892	51,324	29,250	118,532	80,574	254,164	135,466	376,179	219,327	200,219
Gross (loss) profit	(431,114)	(28,584)	(15)	(9,703)	7,746	4,500	6,142	(7,740)	(9,718)	(1,598)	(38,302)	2,902	(469,416)	10,648	(26,004)
Operating expenses:
Research and development		7,386	4,873	4,774	4,882	3,563	3,608	3,006	9,647	6,614	17,033	10,177	27,848	15,059	12,750
Selling, general and administrative		17,210	21,644	11,109	9,973	10,395	13,613	9,221	32,753	22,834	49,963	33,229	79,348	43,202	37,685
Impairment of long-lived assets													6,430
Change in fair value of contingent consideration		1,130									1,130		1,160
Total operating expenses	46,660	25,726	26,517	15,883	14,855	13,958	17,221	12,227	42,400	29,448	68,126	43,406	114,786	58,261	50,435
Operating loss	(477,774)	(54,310)	(26,532)	(25,586)	(7,109)	(9,458)	(11,079)	(19,967)	(52,118)	(31,046)	(106,428)	(40,504)	(584,202)	(47,613)	(76,439)
Interest and other expense, net		(17,551)	(13,462)	(11,846)	(10,999)	(8,273)	(7,965)	(8,454)	(25,308)	(16,419)	(42,859)	(24,692)	(60,484)	(35,691)	(22,750)
Gain (loss) on extinguishment of debt			13,222			(518)		(518)	13,222	(518)	13,222	(518)	17,686	(518)
Change in fair value of common stock warrant liability					72	427	1,706	(2,126)		(420)		7		79	4,286
Loss before income taxes		(71,861)	(26,772)	(37,432)	(18,036)	(17,822)	(17,338)	(30,547)	(64,204)	(47,885)	(136,065)	(65,707)	(627,000)	(83,743)	(94,903)
Income tax benefit		6,644	17,371						17,371		24,015		30,845		9,295
Net loss attributable to the Company		(65,217)	(9,401)	(37,432)	(18,036)	(17,822)	(17,338)	(30,547)	(46,833)	(47,885)	(112,050)	(65,707)	(596,155)	(83,743)	(85,608)
Preferred stock dividends declared, deemed dividends and accretion of discount			(13)	(13)	(1,241)	(544)	(13)	(13)	(26)	(26)	(26)	(570)	(26)	(1,812)	(52)
Net loss attributable to common shareholders	$ (484,105)	$ (65,217)	$ (9,414)	$ (37,445)	$ (19,277)	$ (18,366)	$ (17,351)	$ (30,560)	$ (46,859)	$ (47,911)	$ (112,076)	$ (66,277)	$ (596,181)	$ (85,555)	$ (85,660)
Net loss per share:
Basic and diluted	$ (1.35)	$ (0.18)	$ (0.03)	$ (0.12)	$ (0.07)	$ (0.08)	$ (0.08)	$ (0.14)	$ (0.15)	$ (0.21)	$ (0.34)	$ (0.29)	$ (1.68)	$ (0.36)	$ (0.39)
Weighted average number of common stock outstanding		371,010,544	316,645,050	305,192,201	260,053,150	236,759,521	231,114,868	220,605,068	310,918,626	225,899,224	330,949,265	229,519,323	354,790,106	237,152,780	218,882,337
Sales of fuel cell systems and related infrastructure
Net revenue:
Net revenue	$ (246,171)	$ 83,662	$ 47,746	$ 20,468	$ 69,785	$ 38,883	$ 38,702	$ 2,550	$ 68,214	$ 41,252	$ 151,876	$ 80,135	$ (94,295)	$ 149,920	$ 107,175
Cost of revenue:
Total cost of revenue		69,428	33,888	13,974	47,091	25,183	23,329	2,312	47,862	25,641	117,290	50,824	171,404	97,915	85,205
Services performed on fuel cell systems and related infrastructure
Net revenue:
Net revenue	(29,387)	6,829	6,236	6,521	7,328	6,205	5,341	6,343	12,757	11,684	19,586	17,889	(9,801)	25,217	22,002
Cost of revenue:
Total cost of revenue		9,180	7,773	10,347	11,606	7,802	8,383	6,791	18,120	15,174	27,300	22,976	42,524	34,582	32,271
Provision (benefit) for loss contracts related to service
Cost of revenue:
Total cost of revenue		25,147	706	95	13	206	363	162	801	201	25,948	407	35,473	394	5,345
Power Purchase Agreements
Net revenue:
Net revenue	6,991	6,629	6,579	6,421	6,664	6,520	6,334	6,035	13,000	12,369	19,629	18,889	26,620	25,553	22,569
Cost of revenue:
Total cost of revenue		14,744	14,504	14,771	12,301	10,814	8,829	9,833	29,275	18,662	44,019	29,476	64,640	41,777	41,361
Fuel delivered to customers
Net revenue:
Net revenue	(40,608)	9,831	7,372	7,333	7,779	7,649	7,089	6,582	14,705	13,671	24,536	21,320	(16,072)	29,099	22,469
Cost of revenue:
Total cost of revenue		17,002	11,076	11,254	12,800	11,149	$ 11,146	$ 10,152	22,330	$ 21,298	39,332	32,447	61,815	45,247	$ 36,037
Other
Net revenue:
Net revenue	$ 76	97	62	76	51	135			138		235	135	311	186
Cost of revenue:
Total cost of revenue		$ 131	$ 63	$ 81	$ 50	$ 150			$ 144		$ 275	$ 150	$ 323	$ 200

CONSOLIDATED STATEMENTS OF COMP

CONSOLIDATED STATEMENTS OF COMPREHENSIVE LOSS - USD ($) $ in Thousands	3 Months Ended							6 Months Ended		9 Months Ended		12 Months Ended
	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Jun. 30, 2020	Jun. 30, 2019	Sep. 30, 2020	Sep. 30, 2019	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
CONSOLIDATED STATEMENTS OF COMPREHENSIVE LOSS
Net loss attributable to the Company	$ (65,217)	$ (9,401)	$ (37,432)	$ (18,036)	$ (17,822)	$ (17,338)	$ (30,547)	$ (46,833)	$ (47,885)	$ (112,050)	$ (65,707)	$ (596,155)	$ (83,743)	$ (85,608)
Other comprehensive gain (loss) - foreign currency translation adjustment	687	107	(236)	296	(531)	86	(210)	(129)	(124)	558	(655)	1,163	(296)	(610)
Comprehensive loss attributable to the Company	(64,530)	(9,294)	(37,668)	(17,740)	(18,353)	(17,252)	(30,757)	(46,962)	(48,009)	(111,492)	(66,362)	(594,992)	(84,039)	(86,218)
Preferred stock dividends declared, deemed dividends and accretion of discount		(13)	(13)	(1,241)	(544)	(13)	(13)	(26)	(26)	(26)	(570)	(26)	(1,812)	(52)
Comprehensive loss attributable to common stockholders	$ (64,530)	$ (9,307)	$ (37,681)	$ (18,981)	$ (18,897)	$ (17,265)	$ (30,770)	$ (46,988)	$ (48,035)	$ (111,518)	$ (66,932)	$ (595,018)	$ (85,851)	$ (86,270)

CONSOLIDATED STATEMENTS OF STOC

CONSOLIDATED STATEMENTS OF STOCKHOLDERS' EQUITY (DEFICIT) - USD ($) $ in Thousands	Common Stock	Additional Paid-in-Capital	Accumulated Other Comprehensive Income	Treasury Stock	Accumulated Deficit	Total
Balance (Cumulative effect from adoption of ASC 842) at Dec. 31, 2017					$ 1,200	$ 1,200
Balance at Dec. 31, 2017	$ 2,291	$ 1,250,899	$ 2,194	$ (3,102)	(1,182,053)	70,229
Balance (in shares) at Dec. 31, 2017	229,073,517			587,151
Increase (Decrease) in Stockholders' Equity
Net loss attributable to the Company					(85,608)	(85,608)
Other comprehensive gain (loss)			(610)			(610)
Stock-based compensation	$ 8	8,763				8,771
Stock-based compensation (in shares)	741,216
Stock dividend		52			(52)
Stock dividend (in shares)	29,762
Public offerings, common stock, net	$ 38	6,978				7,016
Public offerings, common stock, net (in shares)	3,804,654
Stock option exercises	$ 5	168		$ (35)		138
Stock option exercises (in shares)	511,412			17,606
Equity component of convertible senior notes, net of issuance costs and income tax (benefit) expense		28,586				28,586
Purchase of capped calls		(16,000)				(16,000)
Purchase of common stock forward				$ (27,500)		(27,500)
Purchase of common stock forward (in shares)				14,397,906
Exercise of warrants (in shares)	100
Provision for common stock warrants		10,190				10,190
Balance at Dec. 31, 2018	$ 2,342	1,289,636	1,584	$ (30,637)	(1,266,513)	(3,588)
Balance (in shares) at Dec. 31, 2018	234,160,661			15,002,663
Increase (Decrease) in Stockholders' Equity
Net loss attributable to the Company						(30,547)
Balance at Mar. 31, 2019	$ 2,445	1,316,815	1,374	$ (30,637)	(1,297,072)	(7,075)
Balance (in shares) at Mar. 31, 2019	244,537,235			15,002,663
Balance at Dec. 31, 2018	$ 2,342	1,289,636	1,584	$ (30,637)	(1,266,513)	(3,588)
Balance (in shares) at Dec. 31, 2018	234,160,661			15,002,663
Increase (Decrease) in Stockholders' Equity
Net loss attributable to the Company						(47,885)
Balance at Jun. 30, 2019	$ 2,470	1,325,381	1,460	$ (30,681)	(1,314,425)	(15,795)
Balance (in shares) at Jun. 30, 2019	246,975,173			15,020,437
Balance at Dec. 31, 2018	$ 2,342	1,289,636	1,584	$ (30,637)	(1,266,513)	(3,588)
Balance (in shares) at Dec. 31, 2018	234,160,661			15,002,663
Increase (Decrease) in Stockholders' Equity
Net loss attributable to the Company						(65,707)
Balance at Sep. 30, 2019	$ 2,540	1,340,781	929	$ (31,216)	(1,332,259)	(19,225)
Balance (in shares) at Sep. 30, 2019	253,982,578			15,259,045
Balance at Dec. 31, 2018	$ 2,342	1,289,636	1,584	$ (30,637)	(1,266,513)	(3,588)
Balance (in shares) at Dec. 31, 2018	234,160,661			15,002,663
Increase (Decrease) in Stockholders' Equity
Net loss attributable to the Company					(83,743)	(83,743)
Other comprehensive gain (loss)			(296)			(296)
Stock-based compensation	$ 19	10,871				10,890
Stock-based compensation (in shares)	1,876,503
Stock dividend		52			(52)
Stock dividend (in shares)	19,286
Public offerings, common stock, net	$ 622	157,722				158,344
Public offerings, common stock, net (in shares)	62,333,585
Stock option exercises	$ 12	1,784		$ (579)		1,217
Stock option exercises (in shares)	1,151,307			256,382
Exercise of warrants	$ 53	14,099				14,152
Exercise of warrants (in shares)	5,250,750
Provision for common stock warrants		6,513				6,513
Accretion of discount, preferred stock		(1,978)				(1,978)
Conversion of preferred stock	$ 138	28,254				28,392
Conversion of preferred stock (in shares)	13,845,468
Balance at Dec. 31, 2019	$ 3,186	1,506,953	1,288	$ (31,216)	(1,350,307)	$ 129,904
Balance (in shares) at Dec. 31, 2019	318,637,560			15,259,045		318,637,560
Balance at Mar. 31, 2019	$ 2,445	1,316,815	1,374	$ (30,637)	(1,297,072)	$ (7,075)
Balance (in shares) at Mar. 31, 2019	244,537,235			15,002,663
Increase (Decrease) in Stockholders' Equity
Net loss attributable to the Company						(17,338)
Balance at Jun. 30, 2019	$ 2,470	1,325,381	1,460	$ (30,681)	(1,314,425)	(15,795)
Balance (in shares) at Jun. 30, 2019	246,975,173			15,020,437
Increase (Decrease) in Stockholders' Equity
Net loss attributable to the Company						(17,822)
Balance at Sep. 30, 2019	$ 2,540	1,340,781	929	$ (31,216)	(1,332,259)	(19,225)
Balance (in shares) at Sep. 30, 2019	253,982,578			15,259,045
Increase (Decrease) in Stockholders' Equity
Net loss attributable to the Company						(18,036)
Balance at Dec. 31, 2019	$ 3,186	1,506,953	1,288	$ (31,216)	(1,350,307)	$ 129,904
Balance (in shares) at Dec. 31, 2019	318,637,560			15,259,045		318,637,560
Increase (Decrease) in Stockholders' Equity
Net loss attributable to the Company						$ (37,432)
Balance at Mar. 31, 2020	$ 3,222	1,519,094	1,052	$ (31,224)	(1,387,752)	104,392
Balance (in shares) at Mar. 31, 2020	322,220,469			15,261,007
Balance at Dec. 31, 2019	$ 3,186	1,506,953	1,288	$ (31,216)	(1,350,307)	$ 129,904
Balance (in shares) at Dec. 31, 2019	318,637,560			15,259,045		318,637,560
Increase (Decrease) in Stockholders' Equity
Net loss attributable to the Company						$ (46,833)
Balance at Jun. 30, 2020	$ 3,482	1,658,438	1,159	$ (31,359)	(1,397,160)	234,560
Balance (in shares) at Jun. 30, 2020	348,201,792			15,292,591
Balance at Dec. 31, 2019	$ 3,186	1,506,953	1,288	$ (31,216)	(1,350,307)	$ 129,904
Balance (in shares) at Dec. 31, 2019	318,637,560			15,259,045		318,637,560
Increase (Decrease) in Stockholders' Equity
Net loss attributable to the Company						$ (112,050)
Balance at Sep. 30, 2020	$ 4,061	2,083,169	1,846	$ (40,434)	(1,462,377)	586,265
Balance (in shares) at Sep. 30, 2020	406,123,816			15,926,068
Balance at Dec. 31, 2019	$ 3,186	1,506,953	1,288	$ (31,216)	(1,350,307)	$ 129,904
Balance (in shares) at Dec. 31, 2019	318,637,560			15,259,045		318,637,560
Increase (Decrease) in Stockholders' Equity
Net loss attributable to the Company					(596,155)	$ (596,155)
Other comprehensive gain (loss)			1,163			1,163
Stock-based compensation	$ 4	17,131				17,135
Stock-based compensation (in shares)	439,649
Stock dividend		26			(26)
Stock dividend (in shares)	5,156
Public offerings, common stock, net	$ 790	1,270,872				$ 1,271,662
Public offerings, common stock, net (in shares)	78,976,250					79,000,000
Stock option exercises	$ 181	41,060		$ (9,218)		$ 32,023
Stock option exercises (in shares)	18,056,200			667,023
Equity component of convertible senior notes, net of issuance costs and income tax (benefit) expense		100,761				100,761
Purchase of capped calls		(16,253)				(16,253)
Termination of capped calls		24,158				24,158
Exercise of warrants	$ 52	(52)
Exercise of warrants (in shares)	5,180,457
Provision for common stock warrants		439,915				439,915
Accretion of discount, preferred stock		(29)				(29)
Conversion of preferred stock	$ 30	1,149				1,179
Conversion of preferred stock (in shares)	2,998,526
Conversion of 5.5% and 7.5% Convertible Senior Notes	$ 306	62,247				62,553
Conversion of 5.5% and 7.5% Convertible Senior Notess (in shares)	30,615,615
Repurchase of 5.5% Convertible Senior Notes, net of income tax benefit	$ 94	(50,864)				(50,770)
Repurchase of 5.5% Convertible Senior Notes, net of income tax benefit (in shares)	9,409,591
Shares issued for acquisitions	$ 97	49,576				49,673
Shares issued for acquisitions (in shares)	9,658,465
Balance at Dec. 31, 2020	$ 4,740	3,446,650	2,451	$ (40,434)	(1,946,488)	$ 1,466,919
Balance (in shares) at Dec. 31, 2020	473,977,469			15,926,068		473,977,469
Balance at Mar. 31, 2020	$ 3,222	1,519,094	1,052	$ (31,224)	(1,387,752)	$ 104,392
Balance (in shares) at Mar. 31, 2020	322,220,469			15,261,007
Increase (Decrease) in Stockholders' Equity
Net loss attributable to the Company						(9,401)
Balance at Jun. 30, 2020	$ 3,482	1,658,438	1,159	$ (31,359)	(1,397,160)	234,560
Balance (in shares) at Jun. 30, 2020	348,201,792			15,292,591
Increase (Decrease) in Stockholders' Equity
Net loss attributable to the Company						(65,217)
Balance at Sep. 30, 2020	$ 4,061	2,083,169	1,846	$ (40,434)	(1,462,377)	$ 586,265
Balance (in shares) at Sep. 30, 2020	406,123,816			15,926,068
Increase (Decrease) in Stockholders' Equity
Public offerings, common stock, net (in shares)						4,400,000
Balance at Dec. 31, 2020	$ 4,740	$ 3,446,650	$ 2,451	$ (40,434)	$ (1,946,488)	$ 1,466,919
Balance (in shares) at Dec. 31, 2020	473,977,469			15,926,068		473,977,469

CONSOLIDATED STATEMENTS OF ST_2

CONSOLIDATED STATEMENTS OF STOCKHOLDERS' EQUITY (DEFICIT) (Parenthetical)	Dec. 31, 2020	Jul. 01, 2020	May 31, 2020	May 29, 2020	May 18, 2020	Sep. 30, 2019	Mar. 31, 2018
Interest rate (as a percent)			3.50%
5.5% Convertible Senior Notes
Interest rate (as a percent)	5.50%		5.50%		5.50%		5.50%
3.75% Convertible Senior Notes
Interest rate (as a percent)	3.75%		3.75%	3.75%	3.75%
7.5% Convertible Senior Note
Interest rate (as a percent)	7.50%	7.50%				7.50%

CONSOLIDATED STATEMENTS OF CASH

CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Operating Activities
Net loss attributable to the Company	$ (596,155)	$ (83,743)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation of long-lived assets	14,434	11,938
Amortization of intangible assets	1,135	698
Stock-based compensation	17,135	10,890
(Gain) loss on extinguishment of debt	(17,686)	518
Provision for bad debts and other assets	700	1,981
Amortization of debt issuance costs and discount on convertible senior notes	17,061	9,006
Provision for common stock warrants	425,047	6,513
Loss on disposal of leased assets		212
Fair value adjustment to contingent consideration	(1,160)
Impairment of long-lived assets	6,430
Change in fair value of common stock warrant liability		(79)
Deferred income tax benefit	(30,845)
Loss (benefit) on service contracts	33,125	(1,643)
Changes in operating assets and liabilities that provide (use) cash:
Accounts receivable	(15,701)	10,594
Inventory	(63,389)	(24,633)
Prepaid expenses and other assets	(18,401)	(8,110)
Accounts payable, accrued expenses, and other liabilities	51,880	17,234
Deferred revenue	20,914	(4,700)
Net cash used in operating activities	(155,476)	(53,324)
Investing Activities
Purchases of property, plant and equipment	(22,526)	(5,683)
Purchase of intangible assets	(1,957)	(2,404)
Purchases of equipment related to PPA and equipment related to fuel delivered to customers	(25,738)	(6,532)
Net cash paid for acquisitions	(45,113)
Proceeds from sale of leased assets		375
Net cash used in investing activities	(95,334)	(14,244)
Financing Activities
Proceeds from issuance of preferred stock and warrants, net of transaction costs		14,089
Proceeds from public offerings, net of transaction costs	1,271,714	158,343
Proceeds from exercise of stock options	32,023	1,217
Payments for redemption of preferred stock		(4,040)
Proceeds from issuance of convertible senior notes, net	205,098	39,052
Repurchase of convertible senior notes	(90,238)
Purchase of capped calls and common stock forward	(16,253)
Proceeds from borrowing of long-term debt, net of transaction costs		119,186
Proceeds from termination of capped calls	24,158
Principal payments on long-term debt	(48,020)	(25,345)
Proceeds from finance obligations	65,259	83,668
Proceeds from long-term debt, net	99,000	119,186
Repayments of finance obligations	(27,212)	(59,196)
Net cash provided by financing activities	1,515,529	326,974
Effect of exchange rate changes on cash	65	(59)
Increase in cash, cash equivalents and restricted cash	1,264,784	259,347
Cash, cash equivalents, and restricted cash beginning of period	369,500	110,153
Cash, cash equivalents, and restricted cash end of period	1,634,284	369,500
Supplemental disclosure of cash flow information
Cash paid for interest	28,942	19,180
Summary of non-cash investing and financing activity
Recognition of right of use assets	55,651	52,924
Net tangible assets acquired in a business combination	8,751
Intangible assets acquired in a business combination	32,268
Conversion of convertible notes to common stock	62,553
Conversion of preferred stock to common stock	$ 1,179	$ 28,392

Nature of Operations

Nature of Operations	12 Months Ended
	Dec. 31, 2020
Nature of Operations
Nature of Operations	1. Nature of Operations ​ Description of Business ​ Plug Power is facilitating the paradigm shift to an increasingly electrified world by innovating cutting-edge hydrogen and fuel cell solutions. In our core business, we provide and continue to develop commercially-viable hydrogen and fuel cell product solutions to replace lead-acid batteries in electric material handling vehicles and industrial trucks for some of the world’s largest retail-distribution and manufacturing businesses. We are focusing our efforts on industrial mobility applications, including electric forklifts and electric industrial vehicles, at multi-shift high volume manufacturing and high throughput distribution sites where we believe our products and services provide a unique combination of productivity, flexibility, and environmental benefits. Additionally, we manufacture and sell fuel cell products to replace batteries and diesel generators in stationary backup power applications. These products have proven valuable with telecommunications, transportation, and utility customers as robust, reliable, and sustainable power solutions. ​ Our current products and services include: GenDrive: GenDrive is our hydrogen fueled PEM fuel cell system providing power to material handling electric vehicles, including class 1, 2, 3 and 6 electric forklifts, Automated Guided Vehicles (“AGVs”) and ground support equipment; GenFuel: GenFuel is our liquid hydrogen fueling delivery, generation, storage, and dispensing system; GenCare: GenCare is our ongoing ‘internet of things’-based maintenance and on-site service program for GenDrive fuel cell systems, GenSure fuel cell systems, GenFuel hydrogen storage and dispensing products and ProGen fuel cell engines; GenSure: GenSure is our stationary fuel cell solution providing scalable, modular Proton Exchange Membrane (PEM) fuel cell power to support the backup and grid-support power requirements of the telecommunications, transportation, and utility sectors; GenSure High Power Fuel Cell Platform will support large scale stationary power and data center markets. GenKey: GenKey is our vertically integrated “turn-key” solution combining either GenDrive or GenSure fuel cell power with GenFuel fuel and GenCare aftermarket service, offering complete simplicity to customers transitioning to fuel cell power; ProGen: ProGen is our fuel cell stack and engine technology currently used globally in mobility and stationary fuel cell systems, and as engines in electric delivery vans. This includes the Plug Power MEA (membrane electrode assembly), a critical component of the fuel cell stack used in zero-emission fuel cell electric vehicle engines; and GenFuel Electrolyzers: GenFuel electrolyzers are modular, scalable hydrogen generators optimized for clean hydrogen production. We provide our products worldwide through our direct product sales force, and by leveraging relationships with original equipment manufacturers (“OEMs”) and their dealer networks. Plug Power is targeting Asia and Europe for expansion in adoption. Europe has rolled out ambitious targets for the hydrogen economy and Plug Power is executing on its strategy to become one of the European leaders. This includes a targeted account strategy for material handling as well as securing strategic partnerships with European original equipment manufacturers, or OEMs, energy companies, utility leaders and accelerating our electrolyzer business. We manufacture our commercially viable products in Latham, New York, Rochester, New York and Spokane, Washington and support liquid hydrogen generation and logistics in Charleston, Tennessee. ​ Liquidity ​ During 2020, the Company issued and sold 79.0 million shares in two separate, registered equity offerings, resulting in net proceeds of approximately $1.3 billion. See Note 16, “Stockholders’ Equity, as restated.” In May 2020, the Company issued $212.5 million in aggregate principal amount of 3.75% Convertible Senior Notes due June 1, 2025, in a private placement to qualified institutional buyers. See Note 15, “Convertible Senior Notes,” as amended. ​ As of December 31, 2020, the Company had $1.3 billion of cash and cash equivalents and $321.9 million of restricted cash. In January and February 2021, the Company issued and sold in another registered equity offering an aggregate of 32.2 million shares of its common stock at a purchase price of $65.00 per share for net proceeds of approximately $1.8 billion. Furthermore in February 2021, the Company completed the previously announced sale of its common stock in connection with a strategic partnership with SK Holdings Co., Ltd. (“SK Holdings”) to accelerate the use of hydrogen as an alternative energy source in Asian markets. The Company sold 54,996,188 shares of its common stock to a subsidiary of SK Holdings at a purchase price of $29.2893 per share, or an aggregate purchase price of approximately $1.6 billion. See Note 23, “Subsequent Events,” for more details. ​ The Company has continued to experience negative cash flows from operations and net losses. The Company incurred net losses attributable to common stockholders of $596.2 million, $85.6 million and $85.7 million for the years ended December 31, 2020, 2019, and 2018, respectively. The Company’s cash used in operations totaled $155.5 million, $53.3 million, and $58.4 million for the year ended December 31, 2020, 2019 and 2018, and has an accumulated deficit of $1.9 billion at December 31, 2020. ​ The Company’s significant obligations consisted of the following as of December 31, 2020: ​ (i) Operating and finance leases totaling $113.9 million and $5.4 million, respectively, of which $14.3 million and $903 thousand, respectively, are due within the next 12 months. These leases are primarily related to sale/leaseback agreements entered into with various financial institutions to facilitate the Company’s commercial transactions with key customers. ​ (ii) Finance obligations totaling $181.6 million of which approximately $32.7 million is due within the next 12 months. Finance obligations consist primarily of debt associated with the sale of future revenues and failed sale/leaseback transactions. ​ (iii) Long-term debt, primarily related to the Company’s loan and security agreement (Loan Agreement) with Generate Lending, LLC (Generate Capital) totaling $175.4 million of which $25.4 million is classified as short term on the consolidated balance sheets. See Note 14, “Long-Term Debt”, for more details. ​ (iv) Convertible senior notes totaling $85.6 million at December 31, 2020. See Note 15, “Convertible Senior Notes, as restated” for more details. ​ The Company believes that its current working capital of $1.4 billion at December 31, 2020, which includes unrestricted cash and cash equivalents of $1.3 billion, together with proceeds from the January 2021 registered equity offering and SK group investment, will provide sufficient liquidity to fund operations for a least one year after the date the financial statements are issued. ​ The Company plans to invest a portion of its available cash to expand its current production and manufacturing capacity and to fund strategic acquisitions and partnerships and capital projects. Future use of the Company’s funds is discretionary and the Company believes that its future working capital and cash position will be sufficient to fund operations even after these growth investments. ​ ​

Restatement of Previously Issue

Restatement of Previously Issued Consolidated Financial Statements	12 Months Ended
	Dec. 31, 2020
Restatement of Previously Issued Consolidated Financial Statements
Restatement of Previously Issued Consolidated Financial Statements	2. Restatement of Previously Issued Consolidated Financial Statements ​ Restatement Background ​ On March 12, 2021, management in concurrence with the Company’s Audit Committee of the Board of Directors (the “Audit Committee”), concluded that our 2019 and 2018 consolidated financial statements, included in our Annual Reports on Form 10-K as of and for the fiscal years ended December 31, 2019 and 2018, and our unaudited consolidated financial statements as of and for each of the first three quarterly periods in 2020 and all quarterly periods in 2019, included in our Quarterly Reports on Form 10-Q for the respective periods, (collectively the “Prior Period Financial Statements”) should no longer be relied upon due to misstatements that are described below, and that we would restate such financial statements to make the necessary accounting corrections. In addition, we have restated the statement of operations for the three months ended December 31, 2019, which was previously disclosed as a note in its form 10-K for the year ended December 31, 2019. Details of the restated consolidated financial statements as of and for the fiscal years ended December 31, 2019 and 2018 are provided below (“Restatement Items”). In addition, details of the restated interim financial information for each of the quarterly periods in fiscal 2019 and for the first three quarters of fiscal 2020, are presented in Note 3, “Unaudited Quarterly Financial data and Restatement of Previously Issued Unaudited Interim Condensed Consolidated Financial Statements”. The Company evaluated the materiality of these errors both qualitatively and quantitatively in accordance with Staff Accounting Bulletin (“SAB”) No. 99, Materiality and SAB No. 108, Considering the Effects of Prior Year Misstatements in Current Year Financial Statements, and determined the effect of these corrections were material to the Prior Period Financial Statements. As a result of the material misstatements, we have restated our Prior Period Financial Statements, in accordance with ASC 250, Accounting Changes and Error Corrections (the “Restated Financial Statements”). ​ The Restatements Items reflect adjustments to correct errors on the balance sheets to reduce the carrying amount of certain right of use assets and lease liabilities associated with leases, increase the loss accrual relating to service contracts, a reclassification of costs resulting in a decrease in Operating expenses - Research and development expense and a corresponding increase in Cost of revenue, the recording of a deemed dividend, and correction of a cumulative adjustment upon adoption of a new accounting standard to a correction of an error. The nature and impact of these adjustments are described below and also detailed in the tables below. Also see Note 3, “Unaudited Quarterly Financial Data and Restatement of Previously Issued Unaudited Interim Condensed Consolidated Financial Statements,” for the impact of these adjustments on each of the quarterly periods. ​ Restatement Items ​ Right of use assets relating to operating leases ​ Loss accrual provision did not consider all relevant historical costs when estimating future service costs when determining whether a loss accrual for extended maintenance contracts was necessary. Additionally, the Company did not consider the service costs related to hydrogen infrastructure, nor the provision for warrants, when estimating the need for a loss accrual on extended maintenance contracts. When properly considering these costs, additional loss accruals for extended maintenance contracts were required to be recorded. The corrections resulted in a ($1.6) million benefit for loss accrual for the year ended December 31, 2019, inclusive of the partial release of the 2018 loss accrual, and a provision for loss accrual of $5.3 million for the year ended December 31, 2018. ​ Research and development expense ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ As of December 31, 2019 ​ As of December 31, 2018 ​ Restatement ​ Restatement ​ ​ Adjustments ​ Adjustments Cost of revenue: ​ ​ ​ ​ ​ ​ Services performed on fuel cell systems and related infrastructure ​ $ 6,986 ​ $ 7,954 Power Purchase Agreements ​ ​ 2,539 ​ ​ 4,264 Sales of fuel cell systems and related infrastructure ​ ​ 1,121 ​ ​ 614 Fuel delivered to customers ​ ​ 8,846 ​ ​ 8,325 Total cost of revenue ​ ​ 19,492 ​ ​ 21,157 ​ ​ ​ ​ ​ ​ ​ Research and development ​ ​ (19,492) ​ ​ (21,157) ​ Series E Redeemable Convertible Preferred Stock Deemed Dividend ​ Adoption of ASC 842 ​ Other adjustments In addition to the Restatement Items, the Company has corrected other adjustments. While these other adjustments are quantitatively immaterial, individually and in the aggregate, because we are correcting for the material errors, we have decided to correct these other adjustments as well. ​ Reclassifications have been made, whenever necessary, to prior period financial statements to conform to the current period presentation for the years ended December 31, 2019 and 2018. ​ Summary impact of Restatement Items and Other Adjustments to Prior Period Financial Statements ​ The following tables present the effect of the Restatement Items, as well as other adjustments, on the Company’s consolidated balance sheets for the periods indicated (in thousands, except per share): ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ As of December 31, 2019 ​ ​ ​ ​ As previously ​ Restatement ​ ​ ​ Restatement ​ ​ Reported ​ Adjustments ​ ​ As Restated ​ References Assets ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Current assets: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Cash and cash equivalents ​ $ 139,496 ​ $ — ​ $ 139,496 ​ ​ Restricted cash ​ ​ 54,813 ​ ​ — ​ ​ 54,813 ​ ​ Accounts receivable ​ 25,448 ​ 320 ​ 25,768 ​ d Inventory ​ 72,391 ​ — ​ 72,391 ​ ​ Prepaid expenses and other current assets ​ 21,192 ​ — ​ 21,192 ​ ​ Total current assets ​ 313,340 ​ 320 ​ 313,660 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Restricted cash ​ 175,191 ​ — ​ 175,191 ​ ​ Property, plant, and equipment, net ​ ​ 14,959 ​ — ​ 14,959 ​ ​ Right of use assets related to finance leases, net ​ ​ — ​ ​ 1,714 ​ ​ 1,714 ​ a Right of use assets related to operating leases, net ​ ​ — ​ ​ 63,266 ​ ​ 63,266 ​ a, b Equipment related to power purchase agreements and fuel delivered to customers, net ​ ​ 244,740 ​ (176,971) ​ 67,769 ​ a, b Goodwill ​ ​ 8,842 ​ ​ — ​ ​ 8,842 ​ ​ Intangible assets, net ​ 5,539 ​ — ​ 5,539 ​ ​ Other assets ​ 8,573 ​ — ​ 8,573 ​ ​ Total assets ​ $ 771,184 ​ $ (111,671) ​ $ 659,513 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Liabilities, Redeemable Preferred Stock, and Stockholders’ Equity ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Current liabilities: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Accounts payable ​ $ 40,376 ​ $ — ​ $ 40,376 ​ ​ Accrued expenses ​ 14,213 ​ 196 ​ 14,409 ​ d Deferred revenue ​ 11,691 ​ — ​ 11,691 ​ ​ Operating lease liabilities ​ ​ — ​ ​ 9,428 ​ ​ 9,428 ​ a, b Finance lease liabilities ​ ​ — ​ ​ 226 ​ ​ 226 ​ a Finance obligations ​ ​ 49,507 ​ ​ (24,840) ​ ​ 24,667 ​ a, b Current portion of long-term debt ​ ​ 26,461 ​ ​ — ​ ​ 26,461 ​ ​ Other current liabilities ​ 8,543 ​ (1,839) ​ 6,704 ​ b, c Total current liabilities ​ 150,791 ​ (16,829) ​ 133,962 ​ ​ Deferred revenue ​ 23,369 ​ (199) ​ 23,170 ​ d Operating lease liabilities ​ ​ — ​ ​ 50,937 ​ ​ 50,937 ​ a, b Finance lease liabilities ​ ​ — ​ ​ 2,011 ​ ​ 2,011 ​ a Finance obligations ​ 265,228 ​ (145,806) ​ 119,422 ​ a, b Convertible senior notes, net ​ ​ 110,246 ​ ​ 185 ​ ​ 110,431 ​ d Long-term debt ​ ​ 85,708 ​ ​ — ​ ​ 85,708 ​ ​ Other liabilities ​ 13 ​ 2,805 ​ 2,818 ​ c Total liabilities ​ 635,355 ​ (106,896) ​ 528,459 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Redeemable preferred stock: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Series C redeemable convertible preferred stock, $0.01 par value per share (aggregate involuntary liquidation preference $16,664 ); 10,431 shares authorized; Issued and outstanding : 2,620 at December 31, 2019 ​ ​ 709 ​ ​ — ​ ​ 709 ​ ​ Series E convertible preferred stock, $0.01 par value per share; Shares authorized: 35,000 at December 31, 2019; Issued and outstanding : 500 at December 31, 2019 ​ ​ 441 ​ ​ — ​ ​ 441 ​ ​ Stockholders’ equity: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Common stock, $0.01 par value per share; 750,000,000 shares authorized; Issued: 318,637,560 at December 31, 2019 ​ 3,186 ​ — ​ 3,186 ​ ​ Additional paid-in capital ​ 1,507,116 ​ (163) ​ 1,506,953 ​ d Accumulated other comprehensive income ​ 1,400 ​ (112) ​ 1,288 ​ d Accumulated deficit ​ (1,345,807) ​ (4,500) ​ (1,350,307) ​ ​ Less common stock in treasury: 15,259,045 at December 31, 2019 ​ ​ (31,216) ​ ​ — ​ ​ (31,216) ​ ​ Total stockholders’ equity ​ 134,679 ​ (4,775) ​ 129,904 ​ ​ Total liabilities, redeemable preferred stock, and stockholders’ equity ​ $ 771,184 ​ $ (111,671) ​ $ 659,513 ​ ​ ​ As of December 31, 2019 (a) The "as previously reported" balances for equipment related to power purchase agreements and fuel delivered to customers, net (previously captioned leased assets, net) and the current and long-term finance obligations have been reclassified to conform to current period presentations, as follows at December 31, 2019: ● $176.0 million was reclassified from equipment related to power purchase agreements and fuel delivered to customers, net to right of use assets related to operating leases, net; ● $1.7 million was reclassified from equipment related to power purchase agreements and fuel delivered to customers, net to right of use asset related to finance leases, net; ● $25.8 million was reclassified from current finance obligations to current operating lease liabilities; ● $145.5 million was reclassified from non-current finance obligations to non-current operating lease liabilities; ● $226 thousand was reclassified from current finance obligations to current finance lease liabilities, respectively; and ● $2.0 million was reclassified from non-current finance obligations to non-current finance lease liabilities (b) The correction of the misstatement associated with the right of use assets relating to operating leases resulted in the following at December 31, 2019: ● the right of use assets related to operating leases, net had a decrease of $112.7 million; ● equipment related to power purchase agreements and lessor property, net had an increase of $767 thousand; ● current operating lease liabilities had a decrease of $16.4 million; ● non-current operating lease liabilities had a decrease of $94.6 million; ● the current finance obligations had a $1.2 million increase; ● the non-current finance obligation had an increase of $1.7 million; and ● other current liabilities decreased $2.7 million. (c) Loss accrual provision: The correction of this misstatement resulted in an increase of $897 thousand to other current liabilities and an increase of $2.8 million to other long-term liabilities at December 31, 2019. (d) Other adjustments: Immaterial adjustments at December 31, 2019 resulted in an increase to accounts receivable of $320 thousand. An increase to accrued expenses of $196 thousand. A decrease to deferred revenue of $199 thousand. An increase in convertible senior notes, net of $185 thousand, and a decrease of $163 thousand to additional paid in capital and a $112 thousand decrease to accumulated other comprehensive income. ​ The following tables present the effect of the Restatement Items, as well as other adjustments, on the Company’s consolidated statements of operations for the periods indicated (in thousands, except share and per share amounts): ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ For the Year Ended December 31, 2019 ​ ​ ​ ​ As Previously ​ Restatement ​ ​ ​ ​ Restatement ​ ​ Reported ​ Adjustments ​ ​ As Restated References Net revenue: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Sales of fuel cell systems and related infrastructure ​ $ 149,884 ​ $ 36 ​ $ 149,920 ​ d Services performed on fuel cell systems and related infrastructure ​ ​ 25,217 ​ ​ — ​ ​ 25,217 ​ ​ Power Purchase Agreements ​ 25,853 ​ (300) ​ 25,553 ​ d Fuel delivered to customers ​ 29,099 ​ — ​ 29,099 ​ ​ Other ​ ​ 186 ​ ​ — ​ ​ 186 ​ ​ Net revenue ​ ​ 230,239 ​ ​ (264) ​ ​ 229,975 ​ ​ Cost of revenue: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Sales of fuel cell systems and related infrastructure ​ 96,859 ​ 1,056 ​ 97,915 ​ a, d Services performed on fuel cell systems and related infrastructure ​ 28,801 ​ 5,781 ​ 34,582 ​ a, c,d Benefit for loss contracts related to service ​ ​ — ​ ​ (394) ​ ​ (394) ​ c Power Purchase Agreements ​ 40,056 ​ 1,721 ​ 41,777 ​ a, b,d Fuel delivered to customers ​ 36,357 ​ 8,890 ​ 45,247 ​ a, d Other ​ 200 ​ — ​ 200 ​ ​ Total cost of revenue ​ 202,273 ​ ​ 17,054 ​ ​ 219,327 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Gross profit ​ 27,966 ​ ​ (17,318) ​ ​ 10,648 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Operating expenses: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Research and development ​ ​ 33,675 ​ ​ (18,616) ​ ​ 15,059 ​ a,d Selling, general and administrative ​ ​ 44,333 ​ ​ (1,131) ​ ​ 43,202 ​ b,d Total operating expenses ​ ​ 78,008 ​ ​ (19,747) ​ ​ 58,261 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Operating loss ​ ​ (50,042) ​ ​ 2,429 ​ ​ (47,613) ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Interest and other expense, net ​ (35,502) ​ (189) ​ (35,691) ​ b,d Change in fair value of common stock warrant liability ​ 79 ​ — ​ 79 ​ ​ Gain (loss) on extinguishment of debt ​ — ​ (518) ​ (518) ​ d ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Loss before income taxes ​ $ (85,465) ​ $ 1,722 ​ $ (83,743) ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Income tax benefit ​ — ​ — ​ — ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Net loss attributable to the Company ​ $ (85,465) ​ $ 1,722 ​ $ (83,743) ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Preferred stock dividends declared, deemed dividends and accretion of discount ​ (52) ​ (1,760) ​ (1,812) ​ e Net loss attributable to common stockholders ​ $ (85,517) ​ $ (38) ​ $ (85,555) ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Net loss per share: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Basic and diluted ​ $ (0.36) ​ ​ ​ ​ $ (0.36) ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Weighted average number of common stock outstanding ​ 237,152,780 ​ ​ ​ ​ 237,152,780 ​ ​ ​ For the year ended December 31, 2019 (a) Research and development: The correction of this misstatement resulted in a net decrease of $19.5 million to research and development, and an increase of $1.1 million to the cost of revenue of fuel cell systems and related infrastructure, an increase of $7 million to the cost of revenue of services performed on fuel cell systems and related infrastructure, an increase of $2.5 million to the cost of power purchase agreements and an increase in the cost of fuel delivered to customers of $8.9 million at December 31, 2019. (b) Right of use asset: The correction of this misstatement resulted in a net decrease to cost of revenue for power purchase agreements of $747 thousand. An increase to selling, general, and administrative expense of $25 thousand, and an increase to interest and other expense, net of $522 thousand. (c) Loss accrual provision: The correction of this misstatement resulted in a net decrease to cost of revenue for services performed on fuel cell systems and related infrastructure of $1.2 million and a net decrease to the provision for loss contracts related to service of $394 thousand for the period ended December 31, 2019. (d) Other adjustments: Immaterial adjustments for the period ended December 31, 2019 resulted in the following: a net increase of $36 thousand to revenue from sales of fuel cell systems and related infrastructure. A net decrease to revenue from power purchase agreements of $300 thousand. A net decrease of $65 thousand to the cost of revenue for sales of fuel cell systems and related infrastructure. A net increase to the cost of revenue for services performed on fuel cell systems and related infrastructure of $44 thousand. A net decrease to cost of revenue for power purchase agreements of $70 thousand. A net increase of $44 thousand to cost of revenue related to fuel delivered to customers. A net increase to research and development expense of $876 thousand. A net decrease to selling general and administrative expense of $1.1 million, a net increase to interest and other expense, net of $185 thousand and an increase of $518 thousand loss on the extinguisment of debt (which was previously reported as interest and other expense, net of $518 thousand). (e) Series E redeemable convertible preferred stock deemed dividend: The correction of this misstatement resulted in a net increase of $1.8 million to preferred stock dividends declared, deemed dividends and accretion of discount. ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ For the Year Ended December 31, 2018 ​ ​ ​ ​ As Previously ​ Restatement ​ ​ ​ ​ Restatement ​ ​ Reported ​ Adjustments ​ ​ As Restated References Net revenue: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Sales of fuel cell systems and related infrastructure ​ $ 107,292 ​ $ (117) ​ $ 107,175 ​ d Services performed on fuel cell systems and related infrastructure ​ ​ 22,002 ​ ​ — ​ ​ 22,002 ​ ​ Power Purchase Agreements ​ 22,869 ​ (300) ​ 22,569 ​ d Fuel delivered to customers ​ 22,469 ​ — ​ 22,469 ​ ​ Net revenue ​ ​ 174,632 ​ ​ (417) ​ ​ 174,215 ​ ​ Cost of revenue: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Sales of fuel cell systems and related infrastructure ​ 84,439 ​ 766 ​ 85,205 ​ a,d Services performed on fuel cell systems and related infrastructure ​ 23,698 ​ 8,573 ​ 32,271 ​ a, d Provision for loss contracts related to service ​ ​ — ​ ​ 5,345 ​ ​ 5,345 ​ c Power Purchase Agreements ​ 36,161 ​ 5,200 ​ 41,361 ​ a, b Fuel delivered to customers ​ 27,712 ​ 8,325 ​ 36,037 ​ a Total cost of revenue ​ 172,010 ​ ​ 28,209 ​ ​ 200,219 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Gross (loss) profit ​ 2,622 ​ ​ (28,626) ​ ​ (26,004) ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Operating expenses: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Research and development ​ ​ 33,907 ​ ​ (21,157) ​ ​ 12,750 ​ a Selling, general and administrative ​ ​ 38,198 ​ ​ (513) ​ ​ 37,685 ​ d Total operating expenses ​ ​ 72,105 ​ ​ (21,670) ​ ​ 50,435 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Operating loss ​ ​ (69,483) ​ ​ (6,956) ​ ​ (76,439) ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Interest and other expense, net ​ (22,135) ​ (615) ​ (22,750) ​ b Change in fair value of common stock warrant liability ​ 4,286 ​ — ​ 4,286 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Loss before income taxes ​ $ (87,332) ​ $ (7,571) ​ $ (94,903) ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Income tax benefit ​ 9,217 ​ 78 ​ 9,295 ​ d ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Net loss attributable to the Company ​ $ (78,115) ​ $ (7,493) ​ $ (85,608) ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Preferred stock dividends declared, deemed dividends and accretion of discount ​ (52) ​ — ​ (52) ​ ​ Net loss attributable to common stockholders ​ $ (78,167) ​ $ (7,493) ​ $ (85,660) ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Net loss per share: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Basic and diluted ​ $ (0.36) ​ ​ ​ ​ $ (0.39) ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Weighted average number of common stock outstanding ​ 218,882,337 ​ ​ ​ ​ 218,882,337 ​ ​ ​ For the year ended December 31, 2018 (a) Research and development: The correction of this misstatement resulted in a net decrease of $21.2 million to research and development, and an increase of $614 thousand to the cost of sales of fuel cell systems and related infrastructure, an increase of $8.0 million to the cost of services performed on fuel cell systems and related infrastructure, an increase of $4.2 million to the cost of power purchase agreements and an increase in the cost of fuel delivered to customers of $8.3 million at December 31, 2018. (b) Right of use asset: The correction of this misstatement resulted in a net increase to cost of revenue for power purchase agreements of $937 thousand, and an increase to interest and other expense, net of $615 thousand. (c) Loss accrual provision: The correction of this misstatement resulted in a net increase to the provision for loss contracts related to service of $5.3 million for the period ended December 31, 2018. (d) Other adjustments: Immaterial adjustments for the period ended December 31, 2018 resulted in the following: a net decrease of $117 thousand to revenue from sales of fuel cell systems and related infrastructure. A net decrease to revenue from power purchase agreements of $300 thousand. A net increase of $152 thousand to the cost of revenue for sales of fuel cell systems and related infrastructure. A net increase to the cost of revenue for services performed on fuel cell systems and related infrastructure of $619 thousand. A net decrease to selling general and administrative expense of $513 thousand and an increase to the income tax benefit of $78 thousand. ​ The following tables present the effect of the Restatement Items, as well as other adjustments, on the Company’s consolidated statements of comprehensive loss for the periods indicated (in thousands): ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ For the year ended December 31, 2019 ​ For the year ended December 31, 2018 ​ ​ ​ ​ As Previously ​ Cumulative ​ ​ ​ As Previously ​ Cumulative ​ ​ ​ ​ Restatement ​ ​ Reported ​ Adjustments ​ As Restated ​ Reported ​ Adjustments ​ ​ As Restated ​ References ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Net loss attributable to the Company ​ $ (85,465) ​ $ 1,722 ​ $ (83,743) ​ $ (78,115) ​ $ (7,493) ​ $ (85,608) ​ ​ Other comprehensive loss - foreign currency translation adjustment ​ (184) ​ (112) ​ (296) ​ (610) ​ — ​ ​ (610) ​ b Comprehensive loss attributable to the Company ​ $ (85,649) ​ $ 1,610 ​ $ (84,039) ​ $ (78,725) ​ $ (7,493) ​ $ (86,218) ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Preferred stock dividends declared, deemed dividends and accretion of discount ​ ​ (52) ​ ​ (1,760) ​ ​ (1,812) ​ ​ (52) ​ ​ — ​ ​ (52) ​ a Comprehensive loss attributable to common stockholders ​ ​ (85,701) ​ ​ (150) ​ ​ (85,851) ​ ​ (78,777) ​ ​ (7,493) ​ ​ (86,270) ​ ​ ​ For the year ened December 31, 2019 and 2018 (a) Series E convertible preferred stock deemed dividend: The correction of this misstatement resulted in a net decrease of $1.8 million to preferred stock dividends declared, deemed dividends and accretion of discount to the period ended December 31, 2019. (b) Other adjustments: Immaterial adjustment for the period ended December 31, 2019 resulted in a net increase of $112 thousand for the other comprehensive loss related to the foreign currency translation adjustment. ​ The following tables present the effect of the Restatement Items, as well as other adjustments, on the Company’s consolidated statements of stockholders’ equity (deficit) for the periods indicated (in thousands, except share amounts): ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Accumulated ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Additional ​ Other ​ ​ ​ ​ ​ ​ Total ​ ​ ​ ​ Common Stock ​ Paid-in ​ Comprehensive ​ Treasury Stock ​ Accumulated ​ Stockholders’ ​ Restatement ​ Shares Amount Capital Income Shares Amount Deficit Equity (Deficit) References BALANCE - December 31, 2017 (As Previously Reported) 229,073,517 ​ $ 2,291 ​ $ 1,250,899 ​ $ 2,194 587,151 ​ $ (3,102) ​ $ (1,178,636) ​ $ 73,646 ​ ​ Cumulative adjustments — ​ — ​ — ​ — — ​ — ​ (3,417) ​ (3,417) ​ a,b BALANCE - December 31, 2017 (As Restated) ​ 229,073,517 ​ ​ 2,291 ​ ​ 1,250,899 ​ ​ 2,194 ​ 587,151 ​ ​ (3,102) ​ ​ (1,182,053) ​ ​ 70,229 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ BALANCE - December 31, 2018 (As Previously Reported) 234,160,661 ​ $ 2,342 ​ $ 1,289,714 ​ $ 1,584 15,002,663 ​ $ (30,637) ​ $ (1,260,290) ​ $ 2,713 ​ ​ Cumulative adjustments — ​ — ​ (78) ​ — — ​ — ​ (6,223) ​ (6,301) ​ a,b BALANCE - December 31, 2018 (As Restated) ​ 234,160,661 ​ ​ 2,342 ​ ​ 1,289,636 ​ ​ 1,584 ​ 15,002,663 ​ ​ (30,637) ​ ​ (1,266,513) ​ ​ (3,588) ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ BALANCE - December 31, 2019 (As Previously Reported) 318,637,560 ​ $ 3,186 ​ $ 1,507,116 ​ $ 1,400 15,259,045 ​ $ (31,216) ​ $ (1,345,807) ​ $ 134,679 ​ ​ Cumulative adjustments ​ — ​ ​ — ​ ​ (163) ​ ​ (112) ​ — ​ ​ — ​ ​ (4,500) ​ ​ (4,775) ​ a,b BALANCE - December 31, 2019 (As Restated) ​ 318,637,560 ​ $ 3,186 ​ $ 1,506,953 ​ $ 1,288 15,259,045 ​ $ (31,216) ​ $ (1,350,307) ​ $ 129,904 ​ ​ ​ As of December 31, 2019 and 2018 (a) Restatement Items: The correction of material misstatements resulted in a net increase in accumulated deficit of $4.5 million, $6.2 million and $3.4 million as of December 31, 2019, 2018 and 2017, respectively. (b) Other adjustments: Immaterial adjustments resulted in the following: for the period ended December 31, 2019, there was a net increase of $112 thousand for the other comprehensive loss related to the foreign currency translation adjustment and a net decrease of $163 thousand in additional paid-in capital; and for the period ended December 31, 2018, there was a net decrease in additional paid-in capital of $78 thousand. ​ The following tables present the effect of the Restatement Items, as well as other adjustments, on the Company’s consolidated statements of cashflows for the periods indicated (in thousands): ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ For the Year Ended December 31, 2019 ​ ​ ​ As previously ​ Restatement ​ ​ ​ Restatement ​ ​ Reported ​ Adjustments ​ ​ As Restated References Operating Activities ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Net loss attributable to the Company ​ $ (85,465) ​ $ 1,722 ​ $ (83,743) ​ a Adjustments to reconcile net loss to net cash used in operating activities: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Depreciation of long-lived assets ​ ​ 11,989 ​ ​ (51) ​ ​ 11,938 ​ b, d Amortization of intangible assets ​ 698 ​ — ​ ​ 698 ​ ​ Stock-based compensation ​ 10,890 ​ — ​ ​ 10,890 ​ ​ Loss on extinguishment of debt ​ — ​ 518 ​ ​ 518 ​ d Provision for bad debts and other assets ​ 1,981 ​ — ​ ​ 1,981 ​ ​ Amortization of debt issuance costs and discount on convertible senior notes ​ 8,821 ​ 185 ​ ​ 9,006 ​ d Provision for common stock warrants ​ ​ 6,513 ​ — ​ ​ 6,513 ​ ​ Loss on disposal of leased assets ​ ​ 212 ​ ​ — ​ ​ 212 ​ ​ Change in fair value of common stock warrant liability ​ ​ (79) ​ ​ — ​ ​ (79) ​ ​ Benefit on service contracts ​ ​ — ​ ​ (1,643) ​ ​ (1,643) ​ c Changes in operating assets and liabilities that provide (use) cash: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Accounts receivable ​ ​ 10,646 ​ ​ (52) ​ ​ 10,594 ​ d Inventory ​ ​ (24,481) ​ ​ (152) ​ ​ (24,633) ​ d Prepaid expenses, and other assets ​ ​ (8,110) ​ ​ — ​ ​ (8,110) ​ ​ Accounts payable, accrued expenses, and other liabilities ​ 19,879 ​ (2,645) ​ ​ 17,234 ​ b, d Deferred revenue ​ ​ (5,016) ​ ​ 316 ​ ​ (4,700) ​ d Net cash used in operating activities ​ (51,522) ​ (1,802) ​ (53,324) ​ ​ Investing Activities ​ ​ ​ ​ ​ ​ ​ ​ ​ Purchases of property, plant and equipment ​ ​ (5,683) ​ ​ — ​ ​ (5,683) ​ ​ Purchase of intangible assets ​ (2,404) ​ — ​ ​ (2,404) ​ ​ Purchases of equipment related to PPA and equipment related to fuel delivered to customers ​ ​ (6,532) ​ ​ — ​ ​ (6,532) ​ ​ Proceeds from sale of leased assets ​ 375 ​ ​ — ​ ​ 375 ​ ​ Net cash used in investing activities ​ ​ (14,244) ​ — ​ ​ (14,244) ​ ​ Financing Activities ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Proceeds from issuance of preferred stock and warrants, net of transaction costs ​ 14,089 ​ — ​ ​ 14,089 ​ ​ Proceeds from public offerings, net of transaction costs ​ 158,428 ​ (85) ​ ​ 158,343 ​ d Proceeds from exercise of stock options ​ ​ 1,217 ​ ​ — ​ ​ 1,217 ​ ​ Payments for redemption of preferred stock ​ (4,040) ​ — ​ ​ (4,040) ​ ​ Proceeds from issuance of convertible senior notes, net ​ ​ 39,052 ​ ​ — ​ ​ 39,052 ​ ​ Proceeds from borrowing of long-term debt, net of transaction costs ​ ​ 119,186 ​ ​ — ​ ​ 119,186 ​ ​ Principal payments on long-term debt ​ ​ (24,827) ​ ​ (518) ​ ​ (25,345) ​ d Proceeds from finance obligations ​ ​ 83,668 ​ ​ — ​ ​ 83,668 ​ ​ Repayments of finance obligations ​ ​ (61,713) ​ ​ 2,517 ​ ​ (59,196) ​ b Net cash provided by financing activities ​ ​ 325,060 ​ ​ 1,914 ​ ​ 326,974 ​ ​ Effect of exchange rate changes on cash ​ ​ 53 ​ ​ (112) ​ ​ (59) ​ d Increase in cash, cash equivalents and restricted cash ​ ​ 259,347 ​ ​ — ​ ​ 259,347 ​ ​ Cash, cash equivalents, and restricted cash beginning of period ​ ​ 110,153 ​ ​ — ​ ​ 110,153 ​ ​ Cash, cash equivalents, and restricted cash end of period ​ $ 369,500 ​ $ — ​ $ 369,500 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Supplemental disclosure of cash flow information ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Cash paid for interest ​ $ 19,180 ​ $ — ​ ​ 19,180 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Summary of non-cash investing and financing activity ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Recognition of right of use assets ​ $ 127,370 ​ $ (74,446) ​ $ 52,924 ​ b Conversion of preferred stock to common stock ​ ​ 28,392 ​ ​ — ​ ​ 28,392 ​ ​ ​ For the year ended December 31, 2019 (a) Refer to descriptions of the adjustments and their impact on net loss in the Consolidated Statement of Operations sections for the year ended December 31, 2019 above. (b) Right of use asset: The correction of this misstatement resulted in a net decrease to operating cashflows of $2.7 million and a net increase to cash provided by financing activities of $2.5 million for the period ended December 31, 2019. In addition there was a net decrease of $74.4 million to the non-cash investing and financing activity related to the recognition of the right of use asset. (c) Provision for loss contracts related to service: The correction of this misstatement resulted in a net decrease to operating cashflows of $1.6 million for the period ended December 31 2019. (d) Other adjustments: Immaterial adjustments resulted in an net increase to operating cashflows of $906 thousand, a decrease to cash provided by financing activites of $603 thousand and a decrease to effect of exchange rate changes on cash of $112 thousand, for the period ended December 31 2019 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ For the Year Ended December 31, 2018 ​ ​ ​ ​ As previously ​ Restatement ​ ​ ​ Restatement ​ Reported ​ Adjustments ​ ​ As Restated References Operating Activities ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Net loss attributable to the Company ​ $ (78,115) ​ $ (7,493) ​ $ (85,608) ​ a Adjustments to reconcile net loss to net cash used in operating activities: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Depreciation of long-lived assets ​ ​ 11,014 ​ ​ 818 ​ ​ 11,832 ​ b, d Amortization of intangible assets ​ 693 ​ — ​ ​ 693 ​ ​ Stock-based compensation ​ 8,771 ​ — ​ ​ 8,771 ​ ​ Provision for bad debts and other assets ​ 1,626 ​ — ​ ​ 1,626 ​ ​ Amortization of debt issuance costs and discount on convertible senior notes ​ 6,347 ​ — ​ ​ 6,347 ​ ​ Provision for common stock warrants ​ ​ 10,190 ​ — ​ ​ 10,190 ​ ​ Change in fair value of common stock warrant liability ​ (4,286) ​ ​ — ​ ​ (4,286) ​ ​ Income tax benefit ​ ​ (9,217) ​ ​ (78) ​ ​ (9,295) ​ d Loss on service contracts ​ ​ — ​ ​ 5,345 ​ ​ 5,345 ​ c Changes in operating assets and liabilities that provide (use) cash: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Accounts receivable ​ ​ (14,398) ​ ​ (268) ​ ​ (14,666) ​ d Inventory ​ ​ 19,041 ​ ​ 152 ​ ​ 19,193 ​ d Prepaid expenses, and other assets ​ ​ (4,654) ​ ​ — ​ ​ (4,654) ​ ​ Accounts payable, accrued expenses, and other liabilities ​ (10,266) ​ 106 ​ ​ (10,160) ​ d Deferred revenue ​ ​ 5,637 ​ ​ 685 ​ ​ 6,322 ​ d Net cash used in operating activities ​ (57,617) ​ (733) ​ (58,350) ​ ​ Investing Activities ​ ​ ​ ​ ​ ​ ​ ​ ​ Purchases of property, plant and equipment ​ ​ (5,142) ​ ​ — ​ ​ (5,142) ​ ​ Purchases of equipment related to PPA and equipment related to fuel delivered to customers ​ ​ (13,501) ​ ​ — ​ ​ (13,501) ​ ​ Purchase of intangible assets ​ (929) ​ — ​ ​ (929) ​ ​ Net cash used in investing activities ​ ​ (19,572) ​ — ​ ​ (19,572) ​ ​ Financing Activities ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Proceeds from issuance of preferred stock and warrants, net of transaction costs ​ 30,934 ​ — ​ ​ 30,934 ​ ​ Proceeds from public offerings, net of transaction costs ​ 7,195 ​ — ​ ​ 7,195 ​ ​ Proceeds from exercise of stock options ​ ​ 138 ​ ​ — ​ ​ 138 ​ ​ Proceeds from issuance of convertible senior notes, net ​ ​ 95,856 ​ ​ — ​ ​ 95,856 ​ ​ Purchase of capped calls and common stock forward ​ ​ (43,500) ​ ​ — ​ ​ (43,500) ​ ​ Principal payments on long-term debt ​ ​ (16,190) ​ ​ — ​ ​ (16,190) ​ ​ Proceeds from finance obligations ​ ​ 76,175 ​ ​ — ​ ​ 76,175 ​ ​ Repayments of finance obligations ​ ​ (31,264) ​ ​ 733 ​ ​ (30,531) ​ b Net cash provided by financing activities ​ ​ 119,344 ​ ​ 733 ​ ​ 120,077 ​ ​ Effect of exchange rate changes on cash ​ ​ (57) ​ ​ — ​ ​ (57) ​ ​ Increase in cash, cash equivalents and restricted cash ​ ​ 42,098 ​ ​ — ​ ​ 42,098 ​ ​ Cash, cash equivalents, and restricted cash beginning of period ​ ​ 68,055 ​ ​ — ​ ​ 68,055 ​ ​ Cash, cash equivalents, and restricted cash end of period ​ $ 110,153 ​ $ — ​ $ 110,153 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Supplemental disclosure of cash flow information ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Cash paid for interest ​ $ 13,057 ​ $ — ​ ​ 13,057 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Summary of non-cash investing and financing activity ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Recognition of right of use assets ​ $ 79,057 ​ $ (37,378) ​

