Plug Power (PLUG) 10-K 9 Mar 20 2019 FY Annual report Financial data

Document and Entity Information

Document and Entity Information - USD ($)	12 Months Ended
	Dec. 31, 2019	Mar. 09, 2020	Jun. 28, 2019
Document and Entity Information:
Document Type	10-K
Document Period End Date	Dec. 31, 2019
Entity Registrant Name	Plug Power Inc
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Entity Filer Category	Accelerated Filer
Entity Small Business	false
Entity Emerging Growth Company	false
Entity Shell Company	false
Entity Common Stock, Shares Outstanding		321,289,882
Entity Central Index Key	0001093691
Current Fiscal Year End Date	--12-31
Document Fiscal Period Focus	FY
Document Fiscal Year Focus	2019
Amendment Flag	false
Entity Well-known Seasoned Issuer	No
Entity Voluntary Filers	No
Entity Public Float			$ 521,797,028

CONSOLIDATED BALANCE SHEETS

CONSOLIDATED BALANCE SHEETS - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Current assets:
Cash and cash equivalents	$ 139,496	$ 38,602
Restricted cash	54,813	17,399
Accounts receivable	25,448	37,347
Inventory	72,391	47,910
Prepaid expenses and other current assets	21,192	14,357
Total current assets	313,340	155,615
Restricted cash	175,191	54,152
Property, plant, and equipment, net	14,959	12,869
Leased property, net	244,740	146,751
Goodwill	8,842	9,023
Intangible assets, net	5,539	3,890
Other assets	8,573	8,026
Total assets	771,184	390,326
Current liabilities:
Accounts payable	40,376	34,824
Accrued expenses	14,213	7,864
Deferred revenue	11,691	12,055
Finance obligations	49,507	74,264
Current portion of long-term debt	26,461	16,803
Other current liabilities	8,543	560
Total current liabilities	150,791	146,370
Deferred revenue	23,369	28,021
Common stock warrant liability		105
Finance obligations	265,228	118,076
Convertible senior notes, net	110,246	63,247
Long-term debt	85,708	133
Other liabilities	13	18
Total liabilities	635,355	355,970
Stockholders' equity:
Common stock, $0.01 par value per share; 750,000,000 shares authorized; Issued (including shares in treasury): 318,637,560 at December 31, 2019 and 234,160,661 at December 31, 2018	3,186	2,342
Additional paid-in capital	1,507,116	1,289,714
Accumulated other comprehensive income	1,400	1,584
Accumulated deficit	(1,345,807)	(1,260,290)
Less common stock in treasury: 15,259,045 at December 31, 2019 and 15,002,663 at December 31, 2018	(31,216)	(30,637)
Total stockholders' equity	134,679	2,713
Total liabilities, redeemable preferred stock, and stockholders' equity	771,184	390,326
Series C Redeemable Convertible Preferred Stock
Redeemable preferred stock:
Redeemable preferred stock	709	709
Series E Redeemable Convertible Preferred Stock
Redeemable preferred stock:
Redeemable preferred stock	$ 441	$ 30,934

CONSOLIDATED BALANCE SHEETS (Pa

CONSOLIDATED BALANCE SHEETS (Parentheticals) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Common stock, par value (in dollars per share)	$ 0.01	$ 0.01
Common stock, shares authorized	750,000,000	750,000,000
Common stock, shares issued	318,637,560	234,160,661
Common stock in treasury, shares	15,259,045	15,002,663
Series C Redeemable Convertible Preferred Stock
Redeemable convertible Preferred Stock, par value (in dollars per share)	$ 0.01	$ 0.01
Redeemable convertible Preferred Stock, shares authorized	10,431	10,431
Redeemable convertible Preferred Stock, shares issued	2,620	2,620
Redeemable convertible Preferred Stock, shares outstanding	2,620	2,620
Redeemable convertible Preferred Stock, aggregate involuntary liquidation preference (in dollars)	$ 16,664	$ 16,664
Series E Redeemable 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	500	35,000
Redeemable convertible Preferred Stock, shares outstanding	500	35,000