Unaudited Quarterly Financial d

Unaudited Quarterly Financial data and Restatement of Previously Issued Unaudited Interim Condensed Consolidated Financial Statements	12 Months Ended
	Dec. 31, 2020
Unaudited Quarterly Financial data and Restatement of Previously Issued Unaudited Interim Condensed Consolidated Financial Statements
Unaudited Quarterly Financial data and Restatement of Previously Issued Unaudited Interim Condensed Consolidated Financial Statements	3. Unaudited Quarterly Financial data and Restatement of Previously Issued Unaudited Interim Condensed Consolidated Financial Statements ​ The following tables below include corrections to the prior period results, and include the Restatement Items and other adjustments included in Note 2, “Restatement of Previously Issued Consolidated Financial Statements,” as well as the following: ​ Bonus Accrual ​ Right of Use assets and lease liabilities ​ Loss accrual provision ​ The summary of the quarterly statement of operations are presented as follows: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Quarters ended ​ ​ As Restated ​ ​ ​ ​ ​ March 31, June 30, September 30, December 31, ​ ​ 2020 ​ 2020 ​ 2020 ​ 2020 Net revenue: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Sales of fuel cell systems and related infrastructure ​ $ 20,468 ​ $ 47,746 ​ $ 83,662 ​ $ (246,171) ​ Services performed on fuel cell systems and related infrastructure ​ 6,521 ​ 6,236 ​ 6,829 ​ (29,387) ​ Power Purchase Agreements ​ 6,421 ​ 6,579 ​ 6,629 ​ 6,991 ​ Fuel delivered to customers ​ 7,333 ​ 7,372 ​ 9,831 ​ (40,608) ​ Other ​ ​ 76 ​ ​ 62 ​ ​ 97 ​ ​ 76 ​ Net revenue ​ ​ 40,819 ​ ​ 67,995 ​ ​ 107,048 ​ ​ (309,099) ​ Gross loss ​ (9,703) ​ (15) ​ (28,584) ​ (431,114) ​ Operating expenses ​ ​ 15,883 ​ ​ 26,517 ​ ​ 25,726 ​ ​ 46,660 ​ Operating loss ​ (25,586) ​ (26,532) ​ (54,310) ​ (477,774) ​ Net loss attributable to common stockholders ​ ​ (37,445) ​ ​ (9,414) ​ ​ (65,217) ​ ​ (484,105) ​ Loss per share: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Basic and Diluted ​ $ (0.12) ​ $ (0.03) ​ $ (0.18) ​ $ (1.35) ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Quarters ended ​ ​ As Restated ​ ​ March 31, June 30, September 30, December 31, ​ ​ 2019 ​ 2019 ​ 2019 ​ 2019 Net revenue: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Sales of fuel cell systems and related infrastructure ​ $ 2,550 ​ $ 38,702 ​ $ 38,883 ​ $ 69,785 ​ Services performed on fuel cell systems and related infrastructure ​ 6,343 ​ 5,341 ​ 6,205 ​ 7,328 ​ Power Purchase Agreements ​ 6,035 ​ 6,334 ​ 6,520 ​ 6,664 ​ Fuel delivered to customers ​ 6,582 ​ 7,089 ​ 7,649 ​ 7,779 ​ Other ​ ​ — ​ ​ — ​ ​ 135 ​ ​ 51 ​ Net revenue ​ ​ 21,510 ​ ​ 57,466 ​ ​ 59,392 ​ ​ 91,607 ​ Gross (loss) profit ​ (7,740) ​ 6,142 ​ 4,500 ​ 7,746 ​ Operating expenses ​ ​ 12,227 ​ ​ 17,221 ​ ​ 13,958 ​ ​ 14,855 ​ Operating loss ​ (19,967) ​ (11,079) ​ (9,458) ​ (7,109) ​ Net loss attributable to common stockholders ​ ​ (30,560) ​ ​ (17,351) ​ ​ (18,366) ​ ​ (19,277) ​ Loss per share: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Basic and Diluted ​ $ (0.14) ​ $ (0.08) ​ $ (0.08) ​ $ (0.07) ​ ​ Summary impact of Restatement Items to previously reported unaudited interim condensed consolidated financial information ​ The following tables present the Restatement Items, as well as other adjustments, on the Company’s unaudited interim condensed consolidated balance sheets for the periods indicated (in thousands, except per share): ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ As of September 30, 2020 ​ ​ ​ ​ As previously ​ Restatement ​ ​ ​ ​ Restatement ​ ​ Reported ​ Adjustments ​ As Restated ​ References Assets ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Current assets: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Cash and cash equivalents ​ $ 448,140 ​ $ — ​ $ 448,140 ​ ​ Restricted cash ​ ​ 55,704 ​ ​ — ​ ​ 55,704 ​ ​ Accounts receivable ​ 113,133 ​ 372 ​ 113,505 ​ e Inventory ​ 134,306 ​ (103) ​ 134,203 ​ e Prepaid expenses and other current assets ​ 26,731 ​ — ​ 26,731 ​ ​ Total current assets ​ 778,014 ​ 269 ​ 778,283 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Restricted cash ​ 227,528 ​ — ​ 227,528 ​ ​ Property, plant, and equipment, net ​ ​ 64,820 ​ — ​ 64,820 ​ ​ Right of use assets related to finance leases, net ​ ​ — ​ ​ 2,335 ​ ​ 2,335 ​ a Right of use assets related to operating leases, net ​ ​ — ​ ​ 90,184 ​ ​ 90,184 ​ a, b Equipment related to power purchase agreements and fuel delivered to customers, net ​ ​ 309,475 ​ (237,584) ​ 71,891 ​ a, b Goodwill ​ ​ 71,962 ​ ​ (140) ​ ​ 71,822 ​ e Intangible assets, net ​ 39,169 ​ 400 ​ 39,569 ​ e Other assets ​ 9,661 ​ — ​ 9,661 ​ ​ Total assets ​ $ 1,500,629 ​ $ (144,536) ​ $ 1,356,093 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Liabilities, Redeemable Preferred Stock, and Stockholders’ Equity ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Current liabilities: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Accounts payable ​ $ 58,793 ​ $ — ​ $ 58,793 ​ ​ Accrued expenses ​ 32,031 ​ 5,917 ​ 37,948 ​ d, e Deferred revenue ​ 17,226 ​ — ​ 17,226 ​ ​ Operating lease liabilities ​ ​ — ​ ​ 10,609 ​ ​ 10,609 ​ a, b Finance lease liabilities ​ ​ — ​ ​ 374 ​ ​ 374 ​ a Finance obligations ​ ​ 63,692 ​ ​ (32,343) ​ ​ 31,349 ​ a, b Current portion of long-term debt ​ ​ 74,829 ​ ​ — ​ ​ 74,829 ​ ​ Other current liabilities ​ 17,280 ​ 3,803 ​ 21,083 ​ b, c Total current liabilities ​ 263,851 ​ (11,640) ​ 252,211 ​ ​ Deferred revenue ​ 29,648 ​ (137) ​ 29,511 ​ e Operating lease liabilities ​ ​ — ​ ​ 74,422 ​ ​ 74,422 ​ a, b Finance lease liabilities ​ ​ — ​ ​ 2,384 ​ ​ 2,384 ​ a Finance obligations ​ 337,150 ​ (196,488) ​ 140,662 ​ a, b Convertible senior notes, net ​ ​ 105,088 ​ ​ — ​ ​ 105,088 ​ ​ Long-term debt ​ ​ 120,380 ​ ​ — ​ ​ 120,380 ​ ​ Other liabilities ​ 27,068 ​ 18,102 ​ 45,170 ​ c Total liabilities ​ 883,185 ​ (113,357) ​ 769,828 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Stockholders’ equity: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Common stock, $0.01 par value per share; 750,000,000 shares authorized; Issued: 406,123,816 at September 30, 2020 ​ 4,061 ​ — ​ 4,061 ​ ​ Additional paid-in capital ​ 2,083,199 ​ (30) ​ 2,083,169 ​ e Accumulated other comprehensive income ​ 1,958 ​ (112) ​ 1,846 ​ e Accumulated deficit ​ (1,431,340) ​ (31,037) ​ (1,462,377) ​ ​ Less common stock in treasury ​ ​ (40,434) ​ ​ — ​ ​ (40,434) ​ ​ Total stockholders’ equity ​ 617,444 ​ (31,179) ​ 586,265 ​ ​ Total liabilities, redeemable preferred stock, and stockholders’ equity ​ $ 1,500,629 ​ $ (144,536) ​ $ 1,356,093 ​ ​ ​ As of September 30, 2020 (a) ● $235.8 million was reclassified from equipment related to power purchase agreements and fuel delivered to customers, net to the right of use assets related to operating leases, net: ● $2.3 million was reclassified from equipment related to power purchase agreements and fuel delivered to customers, net to the right of use asset related to finance leases, net; ● $32.7 million was reclassified from current finance obligations to current operating lease liabilities; ● $195.1 million was reclassified from non-current finance obligations to non-current operating lease liabilities; ● $374 thousand was reclassified from current finance obligations to current finance lease liabilities; and ● $2.4 million was reclassified from non-current finance obligations to non-current finance lease liabilities. (b) The correction of the misstatement associated with the right of use assets relating to operating leases resulted in the following at September 30, 2020: ● the right of use assets related to operating leases, net had a decrease of $145.6 million; ● equipment related to power purchase agreements and fuel delivered to customers, net had an increase of $535 thousand; ● current operating lease liabilities had a decrease of $22.1 million; ● non-current operating lease liabilities had a decrease of $120.6 million; ● the current and non current finance obligations had an increase of $788 thousand and $1.0 million, respectively; and ● other current liabilities had a decrease of $2.6 million (c) Loss accrual provision: The correction of this misstatement resulted in an increase of $6.4 million to other current liabilities and an increase of $18.1 million to other long-term liabilities at September 30, 2020. ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ As of June 30, 2020 ​ ​ ​ ​ As previously ​ Restatement ​ ​ ​ ​ Restatement ​ ​ Reported ​ Adjustments ​ As Restated ​ References Assets ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Current assets: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Cash and cash equivalents ​ $ 152,492 ​ $ — ​ $ 152,492 ​ ​ Restricted cash ​ ​ 50,634 ​ ​ — ​ ​ 50,634 ​ ​ Accounts receivable ​ 45,522 ​ 260 ​ 45,782 ​ d Inventory ​ 114,571 ​ — ​ 114,571 ​ ​ Prepaid expenses and other current assets ​ 31,436 ​ — ​ 31,436 ​ ​ Total current assets ​ 394,655 ​ 260 ​ 394,915 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Restricted cash ​ 180,127 ​ — ​ 180,127 ​ ​ Property, plant, and equipment, net ​ ​ 60,018 ​ — ​ 60,018 ​ ​ Right of use assets related to finance leases, net ​ ​ — ​ ​ 2,389 ​ ​ 2,389 ​ a Right of use assets related to operating leases, net ​ ​ — ​ ​ 71,789 ​ ​ 71,789 ​ a, b Equipment related to power purchase agreements and fuel delivered to customers, net ​ ​ 274,721 ​ (206,293) ​ 68,428 ​ a, b Goodwill ​ ​ 70,402 ​ ​ (140) ​ ​ 70,262 ​ d Intangible assets, net ​ 38,574 ​ 400 ​ 38,974 ​ d Other assets ​ 11,817 ​ — ​ 11,817 ​ ​ Total assets ​ $ 1,030,314 ​ $ (131,595) ​ $ 898,719 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Liabilities, Redeemable Preferred Stock, and Stockholders’ Equity ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Current liabilities: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Accounts payable ​ $ 39,812 ​ $ — ​ $ 39,812 ​ ​ Accrued expenses ​ 23,320 ​ 597 ​ 23,917 ​ d Deferred revenue ​ 14,902 ​ — ​ 14,902 ​ ​ Operating lease liabilities ​ ​ — ​ ​ 9,453 ​ ​ 9,453 ​ a, b Finance lease liabilities ​ ​ — ​ ​ 345 ​ ​ 345 ​ a Finance obligations ​ ​ 57,695 ​ ​ (28,901) ​ ​ 28,794 ​ a, b Current portion of long-term debt ​ ​ 50,933 ​ ​ — ​ ​ 50,933 ​ ​ Other current liabilities ​ 21,692 ​ (2,274) ​ 19,418 ​ b, c Total current liabilities ​ 208,354 ​ (20,780) ​ 187,574 ​ ​ Deferred revenue ​ 25,038 ​ (190) ​ 24,848 ​ d Operating lease liabilities ​ ​ — ​ ​ 58,410 ​ ​ 58,410 ​ a, b Finance lease liabilities ​ ​ — ​ ​ 2,465 ​ ​ 2,465 ​ a Finance obligations ​ 300,653 ​ (169,000) ​ 131,653 ​ a, b Convertible senior notes, net ​ ​ 142,704 ​ ​ 185 ​ ​ 142,889 ​ d Long-term debt ​ ​ 101,844 ​ ​ — ​ ​ 101,844 ​ ​ Other liabilities ​ 11,756 ​ 2,720 ​ 14,476 ​ c Total liabilities ​ 790,349 ​ (126,190) ​ 664,159 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Stockholders’ equity: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Common stock, $0.01 par value per share; 750,000,000 shares authorized; Issued: 348,201,792 at June 30, 2020 ​ 3,482 ​ — ​ 3,482 ​ ​ Additional paid-in capital ​ 1,658,532 ​ (94) ​ 1,658,438 ​ d Accumulated other comprehensive income ​ 1,271 ​ (112) ​ 1,159 ​ d Accumulated deficit ​ (1,391,961) ​ (5,199) ​ (1,397,160) ​ ​ Less common stock in treasury ​ ​ (31,359) ​ ​ — ​ ​ (31,359) ​ ​ Total stockholders’ equity ​ 239,965 ​ (5,405) ​ 234,560 ​ ​ Total liabilities, redeemable preferred stock, and stockholders’ equity ​ $ 1,030,314 ​ $ (131,595) ​ $ 898,719 ​ ​ ​ As of June 30, 2020 (a) The "as previously reported" balances for equipment related to power purchase agreements and fuel delivered to customers, net (previously captioned leased assets, net) and the current and long-term finance obligations have been reclassified to conform to current period presentations, as follows at June 30, 2020: ● $204.7 million was reclassified from equipment related to power purchase agreements and fuel delivered to customers, net to right of use assets related to operating leases, net; ● $2.4 million was reclassified from equipment related to power purchase agreements and fuel delivered to customers, net to right of use asset related to finance leases, net; ● $29.5 million was reclassified from current finance obligations to current operating lease liabilities; ● $169.0 million was reclassified from non-current finance obligations to non-current operating lease liabilities; ● $345 thousand was reclassified from current finance obligations to current finance lease liabilities; and ● $2.4 million was reclassified from non-current finance obligations to non-current finance lease liabilities. ● the right of use assets related to operating leases, net had a decrease of $132.9 million; ● equipment related to power purchase agreements and fuel delivered to customers, net had an increase of $837 thousand; ● current operating lease liabilities had a decrease of $20.1 million; ● non-current operating lease liabilities had a decrease of $110.6 million; ● the current and non current finance obligations had an increase of $898 thousand and $2.4 million, respectively; and ● other current liabilities had a decrease of $3.5 million. (c) Loss accrual provision: The correction of this misstatement resulted in a net increase of $1.3 million to other current liabilities and a net increase of $2.7 million to other long-term liabilities at June 30, 2020. ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ As of March 31, 2020 ​ ​ ​ ​ As previously ​ Restatement ​ ​ ​ ​ Restatement ​ ​ Reported ​ Adjustments ​ As Restated ​ References Assets ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Current assets: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Cash and cash equivalents ​ $ 74,340 ​ $ — ​ $ 74,340 ​ ​ Restricted cash ​ ​ 56,804 ​ ​ — ​ ​ 56,804 ​ ​ Accounts receivable ​ 24,437 ​ 297 ​ 24,734 ​ d Inventory ​ 92,972 ​ — ​ 92,972 ​ ​ Prepaid expenses and other current assets ​ 28,500 ​ — ​ 28,500 ​ ​ Total current assets ​ 277,053 ​ 297 ​ 277,350 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Restricted cash ​ 176,070 ​ — ​ 176,070 ​ ​ Property, plant, and equipment, net ​ ​ 16,591 ​ — ​ 16,591 ​ ​ Right of use assets related to finance leases, net ​ ​ — ​ ​ 1,707 ​ ​ 1,707 ​ a Right of use assets related to operating leases, net ​ ​ — ​ ​ 64,812 ​ ​ 64,812 ​ a, b Equipment related to power purchase agreements and fuel delivered to customers, net ​ ​ 252,802 ​ (184,400) ​ 68,402 ​ a, b Goodwill ​ ​ 8,673 ​ ​ — ​ ​ 8,673 ​ ​ Intangible assets, net ​ 5,296 ​ 400 ​ 5,696 ​ d Other assets ​ 12,059 ​ — ​ 12,059 ​ ​ Total assets ​ $ 748,544 ​ $ (117,184) ​ $ 631,360 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Liabilities, Redeemable Preferred Stock, and Stockholders’ Equity ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Current liabilities: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Accounts payable ​ $ 35,503 ​ $ — ​ $ 35,503 ​ ​ Accrued expenses ​ 14,273 ​ 597 ​ 14,870 ​ d Deferred revenue ​ 11,557 ​ — ​ 11,557 ​ ​ Operating lease liabilities ​ ​ — ​ ​ 8,959 ​ ​ 8,959 ​ a, b Finance lease liabilities ​ ​ — ​ ​ 204 ​ ​ 204 ​ a Finance obligations ​ ​ 52,047 ​ ​ (25,838) ​ ​ 26,209 ​ a, b Current portion of long-term debt ​ ​ 27,819 ​ ​ — ​ ​ 27,819 ​ ​ Other current liabilities ​ 10,423 ​ (1,977) ​ 8,446 ​ b, c Total current liabilities ​ 151,622 ​ (18,055) ​ 133,567 ​ ​ Deferred revenue ​ 22,912 ​ (228) ​ 22,684 ​ d Operating lease liabilities ​ ​ — ​ ​ 52,165 ​ ​ 52,165 ​ a, b Finance lease liabilities ​ ​ — ​ ​ 1,953 ​ ​ 1,953 ​ a Finance obligations ​ 272,171 ​ (150,849) ​ 121,322 ​ a, b Convertible senior notes, net ​ ​ 112,878 ​ ​ 185 ​ ​ 113,063 ​ d Long-term debt ​ ​ 79,119 ​ ​ — ​ ​ 79,119 ​ ​ Other liabilities ​ 13 ​ 2,373 ​ 2,386 ​ c Total liabilities ​ 638,715 ​ (112,456) ​ 526,259 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Redeemable preferred stock: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Redeemable preferred stock: Series C redeemable convertible preferred stock, $0.01 par value per share (aggregate involuntary liquidation $16,664 ); 10,431 shares authorized; Issued and outstanding : 2,620 at March 31, 2020 ​ ​ 709 ​ ​ — ​ ​ 709 ​ ​ Stockholders’ equity: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Common stock, $0.01 par value per share; 750,000,000 shares authorized; Issued: 322,220,469 at March 31, 2020 ​ 3,222 ​ — ​ 3,222 ​ ​ Additional paid-in capital ​ 1,519,257 ​ (163) ​ 1,519,094 ​ d Accumulated other comprehensive income ​ 1,164 ​ (112) ​ 1,052 ​ d Accumulated deficit ​ (1,383,299) ​ (4,453) ​ (1,387,752) ​ ​ Less common stock in treasury ​ ​ (31,224) ​ ​ — ​ ​ (31,224) ​ ​ Total stockholders’ equity ​ 109,120 ​ (4,728) ​ 104,392 ​ ​ Total liabilities, redeemable preferred stock, and stockholders’ equity ​ $ 748,544 ​ $ (117,184) ​ $ 631,360 ​ ​ ​ As of March 31, 2020 (a) The "as previously reported" balances for equipment related to power purchase agreements and fuel delivered to customers, net (previously captioned leased assets, net) and the current and long-term finance obligations have been reclassified to conform to current period presentations, as follows at March 31, 2020: ● $183.4 million was reclassified from equipment related to power purchase agreements and fuel delivered to customers, net to right of use assets related to operating leases, net; ● $1.7 million was reclassified from equipment related to power purchase agreements and fuel delivered to customers, net to right of use asset related to finance leases, net; ● $26.6 million was reclassified from current finance obligations to current operating lease liabilities; ● $151.0 million was reclassified from non-current finance obligations to non-current operating lease liabilities; ● $204 thousand was reclassified from current finance obligations to current finance lease liabilities; and ● $1.9 million was reclassified from non-current finance obligations to non-current finance lease liabilities. (b) The correction of the misstatement associated with the right of use assets relating to operating leases resulted in the following at March 31, 2020: ● the right of use assets related to operating leases, net had a decrease of $118.6 million; ● equipment related to power purchase agreements and fuel delivered to customers, net had an increase of $725 thousand; ● current operating lease liabilities had a decrease of $17.7 million; ● non-current operating lease liabilities had a decrease of $99.0 million; ● the current finance obligations and non-current finance obligations had an increase of $1.0 million and $2.0 million, respectively; and ● other current liabilities had a decrease of $3.2 million. (c) Loss accrual provision: The correction of this misstatement resulted in an increase of $1.2 million to other current liabilities and an increase of $2.4 million to other long-term liabilities at March 31, 2020. ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ As of September 30, 2019 ​ ​ ​ ​ As previously ​ Restatement ​ ​ ​ ​ Restatement ​ ​ Reported ​ Adjustments ​ As Restated ​ References Assets ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Current assets: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Cash and cash equivalents ​ $ 43,275 ​ $ — ​ $ 43,275 ​ ​ Restricted cash ​ ​ 35,720 ​ ​ — ​ ​ 35,720 ​ ​ Accounts receivable ​ 24,392 ​ 345 ​ 24,737 ​ d Inventory ​ 80,601 ​ — ​ 80,601 ​ ​ Prepaid expenses and other current assets ​ 12,804 ​ — ​ 12,804 ​ ​ Total current assets ​ 196,792 ​ 345 ​ 197,137 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Restricted cash ​ 119,322 ​ — ​ 119,322 ​ ​ Property, plant, and equipment, net ​ ​ 14,990 ​ — ​ 14,990 ​ ​ Right of use assets related to finance leases, net ​ ​ — ​ ​ 1,720 ​ ​ 1,720 ​ a Right of use assets related to operating leases, net ​ ​ — ​ ​ 47,016 ​ ​ 47,016 ​ a, b Equipment related to power purchase agreements and fuel delivered to customers, net ​ ​ 202,034 ​ (134,786) ​ 67,248 ​ a, b Goodwill ​ ​ 8,606 ​ ​ — ​ ​ 8,606 ​ ​ Intangible assets, net ​ 5,113 ​ — ​ 5,113 ​ ​ Other assets ​ 9,152 ​ — ​ 9,152 ​ ​ Total assets ​ $ 556,009 ​ $ (85,705) ​ $ 470,304 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Liabilities, Redeemable Preferred Stock, and Stockholders’ Deficit ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Current liabilities: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Accounts payable ​ $ 36,851 ​ $ — ​ $ 36,851 ​ ​ Accrued expenses ​ 9,457 ​ — ​ 9,457 ​ ​ Deferred revenue ​ 11,480 ​ — ​ 11,480 ​ ​ Operating lease liabilities ​ ​ — ​ ​ 8,666 ​ ​ 8,666 ​ a, b Finance lease liabilities ​ ​ — ​ ​ 310 ​ ​ 310 ​ a Finance obligations ​ ​ 41,112 ​ ​ (20,643) ​ ​ 20,469 ​ a, b Current portion of long-term debt ​ ​ 17,202 ​ ​ — ​ ​ 17,202 ​ ​ Other current liabilities ​ 10,238 ​ (1,865) ​ 8,373 ​ b, c Total current liabilities ​ 126,340 ​ (13,532) ​ 112,808 ​ ​ Deferred revenue ​ 22,444 ​ (231) ​ 22,213 ​ d Operating lease liabilities ​ ​ — ​ ​ 36,599 ​ ​ 36,599 ​ a, b Finance lease liabilities ​ ​ — ​ ​ 2,068 ​ ​ 2,068 ​ a Finance obligations ​ 208,465 ​ (108,796) ​ 99,669 ​ a, b Common stock warrant liability ​ ​ 98 ​ ​ — ​ ​ 98 ​ ​ Convertible senior notes, net ​ ​ 107,760 ​ ​ 185 ​ ​ 107,945 ​ d Long-term debt ​ ​ 78,840 ​ ​ — ​ ​ 78,840 ​ ​ Other liabilities ​ 13 ​ 2,821 ​ 2,834 ​ c Total liabilities ​ 543,960 ​ (80,886) ​ 463,074 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Redeemable preferred stock, $.01 par value ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Series C redeemable convertible preferred stock, $0.01 par value per share 10,431 shares authorized; Issued outstanding : 2,620 at September 30, 2019 ​ ​ 709 ​ ​ — ​ ​ 709 ​ ​ Series E redeemable convertible preferred stock, $0.01 par value per share; Shares authorized: 35,000 at outstanding : 28,269 at September 30, 2019 ​ ​ 25,746 ​ ​ — ​ ​ 25,746 ​ ​ Stockholders’ deficit: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Common stock, $0.01 par value per share; 750,000,000 shares authorized; Issued: 253,982,578 at September 30, 2019 ​ 2,540 ​ — ​ 2,540 ​ ​ Additional paid-in capital (1) ​ 1,340,859 ​ (78) ​ 1,340,781 ​ d Accumulated other comprehensive income ​ 929 ​ — ​ 929 ​ ​ Accumulated deficit (1) ​ (1,327,518) ​ (4,741) ​ (1,332,259) ​ ​ Less common stock in treasury ​ ​ (31,216) ​ ​ — ​ ​ (31,216) ​ ​ Total stockholders’ deficit ​ (14,406) ​ (4,819) ​ (19,225) ​ ​ Total liabilities, redeemable preferred stock, and stockholders’ deficit ​ $ 556,009 ​ $ (85,705) ​ $ 470,304 ​ ​ ​ (1) The "as previously reported" balances include a decrease in additional paid-in capital of $6.5 million and an increase of $6.5 million to accumulated deficit due to the impact of the adoption of ASU 2019-08 of January 1, 2019. ​ As of September 30, 2019 (a) The "as previously reported" balances for equipment related to power purchase agreements and fuel delivered to customers, net (previously captioned leased assets, net) and the current and long-term finance obligations have been reclassified to conform to current period presentations, as follows at September 30, 2019: ● $133.7 million was reclassified from equipment related to power purchase agreements and fuel delivered to customers, net to right of use assets related to operating leases, net; ● $1.7 million was reclassified from equipment related to power purchase agreements and fuel delivered to customers, net to right of use asset related to finance leases, net; ● $21.1 million was reclassified from current finance obligations to current operating lease liabilities; ● $109.3 million was reclassified from non-current finance obligations to non-current operating lease liabilities; ● $310 thousand was reclassified from current finance obligations to current finance lease liabilities; and ● $2.1 million was reclassified from non-current finance obligations to non-current finance lease liabilities. (b) The correction of the misstatement associated with the right of use assets relating to operating leases resulted in the following at September 30, 2019: ● the right of use assets related to operating leases, net had a decrease of $86.7 million; ● equipment related to power purchase agreements and fuel delivered to customers, net had an increase of $655 thousand; ● current operating lease liabilities had a decrease of $12.4 million; ● non-current operating lease liabilities had a decrease of $72.7 million; ● the current and non-current finance obligations had a increase of $752 thousand and an increase $2.6 million; and ● other current liabilities had a decrease of $3.0 million. (c) Loss accrual provision: The correction of this misstatement resulted in a net increase of $1.2 million to other current liabilities and a net increase of $2.8 million to other long-term liabilities at September 30, 2019. (d) Other adjustments: Immaterial adjustments at September 30, 2019 resulted in the following: Adjustments related to increases in accounts receivable of $345 thousand, decrease in deferred revenue of $231 thousand, increase in convertible senior notes of $185 thousand and decrease in additional paid in capital of $78 thousand. ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ As of June 30, 2019 ​ ​ ​ ​ As previously ​ Restatement ​ ​ ​ ​ Restatement ​ ​ Reported ​ Adjustments ​ As Restated ​ References Assets ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Current assets: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Cash and cash equivalents ​ $ 19,845 ​ $ — ​ $ 19,845 ​ ​ Restricted cash ​ ​ 19,400 ​ ​ — ​ ​ 19,400 ​ ​ Accounts receivable ​ 26,592 ​ 252 ​ 26,844 ​ d Inventory ​ 73,190 ​ — ​ 73,190 ​ ​ Prepaid expenses and other current assets ​ 14,001 ​ — ​ 14,001 ​ ​ Total current assets ​ 153,028 ​ 252 ​ 153,280 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Restricted cash ​ 96,082 ​ — ​ 96,082 ​ ​ Property, plant, and equipment, net ​ ​ 14,228 ​ — ​ 14,228 ​ ​ Right of use assets related to finance leases, net ​ ​ — ​ ​ 1,726 ​ ​ 1,726 ​ a Right of use assets related to operating leases, net ​ ​ — ​ ​ 39,679 ​ ​ 39,679 ​ a, b Equipment related to power purchase agreements and fuel delivered to customers, net ​ ​ 170,455 ​ (101,473) ​ 68,982 ​ a, b Goodwill ​ ​ 8,961 ​ ​ — ​ ​ 8,961 ​ ​ Intangible assets, net ​ 5,398 ​ — ​ 5,398 ​ ​ Other assets ​ 8,842 ​ — ​ 8,842 ​ ​ Total assets ​ $ 456,994 ​ $ (59,816) ​ $ 397,178 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Liabilities, Redeemable Preferred Stock, and Stockholders’ Deficit ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Current liabilities: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Accounts payable ​ $ 36,946 ​ $ — ​ $ 36,946 ​ ​ Accrued expenses ​ 4,522 ​ — ​ 4,522 ​ ​ Deferred revenue ​ 11,730 ​ — ​ 11,730 ​ ​ Operating lease liabilities ​ ​ — ​ ​ 7,512 ​ ​ 7,512 ​ a, b Finance lease liabilities ​ ​ — ​ ​ 266 ​ ​ 266 ​ a Finance obligations ​ ​ 30,663 ​ ​ (18,208) ​ ​ 12,455 ​ a, b Current portion of long-term debt ​ ​ 15,928 ​ ​ — ​ ​ 15,928 ​ ​ Other current liabilities ​ 3,017 ​ 688 ​ 3,705 ​ b, c Total current liabilities ​ 102,806 ​ (9,742) ​ 93,064 ​ ​ Deferred revenue ​ 24,519 ​ (393) ​ 24,126 ​ d Common stock warrant liability ​ ​ 525 ​ ​ — ​ ​ 525 ​ ​ Operating lease liabilities ​ ​ — ​ ​ 30,631 ​ ​ 30,631 ​ a, b Finance lease liabilities ​ ​ — ​ ​ 2,123 ​ ​ 2,123 ​ a Finance obligations ​ 157,531 ​ (80,615) ​ 76,916 ​ a, b Convertible senior notes, net ​ ​ 66,844 ​ ​ — ​ ​ 66,844 ​ ​ Long-term debt ​ ​ 83,776 ​ ​ — ​ ​ 83,776 ​ ​ Other liabilities ​ 13 ​ 3,320 ​ 3,333 ​ c Total liabilities ​ 436,014 ​ (54,676) ​ 381,338 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Redeemable preferred stock: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Series C redeemable convertible preferred stock, $0.01 par value per share (aggregate involuntary liquidation $16,664 ); 10,431 shares authorized; Issued and outstanding : 2,620 at both June 30, 2019 ​ ​ 709 ​ ​ — ​ ​ 709 ​ ​ Series E redeemable convertible preferred stock, $0.01 par value per share (aggregate involuntary liquidation $35,000 at June 30, 2019); Shares authorized: 35,000 at June 30, outstanding : 35,000 at June 30, 2019 ​ ​ 30,926 ​ ​ — ​ ​ 30,926 ​ ​ Stockholders’ deficit: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Common stock, $0.01 par value per share; 750,000,000 shares authorized; Issued: 246,975,173 at June 30, 2019 ​ 2,470 ​ — ​ 2,470 ​ ​ Additional paid-in capital (1) ​ 1,325,459 ​ (78) ​ 1,325,381 ​ d Accumulated other comprehensive income ​ 1,460 ​ — ​ 1,460 ​ ​ Accumulated deficit (1) ​ (1,309,363) ​ (5,062) ​ (1,314,425) ​ ​ Less common stock in treasury ​ ​ (30,681) ​ ​ — ​ ​ (30,681) ​ ​ Total stockholders’ deficit ​ (10,655) ​ (5,140) ​ (15,795) ​ ​ Total liabilities, redeemable preferred stock, and stockholders’ deficit ​ $ 456,994 ​ $ (59,816) ​ $ 397,178 ​ ​ ​ (1) The "as previously reported" balances include a decrease in additional paid-in capital of $3.5 million and an increase of $3.5 million to accumulated deficit due to the impact of the adoption of ASU 2019-08 of January 1, 2019. ​ As of June 30, 2019 ● $100.3 million was reclassified from equipment related to power purchase agreements and fuel delivered to customers, net to right of use assets related to operating leases, net; ● $1.7 million was reclassified from equipment related to power purchase agreements and fuel delivered to customers, net to right of use asset related to finance leases, net; ● $16.6 million was reclassified from current finance obligations to current operating lease liabilities; ● $80.6 million was reclassified from non-current finance obligations to non-current operating lease liabilities; ● $266 thousand was reclassified from current finance obligations to current finance lease liabilities; and ● $2.1 million was reclassified from non-current finance obligations to non-current finance lease liabilities. ● the right of use assets related to operating leases, net had a decrease of $60.6 million; ● equipment related to power purchase agreements and fuel delivered to customers, net had an increase of $543 thousand; ● current operating lease liabilities had a decrease of $9.1 million; ● non-current operating lease liabilities had a decrease of $50.0 million; ● the current and non-current finance obligations had a decrease of $1.4 million and an increase of $2.2 million; and ● other current liabilities had a decrease of $464 thousand. (c) Loss accrual provision: The correction of this misstatement resulted in a net increase of $1.2 million to other current liabilities and a net increase of $3.3 million to other long-term liabilities at June 30, 2019. ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ As of March 31, 2019 ​ ​ ​ ​ As previously ​ Restatement ​ ​ ​ ​ Restatement ​ ​ Reported ​ Adjustments ​ As Restated ​ References Assets ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Current assets: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Cash and cash equivalents ​ $ 39,336 ​ $ — ​ $ 39,336 ​ ​ Restricted cash ​ ​ 19,297 ​ ​ — ​ ​ 19,297 ​ ​ Accounts receivable ​ 32,062 ​ 245 ​ 32,307 ​ d Inventory ​ 65,474 ​ — ​ 65,474 ​ ​ Prepaid expenses and other current assets ​ 10,296 ​ — ​ 10,296 ​ ​ Total current assets ​ 166,465 ​ 245 ​ 166,710 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Restricted cash ​ 50,598 ​ — ​ 50,598 ​ ​ Property, plant, and equipment, net ​ ​ 13,615 ​ — ​ 13,615 ​ ​ Right of use assets related to finance leases, net ​ ​ — ​ ​ 1,733 ​ ​ 1,733 ​ a Right of use assets related to operating leases, net ​ ​ — ​ ​ 33,599 ​ ​ 33,599 ​ a, b Equipment related to power purchase agreements and fuel delivered to customers, net ​ ​ 141,889 ​ (70,961) ​ 70,928 ​ a, b Goodwill ​ ​ 8,886 ​ ​ — ​ ​ 8,886 ​ ​ Intangible assets, net ​ 3,677 ​ — ​ 3,677 ​ ​ Other assets ​ 11,069 ​ — ​ 11,069 ​ ​ Total assets ​ $ 396,199 ​ $ (35,384) ​ $ 360,815 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Liabilities, Redeemable Preferred Stock, and Stockholders’ Deficit ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Current liabilities: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Accounts payable ​ $ 31,688 ​ $ — ​ $ 31,688 ​ ​ Accrued expenses ​ 6,509 ​ — ​ 6,509 ​ ​ Deferred revenue ​ 11,736 ​ — ​ 11,736 ​ ​ Operating lease liabilities ​ ​ — ​ ​ 7,042 ​ ​ 7,042 ​ a, b Finance lease liabilities ​ ​ — ​ ​ 236 ​ ​ 236 ​ a Finance obligations ​ ​ 23,997 ​ ​ (12,969) ​ ​ 11,028 ​ a, b Current portion of long-term debt ​ ​ 12,559 ​ ​ — ​ ​ 12,559 ​ ​ Other current liabilities ​ 2,271 ​ 1,474 ​ 3,745 ​ c Total current liabilities ​ 88,760 ​ (4,217) ​ 84,543 ​ ​ Deferred revenue ​ 25,835 ​ (469) ​ 25,366 ​ d Operating lease liabilities ​ ​ — ​ ​ 25,657 ​ ​ 25,657 ​ a, b Finance lease liabilities ​ ​ — ​ ​ 2,142 ​ ​ 2,142 ​ a Finance obligations ​ 111,195 ​ (56,331) ​ 54,864 ​ a, b Common stock warrant liability ​ ​ 2,231 ​ ​ — ​ ​ 2,231 ​ ​ Convertible senior notes, net ​ ​ 65,025 ​ ​ — ​ ​ 65,025 ​ ​ Long-term debt ​ ​ 72,676 ​ ​ — ​ ​ 72,676 ​ ​ Other liabilities ​ 17 ​ 3,729 ​ 3,746 ​ c Total liabilities ​ 365,739 ​ (29,489) ​ 336,250 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Redeemable preferred stock: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Series C redeemable convertible preferred stock, $0.01 par value per share (aggregate involuntary liquidation preference $16,664 ); 10,431 shares authorized; Issued and outstanding : 2,620 at March 31, 2019 ​ ​ 709 ​ ​ — ​ ​ 709 ​ ​ Series E redeemable convertible preferred stock, $0.01 par value per share (aggregate involuntary liquidation ​ ​ 30,931 ​ ​ — ​ ​ 30,931 ​ ​ Stockholders’ deficit: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Common stock, $0.01 par value per share; 750,000,000 shares authorized; Issued: ​ 2,445 ​ — ​ 2,445 ​ ​ Additional paid-in capital (1) ​ 1,316,893 ​ (78) ​ 1,316,815 ​ d Accumulated other comprehensive income ​ 1,374 ​ — ​ 1,374 ​ ​ Accumulated deficit (1) ​ (1,291,255) ​ (5,817) ​ (1,297,072) ​ ​ Less common stock in treasury ​ ​ (30,637) ​ ​ — ​ ​ (30,637) ​ ​ Total stockholders’ deficit ​ (1,180) ​ (5,895) ​ (7,075) ​ ​ Total liabilities, redeemable preferred stock, and stockholders’ deficit ​ $ 396,199 ​ $ (35,384) ​ $ 360,815 ​ ​ ​ (1) The "as previously reported" balances include a decrease in additional paid-in capital of $3 .0 million and an increase of $3.0 million to accumulated deficit due to the impact of the adoption of ASU 2019-08 of January 1, 2019. ​ As of March 31, 2019 (a) The "as previously reported" balances for equipment related to power purchase agreements and fuel delivered to customers, net (previously captioned leased assets, net) and the current and long-term finance obligations have been reclassified to conform to current period presentations, as follows at March 31, 2019: ● $69.7 million was reclassified from equipment related to power purchase agreements and fuel delivered to customers, net to right

Summary of Significant Accounti

Summary of Significant Accounting Policies	12 Months Ended
	Dec. 31, 2020
Summary of Significant Accounting Policies
Summary of Significant Accounting Policies	4. Summary of Significant Accounting Policies ​ Principles of Consolidation ​ The consolidated financial statements include the financial statements of the Company and its wholly-owned subsidiaries. All significant intercompany balances and transactions have been eliminated in consolidation. ​ Leases ​ Leases ​ The Company determines if an arrangement is or contains a lease at contract inception. The Company recognizes a right of use asset and a lease liability at the lease commencement date. For operating leases, the lease liability is initially measured at the present value of the unpaid lease payments at the lease commencement date. For finance leases, the lease liability is initially measured in the same manner and date as for operating leases and is subsequently measured at amortized cost using the effective interest method. ​ Key estimates and judgments include how the Company determines (1) the discount rate it uses to discount the unpaid lease payments to present value, (2) the lease term and (3) the lease payments. ​ ● ASC Topic 842 requires a lessee to discount its unpaid lease payments using the interest rate implicit in the lease or, if that rate cannot be readily determined, its incremental borrowing rate. Generally, the Company cannot determine the interest rate implicit in the lease because it does not have access to the lessor’s estimated residual value or the amount of the lessor’s deferred initial direct costs. Therefore, the Company generally uses its incremental borrowing rate as the discount rate for the lease. The Company’s incremental borrowing rate for a lease is the rate of interest it would have to pay on a collateralized basis to borrow an amount equal to the lease payments under similar terms. Adjustments that considered the Company’s actual borrowing rate, inclusive of securitization, as well as borrowing rates for companies of similar credit quality, were applied in the determination of the incremental borrowing rate. ​ ● The lease term for all of the Company’s leases includes the noncancelable period of the lease, plus any additional periods covered by either a Company option to extend (or not to terminate) the lease that the Company is reasonably certain to exercise, or an option to extend (or not to terminate) the lease controlled by the lessor. ​ ● Lease payments included in the measurement of the lease liability comprise fixed payments, and for certain finance leases, the exercise price of a Company option to purchase the underlying asset if the Company is reasonably certain at lease commencement to exercise the option. ​ The right of use asset is initially measured at cost, which comprises the initial amount of the lease liability adjusted for lease payments made at or before the lease commencement date, plus any initial direct costs incurred less any lease incentives received. For operating leases, the right of use asset is subsequently measured throughout the lease term at the carrying amount of the lease liability, plus initial direct costs, plus (minus) any prepaid (accrued) lease payments, less the unamortized balance of lease incentives received. Lease expense for lease payments is recognized on a straight-line basis over the lease term. ​ For finance leases, the right of use asset is subsequently amortized using the straight-line method from the lease commencement date to the earlier of the end of the useful life of the underlying asset or the end of the lease term unless the lease transfers ownership of the underlying asset to the Company or the Company is reasonably certain to exercise an option to purchase the underlying asset. In those cases, the right of use asset is amortized over the useful life of the underlying asset. Amortization of the right of use asset is recognized and presented separately from interest expense on the lease liability. The Company’s leases do not contain variable lease payments. ​ Right of use assets for operating and finance leases are periodically reviewed for impairment losses. The Company uses the long-lived assets impairment guidance in ASC Subtopic 360-10, Property, Plant, and Equipment – Overall ​ The Company monitors for events or changes in circumstances that require a reassessment of its leases. When a reassessment results in the remeasurement of a lease liability, a corresponding adjustment is made to the carrying amount of the corresponding right of use asset. ​ Operating and finance lease right of use assets are presented separately on the Company’s consolidated balance sheets. The current portions of operating and finance lease liabilities are also presented separately within current liabilities and the long-term portions are presented separately within noncurrent liabilities on the consolidated balance sheets. ​ The Company has elected not to recognize right of use assets and lease liabilities for short-term leases that have a lease term of 12 months or less. The Company recognizes the lease payments associated with its short-term leases as an expense on a straight-line basis over the lease term. ​ Revenue Recognition ​ The Company enters into contracts that may contain one or a combination of fuel cell systems and infrastructure, installation, maintenance, spare parts, fuel delivery and other support services. Contracts containing fuel cell systems and related infrastructure may be sold directly to customers or provided to customers under a PPA, discussed further below. ​ The Company does not include a right of return on its products other than rights related to standard warranty provisions that permit repair or replacement of defective goods. The Company accrues for anticipated standard warranty costs at the same time that revenue is recognized for the related product, or when circumstances indicate that warranty costs will be incurred, as applicable. Any prepaid amounts would only be refunded to the extent services have not been provided or the fuel cell systems or infrastructure have not been delivered . Revenue is measured based on the transaction price specified in a contract with a customer, subject to the allocation of the transaction price to distinct performance obligations as discussed below. The Company recognizes revenue when it satisfies a performance obligation by transferring a product or service to a customer. ​ Promises to the customer are separated into performance obligations, and are accounted for separately if they are (1) capable of being distinct and (2) distinct in the context of the contract. The Company considers a performance obligation to be distinct if the customer can benefit from the good or service either on its own or together with other resources readily available to the customer and the Company’s promise to transfer the goods or service to the customer is separately identifiable from other promises in the contract. The Company allocates revenue to each distinct performance obligation based on relative standalone selling prices. ​ Payment terms for sales of fuel cells, infrastructure and service to customers are typically 30 to 90 days. Sale/leaseback transactions with financial institutions are invoiced and collected upon transaction closing. Service is prepaid upfront in a majority of the arrangements. The Company does not adjust the transaction price for a significant financing component when the performance obligation is expected to be fulfilled within a year. ​ In 2017, in separate transactions, the Company issued to each of Amazon.com NV Investment Holdings LLC and Walmart warrants to purchase shares of the Company’s common stock. The Company presents the provision for common stock warrants within each revenue-related line item on the consolidated statements of operations. This presentation reflects a discount that those common stock warrants represent, and therefore revenue is net of these non-cash charges. The provision of common stock warrants is allocated to the relevant revenue-related line items based upon the expected mix of the revenue for each respective contract. See Note 18, “Warrant Transaction Agreements,’ for more details. ​ Nature of goods and services ​ The following is a description of principal activities from which the Company generates its revenue. ​ (j) Sales of Fuel Cell Systems and Related Infrastructure ​ Revenue from sales of fuel cell systems and related infrastructure represents sales of our GenDrive units, GenSure stationary backup power units, as well as hydrogen fueling infrastructure. ​ The Company uses a variety of information sources in determining standalone selling prices for fuel cells systems and related infrastructure. For GenDrive fuel cells, given the nascent nature of the Company’s market, the Company considers several inputs, including prices from a limited number of standalone sales as well as the Company’s negotiations with customers. The Company also considers its costs to produce fuel cells as well as comparable list prices in estimating standalone selling prices. The Company uses applicable observable evidence from similar products in the market to determine standalone selling prices for GenSure stationary backup power units and hydrogen fueling infrastructure. The determination of standalone selling prices of the Company’s performance obligations requires significant judgment, including periodic assessment of pricing approaches and available observable evidence in the market. Once relative standalone selling prices are determined, the Company proportionately allocates the transaction price to each performance obligation within the customer arrangement based upon standalone selling price. The allocated transaction price related to fuel cell systems and spare parts is recognized as revenue at a point in time which usually occurs at shipment (and occasionally upon delivery). Revenue on hydrogen infrastructure installations is generally recognized at the point at which transfer of control passes to the customer, which usually occurs upon customer acceptance of the hydrogen infrastructure. In certain instances, control of hydrogen infrastructure installations transfers to the customer over time, and the related revenue is recognized over time as the performance obligation is satisfied. The Company uses an input method to determine the amount of revenue to recognize during each reporting period when such revenue is recognized over time, based on the costs incurred to satisfy the performance obligation. ​ (ii) ​ Revenue from services performed on fuel cell systems and related infrastructure represents revenue earned on our service and maintenance contracts and sales of spare parts. The Company uses an adjusted market assessment approach to determine standalone selling prices for services. This approach considers market conditions and constraints, the Company’s market share, pricing strategies and objectives while maximizing the use of available observable inputs obtained from a limited number of historical standalone service renewal prices and negotiations with customers. The transaction price allocated to services as discussed above is generally recognized as revenue over time on a straight-line basis over the expected service period, as customers simultaneously receive and consume the benefits of routine, recurring maintenance performed throughout the contract period. ​ In substantially all of its commercial transactions, the Company sells extended maintenance contracts that generally provide for a five ​ Extended maintenance contracts generally do not contain customer renewal options. Upon expiration, customers may either negotiate a contract extension or switch to purchasing spare parts and maintaining the fuel cell systems on their own. (iii) ​ Revenue from PPAs primarily represents payments received from customers who make monthly payments to access for the Company’s GenKey solution. ​ Revenue associated with these agreements is recognized on a straight-line basis over the life of the agreements as the customers receive the benefits from the Company’s performance of the services. The customers receive services ratably over the contract term. ​ In conjunction with entering into a PPA with a customer, the Company may enter into transactions with third-party financial institutions in which it receives proceeds from the sale/leaseback transactions of the equipment and the sale of future service revenue. The proceeds from the financial institution are allocated between the sale of equipment and the sale of future service revenue based on the relative standalone selling prices of equipment and service. The proceeds allocated to the sale of future services are recognized as finance obligations. The proceeds allocated to the sale of the equipment are evaluated to determine if the transaction meets the criteria for sale/leaseback accounting. To meet the sale/leaseback criteria, control of the equipment must transfer to the financial institution, which requires among other criteria the leaseback to meet the criteria for an operating lease and the Company must not have a right to repurchase the equipment (unless specific criteria are met). These transactions typically meet the criteria for sale/leaseback accounting and accordingly, the Company recognizes revenue on the sale of the equipment, and separately recognizes the leaseback obligations. ​ The Company recognizes a lease liability for the equipment leaseback obligation based on the present value of the future payments to the financial institutions that are attributed to the equipment leaseback. The discount rate used to determine the lease liability is the Company’s incremental borrowing rate, which is based on an analysis of the interest rates on the Company’s secured borrowings. Adjustments that considered the Company’s actual borrowing rate, inclusive of securitization, as well as borrowing rates for companies of similar credit quality, were applied in the determination of the incremental borrowing rate. The Company also records a right of use asset which is amortized over the term of the leaseback. Rental expense is recognized on a straight-line basis over the life of the leaseback and is included as a cost of PPA revenue on the consolidated statements of operations. ​ Certain of the Company’s transactions with financial institutions do not meet the criteria for sale/leaseback accounting and accordingly, no equipment sale is recognized. All proceeds from these transactions are accounted for as finance obligations. The right of use assets related to these transactions are classified as equipment related to the PPAs and fuel delivered to the customers, net in the consolidated balance sheets. Costs to service the property, depreciation of the assets related to PPAs and fuel delivered to the customers, and other related costs are included in cost of PPA revenue in the consolidated statements of operations. The Company uses its transaction-date incremental borrowing rate as the interest rate for its finance obligations that arise from these transactions. No additional adjustments to the incremental borrowing rate have been deemed necessary for the finance obligations that have resulted from the failed sale/leaseback transactions. ​ In determining whether the sales of fuel cells and other equipment to financial institutions meet the requirements for revenue recognition under sale/leaseback accounting, the Company, as lessee, determines the classification of the lease. The Company estimates certain key inputs to the associated calculations such as: 1) discount rate used to determine the present value of future lease payments, 2) fair value of the fuel cells and equipment, and 3) useful life of the underlying asset(s): ​ ● ASC Topic 842 requires a lessee to discount its future lease payments using the interest rate implicit in the lease or, if that rate cannot be readily determined, its incremental borrowing rate. Generally, the Company cannot determine the interest rate implicit in its leases because it does not have access to the lessor’s estimated residual value or the amount of the lessor’s deferred initial direct costs. Therefore, the Company generally uses its incremental borrowing rate to estimate the discount rate for each lease. Adjustments that considered the Company’s actual borrowing rate, inclusive of securitization, as well as borrowing rates for companies of similar credit quality were applied in the determination of the incremental borrowing rate. ​ ● In order for the lease to be classified as an operating lease, the present value of the future lease payments cannot exceed 90% of the fair value of the leased assets. The Company estimates the fair value of the lease assets using the sales prices. ​ ● In order for a lease to be classified as an operating lease, the lease term cannot exceed 75% (major part) of the estimated useful life of the leased asset. The average estimated useful life of the fuel cells is 10 years , and the average estimated useful life of the hydrogen infrastructure is 20 years . These estimated useful lives are compared to the term of each lease to determine the appropriate lease classification. ​ (iv) ​ Revenue associated with fuel delivered to customers represents the sale of hydrogen to customers that has been purchased by the Company from a third party or generated on site. The stand-alone selling price is not estimated because it is sold separately and therefore directly observable. ​ The Company purchases hydrogen fuel from suppliers in most cases (and sometimes produces hydrogen onsite) and sells to its customers. Revenue and cost of revenue related to this fuel is recorded as dispensed and is included in the respective “Fuel delivered to customers” lines on the consolidated statements of operations. ​ Contract costs ​ The Company expects that incremental commission fees paid to employees as a result of obtaining sales contracts are recoverable and therefore the Company capitalizes them as contract costs. ​ Capitalized commission fees are amortized on a straight-line basis over the period of time which the transfer of goods or services to which the assets relate occur, typically ranging from 5 to 10 years. Amortization of the capitalized commission fees is included in selling, general and administrative expenses. ​ The Company recognizes the incremental costs of obtaining contracts as an expense when incurred if the amortization period of the assets that the Company otherwise would have recognized is one year or less. These costs are included in selling, general and administrative expenses. ​ Cash Equivalents ​ For purposes of the consolidated statements of cash flows, the Company considers all highly-liquid debt instruments with original maturities of three months or less to be cash equivalents. At December 31, 2020 and 2019, cash equivalents consist of money market accounts. The Company’s cash and cash equivalents are deposited with financial institutions located in the U.S. and may at times exceed insured limits. ​ Common Stock Warrant Accounting ​ The Company accounts for common stock warrants as either derivative liabilities or as equity instruments depending on the specific terms of the respective warrant agreements. ​ Accounts Receivable ​ Accounts receivable are stated at the amount billed or billable to customers and are ordinarily due between 30 and 60 days after the issuance of the invoice. Receivables are reserved or written off based on individual credit evaluation and specific circumstances of the customer. The allowance for doubtful accounts and related receivable are reduced when the amount is deemed uncollectible. As of December 31, 2020, and 2019, the allowance for doubtful accounts was $172 thousand and $249 thousand, respectively. ​ Inventory ​ Inventories are valued at the lower of cost, determined on a first-in, first-out basis, and net realizable value. All inventory, including spare parts inventory held at service locations, is not relieved until the customer has received the product, at which time the customer obtains control of the goods. ​ Property, Plant and Equipment ​ Property, plant and equipment are originally recorded at cost or, if acquired as part of business combination, at fair value. Maintenance and repairs are expensed as costs are incurred. Depreciation on plant and equipment, which includes depreciation on the Company’s primary manufacturing facility, which is accounted for as a financing obligation, is calculated on the straight-line method over the estimated useful lives of the assets. The Company records depreciation and amortization over the following estimated useful lives: ​ ​ ​ ​ Leasehold improvements 5 ‑ 10 years Software, machinery and equipment 1 ‑ 15 years ​ Gains and losses resulting from the sale of property and equipment are recorded in current operations. ​ Equipment related to PPAs and Fuel Delivered to Customers ​ Equipment related to PPAs and fuel delivered to customers primarily consists of the assets deployed related to PPAs and sites where we deliver fuel to customers. Equipment is depreciated over its useful life. Depreciation expense is recorded on a straight-line basis and is included in cost of revenue for PPAs or cost of fuel delivered to customers, respectively, in the consolidated statements of operations. ​ Impairment of Long-Lived Assets and PPA Executory Contract Considerations ​ We evaluate long-lived assets on a quarterly basis to identify events or changes in circumstances (“triggering events”) that indicate the carrying value of certain assets may not be recoverable. Long-lived assets that we evaluate include right of use lease assets, equipment deployed to our PPA’s, assets related primarily to our fuel delivery business and other company owned long-lived assets. ​ Upon the occurrence of a triggering event, long-lived assets are evaluated to determine if the carrying amounts are recoverable. The determination of recoverability is made based upon the estimated undiscounted future net cash flows of assets grouped at the lowest level for which there are identifiable cash flows independent of the cash flows of other groups. For operating assets, the Company has generally determined that the lowest level of identifiable cash flows is based on the customer sites. The assets related primarily to our fuel delivery business are considered to be their own asset group. The cash flows are estimated based on the remaining useful life of the primary asset within the asset group. ​ For assets related to our PPA agreements, we consider all underlying cash inflows related to our contract revenues and cash outflows relating to the costs incurred to service the PPA’s. Our cash flow estimates used in the recoverability test, are based upon, among other things, historical results adjusted to reflect our best estimate of future cash flows and operating performance. Development of future cash flows also requires us to make assumptions and to apply judgment, including timing of future expected cash flows, future cost savings initiatives, and determining recovery values. Changes to our key assumptions related to future performance and other economic and market factors could adversely affect the outcome of our recoverability tests and cause more asset groups to be tested for impairment. ​ If the estimated undiscounted future net cash flows for a given asset group are less than the carrying amount of the related asset group, an impairment loss is determined by comparing the estimated fair value with the carrying amount of the asset group. The impairment loss is then allocated to the long-lived assets in the asset group based on the asset’s relative carrying amounts. However, assets are not impaired below their then estimated fair values. Fair value is generally determined through various valuation techniques, including discounted cash flow models, quoted market values and third-party independent appraisals, as well as year-over-year trends in pricing of our new equipment and overall evaluation of our industry and market, as considered necessary. The Company considers these indicators with certain of its own internal indices and metrics in determining fair value in light of the nascent state of the Company’s market and industry. The estimate of fair value represents our best estimates of these factors and is subject to variability. Changes to our key assumptions related to future performance and other economic and market factors could adversely affect our impairment evaluation. ​ The Company has determined that the assets deployed for certain PPA arrangements are not recoverable based on the undiscounted estimated future cash flows of the asset group. However, the estimated fair value of the assets in the asset group equal or exceed the carrying amount of the assets or otherwise limit the amount of impairment that would have been recognized. The Company has identified the primary source of the losses as the maintenance components of the PPA arrangements and the impact of customer warrant non-cash provisions. As the PPA arrangements are considered to be executory contracts and there is no specific accounting guidance that permits loss recognition for these revenue contracts, the Company has not recognized a provision for the expected future losses under these revenue arrangements. The Company expects that it will recognize future losses for these arrangements as it continues its efforts to reduce costs of delivering the maintenance component of these arrangements. ​ Extended Maintenance Contracts ​ On a quarterly basis, we evaluate any potential losses related to our extended maintenance contracts for fuel cell systems and related infrastructure that has been sold. We measure loss accruals at the customer contract level. The expected revenues and expenses for these contracts include all applicable expected costs of providing services over the remaining term of the contracts and the related unearned net revenue. A loss is recognized if the sum of expected costs of providing services under the contract exceeds related unearned net revenue and is recorded as a provision for loss contracts related to service in the consolidated statement of operations. A key component of these estimates is the expected future service costs. In estimating the expected future service costs, the Company considers its current service cost level and applies significant judgment related to expected cost saving initiatives. The expected future cost savings will be primarily dependent upon the success of the Company’s initiatives related to increasing stack life, achieving better economies of scale on service labor, and improvements in design and operations of infrastructure. If the expected cost saving initiatives are not realized, this will increase the costs of providing services and could adversely affect our estimated contract loss accrual. ​ The following table shows the roll forward of balances in the accrual for loss contracts, including changes due to the provision (benefit) for loss accrual, releases to service cost of sales and releases due to the provision for warrants (in thousands): ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ December 31, 2020 ​ December 31, 2019 ​ December 31, 2018 ​ ​ ​ ​ ​ (as restated) ​ ​ (as restated) Beginning Balance $ 3,702 ​ $ 5,345 ​ $ — Provision (benefit) for Loss Accrual ​ 35,473 ​ ​ (394) ​ ​ 5,345 Released to Service Cost of Sales ​ (2,348) ​ ​ (1,249) ​ ​ — Released to Provision for Warrants ​ (12,814) ​ ​ — ​ ​ — Ending Balance $ 24,013 ​ $ 3,702 ​ $ 5,345 ​ Goodwill and indefinite-lived intangible asset ​ Goodwill is an asset representing the future economic benefits arising from other assets acquired in a business combination that are not individually identified and separately recognized. Goodwill is reviewed for impairment at least annually. The indefinite-lived intangible asset represents in-process research and development for cumulative research and development efforts associated with dry stack electrolyzer technology acquired in connection with the Giner ELX, Inc. acquisition. ​ The Company has the option to perform a qualitative assessment to determine whether it is more-likely-than-not that the fair value of a reporting unit is less than its carrying amount. If this is the case, the quantitative goodwill impairment test is required. If it is more-likely-than-not that the fair value of a reporting unit is greater than its carrying amount, the quantitative goodwill impairment test is not required. ​ The indefinite-lived intangible asset is tested for impairment annually, and more frequently when there is a triggering event. Annually, or when there is a triggering event, the Company first performs a qualitative assessment by evaluating all relevant events and circumstances to determine if it is more likely than not that the indefinite-lived intangible asset is impaired; this includes considering any potential effect on significant inputs to determining the fair value of the indefinite-lived intangible asset. When it is more likely than not that the indefinite-lived intangible asset is impaired, then the Company calculates the fair value of the intangible asset and performs a quantitative impairment test. ​ The Company performs an impairment review of goodwill and the indefinite lived intangible asset on an annual basis at December 1, and when a triggering event is determined to have occurred between annual impairment tests. For the years ended December 31, 2020, 2019, and 2018, the Company performed a qualitative assessment of goodwill for its single reporting unit based on multiple factors including market capitalization and determined that it is not more likely than not that the fair value of its reporting unit is less than the carrying amount. For the year ended December 31, 2020, the Company performed a qualitative assessment of its indefinite lived intangible asset and determined that it is not more likely than not that its fair value is less than the carrying amount. ​ Intangible Assets ​ ​ Fair Value Measurements ​ The Company records the fair value of assets and liabilities in accordance with ASC 820, Fair Value Measurement ​ In addition to defining fair value, ASC 820 expands the disclosure requirements around fair value and establishes a fair value hierarchy for valuation inputs. The hierarchy prioritizes the inputs into three levels based on the extent to which inputs used in measuring fair value are observable in the market. Each fair value measurement is reported in one of the three levels, which is determined by the lowest level input that is significant to the fair value measurement in its entirety. ​ These levels are: ​ ● Level 1 — quoted prices (unadjusted) in active markets for identical assets or liabilities. ● Level 2 — quoted prices for similar assets and liabilities in active markets or inputs that are observable for the asset or liability, either directly or indirectly through market corroboration, for substantially the full term of the financial instrument. ● Level 3 — unobservable inputs reflecting management’s own assumptions about the inputs used in pricing the asset or liability at fair value. ​ The following table summarizes the carrying amount and estimated fair value of the Company’s financial instruments at December 31, 2020 and 2019 (in thousands): ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Carrying ​ Fair ​ Fair Value Measurements As of December 31, 2020 ​ Amount ​ Value ​ Level 1 ​ Level 2 ​ Level 3 Contingent consideration $ 9,760 $ 9,760 $ — $ — $ 9,760 Convertible senior notes ​ 85,640 ​ 1,272,766 ​ — ​ 1,272,766 ​ — Long-term debt ​ 175,402 ​ 175,402 ​ — ​ — ​ 175,402 Finance obligations ​ 181,553 ​ 181,553 ​ — ​ — ​ 181,553 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Carrying ​ Fair ​ Fair Value Measurements As of December 31, 2019 ​ Amount ​ Value ​ Level 1 ​ Level 2 ​ Level 3 Convertible senior notes $ 110,431 $ 188,775 $ — $ 135,320 $ 53,455 Long-term debt ​ 112,169 ​ 112,169 ​ — ​ — ​ 112,169 Finance obligations ​ 144,089 ​ 144,089 ​ — ​ — ​ 144,089 ​ Equity Instruments ​ Common stock warrants that meet certain applicable requirements of ASC Subtopic 815-40, Derivatives and Hedging – Contracts in Entity’s Own Equity ​ Common stock warrants accounted for as equity instruments represent the warrants issued to Amazon and Walmart as discussed in Note 18, “Warrant Transaction Agreements.” The Company adopted FASB ASU 2019-08, Compensation – Stock Compensation (Topic 718) and Revenue from Contracts with Customers (Topic 606), which requires entities to measure and classify share-based payment awards granted to a customer by applying the guidance under Topic 718, as of January 1, 2019. ​ In order

Acquisitions

Acquisitions	12 Months Ended
	Dec. 31, 2020
Acquisitions
Acquisitions	​ 5. Acquisitions ​ Giner ELX Inc. Acquisition On June 22, 2020, the Company acquired 100% of the outstanding shares of Giner ELX, Inc. (“Giner ELX”). Giner ELX is developer of electrolysis hydrogen generators which can be used for a variety of applications, including on-site refueling of hydrogen fuel cells. ​ The fair value of consideration paid by the Company in connection with the Giner ELX acquisition was as follows (in thousands): ​ ​ ​ ​ Cash $ 25,820 Plug Power Stock ​ 19,263 Contingent consideration ​ 7,790 Total consideration $ 52,873 ​ The contingent consideration represents the estimated fair value associated with earn-out payments of up to $16.0 million that the sellers are eligible to receive. Of the total earnout consideration, $8.0 million is related to the achievement of the Allagash earn-out, $2.0 million is associated with the receipt of certain customer opportunities (purchase orders or other contracts) by December 31, 2021, and $6.0 million is associated with the achievement of certain revenue targets for years 2021 through 2023. The Allagash earn-out is achieved when the Company has produced at least two PEM electrolyzer stacks of one megawatt each, utilizing the dry build process and meets certain technical specifications as more fully described in the merger agreement. To be fully paid, the Allagash earn-out needs to be satisfied by July 31, 2023 and is reduced by approximately 8.33% each month beyond this date. In addition to the above, should the earn-out revenue exceed 150% of the 2023 target, the sellers will receive warrants with a value of $5.0 million and if the earn-out revenue exceeds 200% of the 2023 revenue target, the sellers will receive warrants with a value of $10.0 million. The warrants are exercisable within two years of issuance. ​ In connection with the Giner ELX acquisition, the Company revised the acquisition-date fair value of contingent consideration liabilities which were determined to be measurement period adjustments and resulted in an increase in other liabilities and goodwill ​ The following table summarizes the final allocation of the purchase price to the estimated fair value of the net assets acquired, excluding goodwill (in thousands): ​ ​ ​ ​ Accounts receivable $ 1,237 Inventory 4,108 Prepaid expenses and other assets ​ 669 Property, plant and equipment ​ 596 Identifiable intangibles ​ 29,930 Accounts payable, accrued expenses and other liabilities ​ (1,621) Deferred revenue ​ (2,350) Deferred tax liability, net ​ (5,889) Total net assets acquired, excluding goodwill $ 26,680 ​ Identifiable intangibles consisted of developed technology, non-compete agreements, estimated in-process research and development (“IPR&D”), and customer relationships. ​ The fair value of acquired backlog and non-complete agreements was nominal. ​ The fair value of the acquired IPR&D related to the dry stack technology totaling $29.0 million was calculated using the multi-period excess earnings method (“MPEEM”) approach which is a variant of the income approach. The basic principle of the MPEEM approach is that a single asset, in isolation, is not capable of generating cash flow for an enterprise. Several assets are brought together and exploited to generate cash flow. Therefore, to determine cash flow from the exploitation of IPR&D, one must deduct the related expenses incurred for the exploitation of other assets used for the generation of overall cash flow and revenues. The fair value of IPR&D was estimated by discounting the net cash flow derived from the expected revenues attributable to the acquired IPR&D. The fair value of the acquired customer relationships totaling $0.4 million was calculated using a distributor method approach, which is a variant of the income approach. The fair value of wet stack technology totaling $0.4 million was determined using the relief from royalty method. ​ In addition to identifiable intangible assets, the fair value of acquired work in process and finished goods inventory was estimated based on the estimated selling price less costs to be incurred and a market participant profit rate. Additionally, the fair value of the deferred revenue was determined using a cost build-up approach. The direct cost of fulfilling the obligation plus a normal profit margin was used to determine the value of the assumed deferred revenue liability. ​ Included in the purchase consideration are three contingent earn-out payments (as described above): the Allagash earn-out, the customer opportunities, and the revenue targets. Due to the nature of the Allagash and customer opportunities, as outlined in the purchase agreement, a scenario based method (“SBM”) was used to value these contingent payments as the payments are milestone based in nature. These fair value measurements were based on unobservable inputs and are considered to be level 3 financial instruments. The revenue targets are achieved when certain revenue thresholds are met, and the catch-up provision creates path-dependency. As such, the revenue earn-out was valued using a Monte Carlo Simulation. ​ In connection with the acquisition, the Company recorded on its consolidated balance sheet a liability of $7.8 million representing the fair value of contingent consideration payable. The fair value of this contingent consideration was remeasured as of December 31, 2020, and was estimated to be $9.6 million. This increase in fair value of $1.8 million, which was primarily due to a change in the discount rate offset by a decrease in the discount period, was recorded as an expense in the consolidated statement of operations for the year ended December 31, 2020. ​ Included in Giner ELX’s net assets acquired are net deferred tax liabilities of $5.9 million. In connection of the acquisition of these net deferred tax liabilities, the Company reduced its valuation allowance by $5.2 million and recognized a tax benefit $5.2 million during the year ended December 31, 2020. ​ Goodwill associated with the Giner ELX acquisition was calculated as follows (in thousands): ​ ​ ​ ​ Consideration paid $ 52,873 Less: net assets acquired ​ (26,680) Total goodwill recognized $ 26,193 ​ The goodwill consists of the Company’s increased capabilities in green hydrogen supply through the production of electrolyzers. The synergies with the Company’s production of hydrogen storage and dispensing equipment are important to the Company as the demand for green hydrogen is expected to increase. ​ United Hydrogen Group Inc. Acquisition On June 18, 2020, the Company acquired 100% of the outstanding shares of United Hydrogen Group Inc. (“UHG”). UHG produces and sells liquid hydrogen. ​ The fair value of consideration paid by the Company in connection with the UHG acquisition was as follows (in thousands): ​ ​ ​ ​ Cash $ 19,293 Plug Power Stock ​ 30,410 Contingent consideration ​ 1,110 Total consideration $ 50,813 ​ Included in cash and common stock in the above table is $1.0 million of cash and $6.5 million of common stock that was paid in April 2020 to purchase a convertible note in UHG. This convertible note included terms that allowed for reduction of the purchase price if the Company were to complete the acquisition of UHG. As such, this note was cancelled in conjunction with the closing of this acquisition. ​ A portion of the purchase price of UHG was in the form of contingent consideration. The contingent consideration is contingent on future performance related to two discrete milestones associated with the expansion of the liquefication capacity of the Charleston, Tennessee liquid hydrogen plant (the “Charleston Plant”). The Company’s liability for this contingent consideration was measured at fair value based on the Company’s expectations of achieving the expansion milestone. The expected performance was assessed by management which was discounted to present value in order to derive a fair value of the contingent consideration. This fair value measurement was based on unobservable inputs and is considered a level 3 financial instrument. Due to the milestone nature of the payments, a scenario based method (“SBM”) was used to value these contingent payments. ​ The estimated fair value of the contingent consideration as of the acquisition date was $1.1 million. . ​ The following table summarizes the final allocation of the purchase price to the estimated fair value of the net assets acquired, excluding goodwill (in thousands): ​ ​ ​ ​ Accounts receivable $ 444 Inventory 89 Prepaid expenses and other assets ​ 1,152 Property, plant and equipment 41,244 Leased property ​ 796 Identifiable intangible asset 2,338 Long-term debt ​ (11,336) Unfavorable customer contract ​ (15,757) Accounts payable, accrued expenses, deferred revenue and finance obligations ​ (4,631) Total net assets acquired, excluding goodwill $ 14,339 ​ The identifiable intangible asset consisted of developed technology, as described below in Note 10, “Intangible Assets and Goodwill.” The fair value of the developed technology totaling $2.3 million was calculated using the relief from royalty approach which is a variant of the income approach. The application of the relief from royalty approach involves estimating the value of an intangible asset by quantifying the present value of the stream of market derived royalty payments that the owner of the intangible asset is exempted or ‘relieved’ from paying. ​ Additionally, the Company estimated the fair value of an unfavorable customer contract. The fair value of the acquired unfavorable customer contract was calculated using a with and with-out analysis which is a variant of the income approach. Cash flows were calculated using pricing per terms of the existing contract and then compared to cash flows using expected market pricing. The difference between the two cash flows was used to determine the fair value of the contract. Further, the Company assumed interest-bearing debt. The fair value of the assumed debt was calculated using the discounted cash flow method. ​ In connection with the UHG acquisition, the Company finalized the valuation of an unfavorable customer contract and long-term debt which resulted in an increase in other liabilities of $1.9 million, a decrease in long-term debt of $1.7 million, and an increase in goodwill of $0.2 million. ​ Goodwill associated with the UHG acquisition was calculated as follows (in thousands): ​ ​ ​ ​ Consideration paid $ 50,813 Less: net assets acquired ​ (14,339) Total goodwill recognized $ 36,474 ​ The Company now has capabilities in liquid hydrogen generation, liquefaction and distribution logistics, which is important in a growing hydrogen market. ​ Goodwill recorded in connection with the acquisitions is not deductible for tax purposes. ​ The results ​ Neither the Giner ELX acquisition nor the UHG acquisition was material to our consolidated results of operations or financial position and, therefore, pro forma financial information is not presented.