CONSOLIDATED STATEMENTS OF OPER

CONSOLIDATED STATEMENTS OF OPERATIONS - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Net revenue:
Net revenue	$ 230,239	$ 174,632	$ 100,153
Cost of revenue:
Total cost of revenue	202,273	172,010	128,242
Gross profit (loss)	27,966	2,622	(28,089)
Operating expenses:
Research and development	33,675	33,907	28,693
Selling, general and administrative	44,333	38,198	45,010
Total operating expenses	78,008	72,105	73,703
Operating loss	(50,042)	(69,483)	(101,792)
Interest and other expense, net	(35,502)	(22,135)	(10,100)
Change in fair value of common stock warrant liability	79	4,286	(15,188)
Loss before income taxes	(85,465)	(87,332)	(127,080)
Income tax benefit		9,217
Net loss attributable to the Company	(85,465)	(78,115)	(127,080)
Preferred stock dividends declared and accretion of discount	(52)	(52)	(3,098)
Net loss attributable to common stockholders	$ (85,517)	$ (78,167)	$ (130,178)
Net loss per share:
Basic and diluted	$ (0.36)	$ (0.36)	$ (0.60)
Weighted average number of common stock outstanding	237,152,780	218,882,337	216,343,985
Sales of fuel cell systems and related infrastructure
Net revenue:
Net revenue	$ 149,884	$ 107,292	$ 62,631
Cost of revenue:
Total cost of revenue	96,859	84,439	54,815
Services performed on fuel cell systems and related infrastructure
Net revenue:
Net revenue	25,217	22,002	16,202
Cost of revenue:
Total cost of revenue	28,801	23,698	19,814
Power Purchase Agreements
Net revenue:
Net revenue	25,853	22,869	12,869
Cost of revenue:
Total cost of revenue	40,056	36,161	31,292
Fuel delivered to customers
Net revenue:
Net revenue	29,099	22,469	8,167
Cost of revenue:
Total cost of revenue	36,357	$ 27,712	22,013
Other
Net revenue:
Net revenue	186		284
Cost of revenue:
Total cost of revenue	$ 200		$ 308

CONSOLIDATED STATEMENTS OF COMP

CONSOLIDATED STATEMENTS OF COMPREHENSIVE LOSS - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
CONSOLIDATED STATEMENTS OF COMPREHENSIVE LOSS
Net loss attributable to the Company	$ (85,465)	$ (78,115)	$ (127,080)
Other comprehensive (loss) income - foreign currency translation adjustment	(184)	(610)	1,947
Comprehensive loss	$ (85,649)	$ (78,725)	$ (125,133)