Earnings Per Share

Earnings Per Share	12 Months Ended
	Dec. 31, 2020
Earnings Per Share
Earnings Per Share	6. Earnings Per Share, as restated ​ Basic earnings per common stock are computed by dividing net loss attributable to common stockholders by the weighted average number of common stock outstanding during the reporting period. Diluted earnings per share reflects the potential dilution that could occur if securities or other contracts to issue common stock (such as stock options, unvested restricted stock, common stock warrants, and preferred stock) were exercised or converted into common stock or resulted in the issuance of common stock (net of any assumed repurchases) that then shared in the earnings of the Company, if any. This is computed by dividing net earnings by the combination of dilutive common stock equivalents, which is comprised of shares issuable under outstanding warrants, the conversion of preferred stock, and the Company’s share-based compensation plans, and the weighted average number of common stock outstanding during the reporting period. Since the Company is in a net loss position, all common stock equivalents would be considered to be anti-dilutive and are, therefore, not included in the determination of diluted earnings per share. Accordingly, basic and diluted loss per share are the same. ​ The following table provides the components of the calculations of basic and diluted earnings per share (in thousands, except share amounts): ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Year ended December 31, ​ ​ ​ ​ ​ ​ 2019 ​ ​ 2018 ​ ​ 2020 (as restated) ​ (as restated) ​ Numerator: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Net loss attributable to common stockholders ​ $ (596,181) ​ $ (85,555) ​ $ (85,660) ​ Denominator: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Weighted average number of common stock outstanding ​ 354,790,106 ​ 237,152,780 ​ 218,882,337 ​ ​ The potentially dilutive securities are summarized as follows: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ At December 31, ​ 2020 2019 2018 Stock options outstanding (1) ​ 10,284,498 23,013,590 21,957,150 Restricted stock outstanding (2) ​ 5,874,642 4,608,560 2,347,347 Common stock warrants (3) ​ 104,753,740 ​ 110,573,392 ​ 115,824,142 Preferred stock (4) ​ — 2,998,527 17,933,591 Convertible Senior Notes (5) ​ 42,256,610 59,133,896 43,630,020 Number of dilutive potential shares of common stock ​ 163,169,490 200,327,965 ​ 201,692,250 ​ (1) During the years ended December 31, 2020, 2019, and 2018, the Company granted 3,509,549 , 3,221,892 , and 2,679,667 stock options, respectively. ​ (2) During the years ended December 31, 2020, 2019, and 2018, the Company granted 3,227,149 , 3,201,892 , and 2,367,347 shares of restricted stock, respectively. ​ (3) In April 2017, the Company issued a warrant to acquire up to 55,286,696 of the Company’s common stock as part of a transaction agreement with Amazon, subject to certain vesting events, as described in Note 18, “Warrant Transaction Agreements.” The warrant had not been exercised as of December 31, 2020. ​ In July 2017, the Company issued a warrant to acquire up to 55,286,696 of the Company’s common stock as part of a transaction agreement with Walmart, subject to certain vesting events, as described in Note 18, “Warrant Transaction Agreements.” The warrant had been exercised with respect to 5,819,652 shares as of December 31, 2020. ​ (4) The preferred stock amount represents the dilutive potential on the shares of common stock as a result of the conversion of the Series C Redeemable Convertible Preferred Stock (Series C Preferred Stock) and Series E Convertible Preferred Stock (Series E Preferred Stock), based on the conversion price of each preferred stock as of December 31 2019, and 2018, respectively. Of the 10,431 shares of Series C Preferred Stock issued on May 16, 2013, all shares had been converted to common stock as of December 31, 2020. On November 1, 2018, the Company issued 35,000 shares of Series E Preferred Stock. As of December 31, 2019, 30,462 shares of the Series E Preferred Stock had been converted to common stock and 4,038 shares were redeemed for cash. All of the remaining Series E Preferred Stock were converted to either common stock or cash, in January 2020 . ​ (5) In March 2018, the Company issued the 5.5% Convertible Senior Notes. In September 2019, the Company issued the $7.5% Convertible Senior Note, which was fully converted into 16.0 million shares on July 1, 2020. In May 2020, the Company issued the 3.5% Convertible Senior Notes and repurchased $66.3 million of the 5.5% Convertible Senior Notes. In the fourth quarter of 2020, $33.5 million of the remaining 5.5% Convertible Senior Notes converted into 14.6 million shares of common stock. As of December 31, 2020, approximately $160 thousand aggregate principal amount of the 5.5% Convertible Senior Notes remained outstanding, all of which was converted in January 2021 .

Inventory

Inventory	12 Months Ended
	Dec. 31, 2020
Inventory
Inventory	7. Inventory, as restated ​ Inventory as of December 31, 2020 and 2019 as restated, consists of the following (in thousands): ​ ​ ​ ​ ​ ​ ​ ​ ​ December 31, 2020 December 31, 2019 ​ ​ ​ ​ ​ ​ (as restated) Raw materials and supplies - production locations ​ $ 92,221 ​ $ 48,011 Raw materials and supplies - customer locations ​ ​ 12,405 ​ ​ 9,241 Work-in-process ​ 29,349 ​ 12,529 Finished goods ​ 5,411 ​ 2,610 Inventory ​ $ 139,386 ​ $ 72,391 ​

Property, Plant and Equipment

Property, Plant and Equipment	12 Months Ended
	Dec. 31, 2020
Property, Plant and Equipment
Property, Plant and Equipment	8. Property, Plant and Equipment ​ Property, plant and equipment at December 31, 2020 and 2019 consists of the following (in thousands): ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ December 31, 2020 ​ December 31, 2019 Land ​ ​ 1,165 ​ ​ — ​ Leasehold improvements ​ $ 1,121 ​ $ 862 ​ Software, machinery and equipment ​ 94,449 ​ 31,514 ​ Property, plant, and equipment ​ 96,735 ​ 32,376 ​ Less: accumulated depreciation ​ (22,186) ​ (17,417) ​ Property, plant, and equipment, net ​ $ 74,549 ​ $ 14,959 ​ ​ Depreciation expense related to property, plant and equipment was $4.8 million, $3.6 million, and $2.6 million for the years ended December 31, 2020, 2019, and 2018, respectively.

Equipment Related to Power Purc

Equipment Related to Power Purchase Agreements and Fuel Delivered to Customers, net	12 Months Ended
	Dec. 31, 2020
Equipment Related to Power Purchase Agreements and Fuel Delivered to Customers, net
Equipment Related to Power Purchase Agreements and Fuel Delivered to Customers, net	9. Equipment Related to Power Purchase Agreements and Fuel Delivered to Customers, net, as restated ​ Equipment related to power purchase agreements and fuel delivered to customers, net, at December 31, 2020 and 2019 consists of the following (in thousands): ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ December 31, 2019 ​ ​ December 31, 2020 ​ (as restated) Equipment related to power purchase agreements and fuel delivered to customers ​ ​ 92,736 ​ ​ 81,194 Less: accumulated depreciation ​ (16,929) ​ (13,425) Equipment related to power purchase agreements and fuel delivered to customers, net ​ $ 75,807 ​ $ 67,769 ​ As of December 31, 2020, the Company had deployed assets at customer sites that had associated PPAs. These PPAs expire over the next one ten ​ Depreciation expense is $7.9 million and $6.3 million for the years ended December 31, 2020 and 2019 respectively.

Intangible Assets and Goodwill

Intangible Assets and Goodwill	12 Months Ended
	Dec. 31, 2020
Intangible Assets and Goodwill
Intangible Assets and Goodwill	10. Intangible Assets and Goodwill ​ The gross carrying amount and accumulated amortization of the Company’s acquired identifiable intangible assets as of December 31, 2020 are as follows (in thousands): ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Weighted Average ​ Gross Carrying ​ Accumulated ​ ​ ​ ​ ​ Amortization Period ​ Amount ​ Amortization ​ Total Acquired technology 10 years $ 13,697 ​ $ (4,042) ​ $ 9,655 Customer relationships, Non-compete agreements, Backlog & Trademark 6 years ​ 890 ​ ​ (294) ​ ​ 596 In process research and development ​ Indefinite ​ ​ 29,000 ​ ​ — ​ ​ 29,000 ​ ​ ​ ​ $ 43,587 ​ $ (4,336) ​ $ 39,251 ​ The gross carrying amount and accumulated amortization of the Company’s acquired identifiable intangible assets as of December 31, 2019 are as follows (in thousands): ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Weighted Average ​ Gross Carrying ​ Accumulated ​ ​ ​ ​ ​ Amortization Period ​ Amount ​ Amortization ​ Total Acquired technology 9 years ​ $ 8,244 ​ $ (2,815) ​ $ 5,429 Trademark 9 years ​ 320 ​ ​ (210) ​ 110 ​ ​ ​ ​ $ 8,564 ​ $ (3,025) ​ $ 5,539 ​ The change in the gross carrying amount of the acquired technology from December 31, 2019 to December 31, 2020 was due to changes in acquisitions of UHG and Giner ELX, American Fuel Cell (AFC) milestone payments and foreign currency translation, as discussed below. ​ The Company’s in-process research and development is related to the development of the dry build process associated with electrolyzer stacks, as part of acquisition of Giner ELX. The related intangible asset is not currently amortized, as research and development is ongoing. Upon completion of the dry build process, amortization will commence based upon the estimated useful life of the underlying asset. See Note 5, “Acquisitions” for more details. ​ Also, in 2020, the Company acquired technology as part of the acquisition of UHG. The technology relates to the chemical process of manufacturing liquid hydrogen from chlor-alkali waste stream. See Note 5 “Acquisitions”, for more details. ​ In 2019, the Company acquired intellectual property from EnergyOr for $1.5 million. In addition, the Company agreed to pay the sellers a royalty based on future sales of relevant applications, not to exceed $3.0 million, by May 22, 2025. These royalties are added to the intangible asset balance, as incurred. To date, no royalties have been earned. ​ As of December 31, 2020, as part of the agreement to acquire the intellectual property from AFC, the Company paid AFC milestone payments of $2.9 million. ​ Amortization expense for acquired identifiable intangible assets for the years ended December 31, 2020, 2019 and 2018 was $1.1 million, $0.7 million and $0.7 million, respectively. ​ Estimated amortization expense for subsequent years was as follows (in thousands): ​ ​ ​ ​ ​ 2021 ​ ​ 1,878 2022 ​ ​ 1,478 2023 ​ ​ 1,478 2024 ​ ​ 1,456 2025 and thereafter ​ ​ 3,961 Total ​ $ 10,251 ​ Goodwill was $72.4 million and $8.8 million as of December 31, 2020 and 2019 respectively, which increased $62.6 million as a result of the Giner ELX and UHG acquisitions, and increased $900 thousand due to translation gain for Hypulsion goodwill. There were no impairments during the fiscal years ended December 31, 2020 and 2019.

Accrued Expenses

Accrued Expenses	12 Months Ended
	Dec. 31, 2020
Accrued Expenses
Accrued Expenses	11. Accrued Expenses, as restated ​ Accrued expenses at December 31, 2020 and 2019 consist of (in thousands): ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ 2019 ​ ​ 2020 ​ (as restated) ​ Accrued payroll and compensation related costs ​ $ 29,167 ​ $ 2,932 ​ Accrued accounts payable ​ ​ 11,750 ​ ​ 7,254 ​ Accrued sales and other taxes ​ ​ 3,665 ​ ​ 905 ​ Accrued interest ​ ​ 649 ​ ​ 2,374 ​ Accrued other ​ ​ 852 ​ ​ 944 ​ Total ​ $ 46,083 ​ $ 14,409 ​ ​

Operating and Finance Lease Lia

Operating and Finance Lease Liabilities	12 Months Ended
	Dec. 31, 2020
Operating and Finance Lease Liabilities
Operating and Finance Lease Liabilities	12. Operating and Finance Lease Liabilities, as restated ​ As of December 31, 2020, the Company had operating leases, as lessee, primarily associated with sale/leaseback transactions that are partially secured by restricted cash, security deposits and pledged escrows (see also Note 1, “Nature of Operations”) as summarized below. These leases expire over the next one ​ Leases contain termination clauses with associated penalties, the amount of which cause the likelihood of cancellation to be remote. At the end of the lease term, the leased assets may be returned to the lessor by the Company, the Company may negotiate with the lessor to purchase the assets at fair market value, or the Company may negotiate with the lessor to renew the lease at market rental rates. No residual value guarantees are contained in the leases. No financial covenants are contained within the lease, however there are customary operational covenants such as assurance the Company properly maintains the leased assets and carries appropriate insurance, etc. The leases include credit support in the form of either cash, collateral or letters of credit. See Note 22, “Commitments and contingencies, as restated,” for a description of cash held as security associated with the leases. ​ The Company has finance leases associated with its property and equipment in Latham, New York and at fueling customer locations. The fair value of this finance obligation approximated the carrying value as of December 31, 2020. ​ Future minimum lease payments under operating and finance leases (with initial or remaining lease terms in excess of one year) as of December 31, 2020 were as follows (in thousands): ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Finance ​ Total ​ ​ Operating Lease ​ Lease ​ Lease ​ ​ Liability ​ Liability ​ Liabilities 2021 $ 28,536 ​ $ 1,261 ​ $ 29,797 2022 ​ 27,138 ​ 1,234 ​ ​ 28,372 2023 ​ 26,464 ​ 1,210 ​ ​ 27,674 2024 ​ 25,947 ​ 1,293 ​ ​ 27,240 2025 and thereafter ​ 50,362 ​ ​ 1,721 ​ ​ 52,083 Total future minimum payments ​ 158,447 ​ 6,719 ​ ​ 165,166 Less imputed interest ​ (44,509) ​ ​ (1,323) ​ ​ (45,832) Total $ 113,938 ​ $ 5,396 ​ $ 119,334 ​ Rental expense for all operating leases was $22.3 million, $14.6 million and $10.2 million for the years ended December 31, 2020, 2019 and 2018, respectively. ​ The gross profit on sale/leaseback transactions for all operating leases was $61.0 million, $26.2 million and $16.4 million for the years ended December 31, 2020, 2019 and 2018, respectively. Right of use assets obtained in exchange for new operating lease liabilities was $58.5 million and $37.7 million for the years ended December 31, 2020 and 2019, respectively. ​ At December 31, 2020 and 2019, the right of use assets associated with operating leases was $117.0 million and $63.3 million, respectively. The accumulated depreciation for these right of use assets was $48.6 million and $23.6 million at December 31, 2020 and 2019, respectively. ​ At December 31, 2020 and 2019, the right of use assets associated with finance leases was $5.7 million and $1.7 million, respectively. The accumulated depreciation for these right of use assets was $102 thousand and $32 thousand at December 31, 2020 and 2019, respectively. ​ At December 31, 2020 and 2019, security deposits associated with sale/leaseback transactions were $5.8 million and $6.0 million, respectively, and were included in other assets in the consolidated balance sheet. ​ Other information related to the operating leases are presented in the following table: ​ ​ ​ ​ ​ ​ ​ ​ ​ Year ended ​ ​ Year ended ​ ​ December 31, 2020 ​ ​ December 31, 2019 Cash payments (in thousands) $ 22,626 ​ $ 14,055 Weighted average remaining lease term (years) ​ 6.0 ​ ​ 5.0 Weighted average discount rate ​ 11.7% ​ ​ 12.1% ​ Finance lease costs include amortization of the right of use assets (i.e. depreciation expense) and interest on lease liabilities (i.e. interest and other expense, net in the consolidated statement of operations), and were immaterial for the years ended December 31, 2019 and 2018. ​ Right of use assets obtained in exchange for new finance lease liabilities were $4.1 million and $0.1 million for the years ended December 31, 2020 and 2019, respectively. ​ Other information related to the finance leases are presented in the following table: ​ ​ ​ ​ ​ ​ ​ ​ ​ Year ended ​ ​ Year ended ​ ​ December 31, 2020 ​ ​ December 31, 2019 Cash payments (in thousands) $ 471 ​ $ 255 Weighted average remaining lease term (years) ​ 5.6 ​ ​ 7.7 Weighted average discount rate ​ 8.2% ​ ​ 8.8% ​

Finance Obligations

Finance Obligations	12 Months Ended
	Dec. 31, 2020
Finance Obligations
Finance Obligations	13. Finance Obligation, as restated ​ The Company has sold future services to be performed associated with certain sale/leaseback transactions and recorded the balance as a finance obligation. The outstanding balance of this obligation at December 31, 2020 was $157.7 million, $24.7 million and $132.9 million of which was classified as short-term and long-term, respectively, on the accompanying consolidated balance sheet. The outstanding balance of this obligation at December 31, 2019 was $112.4 million, $16.8 million and $95.6 million of which was classified as short-term and long-term, respectively. The amount is amortized using the effective interest method. The fair value of this finance obligation approximated the carrying value as of December 31, 2020. ​ In prior periods, the Company entered into sale/leaseback transactions that were accounted for as financing transactions and reported as part of finance obligations. The outstanding balance of finance obligations related to sale/leaseback transactions at December 31, 2020 was $23.9 million, $8.0 million and $15.9 million of which was classified as short-term and long-term, respectively on the accompanying consolidated balance sheet. The outstanding balance of this obligation at December 31, 2019 was $31.7 million, $7.9 million and $23.8 million of which was classified as short-term and long-term, respectively on the accompanying consolidated balance sheet. The fair value of this finance obligation approximated the carrying value as of both December 31, 2020 and December 31, 2019. ​ Future minimum payments under finance obligations notes above as of December 31, 2020 were as follows (in thousands): ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Total ​ ​ Sale of Future ​ ​ Sale/leaseback Finance ​ ​ revenue - debt ​ ​ financings Obligations 2021 $ 41,670 ​ $ 9,327 ​ $ 50,997 2022 ​ 39,268 ​ ​ 4,975 ​ ​ 44,243 2023 ​ 39,268 ​ ​ 3,149 ​ ​ 42,417 2024 ​ 39,268 ​ ​ 16,154 ​ ​ 55,422 2025 and thereafter ​ 53,385 ​ ​ — ​ ​ 53,385 Total future minimum payments ​ 212,859 ​ ​ 33,605 ​ ​ 246,464 Less imputed interest ​ (55,158) ​ ​ (9,753) ​ ​ (64,911) Total $ 157,701 ​ $ 23,852 ​ $ 181,553 ​ Other information related to the above finance obligations are presented in the following table: ​ ​ ​ ​ ​ ​ ​ ​ ​ Year ended ​ ​ Year ended ​ ​ December 31, 2020 ​ ​ December 31, 2019 Cash payments (in thousands) $ 44,245 ​ $ 76,244 Weighted average remaining term (years) ​ 5.0 ​ ​ 5.3 Weighted average discount rate ​ 11.3% ​ ​ 11.2% ​

Long-Term Debt

Long-Term Debt	12 Months Ended
	Dec. 31, 2020
Long-Term Debt
Long-Term Debt	14. Long-Term Debt In March 2019, the Company entered into a loan and security agreement, as amended (the ”Loan Agreement”), with Generate Lending, LLC (“Generate Capital”), providing for a secured term loan facility in the amount of $100 million (the “Term Loan Facility”). The Company used the proceeds to pay off in full the Company’s previous loan with NY Green Bank a Division of the New York State Energy Research & Development (“Green-Bank Loan”) and terminate and re-purchase certain equipment leases with Generate Plug Power SLB II, LLC. In connection with this transaction, the Company recognized a loss on extinguishment of debt of approximately $0.5 million during the year ended December 31, 2019. This loss was recorded in gain (loss) on extinguishment of debt, in the Company’s consolidated statement of operations. The Company borrowed an incremental $20 million in November 2019. ​ Additionally, during the year ended December 31, 2020, the Company, under another series of amendments to the Loan Agreement, borrowed an incremental $100 million. As part of the amendment to the Loan Agreement, the Company’s interest rate on the secured term loan facility was reduced to 9.50% from 12.00% per annum, and the maturity date was extended to October 31, 2025 from October 6, 2022. On December 31, 2020, the outstanding balance under the Term Loan Facility was $165.8 million. ​ The Loan Agreement includes covenants, limitations, and events of default customary for similar facilities. Interest and a portion of the principal amount is payable on a quarterly basis. Principal payments will be funded in part by releases of restricted cash, as described in Note 22, “Commitments and Contingencies, as restated.” Based on the amortization schedule as of December 31, 2020, the aforementioned loan balance under the Term Loan Facility will be fully paid by October 31, 2025. The Company is in compliance with, or has obtained waivers for, all debt covenants. The Term Loan Facility is secured by substantially all of the Company’s and the guarantor subsidiaries’ assets, including, among other assets, all intellectual property, all securities in domestic subsidiaries and 65% of the securities in foreign subsidiaries, subject to certain exceptions and exclusions. ​ The Loan Agreement provides that if there is an event of default due to the Company’s insolvency or if the Company fails to perform in any material respect the servicing requirements for fuel cell systems under certain customer agreements, which failure would entitle the customer to terminate such customer agreement, replace the Company or withhold the payment of any material amount to the Company under such customer agreement, then Generate Capital has the right to cause Proton Services Inc., a wholly owned subsidiary of the Company, to replace the Company in performing the maintenance services under such customer agreement. ​ Additionally, $1.75 million was paid to an escrow account related to additional fees due in connection with the Green-Bank Loan if the Company does not meet certain New York State employment and fuel cell deployment targets by March 2021. ​ The amount of escrow expected to be received of $700 thousand was recorded in short-term other assets on the Company’s consolidated balance sheets as of December 31, 2020. During the year ended December 31, 2020, the Company received $250 thousand from escrow related to the New York state employment targets. The Company also received $700 thousand related to the New York State employment targets in March 2021. The Company did not meet the deployment targets and charged-off $800 thousand to interest expense during December, 2020. ​ As of December 31, 2020 the Term Loan Facility requires the principal balance as of each of the following dates not to exceed the following (in thousands): ​ ​ ​ ​ December 31, 2021 ​ 127,317 December 31, 2022 ​ 93,321 December 31, 2023 ​ 62,920 December 31, 2024 ​ 33,692 December 31, 2025 ​ — ​

Convertible Senior Notes

Convertible Senior Notes	12 Months Ended
	Dec. 31, 2020
Convertible Senior Notes.
Convertible Senior Notes	​ 15. Convertible Senior Notes 3.75% Convertible Senior Notes ​ On May 18, 2020, the Company issued $200.0 million in aggregate principal amount of 3.75% Convertible Senior Notes due June 1, 2025, which is referred to herein as the 3.75% Convertible Senior Notes, in a private placement to qualified institutional buyers pursuant to Rule 144A under the Securities Act of 1933, as amended, or the Securities Act. On May 29, 2020, the Company issued an additional $12.5 million in aggregate principal amount of 3.75% Convertible Senior Notes. ​ At issuance in May 2020, the total net proceeds from the 3.75% Convertible Senior Notes were as follows: ​ ​ ​ ​ ​ Amount ​ (in thousands) Principal amount $ 212,463 Less initial purchasers' discount ​ (6,374) Less cost of related capped calls ​ (16,253) Less other issuance costs ​ (617) Net proceeds $ 189,219 ​ The 3.75% Convertible Senior Notes bear interest at a rate of 3.75% per year, payable semi-annually in arrears on June 1 and December 1 of each year, beginning on December 1, 2020. The notes will mature on June 1, 2025, unless earlier converted, redeemed or repurchased in accordance with their terms. ​ The 3.75% Convertible Senior Notes are senior, unsecured obligations of the Company and rank senior in right of payment to any of the Company’s indebtedness that is expressly subordinated in right of payment to the notes, equal in right of payment to any of the Company’s existing and future liabilities that are not so subordinated, including the Company’s $100 million in aggregate principal amount of the 5.5% Convertible Senior Notes due 2023, which is referred to herein as the 5.5% Convertible Senior Notes, effectively junior in right of payment to any of the Company’s secured indebtedness to the extent of the value of the collateral securing such indebtedness, and structurally subordinated to all indebtedness and other liabilities, including trade payables, of its current or future subsidiaries. ​ Holders of the 3.75% Convertible Senior Notes may convert their notes at their option at any time prior to the close of the business day immediately preceding December 1, 2024 in the following circumstances: ​ 1) during any calendar quarter commencing after December 31, 2020, if the last reported sale price of the Company’s common stock exceeds 130% of the conversion price for each of at least 20 trading days (whether or not consecutive) during a period of 30 consecutive trading days ending on, and including, the last trading day of the immediately preceding calendar quarter; ​ 2) during the five business days after any five consecutive trading day period (such five consecutive trading day period, the measurement period) in which the trading price per $1,000 principal amount of the 3.75% Convertible Senior Notes for each trading day of the measurement period was less than 98% of the product of the last reported sale price of the Company’s common stock and the conversion rate on each such trading day; ​ 3) if the Company calls any or all of the 3.75% Convertible Senior Notes for redemption, any such notes that have been called for redemption may be converted at any time prior to the close of business on the second scheduled trading day immediately preceding the redemption date; or ​ 4) upon the occurrence of specified corporate events, as described in the indenture governing the 3.75% Convertible Senior Notes. ​ On or after December 1, 2024, the holders of the 3.75% Convertible Senior Notes may convert all or any portion of their notes at any time prior to the close of business on the second scheduled trading day immediately preceding the maturity date regardless of the foregoing conditions. ​ The initial conversion rate for the 3.75% Convertible Senior Notes is 198.6196 shares of the Company’s common stock per $1,000 principal amount of notes, which is equivalent to an initial conversion price of approximately $5.03 per share of the Company’s common stock, subject to adjustment upon the occurrence of specified events. Upon conversion, the Company will pay or deliver, as applicable, cash, shares of the Company’s common stock or a combination of cash and shares of the Company’s common stock, at the Company’s election. During January and February of 2021, $15.2 million of the 3.75% Convertible Senior Notes have been converted and the Company has issued 3.0 million shares in conjunction with these conversions. ​ In addition, following certain corporate events or following issuance of a notice of redemption, the Company will increase the conversion rate for a holder who elects to convert its notes in connection with such a corporate event or convert its notes called for redemption during the related redemption period in certain circumstances. ​ The 3.75% Convertible Senior Notes will be redeemable, in whole or in part, at the Company’s option at any time, and from time to time, on or after June 5, 2023 and before the 41 st one three ​ If the Company undergoes a “fundamental change” (as defined in the Indenture), holders may require the Company to repurchase their notes for cash all or any portion of their notes at a fundamental change repurchase price equal to 100% of the principal amount of the notes to be repurchased, plus accrued and unpaid interest, to, but excluding, the fundamental change repurchase date. ​ In accounting for the issuance of the 3.75% Convertible Senior Notes, the Company separated the notes into liability and equity components. The initial carrying amount of the liability component of approximately $75.2 million, net of costs incurred, was calculated by measuring the fair value of a similar liability that does not have an associated convertible feature. The carrying amount of the equity component of approximately $130.3 million, net of costs incurred, representing the conversion option, was determined by deducting the fair value of the liability component from the par value of the 3.75% Convertible Senior Notes. The difference between the principal amount of the 3.75% Convertible Senior Notes and the liability component (the debt discount) is amortized to interest expense using the effective interest method over the term of the 3.75% Convertible Senior Notes. The effective interest rate is approximately 29.0%. The equity component of the 3.75% Convertible Senior Notes is included in additional paid-in capital in the consolidated balance sheets and is not remeasured as long as it continues to meet the conditions for equity classification. ​ We incurred transaction costs related to the issuance of the 3.75% Convertible Senior Notes of approximately $7.0 million, consisting of initial purchasers’ discount of approximately $6.4 million and other issuance costs of $0.6 million. In accounting for the transaction costs, we allocated the total amount incurred to the liability and equity components using the same proportions as the proceeds from the 3.75% Convertible Senior Notes. Transaction costs attributable to the liability component were approximately $2.6 million, were recorded as debt issuance cost (presented as contra debt in the consolidated balance sheets) and are being amortized to interest expense over the term of the 3.75% Convertible Senior Notes. The transaction costs attributable to the equity component were approximately $4.4 million and were netted with the equity component in stockholders’ equity. The 3.75% Convertible Senior Notes consisted of the following (in thousands): ​ ​ ​ ​ ​ December 31, ​ 2020 Principal amounts: ​ ​ Principal $ 212,463 Unamortized debt discount (1) ​ (124,655) Unamortized debt issuance costs (1) ​ (2,295) Net carrying amount $ 85,513 Carrying amount of the equity component (2) $ 130,249 ​ 1) Included in the consolidated balance sheets within the 3.75% Convertible Senior Notes, net and amortized over the remaining life of the notes using the effective interest rate method. ​ 3) Included in the consolidated balance sheets within additional paid-in capital, net of the associated income tax benefit of $29.8 million. ​ Based on the closing price of the Company’s common stock of $33.91 on December 31, 2020, the if-converted value of the notes was greater than the principal amount. The estimated fair value of the note at December 31, 2020 was approximately $1.3 billion. Fair value estimation was primarily based on a stock exchange, active trade on December 29, 2020 of the 3.75% Senior Convertible Note. The Company considers this a Level 1 fair value measurement. Refer to Note 4, “Summary of Significant Accounting Policies.” ​ Capped Call ​ In conjunction with the pricing of the 3.75% Convertible Senior Notes, the Company entered into privately negotiated capped call transactions (the “3.75% Notes Capped Call”) with certain counterparties at a price of $16.2 million. The 3.75% Notes Capped Call covers, subject to anti-dilution adjustments, the aggregate number of shares of the Company’s common stock that underlie the initial 3.75% Convertible Senior Notes and The net cost incurred in connection with the 3.75% Notes Capped Call has been recorded as a reduction to additional paid-in capital in the consolidated balance sheet. 7.5% Convertible Senior Note In September 2019, the Company issued $40.0 million aggregate principal amount of 7.5% Convertible Senior Note due on January 5, 2023, which is referred to herein as the 7.5% Convertible Senior Note, in exchange for net proceeds of $39.1 million, in a private placement to an accredited investor pursuant to Rule 144A under the Securities Act. There were no required principal payments prior to the maturity of the 7.5% Convertible Senior Note. Upon maturity of the 7.5% Convertible Senior Note, the Company was required to repay 120% of $40.0 million, or $48.0 million. The 7.5% Convertible Senior Note bore interest at 7.5% per year, payable quarterly in arrears on January 5, April 5, July 5 and October 5 of each year beginning on October 5, 2019 and was to mature on January 5, 2023 unless earlier converted or repurchased in accordance with its terms. The 7.5% Convertible Senior Note was unsecured and did not contain any financial covenants or any restrictions on the payment of dividends, or the issuance or repurchase of common stock by the Company. ​ On July 1, 2020, the 7.5% Convertible Senior Note automatically converted into 16.0 million shares of common stock. 5.5% Convertible Senior Notes ​ In March 2018, the Company issued $100 million in aggregate principal amount of the 5.5% Convertible Senior Notes due on March 15, 2023, which is referred to herein as the 5.5% Convertible Senior Notes, in a private placement to qualified institutional buyers pursuant to Rule 144A under the Securities Act. ​ In May 2020, the Company used a portion of the net proceeds from the issuance of the 3.75% Convertible Senior Notes to finance the cash portion of the partial repurchase of the 5.5% Convertible Senior Notes, which consisted of a repurchase of approximately $66.3 million in aggregate principal amount of the 5.5% Convertible Senior Notes in privately-negotiated transactions for aggregate consideration of $128.9 million, consisting of approximately $90.2 million in cash and approximately 9.4 million shares of the Company’s common stock. Of the $128.9 million in aggregate consideration , ​ In accounting for the issuance of the notes, the Company separated the 5.5% Convertible Senior Notes into liability and equity components. The initial carrying amount of the liability component of approximately $58.2 million, net of costs incurred, was calculated by measuring the fair value of a similar liability that does not have an associated convertible feature. The carrying amount of the equity component of approximately $37.7 million, net of costs incurred, representing the conversion option, was determined by deducting the fair value of the liability component from the par value of the 5.5% Convertible Senior Notes. The difference between the principal amount of the 5.5% Convertible Senior Notes and the liability component (the debt discount) is amortized to interest expense using the effective interest method over the term of the 5.5% Convertible Senior Notes. The effective interest rate is approximately 16.0%. The equity component of the 5.5% Convertible Senior Notes is included in additional paid-in capital in the consolidated balance sheets and is not remeasured as long as it continues to meet the conditions for equity classification. ​ We incurred transaction costs related to the issuance of the 5.5% Convertible Senior Notes of approximately $4.1 million, consisting of initial purchasers’ discount of approximately $3.3 million and other issuance costs of $0.9 million. In accounting for the transaction costs, we allocated the total amount incurred to the liability and equity components using the same proportions as the proceeds from the 5.5% Convertible Senior Notes. Transaction costs attributable to the liability component were approximately $2.4 million, were recorded as debt issuance cost (presented as contra debt in the consolidated balance sheets) and are being amortized to interest expense over the term of the 5.5% Convertible Senior Notes. The transaction costs attributable to the equity component were approximately $1.7 million and were netted with the equity component in stockholders’ equity. The 5.5% Convertible Senior Notes consisted of the following (in thousands): ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ December 31, ​ December 31, ​ 2020 ​ ​ 2019 Principal amounts: ​ ​ ​ ​ ​ Principal $ 160 ​ $ 100,000 Unamortized debt discount (1) ​ (32) ​ ​ (27,818) Unamortized debt issuance costs (1) ​ (1) ​ ​ (1,567) Net carrying amount $ 127 ​ $ 70,615 Carrying amount of the equity component (2) $ — ​ $ 37,702 ​ 1) Included in the consolidated balance sheets within the 5.5% Convertible Senior Notes, net and amortized over the remaining life of the 5.5% Convertible Senior Notes using the effective interest rate method. 2) Included in the consolidated balance sheets within additional paid-in capital, net of $1.7 million in equity issuance costs and associated income tax benefit of $9.2 million, at December 31, 2019. ​ Capped Call ​ In conjunction with the pricing of the 5.5% Convertible Senior Notes, the Company entered into privately negotiated capped call transactions (the “5.5% Notes Capped Call”) with certain counterparties at a price of $16.0 million. The 5.5% Notes Capped Call covers, subject to anti-dilution adjustments, the aggregate number of shares of the Company’s common stock that underlie the initial 5.5% Convertible Senior Notes and is generally expected to reduce the potential dilution to the Company’s common stock upon any conversion of the 5.5% Convertible Senior Notes and/or offset any cash payments the Company is required to make in excess of the principal amount of the converted 5.5% Convertible Senior Notes, as the case may be, with such reduction and/or offset subject to a cap based on the cap price. The cap price of the 5.5% Notes Capped Call is initially $3.82 per share, which represents a premium of 100% over the last then-reported sale price of the Company’s common stock of $1.91 per share on the date of the transaction and is subject to certain adjustments under the terms of the 5.5% Notes Capped Call. The 5.5% Notes Capped Call becomes exercisable if the conversion option is exercised. ​ The net cost incurred in connection with the 5.5% Notes Capped Call has been recorded as a reduction to additional paid-in capital in the consolidated balance sheets. In conjunction with the partial repurchase of the 5.5% Convertible Senior Notes, the Company terminated 100% of the 5.5% Notes Capped Call on June 5, 2020. As a result of the termination, the Company received $24.2 million which was recorded in additional paid-in capital. ​ Common Stock Forward ​ In connection with the issuance of the 5.5% Convertible Senior Notes, the Company also entered into a forward stock purchase transaction, or the Common Stock Forward, pursuant to which the Company agreed to purchase 14,397,906 shares of its common stock for settlement on or about March 15, 2023. In connection with the issuance of the 3.75% Convertible Senior Notes and the partial payoff of the 5.5% Convertible Senior Notes, the Company amended and extended the maturity of the Common Stock Forward to June 1, 2025. The number of shares of common stock that the Company will ultimately repurchase under the Common Stock Forward is subject to customary anti-dilution adjustments. The Common Stock Forward is subject to early settlement or settlement with alternative consideration in the event of certain corporate transactions. ​ The net cost incurred in connection with the Common Stock Forward of $27.5 million has been recorded as an increase in treasury stock in the consolidated balance sheets. The related shares were accounted for as a repurchase of common stock. ​ The book value of the Common Stock Forward is not remeasured. ​ During the fourth quarter of 2020, the Common Stock Forward was partially settled and, as a result, the Company received 4.4 million shares of its common stock.

Stockholders' Equity

Stockholders' Equity	12 Months Ended
	Dec. 31, 2020
Stockholders' Equity
Stockholders' Equity	16. Stockholders’ Equity ​ Preferred Stock ​ The Company has authorized 5.0 million shares of preferred stock, par value $0.01 per share. The Company’s certificate of incorporation provides that shares of preferred stock may be issued from time to time in one or more series. The Company’s Board of Directors is authorized to fix the voting rights, if any, designations, powers, preferences, qualifications, limitations and restrictions thereof, applicable to the shares of each series. ​ The Company has authorized Series A Junior Participating Cumulative Preferred Stock, par value $0.01 per Preferred Stock issued and outstanding. See Note 17, “Redeemable Convertible Preferred Stock,” for a description of the Company’s Series C Preferred Stock and Series E Preferred Stock. ​ Common Stock and Warrants ​ The Company has one class of common stock, par value $.01 per share. Each share of the Company’s common stock is entitled to one vote on all matters submitted to stockholders. ​ In February 2021, the Company completed the previously announced sale of its common stock in connection with a strategic partnership with SK Holdings to accelerate the use of hydrogen as an alternative energy source in Asian markets. The Company sold 54,966,188 shares of its common stock to a subsidiary of SK Holdings at a purchase price of $29.2893 per share, or an aggregate purchase price of approximately $1.6 billion. ​ In January and February 2021, the Company issued and sold in a registered equity offering an aggregate of 32.2 million shares of its common stock at a purchase price of $65.00 per share for net proceeds of approximately $1.8 billion. See Note 23, “Subsequent Events,” for more information. ​ In November 2020, the Company issued and sold in a registered direct offering an aggregate of 43,700,000 shares of its common stock at a purchase price of $22.25 per share for net proceeds of approximately $927.3 million. ​ In August 2020, the Company issued and sold in a registered direct offering an aggregate of 35,276,250 shares of its common stock at a purchase price of $10.25 per share for net proceeds of approximately $344.4 million. ​ In December 2019, the Company issued and sold in a registered public offering an aggregate of 46 million shares of its common stock at a purchase price of $2.75 per share for net proceeds of approximately $120.4 million. ​ In March 2019, the Company issued and sold in a registered direct offering an aggregate of 10 million shares of its common stock at a purchase price of $2.35 per share. The net proceeds to the Company were approximately $23.5 million. ​ There were 458,051,920 and 303,378,515 shares of common stock outstanding as of December 31, 2020 and December 31, 2019, respectively. ​ During 2017, warrants to purchase up to 110,573,392 shares of common stock were issued in connection with transaction agreements with Amazon and Walmart, as discussed in Note 18, “Warrant Transaction Agreements.” At December 31, 2020 and December 31, 2019, 68,380,913 and 26,188,434 of the warrant shares had vested, respectively, and are therefore exercisable. These warrants are measured at fair value at the time of grant or modification and are classified as equity instruments on the consolidated balance sheets. Refer to Note 23, “Subsequent Events.” ​ At Market Issuance Sales Agreement ​ On April 13, 2020, the Company entered into the At Market Issuance Sales Agreement with B. Riley Financial (“B. Riley”) as sales agent, pursuant to which the Company may offer and sell, from time to time through B. Riley, shares of Company common stock having an aggregate offering price of up to $75.0 million. As of the date of this filing, the Company has not issued any shares of common stock pursuant to the At Market Issuance Sales Agreement. ​ Prior to December 31, 2019, the Company entered into a previous At Market Issuance Sales Agreement with B. Riley, which was terminated in the fourth quarter of 2019. Under this At Market Issuance Sales Agreement, for the year ended December 31, 2019, the Company issued 6.3 million shares of common stock, resulting in net proceeds of $14.5 million and for the year ended December 31, 2018, the Company issued 3.8 million shares of common stock, resulting in net proceeds of $7.0 million. ​

Redeemable Convertible Preferre

Redeemable Convertible Preferred Stock	12 Months Ended
	Dec. 31, 2020
Redeemable Convertible Preferred Stock
Redeemable Convertible Preferred Stock	17. Redeemable Convertible Preferred Stock, as restated ​ Series E Preferred Stock ​ In November 2018, the Company issued an aggregate of 35,000 shares of the Company’s Series E Preferred Stock in a private placement to certain accredited investors in reliance on Section 4(a)(2) of the Securities Act. The Company received net proceeds of approximately $30.9 million, after deducting placement agent fees and expenses payable by the Company. The Company is required to redeem the Series E Preferred Stock in thirteen monthly installments in the amount of $2.7 million each from May 2019 through May 2020. The Company had 0 and 500 shares of Series E Preferred Stock outstanding at December 31, 2020 and 2019, respectively. The remaining 500 shares were converted to common stock in January 2020. ​ During 2019, certain conversions of the Series E preferred stock resulted in a deemed dividend of approximately $1.8 million that is reflected on the Company’s consolidated statement of operations as Preferred stock dividends declared, deemed dividends and accretion of discount. ​ Series C Preferred Stock ​ In April 2020, 870 shares of Series C Preferred Stock were converted to 923,819 shares of common stock. In May 2020, the remaining the 1,750 shares of Series C Preferred Stock were converted into 1,858,256 shares of common stock. ​

Warrant Transaction Agreements

Warrant Transaction Agreements	12 Months Ended
	Dec. 31, 2020
Warrant Transaction Agreements
Warrant Transaction Agreements	18. Warrant Transaction Agreements ​ Amazon Transaction Agreement ​ On April 4, 2017, the Company and Amazon entered into a Transaction Agreement (the “Amazon Transaction Agreement”), pursuant to which the Company agreed to issue to Amazon.com NV Investment Holdings LLC, a wholly owned subsidiary of Amazon, a warrant (the “Amazon Warrant”) to acquire up to 55,286,696 shares of the Company’s common stock (the “Amazon Warrant Shares”), subject to certain vesting events described below. The Company and Amazon entered into the Amazon Transaction Agreement in connection with existing commercial agreements between the Company and Amazon with respect to the deployment of the Company’s GenKey fuel cell technology at Amazon distribution centers. The existing commercial agreements contemplate, but do not guarantee, future purchase orders for the Company’s fuel cell technology. The vesting of the Amazon Warrant Shares was conditioned upon payments made by Amazon or its affiliates (directly or indirectly through third parties) pursuant to the existing commercial agreements. ​ Under the terms of the original Amazon Warrant, the first tranche of the 5,819,652 Amazon Warrant Shares vested upon execution of the Amazon Warrant, and the remaining Amazon Warrant Shares vest based on Amazon’s payment of up to $600.0 million to the Company in connection with Amazon’s purchase of goods and services from the Company. The $6.7 million fair value of the first tranche of the Amazon Warrant Shares, was recognized as selling, general and administrative expense upon execution of the Amazon Warrant. ​ Provision for the second and third tranches of Amazon Warrant Shares is recorded as a reduction of revenue, because they represent consideration payable to a customer. ​ The fair value of the second tranche of Amazon Warrant Shares was measured at January 1, 2019, upon adoption of ASU 2019-08. The second tranche of 29,098,260 Amazon Warrant Shares vested in four equal installments, as Amazon or its affiliates, directly or indirectly through third parties, made an aggregate of $50.0 million in payments for goods and services to the Company, up to payments totaling $200.0 million in the aggregate. The last installment of the second tranche vested on November 2, 2020. Revenue reductions of $9.0 million, $4.1 million and $9.8 million associated with the second tranche of Amazon Warrant Shares were recorded in 2020, 2019 and 2018, respectively, under the terms of the original Amazon Warrant. ​ Under the terms of the original Amazon Warrant, the third tranche of 20,368,784 Amazon Warrant Shares vests in eight equal installments, as Amazon or its affiliates, directly or indirectly through third parties, made an aggregate of $50.0 million in payments for goods and services to the Company, up to payments totaling $400.0 million in the aggregate. The measurement date for the third tranche of Amazon Warrant Shares was November 2, 2020, when their exercise price was determined, as discussed further below. The fair value of the third tranche of Amazon Warrant Shares was determined to be $10.57 each. During 2020, revenue reductions of $24.1 million associated with the third tranche Amazon Warrant Shares were recorded under the terms of the original Amazon Warrant, prior to the December 31, 2020 waiver described below. ​ On December 31, 2020, the Company waived the remaining vesting conditions under the Amazon Warrant, which resulted in the immediate vesting of all the third tranche of the Amazon Warrant Shares and recognition of an additional $399.7 million reduction to revenue. ​ The $399.7 million reduction to revenue resulting from the December 31, 2020 waiver was determined based upon a probability assessment of whether the underlying shares would have vested under the terms of the original Amazon Warrant. Based upon the Company’s projections of probable future cash collections from Amazon (i.e., a Type I share based payment modification), a reduction of revenue associated with 5,354,905 Amazon Warrant Shares was recognized at their previously measured November 2, 2020 fair value of $10.57 per warrant. A reduction of revenue associated with the remaining 12,730,490 Amazon Warrant Shares was recognized at their December 31, 2020 fair value of $26.95 each, based upon the Company’s assessment that associated future cash collections from Amazon were not deemed probable (i.e., a Type III share based payment modification). ​ The $399.7 million reduction to revenue was recognized during the year ended December 31, 2020 because the Company concluded such amount was not recoverable from the margins expected from future purchases by Amazon under the Amazon Warrant, and no exclusivity or other rights were conferred to the Company in connection with the December 31, 2020 waiver. Additionally, for the year ended December 31, 2020, the Company recorded a reduction to the provision for warrants of $12.8 million in connection with the release of the service loss accrual. ​ At December 31, 2020 and December 31, 2019, 55,286,696 and 20,368,782 of the Amazon Warrant Shares had vested, respectively. The total amount of provision for common stock warrants recorded as a reduction of revenue for the Amazon Warrant during the years ended December 31, 2020, and 2019 and 2018 was $420.0 million, $4.1 million, and $9.8 million, respectively. ​ The exercise price for the first and second tranches of Amazon Warrant Shares is $1.1893 per share. The exercise price of the third tranche of Amazon Warrant Shares is $13.81 per share, which was determined pursuant to the terms of the Amazon Warrant as an amount equal to ninety percent (90%) of the 30-day volume weighted average share price of the Company’s common stock as of November 2, 2020, the final vesting date of the second tranche of Amazon Warrant Shares. The Amazon Warrant is exercisable through April 4, 2027. The Amazon Warrant provides for net share settlement that, if elected by the holder, will reduce the number of shares issued upon exercise to reflect net settlement of the exercise price. The Amazon Warrant provides for certain adjustments that may be made to the exercise price and the number of shares of common stock issuable upon exercise due to customary anti-dilution provisions based on future events. The Amazon Warrant is classified as an equity instrument. ​ Fair value of the Amazon Warrant at December 31, 2020 and November 2, 2020 was based on the Black Scholes Option Pricing Model, which is based, in part, upon level 3 unobservable inputs for which there is little or no market data, requiring the Company to develop its own assumptions. ​ The Company used the following assumptions for its Amazon Warrant: ​ ​ ​ ​ ​ ​ ​ ​ ​ December 31, 2020 ​ November 2, 2020 Risk-free interest rate ​ 0.58% ​ 0.58% Volatility ​ 75.00% ​ 75.00% Expected average term ​ 6.26 ​ 6.42 Exercise price ​ $13.81 ​ $13.81 Stock price ​ $33.91 ​ $15.47 ​ ​ Walmart Transaction Agreement ​ On July 20, 2017, the Company and Walmart entered into a Transaction Agreement (the “Walmart Transaction Agreement”), pursuant to which the Company agreed to issue to Walmart a warrant (the “Walmart Warrant”) to acquire up to 55,286,696 shares of the Company’s common stock, subject to certain vesting events (the “Walmart Warrant Shares”). The Company and Walmart entered into the Walmart Transaction Agreement in connection with existing commercial agreements between the Company and Walmart with respect to the deployment of the Company’s GenKey fuel cell technology across various Walmart distribution centers. The existing commercial agreements contemplate, but do not guarantee, future purchase orders for the Company’s fuel cell technology. The vesting of the warrant shares conditioned upon payments made by Walmart or its affiliates (directly or indirectly through third parties) pursuant to transactions entered into after January 1, 2017 under existing commercial agreements. ​ The majority of the Walmart Warrant Shares will vest based on Walmart’s payment of up to $600.0 million to the Company in connection with Walmart’s purchase of goods and services from the Company. The first tranche of 5,819,652 Walmart Warrant Shares vested upon the execution of the Walmart Warrant and was fully exercised as of December 31, 2020. Accordingly, $10.9 million, the fair value of the first tranche of Walmart Warrant Shares, was recorded as a provision for common stock warrants and presented as a reduction to revenue on the consolidated statements of operations during 2017. All future provision for common stock warrants is measured based on their grant-date fair value and recorded as a charge against revenue. The second tranche of 29,098,260 Walmart Warrant Shares vests in four installments of 7,274,565 Walmart Warrant Shares each time Walmart or its affiliates, directly or indirectly through third parties, make an aggregate of $50.0 million in payments for goods and services to the Company, up to payments totaling $200.0 million in the aggregate. The exercise price for the first and second tranches of Walmart Warrant Shares is $2.1231 per share. After Walmart has made payments to the Company totaling $200.0 million, the third tranche of 20,368,784 Walmart Warrant Shares will vest in eight installments of 2,546,098 Walmart Warrant Shares each time Walmart or its affiliates, directly or indirectly through third parties, make an aggregate of $50.0 million in payments for goods and services to the Company, up to payments totaling $400.0 million in the aggregate. The exercise price of the third tranche of Walmart Warrant Shares will be an amount per share equal to ninety percent (90%) of the 30-day volume weighted average share price of the common stock as of the final vesting date of the second tranche of Walmart Warrant Shares, provided that, with limited exceptions, the exercise price for the third tranche will be no lower than $1.1893. The Walmart Warrant is exercisable through July 20, 2027. ​ The Walmart Warrant provides for net share settlement that, if elected by the holder, will reduce the number of shares issued upon exercise to reflect net settlement of the exercise price. The Walmart Warrant provides for certain adjustments that may be made to the exercise price and the number of shares of common stock issuable upon exercise due to customary anti-dilution provisions based on future events. The Walmart Warrant is classified as an equity instrument. ​ At December 31, 2020 and December 31, 2019, 13,094,217 and 5,819,652 of the Walmart Warrant Shares had vested, respectively. The total amount of provision for common stock warrants recorded as a reduction of revenue for the Walmart Warrant during the years ended December 31, 2020, 2019 and 2018 was $5.0 million, $2.4 million and $0.4 million, respectively.

Revenue

Revenue	12 Months Ended
	Dec. 31, 2020
Revenue
Revenue	19. Revenue, as restated ​ Disaggregation of revenue ​ The following table provides information about disaggregation of revenue (in thousands): ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Major products/services lines ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Year ended December 31, ​ ​ ​ ​ ​ 2019 ​ 2018 ​ ​ 2020 ​ (as restated) ​ (as restated) Sales of fuel cell systems ​ $ (55,091) ​ $ 130,757 ​ $ 75,029 Sale of hydrogen infrastructure ​ ​ (39,204) ​ ​ 19,163 ​ ​ 32,146 Services performed on fuel cell systems and related infrastructure ​ ​ (9,801) ​ ​ 25,217 ​ ​ 22,002 Power Purchase Agreements ​ ​ 26,620 ​ ​ 25,553 ​ ​ 22,569 Fuel delivered to customers ​ ​ (16,072) ​ ​ 29,099 ​ ​ 22,469 Other ​ ​ 311 ​ ​ 186 ​ ​ — Net revenue ​ $ (93,237) ​ $ 229,975 ​ $ 174,215 ​ Contract balances ​ The following table provides information about receivables, contract assets and contract liabilities from contracts with customers (in thousands): ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ 2020 ​ 2019 Accounts receivable ​ $ 43,041 ​ $ 25,768 Contract assets ​ ​ 18,189 ​ ​ 13,251 Contract liabilities ​ ​ 76,285 ​ ​ 40,743 ​ Contract assets relate to contracts for which revenue is recognized on a straight-line basis, however billings escalate over the life of a contract. Contract assets also include amounts recognized as revenue in advance of billings to customers, which are dependent upon the satisfaction of another performance obligation. These amounts are included in prepaid expenses and other assets on the consolidated balance sheet. ​ The contract liabilities relate to the advance consideration received from customers for services that will be recognized over time (primarily fuel cell and related infrastructure services). Contract liabilities also include advance consideration received from customers prior to delivery of products. These amounts are included within deferred revenue and other liabilities on the consolidated balance sheet. ​ Significant changes in the contract assets and the contract liabilities balances during the period are as follows (in thousands): ​ ​ ​ ​ ​ ​ ​ ​ ​ Contract assets ​ Year ended ​ ​ December 31, 2020 Transferred to receivables from contract assets recognized at the beginning of the period ​ $ (5,483) Revenue recognized and not billed as of the end of the period ​ ​ 10,421 Net change in contract assets ​ $ 4,938 ​ ​ ​ ​ ​ ​ Contract liabilities ​ Year ended ​ ​ December 31, 2020 Increases due to cash received, net of amounts recognized as revenue during the period ​ $ 100,492 Contract liabilities assumed as part of acquisitions ​ ​ 2,350 Revenue recognized that was included in the contract liability balance as of the beginning of the period ​ ​ (67,300) Net change in contract liabilities ​ $ 35,542 ​ Estimated future revenue ​ The following table includes estimated revenue included in the backlog expected to be recognized in the future (sales of fuel cell systems and hydrogen installations are expected to be recognized as revenue within one year; sales services five ​ ​ ​ ​ ​ Estimated future revenue ​ ​ ​ ​ ​ December 31, ​ ​ 2020 Sales of fuel cell systems ​ $ 16,209 Sale of hydrogen installations and other infrastructure ​ ​ 28,282 Services performed on fuel cell systems and related infrastructure ​ ​ 75,467 Power Purchase Agreements ​ ​ 178,450 Fuel delivered to customers ​ ​ 65,704 Other rental income ​ ​ 3,294 Total estimated future revenue ​ $ 367,406 ​ Contract costs ​ Contract costs consists of capitalized commission fees and other expenses related to obtaining or fulfilling a contract. ​ Capitalized contract costs at December 31, 2020 and 2019 were $1.5 million and $0.5, respectively.

Employee Benefit Plans

Employee Benefit Plans	12 Months Ended
	Dec. 31, 2020
Employee Benefit Plans
Employee Benefit Plans	20. Employee Benefit Plans ​ 2011 Stock Option and Incentive Plan ​ On May 12, 2011, the Company’s stockholders approved the 2011 Stock Option and Incentive Plan (the “2011 Plan”). The 2011 Plan provided for the issuance of up to a maximum number of shares of common stock equal to the sum of (i) 1,000,000, plus (ii) the number of shares of common stock underlying any grants pursuant to the 2011 Plan or the Plug Power Inc. 1999 Stock Option and Incentive Plan that are forfeited, canceled, repurchased or are terminated (other than by exercise). The shares may be issued pursuant to stock options, stock appreciation rights, restricted stock awards and certain other equity-based awards granted to employees, directors and consultants of the Company. No grants may be made under the 2011 Plan after May 12, 2021. Through various amendments to the 2011 Plan approved by the Company’s stockholders, the number of shares of the Company’s common stock authorized for issuance under the 2011 Plan has been increased to 42.4 million. For the years ended December 31, 2020, 2019, and 2018, the Company recorded expense of approximately $14.4 million, $8.8 million, and $7.4 million, respectively, in connection with the Third Amended and Restated 2011 Stock Option and Incentive Plan. ​ At December 31, 2020, there were outstanding options to purchase approximately 10.2 million shares of Common Stock and 0.8 million shares available for future awards under the 2011 Plan, including adjustments for other types of share-based awards. Options for employees issued under this plan generally vest in equal annual installments over three years and expire ten years after issuance. Options granted to members of the Board generally vest one year after issuance. To date, options granted under the 2011 Plan have vesting provisions ranging from one ​ Compensation cost associated with employee stock options represented approximately $6.8 million, $6.0 million, and $6.4 million of the total share-based payment expense recorded for the years ended December 31, 2020, 2019, and 2018, respectively. The Company estimates the fair value of stock options using a Black-Scholes valuation model, and the resulting fair value is recorded as compensation cost on a straight-line basis over the option vesting period. Key inputs and assumptions used to estimate the fair value of stock options include the grant price of the award, the expected option term, volatility of the Company’s stock, an appropriate risk-free rate, and the Company’s dividend yield. Estimates of fair value are not intended to predict actual future events or the value ultimately realized by employees who receive equity awards, and subsequent events are not indicative of the reasonableness of the original estimates of fair value made by the Company. The assumptions made for purposes of estimating fair value under the Black-Scholes model for the 3,509,549, 3,221,892 and 2,679,667 options granted during the years ended December 31, 2020, 2019, and 2018, respectively, were as follows: ​ ​ ​ ​ ​ ​ ​ ​ ​ 2020 2019 2018 Expected term of options (years) ​ 6 ​ 6 ​ 6 Risk free interest rate ​ 0.37% - 1.37% ​ 1.52% - 2.53% ​ 2.81% - 2.88% Volatility ​ 64.19% - 68.18% ​ 69.32% - 87.94% ​ 98.31% - 98.89% ​ There was no expected dividend yield for the employee stock options granted. ​ The Company used the simplified method in determining its expected term of all its stock option grants in all periods presented. The simplified method was used because the Company does not believe historical exercise data provides a reasonable basis for the expected term of its grants, due primarily to the limited number of stock option exercises that occurred. The Company expects to cease using the simplified method to determine its expected term for stock option grants in 2021. The estimated stock price volatility was derived from the Company’s actual historic stock prices over the past six years, which represents the Company’s best estimate of expected volatility. ​ A summary of stock option activity for the year December 31, 2020 is as follows (in thousands except share amounts): ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Weighted ​ ​ ​ ​ ​ ​ Weighted ​ Average ​ ​ ​ ​ ​ ​ ​ Average ​ Remaining ​ Aggregate ​ ​ ​ ​ Exercise ​ Contractual ​ Intrinsic ​ ​ Shares ​ Price ​ Terms ​ Value Options outstanding at December 31, 2019 ​ 23,013,590 ​ $ 2.48 ​ 6.6 ​ $ 22,277 Granted ​ 3,509,549 ​ ​ 12.79 ​ — ​ ​ — Exercised ​ (16,159,742) ​ ​ 2.55 ​ — ​ ​ — Forfeited ​ (73,249) ​ ​ 6.32 ​ — ​ ​ — Expired ​ (5,650) ​ ​ 4.78 ​ — ​ ​ — Options outstanding at December 31, 2020 ​ 10,284,498 ​ $ 5.78 ​ 7.8 ​ $ 289,316 Options exercisable at December 31, 2020 ​ 4,084,124 ​ ​ 2.31 ​ 5.8 ​ ​ 129,068 Options unvested at December 31, 2020 ​ 6,200,374 ​ $ 8.07 ​ 9.1 ​ $ 160,248 ​ The weighted average grant-date fair value of options granted during the years ended December 31, 2020, 2019, and 2018 was $7.22, $1.67, and $1.55, respectively. As of December 31, 2020, there was approximately $8.1 million of unrecognized compensation cost related to stock option awards to be recognized over the next three years. The total fair value of stock options that vested during the years ended December 31, 2020 and 2019 was approximately $5.9 million and $6.1 million, respectively. ​ Restricted stock awards generally vest in equal installments over a period of one 2020, 2019, and 2018, respectively. Additionally, for the years ended December 31, 2020, 2019, and 2018, there was $41.5 million, $8.4 million, and $3.9 million respectively, of unrecognized compensation cost related to restricted stock awards to be recognized over the next three years. ​ A summary of restricted stock activity for the year ended December 31, 2020 is as follows (in thousands except share amounts): ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Aggregate ​ ​ ​ ​ Intrinsic ​ ​ ​ Shares ​ Value ​ Unvested restricted stock at December 31, 2019 ​ 4,608,560 ​ $ — ​ Granted ​ 3,227,149 ​ ​ — ​ Vested ​ (1,896,901) ​ ​ — ​ Forfeited ​ (64,166) ​ ​ ​ ​ Unvested restricted stock at December 31, 2020 ​ 5,874,642 ​ $ 199,209 ​ ​ 401(k) Savings & Retirement Plan ​ The Company offers a 401(k) Savings & Retirement Plan to eligible employees meeting certain age and service requirements. This plan permits participants to contribute 100% of their salary, up to the maximum allowable by the Internal Revenue Service regulations. Participants are immediately vested in their voluntary contributions plus actual earnings or less actual losses thereon. Participants are vested in the Company’s matching contribution based on years of service completed. Participants are fully vested upon completion of three years of service. During 2018, the Company began funding its matching contribution in a combination of cash and common stock. Accordingly, the Company has issued 403,474 shares and 841,539 shares of common stock to the Plug Power Inc. 401(k) Savings & Retirement Plan during 2020 and 2019, respectively. ​ The Company’s expense for this plan was approximately $2.6 million, $1.9 million, and $1.8 million for the years ended December 31, 2020, 2019, and 2018, respectively. Non-Employee Director Compensation ​ Each non-employee director is paid an annual retainer for their services, in the form of either cash or stock compensation. The Company granted 36,175, 114,285, and 107,389 shares of stock to non-employee directors as compensation for the years ended December 31, 2020, 2019, and 2018, respectively. All common stock issued is fully vested at the time of issuance and is valued at fair value on the date of issuance. The Company’s share-based compensation expense for this plan was approximately $228 thousand, $243 thousand, and $261 thousand for the years ended December 31, 2020, 2019, and 2018, respectively.