CONSOLIDATED STATEMENTS OF STOC

CONSOLIDATED STATEMENTS OF STOCKHOLDERS EQUITY - USD ($) $ in Thousands	Common StockSeries C Redeemable Convertible Preferred Stock	Common StockSeries D Redeemable Convertible Preferred Stock	Common Stock	Additional Paid-in-CapitalSeries C Redeemable Convertible Preferred Stock	Additional Paid-in-CapitalSeries D Redeemable Convertible Preferred Stock	Additional Paid-in-Capital	Accumulated Other Comprehensive Income	Treasury Stock	Accumulated Deficit	Series C Redeemable Convertible Preferred Stock	Series D Redeemable Convertible Preferred Stock	Total
Balance at Dec. 31, 2016			$ 1,917			$ 1,137,482	$ 247	$ (3,091)	$ (1,051,467)			$ 85,088
Balance (in shares) at Dec. 31, 2016			191,723,974					582,328
Increase (Decrease) in Stockholders' Equity
Net loss attributable to the Company									(127,080)			(127,080)
Other comprehensive income/loss							1,947					1,947
Stock-based compensation			$ 1			9,208						9,209
Stock-based compensation (in shares)			148,077
Stock dividend			$ 1			88			(89)
Stock dividend (in shares)			54,130
Public offerings, common stock, net			$ 102			22,890						22,992
Public offerings, common stock, net (in shares)			10,170,759
Stock option exercises			$ 2			106		$ (11)				97
Stock option exercises (in shares)			154,166					4,823
Exercise of warrants			$ 145			39,713						39,858
Exercise of warrants (in shares)			14,501,500
Conversion of preferred stock	$ 28	$ 95		$ 416	$ 7,683					$ 444	$ 7,778
Conversion of preferred stock (in shares)	2,772,518	9,548,393
Provision for common stock warrants						36,322						36,322
Accretion of discount						(3,009)						(3,009)
Balance at Dec. 31, 2017			$ 2,291			1,250,899	2,194	$ (3,102)	(1,178,636)			73,646
Balance (in shares) at Dec. 31, 2017			229,073,517					587,151
Increase (Decrease) in Stockholders' Equity
Net loss attributable to the Company									(78,115)			(78,115)
Other comprehensive income/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						28,664						28,664
Purchase of capped call						(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			1,289,714	1,584	$ (30,637)	(1,260,290)			$ 2,713
Balance (in shares) at Dec. 31, 2018			234,160,661					15,002,663				234,160,661
Increase (Decrease) in Stockholders' Equity
Cumulative effect from adoption of ASC 842									(3,487)			$ (3,487)
Net loss attributable to the Company									(85,465)			(85,465)
Other comprehensive income/loss							(184)					(184)
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			157,807						158,429
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
Conversion of preferred stock (in shares)			13,845,468
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
Balance at Dec. 31, 2019			$ 3,186			$ 1,507,116	$ 1,400	$ (31,216)	$ (1,345,807)			$ 134,679
Balance (in shares) at Dec. 31, 2019			318,637,560					15,259,045				318,637,560

CONSOLIDATED STATEMENTS OF CASH

CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Operating Activities
Net loss attributable to the Company	$ (85,465)	$ (78,115)	$ (127,080)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation of property, plant and equipment, and leased property	11,989	11,014	9,190
Amortization of intangible assets	698	693	593
Stock-based compensation	10,890	8,771	9,209
Provision for bad debts and other assets	1,981	1,626	250
Amortization of debt issuance costs and discount on convertible senior notes	8,821	6,347	770
Provision for common stock warrants	6,513	10,190	36,360
Change in fair value of common stock warrant liability	(79)	(4,286)	15,188
Loss on disposal of leased assets	212
Income tax benefit		(9,217)
Changes in operating assets and liabilities that provide (use) cash:
Accounts receivable	10,646	(14,398)	(9,951)
Inventory	(24,481)	19,041	(18,836)
Prepaid expenses, and other assets	(8,110)	(4,654)	2,157
Accounts payable, accrued expenses, and other liabilities	19,879	(10,266)	11,430
Accrual for loss contracts related to service			(752)
Deferred revenue	(5,016)	5,637	11,290
Net cash used in operating activities	(51,522)	(57,617)	(60,182)
Investing Activities
Purchases of property, plant and equipment	(5,683)	(5,142)	(4,090)
Purchase of intangible asset	(2,404)	(929)
Purchases for construction of leased property	(6,532)	(13,501)	(40,273)
Proceeds from sale of leased assets	375
Net cash used in investing activities	(14,244)	(19,572)	(44,363)
Financing Activities
Proceeds from issuance of preferred stock and warrants, net of transaction costs	14,089	30,934	17,636
Proceeds from public offerings, net of transaction costs	158,428	7,195	22,992
Proceeds from exercise of stock options	1,217	138	97
Payments for redemption of preferred stock	(4,040)		(3,700)
Proceeds from issuance of convertible senior notes, net	39,052	95,856
Purchase of capped call and common stock forward		(43,500)
Proceeds from borrowing of long-term debt, net of transaction costs	119,186		20,147
Principal payments on long-term debt	(24,827)	(16,190)	(12,292)
Proceeds from sale/leaseback transactions accounted for as finance obligations	83,668	76,175	45,368
Repayments of finance obligations	(61,713)	(31,264)	(18,632)
Net cash provided by financing activities	325,060	119,344	71,616
Effect of exchange rate changes on cash	53	(57)	348
Increase (decrease) in cash, cash equivalents and restricted cash	259,347	42,098	(32,581)
Cash, cash equivalents, and restricted cash beginning of period	110,153	68,055	100,636
Cash, cash equivalents, and restricted cash end of period	369,500	110,153	68,055
Supplemental disclosure of cash flow information
Cash paid for interest	19,180	13,057	8,791
Summary of non-cash investing and financing activity
Recognition of right of use asset	127,370	79,057
Net transfers between inventory, leased assets and property, plant and equipment		$ 18,175
Conversion of preferred stock to common stock	$ 28,392		$ 8,222

Nature of Operations

Nature of Operations	12 Months Ended
	Dec. 31, 2019
Nature of Operations
Nature of Operations	1. Nature of Operations Description of Business As a leading provider of comprehensive hydrogen fuel cell turnkey solutions, Plug Power is seeking to build a green hydrogen economy. The Company is focused on hydrogen and fuel cell systems that are used to power electric motors primarily in the electric mobility and stationary power markets, given the ongoing paradigm shift in the power, energy, and transportation industries to address climate change, energy security, and meet sustainability goals. Plug Power created the first commercially viable market for hydrogen fuel cell, or the HFC technology. As a result, the Company has deployed over 30,000 fuel cell systems, and has become the largest buyer of liquid hydrogen, having built and operated a hydrogen network across North America. We are focused on proton exchange membrane, or PEM, fuel cell and fuel processing technologies, fuel cell/battery hybrid technologies, and associated hydrogen storage and dispensing infrastructure from which multiple products are available. A fuel cell is an electrochemical device that combines hydrogen and oxygen to produce electricity and heat without combustion. Hydrogen is derived from hydrocarbon fuels such as liquid petroleum gas, or LPG, natural gas, propane, methanol, ethanol, gasoline or biofuels. Plug Power develops complete hydrogen generation, delivery, storage and refueling solutions for customer locations. Currently, the Company obtains the majority of its hydrogen by purchasing it from fuel suppliers for resale to customers. We provide and continue to develop commercially-viable hydrogen and fuel cell solutions for 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 and ground support equipment; GenFuel: GenFuel is our 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 PEM fuel cell power to support the backup and grid-support power requirements of the telecommunications, transportation, and utility sectors; 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; and 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. We provide our products worldwide through our direct product sales force, and by leveraging relationships with original equipment manufacturers, and their dealer networks. We manufacture our commercially-viable products in Latham, NY and Spokane, WA. We were organized as a corporation in the State of Delaware on June 27, 1997. Unless the context indicates otherwise, the terms “Company,” “Plug Power,” “we,” “our” or “us” as used herein refers to Plug Power Inc. and its subsidiaries. Liquidity Our cash requirements relate primarily to working capital needed to operate and grow our business, including funding operating expenses, growth in inventory to support both shipments of new units and servicing the installed base, growth in equipment leased to customers under long-term arrangements, funding the growth in our GenKey “turn-key” solution, which includes the installation of our customers’ hydrogen infrastructure as well as delivery of the hydrogen fuel, continued development and expansion of our products, payment of lease/financing obligations under sale/leaseback financings, and the repayment or refinancing of our long-term debt. Our ability to achieve profitability and meet future liquidity needs and capital requirements will depend upon numerous factors, including the timing and quantity of product orders and shipments; attaining and expanding positive gross margins across all product lines; the timing and amount of our operating expenses; the timing and costs of working capital needs; the timing and costs of developing marketing and distribution channels; the ability of our customers to obtain financing to support commercial transactions; our ability to obtain financing arrangements to support the sale or leasing of our products and services to customers and to repay or refinance our long-term debt, and the terms of such agreements that may require us to pledge or restrict substantial amounts of our cash to support these financing arrangements; the timing and costs of developing marketing and distribution channels; the timing and costs of product service requirements; the timing and costs of hiring and training product staff; the timing and costs of product development and introductions; the extent of our ongoing and new research and development programs; and changes in our strategy or our planned activities. If we are unable to fund our operations with positive cash flows and cannot obtain external financing, we may not be able to sustain future operations. As a result, we may be required to delay, reduce and/or cease our operations and/or seek bankruptcy protection. We have experienced and