Income Taxes

Income Taxes	12 Months Ended
	Dec. 31, 2020
Income Taxes
Income Taxes	21. Income Taxes, as restated ​ The components of loss before income taxes and the income tax benefit for the years ended December 31, 2020, 2019, and 2018, by jurisdiction, are as follows (in thousands): ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ 2019 ​ 2018 ​ ​ 2020 ​ (as restated) ​ (as restated) ​ ​ U.S. Foreign Total U.S. Foreign Total U.S. Foreign Total Loss before income taxes $ (624,302) $ (2,698) $ (627,000) $ (82,188) $ (1,555) $ (83,743) $ (93,497) $ (1,407) $ (94,903) ​ Income tax benefit ​ ​ 30,845 ​ ​ — ​ ​ 30,845 ​ ​ — ​ ​ — ​ ​ — ​ ​ 9,295 ​ ​ — ​ ​ 9,295 ​ Net loss attributable to the Company $ (593,457) $ (2,698) $ (596,155) $ (82,188) $ (1,555) $ (83,743) $ (84,201) $ (1,407) $ (85,608) ​ ​ The significant components of deferred income tax expense (benefit) for the years ended December 31, 2020, 2019, and 2018, by jurisdiction, are as follows (in thousands): ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ 2019 ​ 2018 ​ ​ ​ 2020 ​ (as restated) ​ (as restated) ​ ​ U.S. Foreign Total U.S. Foreign Total U.S. Foreign Total ​ Deferred tax (benefit) expense ​ $ (31,408) ​ $ (67) ​ $ (31,475) ​ $ (10,621) ​ $ (426) ​ $ (11,047) ​ $ (11,745) ​ $ 933 ​ $ (10,812) ​ Net operating loss carryforward generated ​ ​ (51,849) ​ ​ (438) ​ ​ (52,287) ​ ​ (5,099) ​ ​ (270) ​ ​ (5,369) ​ ​ (10,321) ​ ​ (665) ​ ​ (10,986) ​ Valuation allowance increase (decrease) ​ ​ 52,412 ​ ​ 505 ​ ​ 52,917 ​ ​ 15,720 ​ ​ 696 ​ ​ 16,416 ​ ​ 12,771 ​ ​ (268) ​ ​ 12,503 ​ Benefit for income taxes ​ $ (30,845) ​ $ — ​ $ (30,845) ​ $ — ​ $ — ​ $ — ​ $ (9,295) ​ $ — ​ $ (9,295) ​ ​ The Company’s effective income tax rate differed from the federal statutory rate as follows: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ 2020 2019 2018 U.S. Federal statutory tax rate ​ (21.0) % (21.0) % (21.0) % Deferred state taxes ​ (2.3) % 1.4 % (1.9) % Common stock warrant liability ​ 13.4 % — % (1.0) % Other, net ​ (3.4) % (0.5) % 0.9 % Change in valuation allowance ​ 8.4 % 20.1 % 13.2 % ​ ​ (4.9) % 0.0 % (9.8) % ​ Deferred income taxes reflect the net tax effects of temporary differences between the carrying amounts of certain assets and liabilities for financial reporting and the amounts used for income tax purposes. Significant components of the Company’s deferred tax assets and liabilities as of December 31, 2020 and 2019 are as follows (in thousands): ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ U.S. ​ Foreign ​ Total ​ ​ 2019 ​ 2019 ​ 2019 ​ ​ 2020 ​ (as restated) ​ 2020 ​ (as restated) ​ 2020 ​ (as restated) Intangible assets ​ $ — ​ $ — ​ $ 1,197 ​ $ 1,197 ​ $ 1,197 ​ $ 1,197 Deferred revenue ​ ​ 16,082 ​ ​ 7,922 ​ ​ 192 ​ ​ 129 ​ ​ 16,274 ​ ​ 8,051 Interest expense ​ ​ 21,183 ​ ​ 10,216 ​ ​ — ​ ​ — ​ ​ 21,183 ​ ​ 10,216 Other reserves and accruals ​ ​ 5,087 ​ ​ 1,504 ​ ​ — ​ ​ — ​ ​ 5,087 ​ ​ 1,504 Tax credit carryforwards ​ ​ 4,360 ​ ​ 2,590 ​ ​ 1,253 ​ ​ 1,253 ​ ​ 5,613 ​ ​ 3,843 Amortization of stock-based compensation ​ ​ 3,900 ​ ​ 9,081 ​ ​ — ​ ​ — ​ ​ 3,900 ​ ​ 9,081 Non-compensatory warrants ​ ​ 5,020 ​ ​ 4,322 ​ ​ — ​ ​ — ​ ​ 5,020 ​ ​ 4,322 Capitalized research & development expenditures ​ ​ 30,870 ​ ​ 22,601 ​ ​ 4,483 ​ ​ 4,483 ​ ​ 35,353 ​ ​ 27,084 Right of use liability (operating leases) ​ ​ 27,715 ​ ​ 22,647 ​ ​ — ​ ​ — ​ ​ 27,715 ​ ​ 22,647 Net operating loss carryforwards ​ ​ 110,978 ​ ​ 54,438 ​ ​ 10,014 ​ ​ 9,576 ​ ​ 120,992 ​ ​ 64,014 Total deferred tax asset ​ ​ 225,195 ​ ​ 135,321 ​ ​ 17,139 ​ ​ 16,638 ​ ​ 242,334 ​ ​ 151,959 Valuation allowance ​ ​ (154,467) ​ ​ (102,055) ​ ​ (17,127) ​ ​ (16,622) ​ ​ (171,594) ​ ​ (118,677) Net deferred tax assets ​ $ 70,728 ​ $ 33,266 ​ $ 12 ​ $ 16 ​ $ 70,740 ​ $ 33,282 Intangible assets ​ ​ (7,360) ​ ​ (15) ​ ​ — ​ ​ — ​ ​ (7,360) ​ ​ (15) Convertible debt ​ ​ (27,420) ​ ​ (6,592) ​ ​ — ​ ​ — ​ ​ (27,420) ​ ​ (6,592) Right of use asset (operating leases) ​ ​ (27,684) ​ ​ (23,040) ​ ​ — ​ ​ — ​ ​ (27,684) ​ ​ (23,040) Other reserves and accruals ​ ​ — ​ ​ — ​ ​ (12) ​ ​ (16) ​ ​ (12) ​ ​ (16) Property, plant and equipment and right of use assets ​ ​ (9,191) ​ ​ (3,619) ​ ​ — ​ ​ — ​ ​ (9,191) ​ ​ (3,619) Deferred tax liability ​ $ (71,655) ​ $ (33,266) ​ $ (12) ​ $ (16) ​ $ (71,667) ​ $ (33,282) Net ​ $ (927) ​ $ — ​ $ — ​ $ — ​ $ (927) ​ $ — ​ The Company has recorded a valuation allowance, as a result of uncertainties related to the realization of its net deferred tax asset, at December 31, 2020 and 2019 of approximately $171.6 million and $118.7 million, respectively. A reconciliation of the current year change in valuation allowance is as follows (in thousands): ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ U.S. Foreign Total Increase in valuation allowance for current year increase in net operating losses ​ $ 51,848 ​ $ ​ ​ $ 51,848 ​ Increase (decrease) in valuation allowance for current year net increase (decrease) in deferred tax assets other than net operating losses ​ ​ (5,742) ​ ​ 133 ​ ​ (5,609) ​ Decrease in valuation allowance as a result of foreign currency fluctuation ​ ​ 6,306 ​ ​ — ​ ​ 6,306 ​ Increase in valuation allowance due to change in tax rates ​ ​ — ​ ​ 372 ​ ​ 372 ​ Net increase in valuation allowance ​ $ 52,412 ​ $ 505 ​ $ 52,917 ​ ​ The deferred tax assets have been offset by a full valuation allowance because it is more likely than not that the tax benefits of the net operating loss carryforwards and other deferred tax assets may not be realized due to cumulative losses. ​ Under Section 382 of the Internal Revenue Code of 1986, as amended (the “Code”), the use of loss carryforwards may be limited if a change in ownership of a company occurs. If it is determined that due to transactions involving the Company’s shares owned by its 5 percent or greater stockholders a change of ownership has occurred under the provisions of Section 382 of the Code, the Company's federal and state NOL carryforwards could be subject to significant Section 382 limitations. ​ ​ Approximately $4.4 million of research credit carryforwards generated after the most recent IRC Section 382 ownership change are included in the Company's deferred tax assets. Due to limitations under IRC Section 382, research credit carryforwards existing prior to the most recent IRC Section 382 ownership change will not be used and are not reflected in the Company's gross deferred tax asset at December 31, 2020. The remaining credit carryforwards will expire during the periods 2033 through 2040. ​ At December 31, 2020, the Company has unused Canadian net operating loss carryforwards of approximately $14.0 million. The net operating loss carryforwards if unused will expire at various dates from 2026 through 2034. At December 31, 2020, the Company has Scientific Research and Experimental Development (“SR&ED”) expenditures of $17.2 million available to offset future taxable income. These SR&ED expenditures have no expiry date. At December 31, 2020, the Company has Canadian ITC credit carryforwards of $1.3 million available to offset future income tax. These credit carryforwards if unused will expire at various dates from 2022 through 2028. ​ At December 31, 2020, the Company has unused French net operating loss carryforwards of approximately $21.3 million. The net operating loss may carryforward indefinitely or until the Company changes its activity. ​ As of December 31, 2020, the Company has no un-repatriated foreign earnings or unrecognized tax benefits. ​ ​ The Company recognized an income tax benefit for the year ended December 31, 2020 of $30.8 million resulting from a source of future taxable income attributable to the net credit to additional paid-in capital of $25.6 million related to the issuance of the 3.75% Convertible Senior Notes, offset by the partial extinguishment of the 5.5% Convertible Senior Notes and $5.2 million of income tax benefit for the year ended December 31, 2020 related to the recognition of net deferred tax liabilities in connection with the Giner ELX acquisition. This resulted in a corresponding reduction in our deferred tax asset valuation allowance. The Company has not changed its overall conclusion with respect to the need for a valuation allowance against its net deferred tax assets, which remain fully reserved.

Commitments and Contingencies

Commitments and Contingencies	12 Months Ended
	Dec. 31, 2020
Commitments and Contingencies
Commitments and Contingencies	22. Commitments and Contingencies, as restated ​ Restricted Cash ​ In connection with certain of the above noted sale/leaseback agreements, cash of $169.0 million was required to be restricted as security as of December 31, 2020, which restricted cash will be released over the lease term. As of December 31, 2020, the Company also had certain letters of credit backed by security deposits totaling $152.4 million that are security for the above noted sale/leaseback agreements. ​ The Company also had letters of credit in the aggregate amount of $0.5 million at December 31, 2020 associated with a finance obligation from the sale/leaseback of its building. We consider cash collateralizing this letter of credit as restricted cash. ​ Litigation ​ Legal matters are defended and handled in the ordinary course of business. Liabilities for loss contingencies arising from claims, assessments, litigation, fines, and penalties and other sources are recorded when it is probable that a liability has been incurred and the amount can be reasonably estimated. Legal costs incurred in connection with loss contingencies are expensed as incurred. The Company has not recorded any accruals related to any legal matters. ​ Concentrations of credit risk ​ Concentrations of credit risk with respect to receivables exist due to the limited number of select customers with whom the Company has initial commercial sales arrangements. To mitigate credit risk, the Company performs appropriate evaluation of a prospective customer’s financial condition. ​ At December 31, 2020, three customers comprised approximately 73.9% of the total accounts receivable balance. At December 31, 2019, two customers comprised approximately 62.6% of the total accounts receivable balance. ​ On December 31, 2020, the Company waived the remaining vesting conditions under the Amazon Warrant, which resulted in a reduction in revenue of $399.7 million, which resulted in negative consolidated revenue of $93.2 million for the year ended December 31, 2020. See Note 18, “Warrant Transaction Agreements,” to the consolidated financial statements for further information. Total revenue in 2020 for this customer was negative $310.1 million. For the year ended December 31, 2020, this customer accounted for (332.4)% of our total consolidated revenues which included a provision for warrant charge of $420.0 million, which was recorded as a reduction of revenue. Additionally, 156.2% of our total consolidated revenues were associated primarily with two other customers. For the year ended December 31, 2019 49.7% of total consolidated revenues were associated primarily with two customers, as restated. For the year ended December 31, 2018 66.8% of total consolidated revenues were associated primarily with two customers, as restated. For purposes of assigning a customer to a sale/leaseback transaction completed with a financial institution, the Company considers the end user of the assets to be the ultimate customer. At December 31, 2020, three customers comprised approximately 73.9% of the total accounts receivable balance. At December 31, 2019, two customers comprised approximately 62.6% of the total accounts receivable balance.

Subsequent Events

Subsequent Events	12 Months Ended
	Dec. 31, 2020
Subsequent Events
Subsequent Events	23. Subsequent Events ​ Capital Raise ​ In January and February 2021, the Company issued and sold in a registered equity offering an aggregate of 32,200,000 shares of its common stock at a purchase price of $65.00 per share for net proceeds of approximately $1.8 billion. 3.75% Convertible Senior Notes ​ During January and February of 2021, $15.2 million of the 3.75% Convertible Senior Notes were converted and the Company has issued 3.0 million shares in conjunction with these conversions. ​ Strategic Investment ​ In February 2021, the Company completed the previously announced sale of its common stock in connection with a strategic partnership with SK Holdings to accelerate the use of hydrogen as an alternative energy source in Asian markets. The Company sold 54,966,188 shares of its common stock to a subsidiary of SK Holdings at a purchase price of $29.2893 per share, or an aggregate purchase price of approximately $1.6 billion. ​

Summary of Significant Accoun_2

Summary of Significant Accounting Policies (Policies)	12 Months Ended
	Dec. 31, 2020
Summary of Significant Accounting Policies
Principles of Consolidation	Principles of Consolidation ​ The consolidated financial statements include the financial statements of the Company and its wholly-owned subsidiaries. All significant intercompany balances and transactions have been eliminated in consolidation. ​
Leases	Leases ​ Leases ​ The Company determines if an arrangement is or contains a lease at contract inception. The Company recognizes a right of use asset and a lease liability at the lease commencement date. For operating leases, the lease liability is initially measured at the present value of the unpaid lease payments at the lease commencement date. For finance leases, the lease liability is initially measured in the same manner and date as for operating leases and is subsequently measured at amortized cost using the effective interest method. ​ Key estimates and judgments include how the Company determines (1) the discount rate it uses to discount the unpaid lease payments to present value, (2) the lease term and (3) the lease payments. ​ ● ASC Topic 842 requires a lessee to discount its unpaid lease payments using the interest rate implicit in the lease or, if that rate cannot be readily determined, its incremental borrowing rate. Generally, the Company cannot determine the interest rate implicit in the lease because it does not have access to the lessor’s estimated residual value or the amount of the lessor’s deferred initial direct costs. Therefore, the Company generally uses its incremental borrowing rate as the discount rate for the lease. The Company’s incremental borrowing rate for a lease is the rate of interest it would have to pay on a collateralized basis to borrow an amount equal to the lease payments under similar terms. Adjustments that considered the Company’s actual borrowing rate, inclusive of securitization, as well as borrowing rates for companies of similar credit quality, were applied in the determination of the incremental borrowing rate. ​ ● The lease term for all of the Company’s leases includes the noncancelable period of the lease, plus any additional periods covered by either a Company option to extend (or not to terminate) the lease that the Company is reasonably certain to exercise, or an option to extend (or not to terminate) the lease controlled by the lessor. ​ ● Lease payments included in the measurement of the lease liability comprise fixed payments, and for certain finance leases, the exercise price of a Company option to purchase the underlying asset if the Company is reasonably certain at lease commencement to exercise the option. ​ The right of use asset is initially measured at cost, which comprises the initial amount of the lease liability adjusted for lease payments made at or before the lease commencement date, plus any initial direct costs incurred less any lease incentives received. For operating leases, the right of use asset is subsequently measured throughout the lease term at the carrying amount of the lease liability, plus initial direct costs, plus (minus) any prepaid (accrued) lease payments, less the unamortized balance of lease incentives received. Lease expense for lease payments is recognized on a straight-line basis over the lease term. ​ For finance leases, the right of use asset is subsequently amortized using the straight-line method from the lease commencement date to the earlier of the end of the useful life of the underlying asset or the end of the lease term unless the lease transfers ownership of the underlying asset to the Company or the Company is reasonably certain to exercise an option to purchase the underlying asset. In those cases, the right of use asset is amortized over the useful life of the underlying asset. Amortization of the right of use asset is recognized and presented separately from interest expense on the lease liability. The Company’s leases do not contain variable lease payments. ​ Right of use assets for operating and finance leases are periodically reviewed for impairment losses. The Company uses the long-lived assets impairment guidance in ASC Subtopic 360-10, Property, Plant, and Equipment – Overall ​ The Company monitors for events or changes in circumstances that require a reassessment of its leases. When a reassessment results in the remeasurement of a lease liability, a corresponding adjustment is made to the carrying amount of the corresponding right of use asset. ​ Operating and finance lease right of use assets are presented separately on the Company’s consolidated balance sheets. The current portions of operating and finance lease liabilities are also presented separately within current liabilities and the long-term portions are presented separately within noncurrent liabilities on the consolidated balance sheets. ​ The Company has elected not to recognize right of use assets and lease liabilities for short-term leases that have a lease term of 12 months or less. The Company recognizes the lease payments associated with its short-term leases as an expense on a straight-line basis over the lease term.
Revenue Recognition	Revenue Recognition ​ The Company enters into contracts that may contain one or a combination of fuel cell systems and infrastructure, installation, maintenance, spare parts, fuel delivery and other support services. Contracts containing fuel cell systems and related infrastructure may be sold directly to customers or provided to customers under a PPA, discussed further below. ​ The Company does not include a right of return on its products other than rights related to standard warranty provisions that permit repair or replacement of defective goods. The Company accrues for anticipated standard warranty costs at the same time that revenue is recognized for the related product, or when circumstances indicate that warranty costs will be incurred, as applicable. Any prepaid amounts would only be refunded to the extent services have not been provided or the fuel cell systems or infrastructure have not been delivered . Revenue is measured based on the transaction price specified in a contract with a customer, subject to the allocation of the transaction price to distinct performance obligations as discussed below. The Company recognizes revenue when it satisfies a performance obligation by transferring a product or service to a customer. ​ Promises to the customer are separated into performance obligations, and are accounted for separately if they are (1) capable of being distinct and (2) distinct in the context of the contract. The Company considers a performance obligation to be distinct if the customer can benefit from the good or service either on its own or together with other resources readily available to the customer and the Company’s promise to transfer the goods or service to the customer is separately identifiable from other promises in the contract. The Company allocates revenue to each distinct performance obligation based on relative standalone selling prices. ​ Payment terms for sales of fuel cells, infrastructure and service to customers are typically 30 to 90 days. Sale/leaseback transactions with financial institutions are invoiced and collected upon transaction closing. Service is prepaid upfront in a majority of the arrangements. The Company does not adjust the transaction price for a significant financing component when the performance obligation is expected to be fulfilled within a year. ​ In 2017, in separate transactions, the Company issued to each of Amazon.com NV Investment Holdings LLC and Walmart warrants to purchase shares of the Company’s common stock. The Company presents the provision for common stock warrants within each revenue-related line item on the consolidated statements of operations. This presentation reflects a discount that those common stock warrants represent, and therefore revenue is net of these non-cash charges. The provision of common stock warrants is allocated to the relevant revenue-related line items based upon the expected mix of the revenue for each respective contract. See Note 18, “Warrant Transaction Agreements,’ for more details. ​ Nature of goods and services ​ The following is a description of principal activities from which the Company generates its revenue. ​ (j) Sales of Fuel Cell Systems and Related Infrastructure ​ Revenue from sales of fuel cell systems and related infrastructure represents sales of our GenDrive units, GenSure stationary backup power units, as well as hydrogen fueling infrastructure. ​ The Company uses a variety of information sources in determining standalone selling prices for fuel cells systems and related infrastructure. For GenDrive fuel cells, given the nascent nature of the Company’s market, the Company considers several inputs, including prices from a limited number of standalone sales as well as the Company’s negotiations with customers. The Company also considers its costs to produce fuel cells as well as comparable list prices in estimating standalone selling prices. The Company uses applicable observable evidence from similar products in the market to determine standalone selling prices for GenSure stationary backup power units and hydrogen fueling infrastructure. The determination of standalone selling prices of the Company’s performance obligations requires significant judgment, including periodic assessment of pricing approaches and available observable evidence in the market. Once relative standalone selling prices are determined, the Company proportionately allocates the transaction price to each performance obligation within the customer arrangement based upon standalone selling price. The allocated transaction price related to fuel cell systems and spare parts is recognized as revenue at a point in time which usually occurs at shipment (and occasionally upon delivery). Revenue on hydrogen infrastructure installations is generally recognized at the point at which transfer of control passes to the customer, which usually occurs upon customer acceptance of the hydrogen infrastructure. In certain instances, control of hydrogen infrastructure installations transfers to the customer over time, and the related revenue is recognized over time as the performance obligation is satisfied. The Company uses an input method to determine the amount of revenue to recognize during each reporting period when such revenue is recognized over time, based on the costs incurred to satisfy the performance obligation. ​ (ii) ​ Revenue from services performed on fuel cell systems and related infrastructure represents revenue earned on our service and maintenance contracts and sales of spare parts. The Company uses an adjusted market assessment approach to determine standalone selling prices for services. This approach considers market conditions and constraints, the Company’s market share, pricing strategies and objectives while maximizing the use of available observable inputs obtained from a limited number of historical standalone service renewal prices and negotiations with customers. The transaction price allocated to services as discussed above is generally recognized as revenue over time on a straight-line basis over the expected service period, as customers simultaneously receive and consume the benefits of routine, recurring maintenance performed throughout the contract period. ​ In substantially all of its commercial transactions, the Company sells extended maintenance contracts that generally provide for a five ​ Extended maintenance contracts generally do not contain customer renewal options. Upon expiration, customers may either negotiate a contract extension or switch to purchasing spare parts and maintaining the fuel cell systems on their own. (iii) ​ Revenue from PPAs primarily represents payments received from customers who make monthly payments to access for the Company’s GenKey solution. ​ Revenue associated with these agreements is recognized on a straight-line basis over the life of the agreements as the customers receive the benefits from the Company’s performance of the services. The customers receive services ratably over the contract term. ​ In conjunction with entering into a PPA with a customer, the Company may enter into transactions with third-party financial institutions in which it receives proceeds from the sale/leaseback transactions of the equipment and the sale of future service revenue. The proceeds from the financial institution are allocated between the sale of equipment and the sale of future service revenue based on the relative standalone selling prices of equipment and service. The proceeds allocated to the sale of future services are recognized as finance obligations. The proceeds allocated to the sale of the equipment are evaluated to determine if the transaction meets the criteria for sale/leaseback accounting. To meet the sale/leaseback criteria, control of the equipment must transfer to the financial institution, which requires among other criteria the leaseback to meet the criteria for an operating lease and the Company must not have a right to repurchase the equipment (unless specific criteria are met). These transactions typically meet the criteria for sale/leaseback accounting and accordingly, the Company recognizes revenue on the sale of the equipment, and separately recognizes the leaseback obligations. ​ The Company recognizes a lease liability for the equipment leaseback obligation based on the present value of the future payments to the financial institutions that are attributed to the equipment leaseback. The discount rate used to determine the lease liability is the Company’s incremental borrowing rate, which is based on an analysis of the interest rates on the Company’s secured borrowings. Adjustments that considered the Company’s actual borrowing rate, inclusive of securitization, as well as borrowing rates for companies of similar credit quality, were applied in the determination of the incremental borrowing rate. The Company also records a right of use asset which is amortized over the term of the leaseback. Rental expense is recognized on a straight-line basis over the life of the leaseback and is included as a cost of PPA revenue on the consolidated statements of operations. ​ Certain of the Company’s transactions with financial institutions do not meet the criteria for sale/leaseback accounting and accordingly, no equipment sale is recognized. All proceeds from these transactions are accounted for as finance obligations. The right of use assets related to these transactions are classified as equipment related to the PPAs and fuel delivered to the customers, net in the consolidated balance sheets. Costs to service the property, depreciation of the assets related to PPAs and fuel delivered to the customers, and other related costs are included in cost of PPA revenue in the consolidated statements of operations. The Company uses its transaction-date incremental borrowing rate as the interest rate for its finance obligations that arise from these transactions. No additional adjustments to the incremental borrowing rate have been deemed necessary for the finance obligations that have resulted from the failed sale/leaseback transactions. ​ In determining whether the sales of fuel cells and other equipment to financial institutions meet the requirements for revenue recognition under sale/leaseback accounting, the Company, as lessee, determines the classification of the lease. The Company estimates certain key inputs to the associated calculations such as: 1) discount rate used to determine the present value of future lease payments, 2) fair value of the fuel cells and equipment, and 3) useful life of the underlying asset(s): ​ ● ASC Topic 842 requires a lessee to discount its future lease payments using the interest rate implicit in the lease or, if that rate cannot be readily determined, its incremental borrowing rate. Generally, the Company cannot determine the interest rate implicit in its leases because it does not have access to the lessor’s estimated residual value or the amount of the lessor’s deferred initial direct costs. Therefore, the Company generally uses its incremental borrowing rate to estimate the discount rate for each lease. Adjustments that considered the Company’s actual borrowing rate, inclusive of securitization, as well as borrowing rates for companies of similar credit quality were applied in the determination of the incremental borrowing rate. ​ ● In order for the lease to be classified as an operating lease, the present value of the future lease payments cannot exceed 90% of the fair value of the leased assets. The Company estimates the fair value of the lease assets using the sales prices. ​ ● In order for a lease to be classified as an operating lease, the lease term cannot exceed 75% (major part) of the estimated useful life of the leased asset. The average estimated useful life of the fuel cells is 10 years , and the average estimated useful life of the hydrogen infrastructure is 20 years . These estimated useful lives are compared to the term of each lease to determine the appropriate lease classification. ​ (iv) ​ Revenue associated with fuel delivered to customers represents the sale of hydrogen to customers that has been purchased by the Company from a third party or generated on site. The stand-alone selling price is not estimated because it is sold separately and therefore directly observable. ​ The Company purchases hydrogen fuel from suppliers in most cases (and sometimes produces hydrogen onsite) and sells to its customers. Revenue and cost of revenue related to this fuel is recorded as dispensed and is included in the respective “Fuel delivered to customers” lines on the consolidated statements of operations. ​ Contract costs ​ The Company expects that incremental commission fees paid to employees as a result of obtaining sales contracts are recoverable and therefore the Company capitalizes them as contract costs. ​ Capitalized commission fees are amortized on a straight-line basis over the period of time which the transfer of goods or services to which the assets relate occur, typically ranging from 5 to 10 years. Amortization of the capitalized commission fees is included in selling, general and administrative expenses. ​ The Company recognizes the incremental costs of obtaining contracts as an expense when incurred if the amortization period of the assets that the Company otherwise would have recognized is one year or less. These costs are included in selling, general and administrative expenses.
Cash Equivalents	Cash Equivalents ​ For purposes of the consolidated statements of cash flows, the Company considers all highly-liquid debt instruments with original maturities of three months or less to be cash equivalents. At December 31, 2020 and 2019, cash equivalents consist of money market accounts. The Company’s cash and cash equivalents are deposited with financial institutions located in the U.S. and may at times exceed insured limits. ​
Common Stock Warrant Accounting	Common Stock Warrant Accounting ​ The Company accounts for common stock warrants as either derivative liabilities or as equity instruments depending on the specific terms of the respective warrant agreements.
Accounts Receivable	​ Accounts Receivable ​ Accounts receivable are stated at the amount billed or billable to customers and are ordinarily due between 30 and 60 days after the issuance of the invoice. Receivables are reserved or written off based on individual credit evaluation and specific circumstances of the customer. The allowance for doubtful accounts and related receivable are reduced when the amount is deemed uncollectible. As of December 31, 2020, and 2019, the allowance for doubtful accounts was $172 thousand and $249 thousand, respectively.
Inventory	Inventory ​ Inventories are valued at the lower of cost, determined on a first-in, first-out basis, and net realizable value. All inventory, including spare parts inventory held at service locations, is not relieved until the customer has received the product, at which time the customer obtains control of the goods.
Property, Plant and Equipment	Property, Plant and Equipment ​ Property, plant and equipment are originally recorded at cost or, if acquired as part of business combination, at fair value. Maintenance and repairs are expensed as costs are incurred. Depreciation on plant and equipment, which includes depreciation on the Company’s primary manufacturing facility, which is accounted for as a financing obligation, is calculated on the straight-line method over the estimated useful lives of the assets. The Company records depreciation and amortization over the following estimated useful lives: ​ ​ ​ ​ Leasehold improvements 5 ‑ 10 years Software, machinery and equipment 1 ‑ 15 years ​ Gains and losses resulting from the sale of property and equipment are recorded in current operations.
Equipment related to PPAs and Fuel Delivered to Customers	Equipment related to PPAs and Fuel Delivered to Customers ​ Equipment related to PPAs and fuel delivered to customers primarily consists of the assets deployed related to PPAs and sites where we deliver fuel to customers. Equipment is depreciated over its useful life. Depreciation expense is recorded on a straight-line basis and is included in cost of revenue for PPAs or cost of fuel delivered to customers, respectively, in the consolidated statements of operations.
Impairment of Long-Lived Assets and PPA Executory Contract Considerations	​ Impairment of Long-Lived Assets and PPA Executory Contract Considerations ​ We evaluate long-lived assets on a quarterly basis to identify events or changes in circumstances (“triggering events”) that indicate the carrying value of certain assets may not be recoverable. Long-lived assets that we evaluate include right of use lease assets, equipment deployed to our PPA’s, assets related primarily to our fuel delivery business and other company owned long-lived assets. ​ Upon the occurrence of a triggering event, long-lived assets are evaluated to determine if the carrying amounts are recoverable. The determination of recoverability is made based upon the estimated undiscounted future net cash flows of assets grouped at the lowest level for which there are identifiable cash flows independent of the cash flows of other groups. For operating assets, the Company has generally determined that the lowest level of identifiable cash flows is based on the customer sites. The assets related primarily to our fuel delivery business are considered to be their own asset group. The cash flows are estimated based on the remaining useful life of the primary asset within the asset group. ​ For assets related to our PPA agreements, we consider all underlying cash inflows related to our contract revenues and cash outflows relating to the costs incurred to service the PPA’s. Our cash flow estimates used in the recoverability test, are based upon, among other things, historical results adjusted to reflect our best estimate of future cash flows and operating performance. Development of future cash flows also requires us to make assumptions and to apply judgment, including timing of future expected cash flows, future cost savings initiatives, and determining recovery values. Changes to our key assumptions related to future performance and other economic and market factors could adversely affect the outcome of our recoverability tests and cause more asset groups to be tested for impairment. ​ If the estimated undiscounted future net cash flows for a given asset group are less than the carrying amount of the related asset group, an impairment loss is determined by comparing the estimated fair value with the carrying amount of the asset group. The impairment loss is then allocated to the long-lived assets in the asset group based on the asset’s relative carrying amounts. However, assets are not impaired below their then estimated fair values. Fair value is generally determined through various valuation techniques, including discounted cash flow models, quoted market values and third-party independent appraisals, as well as year-over-year trends in pricing of our new equipment and overall evaluation of our industry and market, as considered necessary. The Company considers these indicators with certain of its own internal indices and metrics in determining fair value in light of the nascent state of the Company’s market and industry. The estimate of fair value represents our best estimates of these factors and is subject to variability. Changes to our key assumptions related to future performance and other economic and market factors could adversely affect our impairment evaluation. ​ The Company has determined that the assets deployed for certain PPA arrangements are not recoverable based on the undiscounted estimated future cash flows of the asset group. However, the estimated fair value of the assets in the asset group equal or exceed the carrying amount of the assets or otherwise limit the amount of impairment that would have been recognized. The Company has identified the primary source of the losses as the maintenance components of the PPA arrangements and the impact of customer warrant non-cash provisions. As the PPA arrangements are considered to be executory contracts and there is no specific accounting guidance that permits loss recognition for these revenue contracts, the Company has not recognized a provision for the expected future losses under these revenue arrangements. The Company expects that it will recognize future losses for these arrangements as it continues its efforts to reduce costs of delivering the maintenance component of these arrangements.
Extended Maintenance Contracts	Extended Maintenance Contracts ​ On a quarterly basis, we evaluate any potential losses related to our extended maintenance contracts for fuel cell systems and related infrastructure that has been sold. We measure loss accruals at the customer contract level. The expected revenues and expenses for these contracts include all applicable expected costs of providing services over the remaining term of the contracts and the related unearned net revenue. A loss is recognized if the sum of expected costs of providing services under the contract exceeds related unearned net revenue and is recorded as a provision for loss contracts related to service in the consolidated statement of operations. A key component of these estimates is the expected future service costs. In estimating the expected future service costs, the Company considers its current service cost level and applies significant judgment related to expected cost saving initiatives. The expected future cost savings will be primarily dependent upon the success of the Company’s initiatives related to increasing stack life, achieving better economies of scale on service labor, and improvements in design and operations of infrastructure. If the expected cost saving initiatives are not realized, this will increase the costs of providing services and could adversely affect our estimated contract loss accrual. ​ The following table shows the roll forward of balances in the accrual for loss contracts, including changes due to the provision (benefit) for loss accrual, releases to service cost of sales and releases due to the provision for warrants (in thousands): ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ December 31, 2020 ​ December 31, 2019 ​ December 31, 2018 ​ ​ ​ ​ ​ (as restated) ​ ​ (as restated) Beginning Balance $ 3,702 ​ $ 5,345 ​ $ — Provision (benefit) for Loss Accrual ​ 35,473 ​ ​ (394) ​ ​ 5,345 Released to Service Cost of Sales ​ (2,348) ​ ​ (1,249) ​ ​ — Released to Provision for Warrants ​ (12,814) ​ ​ — ​ ​ — Ending Balance $ 24,013 ​ $ 3,702 ​ $ 5,345 ​
Goodwill and indefinite-lived intangible asset	Goodwill and indefinite-lived intangible asset ​ Goodwill is an asset representing the future economic benefits arising from other assets acquired in a business combination that are not individually identified and separately recognized. Goodwill is reviewed for impairment at least annually. The indefinite-lived intangible asset represents in-process research and development for cumulative research and development efforts associated with dry stack electrolyzer technology acquired in connection with the Giner ELX, Inc. acquisition. ​ The Company has the option to perform a qualitative assessment to determine whether it is more-likely-than-not that the fair value of a reporting unit is less than its carrying amount. If this is the case, the quantitative goodwill impairment test is required. If it is more-likely-than-not that the fair value of a reporting unit is greater than its carrying amount, the quantitative goodwill impairment test is not required. ​ The indefinite-lived intangible asset is tested for impairment annually, and more frequently when there is a triggering event. Annually, or when there is a triggering event, the Company first performs a qualitative assessment by evaluating all relevant events and circumstances to determine if it is more likely than not that the indefinite-lived intangible asset is impaired; this includes considering any potential effect on significant inputs to determining the fair value of the indefinite-lived intangible asset. When it is more likely than not that the indefinite-lived intangible asset is impaired, then the Company calculates the fair value of the intangible asset and performs a quantitative impairment test. ​ The Company performs an impairment review of goodwill and the indefinite lived intangible asset on an annual basis at December 1, and when a triggering event is determined to have occurred between annual impairment tests. For the years ended December 31, 2020, 2019, and 2018, the Company performed a qualitative assessment of goodwill for its single reporting unit based on multiple factors including market capitalization and determined that it is not more likely than not that the fair value of its reporting unit is less than the carrying amount. For the year ended December 31, 2020, the Company performed a qualitative assessment of its indefinite lived intangible asset and determined that it is not more likely than not that its fair value is less than the carrying amount.
Intangible Assets	Intangible Assets ​ ​
Fair Value Measurements	Fair Value Measurements ​ The Company records the fair value of assets and liabilities in accordance with ASC 820, Fair Value Measurement ​ In addition to defining fair value, ASC 820 expands the disclosure requirements around fair value and establishes a fair value hierarchy for valuation inputs. The hierarchy prioritizes the inputs into three levels based on the extent to which inputs used in measuring fair value are observable in the market. Each fair value measurement is reported in one of the three levels, which is determined by the lowest level input that is significant to the fair value measurement in its entirety. ​ These levels are: ​ ● Level 1 — quoted prices (unadjusted) in active markets for identical assets or liabilities. ● Level 2 — quoted prices for similar assets and liabilities in active markets or inputs that are observable for the asset or liability, either directly or indirectly through market corroboration, for substantially the full term of the financial instrument. ● Level 3 — unobservable inputs reflecting management’s own assumptions about the inputs used in pricing the asset or liability at fair value. ​ The following table summarizes the carrying amount and estimated fair value of the Company’s financial instruments at December 31, 2020 and 2019 (in thousands): ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Carrying ​ Fair ​ Fair Value Measurements As of December 31, 2020 ​ Amount ​ Value ​ Level 1 ​ Level 2 ​ Level 3 Contingent consideration $ 9,760 $ 9,760 $ — $ — $ 9,760 Convertible senior notes ​ 85,640 ​ 1,272,766 ​ — ​ 1,272,766 ​ — Long-term debt ​ 175,402 ​ 175,402 ​ — ​ — ​ 175,402 Finance obligations ​ 181,553 ​ 181,553 ​ — ​ — ​ 181,553 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Carrying ​ Fair ​ Fair Value Measurements As of December 31, 2019 ​ Amount ​ Value ​ Level 1 ​ Level 2 ​ Level 3 Convertible senior notes $ 110,431 $ 188,775 $ — $ 135,320 $ 53,455 Long-term debt ​ 112,169 ​ 112,169 ​ — ​ — ​ 112,169 Finance obligations ​ 144,089 ​ 144,089 ​ — ​ — ​ 144,089
Equity Instruments	Equity Instruments ​ Common stock warrants that meet certain applicable requirements of ASC Subtopic 815-40, Derivatives and Hedging – Contracts in Entity’s Own Equity ​ Common stock warrants accounted for as equity instruments represent the warrants issued to Amazon and Walmart as discussed in Note 18, “Warrant Transaction Agreements.” The Company adopted FASB ASU 2019-08, Compensation – Stock Compensation (Topic 718) and Revenue from Contracts with Customers (Topic 606), which requires entities to measure and classify share-based payment awards granted to a customer by applying the guidance under Topic 718, as of January 1, 2019. ​ In order to calculate warrant charges, the Company used the Black-Scholes pricing model, which required key inputs including volatility and risk-free interest rate and certain unobservable inputs for which there is little or no market data, requiring the Company to develop its own assumptions. The Company estimated the fair value of unvested warrants, considered to be probable of vesting, at the time. Based on that estimated fair value, the Company determined warrant charges, which are recorded as a reduction of revenue in the consolidated statement of operations.
Redeemable Preferred Stock	Redeemable Preferred Stock ​ We account for redeemable preferred stock as temporary equity in accordance with applicable accounting guidance in FASB ASC Topic 480, Distinguishing Liabilities from Equity ​
Income Taxes	Income Taxes ​ Income taxes are accounted for under the asset and liability method. Deferred tax assets and liabilities are recognized for the future tax consequences attributable to differences between the financial statement carrying amounts of existing assets and liabilities and their respective tax basis and operating loss and tax credit carryforwards. Deferred tax assets and liabilities are measured using enacted tax rates expected to apply to taxable income in the years in which those temporary differences are expected to be recovered or settled. The effect on deferred tax assets and liabilities of a change in tax rates is recognized in the period that includes the enactment date. A valuation allowance is recorded to reduce the carrying amounts of deferred tax assets if it is more likely than not that such assets will not be realized. ​ The Company accounts for uncertain tax positions in accordance with FASB ASC No. 740-10-25, Income Taxes-Overall-Recognition he Company
Foreign Currency Translation	Foreign Currency Translation ​ Foreign currency translation adjustments arising from conversion of the Company’s foreign subsidiary’s financial statements to U.S. dollars for reporting purposes are included in accumulated other comprehensive income in stockholders’ equity on the consolidated balance sheets. Transaction gains and losses resulting from the effect of exchange rate changes on transactions denominated in currencies other than the functional currency of the Company’s operations give rise to realized foreign currency transaction gains and losses, and are included in interest and other income and interest and other expense, respectively, in the consolidated statements of operations. ​
Research and Development.	Research and Development ​ Costs related to research and development activities by the Company are expensed as incurred. Certain research and development expenses have been reclassified for 2018, 2019 and 2020, including interim periods during 2019 and 2020 (see Note 2, “Restatement of Previously Issued Consolidated Financial Statements,” and Note 3 “Unaudited Quarterly Financial data and Restatement of Previously Issued Unaudited Interim Condensed Consolidated Financial Statements).
Stock-Based Compensation	Stock-Based Compensation ​ The Company maintains employee stock-based compensation plans, which are described more fully in Note 20, “Employee Benefit Plans.” ​ Stock-based compensation represents the cost related to stock-based awards granted to employees and directors. The Company measures stock-based compensation cost at grant-date, based on the fair value of the award, and recognizes the cost as expense on a straight-line basis over the option’s requisite service period. ​ The Company estimates the fair value of stock-based awards using a Black-Scholes valuation model. Stock-based compensation expense is recorded in cost of revenue associated with sales of fuel cell systems and related infrastructure, cost of revenue for services performed on fuel cell systems and related infrastructure, research and development expense and selling, general and administrative expenses in the consolidated statements of operations based on the employees’ respective function. ​ The Company records deferred tax assets for awards that result in deductions on the Company’s income tax returns, based upon the amount of compensation cost recognized and the Company's statutory tax rate. Differences between the deferred tax assets recognized for financial reporting purposes and the actual tax deduction reported on the Company's income tax return are recorded in the income statement. No tax benefit or expense for stock-based compensation has been recorded during the years ended December 31, 2020, 2019 and 2018 since the Company remains in a full valuation allowance position.
Convertible Senior Notes	Convertible Senior Notes ​ The Company accounts for its convertible senior notes with separate liability and equity components. The carrying amount of the liability component was initially determined by estimating the fair value of a similar debt instrument that does not have an associated convertible feature. The carrying amount of the equity component representing the conversion option was determined by deducting the estimated fair value of the liability component from the par value of the convertible senior notes, as a whole as of the date of issuance. This difference represents a debt discount that is amortized to interest expense, with a corresponding increase to the carrying amount of the liability component, over the term of the convertible senior notes using the effective interest rate method. The equity component is not remeasured as long as it continues to meet the conditions for equity classification. The Company has allocated issuance costs incurred to the liability and equity components. Issuance costs attributable to the liability component are being amortized to expense over the respective term of the convertible senior notes, and issuance costs attributable to the equity components were netted with the respective equity component in additional paid-in capital.
Use of Estimates	Use of Estimates ​ The consolidated financial statements of the Company have been prepared in conformity with U.S. generally accepted accounting principles, which require management to make estimates and assumptions that affect the reported amounts of assets and liabilities and disclosure of contingent assets and liabilities at the date of the consolidated financial statements and the reported amounts of revenues and expenses during the reporting period. Actual results could differ from those estimates.
Reclassifications	Reclassifications ​ Reclassifications are made, whenever necessary, to prior period financial statements to conform to the current period presentation. ​
Subsequent Events	Subsequent Events ​ The Company evaluates subsequent events at the date of the balance sheet as well as conditions that arise after the balance sheet date but before the consolidated financial statements are issued. The effects of conditions that existed at the balance sheet date are recognized in the consolidated financial statements. Events and conditions arising after the balance sheet date but before the consolidated financial statements are issued are evaluated to determine if disclosure is required to keep the consolidated financial statements from being misleading. To the extent such events and conditions exist, if any, disclosures are made regarding the nature of events and the estimated financial effects for those events and conditions. See Note 23, “Subsequent Events.” ​
Recent Accounting Pronouncements	Recent Accounting Pronouncements ​ Recently Adopted Accounting Pronouncements ​ In June 2016, ASU 2016-13, Financial Instruments – Credit Losses (Topic 326): Measurement of Credit Losses on Financial Instruments, was issued. Also, in April 2019, Accounting Standards Update (ASU) 2019-04, Codification Improvements to Topic 326, Financial Instruments—Credit Losses, Topic 815, Derivatives and Hedging, and Topic 825, Financial Instruments, was issued to make improvements to updates 2016-01, Financial Instruments – Overall (Subtopic 825-10), 2016-13, Financial Instruments – Credit Losses (Topic 326) and 2017-12, Derivatives and Hedging (Topic 815). ASU 2016-13 significantly changes how entities account for credit losses for financial assets and certain other instruments, including trade receivables and contract assets, that are not measured at fair value through net income. The ASU requires a number of changes to the assessment of credit losses, including the utilization of an expected credit loss model, which requires consideration of a broader range of information to estimate expected credit losses over the entire lifetime of the asset, including losses where probability is considered remote. Additionally, the standard requires the estimation of lifetime expected losses for trade receivables and contract assets that are classified as current. The Company adopted these standards effective January 1, 2020 and determined the impact of the standards to be immaterial to the consolidated financial statements. ​ In January 2017, ASU 2017-04, Intangibles – Goodwill and Other (Topic 350), was issued to simplify how an entity is required to test goodwill for impairment by eliminating Step 2 from the goodwill impairment test. Step 2 measures a goodwill impairment loss by comparing the implied fair value of a reporting unit’s goodwill with the carrying amount of that goodwill. The Company adopted this standard effective January 1, 2020 and determined there to be no impact to the consolidated financial statements. ​ Recently Issued and Not Yet Adopted Accounting Pronouncements ​ In August 2020, the FASB issued ASU 2020-06, Debt - Debt with Conversion and Other Options (Subtopic 470-20) and Derivatives and Hedging - Contracts in Entity's Own Equity (Subtopic 815-40): Accounting for Convertible Instruments and Contracts in an Entity's Own Equity (“ASU 2020-06”). This ASU simplifies the complexity associated with applying GAAP for certain financial instruments with characteristics of liabilities and equity. More specifically, the amendments focus on the guidance for convertible instruments and derivative scope exception for contracts in an entity’s own equity. Under ASU 2020-06, the embedded conversion features are no longer separated from the host contract for convertible instruments with conversion features that are not required to be accounted for as derivatives under Topic 815, or that do not result in substantial premiums accounted for as paid-in capital. Consequently, a convertible debt instrument, such as the Company’s 3.75% Convertible Senior Notes, will be accounted for as a single liability measured at its amortized cost, as long as no other features require bifurcation and recognition as derivatives. The new guidance also requires the if-converted method to be applied for all convertible instruments and requires additional disclosures. This guidance is required to be adopted by January 1, 2022, and early adoption is permitted, but no earlier than fiscal years beginning after December 15, 2020. The Company has elected to early adopt this guidance on January 1, 2021 using the modified retrospective method. Under this transition method, the cumulative effect of accounting change removed the impact of recognizing the equity component of the Company’s convertible notes at issuance and the subsequent accounting impact of additional interest expense from debt discount amortization. The cumulative effect of the accounting change upon adoption on January 1, 2021 increased the carrying amount of the convertible notes by $120.7 million, reduced accumulated deficit by $9.5 million and reduced additional paid-in capital by $130.2 million. Future interest expense of the convertible notes will be lower as a result of adoption of this guidance and net loss per share will be computed using the if-converted method for convertible instruments. ​ In March 2020, ASU 2020-04, Reference Rate Reform (Topic 848): Facilitation of the Effects of Reference Rate Reform on Financial Reporting, was issued to provide temporary optional expedients and exceptions to the GAAP guidance on contract modifications and hedge accounting to ease the financial reporting burdens related to the expected market transition from the London Interbank Offered Rate (LIBOR) and other interbank offered rates to alternative reference rates. This update was effective starting March 12, 2020 and the Company may elect to apply the amendments prospectively through December 31, 2022. The adoption of this standard does not have a material impact on the Company’s consolidated financial statements. ​ In March 2020, ASU 2020-03, Codification Improvements to Financial Instruments, was issued to make various codification improvements to financial instruments to make the standards easier to understand and apply by eliminating inconsistencies and providing clarifications. This update will be effective at various dates beginning with date of issuance of this ASU. The adoption of this standard does not have a material impact on the Company’s consolidated financial statements. ​ In December 2019, Accounting Standards Update (ASU) 2019-12,

Restatement of Previously Iss_2

Restatement of Previously Issued Consolidated Financial Statements (Tables)	12 Months Ended
	Dec. 31, 2020
Restatement of Previously Issued Consolidated Financial Statements
Summary of the adjustments between cost of revenue and research and development	​ ​ ​ ​ ​ ​ ​ ​ ​ ​ As of December 31, 2019 ​ As of December 31, 2018 ​ Restatement ​ Restatement ​ ​ Adjustments ​ Adjustments Cost of revenue: ​ ​ ​ ​ ​ ​ Services performed on fuel cell systems and related infrastructure ​ $ 6,986 ​ $ 7,954 Power Purchase Agreements ​ ​ 2,539 ​ ​ 4,264 Sales of fuel cell systems and related infrastructure ​ ​ 1,121 ​ ​ 614 Fuel delivered to customers ​ ​ 8,846 ​ ​ 8,325 Total cost of revenue ​ ​ 19,492 ​ ​ 21,157 ​ ​ ​ ​ ​ ​ ​ Research and development ​ ​ (19,492) ​ ​ (21,157)
Summary impact of restatement adjustments and immaterial error correction to previously reported consolidated financial information	The following tables present the effect of the Restatement Items, as well as other adjustments, on the Company’s consolidated balance sheets for the periods indicated (in thousands, except per share): ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ As of December 31, 2019 ​ ​ ​ ​ As previously ​ Restatement ​ ​ ​ Restatement ​ ​ Reported ​ Adjustments ​ ​ As Restated ​ References Assets ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Current assets: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Cash and cash equivalents ​ $ 139,496 ​ $ — ​ $ 139,496 ​ ​ Restricted cash ​ ​ 54,813 ​ ​ — ​ ​ 54,813 ​ ​ Accounts receivable ​ 25,448 ​ 320 ​ 25,768 ​ d Inventory ​ 72,391 ​ — ​ 72,391 ​ ​ Prepaid expenses and other current assets ​ 21,192 ​ — ​ 21,192 ​ ​ Total current assets ​ 313,340 ​ 320 ​ 313,660 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Restricted cash ​ 175,191 ​ — ​ 175,191 ​ ​ Property, plant, and equipment, net ​ ​ 14,959 ​ — ​ 14,959 ​ ​ Right of use assets related to finance leases, net ​ ​ — ​ ​ 1,714 ​ ​ 1,714 ​ a Right of use assets related to operating leases, net ​ ​ — ​ ​ 63,266 ​ ​ 63,266 ​ a, b Equipment related to power purchase agreements and fuel delivered to customers, net ​ ​ 244,740 ​ (176,971) ​ 67,769 ​ a, b Goodwill ​ ​ 8,842 ​ ​ — ​ ​ 8,842 ​ ​ Intangible assets, net ​ 5,539 ​ — ​ 5,539 ​ ​ Other assets ​ 8,573 ​ — ​ 8,573 ​ ​ Total assets ​ $ 771,184 ​ $ (111,671) ​ $ 659,513 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Liabilities, Redeemable Preferred Stock, and Stockholders’ Equity ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Current liabilities: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Accounts payable ​ $ 40,376 ​ $ — ​ $ 40,376 ​ ​ Accrued expenses ​ 14,213 ​ 196 ​ 14,409 ​ d Deferred revenue ​ 11,691 ​ — ​ 11,691 ​ ​ Operating lease liabilities ​ ​ — ​ ​ 9,428 ​ ​ 9,428 ​ a, b Finance lease liabilities ​ ​ — ​ ​ 226 ​ ​ 226 ​ a Finance obligations ​ ​ 49,507 ​ ​ (24,840) ​ ​ 24,667 ​ a, b Current portion of long-term debt ​ ​ 26,461 ​ ​ — ​ ​ 26,461 ​ ​ Other current liabilities ​ 8,543 ​ (1,839) ​ 6,704 ​ b, c Total current liabilities ​ 150,791 ​ (16,829) ​ 133,962 ​ ​ Deferred revenue ​ 23,369 ​ (199) ​ 23,170 ​ d Operating lease liabilities ​ ​ — ​ ​ 50,937 ​ ​ 50,937 ​ a, b Finance lease liabilities ​ ​ — ​ ​ 2,011 ​ ​ 2,011 ​ a Finance obligations ​ 265,228 ​ (145,806) ​ 119,422 ​ a, b Convertible senior notes, net ​ ​ 110,246 ​ ​ 185 ​ ​ 110,431 ​ d Long-term debt ​ ​ 85,708 ​ ​ — ​ ​ 85,708 ​ ​ Other liabilities ​ 13 ​ 2,805 ​ 2,818 ​ c Total liabilities ​ 635,355 ​ (106,896) ​ 528,459 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Redeemable preferred stock: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Series C redeemable convertible preferred stock, $0.01 par value per share (aggregate involuntary liquidation preference $16,664 ); 10,431 shares authorized; Issued and outstanding : 2,620 at December 31, 2019 ​ ​ 709 ​ ​ — ​ ​ 709 ​ ​ Series E convertible preferred stock, $0.01 par value per share; Shares authorized: 35,000 at December 31, 2019; Issued and outstanding : 500 at December 31, 2019 ​ ​ 441 ​ ​ — ​ ​ 441 ​ ​ Stockholders’ equity: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Common stock, $0.01 par value per share; 750,000,000 shares authorized; Issued: 318,637,560 at December 31, 2019 ​ 3,186 ​ — ​ 3,186 ​ ​ Additional paid-in capital ​ 1,507,116 ​ (163) ​ 1,506,953 ​ d Accumulated other comprehensive income ​ 1,400 ​ (112) ​ 1,288 ​ d Accumulated deficit ​ (1,345,807) ​ (4,500) ​ (1,350,307) ​ ​ Less common stock in treasury: 15,259,045 at December 31, 2019 ​ ​ (31,216) ​ ​ — ​ ​ (31,216) ​ ​ Total stockholders’ equity ​ 134,679 ​ (4,775) ​ 129,904 ​ ​ Total liabilities, redeemable preferred stock, and stockholders’ equity ​ $ 771,184 ​ $ (111,671) ​ $ 659,513 ​ ​ ​ As of December 31, 2019 (a) The "as previously reported" balances for equipment related to power purchase agreements and fuel delivered to customers, net (previously captioned leased assets, net) and the current and long-term finance obligations have been reclassified to conform to current period presentations, as follows at December 31, 2019: ● $176.0 million was reclassified from equipment related to power purchase agreements and fuel delivered to customers, net to right of use assets related to operating leases, net; ● $1.7 million was reclassified from equipment related to power purchase agreements and fuel delivered to customers, net to right of use asset related to finance leases, net; ● $25.8 million was reclassified from current finance obligations to current operating lease liabilities; ● $145.5 million was reclassified from non-current finance obligations to non-current operating lease liabilities; ● $226 thousand was reclassified from current finance obligations to current finance lease liabilities, respectively; and ● $2.0 million was reclassified from non-current finance obligations to non-current finance lease liabilities (b) The correction of the misstatement associated with the right of use assets relating to operating leases resulted in the following at December 31, 2019: ● the right of use assets related to operating leases, net had a decrease of $112.7 million; ● equipment related to power purchase agreements and lessor property, net had an increase of $767 thousand; ● current operating lease liabilities had a decrease of $16.4 million; ● non-current operating lease liabilities had a decrease of $94.6 million; ● the current finance obligations had a $1.2 million increase; ● the non-current finance obligation had an increase of $1.7 million; and ● other current liabilities decreased $2.7 million. (c) Loss accrual provision: The correction of this misstatement resulted in an increase of $897 thousand to other current liabilities and an increase of $2.8 million to other long-term liabilities at December 31, 2019. (d) Other adjustments: Immaterial adjustments at December 31, 2019 resulted in an increase to accounts receivable of $320 thousand. An increase to accrued expenses of $196 thousand. A decrease to deferred revenue of $199 thousand. An increase in convertible senior notes, net of $185 thousand, and a decrease of $163 thousand to additional paid in capital and a $112 thousand decrease to accumulated other comprehensive income. ​ The following tables present the effect of the Restatement Items, as well as other adjustments, on the Company’s consolidated statements of operations for the periods indicated (in thousands, except share and per share amounts): ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ For the Year Ended December 31, 2019 ​ ​ ​ ​ As Previously ​ Restatement ​ ​ ​ ​ Restatement ​ ​ Reported ​ Adjustments ​ ​ As Restated References Net revenue: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Sales of fuel cell systems and related infrastructure ​ $ 149,884 ​ $ 36 ​ $ 149,920 ​ d Services performed on fuel cell systems and related infrastructure ​ ​ 25,217 ​ ​ — ​ ​ 25,217 ​ ​ Power Purchase Agreements ​ 25,853 ​ (300) ​ 25,553 ​ d Fuel delivered to customers ​ 29,099 ​ — ​ 29,099 ​ ​ Other ​ ​ 186 ​ ​ — ​ ​ 186 ​ ​ Net revenue ​ ​ 230,239 ​ ​ (264) ​ ​ 229,975 ​ ​ Cost of revenue: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Sales of fuel cell systems and related infrastructure ​ 96,859 ​ 1,056 ​ 97,915 ​ a, d Services performed on fuel cell systems and related infrastructure ​ 28,801 ​ 5,781 ​ 34,582 ​ a, c,d Benefit for loss contracts related to service ​ ​ — ​ ​ (394) ​ ​ (394) ​ c Power Purchase Agreements ​ 40,056 ​ 1,721 ​ 41,777 ​ a, b,d Fuel delivered to customers ​ 36,357 ​ 8,890 ​ 45,247 ​ a, d Other ​ 200 ​ — ​ 200 ​ ​ Total cost of revenue ​ 202,273 ​ ​ 17,054 ​ ​ 219,327 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Gross profit ​ 27,966 ​ ​ (17,318) ​ ​ 10,648 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Operating expenses: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Research and development ​ ​ 33,675 ​ ​ (18,616) ​ ​ 15,059 ​ a,d Selling, general and administrative ​ ​ 44,333 ​ ​ (1,131) ​ ​ 43,202 ​ b,d Total operating expenses ​ ​ 78,008 ​ ​ (19,747) ​ ​ 58,261 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Operating loss ​ ​ (50,042) ​ ​ 2,429 ​ ​ (47,613) ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Interest and other expense, net ​ (35,502) ​ (189) ​ (35,691) ​ b,d Change in fair value of common stock warrant liability ​ 79 ​ — ​ 79 ​ ​ Gain (loss) on extinguishment of debt ​ — ​ (518) ​ (518) ​ d ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Loss before income taxes ​ $ (85,465) ​ $ 1,722 ​ $ (83,743) ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Income tax benefit ​ — ​ — ​ — ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Net loss attributable to the Company ​ $ (85,465) ​ $ 1,722 ​ $ (83,743) ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Preferred stock dividends declared, deemed dividends and accretion of discount ​ (52) ​ (1,760) ​ (1,812) ​ e Net loss attributable to common stockholders ​ $ (85,517) ​ $ (38) ​ $ (85,555) ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Net loss per share: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Basic and diluted ​ $ (0.36) ​ ​ ​ ​ $ (0.36) ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Weighted average number of common stock outstanding ​ 237,152,780 ​ ​ ​ ​ 237,152,780 ​ ​ ​ For the year ended December 31, 2019 (a) Research and development: The correction of this misstatement resulted in a net decrease of $19.5 million to research and development, and an increase of $1.1 million to the cost of revenue of fuel cell systems and related infrastructure, an increase of $7 million to the cost of revenue of services performed on fuel cell systems and related infrastructure, an increase of $2.5 million to the cost of power purchase agreements and an increase in the cost of fuel delivered to customers of $8.9 million at December 31, 2019. (b) Right of use asset: The correction of this misstatement resulted in a net decrease to cost of revenue for power purchase agreements of $747 thousand. An increase to selling, general, and administrative expense of $25 thousand, and an increase to interest and other expense, net of $522 thousand. (c) Loss accrual provision: The correction of this misstatement resulted in a net decrease to cost of revenue for services performed on fuel cell systems and related infrastructure of $1.2 million and a net decrease to the provision for loss contracts related to service of $394 thousand for the period ended December 31, 2019. (d) Other adjustments: Immaterial adjustments for the period ended December 31, 2019 resulted in the following: a net increase of $36 thousand to revenue from sales of fuel cell systems and related infrastructure. A net decrease to revenue from power purchase agreements of $300 thousand. A net decrease of $65 thousand to the cost of revenue for sales of fuel cell systems and related infrastructure. A net increase to the cost of revenue for services performed on fuel cell systems and related infrastructure of $44 thousand. A net decrease to cost of revenue for power purchase agreements of $70 thousand. A net increase of $44 thousand to cost of revenue related to fuel delivered to customers. A net increase to research and development expense of $876 thousand. A net decrease to selling general and administrative expense of $1.1 million, a net increase to interest and other expense, net of $185 thousand and an increase of $518 thousand loss on the extinguisment of debt (which was previously reported as interest and other expense, net of $518 thousand). (e) Series E redeemable convertible preferred stock deemed dividend: The correction of this misstatement resulted in a net increase of $1.8 million to preferred stock dividends declared, deemed dividends and accretion of discount. ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ For the Year Ended December 31, 2018 ​ ​ ​ ​ As Previously ​ Restatement ​ ​ ​ ​ Restatement ​ ​ Reported ​ Adjustments ​ ​ As Restated References Net revenue: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Sales of fuel cell systems and related infrastructure ​ $ 107,292 ​ $ (117) ​ $ 107,175 ​ d Services performed on fuel cell systems and related infrastructure ​ ​ 22,002 ​ ​ — ​ ​ 22,002 ​ ​ Power Purchase Agreements ​ 22,869 ​ (300) ​ 22,569 ​ d Fuel delivered to customers ​ 22,469 ​ — ​ 22,469 ​ ​ Net revenue ​ ​ 174,632 ​ ​ (417) ​ ​ 174,215 ​ ​ Cost of revenue: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Sales of fuel cell systems and related infrastructure ​ 84,439 ​ 766 ​ 85,205 ​ a,d Services performed on fuel cell systems and related infrastructure ​ 23,698 ​ 8,573 ​ 32,271 ​ a, d Provision for loss contracts related to service ​ ​ — ​ ​ 5,345 ​ ​ 5,345 ​ c Power Purchase Agreements ​ 36,161 ​ 5,200 ​ 41,361 ​ a, b Fuel delivered to customers ​ 27,712 ​ 8,325 ​ 36,037 ​ a Total cost of revenue ​ 172,010 ​ ​ 28,209 ​ ​ 200,219 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Gross (loss) profit ​ 2,622 ​ ​ (28,626) ​ ​ (26,004) ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Operating expenses: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Research and development ​ ​ 33,907 ​ ​ (21,157) ​ ​ 12,750 ​ a Selling, general and administrative ​ ​ 38,198 ​ ​ (513) ​ ​ 37,685 ​ d Total operating expenses ​ ​ 72,105 ​ ​ (21,670) ​ ​ 50,435 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Operating loss ​ ​ (69,483) ​ ​ (6,956) ​ ​ (76,439) ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Interest and other expense, net ​ (22,135) ​ (615) ​ (22,750) ​ b Change in fair value of common stock warrant liability ​ 4,286 ​ — ​ 4,286 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Loss before income taxes ​ $ (87,332) ​ $ (7,571) ​ $ (94,903) ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Income tax benefit ​ 9,217 ​ 78 ​ 9,295 ​ d ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Net loss attributable to the Company ​ $ (78,115) ​ $ (7,493) ​ $ (85,608) ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Preferred stock dividends declared, deemed dividends and accretion of discount ​ (52) ​ — ​ (52) ​ ​ Net loss attributable to common stockholders ​ $ (78,167) ​ $ (7,493) ​ $ (85,660) ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Net loss per share: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Basic and diluted ​ $ (0.36) ​ ​ ​ ​ $ (0.39) ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Weighted average number of common stock outstanding ​ 218,882,337 ​ ​ ​ ​ 218,882,337 ​ ​ ​ For the year ended December 31, 2018 (a) Research and development: The correction of this misstatement resulted in a net decrease of $21.2 million to research and development, and an increase of $614 thousand to the cost of sales of fuel cell systems and related infrastructure, an increase of $8.0 million to the cost of services performed on fuel cell systems and related infrastructure, an increase of $4.2 million to the cost of power purchase agreements and an increase in the cost of fuel delivered to customers of $8.3 million at December 31, 2018. (b) Right of use asset: The correction of this misstatement resulted in a net increase to cost of revenue for power purchase agreements of $937 thousand, and an increase to interest and other expense, net of $615 thousand. (c) Loss accrual provision: The correction of this misstatement resulted in a net increase to the provision for loss contracts related to service of $5.3 million for the period ended December 31, 2018. (d) Other adjustments: Immaterial adjustments for the period ended December 31, 2018 resulted in the following: a net decrease of $117 thousand to revenue from sales of fuel cell systems and related infrastructure. A net decrease to revenue from power purchase agreements of $300 thousand. A net increase of $152 thousand to the cost of revenue for sales of fuel cell systems and related infrastructure. A net increase to the cost of revenue for services performed on fuel cell systems and related infrastructure of $619 thousand. A net decrease to selling general and administrative expense of $513 thousand and an increase to the income tax benefit of $78 thousand. ​ The following tables present the effect of the Restatement Items, as well as other adjustments, on the Company’s consolidated statements of comprehensive loss for the periods indicated (in thousands): ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ For the year ended December 31, 2019 ​ For the year ended December 31, 2018 ​ ​ ​ ​ As Previously ​ Cumulative ​ ​ ​ As Previously ​ Cumulative ​ ​ ​ ​ Restatement ​ ​ Reported ​ Adjustments ​ As Restated ​ Reported ​ Adjustments ​ ​ As Restated ​ References ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Net loss attributable to the Company ​ $ (85,465) ​ $ 1,722 ​ $ (83,743) ​ $ (78,115) ​ $ (7,493) ​ $ (85,608) ​ ​ Other comprehensive loss - foreign currency translation adjustment ​ (184) ​ (112) ​ (296) ​ (610) ​ — ​ ​ (610) ​ b Comprehensive loss attributable to the Company ​ $ (85,649) ​ $ 1,610 ​ $ (84,039) ​ $ (78,725) ​ $ (7,493) ​ $ (86,218) ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Preferred stock dividends declared, deemed dividends and accretion of discount ​ ​ (52) ​ ​ (1,760) ​ ​ (1,812) ​ ​ (52) ​ ​ — ​ ​ (52) ​ a Comprehensive loss attributable to common stockholders ​ ​ (85,701) ​ ​ (150) ​ ​ (85,851) ​ ​ (78,777) ​ ​ (7,493) ​ ​ (86,270) ​ ​ ​ For the year ened December 31, 2019 and 2018 (a) Series E convertible preferred stock deemed dividend: The correction of this misstatement resulted in a net decrease of $1.8 million to preferred stock dividends declared, deemed dividends and accretion of discount to the period ended December 31, 2019. (b) Other adjustments: Immaterial adjustment for the period ended December 31, 2019 resulted in a net increase of $112 thousand for the other comprehensive loss related to the foreign currency translation adjustment. ​ The following tables present the effect of the Restatement Items, as well as other adjustments, on the Company’s consolidated statements of stockholders’ equity (deficit) for the periods indicated (in thousands, except share amounts): ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Accumulated ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Additional ​ Other ​ ​ ​ ​ ​ ​ Total ​ ​ ​ ​ Common Stock ​ Paid-in ​ Comprehensive ​ Treasury Stock ​ Accumulated ​ Stockholders’ ​ Restatement ​ Shares Amount Capital Income Shares Amount Deficit Equity (Deficit) References BALANCE - December 31, 2017 (As Previously Reported) 229,073,517 ​ $ 2,291 ​ $ 1,250,899 ​ $ 2,194 587,151 ​ $ (3,102) ​ $ (1,178,636) ​ $ 73,646 ​ ​ Cumulative adjustments — ​ — ​ — ​ — — ​ — ​ (3,417) ​ (3,417) ​ a,b BALANCE - December 31, 2017 (As Restated) ​ 229,073,517 ​ ​ 2,291 ​ ​ 1,250,899 ​ ​ 2,194 ​ 587,151 ​ ​ (3,102) ​ ​ (1,182,053) ​ ​ 70,229 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ BALANCE - December 31, 2018 (As Previously Reported) 234,160,661 ​ $ 2,342 ​ $ 1,289,714 ​ $ 1,584 15,002,663 ​ $ (30,637) ​ $ (1,260,290) ​ $ 2,713 ​ ​ Cumulative adjustments — ​ — ​ (78) ​ — — ​ — ​ (6,223) ​ (6,301) ​ a,b BALANCE - December 31, 2018 (As Restated) ​ 234,160,661 ​ ​ 2,342 ​ ​ 1,289,636 ​ ​ 1,584 ​ 15,002,663 ​ ​ (30,637) ​ ​ (1,266,513) ​ ​ (3,588) ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ BALANCE - December 31, 2019 (As Previously Reported) 318,637,560 ​ $ 3,186 ​ $ 1,507,116 ​ $ 1,400 15,259,045 ​ $ (31,216) ​ $ (1,345,807) ​ $ 134,679 ​ ​ Cumulative adjustments ​ — ​ ​ — ​ ​ (163) ​ ​ (112) ​ — ​ ​ — ​ ​ (4,500) ​ ​ (4,775) ​ a,b BALANCE - December 31, 2019 (As Restated) ​ 318,637,560 ​ $ 3,186 ​ $ 1,506,953 ​ $ 1,288 15,259,045 ​ $ (31,216) ​ $ (1,350,307) ​ $ 129,904 ​ ​ ​ As of December 31, 2019 and 2018 (a) Restatement Items: The correction of material misstatements resulted in a net increase in accumulated deficit of $4.5 million, $6.2 million and $3.4 million as of December 31, 2019, 2018 and 2017, respectively. (b) Other adjustments: Immaterial adjustments resulted in the following: for the period ended December 31, 2019, there was a net increase of $112 thousand for the other comprehensive loss related to the foreign currency translation adjustment and a net decrease of $163 thousand in additional paid-in capital; and for the period ended December 31, 2018, there was a net decrease in additional paid-in capital of $78 thousand. ​ The following tables present the effect of the Restatement Items, as well as other adjustments, on the Company’s consolidated statements of cashflows for the periods indicated (in thousands): ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ For the Year Ended December 31, 2019 ​ ​ ​ As previously ​ Restatement ​ ​ ​ Restatement ​ ​ Reported ​ Adjustments ​ ​ As Restated References Operating Activities ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Net loss attributable to the Company ​ $ (85,465) ​ $ 1,722 ​ $ (83,743) ​ a Adjustments to reconcile net loss to net cash used in operating activities: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Depreciation of long-lived assets ​ ​ 11,989 ​ ​ (51) ​ ​ 11,938 ​ b, d Amortization of intangible assets ​ 698 ​ — ​ ​ 698 ​ ​ Stock-based compensation ​ 10,890 ​ — ​ ​ 10,890 ​ ​ Loss on extinguishment of debt ​ — ​ 518 ​ ​ 518 ​ d Provision for bad debts and other assets ​ 1,981 ​ — ​ ​ 1,981 ​ ​ Amortization of debt issuance costs and discount on convertible senior notes ​ 8,821 ​ 185 ​ ​ 9,006 ​ d Provision for common stock warrants ​ ​ 6,513 ​ — ​ ​ 6,513 ​ ​ Loss on disposal of leased assets ​ ​ 212 ​ ​ — ​ ​ 212 ​ ​ Change in fair value of common stock warrant liability ​ ​ (79) ​ ​ — ​ ​ (79) ​ ​ Benefit on service contracts ​ ​ — ​ ​ (1,643) ​ ​ (1,643) ​ c Changes in operating assets and liabilities that provide (use) cash: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Accounts receivable ​ ​ 10,646 ​ ​ (52) ​ ​ 10,594 ​ d Inventory ​ ​ (24,481) ​ ​ (152) ​ ​ (24,633) ​ d Prepaid expenses, and other assets ​ ​ (8,110) ​ ​ — ​ ​ (8,110) ​ ​ Accounts payable, accrued expenses, and other liabilities ​ 19,879 ​ (2,645) ​ ​ 17,234 ​ b, d Deferred revenue ​ ​ (5,016) ​ ​ 316 ​ ​ (4,700) ​ d Net cash used in operating activities ​ (51,522) ​ (1,802) ​ (53,324) ​ ​ Investing Activities ​ ​ ​ ​ ​ ​ ​ ​ ​ Purchases of property, plant and equipment ​ ​ (5,683) ​ ​ — ​ ​ (5,683) ​ ​ Purchase of intangible assets ​ (2,404) ​ — ​ ​ (2,404) ​ ​ Purchases of equipment related to PPA and equipment related to fuel delivered to customers ​ ​ (6,532) ​ ​ — ​ ​ (6,532) ​ ​ Proceeds from sale of leased assets ​ 375 ​ ​ — ​ ​ 375 ​ ​ Net cash used in investing activities ​ ​ (14,244) ​ — ​ ​ (14,244) ​ ​ Financing Activities ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Proceeds from issuance of preferred stock and warrants, net of transaction costs ​ 14,089 ​ — ​ ​ 14,089 ​ ​ Proceeds from public offerings, net of transaction costs ​ 158,428 ​ (85) ​ ​ 158,343 ​ d Proceeds from exercise of stock options ​ ​ 1,217 ​ ​ — ​ ​ 1,217 ​ ​ Payments for redemption of preferred stock ​ (4,040) ​ — ​ ​ (4,040) ​ ​ Proceeds from issuance of convertible senior notes, net ​ ​ 39,052 ​ ​ — ​ ​ 39,052 ​ ​ Proceeds from borrowing of long-term debt, net of transaction costs ​ ​ 119,186 ​ ​ — ​ ​ 119,186 ​ ​ Principal payments on long-term debt ​ ​ (24,827) ​ ​ (518) ​ ​ (25,345) ​ d Proceeds from finance obligations ​ ​ 83,668 ​ ​ — ​ ​ 83,668 ​ ​ Repayments of finance obligations ​ ​ (61,713) ​ ​ 2,517 ​ ​ (59,196) ​ b Net cash provided by financing activities ​ ​ 325,060 ​ ​ 1,914 ​ ​ 326,974 ​ ​ Effect of exchange rate changes on cash ​ ​ 53 ​ ​ (112) ​ ​ (59) ​ d Increase in cash, cash equivalents and restricted cash ​ ​ 259,347 ​ ​ — ​ ​ 259,347 ​ ​ Cash, cash equivalents, and restricted cash beginning of period ​ ​ 110,153 ​ ​ — ​ ​ 110,153 ​ ​ Cash, cash equivalents, and restricted cash end of period ​ $ 369,500 ​ $ — ​ $ 369,500 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Supplemental disclosure of cash flow information ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Cash paid for interest ​ $ 19,180 ​ $ — ​ ​ 19,180 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Summary of non-cash investing and financing activity ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Recognition of right of use assets ​ $ 127,370 ​ $ (74,446) ​ $ 52,924 ​ b Conversion of preferred stock to common stock ​ ​ 28,392 ​ ​ — ​ ​ 28,392 ​ ​ ​ For the year ended December 31, 2019 (a) Refer to descriptions of the adjustments and their impact on net loss in the Consolidated Statement of Operations sections for the year ended December 31, 2019 above. (b) Right of use asset: The correction of this misstatement resulted in a net decrease to operating cashflows of $2.7 million and a net increase to cash provided by financing activities of $2.5 million for the period ended December 31, 2019. In addition there was a net decrease of $74.4 million to the non-cash investing and financing activity related to the recognition of the right of use asset. (c) Provision for loss contracts related to service: The correction of this misstatement resulted in a net decrease to operating cashflows of $1.6 million for the period ended December 31 2019. (d) Other adjustments: Immaterial adjustments resulted in an net increase to operating cashflows of $906 thousand, a decrease to cash provided by financing activites of $603 thousand and a decrease to effect of exchange rate changes on cash of $112 thousand, for the period ended December 31 2019 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ For the Year Ended December 31, 2018 ​ ​ ​ ​ As previously ​ Restatement ​ ​ ​ Restatement ​ Reported ​ Adjustments ​ ​ As Restated References Operating Activities ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Net loss attributable to the Company ​ $ (78,115) ​ $ (7,493) ​ $ (85,608) ​ a Adjustments to reconcile net loss to net cash used in operating activities: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Depreciation of long-lived assets ​ ​ 11,014 ​ ​ 818 ​ ​ 11,832 ​ b, d Amortization of intangible assets ​ 693 ​ — ​ ​ 693 ​ ​ Stock-based compensation ​ 8,771 ​ — ​ ​ 8,771 ​ ​ Provision for bad debts and other assets ​ 1,626 ​ — ​ ​ 1,626 ​ ​ Amortization of debt issuance costs and discount on convertible senior notes ​ 6,347 ​ — ​ ​ 6,347 ​ ​ Provision for common stock warrants ​ ​ 10,190 ​ — ​ ​ 10,190 ​ ​ Change in fair value of common stock warrant liability ​ (4,286) ​ ​ — ​ ​ (4,286) ​ ​ Income tax benefit ​ ​ (9,217) ​ ​ (78) ​ ​ (9,295) ​ d Loss on service contracts ​ ​ — ​ ​ 5,345 ​ ​ 5,345 ​ c Changes in operating assets and liabilities that provide (use) cash: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Accounts receivable ​ ​ (14,398) ​ ​ (268) ​ ​ (14,666) ​ d Inventory ​ ​ 19,041 ​ ​ 152 ​ ​ 19,193 ​ d Prepaid expenses, and other assets ​ ​ (4,654) ​ ​ — ​ ​ (4,654) ​ ​ Accounts payable, accrued expenses, and other liabilities ​ (10,266) ​ 106 ​ ​ (10,160) ​ d Deferred revenue ​ ​ 5,637 ​ ​ 685 ​ ​ 6,322 ​ d Net cash used in operating activities ​ (57,617) ​ (733) ​ (58,350) ​ ​ Investing Activities ​ ​ ​ ​ ​ ​ ​ ​ ​ Purchases of property, plant and equipment ​ ​ (5,142) ​ ​ — ​ ​ (5,142) ​ ​ Purchases of equipment related to PPA and equipment related to fuel delivered to customers ​ ​ (13,501) ​ ​ — ​ ​ (13,501) ​ ​ Purchase of intangible assets ​ (929) ​ — ​ ​ (929) ​ ​ Net cash used in investing activities ​ ​ (19,572) ​ — ​ ​ (19,572) ​ ​ Financing Activities ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Proceeds from issuance of preferred stock and warrants, net of transaction costs ​ 30,934 ​ — ​ ​ 30,934 ​ ​ Proceeds from public offerings, net of transaction costs ​ 7,195 ​ — ​ ​ 7,195 ​ ​ Proceeds from exercise of stock options ​ ​ 138 ​ ​ — ​ ​ 138 ​ ​ Proceeds from issuance of convertible senior notes, net ​ ​ 95,856 ​ ​ — ​ ​ 95,856 ​ ​ Purchase of capped calls and common stock forward ​ ​ (43,500) ​ ​ — ​ ​ (43,500) ​ ​ Principal payments on long-term debt ​ ​ (16,190) ​ ​ — ​ ​ (16,190) ​ ​ Proceeds from finance obligations ​ ​ 76,175 ​ ​ — ​ ​ 76,175 ​ ​ Repayments of finance obligations ​ ​ (31,264) ​ ​ 733 ​ ​ (30,531) ​ b Net cash provided by financing activities ​ ​ 119,344 ​ ​ 733 ​ ​ 120,077 ​ ​ Effect of exchange rate changes on cash ​ ​ (57) ​ ​ — ​ ​ (57) ​ ​ Increase in cash, cash equivalents and restricted cash ​ ​ 42,098 ​ ​ — ​ ​ 42,098 ​ ​ Cash, cash equivalents, and restricted cash beginning of period ​ ​ 68,055 ​ ​ — ​ ​ 68,055 ​ ​ Cash, cash equivalents, and restricted cash end of period ​ $ 110,153 ​ $ — ​ $ 110,153 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Supplemental disclosure of cash flow information ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Cash paid for interest ​ $ 13,057 ​ $ — ​ ​ 13,057 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Summary of non-cash investing and financing activity ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Recognition of right of use assets ​ $ 79,057 ​ $ (37,378) ​ $ 41,679 ​ b Net transfers between inventory and long-lived assets ​ ​ 18,175 ​ ​ — ​ ​ 18,175 ​ ​ ​ For the year ended December 31, 2018 (a) Refer to descriptions of the adjustments and their impact on net loss in the Consolidated Statement of Operations and Consolidated Balance Sheets sections for the year ended December 31, 2018 above . (b) Right of use asset: The correction of this misstatement resulted in a net increase to operating cashflows of $818 thousand and a net increase to financing cash flows of $733 thousand for the period ended December 31, 2018. In addition, there was a net decrease of $37.4 million to the non-cash investing and financing activity related to the recognition of the right of use asset (c) Provision for loss contracts related to service: The correction of this misstatement resulted in a net increase to operating cashflows of $5.3 million for the period ended December 31 2018. (d) Other adjustments: Immaterial adjustments resulted in an net increase to cash used in operating cash flows of $597 thousand for the period ended December 31 2018 .

Unaudited Quarterly Financial_2

Unaudited Quarterly Financial data and Restatement of Previously Issued Unaudited Interim Condensed Consolidated Financial Statements (Tables)	12 Months Ended
	Dec. 31, 2020
Unaudited Quarterly Financial data and Restatement of Previously Issued Unaudited Interim Condensed Consolidated Financial Statements
Schedule of Quarterly Financial Information	​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Quarters ended ​ ​ As Restated ​ ​ ​ ​ ​ March 31, June 30, September 30, December 31, ​ ​ 2020 ​ 2020 ​ 2020 ​ 2020 Net revenue: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Sales of fuel cell systems and related infrastructure ​ $ 20,468 ​ $ 47,746 ​ $ 83,662 ​ $ (246,171) ​ Services performed on fuel cell systems and related infrastructure ​ 6,521 ​ 6,236 ​ 6,829 ​ (29,387) ​ Power Purchase Agreements ​ 6,421 ​ 6,579 ​ 6,629 ​ 6,991 ​ Fuel delivered to customers ​ 7,333 ​ 7,372 ​ 9,831 ​ (40,608) ​ Other ​ ​ 76 ​ ​ 62 ​ ​ 97 ​ ​ 76 ​ Net revenue ​ ​ 40,819 ​ ​ 67,995 ​ ​ 107,048 ​ ​ (309,099) ​ Gross loss ​ (9,703) ​ (15) ​ (28,584) ​ (431,114) ​ Operating expenses ​ ​ 15,883 ​ ​ 26,517 ​ ​ 25,726 ​ ​ 46,660 ​ Operating loss ​ (25,586) ​ (26,532) ​ (54,310) ​ (477,774) ​ Net loss attributable to common stockholders ​ ​ (37,445) ​ ​ (9,414) ​ ​ (65,217) ​ ​ (484,105) ​ Loss per share: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Basic and Diluted ​ $ (0.12) ​ $ (0.03) ​ $ (0.18) ​ $ (1.35) ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Quarters ended ​ ​ As Restated ​ ​ March 31, June 30, September 30, December 31, ​ ​ 2019 ​ 2019 ​ 2019 ​ 2019 Net revenue: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Sales of fuel cell systems and related infrastructure ​ $ 2,550 ​ $ 38,702 ​ $ 38,883 ​ $ 69,785 ​ Services performed on fuel cell systems and related infrastructure ​ 6,343 ​ 5,341 ​ 6,205 ​ 7,328 ​ Power Purchase Agreements ​ 6,035 ​ 6,334 ​ 6,520 ​ 6,664 ​ Fuel delivered to customers ​ 6,582 ​ 7,089 ​ 7,649 ​ 7,779 ​ Other ​ ​ — ​ ​ — ​ ​ 135 ​ ​ 51 ​ Net revenue ​ ​ 21,510 ​ ​ 57,466 ​ ​ 59,392 ​ ​ 91,607 ​ Gross (loss) profit ​ (7,740) ​ 6,142 ​ 4,500 ​ 7,746 ​ Operating expenses ​ ​ 12,227 ​ ​ 17,221 ​ ​ 13,958 ​ ​ 14,855 ​ Operating loss ​ (19,967) ​ (11,079) ​ (9,458) ​ (7,109) ​ Net loss attributable to common stockholders ​ ​ (30,560) ​ ​ (17,351) ​ ​ (18,366) ​ ​ (19,277) ​ Loss per share: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Basic and Diluted ​ $ (0.14) ​ $ (0.08) ​ $ (0.08) ​ $ (0.07) ​

Summary of Significant Accoun_3

Summary of Significant Accounting Policies (Tables)	12 Months Ended
	Dec. 31, 2020
Summary of Significant Accounting Policies
Schedule of Property Plant and Equipment Useful Lives	​ ​ ​ ​ Leasehold improvements 5 ‑ 10 years Software, machinery and equipment 1 ‑ 15 years
Schedule of accrual for loss contracts	The following table shows the roll forward of balances in the accrual for loss contracts, including changes due to the provision (benefit) for loss accrual, releases to service cost of sales and releases due to the provision for warrants (in thousands): ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ December 31, 2020 ​ December 31, 2019 ​ December 31, 2018 ​ ​ ​ ​ ​ (as restated) ​ ​ (as restated) Beginning Balance $ 3,702 ​ $ 5,345 ​ $ — Provision (benefit) for Loss Accrual ​ 35,473 ​ ​ (394) ​ ​ 5,345 Released to Service Cost of Sales ​ (2,348) ​ ​ (1,249) ​ ​ — Released to Provision for Warrants ​ (12,814) ​ ​ — ​ ​ — Ending Balance $ 24,013 ​ $ 3,702 ​ $ 5,345
Schedule of carrying amount and estimated fair value of financial instruments	The following table summarizes the carrying amount and estimated fair value of the Company’s financial instruments at December 31, 2020 and 2019 (in thousands): ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Carrying ​ Fair ​ Fair Value Measurements As of December 31, 2020 ​ Amount ​ Value ​ Level 1 ​ Level 2 ​ Level 3 Contingent consideration $ 9,760 $ 9,760 $ — $ — $ 9,760 Convertible senior notes ​ 85,640 ​ 1,272,766 ​ — ​ 1,272,766 ​ — Long-term debt ​ 175,402 ​ 175,402 ​ — ​ — ​ 175,402 Finance obligations ​ 181,553 ​ 181,553 ​ — ​ — ​ 181,553 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Carrying ​ Fair ​ Fair Value Measurements As of December 31, 2019 ​ Amount ​ Value ​ Level 1 ​ Level 2 ​ Level 3 Convertible senior notes $ 110,431 $ 188,775 $ — $ 135,320 $ 53,455 Long-term debt ​ 112,169 ​ 112,169 ​ — ​ — ​ 112,169 Finance obligations ​ 144,089 ​ 144,089 ​ — ​ — ​ 144,089

Acquisitions (Tables)

Acquisitions (Tables)	12 Months Ended
	Dec. 31, 2020
Giner ELX, Inc
Schedule of fair value of consideration paid	The fair value of consideration paid by the Company in connection with the Giner ELX acquisition was as follows (in thousands): ​ ​ ​ ​ Cash $ 25,820 Plug Power Stock ​ 19,263 Contingent consideration ​ 7,790 Total consideration $ 52,873 ​
Summary of allocation of the purchase price to the estimated fair value of the net assets acquired	The following table summarizes the final allocation of the purchase price to the estimated fair value of the net assets acquired, excluding goodwill (in thousands): ​ ​ ​ ​ Accounts receivable $ 1,237 Inventory 4,108 Prepaid expenses and other assets ​ 669 Property, plant and equipment ​ 596 Identifiable intangibles ​ 29,930 Accounts payable, accrued expenses and other liabilities ​ (1,621) Deferred revenue ​ (2,350) Deferred tax liability, net ​ (5,889) Total net assets acquired, excluding goodwill $ 26,680
Business combination segment allocation	Goodwill associated with the Giner ELX acquisition was calculated as follows (in thousands): ​ ​ ​ ​ Consideration paid $ 52,873 Less: net assets acquired ​ (26,680) Total goodwill recognized $ 26,193
United Hydrogen Group Inc
Schedule of fair value of consideration paid	The fair value of consideration paid by the Company in connection with the UHG acquisition was as follows (in thousands): ​ ​ ​ ​ Cash $ 19,293 Plug Power Stock ​ 30,410 Contingent consideration ​ 1,110 Total consideration $ 50,813 ​
Summary of allocation of the purchase price to the estimated fair value of the net assets acquired	​ The following table summarizes the final allocation of the purchase price to the estimated fair value of the net assets acquired, excluding goodwill (in thousands): ​ ​ ​ ​ Accounts receivable $ 444 Inventory 89 Prepaid expenses and other assets ​ 1,152 Property, plant and equipment 41,244 Leased property ​ 796 Identifiable intangible asset 2,338 Long-term debt ​ (11,336) Unfavorable customer contract ​ (15,757) Accounts payable, accrued expenses, deferred revenue and finance obligations ​ (4,631) Total net assets acquired, excluding goodwill $ 14,339
Business combination segment allocation	Goodwill associated with the UHG acquisition was calculated as follows (in thousands): ​ ​ ​ ​ Consideration paid $ 50,813 Less: net assets acquired ​ (14,339) Total goodwill recognized $ 36,474

Earnings Per Share (Tables)

Earnings Per Share (Tables)	12 Months Ended
	Dec. 31, 2020
Earnings Per Share
Schedule of components of the calculations of basic and diluted earnings per share:	The following table provides the components of the calculations of basic and diluted earnings per share (in thousands, except share amounts): ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Year ended December 31, ​ ​ ​ ​ ​ ​ 2019 ​ ​ 2018 ​ ​ 2020 (as restated) ​ (as restated) ​ Numerator: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Net loss attributable to common stockholders ​ $ (596,181) ​ $ (85,555) ​ $ (85,660) ​ Denominator: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Weighted average number of common stock outstanding ​ 354,790,106 ​ 237,152,780 ​ 218,882,337 ​ ​
Schedule of potential dilutive common shares	​ ​ ​ ​ ​ ​ ​ ​ ​ At December 31, ​ 2020 2019 2018 Stock options outstanding (1) ​ 10,284,498 23,013,590 21,957,150 Restricted stock outstanding (2) ​ 5,874,642 4,608,560 2,347,347 Common stock warrants (3) ​ 104,753,740 ​ 110,573,392 ​ 115,824,142 Preferred stock (4) ​ — 2,998,527 17,933,591 Convertible Senior Notes (5) ​ 42,256,610 59,133,896 43,630,020 Number of dilutive potential shares of common stock ​ 163,169,490 200,327,965 ​ 201,692,250 ​ (1) During the years ended December 31, 2020, 2019, and 2018, the Company granted 3,509,549 , 3,221,892 , and 2,679,667 stock options, respectively. ​ (2) During the years ended December 31, 2020, 2019, and 2018, the Company granted 3,227,149 , 3,201,892 , and 2,367,347 shares of restricted stock, respectively. ​ (3) In April 2017, the Company issued a warrant to acquire up to 55,286,696 of the Company’s common stock as part of a transaction agreement with Amazon, subject to certain vesting events, as described in Note 18, “Warrant Transaction Agreements.” The warrant had not been exercised as of December 31, 2020. ​ In July 2017, the Company issued a warrant to acquire up to 55,286,696 of the Company’s common stock as part of a transaction agreement with Walmart, subject to certain vesting events, as described in Note 18, “Warrant Transaction Agreements.” The warrant had been exercised with respect to 5,819,652 shares as of December 31, 2020. ​ (4) The preferred stock amount represents the dilutive potential on the shares of common stock as a result of the conversion of the Series C Redeemable Convertible Preferred Stock (Series C Preferred Stock) and Series E Convertible Preferred Stock (Series E Preferred Stock), based on the conversion price of each preferred stock as of December 31 2019, and 2018, respectively. Of the 10,431 shares of Series C Preferred Stock issued on May 16, 2013, all shares had been converted to common stock as of December 31, 2020. On November 1, 2018, the Company issued 35,000 shares of Series E Preferred Stock. As of December 31, 2019, 30,462 shares of the Series E Preferred Stock had been converted to common stock and 4,038 shares were redeemed for cash. All of the remaining Series E Preferred Stock were converted to either common stock or cash, in January 2020 . ​ (5) In March 2018, the Company issued the 5.5% Convertible Senior Notes. In September 2019, the Company issued the $7.5% Convertible Senior Note, which was fully converted into 16.0 million shares on July 1, 2020. In May 2020, the Company issued the 3.5% Convertible Senior Notes and repurchased $66.3 million of the 5.5% Convertible Senior Notes. In the fourth quarter of 2020, $33.5 million of the remaining 5.5% Convertible Senior Notes converted into 14.6 million shares of common stock. As of December 31, 2020, approximately $160 thousand aggregate principal amount of the 5.5% Convertible Senior Notes remained outstanding, all of which was converted in January 2021 .

Inventory (Tables)

Inventory (Tables)	12 Months Ended
	Dec. 31, 2020
Inventory
Schedule of Inventory	Inventory as of December 31, 2020 and 2019 as restated, consists of the following (in thousands): ​ ​ ​ ​ ​ ​ ​ ​ ​ December 31, 2020 December 31, 2019 ​ ​ ​ ​ ​ ​ (as restated) Raw materials and supplies - production locations ​ $ 92,221 ​ $ 48,011 Raw materials and supplies - customer locations ​ ​ 12,405 ​ ​ 9,241 Work-in-process ​ 29,349 ​ 12,529 Finished goods ​ 5,411 ​ 2,610 Inventory ​ $ 139,386 ​ $ 72,391

Property, Plant and Equipment (

Property, Plant and Equipment (Tables)	12 Months Ended
	Dec. 31, 2020
Property, Plant and Equipment
Schedule of Property plant and equipment	Property, plant and equipment at December 31, 2020 and 2019 consists of the following (in thousands): ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ December 31, 2020 ​ December 31, 2019 Land ​ ​ 1,165 ​ ​ — ​ Leasehold improvements ​ $ 1,121 ​ $ 862 ​ Software, machinery and equipment ​ 94,449 ​ 31,514 ​ Property, plant, and equipment ​ 96,735 ​ 32,376 ​ Less: accumulated depreciation ​ (22,186) ​ (17,417) ​ Property, plant, and equipment, net ​ $ 74,549 ​ $ 14,959 ​

Equipment Related to Power Pu_2

Equipment Related to Power Purchase Agreements and Fuel Delivered to Customers, net (Tables)	12 Months Ended
	Dec. 31, 2020
Equipment Related to Power Purchase Agreements and Fuel Delivered to Customers, net
Equipment related to power purchase agreements and fuel delivered to customers, net	Equipment related to power purchase agreements and fuel delivered to customers, net, at December 31, 2020 and 2019 consists of the following (in thousands): ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ December 31, 2019 ​ ​ December 31, 2020 ​ (as restated) Equipment related to power purchase agreements and fuel delivered to customers ​ ​ 92,736 ​ ​ 81,194 Less: accumulated depreciation ​ (16,929) ​ (13,425) Equipment related to power purchase agreements and fuel delivered to customers, net ​ $ 75,807 ​ $ 67,769

Intangible Assets and Goodwill

Intangible Assets and Goodwill (Tables)	12 Months Ended
	Dec. 31, 2020
Intangible Assets and Goodwill
Schedule of Intangible assets	The gross carrying amount and accumulated amortization of the Company’s acquired identifiable intangible assets as of December 31, 2020 are as follows (in thousands): ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Weighted Average ​ Gross Carrying ​ Accumulated ​ ​ ​ ​ ​ Amortization Period ​ Amount ​ Amortization ​ Total Acquired technology 10 years $ 13,697 ​ $ (4,042) ​ $ 9,655 Customer relationships, Non-compete agreements, Backlog & Trademark 6 years ​ 890 ​ ​ (294) ​ ​ 596 In process research and development ​ Indefinite ​ ​ 29,000 ​ ​ — ​ ​ 29,000 ​ ​ ​ ​ $ 43,587 ​ $ (4,336) ​ $ 39,251 ​ The gross carrying amount and accumulated amortization of the Company’s acquired identifiable intangible assets as of December 31, 2019 are as follows (in thousands): ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Weighted Average ​ Gross Carrying ​ Accumulated ​ ​ ​ ​ ​ Amortization Period ​ Amount ​ Amortization ​ Total Acquired technology 9 years ​ $ 8,244 ​ $ (2,815) ​ $ 5,429 Trademark 9 years ​ 320 ​ ​ (210) ​ 110 ​ ​ ​ ​ $ 8,564 ​ $ (3,025) ​ $ 5,539
Schedule of future amortization of intangible assets	Estimated amortization expense for subsequent years was as follows (in thousands): ​ ​ ​ ​ ​ 2021 ​ ​ 1,878 2022 ​ ​ 1,478 2023 ​ ​ 1,478 2024 ​ ​ 1,456 2025 and thereafter ​ ​ 3,961 Total ​ $ 10,251

Accrued Expenses (Tables)

Accrued Expenses (Tables)	12 Months Ended
	Dec. 31, 2020
Accrued Expenses
Schedule of Accrued Expenses	Accrued expenses at December 31, 2020 and 2019 consist of (in thousands): ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ 2019 ​ ​ 2020 ​ (as restated) ​ Accrued payroll and compensation related costs ​ $ 29,167 ​ $ 2,932 ​ Accrued accounts payable ​ ​ 11,750 ​ ​ 7,254 ​ Accrued sales and other taxes ​ ​ 3,665 ​ ​ 905 ​ Accrued interest ​ ​ 649 ​ ​ 2,374 ​ Accrued other ​ ​ 852 ​ ​ 944 ​ Total ​ $ 46,083 ​ $ 14,409 ​

Operating and Finance Lease L_2

Operating and Finance Lease Liabilities (Tables)	12 Months Ended
	Dec. 31, 2020
Operating and Finance Lease Liabilities
Schedule of future minimum lease payments under operating leases	Future minimum lease payments under operating and finance leases (with initial or remaining lease terms in excess of one year) as of December 31, 2020 were as follows (in thousands): ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Finance ​ Total ​ ​ Operating Lease ​ Lease ​ Lease ​ ​ Liability ​ Liability ​ Liabilities 2021 $ 28,536 ​ $ 1,261 ​ $ 29,797 2022 ​ 27,138 ​ 1,234 ​ ​ 28,372 2023 ​ 26,464 ​ 1,210 ​ ​ 27,674 2024 ​ 25,947 ​ 1,293 ​ ​ 27,240 2025 and thereafter ​ 50,362 ​ ​ 1,721 ​ ​ 52,083 Total future minimum payments ​ 158,447 ​ 6,719 ​ ​ 165,166 Less imputed interest ​ (44,509) ​ ​ (1,323) ​ ​ (45,832) Total $ 113,938 ​ $ 5,396 ​ $ 119,334
Schedule of operating leases other information	​ ​ ​ ​ ​ ​ ​ ​ ​ Year ended ​ ​ Year ended ​ ​ December 31, 2020 ​ ​ December 31, 2019 Cash payments (in thousands) $ 22,626 ​ $ 14,055 Weighted average remaining lease term (years) ​ 6.0 ​ ​ 5.0 Weighted average discount rate ​ 11.7% ​ ​ 12.1%
Schedule of finance leases other information	​ ​ ​ ​ ​ ​ ​ ​ ​ Year ended ​ ​ Year ended ​ ​ December 31, 2020 ​ ​ December 31, 2019 Cash payments (in thousands) $ 471 ​ $ 255 Weighted average remaining lease term (years) ​ 5.6 ​ ​ 7.7 Weighted average discount rate ​ 8.2% ​ ​ 8.8%

Finance Obligations (Tables)

Finance Obligations (Tables)	12 Months Ended
	Dec. 31, 2020
Sale Leaseback Transaction [Line Items]
Schedule of finance leases other information	​ ​ ​ ​ ​ ​ ​ ​ ​ Year ended ​ ​ Year ended ​ ​ December 31, 2020 ​ ​ December 31, 2019 Cash payments (in thousands) $ 471 ​ $ 255 Weighted average remaining lease term (years) ​ 5.6 ​ ​ 7.7 Weighted average discount rate ​ 8.2% ​ ​ 8.8%
Finance obligation
Sale Leaseback Transaction [Line Items]
Schedule of future minimum lease payments under finance obligations	Future minimum payments under finance obligations notes above as of December 31, 2020 were as follows (in thousands): ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Total ​ ​ Sale of Future ​ ​ Sale/leaseback Finance ​ ​ revenue - debt ​ ​ financings Obligations 2021 $ 41,670 ​ $ 9,327 ​ $ 50,997 2022 ​ 39,268 ​ ​ 4,975 ​ ​ 44,243 2023 ​ 39,268 ​ ​ 3,149 ​ ​ 42,417 2024 ​ 39,268 ​ ​ 16,154 ​ ​ 55,422 2025 and thereafter ​ 53,385 ​ ​ — ​ ​ 53,385 Total future minimum payments ​ 212,859 ​ ​ 33,605 ​ ​ 246,464 Less imputed interest ​ (55,158) ​ ​ (9,753) ​ ​ (64,911) Total $ 157,701 ​ $ 23,852 ​ $ 181,553
Schedule of finance leases other information	​ ​ ​ ​ ​ ​ ​ ​ ​ Year ended ​ ​ Year ended ​ ​ December 31, 2020 ​ ​ December 31, 2019 Cash payments (in thousands) $ 44,245 ​ $ 76,244 Weighted average remaining term (years) ​ 5.0 ​ ​ 5.3 Weighted average discount rate ​ 11.3% ​ ​ 11.2%

Long-Term Debt (Tables)

Long-Term Debt (Tables)	12 Months Ended
	Dec. 31, 2020
Long-Term Debt
Summary of principal payments of long term debt	As of December 31, 2020 the Term Loan Facility requires the principal balance as of each of the following dates not to exceed the following (in thousands): ​ ​ ​ ​ December 31, 2021 ​ 127,317 December 31, 2022 ​ 93,321 December 31, 2023 ​ 62,920 December 31, 2024 ​ 33,692 December 31, 2025 ​ —

Convertible Senior Notes (Table

Convertible Senior Notes (Tables)	12 Months Ended
	Dec. 31, 2020
3.75% Convertible Senior Notes
Debt Instrument [Line Items]
Schedule of net proceeds from the Convertible Senior Notes	​ ​ ​ ​ ​ Amount ​ (in thousands) Principal amount $ 212,463 Less initial purchasers' discount ​ (6,374) Less cost of related capped calls ​ (16,253) Less other issuance costs ​ (617) Net proceeds $ 189,219

Amazon.com, Inc. Transaction Ag

Amazon.com, Inc. Transaction Agreement (Tables)	3 Months Ended
	Dec. 31, 2020
Warrant Transaction Agreements
Schedule of warranty assumptions	​ ​ ​ ​ ​ ​ ​ ​ December 31, 2020 ​ November 2, 2020 Risk-free interest rate ​ 0.58% ​ 0.58% Volatility ​ 75.00% ​ 75.00% Expected average term ​ 6.26 ​ 6.42 Exercise price ​ $13.81 ​ $13.81 Stock price ​ $33.91 ​ $15.47

Revenue (Tables)

Revenue (Tables)	12 Months Ended
	Dec. 31, 2020
Revenue
Schedule of disaggregation of revenue	The following table provides information about disaggregation of revenue (in thousands): ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Major products/services lines ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Year ended December 31, ​ ​ ​ ​ ​ 2019 ​ 2018 ​ ​ 2020 ​ (as restated) ​ (as restated) Sales of fuel cell systems ​ $ (55,091) ​ $ 130,757 ​ $ 75,029 Sale of hydrogen infrastructure ​ ​ (39,204) ​ ​ 19,163 ​ ​ 32,146 Services performed on fuel cell systems and related infrastructure ​ ​ (9,801) ​ ​ 25,217 ​ ​ 22,002 Power Purchase Agreements ​ ​ 26,620 ​ ​ 25,553 ​ ​ 22,569 Fuel delivered to customers ​ ​ (16,072) ​ ​ 29,099 ​ ​ 22,469 Other ​ ​ 311 ​ ​ 186 ​ ​ — Net revenue ​ $ (93,237) ​ $ 229,975 ​ $ 174,215
Schedule of receivables, contract assets and contract liabilities from contracts with customers	The following table provides information about receivables, contract assets and contract liabilities from contracts with customers (in thousands): ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ 2020 ​ 2019 Accounts receivable ​ $ 43,041 ​ $ 25,768 Contract assets ​ ​ 18,189 ​ ​ 13,251 Contract liabilities ​ ​ 76,285 ​ ​ 40,743
Schedule of changes in contract assets and the contract liabilities	Significant changes in the contract assets and the contract liabilities balances during the period are as follows (in thousands): ​ ​ ​ ​ ​ ​ ​ ​ ​ Contract assets ​ Year ended ​ ​ December 31, 2020 Transferred to receivables from contract assets recognized at the beginning of the period ​ $ (5,483) Revenue recognized and not billed as of the end of the period ​ ​ 10,421 Net change in contract assets ​ $ 4,938 ​ ​ ​ ​ ​ ​ Contract liabilities ​ Year ended ​ ​ December 31, 2020 Increases due to cash received, net of amounts recognized as revenue during the period ​ $ 100,492 Contract liabilities assumed as part of acquisitions ​ ​ 2,350 Revenue recognized that was included in the contract liability balance as of the beginning of the period ​ ​ (67,300) Net change in contract liabilities ​ $ 35,542
Schedule of Estimated future revenue	The following table includes estimated revenue included in the backlog expected to be recognized in the future (sales of fuel cell systems and hydrogen installations are expected to be recognized as revenue within one year; sales services five ​ ​ ​ ​ ​ Estimated future revenue ​ ​ ​ ​ ​ December 31, ​ ​ 2020 Sales of fuel cell systems ​ $ 16,209 Sale of hydrogen installations and other infrastructure ​ ​ 28,282 Services performed on fuel cell systems and related infrastructure ​ ​ 75,467 Power Purchase Agreements ​ ​ 178,450 Fuel delivered to customers ​ ​ 65,704 Other rental income ​ ​ 3,294 Total estimated future revenue ​ $ 367,406

Employee Benefit Plans (Tables)

Employee Benefit Plans (Tables)	12 Months Ended
	Dec. 31, 2020
Employee Benefit Plans
Assumptions made for the purpose of estimating fair value	​ ​ ​ ​ ​ ​ ​ ​ ​ 2020 2019 2018 Expected term of options (years) ​ 6 ​ 6 ​ 6 Risk free interest rate ​ 0.37% - 1.37% ​ 1.52% - 2.53% ​ 2.81% - 2.88% Volatility ​ 64.19% - 68.18% ​ 69.32% - 87.94% ​ 98.31% - 98.89%
Schedule of Share-based Compensation, Stock Options, Activity	​ A summary of stock option activity for the year December 31, 2020 is as follows (in thousands except share amounts): ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Weighted ​ ​ ​ ​ ​ ​ Weighted ​ Average ​ ​ ​ ​ ​ ​ ​ Average ​ Remaining ​ Aggregate ​ ​ ​ ​ Exercise ​ Contractual ​ Intrinsic ​ ​ Shares ​ Price ​ Terms ​ Value Options outstanding at December 31, 2019 ​ 23,013,590 ​ $ 2.48 ​ 6.6 ​ $ 22,277 Granted ​ 3,509,549 ​ ​ 12.79 ​ — ​ ​ — Exercised ​ (16,159,742) ​ ​ 2.55 ​ — ​ ​ — Forfeited ​ (73,249) ​ ​ 6.32 ​ — ​ ​ — Expired ​ (5,650) ​ ​ 4.78 ​ — ​ ​ — Options outstanding at December 31, 2020 ​ 10,284,498 ​ $ 5.78 ​ 7.8 ​ $ 289,316 Options exercisable at December 31, 2020 ​ 4,084,124 ​ ​ 2.31 ​ 5.8 ​ ​ 129,068 Options unvested at December 31, 2020 ​ 6,200,374 ​ $ 8.07 ​ 9.1 ​ $ 160,248
Nonvested Restricted Stock Shares Activity	A summary of restricted stock activity for the year ended December 31, 2020 is as follows (in thousands except share amounts): ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Aggregate ​ ​ ​ ​ Intrinsic ​ ​ ​ Shares ​ Value ​ Unvested restricted stock at December 31, 2019 ​ 4,608,560 ​ $ — ​ Granted ​ 3,227,149 ​ ​ — ​ Vested ​ (1,896,901) ​ ​ — ​ Forfeited ​ (64,166) ​ ​ ​ ​ Unvested restricted stock at December 31, 2020 ​ 5,874,642 ​ $ 199,209 ​

Income Taxes (Tables)

Income Taxes (Tables)	12 Months Ended
	Dec. 31, 2020
Income Taxes
Schedule Components of loss before income taxes and the provision for income taxes	The components of loss before income taxes and the income tax benefit for the years ended December 31, 2020, 2019, and 2018, by jurisdiction, are as follows (in thousands): ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ 2019 ​ 2018 ​ ​ 2020 ​ (as restated) ​ (as restated) ​ ​ U.S. Foreign Total U.S. Foreign Total U.S. Foreign Total Loss before income taxes $ (624,302) $ (2,698) $ (627,000) $ (82,188) $ (1,555) $ (83,743) $ (93,497) $ (1,407) $ (94,903) ​ Income tax benefit ​ ​ 30,845 ​ ​ — ​ ​ 30,845 ​ ​ — ​ ​ — ​ ​ — ​ ​ 9,295 ​ ​ — ​ ​ 9,295 ​ Net loss attributable to the Company $ (593,457) $ (2,698) $ (596,155) $ (82,188) $ (1,555) $ (83,743) $ (84,201) $ (1,407) $ (85,608) ​
Schedule of Significant Components of Deferred Income Tax Expense (Benefit)	The significant components of deferred income tax expense (benefit) for the years ended December 31, 2020, 2019, and 2018, by jurisdiction, are as follows (in thousands): ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ 2019 ​ 2018 ​ ​ ​ 2020 ​ (as restated) ​ (as restated) ​ ​ U.S. Foreign Total U.S. Foreign Total U.S. Foreign Total ​ Deferred tax (benefit) expense ​ $ (31,408) ​ $ (67) ​ $ (31,475) ​ $ (10,621) ​ $ (426) ​ $ (11,047) ​ $ (11,745) ​ $ 933 ​ $ (10,812) ​ Net operating loss carryforward generated ​ ​ (51,849) ​ ​ (438) ​ ​ (52,287) ​ ​ (5,099) ​ ​ (270) ​ ​ (5,369) ​ ​ (10,321) ​ ​ (665) ​ ​ (10,986) ​ Valuation allowance increase (decrease) ​ ​ 52,412 ​ ​ 505 ​ ​ 52,917 ​ ​ 15,720 ​ ​ 696 ​ ​ 16,416 ​ ​ 12,771 ​ ​ (268) ​ ​ 12,503 ​ Benefit for income taxes ​ $ (30,845) ​ $ — ​ $ (30,845) ​ $ — ​ $ — ​ $ — ​ $ (9,295) ​ $ — ​ $ (9,295) ​
Schedule of Effective Income Tax Rate Reconciliation	The Company’s effective income tax rate differed from the federal statutory rate as follows: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ 2020 2019 2018 U.S. Federal statutory tax rate ​ (21.0) % (21.0) % (21.0) % Deferred state taxes ​ (2.3) % 1.4 % (1.9) % Common stock warrant liability ​ 13.4 % — % (1.0) % Other, net ​ (3.4) % (0.5) % 0.9 % Change in valuation allowance ​ 8.4 % 20.1 % 13.2 % ​ ​ (4.9) % 0.0 % (9.8) %
Schedule of Deferred Tax Assets and Liabilities	​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ U.S. ​ Foreign ​ Total ​ ​ 2019 ​ 2019 ​ 2019 ​ ​ 2020 ​ (as restated) ​ 2020 ​ (as restated) ​ 2020 ​ (as restated) Intangible assets ​ $ — ​ $ — ​ $ 1,197 ​ $ 1,197 ​ $ 1,197 ​ $ 1,197 Deferred revenue ​ ​ 16,082 ​ ​ 7,922 ​ ​ 192 ​ ​ 129 ​ ​ 16,274 ​ ​ 8,051 Interest expense ​ ​ 21,183 ​ ​ 10,216 ​ ​ — ​ ​ — ​ ​ 21,183 ​ ​ 10,216 Other reserves and accruals ​ ​ 5,087 ​ ​ 1,504 ​ ​ — ​ ​ — ​ ​ 5,087 ​ ​ 1,504 Tax credit carryforwards ​ ​ 4,360 ​ ​ 2,590 ​ ​ 1,253 ​ ​ 1,253 ​ ​ 5,613 ​ ​ 3,843 Amortization of stock-based compensation ​ ​ 3,900 ​ ​ 9,081 ​ ​ — ​ ​ — ​ ​ 3,900 ​ ​ 9,081 Non-compensatory warrants ​ ​ 5,020 ​ ​ 4,322 ​ ​ — ​ ​ — ​ ​ 5,020 ​ ​ 4,322 Capitalized research & development expenditures ​ ​ 30,870 ​ ​ 22,601 ​ ​ 4,483 ​ ​ 4,483 ​ ​ 35,353 ​ ​ 27,084 Right of use liability (operating leases) ​ ​ 27,715 ​ ​ 22,647 ​ ​ — ​ ​ — ​ ​ 27,715 ​ ​ 22,647 Net operating loss carryforwards ​ ​ 110,978 ​ ​ 54,438 ​ ​ 10,014 ​ ​ 9,576 ​ ​ 120,992 ​ ​ 64,014 Total deferred tax asset ​ ​ 225,195 ​ ​ 135,321 ​ ​ 17,139 ​ ​ 16,638 ​ ​ 242,334 ​ ​ 151,959 Valuation allowance ​ ​ (154,467) ​ ​ (102,055) ​ ​ (17,127) ​ ​ (16,622) ​ ​ (171,594) ​ ​ (118,677) Net deferred tax assets ​ $ 70,728 ​ $ 33,266 ​ $ 12 ​ $ 16 ​ $ 70,740 ​ $ 33,282 Intangible assets ​ ​ (7,360) ​ ​ (15) ​ ​ — ​ ​ — ​ ​ (7,360) ​ ​ (15) Convertible debt ​ ​ (27,420) ​ ​ (6,592) ​ ​ — ​ ​ — ​ ​ (27,420) ​ ​ (6,592) Right of use asset (operating leases) ​ ​ (27,684) ​ ​ (23,040) ​ ​ — ​ ​ — ​ ​ (27,684) ​ ​ (23,040) Other reserves and accruals ​ ​ — ​ ​ — ​ ​ (12) ​ ​ (16) ​ ​ (12) ​ ​ (16) Property, plant and equipment and right of use assets ​ ​ (9,191) ​ ​ (3,619) ​ ​ — ​ ​ — ​ ​ (9,191) ​ ​ (3,619) Deferred tax liability ​ $ (71,655) ​ $ (33,266) ​ $ (12) ​ $ (16) ​ $ (71,667) ​ $ (33,282) Net ​ $ (927) ​ $ — ​ $ — ​ $ — ​ $ (927) ​ $ —
Schedule of Valuation Allowance	​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ U.S. Foreign Total Increase in valuation allowance for current year increase in net operating losses ​ $ 51,848 ​ $ ​ ​ $ 51,848 ​ Increase (decrease) in valuation allowance for current year net increase (decrease) in deferred tax assets other than net operating losses ​ ​ (5,742) ​ ​ 133 ​ ​ (5,609) ​ Decrease in valuation allowance as a result of foreign currency fluctuation ​ ​ 6,306 ​ ​ — ​ ​ 6,306 ​ Increase in valuation allowance due to change in tax rates ​ ​ — ​ ​ 372 ​ ​ 372 ​ Net increase in valuation allowance ​ $ 52,412 ​ $ 505 ​ $ 52,917 ​

Nature of Operations (Details)

Nature of Operations (Details) - USD ($) $ / shares in Units, $ in Thousands	1 Months Ended						2 Months Ended	3 Months Ended								6 Months Ended		9 Months Ended		12 Months Ended
	Feb. 28, 2021	Jan. 31, 2021	Nov. 30, 2020	Aug. 31, 2020	Dec. 31, 2019	Mar. 31, 2019	Feb. 28, 2021	Dec. 31, 2020	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Jun. 30, 2020	Jun. 30, 2019	Sep. 30, 2020	Sep. 30, 2019	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018	May 31, 2020	May 29, 2020	May 18, 2020
Liquidity
Number of common stock sold			43,700,000	35,276,250	46,000,000	10,000,000		4,400,000												79,000,000
Share Price			$ 22.25	$ 10.25	$ 2.75	$ 2.35						$ 2.75			$ 2.35						$ 2.75
Proceeds from public offerings, net of transaction costs			$ 927,300	$ 344,400	$ 120,400	$ 23,500									$ 23,498	$ (269)	$ 28,265	$ 344,398	$ 38,098	$ 1,271,714	$ 158,343	$ 7,195
Common stock, shares issued					318,637,560			473,977,469				318,637,560								473,977,469	318,637,560
Cash and cash equivalents					$ 139,496	39,336		$ 1,312,404	$ 448,140	$ 152,492	$ 74,340	$ 139,496	$ 43,275	$ 19,845	39,336	152,492	19,845	448,140	43,275	$ 1,312,404	$ 139,496
Restricted cash								321,900												321,900
Net loss attributable to common shareholders								(484,105)	(65,217)	(9,414)	(37,445)	(19,277)	(18,366)	(17,351)	(30,560)	(46,859)	(47,911)	(112,076)	(66,277)	(596,181)	(85,555)	(85,660)
Net loss attributable to common shareholders								484,105	65,217	9,414	37,445	19,277	18,366	17,351	30,560	46,859	47,911	112,076	66,277	596,181	85,555	85,660
Net cash used in operating activities											60,402				35,699	111,891	48,328	156,506	54,141	155,476	53,324	$ 58,350
Accumulated deficit					(1,350,307)	(1,297,072)		(1,946,488)	(1,462,377)	(1,397,160)	(1,387,752)	(1,350,307)	(1,332,259)	(1,314,425)	(1,297,072)	(1,397,160)	(1,314,425)	(1,462,377)	(1,332,259)	(1,946,488)	(1,350,307)
Total operating lease, liabilities								113,938												113,938
Total finance lease liabilities								5,396												5,396
Operating lease liabilities					9,428	7,042		14,314	10,609	9,453	8,959	9,428	8,666	7,512	7,042	9,453	7,512	10,609	8,666	14,314	9,428
Finance lease liabilities					$ 226	$ 236		903	$ 374	$ 345	$ 204	$ 226	$ 310	$ 266	$ 236	$ 345	$ 266	$ 374	$ 310	903	$ 226
Incremental term loan								175,400												175,400
Short-term borrowing								25,400												25,400
Convertible senior notes								85,600												85,600
Working capital																				1,400,000
Interest rate (as a percent)																							3.50%
Finance obligation
Liquidity
Total finance lease liabilities								181,553												181,553
Finance lease liabilities								$ 32,700												$ 32,700
3.75% Convertible Senior Notes
Liquidity
Share Price								$ 33.91												$ 33.91
Principal amount								$ 212,463												$ 212,463			$ 212,463	$ 12,500	$ 200,000
Interest rate (as a percent)								3.75%												3.75%			3.75%	3.75%	3.75%
Private placement | 3.75% Convertible Senior Notes
Liquidity
Principal amount																							$ 212,500
Interest rate (as a percent)																							3.75%
Subsequent event
Liquidity
Number of common stock sold							32.2
Subsequent event | 3.75% Convertible Senior Notes
Liquidity
Interest rate (as a percent)	3.75%	3.75%					3.75%
Subsequent event | SK Holdings Co LTD
Liquidity
Number of common stock sold	54,996,188
Proceeds from public offerings, net of transaction costs	$ 1,600,000
Common stock, shares issued	54,966,188						54,966,188
Per share price of shares of common stock	$ 29.2893						$ 29.2893
Subsequent event | Public Offerings
Liquidity
Number of common stock sold	32,200,000	32,200,000
Share Price	$ 65	$ 65					$ 65
Proceeds from public offerings, net of transaction costs	$ 1,800,000	$ 1,800,000

Restatement of Previously Iss_3

Restatement of Previously Issued Consolidated Financial Statements - Restatement Background (Details) - USD ($) $ in Thousands	3 Months Ended								6 Months Ended		9 Months Ended		12 Months Ended
	Dec. 31, 2020	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Jun. 30, 2020	Jun. 30, 2019	Sep. 30, 2020	Sep. 30, 2019	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018	Jan. 01, 2018
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Operating Lease, Right-of-Use Asset	$ 117,016	$ 90,184	$ 71,789	$ 64,812	$ 63,266	$ 47,016	$ 39,679	$ 33,599	$ 71,789	$ 39,679	$ 90,184	$ 47,016	$ 117,016	$ 63,266
Operating Lease, Liability	113,938												113,938
Total cost of revenue		135,632	68,010	50,522	83,861	54,892	51,324	29,250	118,532	80,574	254,164	135,466	376,179	219,327	$ 200,219
Net Income (Loss) Available to Common Stockholders, Basic	(484,105)	(65,217)	(9,414)	(37,445)	(19,277)	(18,366)	(17,351)	(30,560)	(46,859)	(47,911)	(112,076)	(66,277)	(596,181)	(85,555)	(85,660)
Increase in accumulated deficit	(1,946,488)	(1,462,377)	(1,397,160)	(1,387,752)	(1,350,307)	(1,332,259)	(1,314,425)	(1,297,072)	(1,397,160)	(1,314,425)	(1,462,377)	(1,332,259)	(1,946,488)	(1,350,307)
Research and Development Expense		7,386	4,873	4,774	4,882	3,563	3,608	3,006	9,647	6,614	17,033	10,177	27,848	15,059	12,750
Nonoperating Income (Expense)		(17,551)	(13,462)	(11,846)	(10,999)	(8,273)	(7,965)	(8,454)	(25,308)	(16,419)	(42,859)	(24,692)	(60,484)	(35,691)	(22,750)
Asset Impairment Charges													6,430
Right of use assets obtained in exchange for new operating lease liabilities													58,500	37,700
Other current liabilities	29,487	21,083	19,418	8,446	6,704	8,373	3,705	3,745	19,418	3,705	21,083	8,373	29,487	6,704
Other liabilities	40,447	45,170	14,476	2,386	2,818	2,834	3,333	3,746	14,476	3,333	45,170	2,834	40,447	2,818
Finance Lease, Liability	5,396												5,396
Finance obligations	32,717	31,349	28,794	26,209	24,667	20,469	12,455	11,028	28,794	12,455	31,349	20,469	32,717	24,667
Financing Transaction Finance Obligation Amount	$ 148,836	140,662	131,653	121,322	119,422	99,669	76,916	54,864	131,653	76,916	140,662	99,669	148,836	119,422
Series E Redeemable Convertible Preferred Stock
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Dividends, Preferred Stock														1,800
Provision (benefit) for loss contracts related to service
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Total cost of revenue		25,147	706	95	13	206	363	162	801	201	25,948	407	35,473	394	5,345
Sales of fuel cell systems and related infrastructure
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Total cost of revenue		69,428	33,888	13,974	47,091	25,183	23,329	2,312	47,862	25,641	117,290	50,824	171,404	97,915	85,205
Sales of fuel cell systems and related infrastructure | Revision of Research and Development Expense
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Total cost of revenue														7,000
Fuel delivered to customers
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Total cost of revenue		17,002	11,076	11,254	12,800	11,149	11,146	10,152	22,330	21,298	39,332	32,447	61,815	45,247	36,037
Fuel delivered to customers | Revision of Research and Development Expense
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Total cost of revenue														8,900
Services performed on fuel cell systems and related infrastructure
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Total cost of revenue		9,180	7,773	10,347	11,606	7,802	8,383	6,791	18,120	15,174	27,300	22,976	42,524	34,582	32,271
Power Purchase Agreements
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Total cost of revenue		14,744	14,504	14,771	12,301	10,814	8,829	9,833	29,275	18,662	44,019	29,476	$ 64,640	41,777	41,361
Restatement Adjustments
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Operating Lease, Right-of-Use Asset		90,184	71,789	64,812	63,266	47,016	39,679	33,599	71,789	39,679	90,184	47,016		63,266
Total cost of revenue		27,353	5,016	5,238	4,979	3,778	4,410	3,887	10,254	8,297	37,607	12,075		17,054	28,209
Net Income (Loss) Available to Common Stockholders, Basic		(25,838)	(745)	47	(989)	(209)	756	444	(705)	1,161	(26,543)	952		(38)	(7,493)
Increase in accumulated deficit		(31,037)	(5,199)	(4,453)	(4,500)	(4,741)	(5,062)	(5,817)	(5,199)	(5,062)	(31,037)	(4,741)		(4,500)
Research and Development Expense		(4,578)	(4,884)	(5,638)	(4,459)	(4,465)	(5,325)	(4,367)	(10,522)	(9,692)	(15,100)	(14,157)		(18,616)	(21,157)
Nonoperating Income (Expense)		(310)	(264)	(263)	(193)	(301)	(104)	(109)	(527)	(213)	(837)	(514)		(189)	(615)
Other current liabilities		3,803	(2,274)	(1,977)	(1,839)	(1,865)	688	1,474	(2,274)	688	3,803	(1,865)		(1,839)
Other liabilities		18,102	2,720	2,373	2,805	2,821	3,320	3,729	2,720	3,320	18,102	2,821		2,805
Finance obligations		(32,343)	(28,901)	(25,838)	(24,840)	(20,643)	(18,208)	(12,969)	(28,901)	(18,208)	(32,343)	(20,643)		(24,840)
Financing Transaction Finance Obligation Amount		(196,488)	(169,000)	(150,849)	(145,806)	(108,796)	(80,615)	(56,331)	(169,000)	(80,615)	(196,488)	(108,796)		(145,806)
Restatement Adjustments | Series E Redeemable Convertible Preferred Stock
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Net Income (Loss) Available to Common Stockholders, Basic														1,800
Dividends, Preferred Stock														1,800	1,800
Restatement Adjustments | Revision of Lease Liability
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Increase in accumulated deficit					4,500									4,500	6,200
Restatement Adjustments | Revision of Deemed Dividend [Member] | Series E Redeemable Convertible Preferred Stock
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Deemed Dividend														1,800
Restatement Adjustments | Revision of Research and Development Expense
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Total cost of revenue														1,100
Research and Development Expense														(19,492)	(21,157)
Restatement Adjustments | Cumulative effect from adoption of ASC 842
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Increase in accumulated deficit																$ 3,400
Restatement Adjustments | Provision (benefit) for loss contracts related to service
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Total cost of revenue		20,841	706	95	13	206	363	162	801	201	21,642	407		394	5,345
Restatement Adjustments | Sales of fuel cell systems and related infrastructure
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Total cost of revenue		919	212	230	672	193	200	(9)	442	191	1,361	384		1,056	766
Restatement Adjustments | Sales of fuel cell systems and related infrastructure | Revision of Research and Development Expense
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Total cost of revenue															614
Restatement Adjustments | Fuel delivered to customers
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Total cost of revenue		2,830	2,016	2,219	2,378	1,989	2,292	2,231	4,235	4,523	7,065	6,512		8,890	8,325
Restatement Adjustments | Fuel delivered to customers | Revision of Research and Development Expense
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Total cost of revenue															8,300
Restatement Adjustments | Services performed on fuel cell systems and related infrastructure
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Total cost of revenue		2,106	1,282	2,166	1,607	1,341	2,165	668	3,448	2,833	5,554	4,174		5,781	8,573
Restatement Adjustments | Services performed on fuel cell systems and related infrastructure | Revision of Research and Development Expense
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Total cost of revenue														2,500	8,000
Restatement Adjustments | Power Purchase Agreements
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Total cost of revenue		$ 657	$ 800	$ 528	$ 309	$ 461	$ 116	$ 835	$ 1,328	$ 951	$ 1,985	$ 1,412		$ 1,721	5,200
Restatement Adjustments | Power Purchase Agreements | Revision of Research and Development Expense
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Total cost of revenue															$ 4,200