continue to experience negative cash flows from operations and net losses. The Company incurred net losses attributable to common stockholders of $85.5 million, $78.2 million and $130.2 million for the years ended December 31, 2019, 2018, and 2017, respectively, and had an accumulated deficit of $1.3 billion at December 31, 2019. We have historically funded our operations primarily through public and private offerings of During the year ended December 31, 2019, net cash used in operating activities was $51.5 million, consisting primarily of a net loss attributable to the Company of $85.5 million, and net outflows from fluctuations in working capital and other assets and liabilities of $7.1 million, offset by the impact of noncash charges of $41.0 million,. The changes in working capital primarily were related to decreases in accounts receivable and deferred revenue, offset by increases in inventory, prepaid expenses, other current assets, accounts payable, accrued expenses, and other liabilities. Cash outflows related to equipment that we sell are included in net cash used on operating activities. As of December 31, 2019, we had cash and cash equivalents of $139.5 million and net working capital of $162.5 million. By comparison, at December 31, 2018, we had cash and cash equivalents of $38.6 million and net working capital of $9.2 million. Net cash used in investing activities for the year ended December 31, 2019, totaled $14.2 million and included purchases of property, plant and equipment and intangible assets and outflows associated with materials, labor, and overhead necessary to construct new leased property. Cash outflows related to equipment that we lease directly to customers are included in net cash used in investing activities. Net cash provided by financing activities for the year ended December 31, 2019 totaled $325.1 million and primarily resulted from the net proceeds from the issuance of preferred stock and warrants of $14.1 million, net proceeds from public offerings of our equity of $158.4 million, proceeds from the exercise of stock options of $1.2 million, net proceeds of $39.1 million from the issuance of the $40 million Convertible Senior Note, proceeds from the issuance of long-term debt of $119.2 million and increase in finance obligations of $83.7 million, offset by payments for redemption of preferred stock of $4.0 million and repayments of long-term debt of $24.8 million and finance obligations of $61.7 million. Public and Private Offerings of Equity and Debt Common Stock Issuance On April 3, 2017, the Company entered into an At Market Issuance Sales Agreement, or the Sales Agreement, with FBR Capital Markets & Co. (now B. Riley FBR, Inc.) , or FBR, as sales agent, pursuant to which the Company may offer and sell, from time to time through FBR, shares of common stock par value $0.01 per share having an aggregate offering price of up to $75.0 million. During the year ended December 31, 2019, the Company issued 6.3 million shares of common stock through its Sales Agreement resulting in net proceeds of $14.5 million. As of December 2, 2019, the Company had raised a total of $46.8 million during the term of the Sales Agreement. On December 2, 2019, the Sale Agreement expired. In December 2019, the Company sold 46 million shares of common stock at a public price of $2.75 per share for net proceeds of approximately $120.4 million. In March 2019, the Company sold 10 million shares of common stock at a purchase price of $2.35 per share for net proceeds of $23.5 million. Preferred Stock Issuance In November 2018, the Company completed a private placement of an aggregate of 35,000 shares of the Company’s Series E Redeemable Convertible Preferred Stock, par value $0.01 per share, or the Series E Preferred Stock, for net proceeds of approximately $30.9 million. In the third quarter of 2019, the Company redeemed 4,038 shares of Series E Preferred Stock totaling $4.0 million. In the fourth quarter of 2019, the Company converted 30,962 shares of Series E Preferred Stock into 13.8 million shares of common stock. In January 2020, the Company converted the remainder of the 500 shares of Series E Preferred Stock into 216 thousand shares of common stock. See Note 12, Redeemable Convertible Preferred Stock, for additional information. Debt In September 2019, the Company issued a $40.0 million in aggregate principal amount of 7.5% convertible senior note due in 2023, which we refer to herein as the $40 million Convertible Senior Note. The Company’s total obligation, net of interest accretion, due to the holder is $48.0 million. The total net proceeds from this offering, after deducting costs of the issuance were $39.1 million. As of December 31, 2019, the outstanding balance of the note, net of related discount and issuance