Restatement of Previously Iss_4

Restatement of Previously Issued Consolidated Financial Statements - Research and development expense (Details) - USD ($) $ in Thousands	3 Months Ended								6 Months Ended		9 Months Ended		12 Months Ended
	Dec. 31, 2020	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Jun. 30, 2020	Jun. 30, 2019	Sep. 30, 2020	Sep. 30, 2019	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Research and Development Expense		$ 7,386	$ 4,873	$ 4,774	$ 4,882	$ 3,563	$ 3,608	$ 3,006	$ 9,647	$ 6,614	$ 17,033	$ 10,177	$ 27,848	$ 15,059	$ 12,750
Gross Profit	$ (431,114)	(28,584)	(15)	(9,703)	7,746	4,500	6,142	(7,740)	(9,718)	(1,598)	(38,302)	2,902	$ (469,416)	10,648	(26,004)
Restatement Adjustments
Cost of Revenue														19,492	21,157
Research and Development Expense		(4,578)	(4,884)	(5,638)	(4,459)	(4,465)	(5,325)	(4,367)	(10,522)	(9,692)	(15,100)	(14,157)		(18,616)	(21,157)
Gross Profit		$ (27,294)	$ (5,091)	$ (5,232)	$ (5,036)	$ (3,847)	$ (4,479)	$ (3,956)	$ (10,323)	$ (8,435)	$ (37,617)	$ (12,282)		(17,318)	(28,626)
Restatement Adjustments | Sales of fuel cell systems and related infrastructure
Cost of Revenue														1,121	614
Restatement Adjustments | Services performed on fuel cell systems and related infrastructure
Cost of Revenue														6,986	7,954
Restatement Adjustments | Power Purchase Agreements
Cost of Revenue														2,539	4,264
Revision of Research and Development Expense | Restatement Adjustments
Research and Development Expense														$ (19,492)	$ (21,157)

Restatement of Previously Iss_5

Restatement of Previously Issued Consolidated Financial Statements - Consolidated Balance Sheets (Details) - USD ($)	Dec. 31, 2020	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Current assets:
Cash and cash equivalents	$ 1,312,404,000	$ 448,140,000	$ 152,492,000	$ 74,340,000	$ 139,496,000	$ 43,275,000	$ 19,845,000	$ 39,336,000
Restricted cash	64,041,000	55,704,000	50,634,000	56,804,000	54,813,000	35,720,000	19,400,000	19,297,000
Accounts receivable	43,041,000	113,505,000	45,782,000	24,734,000	25,768,000	24,737,000	26,844,000	32,307,000
Inventory	139,386,000	134,203,000	114,571,000	92,972,000	72,391,000	80,601,000	73,190,000	65,474,000
Prepaid expenses and other current assets	44,324,000	26,731,000	31,436,000	28,500,000	21,192,000	12,804,000	14,001,000	10,296,000
Total current assets	1,603,196,000	778,283,000	394,915,000	277,350,000	313,660,000	197,137,000	153,280,000	166,710,000
Restricted cash	257,839,000	227,528,000	180,127,000	176,070,000	175,191,000	119,322,000	96,082,000	50,598,000
Property, plant, and equipment, net	74,549,000	64,820,000	60,018,000	16,591,000	14,959,000	14,990,000	14,228,000	13,615,000
Right of use assets related to finance leases, net	5,724,000	2,335,000	2,389,000	1,707,000	1,714,000	1,720,000	1,726,000	1,733,000
Right of use assets related to operating leases	117,016,000	90,184,000	71,789,000	64,812,000	63,266,000	47,016,000	39,679,000	33,599,000
Equipment related to power purchase agreements and fuel delivered to customers, net	75,807,000	71,891,000	68,428,000	68,402,000	67,769,000	67,248,000	68,982,000	70,928,000
Goodwill	72,387,000	71,822,000	70,262,000	8,673,000	8,842,000	8,606,000	8,961,000	8,886,000
Intangible assets, net	39,251,000	39,569,000	38,974,000	5,696,000	5,539,000	5,113,000	5,398,000	3,677,000
Other assets	5,513,000	9,661,000	11,817,000	12,059,000	8,573,000	9,152,000	8,842,000	11,069,000
Total assets	2,251,282,000	1,356,093,000	898,719,000	631,360,000	659,513,000	470,304,000	397,178,000	360,815,000
Current liabilities:
Accounts payable	50,198,000	58,793,000	39,812,000	35,503,000	40,376,000	36,851,000	36,946,000	31,688,000
Accrued expenses	46,083,000	37,948,000	23,917,000	14,870,000	14,409,000	9,457,000	4,522,000	6,509,000
Deferred revenue	23,275,000	17,226,000	14,902,000	11,557,000	11,691,000	11,480,000	11,730,000	11,736,000
Operating lease liabilities	14,314,000	10,609,000	9,453,000	8,959,000	9,428,000	8,666,000	7,512,000	7,042,000
Finance lease liabilities	903,000	374,000	345,000	204,000	226,000	310,000	266,000	236,000
Finance obligations	32,717,000	31,349,000	28,794,000	26,209,000	24,667,000	20,469,000	12,455,000	11,028,000
Current portion of long-term debt	25,389,000	74,829,000	50,933,000	27,819,000	26,461,000	17,202,000	15,928,000	12,559,000
Other current liabilities	29,487,000	21,083,000	19,418,000	8,446,000	6,704,000	8,373,000	3,705,000	3,745,000
Total current liabilities	222,366,000	252,211,000	187,574,000	133,567,000	133,962,000	112,808,000	93,064,000	84,543,000
Deferred revenue	32,944,000	29,511,000	24,848,000	22,684,000	23,170,000	22,213,000	24,126,000	25,366,000
Operating lease liabilities	99,624,000	74,422,000	58,410,000	52,165,000	50,937,000	36,599,000	30,631,000	25,657,000
Finance lease liabilities	4,493,000	2,384,000	2,465,000	1,953,000	2,011,000	2,068,000	2,123,000	2,142,000
Finance obligations	148,836,000	140,662,000	131,653,000	121,322,000	119,422,000	99,669,000	76,916,000	54,864,000
Common stock warrant liability						98,000	525,000	2,231,000
Convertible senior notes, net	85,640,000	105,088,000	142,889,000	113,063,000	110,431,000	107,945,000	66,844,000	65,025,000
Long-term debt	150,013,000	120,380,000	101,844,000	79,119,000	85,708,000	78,840,000	83,776,000	72,676,000
Other liabilities	40,447,000	45,170,000	14,476,000	2,386,000	2,818,000	2,834,000	3,333,000	3,746,000
Total liabilities	784,363,000	769,828,000	664,159,000	526,259,000	528,459,000	463,074,000	381,338,000	336,250,000
Redeemable preferred stock:
Preferred stock						0.01
Stockholders' equity:
Common stock, $.01 par value	4,740,000	4,061,000	3,482,000	3,222,000	3,186,000	2,540,000	2,470,000	2,445,000
Additional paid-in capital	3,446,650,000	2,083,169,000	1,658,438,000	1,519,094,000	1,506,953,000	1,340,781,000	1,325,381,000	1,316,815,000
Accumulated other comprehensive income	2,451,000	1,846,000	1,159,000	1,052,000	1,288,000	929,000	1,460,000	1,374,000
Accumulated deficit	(1,946,488,000)	(1,462,377,000)	(1,397,160,000)	(1,387,752,000)	(1,350,307,000)	(1,332,259,000)	(1,314,425,000)	(1,297,072,000)
Less common stock in treasury	(40,434,000)	(40,434,000)	(31,359,000)	(31,224,000)	(31,216,000)	(31,216,000)	(30,681,000)	(30,637,000)
Total stockholders' equity	1,466,919,000	586,265,000	234,560,000	104,392,000	129,904,000	(19,225,000)	(15,795,000)	(7,075,000)	$ (3,588,000)	$ 70,229,000
Total liabilities, redeemable preferred stock, and stockholders' equity	$ 2,251,282,000	1,356,093,000	898,719,000	631,360,000	659,513,000	470,304,000	397,178,000	360,815,000
Series C Redeemable Convertible Preferred Stock
Redeemable preferred stock:
Preferred stock				709,000	709,000	709,000	709,000	709,000
Series E Redeemable Convertible Preferred Stock
Redeemable preferred stock:
Preferred stock					441,000	25,746,000	30,926,000	30,931,000
As previously Reported
Current assets:
Cash and cash equivalents		448,140,000	152,492,000	74,340,000	139,496,000	43,275,000	19,845,000	39,336,000
Restricted cash		55,704,000	50,634,000	56,804,000	54,813,000	35,720,000	19,400,000	19,297,000
Accounts receivable		113,133,000	45,522,000	24,437,000	25,448,000	24,392,000	26,592,000	32,062,000
Inventory		134,306,000	114,571,000	92,972,000	72,391,000	80,601,000	73,190,000	65,474,000
Prepaid expenses and other current assets		26,731,000	31,436,000	28,500,000	21,192,000	12,804,000	14,001,000	10,296,000
Total current assets		778,014,000	394,655,000	277,053,000	313,340,000	196,792,000	153,028,000	166,465,000
Restricted cash		227,528,000	180,127,000	176,070,000	175,191,000	119,322,000	96,082,000	50,598,000
Property, plant, and equipment, net		64,820,000	60,018,000	16,591,000	14,959,000	14,990,000	14,228,000	13,615,000
Equipment related to power purchase agreements and fuel delivered to customers, net		309,475,000	274,721,000	252,802,000	244,740,000	202,034,000	170,455,000	141,889,000
Goodwill		71,962,000	70,402,000	8,673,000	8,842,000	8,606,000	8,961,000	8,886,000
Intangible assets, net		39,169,000	38,574,000	5,296,000	5,539,000	5,113,000	5,398,000	3,677,000
Other assets		9,661,000	11,817,000	12,059,000	8,573,000	9,152,000	8,842,000	11,069,000
Total assets		1,500,629,000	1,030,314,000	748,544,000	771,184,000	556,009,000	456,994,000	396,199,000
Current liabilities:
Accounts payable		58,793,000	39,812,000	35,503,000	40,376,000	36,851,000	36,946,000	31,688,000
Accrued expenses		32,031,000	23,320,000	14,273,000	14,213,000	9,457,000	4,522,000	6,509,000
Deferred revenue		17,226,000	14,902,000	11,557,000	11,691,000	11,480,000	11,730,000	11,736,000
Finance obligations		63,692,000	57,695,000	52,047,000	49,507,000	41,112,000	30,663,000	23,997,000
Current portion of long-term debt		74,829,000	50,933,000	27,819,000	26,461,000	17,202,000	15,928,000	12,559,000
Other current liabilities		17,280,000	21,692,000	10,423,000	8,543,000	10,238,000	3,017,000	2,271,000
Total current liabilities		263,851,000	208,354,000	151,622,000	150,791,000	126,340,000	102,806,000	88,760,000
Deferred revenue		29,648,000	25,038,000	22,912,000	23,369,000	22,444,000	24,519,000	25,835,000
Finance obligations		337,150,000	300,653,000	272,171,000	265,228,000	208,465,000	157,531,000	111,195,000
Common stock warrant liability						98,000	525,000	2,231,000
Convertible senior notes, net		105,088,000	142,704,000	112,878,000	110,246,000	107,760,000	66,844,000	65,025,000
Long-term debt		120,380,000	101,844,000	79,119,000	85,708,000	78,840,000	83,776,000	72,676,000
Other liabilities		27,068,000	11,756,000	13,000	13,000	13,000	13,000	17,000
Total liabilities		883,185,000	790,349,000	638,715,000	635,355,000	543,960,000	436,014,000	365,739,000
Stockholders' equity:
Common stock, $.01 par value		4,061,000	3,482,000	3,222,000	3,186,000	2,540,000	2,470,000	2,445,000
Additional paid-in capital		2,083,199,000	1,658,532,000	1,519,257,000	1,507,116,000	1,340,859,000	1,325,459,000	1,316,893,000
Accumulated other comprehensive income		1,958,000	1,271,000	1,164,000	1,400,000	929,000	1,460,000	1,374,000
Accumulated deficit		(1,431,340,000)	(1,391,961,000)	(1,383,299,000)	(1,345,807,000)	(1,327,518,000)	(1,309,363,000)	(1,291,255,000)
Less common stock in treasury		(40,434,000)	(31,359,000)	(31,224,000)	(31,216,000)	(31,216,000)	(30,681,000)	(30,637,000)
Total stockholders' equity		617,444,000	239,965,000	109,120,000	134,679,000	(14,406,000)	(10,655,000)	(1,180,000)	2,713,000	73,646,000
Total liabilities, redeemable preferred stock, and stockholders' equity		1,500,629,000	1,030,314,000	748,544,000	771,184,000	556,009,000	456,994,000	396,199,000
As previously Reported | Series C Redeemable Convertible Preferred Stock
Redeemable preferred stock:
Preferred stock				709,000	709,000	709,000	709,000	709,000
As previously Reported | Series E Redeemable Convertible Preferred Stock
Redeemable preferred stock:
Preferred stock					441,000	25,746,000	30,926,000	30,931,000
Restatement Adjustments
Current assets:
Accounts receivable		372,000	260,000	297,000	320,000	345,000	252,000	245,000
Inventory		(103,000)
Total current assets		269,000	260,000	297,000	320,000	345,000	252,000	245,000
Right of use assets related to finance leases, net		2,335,000	2,389,000	1,707,000	1,714,000	1,720,000	1,726,000	1,733,000
Right of use assets related to operating leases		90,184,000	71,789,000	64,812,000	63,266,000	47,016,000	39,679,000	33,599,000
Equipment related to power purchase agreements and fuel delivered to customers, net		(237,584,000)	(206,293,000)	(184,400,000)	(176,971,000)	(134,786,000)	(101,473,000)	(70,961,000)
Goodwill		(140,000)	(140,000)
Intangible assets, net		400,000	400,000	400,000
Total assets		(144,536,000)	(131,595,000)	(117,184,000)	(111,671,000)	(85,705,000)	(59,816,000)	(35,384,000)
Current liabilities:
Accrued expenses		5,917,000	597,000	597,000	196,000
Operating lease liabilities		10,609,000	9,453,000	8,959,000	9,428,000	8,666,000	7,512,000	7,042,000
Finance lease liabilities		374,000	345,000	204,000	226,000	310,000	266,000	236,000
Finance obligations		(32,343,000)	(28,901,000)	(25,838,000)	(24,840,000)	(20,643,000)	(18,208,000)	(12,969,000)
Other current liabilities		3,803,000	(2,274,000)	(1,977,000)	(1,839,000)	(1,865,000)	688,000	1,474,000
Total current liabilities		(11,640,000)	(20,780,000)	(18,055,000)	(16,829,000)	(13,532,000)	(9,742,000)	(4,217,000)
Deferred revenue		(137,000)	(190,000)	(228,000)	(199,000)	(231,000)	(393,000)	(469,000)
Operating lease liabilities		74,422,000	58,410,000	52,165,000	50,937,000	36,599,000	30,631,000	25,657,000
Finance lease liabilities		2,384,000	2,465,000	1,953,000	2,011,000	2,068,000	2,123,000	2,142,000
Finance obligations		(196,488,000)	(169,000,000)	(150,849,000)	(145,806,000)	(108,796,000)	(80,615,000)	(56,331,000)
Convertible senior notes, net			185,000	185,000	185,000	185,000
Other liabilities		18,102,000	2,720,000	2,373,000	2,805,000	2,821,000	3,320,000	3,729,000
Total liabilities		(113,357,000)	(126,190,000)	(112,456,000)	(106,896,000)	(80,886,000)	(54,676,000)	(29,489,000)
Stockholders' equity:
Additional paid-in capital		(30,000)	(94,000)	(163,000)	(163,000)	(78,000)	(78,000)	(78,000)
Accumulated other comprehensive income		(112,000)	(112,000)	(112,000)	(112,000)
Accumulated deficit		(31,037,000)	(5,199,000)	(4,453,000)	(4,500,000)	(4,741,000)	(5,062,000)	(5,817,000)
Total stockholders' equity		(31,179,000)	(5,405,000)	(4,728,000)	(4,775,000)	(4,819,000)	(5,140,000)	(5,895,000)	$ (6,301,000)	$ (3,417,000)
Total liabilities, redeemable preferred stock, and stockholders' equity		$ (144,536,000)	$ (131,595,000)	$ (117,184,000)	$ (111,671,000)	$ (85,705,000)	$ (59,816,000)	$ (35,384,000)

Restatement of Previously Iss_6

Restatement of Previously Issued Consolidated Financial Statements - Consolidated Balance Sheets (Narrative) (Details) - USD ($) $ / shares in Units, $ in Thousands	Dec. 31, 2020	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Common stock, par value (in dollars per share)	$ 0.01	$ 0.01	$ 0.01	$ 0.01	$ 0.01	$ 0.01	$ 0.01	$ 0.01
Common Stock, Shares Authorized	750,000,000				750,000,000
Common stock, shares issued	473,977,469				318,637,560
Common Stock, Shares Outstanding	458,051,920				303,378,515
Common stock in treasury, shares	15,926,068				15,259,045
Series C Redeemable Convertible Preferred Stock
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Redeemable convertible Preferred Stock, par value (in dollars per share)	$ 0.01			$ 0.01	$ 0.01	$ 0.01	$ 0.01	$ 0.01
Redeemable convertible Preferred Stock, shares authorized	10,431			10,431,000	10,431	10,431,000	10,431,000	10,431,000
Redeemable convertible Preferred Stock, shares issued	0			2,620,000	2,620	2,620,000	2,620,000	2,620,000
Redeemable convertible Preferred Stock, shares outstanding	0			2,620,000	2,620	2,620,000	2,620,000	2,620,000
Redeemable convertible Preferred Stock, aggregate involuntary liquidation preference (in dollars)	$ 16,664			$ 16,664	$ 16,664		$ 16,664	$ 16,664
Series E Redeemable Convertible Preferred Stock
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Redeemable convertible Preferred Stock, par value (in dollars per share)					$ 0.01	$ 0.01	$ 0.01	$ 0.01
Redeemable convertible Preferred Stock, shares authorized					35,000,000	35,000,000	35,000,000	35,000,000
Redeemable convertible Preferred Stock, shares issued					500,000	28,269,000	35,000,000	35,000,000
Redeemable convertible Preferred Stock, shares outstanding					500,000	28,269,000	35,000,000
Redeemable convertible Preferred Stock, aggregate involuntary liquidation preference (in dollars)							$ 35,000	$ 35,000

Restatement of Previously Iss_7

Restatement of Previously Issued Consolidated Financial Statements - Consolidated Statements of Income (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended								6 Months Ended		9 Months Ended		12 Months Ended
	Dec. 31, 2020	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Jun. 30, 2020	Jun. 30, 2019	Sep. 30, 2020	Sep. 30, 2019	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Net revenue:
Net revenue	$ 309,099	$ 107,048	$ 67,995	$ 40,819	$ 91,607	$ 59,392	$ 57,466	$ 21,510		$ 78,976		$ 138,368
Net revenue		107,048	67,995	40,819	91,607				$ 108,814		$ 215,862		$ (93,237)	$ 229,975	$ 174,215
Cost of revenue:
Total cost of revenue		135,632	68,010	50,522	83,861	54,892	51,324	29,250	118,532	80,574	254,164	135,466	376,179	219,327	200,219
Gross (loss) profit	(431,114)	(28,584)	(15)	(9,703)	7,746	4,500	6,142	(7,740)	(9,718)	(1,598)	(38,302)	2,902	(469,416)	10,648	(26,004)
Operating expenses:
Research and development		7,386	4,873	4,774	4,882	3,563	3,608	3,006	9,647	6,614	17,033	10,177	27,848	15,059	12,750
Selling, general and administrative		17,210	21,644	11,109	9,973	10,395	13,613	9,221	32,753	22,834	49,963	33,229	79,348	43,202	37,685
Change in fair value of contingent consideration		1,130									1,130		1,160
Total operating expenses	46,660	25,726	26,517	15,883	14,855	13,958	17,221	12,227	42,400	29,448	68,126	43,406	114,786	58,261	50,435
Operating loss	(477,774)	(54,310)	(26,532)	(25,586)	(7,109)	(9,458)	(11,079)	(19,967)	(52,118)	(31,046)	(106,428)	(40,504)	(584,202)	(47,613)	(76,439)
Interest and other expense, net		(17,551)	(13,462)	(11,846)	(10,999)	(8,273)	(7,965)	(8,454)	(25,308)	(16,419)	(42,859)	(24,692)	(60,484)	(35,691)	(22,750)
Change in fair value of common stock warrant liability					72	427	1,706	(2,126)		(420)		7		79	4,286
Impairment of long-lived assets													(6,430)
Gain (loss) on extinguishment of debt			13,222			(518)		(518)	13,222	(518)	13,222	(518)	17,686	(518)
Loss before income taxes		(71,861)	(26,772)	(37,432)	(18,036)	(17,822)	(17,338)	(30,547)	(64,204)	(47,885)	(136,065)	(65,707)	(627,000)	(83,743)	(94,903)
Income tax benefit		6,644	17,371						17,371		24,015		30,845		9,295
Net loss attributable to the Company		(65,217)	(9,401)	(37,432)	(18,036)	(17,822)	(17,338)	(30,547)	(46,833)	(47,885)	(112,050)	(65,707)	(596,155)	(83,743)	(85,608)
Preferred stock dividends declared, deemed dividends and accretion of discount			(13)	(13)	(1,241)	(544)	(13)	(13)	(26)	(26)	(26)	(570)	(26)	(1,812)	(52)
Net loss attributable to common shareholders	$ (484,105)	$ (65,217)	$ (9,414)	$ (37,445)	$ (19,277)	$ (18,366)	$ (17,351)	$ (30,560)	$ (46,859)	$ (47,911)	$ (112,076)	$ (66,277)	$ (596,181)	$ (85,555)	$ (85,660)
Net loss per share:
Basic and diluted	$ (1.35)	$ (0.18)	$ (0.03)	$ (0.12)	$ (0.07)	$ (0.08)	$ (0.08)	$ (0.14)	$ (0.15)	$ (0.21)	$ (0.34)	$ (0.29)	$ (1.68)	$ (0.36)	$ (0.39)
Weighted average number of common stock outstanding		371,010,544	316,645,050	305,192,201	260,053,150	236,759,521	231,114,868	220,605,068	310,918,626	225,899,224	330,949,265	229,519,323	354,790,106	237,152,780	218,882,337
Sales of fuel cell systems and related infrastructure
Net revenue:
Net revenue	$ (246,171)	$ 83,662	$ 47,746	$ 20,468	$ 69,785	$ 38,883	$ 38,702	$ 2,550	$ 68,214	$ 41,252	$ 151,876	$ 80,135	$ (94,295)	$ 149,920	$ 107,175
Cost of revenue:
Total cost of revenue		69,428	33,888	13,974	47,091	25,183	23,329	2,312	47,862	25,641	117,290	50,824	171,404	97,915	85,205
Services performed on fuel cell systems and related infrastructure
Net revenue:
Net revenue	(29,387)	6,829	6,236	6,521	7,328	6,205	5,341	6,343	12,757	11,684	19,586	17,889	(9,801)	25,217	22,002
Cost of revenue:
Total cost of revenue		9,180	7,773	10,347	11,606	7,802	8,383	6,791	18,120	15,174	27,300	22,976	42,524	34,582	32,271
Provision (benefit) for loss contracts related to service
Cost of revenue:
Total cost of revenue		25,147	706	95	13	206	363	162	801	201	25,948	407	35,473	394	5,345
Power Purchase Agreements
Net revenue:
Net revenue	6,991	6,629	6,579	6,421	6,664	6,520	6,334	6,035	13,000	12,369	19,629	18,889	26,620	25,553	22,569
Cost of revenue:
Total cost of revenue		14,744	14,504	14,771	12,301	10,814	8,829	9,833	29,275	18,662	44,019	29,476	64,640	41,777	41,361
Fuel delivered to customers
Net revenue:
Net revenue	(40,608)	9,831	7,372	7,333	7,779	7,649	7,089	6,582	14,705	13,671	24,536	21,320	(16,072)	29,099	22,469
Cost of revenue:
Total cost of revenue		17,002	11,076	11,254	12,800	11,149	11,146	10,152	22,330	21,298	39,332	32,447	61,815	45,247	36,037
Other
Net revenue:
Net revenue	$ 76	97	62	76	51	135			138		235	135	311	186
Cost of revenue:
Total cost of revenue		131	63	81	50	150			144		275	150	$ 323	200
As previously Reported
Net revenue:
Net revenue						59,461	57,535	21,579		79,114		138,575
Net revenue		106,989	68,070	40,813	91,664				108,883		215,872			230,239	174,632
Cost of revenue:
Total cost of revenue		108,279	62,994	45,284	78,882	51,114	46,914	25,363	108,278	72,277	216,557	123,391		202,273	172,010
Gross (loss) profit		(1,290)	5,076	(4,471)	12,782	8,347	10,621	(3,784)	605	6,837	(685)	15,184		27,966	2,622
Operating expenses:
Research and development		11,964	9,757	10,412	9,341	8,028	8,933	7,373	20,169	16,306	32,133	24,334		33,675	33,907
Selling, general and administrative		14,277	21,658	11,013	10,982	10,400	13,627	9,324	32,671	22,951	46,948	33,351		44,333	38,198
Total operating expenses		26,241	31,415	21,425	20,323	18,428	22,560	16,697	52,840	39,257	79,081	57,685		78,008	72,105
Operating loss		(27,531)	(26,339)	(25,896)	(7,541)	(10,081)	(11,939)	(20,481)	(52,235)	(32,420)	(79,766)	(42,501)		(50,042)	(69,483)
Interest and other expense, net		(17,241)	(13,198)	(11,583)	(10,806)	(7,972)	(7,861)	(8,345)	(24,781)	(16,206)	(42,022)	(24,178)		(35,502)	(22,135)
Change in fair value of common stock warrant liability		(1,130)			72	427	1,706	(2,126)		(420)	(1,130)	7		79	4,286
Gain (loss) on extinguishment of debt			13,222			(518)			13,222		13,222	(518)
Loss before income taxes		(45,902)	(26,315)	(37,479)	(18,275)	(18,144)	(18,094)	(30,952)	(63,794)	(49,046)	(109,696)	(67,190)		(85,465)	(87,332)
Income tax benefit		6,523	17,659						17,659		24,182				9,217
Net loss attributable to the Company		(39,379)	(8,656)	(37,479)	(18,275)	(18,144)	(18,094)	(30,952)	(46,135)	(49,046)	(85,514)	(67,190)		(85,465)	(78,115)
Preferred stock dividends declared, deemed dividends and accretion of discount			(13)	(13)	(13)	(13)	(13)	(52)	(19)	(26)	(19)	(39)		(52)	(52)
Net loss attributable to common shareholders		$ (39,379)	$ (8,669)	$ (37,492)	$ (18,288)	$ (18,157)	$ (18,107)	$ (31,004)	$ (46,154)	$ (49,072)	$ (85,533)	$ (67,229)		$ (85,517)	$ (78,167)
Net loss per share:
Basic and diluted		$ (0.11)	$ (0.03)	$ (0.12)	$ (0.07)	$ (0.08)	$ (0.08)	$ (0.14)	$ (0.15)	$ (0.22)	$ (0.26)	$ (0.29)		$ (0.36)	$ (0.36)
Weighted average number of common stock outstanding		371,010,544	316,645,050	305,192,201	260,053,150	236,759,521	231,114,868	220,605,068	310,918,626	225,899,224	330,949,265	229,519,323		237,152,780	218,882,337
As previously Reported | Sales of fuel cell systems and related infrastructure
Net revenue:
Net revenue		$ 83,528	$ 47,746	$ 20,387	$ 69,767	$ 38,877	$ 38,696	$ 2,544	$ 68,133	$ 41,240	$ 151,661	$ 80,117		$ 149,884	$ 107,292
Cost of revenue:
Total cost of revenue		68,509	33,676	13,744	46,419	24,990	23,129	2,321	47,420	25,450	115,929	50,440		96,859	84,439
As previously Reported | Services performed on fuel cell systems and related infrastructure
Net revenue:
Net revenue		6,829	6,236	6,521	7,328	6,205	5,341	6,343	12,757	11,684	19,586	17,889		25,217	22,002
Cost of revenue:
Total cost of revenue		7,074	6,491	8,181	9,999	6,461	6,218	6,123	14,672	12,341	21,746	18,802		28,801	23,698
As previously Reported | Provision (benefit) for loss contracts related to service
Cost of revenue:
Total cost of revenue		4,306									4,306
As previously Reported | Power Purchase Agreements
Net revenue:
Net revenue		6,704	6,654	6,496	6,739	6,595	6,409	6,110	13,150	12,519	19,854	19,114		25,853	22,869
Cost of revenue:
Total cost of revenue		14,087	13,704	14,243	11,992	10,353	8,713	8,998	27,947	17,711	42,034	28,064		40,056	36,161
As previously Reported | Fuel delivered to customers
Net revenue:
Net revenue		9,831	7,372	7,333	7,779	7,649	7,089	6,582	14,705	13,671	24,536	21,320		29,099	22,469
Cost of revenue:
Total cost of revenue		14,172	9,060	9,035	10,422	9,160	8,854	7,921	18,095	16,775	32,267	25,935		36,357	27,712
As previously Reported | Other
Net revenue:
Net revenue		97	62	76	51	135			138		235	135		186
Cost of revenue:
Total cost of revenue		131	63	81	50	150			144		275	150		200
Restatement Adjustments
Net revenue:
Net revenue						(69)	(69)	(69)		(138)		(207)
Net revenue		59	(75)	6	(57)				(69)		(10)			(264)	(417)
Cost of revenue:
Total cost of revenue		27,353	5,016	5,238	4,979	3,778	4,410	3,887	10,254	8,297	37,607	12,075		17,054	28,209
Gross (loss) profit		(27,294)	(5,091)	(5,232)	(5,036)	(3,847)	(4,479)	(3,956)	(10,323)	(8,435)	(37,617)	(12,282)		(17,318)	(28,626)
Operating expenses:
Research and development		(4,578)	(4,884)	(5,638)	(4,459)	(4,465)	(5,325)	(4,367)	(10,522)	(9,692)	(15,100)	(14,157)		(18,616)	(21,157)
Selling, general and administrative		2,933	(14)	96	(1,009)	(5)	(14)	(103)	82	(117)	3,015	(122)		(1,131)	(513)
Change in fair value of contingent consideration		1,130									1,130
Total operating expenses		(515)	(4,898)	(5,542)	(5,468)	(4,470)	(5,339)	(4,470)	(10,440)	(9,809)	(10,955)	(14,279)		(19,747)	(21,670)
Operating loss		(26,779)	(193)	310	432	623	860	514	117	1,374	(26,662)	1,997		2,429	(6,956)
Interest and other expense, net		(310)	(264)	(263)	(193)	(301)	(104)	(109)	(527)	(213)	(837)	(514)		(189)	(615)
Change in fair value of common stock warrant liability		1,130									1,130
Gain (loss) on extinguishment of debt								(518)		(518)		(518)		(518)
Loss before income taxes		(25,959)	(457)	47	239	322	756	405	(410)	1,161	(26,369)	1,483		1,722	(7,571)
Income tax benefit		121	(288)						(288)		(167)				78
Net loss attributable to the Company		(25,838)	(745)	47	239	322	756	405	(698)	1,161	(26,536)	1,483		1,722	(7,493)
Preferred stock dividends declared, deemed dividends and accretion of discount					(1,228)	(531)		39	(7)		(7)	(531)		(1,760)
Net loss attributable to common shareholders		(25,838)	(745)	47	(989)	(209)	756	444	(705)	1,161	(26,543)	952		(38)	(7,493)
Restatement Adjustments | Sales of fuel cell systems and related infrastructure
Net revenue:
Net revenue		134		81	18	6	6	6	81	12	215	18		36	(117)
Cost of revenue:
Total cost of revenue		919	212	230	672	193	200	(9)	442	191	1,361	384		1,056	766
Restatement Adjustments | Services performed on fuel cell systems and related infrastructure
Cost of revenue:
Total cost of revenue		2,106	1,282	2,166	1,607	1,341	2,165	668	3,448	2,833	5,554	4,174		5,781	8,573
Restatement Adjustments | Provision (benefit) for loss contracts related to service
Cost of revenue:
Total cost of revenue		20,841	706	95	13	206	363	162	801	201	21,642	407		394	5,345
Restatement Adjustments | Power Purchase Agreements
Net revenue:
Net revenue		(75)	(75)	(75)	(75)	(75)	(75)	(75)	(150)	(150)	(225)	(225)		(300)	(300)
Cost of revenue:
Total cost of revenue		657	800	528	309	461	116	835	1,328	951	1,985	1,412		1,721	5,200
Restatement Adjustments | Fuel delivered to customers
Net revenue:
Net revenue														8,846	8,325
Cost of revenue:
Total cost of revenue		$ 2,830	$ 2,016	$ 2,219	$ 2,378	$ 1,989	$ 2,292	$ 2,231	$ 4,235	$ 4,523	$ 7,065	$ 6,512		$ 8,890	$ 8,325

Restatement of Previously Iss_8

Restatement of Previously Issued Consolidated Financial Statements - Consolidated Statements of Comprehensive Income (Details) - USD ($) $ in Thousands	3 Months Ended							6 Months Ended		9 Months Ended		12 Months Ended
	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Jun. 30, 2020	Jun. 30, 2019	Sep. 30, 2020	Sep. 30, 2019	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Net loss attributable to the Company	$ (65,217)	$ (9,401)	$ (37,432)	$ (18,036)	$ (17,822)	$ (17,338)	$ (30,547)	$ (46,833)	$ (47,885)	$ (112,050)	$ (65,707)	$ (596,155)	$ (83,743)	$ (85,608)
Other comprehensive gain (loss) - foreign currency translation adjustment	687	107	(236)	296	(531)	86	(210)	(129)	(124)	558	(655)	1,163	(296)	(610)
Comprehensive loss attributable to the Company	(64,530)	(9,294)	(37,668)	(17,740)	(18,353)	(17,252)	(30,757)	(46,962)	(48,009)	(111,492)	(66,362)	(594,992)	(84,039)	(86,218)
Preferred stock dividends declared, deemed dividends and accretion of discount		(13)	(13)	(1,241)	(544)	(13)	(13)	(26)	(26)	(26)	(570)	(26)	(1,812)	(52)
Comprehensive loss attributable to common stockholders	(64,530)	(9,307)	(37,681)	(18,981)	(18,897)	(17,265)	(30,770)	(46,988)	(48,035)	(111,518)	(66,932)	$ (595,018)	(85,851)	(86,270)
As previously Reported
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Net loss attributable to the Company	(39,379)	(8,656)	(37,479)	(18,275)	(18,144)	(18,094)	(30,952)	(46,135)	(49,046)	(85,514)	(67,190)		(85,465)	(78,115)
Other comprehensive gain (loss) - foreign currency translation adjustment	687	107	(236)		(531)	86	(210)	(129)	(124)	558	(655)		(184)	(610)
Comprehensive loss attributable to the Company	(38,692)	(8,549)	(37,715)		(18,675)	(18,008)	(31,162)	(46,264)	(49,170)	(84,956)	(67,845)		(85,649)	(78,725)
Preferred stock dividends declared, deemed dividends and accretion of discount		(13)	(13)	(13)	(13)	(13)	(52)	(19)	(26)	(19)	(39)		(52)	(52)
Comprehensive loss attributable to common stockholders	(38,692)	(8,562)	(37,728)		(18,688)	(18,021)	(31,214)	(46,283)	(49,196)	(84,975)	(67,884)		(85,701)	(78,777)
Restatement Adjustments
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Net loss attributable to the Company	(25,838)	(745)	47	239	322	756	405	(698)	1,161	(26,536)	1,483		1,722	(7,493)
Comprehensive loss attributable to the Company	(25,838)	(745)	47		322	756	405	(698)	1,161	(26,536)	1,483
Preferred stock dividends declared, deemed dividends and accretion of discount				$ (1,228)	(531)		39	(7)		(7)	(531)		(1,760)
Comprehensive loss attributable to common stockholders	$ (25,838)	$ (745)	$ 47		$ (209)	$ 756	$ 444	$ (705)	$ 1,161	$ (26,543)	$ 952
Restatement Adjustments | Cumulative Adjustment
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Net loss attributable to the Company													1,722	(7,493)
Other comprehensive gain (loss) - foreign currency translation adjustment													(112)
Comprehensive loss attributable to the Company													1,610	(7,493)
Preferred stock dividends declared, deemed dividends and accretion of discount													(1,760)
Comprehensive loss attributable to common stockholders													$ (150)	$ (7,493)

Restatement of Previously Iss_9

Restatement of Previously Issued Consolidated Financial Statements - Consolidated Statements of Stockholders' Equity (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018
Increase (Decrease) in Stockholders' Equity
Balance	$ 586,265	$ 234,560	$ 104,392	$ 129,904	$ (19,225)	$ (15,795)	$ (7,075)	$ (3,588)	$ 70,229
Balance (in shares)				318,637,560
Balance	$ 1,466,919	586,265	234,560	$ 104,392	$ 129,904	(19,225)	(15,795)	(7,075)	(3,588)
Balance (in shares)	473,977,469				318,637,560
Common Stock
Increase (Decrease) in Stockholders' Equity
Balance	$ 4,061	$ 3,482	$ 3,222	$ 3,186	$ 2,540	$ 2,470	$ 2,445	$ 2,342	$ 2,291
Balance (in shares)	406,123,816	348,201,792	322,220,469	318,637,560	253,982,578	246,975,173	244,537,235	234,160,661	229,073,517
Balance	$ 4,740	$ 4,061	$ 3,482	$ 3,222	$ 3,186	$ 2,540	$ 2,470	$ 2,445	$ 2,342
Balance (in shares)	473,977,469	406,123,816	348,201,792	322,220,469	318,637,560	253,982,578	246,975,173	244,537,235	234,160,661
Additional Paid-in-Capital
Increase (Decrease) in Stockholders' Equity
Balance	$ 2,083,169	$ 1,658,438	$ 1,519,094	$ 1,506,953	$ 1,340,781	$ 1,325,381	$ 1,316,815	$ 1,289,636	$ 1,250,899
Balance	3,446,650	2,083,169	1,658,438	1,519,094	1,506,953	1,340,781	1,325,381	1,316,815	1,289,636
Accumulated Other Comprehensive Income
Increase (Decrease) in Stockholders' Equity
Balance	1,846	1,159	1,052	1,288	929	1,460	1,374	1,584	2,194
Balance	2,451	1,846	1,159	1,052	1,288	929	1,460	1,374	1,584
Treasury Stock
Increase (Decrease) in Stockholders' Equity
Balance	$ (40,434)	$ (31,359)	$ (31,224)	$ (31,216)	$ (31,216)	$ (30,681)	$ (30,637)	$ (30,637)	$ (3,102)
Balance (in shares)	15,926,068	15,292,591	15,261,007	15,259,045	15,259,045	15,020,437	15,002,663	15,002,663	587,151
Balance	$ (40,434)	$ (40,434)	$ (31,359)	$ (31,224)	$ (31,216)	$ (31,216)	$ (30,681)	$ (30,637)	$ (30,637)
Balance (in shares)	15,926,068	15,926,068	15,292,591	15,261,007	15,259,045	15,259,045	15,020,437	15,002,663	15,002,663
Accumulated Deficit
Increase (Decrease) in Stockholders' Equity
Balance	$ (1,462,377)	$ (1,397,160)	$ (1,387,752)	$ (1,350,307)	$ (1,332,259)	$ (1,314,425)	$ (1,297,072)	$ (1,266,513)	$ (1,182,053)
Balance	(1,946,488)	(1,462,377)	(1,397,160)	(1,387,752)	(1,350,307)	(1,332,259)	(1,314,425)	(1,297,072)	(1,266,513)
As previously Reported
Increase (Decrease) in Stockholders' Equity
Balance	617,444	239,965	109,120	134,679	(14,406)	(10,655)	(1,180)	2,713	73,646
Balance		617,444	239,965	109,120	134,679	(14,406)	(10,655)	(1,180)	2,713
As previously Reported | Common Stock
Increase (Decrease) in Stockholders' Equity
Balance	$ 4,061	$ 3,482	$ 3,222	$ 3,186	$ 2,540	$ 2,470	$ 2,445	$ 2,342	$ 2,291
Balance (in shares)	406,123,816	348,201,792	322,220,469	318,637,560	253,982,578	246,975,173	244,537,235	234,160,661	229,073,517
Balance		$ 4,061	$ 3,482	$ 3,222	$ 3,186	$ 2,540	$ 2,470	$ 2,445	$ 2,342
Balance (in shares)		406,123,816	348,201,792	322,220,469	318,637,560	253,982,578	246,975,173	244,537,235	234,160,661
As previously Reported | Additional Paid-in-Capital
Increase (Decrease) in Stockholders' Equity
Balance	$ 2,083,199	$ 1,658,532	$ 1,519,257	$ 1,507,116	$ 1,340,859	$ 1,325,459	$ 1,316,893	$ 1,289,714	$ 1,250,899
Balance		2,083,199	1,658,532	1,519,257	1,507,116	1,340,859	1,325,459	1,316,893	1,289,714
As previously Reported | Accumulated Other Comprehensive Income
Increase (Decrease) in Stockholders' Equity
Balance	1,958	1,271	1,164	1,400	929	1,460	1,374	1,584	2,194
Balance		1,958	1,271	1,164	1,400	929	1,460	1,374	1,584
As previously Reported | Treasury Stock
Increase (Decrease) in Stockholders' Equity
Balance	$ (40,434)	$ (31,359)	$ (31,224)	$ (31,216)	$ (31,216)	$ (30,681)	$ (30,637)	$ (30,637)	$ (3,102)
Balance (in shares)	15,926,068	15,292,591	15,261,007	15,259,045	15,259,045	15,020,437	15,002,663	15,002,663	587,151
Balance		$ (40,434)	$ (31,359)	$ (31,224)	$ (31,216)	$ (31,216)	$ (30,681)	$ (30,637)	$ (30,637)
Balance (in shares)		15,926,068	15,292,591	15,261,007	15,259,045	15,259,045	15,020,437	15,002,663	15,002,663
As previously Reported | Accumulated Deficit
Increase (Decrease) in Stockholders' Equity
Balance	$ (1,431,340)	$ (1,391,961)	$ (1,383,299)	$ (1,345,807)	$ (1,327,518)	$ (1,309,363)	$ (1,291,255)	$ (1,260,290)	$ (1,178,636)
Balance		(1,431,340)	(1,391,961)	(1,383,299)	(1,345,807)	(1,327,518)	(1,309,363)	(1,291,255)	(1,260,290)
Restatement Adjustments
Increase (Decrease) in Stockholders' Equity
Balance	(31,179)	(5,405)	(4,728)	(4,775)	(4,819)	(5,140)	(5,895)	(6,301)	(3,417)
Balance		(31,179)	(5,405)	(4,728)	(4,775)	(4,819)	(5,140)	(5,895)	(6,301)
Restatement Adjustments | Additional Paid-in-Capital
Increase (Decrease) in Stockholders' Equity
Balance	(30)	(94)	(163)	(163)	(78)	(78)	(78)	(78)
Balance		(30)	(94)	(163)	(163)	(78)	(78)	(78)	(78)
Restatement Adjustments | Accumulated Other Comprehensive Income
Increase (Decrease) in Stockholders' Equity
Balance	(112)	(112)	(112)	(112)
Balance		(112)	(112)	(112)	(112)
Restatement Adjustments | Accumulated Deficit
Increase (Decrease) in Stockholders' Equity
Balance	$ (31,037)	(5,199)	(4,453)	(4,500)	(4,741)	(5,062)	(5,817)	(6,223)	(3,417)
Balance		$ (31,037)	$ (5,199)	$ (4,453)	$ (4,500)	$ (4,741)	$ (5,062)	$ (5,817)	$ (6,223)

Restatement of Previously Is_10

Restatement of Previously Issued Consolidated Financial Statements - Consolidated Statements of Cash Flows (Details) - USD ($) $ in Thousands	1 Months Ended				3 Months Ended								6 Months Ended		9 Months Ended		12 Months Ended
	Nov. 30, 2020	Aug. 31, 2020	Dec. 31, 2019	Mar. 31, 2019	Dec. 31, 2020	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Jun. 30, 2020	Jun. 30, 2019	Sep. 30, 2020	Sep. 30, 2019	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Operating Activities
Net loss attributable to the Company						$ (65,217)	$ (9,401)	$ (37,432)	$ (18,036)	$ (17,822)	$ (17,338)	$ (30,547)	$ (46,833)	$ (47,885)	$ (112,050)	$ (65,707)	$ (596,155)	$ (83,743)	$ (85,608)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation of long-lived assets								2,991				2,748	6,069	5,433	9,860	8,858	14,434	11,938	11,832
Amortization of intangible assets								175				175	398	338	835	518	1,135	698	693
Stock-based compensation								3,045				2,497	6,188	5,123	9,258	7,927	17,135	10,890	8,771
(Gain) loss on extinguishment of debt							(13,222)			518		518	(13,222)	518	(13,222)	518	(17,686)	518
Provision for bad debts and other assets												307		907		1,253	700	1,981	1,626
Amortization of debt issuance costs and discount on convertible senior notes								2,716				2,469	6,528	4,340	12,183	6,442	17,061	9,006	6,347
Provision for common stock warrants								2,566				1,193	7,983	2,209	25,198	3,706	425,047	6,513	10,190
Loss on disposal of leased assets								(128)						212		212		212
Impairment of long-lived assets																	6,430
Fair value adjustment to contingent consideration															1,130		(1,160)
Change in fair value of common stock warrant liability									(72)	(427)	(1,706)	2,126		420		(7)		(79)	(4,286)
Deferred income tax benefit						(6,644)	(17,371)						(17,371)		(24,015)		(30,845)		(9,295)
Loss (benefit) on service contracts								(128)				(142)	277	(873)	25,110	(1,366)	33,125	(1,643)	5,345
Changes in operating assets and liabilities that provide (use) cash:
Accounts receivable								1,034				5,001	(18,333)	9,864	(86,056)	11,625	(15,701)	10,594	(14,666)
Inventory								(20,581)				(17,716)	(37,983)	(25,431)	(57,615)	(32,843)	(63,389)	(24,633)	19,193
Prepaid expenses and other assets								(10,794)				1,018	(11,887)	(460)	(4,956)	427	(18,401)	(8,110)	(4,654)
Accounts payable, accrued expenses, and other liabilities								(3,374)				(2,887)	3,903	662	41,125	10,164	51,880	17,234	(10,160)
Deferred revenue								(620)				(2,459)	2,392	(3,705)	16,709	(5,868)	20,914	(4,700)	6,322
Net cash used in operating activities								(60,402)				(35,699)	(111,891)	(48,328)	(156,506)	(54,141)	(155,476)	(53,324)	(58,350)
Investing Activities
Purchases of property, plant and equipment								(2,507)				(1,468)	(5,009)	(2,844)	(11,265)	(4,635)	(22,526)	(5,683)	(5,142)
Purchases of equipment related to PPA and equipment related to fuel delivered to customers								(3,848)				(806)	(6,256)	(1,987)	(13,699)	(2,851)	(25,738)	(6,532)	(13,501)
Purchase of intangible assets														(1,860)	(1,638)	(1,860)	(1,957)	(2,404)	(929)
Proceeds from sale of leased assets														375		375		375
Net cash used in investing activities								(6,355)				(2,274)	(56,551)	(6,316)	(71,715)	(8,971)	(95,334)	(14,244)	(19,572)
Financing Activities
Proceeds from issuance of preferred stock, net of transaction costs												(3)		(8)		(37)		14,089	30,934
Proceeds from public offerings, net of transaction costs	$ 927,300	$ 344,400	$ 120,400	$ 23,500								23,498	(269)	28,265	344,398	38,098	1,271,714	158,343	7,195
Proceeds from exercise of stock options								6,104				81	15,798	205	23,335	(116)	32,023	1,217	138
Payments for redemption of preferred stock																(4,040)		(4,040)
Proceeds from issuance of convertible senior notes, net													205,100		205,098	39,052	205,098	39,052	95,856
Repurchase of convertible senior notes													(90,238)		(90,238)		(90,238)
Purchase of capped calls and common stock forward													(16,253)		(16,253)		(16,253)		(43,500)
Proceeds from termination of capped calls													24,158		24,158		24,158
Principal payments on long-term debt								(5,315)				(17,671)	(21,626)	(18,039)	(27,845)	(21,704)	(48,020)	(25,345)	(16,190)
Proceeds from long-term debt, net												84,761	49,000	99,546	99,000	99,496	99,000	119,186
Proceeds from sale/leaseback transaction accounted for as finance obligations																		83,668	76,175
Repayments of finance obligations								(5,343)				(53,580)	(11,129)	(55,712)	(19,038)	(56,603)	(27,212)	(59,196)	(30,531)
Proceeds from finance obligations								9,024					27,678	25,609	47,568	57,249	65,259	83,668	76,175
Net cash provided by financing activities								4,470				37,086	182,219	79,866	590,183	151,395	1,515,529	326,974	120,077
Effect of exchange rate changes on cash								1				(35)	(24)	(48)	(90)	(119)	65	(59)	(57)
Increase in cash, cash equivalents and restricted cash								(62,286)				(922)	13,753	25,174	361,872	88,164	1,264,784	259,347	42,098
Cash, cash equivalents, and restricted cash beginning of period					$ 731,372	383,253	307,214	369,500	198,317	135,327	109,231	110,153	369,500	110,153	369,500	110,153	369,500	110,153	68,055
Cash, cash equivalents, and restricted cash end of period			369,500	109,231	1,634,284	731,372	383,253	307,214	369,500	198,317	135,327	109,231	383,253	135,327	731,372	198,317	1,634,284	369,500	110,153
Supplemental disclosure of cash flow information
Cash paid for interest								5,155				4,858	9,466	8,673	16,975	8,673	28,942	19,180	13,057
Summary of non-cash investing and financing activity
Recognition of right of use assets								340				2,000	6,836	11,689	25,857	29,903	55,651	52,924	41,679
Net transfers between inventory and long-lived assets																			18,175
Conversion of preferred stock to common stock								441					441		43,058	1,883	1,179	28,392
As previously Reported
Operating Activities
Net loss attributable to the Company						(39,379)	(8,656)	(37,479)	(18,275)	(18,144)	(18,094)	(30,952)	(46,135)	(49,046)	(85,514)	(67,190)		(85,465)	(78,115)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation of long-lived assets								2,850				2,776	5,783	5,496	9,381	8,944		11,989	11,014
Amortization of intangible assets								175				175	398	338	835	518		698	693
Stock-based compensation								3,045				2,497	6,188	5,123	9,258	7,927		10,890	8,771
(Gain) loss on extinguishment of debt							(13,222)			518			(13,222)		(13,222)	518
Provision for bad debts and other assets												307		907		1,253		1,981	1,626
Amortization of debt issuance costs and discount on convertible senior notes								2,716				2,469	6,528	4,340	12,183	6,257		8,821	6,347
Provision for common stock warrants								2,566				1,193	7,983	2,209	25,198	3,706		6,513	10,190
Loss on disposal of leased assets														212		212		212
Fair value adjustment to contingent consideration															1,130
Change in fair value of common stock warrant liability						1,130			(72)	(427)	(1,706)	2,126		420	1,130	(7)		(79)	(4,286)
Deferred income tax benefit						(6,523)	(17,659)						(17,659)		(24,182)				(9,217)
Loss (benefit) on service contracts															4,306
Changes in operating assets and liabilities that provide (use) cash:
Accounts receivable								1,011				4,978	(18,393)	9,848	(86,004)	11,702		10,646	(14,398)
Inventory								(20,581)				(17,564)	(37,983)	(25,280)	(57,718)	(32,691)		(24,481)	19,041
Prepaid expenses and other assets								(10,794)				1,018	(11,817)	(460)	(4,956)	427		(8,110)	(4,654)
Accounts payable, accrued expenses, and other liabilities								(2,933)				(2,781)	4,699	1,232	35,748	13,293		19,879	(10,266)
Deferred revenue								(591)				(2,505)	2,383	(3,827)	16,647	(6,152)		(5,016)	5,637
Net cash used in operating activities								(60,015)				(36,263)	(111,247)	(48,488)	(156,910)	(51,801)		(51,522)	(57,617)
Investing Activities
Purchases of property, plant and equipment								(2,507)				(1,468)	(5,009)	(2,844)	(11,265)	(4,635)		(5,683)	(5,142)
Purchases of equipment related to PPA and equipment related to fuel delivered to customers								(3,848)				(806)	(6,256)	(1,987)	(13,699)	(2,851)		(6,532)	(13,501)
Purchase of intangible assets														(1,860)	(1,638)	(1,860)		(2,404)	(929)
Proceeds from sale of leased assets														375		375		375
Net cash used in investing activities								(6,355)				(2,274)	(56,551)	(6,316)	(71,715)	(8,971)		(14,244)	(19,572)
Financing Activities
Proceeds from issuance of preferred stock, net of transaction costs												(3)		(8)		(37)		14,089	30,934
Proceeds from public offerings, net of transaction costs												23,498	(269)	28,265	344,398	38,098		158,428	7,195
Proceeds from exercise of stock options								6,104				81	15,798	205	23,335	(116)		1,217	138
Payments for redemption of preferred stock																(4,040)		(4,040)
Proceeds from issuance of convertible senior notes, net													205,100		205,098	39,052		39,052	95,856
Repurchase of convertible senior notes													(90,238)		(90,238)
Purchase of capped calls and common stock forward													(16,253)		(16,253)				(43,500)
Proceeds from termination of capped calls													24,158		24,158
Principal payments on long-term debt								(5,315)				(17,153)	(21,626)	(17,521)	(27,845)	(21,186)		(24,827)	(16,190)
Proceeds from long-term debt, net												84,761	49,000	99,546	99,000	99,496		119,186
Proceeds from sale/leaseback transaction accounted for as finance obligations																		83,668	76,175
Repayments of finance obligations								(5,730)				(53,534)	(11,783)	(56,070)	(18,634)	(59,461)		(61,713)	(31,264)
Proceeds from finance obligations								9,024					27,678	25,609	47,568	57,249
Net cash provided by financing activities								4,083				37,650	181,565	80,026	590,587	149,055		325,060	119,344
Effect of exchange rate changes on cash								1				(35)	(14)	(48)	(90)	(119)		53	(57)
Increase in cash, cash equivalents and restricted cash								(62,286)				(922)	13,753	25,174	361,872	88,164		259,347	42,098
Cash, cash equivalents, and restricted cash beginning of period					$ 731,372	383,253	307,214	369,500	198,317	135,327	109,231	110,153	369,500	110,153	369,500	110,153	$ 369,500	110,153	68,055
Cash, cash equivalents, and restricted cash end of period			$ 369,500	$ 109,231		731,372	383,253	307,214	369,500	198,317	135,327	109,231	383,253	135,327	731,372	198,317		369,500	110,153
Supplemental disclosure of cash flow information
Cash paid for interest								5,155				4,858	9,466	8,673	16,975	8,673		19,180	13,057
Summary of non-cash investing and financing activity
Recognition of right of use assets								6,189					26,922	34,530	56,377	78,626		127,370	79,057
Conversion of preferred stock to common stock								441					441		42,873	1,883		28,392
Restatement Adjustments
Operating Activities
Net loss attributable to the Company						(25,838)	(745)	47	$ 239	$ 322	$ 756	405	(698)	1,161	(26,536)	1,483		1,722	(7,493)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation of long-lived assets								141				(28)	286	(63)	479	(86)		(51)	818
(Gain) loss on extinguishment of debt												518		518		518		518
Amortization of debt issuance costs and discount on convertible senior notes																185		185
Loss on disposal of leased assets								(128)
Change in fair value of common stock warrant liability						(1,130)									(1,130)
Deferred income tax benefit						$ (121)	$ 288						288		167				(78)
Loss (benefit) on service contracts												(142)	277	(873)	20,804	(1,366)		(1,643)	5,345
Changes in operating assets and liabilities that provide (use) cash:
Accounts receivable								23				23	60	16	(52)	(77)		(52)	(268)
Inventory												(152)		(151)	103	(152)		(152)	152
Prepaid expenses and other assets													(70)
Accounts payable, accrued expenses, and other liabilities								(441)				(106)	(796)	(570)	5,377	(3,129)		(2,645)	106
Deferred revenue								(29)				46	9	122	62	284		316	685
Net cash used in operating activities								(387)				564	(644)	160	404	(2,340)		(1,802)	(733)
Financing Activities
Proceeds from public offerings, net of transaction costs																		(85)
Principal payments on long-term debt												(518)		(518)		(518)		(518)
Repayments of finance obligations								387				(46)	654	358	(404)	2,858		2,517	733
Net cash provided by financing activities								387				(564)	654	(160)	(404)	2,340		1,914	733
Effect of exchange rate changes on cash													(10)					(112)
Summary of non-cash investing and financing activity
Recognition of right of use assets								$ (5,849)				$ 2,000	$ (20,086)	$ (22,841)	(30,520)	$ (48,723)		$ (74,446)	$ (37,378)
Conversion of preferred stock to common stock															$ 185

Unaudited Quarterly Financial_3

Unaudited Quarterly Financial data and Restatement of Previously Issued Unaudited Interim Condensed Consolidated Financial Statements - Consolidated Balance Sheets (Details) - USD ($)	Dec. 31, 2020	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Current assets:
Cash and cash equivalents	$ 1,312,404,000	$ 448,140,000	$ 152,492,000	$ 74,340,000	$ 139,496,000	$ 43,275,000	$ 19,845,000	$ 39,336,000
Restricted cash	64,041,000	55,704,000	50,634,000	56,804,000	54,813,000	35,720,000	19,400,000	19,297,000
Accounts receivable	43,041,000	113,505,000	45,782,000	24,734,000	25,768,000	24,737,000	26,844,000	32,307,000
Inventory	139,386,000	134,203,000	114,571,000	92,972,000	72,391,000	80,601,000	73,190,000	65,474,000
Prepaid expenses and other current assets	44,324,000	26,731,000	31,436,000	28,500,000	21,192,000	12,804,000	14,001,000	10,296,000
Total current assets	1,603,196,000	778,283,000	394,915,000	277,350,000	313,660,000	197,137,000	153,280,000	166,710,000
Restricted cash	257,839,000	227,528,000	180,127,000	176,070,000	175,191,000	119,322,000	96,082,000	50,598,000
Property, plant, and equipment, net	74,549,000	64,820,000	60,018,000	16,591,000	14,959,000	14,990,000	14,228,000	13,615,000
Right of use assets related to finance leases, net	5,724,000	2,335,000	2,389,000	1,707,000	1,714,000	1,720,000	1,726,000	1,733,000
Right of use assets related to operating leases, net	117,016,000	90,184,000	71,789,000	64,812,000	63,266,000	47,016,000	39,679,000	33,599,000
Equipment related to power purchase agreements and fuel delivered to customers, net	75,807,000	71,891,000	68,428,000	68,402,000	67,769,000	67,248,000	68,982,000	70,928,000
Goodwill	72,387,000	71,822,000	70,262,000	8,673,000	8,842,000	8,606,000	8,961,000	8,886,000
Intangible assets, net	39,251,000	39,569,000	38,974,000	5,696,000	5,539,000	5,113,000	5,398,000	3,677,000
Other assets	5,513,000	9,661,000	11,817,000	12,059,000	8,573,000	9,152,000	8,842,000	11,069,000
Total assets	2,251,282,000	1,356,093,000	898,719,000	631,360,000	659,513,000	470,304,000	397,178,000	360,815,000
Current liabilities:
Accounts payable	50,198,000	58,793,000	39,812,000	35,503,000	40,376,000	36,851,000	36,946,000	31,688,000
Accrued expenses	46,083,000	37,948,000	23,917,000	14,870,000	14,409,000	9,457,000	4,522,000	6,509,000
Deferred revenue	23,275,000	17,226,000	14,902,000	11,557,000	11,691,000	11,480,000	11,730,000	11,736,000
Operating lease liabilities	14,314,000	10,609,000	9,453,000	8,959,000	9,428,000	8,666,000	7,512,000	7,042,000
Finance lease liabilities	903,000	374,000	345,000	204,000	226,000	310,000	266,000	236,000
Finance obligations	32,717,000	31,349,000	28,794,000	26,209,000	24,667,000	20,469,000	12,455,000	11,028,000
Current portion of long-term debt	25,389,000	74,829,000	50,933,000	27,819,000	26,461,000	17,202,000	15,928,000	12,559,000
Other current liabilities	29,487,000	21,083,000	19,418,000	8,446,000	6,704,000	8,373,000	3,705,000	3,745,000
Total current liabilities	222,366,000	252,211,000	187,574,000	133,567,000	133,962,000	112,808,000	93,064,000	84,543,000
Deferred revenue	32,944,000	29,511,000	24,848,000	22,684,000	23,170,000	22,213,000	24,126,000	25,366,000
Operating lease liabilities	99,624,000	74,422,000	58,410,000	52,165,000	50,937,000	36,599,000	30,631,000	25,657,000
Finance lease liabilities	4,493,000	2,384,000	2,465,000	1,953,000	2,011,000	2,068,000	2,123,000	2,142,000
Common stock warrant liability						98,000	525,000	2,231,000
Finance obligations	148,836,000	140,662,000	131,653,000	121,322,000	119,422,000	99,669,000	76,916,000	54,864,000
Convertible senior notes, net	85,640,000	105,088,000	142,889,000	113,063,000	110,431,000	107,945,000	66,844,000	65,025,000
Long-term debt	150,013,000	120,380,000	101,844,000	79,119,000	85,708,000	78,840,000	83,776,000	72,676,000
Other liabilities	40,447,000	45,170,000	14,476,000	2,386,000	2,818,000	2,834,000	3,333,000	3,746,000
Total liabilities	784,363,000	769,828,000	664,159,000	526,259,000	528,459,000	463,074,000	381,338,000	336,250,000
Redeemable preferred stock:
Preferred stock						0.01
Stockholders' equity:
Common stock, $.01 par value	4,740,000	4,061,000	3,482,000	3,222,000	3,186,000	2,540,000	2,470,000	2,445,000
Additional paid-in capital	3,446,650,000	2,083,169,000	1,658,438,000	1,519,094,000	1,506,953,000	1,340,781,000	1,325,381,000	1,316,815,000
Accumulated other comprehensive income	2,451,000	1,846,000	1,159,000	1,052,000	1,288,000	929,000	1,460,000	1,374,000
Accumulated deficit	(1,946,488,000)	(1,462,377,000)	(1,397,160,000)	(1,387,752,000)	(1,350,307,000)	(1,332,259,000)	(1,314,425,000)	(1,297,072,000)
Less common stock in treasury	(40,434,000)	(40,434,000)	(31,359,000)	(31,224,000)	(31,216,000)	(31,216,000)	(30,681,000)	(30,637,000)
Total stockholders' equity	1,466,919,000	586,265,000	234,560,000	104,392,000	129,904,000	(19,225,000)	(15,795,000)	(7,075,000)	$ (3,588,000)	$ 70,229,000
Total liabilities, redeemable preferred stock, and stockholders' equity	$ 2,251,282,000	1,356,093,000	898,719,000	631,360,000	659,513,000	470,304,000	397,178,000	360,815,000
As previously Reported
Current assets:
Cash and cash equivalents		448,140,000	152,492,000	74,340,000	139,496,000	43,275,000	19,845,000	39,336,000
Restricted cash		55,704,000	50,634,000	56,804,000	54,813,000	35,720,000	19,400,000	19,297,000
Accounts receivable		113,133,000	45,522,000	24,437,000	25,448,000	24,392,000	26,592,000	32,062,000
Inventory		134,306,000	114,571,000	92,972,000	72,391,000	80,601,000	73,190,000	65,474,000
Prepaid expenses and other current assets		26,731,000	31,436,000	28,500,000	21,192,000	12,804,000	14,001,000	10,296,000
Total current assets		778,014,000	394,655,000	277,053,000	313,340,000	196,792,000	153,028,000	166,465,000
Restricted cash		227,528,000	180,127,000	176,070,000	175,191,000	119,322,000	96,082,000	50,598,000
Property, plant, and equipment, net		64,820,000	60,018,000	16,591,000	14,959,000	14,990,000	14,228,000	13,615,000
Equipment related to power purchase agreements and fuel delivered to customers, net		309,475,000	274,721,000	252,802,000	244,740,000	202,034,000	170,455,000	141,889,000
Goodwill		71,962,000	70,402,000	8,673,000	8,842,000	8,606,000	8,961,000	8,886,000
Intangible assets, net		39,169,000	38,574,000	5,296,000	5,539,000	5,113,000	5,398,000	3,677,000
Other assets		9,661,000	11,817,000	12,059,000	8,573,000	9,152,000	8,842,000	11,069,000
Total assets		1,500,629,000	1,030,314,000	748,544,000	771,184,000	556,009,000	456,994,000	396,199,000
Current liabilities:
Accounts payable		58,793,000	39,812,000	35,503,000	40,376,000	36,851,000	36,946,000	31,688,000
Accrued expenses		32,031,000	23,320,000	14,273,000	14,213,000	9,457,000	4,522,000	6,509,000
Deferred revenue		17,226,000	14,902,000	11,557,000	11,691,000	11,480,000	11,730,000	11,736,000
Finance obligations		63,692,000	57,695,000	52,047,000	49,507,000	41,112,000	30,663,000	23,997,000
Current portion of long-term debt		74,829,000	50,933,000	27,819,000	26,461,000	17,202,000	15,928,000	12,559,000
Other current liabilities		17,280,000	21,692,000	10,423,000	8,543,000	10,238,000	3,017,000	2,271,000
Total current liabilities		263,851,000	208,354,000	151,622,000	150,791,000	126,340,000	102,806,000	88,760,000
Deferred revenue		29,648,000	25,038,000	22,912,000	23,369,000	22,444,000	24,519,000	25,835,000
Common stock warrant liability						98,000	525,000	2,231,000
Finance obligations		337,150,000	300,653,000	272,171,000	265,228,000	208,465,000	157,531,000	111,195,000
Convertible senior notes, net		105,088,000	142,704,000	112,878,000	110,246,000	107,760,000	66,844,000	65,025,000
Long-term debt		120,380,000	101,844,000	79,119,000	85,708,000	78,840,000	83,776,000	72,676,000
Other liabilities		27,068,000	11,756,000	13,000	13,000	13,000	13,000	17,000
Total liabilities		883,185,000	790,349,000	638,715,000	635,355,000	543,960,000	436,014,000	365,739,000
Stockholders' equity:
Common stock, $.01 par value		4,061,000	3,482,000	3,222,000	3,186,000	2,540,000	2,470,000	2,445,000
Additional paid-in capital		2,083,199,000	1,658,532,000	1,519,257,000	1,507,116,000	1,340,859,000	1,325,459,000	1,316,893,000
Accumulated other comprehensive income		1,958,000	1,271,000	1,164,000	1,400,000	929,000	1,460,000	1,374,000
Accumulated deficit		(1,431,340,000)	(1,391,961,000)	(1,383,299,000)	(1,345,807,000)	(1,327,518,000)	(1,309,363,000)	(1,291,255,000)
Less common stock in treasury		(40,434,000)	(31,359,000)	(31,224,000)	(31,216,000)	(31,216,000)	(30,681,000)	(30,637,000)
Total stockholders' equity		617,444,000	239,965,000	109,120,000	134,679,000	(14,406,000)	(10,655,000)	(1,180,000)	2,713,000	73,646,000
Total liabilities, redeemable preferred stock, and stockholders' equity		1,500,629,000	1,030,314,000	748,544,000	771,184,000	556,009,000	456,994,000	396,199,000
Restatement Adjustments
Current assets:
Accounts receivable		372,000	260,000	297,000	320,000	345,000	252,000	245,000
Inventory		(103,000)
Total current assets		269,000	260,000	297,000	320,000	345,000	252,000	245,000
Right of use assets related to finance leases, net		2,335,000	2,389,000	1,707,000	1,714,000	1,720,000	1,726,000	1,733,000
Right of use assets related to operating leases, net		90,184,000	71,789,000	64,812,000	63,266,000	47,016,000	39,679,000	33,599,000
Equipment related to power purchase agreements and fuel delivered to customers, net		(237,584,000)	(206,293,000)	(184,400,000)	(176,971,000)	(134,786,000)	(101,473,000)	(70,961,000)
Goodwill		(140,000)	(140,000)
Intangible assets, net		400,000	400,000	400,000
Total assets		(144,536,000)	(131,595,000)	(117,184,000)	(111,671,000)	(85,705,000)	(59,816,000)	(35,384,000)
Current liabilities:
Accrued expenses		5,917,000	597,000	597,000	196,000
Operating lease liabilities		10,609,000	9,453,000	8,959,000	9,428,000	8,666,000	7,512,000	7,042,000
Finance lease liabilities		374,000	345,000	204,000	226,000	310,000	266,000	236,000
Finance obligations		(32,343,000)	(28,901,000)	(25,838,000)	(24,840,000)	(20,643,000)	(18,208,000)	(12,969,000)
Other current liabilities		3,803,000	(2,274,000)	(1,977,000)	(1,839,000)	(1,865,000)	688,000	1,474,000
Total current liabilities		(11,640,000)	(20,780,000)	(18,055,000)	(16,829,000)	(13,532,000)	(9,742,000)	(4,217,000)
Deferred revenue		(137,000)	(190,000)	(228,000)	(199,000)	(231,000)	(393,000)	(469,000)
Operating lease liabilities		74,422,000	58,410,000	52,165,000	50,937,000	36,599,000	30,631,000	25,657,000
Finance lease liabilities		2,384,000	2,465,000	1,953,000	2,011,000	2,068,000	2,123,000	2,142,000
Finance obligations		(196,488,000)	(169,000,000)	(150,849,000)	(145,806,000)	(108,796,000)	(80,615,000)	(56,331,000)
Convertible senior notes, net			185,000	185,000	185,000	185,000
Other liabilities		18,102,000	2,720,000	2,373,000	2,805,000	2,821,000	3,320,000	3,729,000
Total liabilities		(113,357,000)	(126,190,000)	(112,456,000)	(106,896,000)	(80,886,000)	(54,676,000)	(29,489,000)
Stockholders' equity:
Additional paid-in capital		(30,000)	(94,000)	(163,000)	(163,000)	(78,000)	(78,000)	(78,000)
Accumulated other comprehensive income		(112,000)	(112,000)	(112,000)	(112,000)
Accumulated deficit		(31,037,000)	(5,199,000)	(4,453,000)	(4,500,000)	(4,741,000)	(5,062,000)	(5,817,000)
Total stockholders' equity		(31,179,000)	(5,405,000)	(4,728,000)	(4,775,000)	(4,819,000)	(5,140,000)	(5,895,000)	$ (6,301,000)	$ (3,417,000)
Total liabilities, redeemable preferred stock, and stockholders' equity		$ (144,536,000)	$ (131,595,000)	(117,184,000)	(111,671,000)	(85,705,000)	(59,816,000)	(35,384,000)
Series C Redeemable Convertible Preferred Stock
Redeemable preferred stock:
Preferred stock				709,000	709,000	709,000	709,000	709,000
Series C Redeemable Convertible Preferred Stock | As previously Reported
Redeemable preferred stock:
Preferred stock				$ 709,000	709,000	709,000	709,000	709,000
Series E Redeemable Convertible Preferred Stock
Redeemable preferred stock:
Preferred stock					441,000	25,746,000	30,926,000	30,931,000
Series E Redeemable Convertible Preferred Stock | As previously Reported
Redeemable preferred stock:
Preferred stock					$ 441,000	$ 25,746,000	$ 30,926,000	$ 30,931,000

Unaudited Quarterly Financial_4

Unaudited Quarterly Financial data and Restatement of Previously Issued Unaudited Interim Condensed Consolidated Financial Statements - Consolidated Balance Sheets (Narrative) (Details) - USD ($) $ / shares in Units, $ in Thousands	Dec. 31, 2020	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Common stock, par value (in dollars per share)	$ 0.01	$ 0.01	$ 0.01	$ 0.01	$ 0.01	$ 0.01	$ 0.01	$ 0.01
Series C Redeemable Convertible Preferred Stock
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Redeemable convertible Preferred Stock, par value (in dollars per share)	$ 0.01			$ 0.01	$ 0.01	$ 0.01	$ 0.01	$ 0.01
Redeemable convertible Preferred Stock, shares authorized	10,431			10,431,000	10,431	10,431,000	10,431,000	10,431,000
Redeemable convertible Preferred Stock, shares issued	0			2,620,000	2,620	2,620,000	2,620,000	2,620,000
Redeemable convertible Preferred Stock, shares outstanding	0			2,620,000	2,620	2,620,000	2,620,000	2,620,000
Redeemable convertible Preferred Stock, aggregate involuntary liquidation preference (in dollars)	$ 16,664			$ 16,664	$ 16,664		$ 16,664	$ 16,664
Series E Redeemable Convertible Preferred Stock
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Redeemable convertible Preferred Stock, par value (in dollars per share)					$ 0.01	$ 0.01	$ 0.01	$ 0.01
Redeemable convertible Preferred Stock, shares authorized					35,000,000	35,000,000	35,000,000	35,000,000
Redeemable convertible Preferred Stock, shares issued					500,000	28,269,000	35,000,000	35,000,000
Redeemable convertible Preferred Stock, shares outstanding					500,000	28,269,000	35,000,000
Redeemable convertible Preferred Stock, aggregate involuntary liquidation preference (in dollars)							$ 35,000	$ 35,000

Unaudited Quarterly Financial_5

Unaudited Quarterly Financial data and Restatement of Previously Issued Unaudited Interim Condensed Consolidated Financial Statements - Consolidated Statements of Income (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended								6 Months Ended		9 Months Ended		12 Months Ended
	Dec. 31, 2020	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Jun. 30, 2020	Jun. 30, 2019	Sep. 30, 2020	Sep. 30, 2019	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Net revenue:
Net revenue	$ 309,099	$ 107,048	$ 67,995	$ 40,819	$ 91,607	$ 59,392	$ 57,466	$ 21,510		$ 78,976		$ 138,368
Net revenue		107,048	67,995	40,819	91,607				$ 108,814		$ 215,862		$ (93,237)	$ 229,975	$ 174,215
Cost of revenue:
Total cost of revenue		135,632	68,010	50,522	83,861	54,892	51,324	29,250	118,532	80,574	254,164	135,466	376,179	219,327	200,219
Gross (loss) profit	(431,114)	(28,584)	(15)	(9,703)	7,746	4,500	6,142	(7,740)	(9,718)	(1,598)	(38,302)	2,902	(469,416)	10,648	(26,004)
Operating expenses:
Research and development		7,386	4,873	4,774	4,882	3,563	3,608	3,006	9,647	6,614	17,033	10,177	27,848	15,059	12,750
Selling, general and administrative		17,210	21,644	11,109	9,973	10,395	13,613	9,221	32,753	22,834	49,963	33,229	79,348	43,202	37,685
Change in fair value of contingent consideration		1,130									1,130		1,160
Total operating expenses	46,660	25,726	26,517	15,883	14,855	13,958	17,221	12,227	42,400	29,448	68,126	43,406	114,786	58,261	50,435
Operating loss	(477,774)	(54,310)	(26,532)	(25,586)	(7,109)	(9,458)	(11,079)	(19,967)	(52,118)	(31,046)	(106,428)	(40,504)	(584,202)	(47,613)	(76,439)
Interest and other expense, net		(17,551)	(13,462)	(11,846)	(10,999)	(8,273)	(7,965)	(8,454)	(25,308)	(16,419)	(42,859)	(24,692)	(60,484)	(35,691)	(22,750)
Change in fair value of common stock warrant liability					72	427	1,706	(2,126)		(420)		7		79	4,286
Gain (loss) on extinguishment of debt			13,222			(518)		(518)	13,222	(518)	13,222	(518)	17,686	(518)
Loss before income taxes		(71,861)	(26,772)	(37,432)	(18,036)	(17,822)	(17,338)	(30,547)	(64,204)	(47,885)	(136,065)	(65,707)	(627,000)	(83,743)	(94,903)
Income tax benefit		6,644	17,371						17,371		24,015		30,845		9,295
Net loss attributable to the Company		(65,217)	(9,401)	(37,432)	(18,036)	(17,822)	(17,338)	(30,547)	(46,833)	(47,885)	(112,050)	(65,707)	(596,155)	(83,743)	(85,608)
Preferred stock dividends declared, deemed dividends and accretion of discount			(13)	(13)	(1,241)	(544)	(13)	(13)	(26)	(26)	(26)	(570)	(26)	(1,812)	(52)
Net loss attributable to common shareholders	$ (484,105)	$ (65,217)	$ (9,414)	$ (37,445)	$ (19,277)	$ (18,366)	$ (17,351)	$ (30,560)	$ (46,859)	$ (47,911)	$ (112,076)	$ (66,277)	$ (596,181)	$ (85,555)	$ (85,660)
Net loss per share:
Basic and diluted	$ (1.35)	$ (0.18)	$ (0.03)	$ (0.12)	$ (0.07)	$ (0.08)	$ (0.08)	$ (0.14)	$ (0.15)	$ (0.21)	$ (0.34)	$ (0.29)	$ (1.68)	$ (0.36)	$ (0.39)
Weighted average number of common stock outstanding		371,010,544	316,645,050	305,192,201	260,053,150	236,759,521	231,114,868	220,605,068	310,918,626	225,899,224	330,949,265	229,519,323	354,790,106	237,152,780	218,882,337
Sales of fuel cell systems and related infrastructure
Net revenue:
Net revenue	$ (246,171)	$ 83,662	$ 47,746	$ 20,468	$ 69,785	$ 38,883	$ 38,702	$ 2,550	$ 68,214	$ 41,252	$ 151,876	$ 80,135	$ (94,295)	$ 149,920	$ 107,175
Cost of revenue:
Total cost of revenue		69,428	33,888	13,974	47,091	25,183	23,329	2,312	47,862	25,641	117,290	50,824	171,404	97,915	85,205
Services performed on fuel cell systems and related infrastructure
Net revenue:
Net revenue	(29,387)	6,829	6,236	6,521	7,328	6,205	5,341	6,343	12,757	11,684	19,586	17,889	(9,801)	25,217	22,002
Cost of revenue:
Total cost of revenue		9,180	7,773	10,347	11,606	7,802	8,383	6,791	18,120	15,174	27,300	22,976	42,524	34,582	32,271
Provision (benefit) for loss contracts related to service
Cost of revenue:
Total cost of revenue		25,147	706	95	13	206	363	162	801	201	25,948	407	35,473	394	5,345
Power Purchase Agreements
Net revenue:
Net revenue	6,991	6,629	6,579	6,421	6,664	6,520	6,334	6,035	13,000	12,369	19,629	18,889	26,620	25,553	22,569
Cost of revenue:
Total cost of revenue		14,744	14,504	14,771	12,301	10,814	8,829	9,833	29,275	18,662	44,019	29,476	64,640	41,777	41,361
Fuel delivered to customers
Net revenue:
Net revenue	(40,608)	9,831	7,372	7,333	7,779	7,649	7,089	6,582	14,705	13,671	24,536	21,320	(16,072)	29,099	22,469
Cost of revenue:
Total cost of revenue		17,002	11,076	11,254	12,800	11,149	11,146	10,152	22,330	21,298	39,332	32,447	61,815	45,247	36,037
Other
Net revenue:
Net revenue	$ 76	97	62	76	51	135			138		235	135	311	186
Cost of revenue:
Total cost of revenue		131	63	81	50	150			144		275	150	$ 323	200
As previously Reported
Net revenue:
Net revenue						59,461	57,535	21,579		79,114		138,575
Net revenue		106,989	68,070	40,813	91,664				108,883		215,872			230,239	174,632
Cost of revenue:
Total cost of revenue		108,279	62,994	45,284	78,882	51,114	46,914	25,363	108,278	72,277	216,557	123,391		202,273	172,010
Gross (loss) profit		(1,290)	5,076	(4,471)	12,782	8,347	10,621	(3,784)	605	6,837	(685)	15,184		27,966	2,622
Operating expenses:
Research and development		11,964	9,757	10,412	9,341	8,028	8,933	7,373	20,169	16,306	32,133	24,334		33,675	33,907
Selling, general and administrative		14,277	21,658	11,013	10,982	10,400	13,627	9,324	32,671	22,951	46,948	33,351		44,333	38,198
Total operating expenses		26,241	31,415	21,425	20,323	18,428	22,560	16,697	52,840	39,257	79,081	57,685		78,008	72,105
Operating loss		(27,531)	(26,339)	(25,896)	(7,541)	(10,081)	(11,939)	(20,481)	(52,235)	(32,420)	(79,766)	(42,501)		(50,042)	(69,483)
Interest and other expense, net		(17,241)	(13,198)	(11,583)	(10,806)	(7,972)	(7,861)	(8,345)	(24,781)	(16,206)	(42,022)	(24,178)		(35,502)	(22,135)
Change in fair value of common stock warrant liability		(1,130)			72	427	1,706	(2,126)		(420)	(1,130)	7		79	4,286
Gain (loss) on extinguishment of debt			13,222			(518)			13,222		13,222	(518)
Loss before income taxes		(45,902)	(26,315)	(37,479)	(18,275)	(18,144)	(18,094)	(30,952)	(63,794)	(49,046)	(109,696)	(67,190)		(85,465)	(87,332)
Income tax benefit		6,523	17,659						17,659		24,182				9,217
Net loss attributable to the Company		(39,379)	(8,656)	(37,479)	(18,275)	(18,144)	(18,094)	(30,952)	(46,135)	(49,046)	(85,514)	(67,190)		(85,465)	(78,115)
Preferred stock dividends declared, deemed dividends and accretion of discount			(13)	(13)	(13)	(13)	(13)	(52)	(19)	(26)	(19)	(39)		(52)	(52)
Net loss attributable to common shareholders		$ (39,379)	$ (8,669)	$ (37,492)	$ (18,288)	$ (18,157)	$ (18,107)	$ (31,004)	$ (46,154)	$ (49,072)	$ (85,533)	$ (67,229)		$ (85,517)	$ (78,167)
Net loss per share:
Basic and diluted		$ (0.11)	$ (0.03)	$ (0.12)	$ (0.07)	$ (0.08)	$ (0.08)	$ (0.14)	$ (0.15)	$ (0.22)	$ (0.26)	$ (0.29)		$ (0.36)	$ (0.36)
Weighted average number of common stock outstanding		371,010,544	316,645,050	305,192,201	260,053,150	236,759,521	231,114,868	220,605,068	310,918,626	225,899,224	330,949,265	229,519,323		237,152,780	218,882,337
As previously Reported | Sales of fuel cell systems and related infrastructure
Net revenue:
Net revenue		$ 83,528	$ 47,746	$ 20,387	$ 69,767	$ 38,877	$ 38,696	$ 2,544	$ 68,133	$ 41,240	$ 151,661	$ 80,117		$ 149,884	$ 107,292
Cost of revenue:
Total cost of revenue		68,509	33,676	13,744	46,419	24,990	23,129	2,321	47,420	25,450	115,929	50,440		96,859	84,439
As previously Reported | Services performed on fuel cell systems and related infrastructure
Net revenue:
Net revenue		6,829	6,236	6,521	7,328	6,205	5,341	6,343	12,757	11,684	19,586	17,889		25,217	22,002
Cost of revenue:
Total cost of revenue		7,074	6,491	8,181	9,999	6,461	6,218	6,123	14,672	12,341	21,746	18,802		28,801	23,698
As previously Reported | Provision (benefit) for loss contracts related to service
Cost of revenue:
Total cost of revenue		4,306									4,306
As previously Reported | Power Purchase Agreements
Net revenue:
Net revenue		6,704	6,654	6,496	6,739	6,595	6,409	6,110	13,150	12,519	19,854	19,114		25,853	22,869
Cost of revenue:
Total cost of revenue		14,087	13,704	14,243	11,992	10,353	8,713	8,998	27,947	17,711	42,034	28,064		40,056	36,161
As previously Reported | Fuel delivered to customers
Net revenue:
Net revenue		9,831	7,372	7,333	7,779	7,649	7,089	6,582	14,705	13,671	24,536	21,320		29,099	22,469
Cost of revenue:
Total cost of revenue		14,172	9,060	9,035	10,422	9,160	8,854	7,921	18,095	16,775	32,267	25,935		36,357	27,712
As previously Reported | Other
Net revenue:
Net revenue		97	62	76	51	135			138		235	135		186
Cost of revenue:
Total cost of revenue		131	63	81	50	150			144		275	150		200
Restatement Adjustments
Net revenue:
Net revenue						(69)	(69)	(69)		(138)		(207)
Net revenue		59	(75)	6	(57)				(69)		(10)			(264)	(417)
Cost of revenue:
Total cost of revenue		27,353	5,016	5,238	4,979	3,778	4,410	3,887	10,254	8,297	37,607	12,075		17,054	28,209
Gross (loss) profit		(27,294)	(5,091)	(5,232)	(5,036)	(3,847)	(4,479)	(3,956)	(10,323)	(8,435)	(37,617)	(12,282)		(17,318)	(28,626)
Operating expenses:
Research and development		(4,578)	(4,884)	(5,638)	(4,459)	(4,465)	(5,325)	(4,367)	(10,522)	(9,692)	(15,100)	(14,157)		(18,616)	(21,157)
Selling, general and administrative		2,933	(14)	96	(1,009)	(5)	(14)	(103)	82	(117)	3,015	(122)		(1,131)	(513)
Change in fair value of contingent consideration		1,130									1,130
Total operating expenses		(515)	(4,898)	(5,542)	(5,468)	(4,470)	(5,339)	(4,470)	(10,440)	(9,809)	(10,955)	(14,279)		(19,747)	(21,670)
Operating loss		(26,779)	(193)	310	432	623	860	514	117	1,374	(26,662)	1,997		2,429	(6,956)
Interest and other expense, net		(310)	(264)	(263)	(193)	(301)	(104)	(109)	(527)	(213)	(837)	(514)		(189)	(615)
Change in fair value of common stock warrant liability		1,130									1,130
Gain (loss) on extinguishment of debt								(518)		(518)		(518)		(518)
Loss before income taxes		(25,959)	(457)	47	239	322	756	405	(410)	1,161	(26,369)	1,483		1,722	(7,571)
Income tax benefit		121	(288)						(288)		(167)				78
Net loss attributable to the Company		(25,838)	(745)	47	239	322	756	405	(698)	1,161	(26,536)	1,483		1,722	(7,493)
Preferred stock dividends declared, deemed dividends and accretion of discount					(1,228)	(531)		39	(7)		(7)	(531)		(1,760)
Net loss attributable to common shareholders		(25,838)	(745)	47	(989)	(209)	756	444	(705)	1,161	(26,543)	952		(38)	(7,493)
Restatement Adjustments | Sales of fuel cell systems and related infrastructure
Net revenue:
Net revenue		134		81	18	6	6	6	81	12	215	18		36	(117)
Cost of revenue:
Total cost of revenue		919	212	230	672	193	200	(9)	442	191	1,361	384		1,056	766
Restatement Adjustments | Services performed on fuel cell systems and related infrastructure
Cost of revenue:
Total cost of revenue		2,106	1,282	2,166	1,607	1,341	2,165	668	3,448	2,833	5,554	4,174		5,781	8,573
Restatement Adjustments | Provision (benefit) for loss contracts related to service
Cost of revenue:
Total cost of revenue		20,841	706	95	13	206	363	162	801	201	21,642	407		394	5,345
Restatement Adjustments | Power Purchase Agreements
Net revenue:
Net revenue		(75)	(75)	(75)	(75)	(75)	(75)	(75)	(150)	(150)	(225)	(225)		(300)	(300)
Cost of revenue:
Total cost of revenue		657	800	528	309	461	116	835	1,328	951	1,985	1,412		1,721	5,200
Restatement Adjustments | Fuel delivered to customers
Net revenue:
Net revenue														8,846	8,325
Cost of revenue:
Total cost of revenue		$ 2,830	$ 2,016	$ 2,219	$ 2,378	$ 1,989	$ 2,292	$ 2,231	$ 4,235	$ 4,523	$ 7,065	$ 6,512		$ 8,890	$ 8,325

Unaudited Quarterly Financial_6

Unaudited Quarterly Financial data and Restatement of previously Issued Unaudited interim Condensed Consolidated Financial Statements - Consolidated Statements of Comprehensive Income (Details) - USD ($) $ in Thousands	3 Months Ended							6 Months Ended		9 Months Ended		12 Months Ended
	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Jun. 30, 2020	Jun. 30, 2019	Sep. 30, 2020	Sep. 30, 2019	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Net loss attributable to the Company	$ (65,217)	$ (9,401)	$ (37,432)	$ (18,036)	$ (17,822)	$ (17,338)	$ (30,547)	$ (46,833)	$ (47,885)	$ (112,050)	$ (65,707)	$ (596,155)	$ (83,743)	$ (85,608)
Other comprehensive gain (loss) - foreign currency translation adjustment	687	107	(236)	296	(531)	86	(210)	(129)	(124)	558	(655)	1,163	(296)	(610)
Comprehensive loss attributable to the Company	(64,530)	(9,294)	(37,668)	(17,740)	(18,353)	(17,252)	(30,757)	(46,962)	(48,009)	(111,492)	(66,362)	(594,992)	(84,039)	(86,218)
Preferred stock dividends declared, deemed dividends and accretion of discount		(13)	(13)	(1,241)	(544)	(13)	(13)	(26)	(26)	(26)	(570)	(26)	(1,812)	(52)
Comprehensive loss attributable to common stockholders	(64,530)	(9,307)	(37,681)	(18,981)	(18,897)	(17,265)	(30,770)	(46,988)	(48,035)	(111,518)	(66,932)	$ (595,018)	(85,851)	(86,270)
As previously Reported
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Net loss attributable to the Company	(39,379)	(8,656)	(37,479)	(18,275)	(18,144)	(18,094)	(30,952)	(46,135)	(49,046)	(85,514)	(67,190)		(85,465)	(78,115)
Other comprehensive gain (loss) - foreign currency translation adjustment	687	107	(236)		(531)	86	(210)	(129)	(124)	558	(655)		(184)	(610)
Comprehensive loss attributable to the Company	(38,692)	(8,549)	(37,715)		(18,675)	(18,008)	(31,162)	(46,264)	(49,170)	(84,956)	(67,845)		(85,649)	(78,725)
Preferred stock dividends declared, deemed dividends and accretion of discount		(13)	(13)	(13)	(13)	(13)	(52)	(19)	(26)	(19)	(39)		(52)	(52)
Comprehensive loss attributable to common stockholders	(38,692)	(8,562)	(37,728)		(18,688)	(18,021)	(31,214)	(46,283)	(49,196)	(84,975)	(67,884)		(85,701)	(78,777)
Restatement Adjustments
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Net loss attributable to the Company	(25,838)	(745)	47	239	322	756	405	(698)	1,161	(26,536)	1,483		1,722	$ (7,493)
Comprehensive loss attributable to the Company	(25,838)	(745)	47		322	756	405	(698)	1,161	(26,536)	1,483
Preferred stock dividends declared, deemed dividends and accretion of discount				$ (1,228)	(531)		39	(7)		(7)	(531)		$ (1,760)
Comprehensive loss attributable to common stockholders	$ (25,838)	$ (745)	$ 47		$ (209)	$ 756	$ 444	$ (705)	$ 1,161	$ (26,543)	$ 952

Unaudited Quarterly Financial_7

Unaudited Quarterly Financial data and Restatement of Previously Issued Unaudited interim Condensed Consolidated Financial Statements - Condensed Consolidated Statements of Stockholders' Equity (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018
Increase (Decrease) in Stockholders' Equity
Balance	$ 586,265	$ 234,560	$ 104,392	$ 129,904	$ (19,225)	$ (15,795)	$ (7,075)	$ (3,588)	$ 70,229
Balance (in shares)				318,637,560
Balance	$ 1,466,919	586,265	234,560	$ 104,392	$ 129,904	(19,225)	(15,795)	(7,075)	(3,588)
Balance (in shares)	473,977,469				318,637,560
As previously Reported
Increase (Decrease) in Stockholders' Equity
Balance	$ 617,444	239,965	109,120	134,679	$ (14,406)	(10,655)	(1,180)	2,713	73,646
Balance		617,444	239,965	109,120	134,679	(14,406)	(10,655)	(1,180)	2,713
Restatement Adjustments
Increase (Decrease) in Stockholders' Equity
Balance	(31,179)	(5,405)	(4,728)	(4,775)	(4,819)	(5,140)	(5,895)	(6,301)	(3,417)
Balance		(31,179)	(5,405)	(4,728)	(4,775)	(4,819)	(5,140)	(5,895)	(6,301)
Common Stock
Increase (Decrease) in Stockholders' Equity
Balance	$ 4,061	$ 3,482	$ 3,222	$ 3,186	$ 2,540	$ 2,470	$ 2,445	$ 2,342	$ 2,291
Balance (in shares)	406,123,816	348,201,792	322,220,469	318,637,560	253,982,578	246,975,173	244,537,235	234,160,661	229,073,517
Balance	$ 4,740	$ 4,061	$ 3,482	$ 3,222	$ 3,186	$ 2,540	$ 2,470	$ 2,445	$ 2,342
Balance (in shares)	473,977,469	406,123,816	348,201,792	322,220,469	318,637,560	253,982,578	246,975,173	244,537,235	234,160,661
Common Stock | As previously Reported
Increase (Decrease) in Stockholders' Equity
Balance	$ 4,061	$ 3,482	$ 3,222	$ 3,186	$ 2,540	$ 2,470	$ 2,445	$ 2,342	$ 2,291
Balance (in shares)	406,123,816	348,201,792	322,220,469	318,637,560	253,982,578	246,975,173	244,537,235	234,160,661	229,073,517
Balance		$ 4,061	$ 3,482	$ 3,222	$ 3,186	$ 2,540	$ 2,470	$ 2,445	$ 2,342
Balance (in shares)		406,123,816	348,201,792	322,220,469	318,637,560	253,982,578	246,975,173	244,537,235	234,160,661
Additional Paid-in-Capital
Increase (Decrease) in Stockholders' Equity
Balance	$ 2,083,169	$ 1,658,438	$ 1,519,094	$ 1,506,953	$ 1,340,781	$ 1,325,381	$ 1,316,815	$ 1,289,636	$ 1,250,899
Balance	3,446,650	2,083,169	1,658,438	1,519,094	1,506,953	1,340,781	1,325,381	1,316,815	1,289,636
Additional Paid-in-Capital | As previously Reported
Increase (Decrease) in Stockholders' Equity
Balance	2,083,199	1,658,532	1,519,257	1,507,116	1,340,859	1,325,459	1,316,893	1,289,714	1,250,899
Balance		2,083,199	1,658,532	1,519,257	1,507,116	1,340,859	1,325,459	1,316,893	1,289,714
Additional Paid-in-Capital | Restatement Adjustments
Increase (Decrease) in Stockholders' Equity
Balance	(30)	(94)	(163)	(163)	(78)	(78)	(78)	(78)
Balance		(30)	(94)	(163)	(163)	(78)	(78)	(78)	(78)
Accumulated Other Comprehensive Income
Increase (Decrease) in Stockholders' Equity
Balance	1,846	1,159	1,052	1,288	929	1,460	1,374	1,584	2,194
Balance	2,451	1,846	1,159	1,052	1,288	929	1,460	1,374	1,584
Accumulated Other Comprehensive Income | As previously Reported
Increase (Decrease) in Stockholders' Equity
Balance	1,958	1,271	1,164	1,400	929	1,460	1,374	1,584	2,194
Balance		1,958	1,271	1,164	1,400	929	1,460	1,374	1,584
Accumulated Other Comprehensive Income | Restatement Adjustments
Increase (Decrease) in Stockholders' Equity
Balance	(112)	(112)	(112)	(112)
Balance		(112)	(112)	(112)	(112)
Treasury Stock
Increase (Decrease) in Stockholders' Equity
Balance	$ (40,434)	$ (31,359)	$ (31,224)	$ (31,216)	$ (31,216)	$ (30,681)	$ (30,637)	$ (30,637)	$ (3,102)
Balance (in shares)	15,926,068	15,292,591	15,261,007	15,259,045	15,259,045	15,020,437	15,002,663	15,002,663	587,151
Balance	$ (40,434)	$ (40,434)	$ (31,359)	$ (31,224)	$ (31,216)	$ (31,216)	$ (30,681)	$ (30,637)	$ (30,637)
Balance (in shares)	15,926,068	15,926,068	15,292,591	15,261,007	15,259,045	15,259,045	15,020,437	15,002,663	15,002,663
Treasury Stock | As previously Reported
Increase (Decrease) in Stockholders' Equity
Balance	$ (40,434)	$ (31,359)	$ (31,224)	$ (31,216)	$ (31,216)	$ (30,681)	$ (30,637)	$ (30,637)	$ (3,102)
Balance (in shares)	15,926,068	15,292,591	15,261,007	15,259,045	15,259,045	15,020,437	15,002,663	15,002,663	587,151
Balance		$ (40,434)	$ (31,359)	$ (31,224)	$ (31,216)	$ (31,216)	$ (30,681)	$ (30,637)	$ (30,637)
Balance (in shares)		15,926,068	15,292,591	15,261,007	15,259,045	15,259,045	15,020,437	15,002,663	15,002,663
Accumulated Deficit
Increase (Decrease) in Stockholders' Equity
Balance	$ (1,462,377)	$ (1,397,160)	$ (1,387,752)	$ (1,350,307)	$ (1,332,259)	$ (1,314,425)	$ (1,297,072)	$ (1,266,513)	$ (1,182,053)
Balance	(1,946,488)	(1,462,377)	(1,397,160)	(1,387,752)	(1,350,307)	(1,332,259)	(1,314,425)	(1,297,072)	(1,266,513)
Accumulated Deficit | As previously Reported
Increase (Decrease) in Stockholders' Equity
Balance	(1,431,340)	(1,391,961)	(1,383,299)	(1,345,807)	(1,327,518)	(1,309,363)	(1,291,255)	(1,260,290)	(1,178,636)
Balance		(1,431,340)	(1,391,961)	(1,383,299)	(1,345,807)	(1,327,518)	(1,309,363)	(1,291,255)	(1,260,290)
Accumulated Deficit | Restatement Adjustments
Increase (Decrease) in Stockholders' Equity
Balance	$ (31,037)	(5,199)	(4,453)	(4,500)	(4,741)	(5,062)	(5,817)	(6,223)	(3,417)
Balance		$ (31,037)	$ (5,199)	$ (4,453)	$ (4,500)	$ (4,741)	$ (5,062)	$ (5,817)	$ (6,223)

Unaudited Quarterly Financial_8

Unaudited Quarterly Financial data and Restatement of Previously Issued Unaudited interim Condensed Consolidated Financial Statements - Consolidated Statements of Cash Flows (Details) - USD ($) $ in Thousands	1 Months Ended				3 Months Ended								6 Months Ended		9 Months Ended		12 Months Ended
	Nov. 30, 2020	Aug. 31, 2020	Dec. 31, 2019	Mar. 31, 2019	Dec. 31, 2020	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Jun. 30, 2020	Jun. 30, 2019	Sep. 30, 2020	Sep. 30, 2019	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Operating Activities
Net loss attributable to the Company						$ (65,217)	$ (9,401)	$ (37,432)	$ (18,036)	$ (17,822)	$ (17,338)	$ (30,547)	$ (46,833)	$ (47,885)	$ (112,050)	$ (65,707)	$ (596,155)	$ (83,743)	$ (85,608)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation of long-lived assets								2,991				2,748	6,069	5,433	9,860	8,858	14,434	11,938	11,832
Amortization of intangible assets								175				175	398	338	835	518	1,135	698	693
Stock-based compensation								3,045				2,497	6,188	5,123	9,258	7,927	17,135	10,890	8,771
(Gain) loss on extinguishment of debt							(13,222)			518		518	(13,222)	518	(13,222)	518	(17,686)	518
Provision for bad debts and other assets												307		907		1,253	700	1,981	1,626
Amortization of debt issuance costs and discount on convertible senior notes								2,716				2,469	6,528	4,340	12,183	6,442	17,061	9,006	6,347
Provision for common stock warrants								2,566				1,193	7,983	2,209	25,198	3,706	425,047	6,513	10,190
Loss on disposal of leased assets								(128)						212		212		212
Fair value adjustment to contingent consideration															1,130		(1,160)
Loss (benefit) on service contracts								(128)				(142)	277	(873)	25,110	(1,366)	33,125	(1,643)	5,345
Change in fair value of common stock warrant liability									(72)	(427)	(1,706)	2,126		420		(7)		(79)	(4,286)
Deferred income tax benefit						(6,644)	(17,371)						(17,371)		(24,015)		(30,845)		(9,295)
Changes in operating assets and liabilities that provide (use) cash:
Accounts receivable								1,034				5,001	(18,333)	9,864	(86,056)	11,625	(15,701)	10,594	(14,666)
Inventory								(20,581)				(17,716)	(37,983)	(25,431)	(57,615)	(32,843)	(63,389)	(24,633)	19,193
Prepaid expenses and other assets								(10,794)				1,018	(11,887)	(460)	(4,956)	427	(18,401)	(8,110)	(4,654)
Accounts payable, accrued expenses, and other liabilities								(3,374)				(2,887)	3,903	662	41,125	10,164	51,880	17,234	(10,160)
Deferred revenue								(620)				(2,459)	2,392	(3,705)	16,709	(5,868)	20,914	(4,700)	6,322
Net cash used in operating activities								(60,402)				(35,699)	(111,891)	(48,328)	(156,506)	(54,141)	(155,476)	(53,324)	(58,350)
Investing Activities
Purchases of property, plant and equipment								(2,507)				(1,468)	(5,009)	(2,844)	(11,265)	(4,635)	(22,526)	(5,683)	(5,142)
Purchase of intangible assets														(1,860)	(1,638)	(1,860)	(1,957)	(2,404)	(929)
Purchases of equipment related to PPA and equipment related to fuel delivered to customers								(3,848)				(806)	(6,256)	(1,987)	(13,699)	(2,851)	(25,738)	(6,532)	(13,501)
Net cash paid for acquisitions													(45,286)		(45,113)		(45,113)
Proceeds from sale of leased assets														375		375		375
Net cash used in investing activities								(6,355)				(2,274)	(56,551)	(6,316)	(71,715)	(8,971)	(95,334)	(14,244)	(19,572)
Financing Activities
Proceeds from issuance of preferred stock, net of transaction costs												(3)		(8)		(37)		14,089	30,934
Proceeds from public offerings, net of transaction costs	$ 927,300	$ 344,400	$ 120,400	$ 23,500								23,498	(269)	28,265	344,398	38,098	1,271,714	158,343	7,195
Proceeds from exercise of stock options								6,104				81	15,798	205	23,335	(116)	32,023	1,217	138
Payments for redemption of preferred stock																(4,040)		(4,040)
Proceeds from issuance of convertible senior notes, net													205,100		205,098	39,052	205,098	39,052	95,856
Repurchase of convertible senior notes													(90,238)		(90,238)		(90,238)
Purchase of capped calls and common stock forward													(16,253)		(16,253)		(16,253)		(43,500)
Proceeds from termination of capped calls													24,158		24,158		24,158
Principal payments on long-term debt								(5,315)				(17,671)	(21,626)	(18,039)	(27,845)	(21,704)	(48,020)	(25,345)	(16,190)
Proceeds from long-term debt, net												84,761	49,000	99,546	99,000	99,496	99,000	119,186
Repayments of finance obligations								(5,343)				(53,580)	(11,129)	(55,712)	(19,038)	(56,603)	(27,212)	(59,196)	(30,531)
Proceeds from finance obligations								9,024					27,678	25,609	47,568	57,249	65,259	83,668	76,175
Net cash provided by financing activities								4,470				37,086	182,219	79,866	590,183	151,395	1,515,529	326,974	120,077
Effect of exchange rate changes on cash								1				(35)	(24)	(48)	(90)	(119)	65	(59)	(57)
Increase in cash, cash equivalents and restricted cash								(62,286)				(922)	13,753	25,174	361,872	88,164	1,264,784	259,347	42,098
Cash, cash equivalents, and restricted cash beginning of period					$ 731,372	383,253	307,214	369,500	198,317	135,327	109,231	110,153	369,500	110,153	369,500	110,153	369,500	110,153	68,055
Cash, cash equivalents, and restricted cash end of period			369,500	109,231	1,634,284	731,372	383,253	307,214	369,500	198,317	135,327	109,231	383,253	135,327	731,372	198,317	1,634,284	369,500	110,153
Supplemental disclosure of cash flow information
Cash paid for interest								5,155				4,858	9,466	8,673	16,975	8,673	28,942	19,180	13,057
Summary of non-cash investing and financing activity
Recognition of right of use assets								340				2,000	6,836	11,689	25,857	29,903	55,651	52,924	41,679
Net transfers between inventory and long-lived assets																			18,175
Conversion of preferred stock to common stock								441					441		43,058	1,883	1,179	28,392
As previously Reported
Operating Activities
Net loss attributable to the Company						(39,379)	(8,656)	(37,479)	(18,275)	(18,144)	(18,094)	(30,952)	(46,135)	(49,046)	(85,514)	(67,190)		(85,465)	(78,115)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation of long-lived assets								2,850				2,776	5,783	5,496	9,381	8,944		11,989	11,014
Amortization of intangible assets								175				175	398	338	835	518		698	693
Stock-based compensation								3,045				2,497	6,188	5,123	9,258	7,927		10,890	8,771
(Gain) loss on extinguishment of debt							(13,222)			518			(13,222)		(13,222)	518
Provision for bad debts and other assets												307		907		1,253		1,981	1,626
Amortization of debt issuance costs and discount on convertible senior notes								2,716				2,469	6,528	4,340	12,183	6,257		8,821	6,347
Provision for common stock warrants								2,566				1,193	7,983	2,209	25,198	3,706		6,513	10,190
Loss on disposal of leased assets														212		212		212
Fair value adjustment to contingent consideration															1,130
Loss (benefit) on service contracts															4,306
Change in fair value of common stock warrant liability						1,130			(72)	(427)	(1,706)	2,126		420	1,130	(7)		(79)	(4,286)
Deferred income tax benefit						(6,523)	(17,659)						(17,659)		(24,182)				(9,217)
Changes in operating assets and liabilities that provide (use) cash:
Accounts receivable								1,011				4,978	(18,393)	9,848	(86,004)	11,702		10,646	(14,398)
Inventory								(20,581)				(17,564)	(37,983)	(25,280)	(57,718)	(32,691)		(24,481)	19,041
Prepaid expenses and other assets								(10,794)				1,018	(11,817)	(460)	(4,956)	427		(8,110)	(4,654)
Accounts payable, accrued expenses, and other liabilities								(2,933)				(2,781)	4,699	1,232	35,748	13,293		19,879	(10,266)
Deferred revenue								(591)				(2,505)	2,383	(3,827)	16,647	(6,152)		(5,016)	5,637
Net cash used in operating activities								(60,015)				(36,263)	(111,247)	(48,488)	(156,910)	(51,801)		(51,522)	(57,617)
Investing Activities
Purchases of property, plant and equipment								(2,507)				(1,468)	(5,009)	(2,844)	(11,265)	(4,635)		(5,683)	(5,142)
Purchase of intangible assets														(1,860)	(1,638)	(1,860)		(2,404)	(929)
Purchases of equipment related to PPA and equipment related to fuel delivered to customers								(3,848)				(806)	(6,256)	(1,987)	(13,699)	(2,851)		(6,532)	(13,501)
Net cash paid for acquisitions													(45,286)		(45,113)
Proceeds from sale of leased assets														375		375		375
Net cash used in investing activities								(6,355)				(2,274)	(56,551)	(6,316)	(71,715)	(8,971)		(14,244)	(19,572)
Financing Activities
Proceeds from issuance of preferred stock, net of transaction costs												(3)		(8)		(37)		14,089	30,934
Proceeds from public offerings, net of transaction costs												23,498	(269)	28,265	344,398	38,098		158,428	7,195
Proceeds from exercise of stock options								6,104				81	15,798	205	23,335	(116)		1,217	138
Payments for redemption of preferred stock																(4,040)		(4,040)
Proceeds from issuance of convertible senior notes, net													205,100		205,098	39,052		39,052	95,856
Repurchase of convertible senior notes													(90,238)		(90,238)
Purchase of capped calls and common stock forward													(16,253)		(16,253)				(43,500)
Proceeds from termination of capped calls													24,158		24,158
Principal payments on long-term debt								(5,315)				(17,153)	(21,626)	(17,521)	(27,845)	(21,186)		(24,827)	(16,190)
Proceeds from long-term debt, net												84,761	49,000	99,546	99,000	99,496		119,186
Repayments of finance obligations								(5,730)				(53,534)	(11,783)	(56,070)	(18,634)	(59,461)		(61,713)	(31,264)
Proceeds from finance obligations								9,024					27,678	25,609	47,568	57,249
Net cash provided by financing activities								4,083				37,650	181,565	80,026	590,587	149,055		325,060	119,344
Effect of exchange rate changes on cash								1				(35)	(14)	(48)	(90)	(119)		53	(57)
Increase in cash, cash equivalents and restricted cash								(62,286)				(922)	13,753	25,174	361,872	88,164		259,347	42,098
Cash, cash equivalents, and restricted cash beginning of period					$ 731,372	383,253	307,214	369,500	198,317	135,327	109,231	110,153	369,500	110,153	369,500	110,153	$ 369,500	110,153	68,055
Cash, cash equivalents, and restricted cash end of period			$ 369,500	$ 109,231		731,372	383,253	307,214	369,500	198,317	135,327	109,231	383,253	135,327	731,372	198,317		369,500	110,153
Supplemental disclosure of cash flow information
Cash paid for interest								5,155				4,858	9,466	8,673	16,975	8,673		19,180	13,057
Summary of non-cash investing and financing activity
Recognition of right of use assets								6,189					26,922	34,530	56,377	78,626		127,370	79,057
Conversion of preferred stock to common stock								441					441		42,873	1,883		28,392
Restatement Adjustments
Operating Activities
Net loss attributable to the Company						(25,838)	(745)	47	$ 239	$ 322	$ 756	405	(698)	1,161	(26,536)	1,483		1,722	(7,493)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation of long-lived assets								141				(28)	286	(63)	479	(86)		(51)	818
(Gain) loss on extinguishment of debt												518		518		518		518
Amortization of debt issuance costs and discount on convertible senior notes																185		185
Loss on disposal of leased assets								(128)
Loss (benefit) on service contracts												(142)	277	(873)	20,804	(1,366)		(1,643)	5,345
Change in fair value of common stock warrant liability						(1,130)									(1,130)
Deferred income tax benefit						$ (121)	$ 288						288		167				(78)
Changes in operating assets and liabilities that provide (use) cash:
Accounts receivable								23				23	60	16	(52)	(77)		(52)	(268)
Inventory												(152)		(151)	103	(152)		(152)	152
Prepaid expenses and other assets													(70)
Accounts payable, accrued expenses, and other liabilities								(441)				(106)	(796)	(570)	5,377	(3,129)		(2,645)	106
Deferred revenue								(29)				46	9	122	62	284		316	685
Net cash used in operating activities								(387)				564	(644)	160	404	(2,340)		(1,802)	(733)
Financing Activities
Proceeds from public offerings, net of transaction costs																		(85)
Principal payments on long-term debt												(518)		(518)		(518)		(518)
Repayments of finance obligations								387				(46)	654	358	(404)	2,858		2,517	733
Net cash provided by financing activities								387				(564)	654	(160)	(404)	2,340		1,914	733
Effect of exchange rate changes on cash													(10)					(112)
Summary of non-cash investing and financing activity
Recognition of right of use assets								$ (5,849)				$ 2,000	$ (20,086)	$ (22,841)	(30,520)	$ (48,723)		$ (74,446)	$ (37,378)
Conversion of preferred stock to common stock															$ 185

Unaudited Quarterly Financial_9

Unaudited Quarterly Financial data and Restatement of Previously Issued Unaudited interim Condensed Consolidated Financial Statements - Narrative (Details) - USD ($) $ in Thousands	3 Months Ended							6 Months Ended		9 Months Ended		12 Months Ended
	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Jun. 30, 2020	Jun. 30, 2019	Sep. 30, 2020	Sep. 30, 2019	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Right of use assets obtained in exchange for new operating lease liabilities												$ 58,500	$ 37,700
Research and development	$ 7,386	$ 4,873	$ 4,774	$ 4,882	$ 3,563	$ 3,608	$ 3,006	$ 9,647	$ 6,614	$ 17,033	$ 10,177	$ 27,848	15,059	$ 12,750
As previously Reported
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Research and development	11,964	9,757	10,412	9,341	8,028	8,933	7,373	20,169	16,306	32,133	24,334		33,675	33,907
Restatement Adjustments
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Research and development	$ (4,578)	$ (4,884)	$ (5,638)	$ (4,459)	$ (4,465)	$ (5,325)	$ (4,367)	$ (10,522)	$ (9,692)	$ (15,100)	$ (14,157)		(18,616)	(21,157)
Cost of Revenue													$ 19,492	$ 21,157

Unaudited Quarterly Financia_10

Unaudited Quarterly Financial data and Restatement of Previously Issued Unaudited Interim Condensed Consolidated Financial Statements - Additional Information (Details) - USD ($) $ in Thousands	3 Months Ended							6 Months Ended		9 Months Ended		12 Months Ended
	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Jun. 30, 2020	Jun. 30, 2019	Sep. 30, 2020	Sep. 30, 2019	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Long-term Line of Credit												$ 175,400
Property, Plant, and Equipment, Lessor Asset under Operating Lease, after Accumulated Depreciation	$ 71,891	$ 68,428	$ 68,402	$ 67,769	$ 67,248	$ 68,982	$ 70,928	$ 68,428	$ 68,982	$ 71,891	$ 67,248	75,807	$ 67,769
Other Liabilities, Noncurrent	45,170	14,476	2,386	2,818	2,834	3,333	3,746	14,476	3,333	45,170	2,834	40,447	2,818
Operating Lease, Liability												113,938
Accounts receivable	113,505	45,782	24,734	25,768	24,737	26,844	32,307	45,782	26,844	113,505	24,737	43,041	25,768
Inventory, Net	134,203	114,571	92,972	72,391	80,601	73,190	65,474	114,571	73,190	134,203	80,601	139,386	72,391
Prepaid Expense and Other Assets, Current	26,731	31,436	28,500	21,192	12,804	14,001	10,296	31,436	14,001	26,731	12,804	44,324	21,192
Goodwill	71,822	70,262	8,673	8,842	8,606	8,961	8,886	70,262	8,961	71,822	8,606	72,387	8,842
Operating Lease, Right-of-Use Asset	90,184	71,789	64,812	63,266	47,016	39,679	33,599	71,789	39,679	90,184	47,016	117,016	63,266
Intangible Assets, Net (Excluding Goodwill)	39,569	38,974	5,696	5,539	5,113	5,398	3,677	38,974	5,398	39,569	5,113	39,251	5,539
Accrued Liabilities, Current	37,948	23,917	14,870	14,409	9,457	4,522	6,509	23,917	4,522	37,948	9,457	46,083	14,409
Other Liabilities, Current	21,083	19,418	8,446	6,704	8,373	3,705	3,745	19,418	3,705	21,083	8,373	29,487	6,704
Deferred Revenue, Noncurrent	29,511	24,848	22,684	23,170	22,213	24,126	25,366	24,848	24,126	29,511	22,213	32,944	23,170
Other assets	9,661	11,817	12,059	8,573	9,152	8,842	11,069	11,817	8,842	9,661	9,152	5,513	8,573
Accounts payable	58,793	39,812	35,503	40,376	36,851	36,946	31,688	39,812	36,946	58,793	36,851	50,198	40,376
Convertible senior notes, net	105,088	142,889	113,063	110,431	107,945	66,844	65,025	142,889	66,844	105,088	107,945	85,640	110,431
Additional Paid in Capital	2,083,169	1,658,438	1,519,094	1,506,953	1,340,781	1,325,381	1,316,815	1,658,438	1,325,381	2,083,169	1,340,781	3,446,650	1,506,953
Accumulated Other Comprehensive Income (Loss), Net of Tax	1,846	1,159	1,052	1,288	929	1,460	1,374	1,159	1,460	1,846	929	2,451	1,288
Research and Development Expense	7,386	4,873	4,774	4,882	3,563	3,608	3,006	9,647	6,614	17,033	10,177	27,848	15,059	$ 12,750
Cost of Goods and Services Sold	135,632	68,010	50,522	83,861	54,892	51,324	29,250	118,532	80,574	254,164	135,466	376,179	219,327	200,219
Nonoperating Income (Expense)	(17,551)	(13,462)	(11,846)	(10,999)	(8,273)	(7,965)	(8,454)	(25,308)	(16,419)	(42,859)	(24,692)	(60,484)	(35,691)	(22,750)
Selling, General and Administrative Expense	17,210	21,644	11,109	9,973	10,395	13,613	9,221	32,753	22,834	49,963	33,229	79,348	43,202	37,685
Income tax benefit	6,644	17,371						17,371		24,015		30,845		9,295
Net revenue	107,048	67,995	40,819	91,607				108,814		215,862		(93,237)	229,975	174,215
Net Cash Provided by (Used in) Operating Activities			(60,402)				(35,699)	(111,891)	(48,328)	(156,506)	(54,141)	(155,476)	(53,324)	(58,350)
Repayments of Debt			5,343				53,580	11,129	55,712	19,038	56,603	27,212	59,196	30,531
Accumulated deficit	(1,462,377)	(1,397,160)	(1,387,752)	(1,350,307)	(1,332,259)	(1,314,425)	(1,297,072)	(1,397,160)	(1,314,425)	(1,462,377)	(1,332,259)	(1,946,488)	(1,350,307)
Bonus Accrual
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Other Labor-related Expenses	5,300									5,300
ROU assets and lease liabilities
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Other Labor-related Expenses										2,400
As previously Reported
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Property, Plant, and Equipment, Lessor Asset under Operating Lease, after Accumulated Depreciation	309,475	274,721	252,802	244,740	202,034	170,455	141,889	274,721	170,455	309,475	202,034		244,740
Other Liabilities, Noncurrent	27,068	11,756	13	13	13	13	17	11,756	13	27,068	13		13
Accounts receivable	113,133	45,522	24,437	25,448	24,392	26,592	32,062	45,522	26,592	113,133	24,392		25,448
Inventory, Net	134,306	114,571	92,972	72,391	80,601	73,190	65,474	114,571	73,190	134,306	80,601		72,391
Prepaid Expense and Other Assets, Current	26,731	31,436	28,500	21,192	12,804	14,001	10,296	31,436	14,001	26,731	12,804		21,192
Goodwill	71,962	70,402	8,673	8,842	8,606	8,961	8,886	70,402	8,961	71,962	8,606		8,842
Intangible Assets, Net (Excluding Goodwill)	39,169	38,574	5,296	5,539	5,113	5,398	3,677	38,574	5,398	39,169	5,113		5,539
Accrued Liabilities, Current	32,031	23,320	14,273	14,213	9,457	4,522	6,509	23,320	4,522	32,031	9,457		14,213
Other Liabilities, Current	17,280	21,692	10,423	8,543	10,238	3,017	2,271	21,692	3,017	17,280	10,238		8,543
Deferred Revenue, Noncurrent	29,648	25,038	22,912	23,369	22,444	24,519	25,835	25,038	24,519	29,648	22,444		23,369
Other assets	9,661	11,817	12,059	8,573	9,152	8,842	11,069	11,817	8,842	9,661	9,152		8,573
Accounts payable	58,793	39,812	35,503	40,376	36,851	36,946	31,688	39,812	36,946	58,793	36,851		40,376
Convertible senior notes, net	105,088	142,704	112,878	110,246	107,760	66,844	65,025	142,704	66,844	105,088	107,760		110,246
Additional Paid in Capital	2,083,199	1,658,532	1,519,257	1,507,116	1,340,859	1,325,459	1,316,893	1,658,532	1,325,459	2,083,199	1,340,859		1,507,116
Accumulated Other Comprehensive Income (Loss), Net of Tax	1,958	1,271	1,164	1,400	929	1,460	1,374	1,271	1,460	1,958	929		1,400
Research and Development Expense	11,964	9,757	10,412	9,341	8,028	8,933	7,373	20,169	16,306	32,133	24,334		33,675	33,907
Cost of Goods and Services Sold	108,279	62,994	45,284	78,882	51,114	46,914	25,363	108,278	72,277	216,557	123,391		202,273	172,010
Nonoperating Income (Expense)	(17,241)	(13,198)	(11,583)	(10,806)	(7,972)	(7,861)	(8,345)	(24,781)	(16,206)	(42,022)	(24,178)		(35,502)	(22,135)
Selling, General and Administrative Expense	14,277	21,658	11,013	10,982	10,400	13,627	9,324	32,671	22,951	46,948	33,351		44,333	38,198
Income tax benefit	6,523	17,659						17,659		24,182				9,217
Net revenue	106,989	68,070	40,813	91,664				108,883		215,872			230,239	174,632
Net Cash Provided by (Used in) Operating Activities			(60,015)				(36,263)	(111,247)	(48,488)	(156,910)	(51,801)		(51,522)	(57,617)
Repayments of Debt			5,730				53,534	11,783	56,070	18,634	59,461		61,713	31,264
Accumulated deficit	(1,431,340)	(1,391,961)	(1,383,299)	(1,345,807)	(1,327,518)	(1,309,363)	(1,291,255)	(1,391,961)	(1,309,363)	(1,431,340)	(1,327,518)		(1,345,807)
Provision (benefit) for loss contracts related to service
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Cost of Goods and Services Sold	25,147	706	95	13	206	363	162	801	201	25,948	407	35,473	394	5,345
Provision (benefit) for loss contracts related to service | As previously Reported
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Cost of Goods and Services Sold	4,306									4,306
Sales of fuel cell systems and related infrastructure
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Cost of Goods and Services Sold	69,428	33,888	13,974	47,091	25,183	23,329	2,312	47,862	25,641	117,290	50,824	171,404	97,915	85,205
Sales of fuel cell systems and related infrastructure | Revision of Research and Development Expense
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Cost of Goods and Services Sold													7,000
Sales of fuel cell systems and related infrastructure | As previously Reported
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Cost of Goods and Services Sold	68,509	33,676	13,744	46,419	24,990	23,129	2,321	47,420	25,450	115,929	50,440		96,859	84,439
Fuel delivered to customers
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Cost of Goods and Services Sold	17,002	11,076	11,254	12,800	11,149	11,146	10,152	22,330	21,298	39,332	32,447	61,815	45,247	36,037
Fuel delivered to customers | Revision of Research and Development Expense
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Cost of Goods and Services Sold													8,900
Fuel delivered to customers | As previously Reported
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Cost of Goods and Services Sold	14,172	9,060	9,035	10,422	9,160	8,854	7,921	18,095	16,775	32,267	25,935		36,357	27,712
Services performed on fuel cell systems and related infrastructure
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Cost of Goods and Services Sold	9,180	7,773	10,347	11,606	7,802	8,383	6,791	18,120	15,174	27,300	22,976	42,524	34,582	32,271
Services performed on fuel cell systems and related infrastructure | As previously Reported
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Cost of Goods and Services Sold	7,074	6,491	8,181	9,999	6,461	6,218	6,123	14,672	12,341	21,746	18,802		28,801	23,698
Power Purchase Agreements
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Cost of Goods and Services Sold	14,744	14,504	14,771	12,301	10,814	8,829	9,833	29,275	18,662	44,019	29,476	$ 64,640	41,777	41,361
Power Purchase Agreements | As previously Reported
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Cost of Goods and Services Sold	$ 14,087	$ 13,704	$ 14,243	$ 11,992	10,353	8,713	8,998	$ 27,947	17,711	$ 42,034	28,064		$ 40,056	$ 36,161
ASU 2019-08 | As previously Reported
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Additional Paid in Capital					6,500	3,500	3,000		3,500		6,500
Accumulated deficit					$ 6,500	$ 3,500	$ 3,000		$ 3,500		$ 6,500

Summary of Significant Accoun_4

Summary of Significant Accounting Policies (Details) - USD ($) $ in Thousands

12 Months Ended

Dec. 31, 2020

Dec. 31, 2019

Dec. 31, 2018

Jan. 01, 2021

Sep. 30, 2020

Jun. 30, 2020

May 31, 2020

May 29, 2020

May 18, 2020

Mar. 31, 2020

Sep. 30, 2019

Jun. 30, 2019

Mar. 31, 2019

Mar. 31, 2018

Summary of Significant Accounting Policies

Loss accrual

$ 24,013

$ 3,702

$ 5,345

Operating lease maximum allowed extension percentage

75.00%

Minimum number of days after an invoice is issued when accounts receivable is considered due

30 days

Maximum number of days after an invoice is issued when accounts receivable is considered due

60 days

Allowance for doubtful accounts receivable

$ 172

249

Accumulated deficit

(1,946,488)

(1,350,307)

$ (1,462,377)

$ (1,397,160)

$ (1,387,752)

$ (1,332,259)

$ (1,314,425)

$ (1,297,072)

Additional paid-in capital

3,446,650

1,506,953

$ 2,083,169

$ 1,658,438

$ 1,519,094

$ 1,340,781

$ 1,325,381

$ 1,316,815

Interest rate (as a percent)

3.50%

Stock-Based Compensation

Tax benefit (expense) for stock-based compensation

$ 0

$ 0

$ 0

Fuel

Property, Plant and Equipment

Estimated useful life

10 years

Hydrogen infrastructure

Property, Plant and Equipment

Estimated useful life

20 years

Minimum

Summary of Significant Accounting Policies

Payment terms for fuel cells and its services

30 days

Extension period

5 years

Uptime of the fleet (as a percent)

97.00%

Intangible Assets

Intangible asset useful lives

5 years

Maximum

Summary of Significant Accounting Policies

Payment terms for fuel cells and its services

90 days

Extension period

10 years

Uptime of the fleet (as a percent)

98.00%

Intangible Assets

Intangible asset useful lives

10 years

Leasehold Improvements | Minimum

Property, Plant and Equipment

Estimated useful life

5 years

Leasehold Improvements | Maximum

Property, Plant and Equipment

Estimated useful life

10 years

Software, machinery and equipment | Minimum

Property, Plant and Equipment

Estimated useful life

1 year

Software, machinery and equipment | Maximum

Property, Plant and Equipment

Estimated useful life

15 years

3.75% Convertible Senior Notes

Summary of Significant Accounting Policies

Interest rate (as a percent)

3.75%

3.75%

3.75%

3.75%

5.5% Convertible Senior Notes

Summary of Significant Accounting Policies

Interest rate (as a percent)