costs, was $39.6 million. See Note 10, Convertible Senior Notes, for more details. In March 2018, the Company issued $100.0 million in aggregate principal amount of 5.5% convertible senior notes due in 2023, which we refer to herein as the $100 million Convertible Senior Notes. The total net proceeds from this offering, after deducting costs of the issuance, were approximately $95.9 million. Approximately $43.5 million of the proceeds were used for the cost of the Capped Call and the Common Stock Forward, both of which are hedges related to the $100 million Convertible Senior Notes. As of December 31, 2019, the outstanding balance of the notes, net of related accretion and issuance costs, was $70.6 million. See Note 10, Convertible Senior Notes, for more details. On April 12, 2017, the Company issued to Tech Opportunities LLC (Tech Opps) warrants to acquire up to 5,250,750 shares of common stock at an exercise price of $2.69 per share. All of these warrants were exercised on October 15, 2019 for net proceeds of $14.1 million. See Note 11, Stockholders’ Equity, for additional information. Operating or Finance Leases The Company enters into sale/leaseback agreements with various financial institutions to facilitate the Company’s commercial transactions with key customers. The Company sells certain fuel cell systems and hydrogen infrastructure to the financial institutions and leases the equipment back to support certain customer locations and to fulfill its varied Power Purchase Agreements (PPAs). In connection with certain operating leases, the financial institutions require the Company to maintain cash balances in restricted accounts securing the Company’s finance obligations. Cash received from customers under the PPAs is used to make payments against the Company’s finance obligations. As the Company performs under these agreements, the required restricted cash balances are released, according to a set schedule. The total remaining lease payments to financial institutions under these agreements at December 31, 2019 was $227.2 million, $234.5 million of which were secured with restricted cash, security deposits and pledged service escrows. The Company has a master lease agreement with Wells Fargo Equipment Finance, Inc. (Wells Fargo MLA) to finance the Company’s commercial transactions with Wal-Mart Stores, Inc. (Walmart). The Wells Fargo MLA was entered into in 2017 and amended in 2018. Pursuant to the Wells Fargo MLA, the Company sells fuel cell systems and hydrogen infrastructure to Wells Fargo and then leases them back and operates them at Walmart sites under lease agreements with Walmart. The total remaining lease payments to Wells Fargo were $112.8 million at December 31, 2019. Transactions completed under the Wells Fargo MLA in 2019 and 2018 were accounted for as operating leases and therefore the sales of the fuel cell systems and hydrogen infrastructure were recognized as revenue for the year ended December 31, 2019 and 2018. Transactions completed under the Wells Fargo MLA in 2017 were accounted for as finance leases. The difference in lease classification is due to changes in financing terms and their bearing on lease assessment criteria. Also included in the remaining lease payments to Wells Fargo was a sale/leaseback transaction in 2015 that was accounted for as an operating lease. In connection with the Wells Fargo MLA, the Company has a customer guarantee for a majority of the transactions. The aforementioned Wells Fargo MLA transactions required a letter of credit for the unguaranteed portion totaling $30.7 million. Additionally, during the third quarter of 2019, the Company entered into master lease agreements with both Key Equipment Finance (KeyBank) and SunTrust Equipment Finance & Lease Corp. (SunTrust), to finance commercial transactions with Walmart. The transactions with KeyBank and SunTrust required cash collateral for the unguaranteed portions totaling $15.9 million. Similar to the aforementioned Wells Fargo MLA, the Company has a customer guarantee for the majority of the transactions. During the year ended December 31, 2019, the Company entered into additional, similar master lease agreements with Wells Fargo, Crestmark Equipment Finance (Crestmark), First American Bancorp, Inc. (First American), 36 th Street Capital Partners, LLC (36 th Street) and Fifth Third Bank, National Association (Fifth Third) to finance subscription programs with other customers. The total remaining lease payments to these financial institutions were $93.2 million at December 31, 2019. The majority of the lease payments are secured by cash collateral and letters of credit backed by restricted cash. Long-Term Debt In March 2019, the Company entered into a loan and security agreement with Generate Lending, LLC (Generate Capital)