5.50%

5.50%

5.50%

5.50%

Cumulative Adjustment

Summary of Significant Accounting Policies

Convertible Debt

$ 120,700

Accumulated deficit

9,500

Additional paid-in capital

$ 130,200

Summary of Significant Accoun_5

Summary of Significant Accounting Policies - Accrual for loss contracts (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Accrual for loss contracts
Beginning Balance	$ 3,702	$ 5,345
Provision (benefit) for Loss Accrual	35,473	394	$ 5,345
Released to Service Cost of Sales	(2,348)	(1,249)
Released to Provision for Warrants	(12,814)
Ending Balance	$ 24,013	$ 3,702	$ 5,345

Summary of Significant Accoun_6

Summary of Significant Accounting Policies - Fair value measurements (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Level 2
Fair Value
Convertible senior notes	$ 1,272,766	$ 135,320
Level 3
Fair Value
Contingent consideration	9,760
Convertible senior notes		53,455
Long-term debt	175,402	112,169
Finance obligations	181,553	144,089
Carrying value
Fair Value
Contingent consideration	9,760
Convertible senior notes	85,640	110,431
Long-term debt	175,402	112,169
Finance obligations	181,553	144,089
Fair value
Fair Value
Contingent consideration	9,760
Convertible senior notes	1,272,766	188,775
Long-term debt	175,402	112,169
Finance obligations	$ 181,553	$ 144,089

Acquisitions - Fair value of co

Acquisitions - Fair value of consideration (Details) - USD ($) $ in Thousands	Jun. 22, 2020	Jun. 18, 2020
Giner ELX, Inc
Cash	$ 25,820
Plug Power Stock	19,263
Contingent consideration	7,790
Total consideration	$ 52,873
United Hydrogen Group Inc
Cash		$ 19,293
Plug Power Stock		30,410
Contingent consideration		1,110
Total consideration		$ 50,813

Acquisitions - Allocation Of Pu

Acquisitions - Allocation Of Purchase Price (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Jun. 22, 2020	Jun. 18, 2020
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Net [Abstract]
Deferred tax liability, net	$ (5,900)
Giner ELX, Inc
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Net [Abstract]
Accounts receivable		$ 1,237
Inventory		4,108
Prepaid expenses and other assets		669
Property, Plant and equipment.		596
Identifiable intangibles		29,930
Accounts payable, accrued expenses, deferred revenue and finance obligations		(1,621)
Deferred revenue		(2,350)
Deferred tax liability, net		(5,889)
Total net assets acquired, excluding goodwill		$ 26,680
United Hydrogen Group Inc
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Net [Abstract]
Accounts receivable			$ 444
Inventory			89
Prepaid expenses and other assets			1,152
Property, Plant and equipment.			41,244
Leased property			796
Identifiable intangibles			2,338
Long-term debt			(11,336)
Unfavorable customer contract			(15,757)
Accounts payable, accrued expenses, deferred revenue and finance obligations			(4,631)
Total net assets acquired, excluding goodwill			$ 14,339

Acquisitions - Goodwill (Detail

Acquisitions - Goodwill (Details) - USD ($) $ in Thousands	Jun. 22, 2020	Jun. 18, 2020	Dec. 31, 2020	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019
Total goodwill recognized			$ 72,387	$ 71,822	$ 70,262	$ 8,673	$ 8,842	$ 8,606	$ 8,961	$ 8,886
Giner ELX, Inc
Consideration paid	$ 52,873
Less: net assets acquired	(26,680)
Total goodwill recognized	$ 26,193
United Hydrogen Group Inc
Consideration paid		$ 50,813
Less: net assets acquired		(14,339)
Total goodwill recognized		$ (36,474)

Acquisitions - Narratives (Deta

Acquisitions - Narratives (Details) $ in Thousands	Jun. 22, 2020USD ($)item	Jun. 18, 2020USD ($)	Apr. 30, 2020USD ($)	Sep. 30, 2020USD ($)	Sep. 30, 2020USD ($)	Dec. 31, 2020USD ($)	Dec. 31, 2019USD ($)	Sep. 30, 2019USD ($)	Jun. 30, 2019USD ($)	Mar. 31, 2019USD ($)
Warrants								$ 98	$ 525	$ 2,231
Increase in goodwill							$ 62,600
Change in fair value				$ 1,130	$ 1,130	$ 1,160
Deferred tax liability						5,900
Reduction to valuation allowance						5,200
Unrecognized tax benefits released due to expiration of stature of limitations						5,200
Giner ELX, Inc
Percentage of outstanding shares	100.00%
Earn-out payments	$ 16,000					7,800
Achievement of Allagash earn out	8,000
Receipt of certain customer opportunities	2,000
Achievement of revenue targets	$ 6,000
Number of electrolyzer stacks | item	2
Warrants term	2 years
Increase in other liabilities						700
Increase in goodwill						700
Fair value contingent estimated						9,600
Change in fair value						1,800
Deferred tax liability	$ 5,889
Revenues						3,600
Giner ELX, Inc | Non achieving of allagash earn out revenue by July 31, 2033
Percentage of monthly reduction of contingent consideration	8.33%
Giner ELX, Inc | Earn-out revenue exceeds 150% of target stated for year 2023
Warrants	$ 5,000
Giner ELX, Inc | Earn-out revenue exceeds 200% of target stated for year 2023
Warrants	$ 10,000
United Hydrogen Group Inc
Percentage of outstanding shares		100.00%
Earn-out payments		$ 1,100				200
Cash paid in respect to certain indebtedness			$ 1,000
Increase in goodwill		200
Decrease in long term debt		1,900
Increase in other liabilities		1,700
Payment made on achievement of first milestone		300
Change in fair value of contingent consideration due to reduction in the probability assessment		$ 610
Revenues						4,200
United Hydrogen Group Inc | Common Stock
Value of shares of common stock issued			$ 6,500
Developed Technology Rights | United Hydrogen Group Inc
Fair value of acquisition						2,300
In process R&D | Giner ELX, Inc
Fair value of acquisition						29,000
Customer relationships | Giner ELX, Inc
Fair value of acquisition						400
Wet Stack Technology | Giner ELX, Inc
Fair value of acquisition						$ 400

Earnings Per Share - Basic and

Earnings Per Share - Basic and Diluted Components (Details) - USD ($) $ in Thousands	3 Months Ended								6 Months Ended		9 Months Ended		12 Months Ended
	Dec. 31, 2020	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Jun. 30, 2020	Jun. 30, 2019	Sep. 30, 2020	Sep. 30, 2019	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Numerator:
Net (loss) income attributable to common shareholders	$ (484,105)	$ (65,217)	$ (9,414)	$ (37,445)	$ (19,277)	$ (18,366)	$ (17,351)	$ (30,560)	$ (46,859)	$ (47,911)	$ (112,076)	$ (66,277)	$ (596,181)	$ (85,555)	$ (85,660)
Denominator:
Weighted average number of common stock outstanding		371,010,544	316,645,050	305,192,201	260,053,150	236,759,521	231,114,868	220,605,068	310,918,626	225,899,224	330,949,265	229,519,323	354,790,106	237,152,780	218,882,337

Earnings Per Share - Dilutive P

Earnings Per Share - Dilutive Potential Common Shares (Details) - USD ($) $ in Thousands	Jul. 01, 2020	Nov. 01, 2018	May 16, 2013	Jan. 31, 2020	Jul. 31, 2017	Apr. 30, 2017	Dec. 31, 2020	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018	May 31, 2020	May 18, 2020	Sep. 30, 2019	Mar. 31, 2018	Apr. 04, 2017
Earnings Per Share
Number of dilutive potential common stock								163,169,490	200,327,965	201,692,250
Interest rate (as a percent)											3.50%
Convertible senior notes							$ 85,600	$ 85,600
Stock options
Earnings Per Share
Stock options granted								3,509,549	3,221,892	2,679,667
Warrant Transaction Agreements
Earnings Per Share
Shares of common stock that can be purchased from warrants issued (in shares)					55,286,696	55,286,696									55,286,696
Number of warrants exercised (in shares)					5,819,652	0
Tranche one of warrants issued with the Amazon.com, Inc transaction agreement
Earnings Per Share
Shares of common stock that can be purchased from warrants issued (in shares)															5,819,652
Series C Preferred Stock
Earnings Per Share
Shares issued (in shares)			10,431
Series E Preferred Stock
Earnings Per Share
Shares issued (in shares)		35,000
Number of shares redeemed									4,038
Number of preferred shares that had been converted to common stock				500					30,462
5.5% Convertible Senior Notes
Earnings Per Share
Interest rate (as a percent)							5.50%	5.50%			5.50%	5.50%		5.50%
Conversion of notes through common stock issuance							14,600,000
Repurchase amount											$ 66,300
Convertible senior notes							$ 33,500	$ 33,500
Long-term borrowings							$ 160	$ 160			$ 48,700
7.5% Convertible Senior Note
Earnings Per Share
Interest rate (as a percent)	7.50%						7.50%	7.50%					7.50%
Conversion of notes through common stock issuance	16,000,000
Stock options
Earnings Per Share
Number of dilutive potential common stock								10,284,498	23,013,590	21,957,150
Stock options granted								3,509,549	3,221,892	2,679,667
Restricted stock
Earnings Per Share
Number of dilutive potential common stock								5,874,642	4,608,560	2,347,347
Stock options granted								3,227,149	3,201,892	2,367,347
Warrants
Earnings Per Share
Number of dilutive potential common stock								104,753,740	110,573,392	115,824,142
Preferred stock
Earnings Per Share
Number of dilutive potential common stock									2,998,527	17,933,591
Convertible Senior Notes
Earnings Per Share
Number of dilutive potential common stock								42,256,610	59,133,896	43,630,020

Inventory (Details)

Inventory (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019
Inventory
Raw materials and supplies - production locations	$ 92,221				$ 48,011
Raw materials and supplies - customer locations	12,405				9,241
Work-in-process	29,349				12,529
Finished goods	5,411				2,610
Inventory	$ 139,386	$ 134,203	$ 114,571	$ 92,972	$ 72,391	$ 80,601	$ 73,190	$ 65,474

Property, Plant and Equipment_2

Property, Plant and Equipment (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019
Property, plant and equipment
Property, plant, and equipment, gross	$ 96,735	$ 32,376
Less: accumulated depreciation	(22,186)	(17,417)
Property, plant, and equipment, net	74,549	14,959		$ 64,820	$ 60,018	$ 16,591	$ 14,990	$ 14,228	$ 13,615
Depreciation expense	4,800	3,600	$ 2,600
Land
Property, plant and equipment
Property, plant, and equipment, gross	1,165
Leasehold Improvements
Property, plant and equipment
Property, plant, and equipment, gross	1,121	862
Software, machinery and equipment
Property, plant and equipment
Property, plant, and equipment, gross	$ 94,449	$ 31,514

Equipment Related to Power Pu_3

Equipment Related to Power Purchase Agreements and Fuel Delivered to Customers, net (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019
Lessee, Lease, Description [Line Items]
Lessor property and equipment related to power purchase agreements	$ 92,736				$ 81,194
Less: accumulated depreciation	(16,929)				(13,425)
Lessor property and equipment related to power purchase agreements, net	$ 75,807	$ 71,891	$ 68,428	$ 68,402	67,769	$ 67,248	$ 68,982	$ 70,928
Restatement Adjustments
Lessee, Lease, Description [Line Items]
Lessor property and equipment related to power purchase agreements, net		$ (237,584)	$ (206,293)	$ (184,400)	$ (176,971)	$ (134,786)	$ (101,473)	$ (70,961)

Equipment Related to Power Pu_4

Equipment Related to Power Purchase Agreements and Fuel Delivered to Customers, net - Future minimum lease payments (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Lessor, Lease, Description [Line Items]
Depreciation expense	$ 7.9	$ 6.3
Minimum
Lessor, Lease, Description [Line Items]
Lease term	1 year
Maximum
Lessor, Lease, Description [Line Items]
Lease term	10 years

Intangible Assets and Goodwil_2

Intangible Assets and Goodwill - Gross Carrying Amount (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019
Gross carrying amount and accumulated amortization of acquired identifiable intangible assets
Gross Carrying Amount	$ 43,587	$ 8,564
Accumulated Amortization	(4,336)	(3,025)
Total	39,251	5,539
Goodwill	72,387	8,842	$ 71,822	$ 70,262	$ 8,673	$ 8,606	$ 8,961	$ 8,886
Increase in goodwill		62,600
Translation gain on goodwill		900
Goodwill impairments	0	0
EnergyOr
Gross carrying amount and accumulated amortization of acquired identifiable intangible assets
Acquired		1,500
Milestone payments		$ 3,000
American Fuel Cell LLC
Gross carrying amount and accumulated amortization of acquired identifiable intangible assets
Milestone payments	2,900
In process R&D
Gross carrying amount and accumulated amortization of acquired identifiable intangible assets
Gross Carrying Amount	29,000
Total	$ 29,000
Acquired technology
Gross carrying amount and accumulated amortization of acquired identifiable intangible assets
Weighted Average Amortization Period	10 years	9 years
Gross Carrying Amount	$ 13,697	$ 8,244
Accumulated Amortization	(4,042)	(2,815)
Total	$ 9,655	$ 5,429
Customer relationships, Backlog & Trademark
Gross carrying amount and accumulated amortization of acquired identifiable intangible assets
Weighted Average Amortization Period	6 years
Gross Carrying Amount	$ 890
Accumulated Amortization	(294)
Total	$ 596
Trademark
Gross carrying amount and accumulated amortization of acquired identifiable intangible assets
Weighted Average Amortization Period		9 years
Gross Carrying Amount		$ 320
Accumulated Amortization		(210)
Total		$ 110

Intangible Assets and Goodwil_3

Intangible Assets and Goodwill - Estimated Amortization Expense (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended		9 Months Ended		12 Months Ended
	Mar. 31, 2020	Mar. 31, 2019	Jun. 30, 2020	Jun. 30, 2019	Sep. 30, 2020	Sep. 30, 2019	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Intangible Assets and Goodwill
Amortization of Intangible Assets	$ 175	$ 175	$ 398	$ 338	$ 835	$ 518	$ 1,135	$ 698	$ 693
Estimated amortization expense
2021							1,878
2022							1,478
2023							1,478
2024							1,456
2025 and thereafter							3,961
Total							$ 10,251

Accrued Expenses (Details)

Accrued Expenses (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019
Accrued Expenses
Accrued payroll and compensation related costs	$ 29,167				$ 2,932
Accrued accounts payable	11,750				7,254
Accrued sales and other taxes	3,665				905
Accrued interest	649				2,374
Accrued other	852				944
Total	$ 46,083	$ 37,948	$ 23,917	$ 14,870	$ 14,409	$ 9,457	$ 4,522	$ 6,509

Operating and Finance Lease L_3

Operating and Finance Lease Liabilities - Narrative (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019
Lessee, Lease, Description [Line Items]
Rental expense for all operating lease	$ 22,300	$ 14,600	$ 10,200
Gross profit on sale leaseback transactions	61,000	26,200	$ 16,400
Right of use assets obtained in exchange for new operating lease liabilities	58,500	37,700
Right of use assets related to operating leases	117,016	63,266		$ 90,184	$ 71,789	$ 64,812	$ 47,016	$ 39,679	$ 33,599
Amortization of right-of-use asset from operating lease	48,600	23,600
Right of use assets related to finance leases, net	5,724	1,714		$ 2,335	$ 2,389	$ 1,707	$ 1,720	$ 1,726	$ 1,733
Amortization of right-of-use asset from finance lease	102	32
Prepaid rent and security deposit	5,800	6,000
Right-of-Use Asset Obtained in Exchange for Finance Lease Liability	$ 4,100	$ 100
Minimum
Lessee, Lease, Description [Line Items]
Lease Term - as Lessee	1 year
Maximum
Lessee, Lease, Description [Line Items]
Lease Term - as Lessee	9 years

Operating and Finance Lease L_4

Operating and Finance Lease Liabilities - Future minimum lease payments under operating and finance leases (Details) $ in Thousands	Dec. 31, 2020USD ($)
Future minimum lease payments under operating lease
2021	$ 28,536
2022	27,138
2023	26,464
2024	25,947
2025 and thereafter	50,362
Total future minimum lease payments	158,447
Less imputed lease interest	(44,509)
Total operating lease, liabilities	113,938
Future minimum lease payments under finance leases
2021	1,261
2022	1,234
2023	1,210
2024	1,293
2025 and thereafter	1,721
Total future minimum lease payments	6,719
Less imputed lease interest	(1,323)
Total finance lease liabilities	5,396
Total future minimum payments	165,166
Future minimum lease payments under operating and finance leases
2021	29,797
2022	28,372
2023	27,674
2024	27,240
2025 and thereafter	52,083
Less imputed lease interest	(45,832)
Total	$ 119,334

Operating and Finance Lease L_5

Operating and Finance Lease Liabilities - Other information related to the operating leases (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Lessee, Operating Lease, Description [Abstract]
Cash payments	$ 22,626	$ 14,055
Weighted average remaining lease term (in years)	6 years	5 years
Weighted average discount rate (as a percent)	11.70%	12.10%

Operating and Finance Lease L_6

Operating and Finance Lease Liabilities - Other information related to the finance leases (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Other information
Cash payments	$ 471	$ 255
Weighted average remaining lease term (years)	5 years 7 months 6 days	7 years 8 months 12 days
Weighted average discount rate	8.20%	8.80%

Finance Obligations - Narrative

Finance Obligations - Narrative (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019
Sale Leaseback Transaction [Line Items]
Total operating lease, liabilities	$ 113,938
Short term operating lease obligation	14,314	$ 10,609	$ 9,453	$ 8,959	$ 9,428	$ 8,666	$ 7,512	$ 7,042
Long term operating lease obligation	99,624	74,422	58,410	52,165	50,937	36,599	30,631	25,657
Total finance lease liabilities	5,396
Short term finance lease obligation	903	374	345	204	226	310	266	236
Long term finance lease obligation	4,493	$ 2,384	$ 2,465	$ 1,953	2,011	$ 2,068	$ 2,123	$ 2,142
Sale Leaseback Agreements
Sale Leaseback Transaction [Line Items]
Total operating lease, liabilities	157,700				112,400
Short term operating lease obligation	24,700				16,800
Long term operating lease obligation	132,900				95,600
Total finance lease liabilities	23,852				31,700
Short term finance lease obligation	8,000				7,900
Long term finance lease obligation	$ 15,900				$ 23,800

Finance Obligations - Future mi

Finance Obligations - Future minimum payments under finance obligations (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Future minimum lease payments under finance leases
2021	$ 1,261
2022	1,234
2023	1,210
2024	1,293
2025 and thereafter	1,721
Total future minimum lease payments	6,719
Less imputed lease interest	(1,323)
Total finance lease liabilities	5,396
Total future minimum payments	165,166
Finance obligation
Future minimum lease payments under finance leases
2021	50,997
2022	44,243
2023	42,417
2024	55,422
2025 and thereafter	53,385
Total future minimum lease payments	246,464
Less imputed lease interest	(64,911)
Total finance lease liabilities	181,553
Sale of Future Revenue - Debt
Future minimum lease payments under finance leases
2021	41,670
2022	39,268
2023	39,268
2024	39,268
2025 and thereafter	53,385
Total future minimum lease payments	212,859
Less imputed lease interest	(55,158)
Total finance lease liabilities	157,701
Sale Leaseback Agreements
Future minimum lease payments under finance leases
2021	9,327
2022	4,975
2023	3,149
2024	16,154
Total future minimum lease payments	33,605
Less imputed lease interest	(9,753)
Total finance lease liabilities	$ 23,852	$ 31,700

Finance Obligations - Other inf

Finance Obligations - Other information related to finance obligations (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Sale Leaseback Transaction [Line Items]
Cash payments	$ 471	$ 255
Weighted average remaining term (years)	5 years 7 months 6 days	7 years 8 months 12 days
Weighted average discount rate	8.20%	8.80%
Finance obligation
Sale Leaseback Transaction [Line Items]
Cash payments	$ 44,245	$ 76,244
Weighted average remaining term (years)	5 years	5 years 3 months 18 days
Weighted average discount rate	11.30%	11.20%

Long-Term Debt (Details)

Long-Term Debt (Details) - USD ($) $ in Thousands

1 Months Ended

3 Months Ended

6 Months Ended

9 Months Ended

12 Months Ended

Mar. 31, 2021

Nov. 30, 2019

Jun. 30, 2020

Sep. 30, 2019

Mar. 31, 2019

Jun. 30, 2020

Jun. 30, 2019

Sep. 30, 2020

Sep. 30, 2019

Dec. 31, 2020

Dec. 31, 2019

May 31, 2020

Long-Term Debt

Interest rate (as a percent)

3.50%

Loss on extinguishment of debt

$ 13,222

$ (518)

$ (518)

$ 13,222

$ (518)

$ 13,222

$ (518)

$ 17,686

$ (518)

Proceeds from escrow

$ 700

250

Interest expense

$ 800

Percent of securities in foreign subsidiaries guaranteed to secure debt

65.00%

Principal payments of long term debt

December 31, 2021

$ 127,317

December 31, 2022

93,321

December 31, 2023

62,920

December 31, 2024

33,692

Incremental term loan

175,400

Short-term other assets

Long-Term Debt

Proceeds from escrow

700

Secured term loan facility

Long-Term Debt

Borrowing

$ 20,000

Secured term loan facility | Loan and security agreement

Long-Term Debt

Borrowing

$ 100,000

Interest rate (as a percent)

9.50%

12.00%

Term Loan facility

Principal payments of long term debt

Incremental term loan

$ 165,800

Generate Lending, LLC | Secured term loan facility | Loan and security agreement

Long-Term Debt

Loan Amount

$ 100,000

NY Green Bank

Long-Term Debt

Loss on extinguishment of debt

$ 500

Cash held in escrow deposit

$ 1,750

Convertible Senior Notes - Net

Convertible Senior Notes - Net proceeds (Details) $ / shares in Units, $ in Thousands	Jul. 01, 2020shares	May 18, 2020USD ($)D$ / shares	Feb. 28, 2021USD ($)shares	Jan. 31, 2021USD ($)shares	Nov. 30, 2020$ / sharesshares	Aug. 31, 2020$ / sharesshares	May 31, 2020USD ($)shares	Dec. 31, 2019USD ($)$ / sharesshares	Sep. 30, 2019USD ($)	Mar. 31, 2019$ / sharesshares	Feb. 28, 2021USD ($)shares	Dec. 31, 2020USD ($)$ / sharesshares	Jun. 30, 2020USD ($)	Mar. 31, 2020USD ($)	Sep. 30, 2019USD ($)	Mar. 31, 2019USD ($)$ / shares	Jun. 30, 2020USD ($)	Jun. 30, 2019USD ($)	Sep. 30, 2020USD ($)	Sep. 30, 2019USD ($)	Dec. 31, 2020USD ($)$ / sharesshares	Dec. 31, 2019USD ($)$ / shares	Dec. 31, 2018USD ($)	May 29, 2020USD ($)	Mar. 31, 2018USD ($)
Convertible Senior Notes
Interest rate (as a percent)							3.50%
Net proceeds														$ 9,024			$ 27,678	$ 25,609	$ 47,568	$ 57,249	$ 65,259	$ 83,668	$ 76,175
Aggregate consideration																	90,238		90,238		90,238
Conversion of convertible notes to common stock																					62,553
Convertible senior notes												$ 85,600									85,600
Convertible senior note														$ 441			441		43,058	1,883	1,179	28,392
Proceeds from issuance of convertible senior notes, net																	205,100		205,098	39,052	205,098	39,052	$ 95,856
Gain (loss) on extinguishment of debt													$ 13,222		$ (518)	$ (518)	$ 13,222	$ (518)	$ 13,222	(518)	$ 17,686	$ (518)
Closing price of the company's stock | $ / shares					$ 22.25	$ 10.25		$ 2.75		$ 2.35						$ 2.35						$ 2.75
Common stock shares issued | shares					43,700,000	35,276,250		46,000,000		10,000,000		4,400,000									79,000,000
Subsequent event
Convertible Senior Notes
Common stock shares issued | shares											32.2
Level 3
Convertible Senior Notes
Fair value of convertible senior notes								$ 53,455														$ 53,455
3.75% Convertible Senior Notes
Convertible Senior Notes
Principal amount		$ 200,000					$ 212,463					$ 212,463									$ 212,463			$ 12,500
Interest rate (as a percent)		3.75%					3.75%					3.75%									3.75%			3.75%
Net proceeds							$ 189,219
Maturity principal amount		$ 1
Conversion rates for the notes (in shares)		198.6196
Conversion price, per share | $ / shares		$ 5.03
Trading days | D		20
Consecutive trading days | D		30
Conversion price (as a percent)		130.00%
Number of business days		5 days
Number of consecutive trading days		5 days
Principal amount (as a percent)		98.00%
Percentage of principal amount to be redeemed		100.00%
Carrying amount of the liability component		$ 75,200
Carrying amount of the equity component		$ 130,300										$ 130,249									$ 130,249
Effective interest rate (as a percent)		29.00%
Transaction costs for issuance		$ 7,000
Initial purchasers' discount		6,400					6,374
Other issuance costs		600					617
Transaction costs attributable to the liability component		2,600
Transaction costs attributable to the equity component		$ 4,400
Closing price of the company's stock | $ / shares												$ 33.91									$ 33.91
Fair value of convertible senior notes												$ 1,300,000									$ 1,300,000
3.75% Convertible Senior Notes | Subsequent event
Convertible Senior Notes
Interest rate (as a percent)			3.75%	3.75%							3.75%
Conversion of notes through common stock issuance | shares			3,000,000	3,000,000							3,000,000
Convertible senior note			$ 15,200	$ 15,200							$ 15,200
3.75% Convertible Senior Notes | Minimum
Convertible Senior Notes
Redemption notice days		1 day
3.75% Convertible Senior Notes | Maximum
Convertible Senior Notes
Redemption notice days		3 days
3.75% Convertible Senior Notes | Private placement
Convertible Senior Notes
Principal amount							$ 212,500
Interest rate (as a percent)							3.75%
7.5% Convertible Senior Note
Convertible Senior Notes
Principal amount									$ 40,000						$ 40,000					$ 40,000
Interest rate (as a percent)	7.50%								7.50%			7.50%			7.50%					7.50%	7.50%
Conversion of notes through common stock issuance | shares	16,000,000
Maturity principal amount									$ 48,000						$ 48,000					$ 48,000
Proceeds from issuance of convertible senior notes, net									$ 39,100
Percentage of principal amount to be redeemed									120.00%
5.5% Convertible Senior Notes
Convertible Senior Notes
Principal amount		$ 100,000						100,000				$ 160									$ 160	100,000			$ 100,000
Interest rate (as a percent)		5.50%					5.50%					5.50%									5.50%				5.50%
Repurchase of convertible senior notes | shares							9,400,000
Aggregate repurchase of debt							$ 128,900
Aggregate consideration							90,200
Conversion of notes through common stock issuance | shares												14,600,000
Debt component of debt exchange							35,500
Equity component of debt exchange							$ 93,400
Discount rate for fair value of liability							29.80%
Long-term borrowings							$ 48,700					$ 160									$ 160
Convertible senior notes												33,500									$ 33,500
Maturity principal amount							66,300
Gain on early debt extinguishment							$ 13,200
Percentage of principal amount to be redeemed							100.00%
Carrying amount of the liability component							$ 58,200
Carrying amount of the equity component							$ 37,700	$ 37,702														37,702
Effective interest rate (as a percent)							16.00%
Transaction costs for issuance							$ 4,100
Initial purchasers' discount							3,300
Other issuance costs							900															$ 1,700
Gain (loss) on extinguishment of debt												$ 4,500
Transaction costs attributable to the liability component							2,400
Transaction costs attributable to the equity component							$ 1,700

Convertible Senior Notes (Detai

Convertible Senior Notes (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2020	Sep. 30, 2020	Jun. 30, 2020	May 31, 2020	May 29, 2020	May 18, 2020	Mar. 31, 2020	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Mar. 31, 2018
Convertible Senior Notes
Net carrying amount	$ 110,431	$ 85,640	$ 105,088	$ 142,889				$ 113,063	$ 107,945	$ 66,844	$ 65,025
3.75% Convertible Senior Notes
Convertible Senior Notes
Principal amount		212,463			$ 212,463	$ 12,500	$ 200,000
Unamortized debt discount		(124,655)
Unamortized debt issuance costs		(2,295)
Net carrying amount		85,513
Carrying amount of the equity component		130,249					130,300
5.5% Convertible Senior Notes
Convertible Senior Notes
Principal amount	100,000	160					$ 100,000					$ 100,000
Unamortized debt discount	(27,818)	(32)
Unamortized debt issuance costs	(1,567)	(1)
Net carrying amount	70,615	$ 127
Carrying amount of the equity component	37,702				$ 37,700
Income tax benefit on equity component	$ 9,200

Convertible Senior Notes - Conv

Convertible Senior Notes - Conversion (Details) - USD ($) $ in Thousands	May 18, 2020	May 31, 2020	Mar. 31, 2020	Jun. 30, 2020	Jun. 30, 2019	Sep. 30, 2020	Sep. 30, 2019	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018	May 29, 2020	Mar. 31, 2018
Convertible Senior Notes
Net proceeds			$ 9,024	$ 27,678	$ 25,609	$ 47,568	$ 57,249	$ 65,259	$ 83,668	$ 76,175
5.5% Convertible Senior Notes
Convertible Senior Notes
Principal amount	$ 100,000							160	100,000			$ 100,000
Less initial purchasers' discount		$ (3,300)
Less other issuance costs		(900)							$ (1,700)
3.75% Convertible Senior Notes
Convertible Senior Notes
Principal amount	200,000	212,463						$ 212,463			$ 12,500
Less initial purchasers' discount	(6,400)	(6,374)
Less cost of related capped calls		(16,253)
Less other issuance costs	$ (600)	(617)
Net proceeds		$ 189,219

Convertible Senior Notes - Capp

Convertible Senior Notes - Capped Call and Common Stock Forward (Details) - USD ($) $ / shares in Units, $ in Thousands	May 18, 2020	Nov. 30, 2020	Aug. 31, 2020	May 31, 2020	Dec. 31, 2019	Mar. 31, 2019	Dec. 31, 2020	Dec. 31, 2020	Jul. 01, 2020	May 29, 2020	Sep. 30, 2019	Mar. 31, 2018
Capped Call and Common Stock Forward
Interest rate (as a percent)				3.50%
Share Price		$ 22.25	$ 10.25		$ 2.75	$ 2.35
Common stock shares issued		43,700,000	35,276,250		46,000,000	10,000,000	4,400,000	79,000,000
Common Stock Forward
Capped Call and Common Stock Forward
Common stock shares issued								14,397,906
3.75% Convertible Senior Notes
Capped Call and Common Stock Forward
Interest rate (as a percent)	3.75%			3.75%			3.75%	3.75%		3.75%
Principal amount	$ 200,000			$ 212,463			$ 212,463	$ 212,463		$ 12,500
Share Price							$ 33.91	$ 33.91
3.75% Convertible Senior Notes | Capped Call
Capped Call and Common Stock Forward
Capped call options amount	$ 16,200
Cap price	$ 6.7560
Premium (as a percent)	60.00%
Share Price	$ 4.11
5.5% Convertible Senior Notes
Capped Call and Common Stock Forward
Interest rate (as a percent)	5.50%			5.50%			5.50%	5.50%				5.50%
Principal amount	$ 100,000				$ 100,000		$ 160	$ 160				$ 100,000
5.5% Convertible Senior Notes | Capped Call
Capped Call and Common Stock Forward
Capped call options amount				$ 16,000
Cap price				$ 3.82
Premium (as a percent)				100.00%
Share Price				$ 1.91
Recorded in additional paid-in capital				$ 24,200
7.5% Convertible Senior Note
Capped Call and Common Stock Forward
Interest rate (as a percent)							7.50%	7.50%	7.50%		7.50%
Principal amount											$ 40,000
7.5% Convertible Senior Note | Common Stock Forward
Capped Call and Common Stock Forward
Net cost incurred								$ 27,500

Stockholders' Equity - Common S

Stockholders' Equity - Common Stock and Warrants (Details) $ / shares in Units, $ in Thousands	Apr. 13, 2020USD ($)	Feb. 28, 2021USD ($)$ / sharesshares	Jan. 31, 2021USD ($)$ / sharesshares	Nov. 30, 2020USD ($)$ / sharesshares	Aug. 31, 2020USD ($)$ / sharesshares	Dec. 31, 2019USD ($)$ / sharesshares	Mar. 31, 2019USD ($)$ / sharesshares	Feb. 28, 2021$ / sharesshares	Dec. 31, 2020$ / sharesshares	Mar. 31, 2019USD ($)$ / shares	Jun. 30, 2020USD ($)$ / shares	Jun. 30, 2019USD ($)$ / shares	Sep. 30, 2020USD ($)$ / shares	Sep. 30, 2019USD ($)$ / shares	Dec. 31, 2020USD ($)item$ / sharesshares	Dec. 31, 2019USD ($)$ / sharesshares	Dec. 31, 2018USD ($)shares	Dec. 31, 2017shares	Mar. 31, 2020$ / shares
Stockholders' equity
Preferred stock, Shares authorized									5,000,000						5,000,000
Preferred stock, par value | $ / shares									$ 0.01						$ 0.01
Net proceeds from shares of common stock sold | $				$ 927,300	$ 344,400	$ 120,400	$ 23,500			$ 23,498	$ (269)	$ 28,265	$ 344,398	$ 38,098	$ 1,271,714	$ 158,343	$ 7,195
Common Stock Shares, Outstanding						303,378,515			458,051,920						458,051,920	303,378,515
Common Stock, Shares, Issued						318,637,560			473,977,469						473,977,469	318,637,560
Common stock, par value (in dollars per share) | $ / shares						$ 0.01	$ 0.01		$ 0.01	$ 0.01	$ 0.01	$ 0.01	$ 0.01	$ 0.01	$ 0.01	$ 0.01			$ 0.01
Number of votes per share | item															1
Common stock shares issued				43,700,000	35,276,250	46,000,000	10,000,000		4,400,000						79,000,000
Share price (in dollars per share) | $ / shares				$ 22.25	$ 10.25	$ 2.75	$ 2.35			$ 2.35						$ 2.75
Series A Junior Participating Cumulative Preferred Stock
Stockholders' equity
Preferred stock, par value | $ / shares									$ 0.01						$ 0.01
Common Stock Shares, Outstanding						0			0						0	0
At Market Issuance Sales Agreement
Stockholders' equity
Net proceeds from shares of common stock sold | $																$ 14,500	$ 7,000
Common stock shares issued																6,300,000	3,800,000
Authorized amount | $	$ 75,000
Warrant Issued With Amazon And Walmart Stores Inc Transaction Agreement In 2017
Stockholders' equity
Number of warrants exercised (in shares)															68,380,913	26,188,434
Maximum | Warrant Issued With Amazon And Walmart Stores Inc Transaction Agreement In 2017
Stockholders' equity
Class of Warrant or Right Issued																		110,573,392
Subsequent event
Stockholders' equity
Common stock shares issued								32.2
Subsequent event | SK Holdings Co LTD
Stockholders' equity
Net proceeds from shares of common stock sold | $		$ 1,600,000
Common Stock, Shares, Issued		54,966,188						54,966,188
Common stock shares issued		54,996,188
Per share price of shares of common stock | $ / shares		$ 29.2893						$ 29.2893
Subsequent event | Public Offerings
Stockholders' equity
Net proceeds from shares of common stock sold | $		$ 1,800,000	$ 1,800,000
Common stock shares issued		32,200,000	32,200,000
Share price (in dollars per share) | $ / shares		$ 65	$ 65					$ 65

Redeemable Convertible Prefer_2

Redeemable Convertible Preferred Stock (Details) $ in Millions	Nov. 01, 2018shares	May 31, 2020shares	Apr. 30, 2020shares	Jan. 31, 2020shares	Nov. 30, 2018USD ($)shares	Dec. 31, 2019USD ($)shares	Dec. 31, 2020USD ($)installmentshares
Series C Redeemable Convertible Preferred Stock
Redeemable preferred stock
Number of shares of common stock issued on conversion of preferred stock		1,858,256	923,819
Number of preferred shares that had been converted to common stock		1,750	870
Series E Redeemable Convertible Preferred Stock
Redeemable preferred stock
Shares issued (in shares)					35,000
Net proceeds from public offering | $					$ 30.9
Number of monthly installments | installment							13
Redemption value for each installment | $							$ 2.7
Shares outstanding (in shares)						500	0
Preferred stock, dividends | $						$ 1.8
Series E Preferred Stock
Redeemable preferred stock
Shares issued (in shares)	35,000
Number of preferred shares that had been converted to common stock				500		30,462

Warrant Transaction Agreements

Warrant Transaction Agreements - Amazon.com, Inc. Transaction Agreement (Details) $ / shares in Units, $ in Thousands	Dec. 31, 2020USD ($)$ / sharesshares	Nov. 02, 2020USD ($)installment$ / sharesshares	Jan. 01, 2019USD ($)installmentshares	Jul. 20, 2017USD ($)	Apr. 04, 2017USD ($)shares	Dec. 31, 2020$ / sharesshares	Sep. 30, 2020USD ($)	Jun. 30, 2020USD ($)	Mar. 31, 2020USD ($)	Dec. 31, 2019USD ($)shares	Sep. 30, 2019USD ($)	Jun. 30, 2019USD ($)	Mar. 31, 2019USD ($)	Jun. 30, 2020USD ($)	Jun. 30, 2019USD ($)	Sep. 30, 2020USD ($)	Sep. 30, 2019USD ($)	Dec. 31, 2020USD ($)$ / sharesshares	Dec. 31, 2019USD ($)shares	Dec. 31, 2018USD ($)	Jul. 31, 2017shares	Apr. 30, 2017shares
Class of Warrant or Right [Line Items]
Reduction in revenue				$ 10,900														$ 399,700
Selling, general and administrative							$ 17,210	$ 21,644	$ 11,109	$ 9,973	$ 10,395	$ 13,613	$ 9,221	$ 32,753	$ 22,834	$ 49,963	$ 33,229	$ 79,348	$ 43,202	$ 37,685
Exercise price calculation				The exercise price of the third tranche of Walmart Warrant Shares will be an amount per share equal to ninety percent (90%) of the 30-day volume weighted average share price of the common stock as of the final vesting date of the second tranche of Walmart Warrant Shares
Risk-free interest rate	0.58%	0.58%				0.58%												0.58%
Volatility	75.00%	75.00%				75.00%												75.00%
Expected average term	6 years 3 months 3 days	6 years 5 months 1 day
Exercise price | $ / shares	$ 13.81	$ 13.81				$ 13.81												$ 13.81
Stock price | $ / shares	$ 33.91	15.47				$ 33.91												$ 33.91
Warrant Transaction Agreements
Class of Warrant or Right [Line Items]
Shares of common stock that can be purchased from warrants issued (in shares) | shares					55,286,696																55,286,696	55,286,696
Reduction in revenue	$ 399,700																	$ 420,000	$ 4,100	9,800
Warrant shares vested (in shares) | shares	55,286,696					55,286,696				20,368,782								55,286,696	20,368,782
Fair value of warrants per share | $ / shares	$ 26.95	$ 10.57
Tranche one of warrants issued with the Amazon.com, Inc transaction agreement
Class of Warrant or Right [Line Items]
Shares of common stock that can be purchased from warrants issued (in shares) | shares					5,819,652
Cash payments to be received under agreement					$ 600,000
Selling, general and administrative					$ 6,700
Exercise price calculation						$1.1893
Tranche two of warrants issued with the Amazon.com, Inc. Transaction Agreement
Class of Warrant or Right [Line Items]
Cash payments to be received under agreement			$ 50,000
Reduction in revenue																		$ 9,000	$ 4,100	$ 9,800
Warrant shares vested (in shares) | shares			29,098,260
Number of installments | installment			4
Tranche two of warrants issued with the Amazon.com, Inc. Transaction Agreement | Maximum
Class of Warrant or Right [Line Items]
Cash payments to be received under agreement			$ 200,000
Tranche three of warrants issued with the Amazon.com, Inc. Transaction Agreement
Class of Warrant or Right [Line Items]
Cash payments to be received under agreement		$ 50,000
Reduction in revenue																		$ 24,100
Warrant shares vested (in shares) | shares		20,368,784
Number of installments | installment		8
Exercise price of warrants (in dollars per share) | $ / shares	$ 13.81					$ 13.81												$ 13.81
Fair value of warrants per share | $ / shares		$ 10.57
Tranche three of warrants issued with the Amazon.com, Inc. Transaction Agreement | Maximum
Class of Warrant or Right [Line Items]
Cash payments to be received under agreement		$ 400,000
Warrant Issued With Amazon
Class of Warrant or Right [Line Items]
Reduction in revenue																		$ 399,700
Warrant shares vested (in shares) | shares	5,354,905	12,730,490				5,354,905												5,354,905

Warrant Transaction Agreement_2

Warrant Transaction Agreements - Walmart Stores, Inc. Transaction Agreement (Details) $ / shares in Units, $ in Millions	Jul. 20, 2017USD ($)installment$ / sharesshares	Dec. 31, 2020USD ($)shares	Dec. 31, 2019USD ($)shares	Dec. 31, 2018USD ($)
Warrant Transaction Agreements
Reduction in revenue	$ 10.9	$ 399.7
Exercise price calculation	The exercise price of the third tranche of Walmart Warrant Shares will be an amount per share equal to ninety percent (90%) of the 30-day volume weighted average share price of the common stock as of the final vesting date of the second tranche of Walmart Warrant Shares
Warrants issued with the Walmart Stores, Inc transaction agreement
Warrant Transaction Agreements
Shares of common stock that can be purchased from warrants issued (in shares) | shares	55,286,696
Reduction in revenue		$ 5	$ 2.4	$ 0.4
Cash payments to be received under agreement	$ 200
Warrant shares vested (in shares) | shares		5,819,652	13,094,217
Tranche one of warrants issued with the Walmart Stores Inc transaction agreement
Warrant Transaction Agreements
Warrant shares vested (in shares) | shares	5,819,652
Exercise price of warrants (in dollars per share) | $ / shares	$ 2.1231
Tranche two of warrants issued with the Walmart Stores, Inc. Transaction Agreement
Warrant Transaction Agreements
Cash payments to be received under agreement	$ 50
Warrant shares vested (in shares) | shares	29,098,260
Number of installments | installment	4
Number of shares per installment | shares	7,274,565
Tranche three of warrants issued with the Walmart Stores, Inc. Transaction Agreement
Warrant Transaction Agreements
Shares of common stock that can be purchased from warrants issued (in shares) | shares	20,368,784
Cash payments to be received under agreement	$ 50
Number of installments | installment	8
Number of shares per installment | shares	2,546,098
Maximum | Warrants issued with the Walmart Stores, Inc transaction agreement
Warrant Transaction Agreements
Cash payments to be received under agreement	$ 600
Maximum | Tranche two of warrants issued with the Walmart Stores, Inc. Transaction Agreement
Warrant Transaction Agreements
Cash payments to be received under agreement	200
Maximum | Tranche three of warrants issued with the Walmart Stores, Inc. Transaction Agreement
Warrant Transaction Agreements
Cash payments to be received under agreement	$ 400

Revenue - Disaggregation of Rev

Revenue - Disaggregation of Revenue (Details) - USD ($) $ in Thousands	3 Months Ended								6 Months Ended		9 Months Ended		12 Months Ended
	Dec. 31, 2020	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Jun. 30, 2020	Jun. 30, 2019	Sep. 30, 2020	Sep. 30, 2019	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Revenue
Net revenue	$ 309,099	$ 107,048	$ 67,995	$ 40,819	$ 91,607	$ 59,392	$ 57,466	$ 21,510		$ 78,976		$ 138,368
Net revenue		107,048	67,995	40,819	91,607				$ 108,814		$ 215,862		$ (93,237)	$ 229,975	$ 174,215
Sales of fuel cell systems
Revenue
Net revenue													(55,091)	130,757	75,029
Sale of hydrogen installations and other infrastructure
Revenue
Net revenue													(39,204)	19,163	32,146
Services performed on fuel cell systems and related infrastructure
Revenue
Net revenue	(29,387)	6,829	6,236	6,521	7,328	6,205	5,341	6,343	12,757	11,684	19,586	17,889	(9,801)	25,217	22,002
Power Purchase Agreements
Revenue
Net revenue	6,991	6,629	6,579	6,421	6,664	6,520	6,334	6,035	13,000	12,369	19,629	18,889	26,620	25,553	22,569
Fuel delivered to customers
Revenue
Net revenue	(40,608)	9,831	7,372	7,333	7,779	7,649	$ 7,089	$ 6,582	14,705	$ 13,671	24,536	21,320	(16,072)	29,099	$ 22,469
Other
Revenue
Net revenue	$ 76	$ 97	$ 62	$ 76	$ 51	$ 135			$ 138		$ 235	$ 135	$ 311	$ 186

Revenue - Contract balances (De

Revenue - Contract balances (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019
Revenue
Accounts receivable	$ 43,041	$ 113,505	$ 45,782	$ 24,734	$ 25,768	$ 24,737	$ 26,844	$ 32,307
Contract assets	18,189				13,251
Contract liabilities	$ 76,285				$ 40,743

Revenue - Changes in contract a

Revenue - Changes in contract assets and contract liabilities (Details) $ in Thousands	12 Months Ended
	Dec. 31, 2020USD ($)
Contract assets
Transferred to receivables from contract assets recognized at the beginning of the period	$ (5,483)
Revenue recognized and not billed as of the end of the period	10,421
Net change in contract assets	4,938
Contract liabilities
Increases due to cash received, net of amounts recognized as revenue during the period	100,492
Contract liabilities assumed as part of acquisitions	2,350
Revenue recognized that was included in the contract liability balance as of the beginning of the period	(67,300)
Net change in contract liabilities	$ 35,542

Revenue - Estimated future reve

Revenue - Estimated future revenue (Details) $ in Thousands	12 Months Ended
	Dec. 31, 2020USD ($)
Revenue
Total estimated future revenue	$ 367,406
Sales of fuel cell systems
Revenue
Total estimated future revenue	16,209
Sale of hydrogen installations and other infrastructure
Revenue
Total estimated future revenue	28,282
Services performed on fuel cell systems and related infrastructure
Revenue
Total estimated future revenue	75,467
Power Purchase Agreements
Revenue
Total estimated future revenue	178,450
Fuel delivered to customers
Revenue
Total estimated future revenue	65,704
Other
Revenue
Total estimated future revenue	$ 3,294
Maximum | Sales of fuel cell systems
Revenue
Duration of estimated revenue expected to be recognized in future (in years)	1 year
Maximum | Services performed on fuel cell systems and related infrastructure
Revenue
Duration of estimated revenue expected to be recognized in future (in years)	7 years
Maximum | Power Purchase Agreements
Revenue
Duration of estimated revenue expected to be recognized in future (in years)	7 years
Minimum | Services performed on fuel cell systems and related infrastructure
Revenue
Duration of estimated revenue expected to be recognized in future (in years)	5 years
Minimum | Power Purchase Agreements
Revenue
Duration of estimated revenue expected to be recognized in future (in years)	5 years

Revenue - Others (Details)

Revenue - Others (Details) - USD ($) $ in Millions	Dec. 31, 2020	Dec. 31, 2019
Revenue
Capitalized contract costs	$ 1.5	$ 0.5

Employee Benefit Plans - Assump

Employee Benefit Plans - Assumptions For Estimating Fair Value (Details) - USD ($) $ in Millions	May 12, 2011	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Employee Benefit Plans
Compensation cost		$ 14.4	$ 8.8	$ 7.4
Assumptions for estimating fair value
Dividend Yield		0.00%
Stock options
Employee Benefit Plans
Number of options outstanding (in shares)		10,284,498	23,013,590
Compensation cost		$ 6.8	$ 6	$ 6.4
Stock options granted		3,509,549	3,221,892	2,679,667
Assumptions for estimating fair value
Expected term of options (years)		6 years	6 years	6 years
Stock options | Minimum
Assumptions for estimating fair value
Risk free rate (as a percent):		0.37%	1.52%	2.81%
Volatility (as a percent):		64.19%	69.32%	98.31%
Stock options | Maximum
Assumptions for estimating fair value
Risk free rate (as a percent):		1.37%	2.53%	2.88%
Volatility (as a percent):		68.18%	87.94%	98.89%
the 2011 Plan | Stock options
Employee Benefit Plans
Maximum number of common stock shares available for issuance	1,000,000	42,400,000
Aggregate number of options granted (in shares)		10,200,000
Number of options available for issuance (in shares)		800,000
Expiration period		10 years
Stock options granted	0
the 2011 Plan | Stock options | Minimum
Employee Benefit Plans
Vesting period		1 year
the 2011 Plan | Stock options | Maximum
Employee Benefit Plans
Vesting period		3 years
the 2011 Plan | Employees | Stock options
Employee Benefit Plans
Vesting period		3 years
Expiration period		10 years
the 2011 Plan | Board of Directors | Stock options
Employee Benefit Plans
Vesting period		1 year

Employee Benefit Plans - Stock

Employee Benefit Plans - Stock Activity, Weighted Average Exercise Price (Details) - Stock options - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Shares
Options outstanding, beginning balance (in shares)	23,013,590
Granted (in shares)	3,509,549	3,221,892	2,679,667
Exercised (in shares)	(16,159,742)
Forfeited (in shares)	(73,249)
Expired (in shares)	(5,650)
Options outstanding, end balance (in shares)	10,284,498	23,013,590
Options exercisable (in shares)	4,084,124
Options unvested (in shares)	6,200,374
Weighted Average Exercise Price
Options outstanding, beginning balance, weighted-average exercise price	$ 2.48
Granted, weighted-average exercise price	12.79
Exercised, weighted-average exercise price	2.55
Forfeited, weighted-average exercise price	6.32
Expired, weighted-average exercise price	4.78
Options outstanding, end balance, weighted-average exercise price	5.78	$ 2.48
Options exercisable, weighted-average exercise price	2.31
Options unvested, weighted-average exercise price	$ 8.07
Stock option activity additional disclosures
Options outstanding, weighted-average remaining contractual term	7 years 9 months 18 days	6 years 7 months 6 days
Options exercisable, weighted-average remaining contractual term	5 years 9 months 18 days
Options unvested, weighted-average remaining contractual term	9 years 1 month 6 days
Options outstanding, aggregate intrinsic value	$ 289,316	$ 22,277
Options exercisable, aggregate intrinsic value	129,068
Options unvested, aggregate intrinsic value	$ 160,248
Weighted-average grant date fair value of options granted (per share)	$ 7.22	$ 1.67	$ 1.55
Unrecognized compensation cost	$ 8,100
Period for recognition	3 years
Fair value of stock options that vested during the period	$ 5,900	$ 6,100

Employee Benefit Plans - Restri

Employee Benefit Plans - Restricted Stock Activity (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Employee Benefit Plans
Compensation cost	$ 14,400	$ 8,800	$ 7,400
Restricted stock
Employee Benefit Plans
Compensation cost	7,600	2,800	966
Unrecognized compensation cost	$ 41,500	$ 8,400	$ 3,900
Period for recognition	3 years
Shares
Unvested restricted stock, beginning balance (in shares)	4,608,560
Granted (in shares)	3,227,149
Vested (in shares)	(1,896,901)
Forfeited (in shares)	(64,166)
Unvested restricted stock, end balance (in shares)	5,874,642	4,608,560
Aggregate Intrinsic Value
Unvested restricted stock aggregate intrinsic value	$ 199,209
Restricted stock | Minimum
Employee Benefit Plans
Vesting period	1 year
Restricted stock | Maximum
Employee Benefit Plans
Vesting period	3 years

Employee Benefit Plans - 401(K)

Employee Benefit Plans - 401(K) Saving And Retirement Plan (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Employee Benefit Plan Compensation
Compensation cost	$ 14,400	$ 8,800	$ 7,400
Non Employee Director
Employee Benefit Plan Compensation
Granted (in shares)	36,175	114,285	107,389
Compensation cost	$ 228	$ 243	$ 261
Savings And Retirement Plan 401 K
401(K) Savings & Retirement Plan
Percent of salary employee is permitted to contribute	100.00%
Vesting period	3 years
Common stock, shares issued	403,474	841,539
Total expense (including issuance of shares)	$ 2,600	$ 1,900	$ 1,800

Income Taxes - Components Of In

Income Taxes - Components Of Income Tax (Details) - USD ($) $ in Thousands	3 Months Ended							6 Months Ended		9 Months Ended		12 Months Ended
	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Jun. 30, 2020	Jun. 30, 2019	Sep. 30, 2020	Sep. 30, 2019	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Components of loss before income taxes and income tax benefit
Loss before income taxes	$ (71,861)	$ (26,772)	$ (37,432)	$ (18,036)	$ (17,822)	$ (17,338)	$ (30,547)	$ (64,204)	$ (47,885)	$ (136,065)	$ (65,707)	$ (627,000)	$ (83,743)	$ (94,903)
Income tax benefit	6,644	17,371						17,371		24,015		30,845		9,295
Net loss attributable to the Company	$ (65,217)	$ (9,401)	$ (37,432)	$ (18,036)	$ (17,822)	$ (17,338)	$ (30,547)	$ (46,833)	$ (47,885)	$ (112,050)	$ (65,707)	(596,155)	(83,743)	(85,608)
Significant components of deferred income tax expense (benefit)
Deferred tax (benefit) expense												(31,475)	(11,047)	(10,812)
Net operating loss carryforward generated												(52,287)	(5,369)	(10,986)
Valuation allowance increase (decrease)												52,917	16,416	12,503
U.S.
Components of loss before income taxes and income tax benefit
Loss before income taxes												(624,302)	(82,188)	(93,497)
Income tax benefit												30,845		9,295
Net loss attributable to the Company												(593,457)	(82,188)	(84,201)
Significant components of deferred income tax expense (benefit)
Deferred tax (benefit) expense												(31,408)	(10,621)	(11,745)
Net operating loss carryforward generated												(51,849)	(5,099)	(10,321)
Valuation allowance increase (decrease)												52,412	15,720	12,771
Foreign
Components of loss before income taxes and income tax benefit
Loss before income taxes												(2,698)	(1,555)	(1,407)
Net loss attributable to the Company												(2,698)	(1,555)	(1,407)
Significant components of deferred income tax expense (benefit)
Deferred tax (benefit) expense												(67)	(426)	933
Net operating loss carryforward generated												(438)	(270)	(665)
Valuation allowance increase (decrease)												$ 505	$ 696	$ (268)

Income Taxes - Effective Income

Income Taxes - Effective Income Tax Rate Reconciliation (Details)	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Effective income tax rate reconciliation
U.S. Federal statutory tax rate	(21.00%)	(21.00%)	(21.00%)
Deferred state taxes	(2.30%)	1.40%	(1.90%)
Common stock warrant liability	13.40%		(1.00%)
Other, net	(3.40%)	(0.50%)	0.90%
Change in valuation allowance	8.40%	20.10%	13.20%
Total effective income tax rate	(4.90%)	0.00%	(9.80%)

Income Taxes - Deferred Tax Ass

Income Taxes - Deferred Tax Assets And Liabilities (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Significant components of the Company's deferred tax assets and liabilities
Intangible assets	$ 1,197	$ 1,197
Deferred revenue	16,274	8,051
Interest expense	21,183	10,216
Other reserves and accruals	5,087	1,504
Tax credit carryforwards	5,613	3,843
Amortization of stock-based compensation	3,900	9,081
Non-Compensatory warrants	5,020	4,322
Capitalized research & development expenditures	35,353	27,084
Right of use liability (operating leases)	27,715	22,647
Net operating loss carryforwards	120,992	64,014
Total deferred tax asset	242,334	151,959
Valuation allowance	(171,594)	(118,677)
Net deferred tax assets	70,740	33,282
Intangible assets	(7,360)	(15)
Convertible debt	(27,420)	(6,592)
Right of use asset (operating leases)	(27,684)	(23,040)
Other reserves and accruals	(12)	(16)
Property, plant and equipment and right of use assets	(9,191)	(3,619)
Deferred tax liability	(71,667)	(33,282)
Net	(927)
Deferred tax assets, valuation allowance	171,600	118,700
U.S.
Significant components of the Company's deferred tax assets and liabilities
Deferred revenue	16,082	7,922
Interest expense	21,183	10,216
Other reserves and accruals	5,087	1,504
Tax credit carryforwards	4,360	2,590
Amortization of stock-based compensation	3,900	9,081
Non-Compensatory warrants	5,020	4,322
Capitalized research & development expenditures	30,870	22,601
Right of use liability (operating leases)	27,715	22,647
Net operating loss carryforwards	110,978	54,438
Total deferred tax asset	225,195	135,321
Valuation allowance	(154,467)	(102,055)
Net deferred tax assets	70,728	33,266
Intangible assets	(7,360)	(15)
Convertible debt	(27,420)	(6,592)
Right of use asset (operating leases)	(27,684)	(23,040)
Property, plant and equipment and right of use assets	(9,191)	(3,619)
Deferred tax liability	(71,655)	(33,266)
Net	(927)
Foreign
Significant components of the Company's deferred tax assets and liabilities
Intangible assets	1,197	1,197
Deferred revenue	192	129
Tax credit carryforwards	1,253	1,253
Capitalized research & development expenditures	4,483	4,483
Net operating loss carryforwards	10,014	9,576
Total deferred tax asset	17,139	16,638
Valuation allowance	(17,127)	(16,622)
Net deferred tax assets	12	16
Other reserves and accruals	(12)	(16)
Deferred tax liability	$ (12)	$ (16)

Income Taxes - Change In Valuat

Income Taxes - Change In Valuation Allowance (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Change in valuation allowance
Increase in valuation allowance for current year increase in net operating losses	$ 51,848
Increase (decrease) in valuation allowance for current year net increase (decrease) in deferred tax assets other than net operating losses	(5,609)
Decrease in valuation allowance as a result of foreign currency fluctuation	6,306
Increase in valuation allowance due to change in tax rates	372
Net increase in valuation allowance	52,917	$ 16,416	$ 12,503
U.S.
Change in valuation allowance
Increase in valuation allowance for current year increase in net operating losses	51,848
Increase (decrease) in valuation allowance for current year net increase (decrease) in deferred tax assets other than net operating losses	(5,742)
Decrease in valuation allowance as a result of foreign currency fluctuation	6,306
Net increase in valuation allowance	52,412	15,720	12,771
Foreign
Change in valuation allowance
Increase (decrease) in valuation allowance for current year net increase (decrease) in deferred tax assets other than net operating losses	133
Increase in valuation allowance due to change in tax rates	372
Net increase in valuation allowance	$ 505	$ 696	$ (268)

Income Taxes - Unrecognized Tax

Income Taxes - Unrecognized Tax Benefits (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Income taxes
Pre-change net operating losses that can be used in future years	$ 13,500
Net operating losses not subject to IRC section 382	450,900
Deferred tax assets, U.S. net operating loss carryforwards	464,400
Amount of net operating loss carryforwards that will expire due to IRC Section 382 limitations	4,400
Net operating loss carryforwards	120,992	$ 64,014
Un-repatriated foreign earnings	0
Restated adjustment
Income taxes
Net operating loss carryforwards	205,200	25,000	$ 43,400
Canada
Income taxes
Research and experimental development expenditure carryforwards	17,200
Canadian ITC credit carryforwards	1,300
Foreign
Income taxes
Net operating loss carryforwards	10,014	$ 9,576
Foreign | French
Income taxes
Unused net operating loss carryforwards	21,300
Foreign | Canada
Income taxes
Net operating loss carryforwards	$ 14,000

Income Taxes (Details)

Income Taxes (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended	9 Months Ended	12 Months Ended
	Sep. 30, 2020	Jun. 30, 2020	Jun. 30, 2020	Sep. 30, 2020	Dec. 31, 2020	Dec. 31, 2018	May 31, 2020	May 29, 2020	May 18, 2020	Mar. 31, 2018
Deferred income tax benefit	$ (6,644)	$ (17,371)	$ (17,371)	$ (24,015)	$ (30,845)	$ (9,295)
Interest rate (as a percent)							3.50%
Giner ELX, Inc
Income tax benefit related to deferred taxes					5,200
3.75% Convertible Senior Notes
Future taxable income attributable to the net credit to additional paid-in capital					$ 25,600
Interest rate (as a percent)					3.75%		3.75%	3.75%	3.75%
5.5% Convertible Senior Notes
Interest rate (as a percent)					5.50%		5.50%		5.50%	5.50%

Commitments and Contingencies -

Commitments and Contingencies - Concentrations of Credit Risk (Details) $ in Thousands	Dec. 31, 2020USD ($)customer	Jul. 20, 2017USD ($)	Sep. 30, 2020USD ($)	Jun. 30, 2020USD ($)	Mar. 31, 2020USD ($)	Dec. 31, 2019USD ($)customer	Jun. 30, 2020USD ($)	Sep. 30, 2020USD ($)	Dec. 31, 2020USD ($)customer	Dec. 31, 2019USD ($)customer	Dec. 31, 2018USD ($)customer
Customer Concentration
Restricted cash	$ 169,000								$ 169,000
Letter of credit	152,400								152,400
Reduction in revenue		$ 10,900							399,700
Consolidated revenue			$ 107,048	$ 67,995	$ 40,819	$ 91,607	$ 108,814	$ 215,862	(93,237)	$ 229,975	$ 174,215
Letter of Credit
Customer Concentration
Letter of credit	$ 500								$ 500
Accounts receivable | Customer concentration | Customers
Customer Concentration
Number of customers | customer	3					2			3	2
Concentration risk (as a percent)									73.90%	62.60%
Revenues | Customer concentration | Customers
Customer Concentration
Number of customers | customer	2					2			2	2	2
Concentration risk (as a percent)									156.20%	49.70%	66.80%
Warrant Transaction Agreements
Customer Concentration
Reduction in revenue	$ 399,700								$ 420,000	$ 4,100	$ 9,800
Warrant Transaction Agreements | Revenues | Customer concentration | Amazon
Customer Concentration
Consolidated revenue									$ 310,100
Concentration risk (as a percent)									332.40%
Provision for common stock warrants									$ 420,000

Subsequent Events (Details)

Subsequent Events (Details) - USD ($) $ / shares in Units, $ in Thousands	1 Months Ended						2 Months Ended	3 Months Ended			6 Months Ended		9 Months Ended		12 Months Ended
	Feb. 28, 2021	Jan. 31, 2021	Nov. 30, 2020	Aug. 31, 2020	Dec. 31, 2019	Mar. 31, 2019	Feb. 28, 2021	Dec. 31, 2020	Mar. 31, 2020	Mar. 31, 2019	Jun. 30, 2020	Jun. 30, 2019	Sep. 30, 2020	Sep. 30, 2019	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018	May 31, 2020	May 29, 2020	May 18, 2020
Subsequent Events
Public offerings, common stock, net (in shares)			43,700,000	35,276,250	46,000,000	10,000,000		4,400,000							79,000,000
Proceeds from public offerings, net of transaction costs			$ 927,300	$ 344,400	$ 120,400	$ 23,500				$ 23,498	$ (269)	$ 28,265	$ 344,398	$ 38,098	$ 1,271,714	$ 158,343	$ 7,195
Conversion of preferred stock to common stock									$ 441		$ 441		$ 43,058	$ 1,883	$ 1,179	$ 28,392
Interest rate (as a percent)																		3.50%
Common stock, shares issued					318,637,560			473,977,469							473,977,469	318,637,560
Share price (in dollars per share)			$ 22.25	$ 10.25	$ 2.75	$ 2.35				$ 2.35						$ 2.75
3.75% Convertible Senior Notes
Subsequent Events
Interest rate (as a percent)								3.75%							3.75%			3.75%	3.75%	3.75%
Share price (in dollars per share)								$ 33.91							$ 33.91
Subsequent event
Subsequent Events
Public offerings, common stock, net (in shares)							32.2
Subsequent event | SK Holdings Co LTD
Subsequent Events
Public offerings, common stock, net (in shares)	54,996,188
Per share price of shares of common stock	$ 29.2893						$ 29.2893
Proceeds from public offerings, net of transaction costs	$ 1,600,000
Common stock, shares issued	54,966,188						54,966,188
Subsequent event | 3.75% Convertible Senior Notes
Subsequent Events
Conversion of preferred stock to common stock	$ 15,200	$ 15,200					$ 15,200
Interest rate (as a percent)	3.75%	3.75%					3.75%
Conversion of notes through common stock issuance	3,000,000	3,000,000					3,000,000
Subsequent event | Public Offerings
Subsequent Events
Public offerings, common stock, net (in shares)	32,200,000	32,200,000
Proceeds from public offerings, net of transaction costs	$ 1,800,000	$ 1,800,000
Share price (in dollars per share)	$ 65	$ 65					$ 65