Summary of Significant Accounti

Summary of Significant Accounting Policies	12 Months Ended
	Dec. 31, 2019
Summary of Significant Accounting Policies
Summary of Significant Accounting Policies	2. 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 The Company is a lessee in noncancelable (1) operating leases, primarily related to sale/leaseback transactions with financial institutions for deployment of the Company’s products at certain customer sites, and (2) finance leases, also primarily related to sale/leaseback transactions with financial institutions for similar commercial purposes. The Company accounts for leases in accordance with Accounting Standards Codification (ASC) Topic 842, Leases (ASC Topic 842), as amended, which was adopted in 2018 (see Recently Adopted Accounting Standards). The Company determines if an arrangement is or contains a lease at contract inception. The Company recognizes a right of use (ROU) asset and a lease liability (i.e. finance obligation) 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. · 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 the exercise price of a Company option to purchase the underlying asset if the Company is reasonably certain to exercise the option. The ROU 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 ROU 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 ROU 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 ROU asset is amortized over the useful life of the underlying asset. Amortization of the ROU asset is recognized and presented separately from interest expense on the lease liability. The Company’s leases do not contain variable lease payments. ROU 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 , to determine whether an ROU asset is impaired, and if so, the amount of the impairment loss to recognize. No impairment losses have been recognized to date. The Company monitors for events or changes in circumstances that require a reassessment of one 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 ROU asset. Operating and finance lease ROU assets are presented within leased property, net on the consolidated balance sheets. The current portion of operating and finance lease liabilities is included in finance obligations within current liabilities and the long-term portion is presented in finance obligations within noncurrent liabilities on the consolidated balance sheets. The Company has elected not to recognize ROU assets and lease liabilities for short-term leases that have a lease term of 12 months or less. The Company has elected to apply the short-term lease recognition and measurement exemption for other classes of leased assets. 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 or provided to customers under a Power Purchase Agreement (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. Only a limited number of fuel cell units are under standard warranty. 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 control over a product or service to a customer. The Company accounts for each distinct performance obligation within its arrangements as a distinct unit of accounting if the items under the performance obligation have value to the customer on a standalone basis. The Company considers a performance obligation to be distinct and have a standalone value 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. 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. Nature of goods and services The following is a description of principal activities from which the Company generates its revenue. (i) 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 considers comparable list prices, as well as historical average pricing approaches to determine standalone selling prices for GenDrive fuel cells. The Company uses 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 continual 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. 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 on 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 based on the Company’s efforts 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 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. In substantially all of its commercial transactions, the Company sells extended maintenance contracts that generally provide for a five to ten year service period from the date of product installation. Services include monitoring, technical support, maintenance and services that provide for 97% to 98% uptime of the fleet. These services are accounted for as a separate performance obligation, and accordingly, revenue generated from these transactions, subject to the proportional allocation of transaction price, is deferred and recognized in income over the term of the contract, generally on a straight-line basis. Additionally, the Company may enter into annual service and extended maintenance contracts that are billed monthly. Revenue generated from these transactions is recognized in income on a straight-line basis over the term of the contract. Costs are recognized as incurred over the term of the contract. Sales of spare parts are included within service revenue on the consolidated statements of operations. When costs are projected to exceed revenues over the life of the extended maintenance contract, an accrual for loss contracts is recorded. Costs are estimated based upon historical experience and consider the estimated impact of the Company’s cost reduction initiatives. The actual results may differ from these estimates. Upon expiration of the extended maintenance contracts, customers either choose to extend the contract 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 the Company’s GenKey solution. When fuel cell systems and related infrastructure are provided to customers through a PPA, revenues associated with these agreements are treated as rental income and recognized on a straight-line basis over the life of the agreements. In conjunction with entering into a PPA with a customer, the Company may enter into sale/leaseback transactions with third-party financial institutions, whereby the fuel cells, a majority of the related infrastructure and, in some cases, service are sold to the third-party financial institution and leased back to the Company through either an operating or finance lease. Certain of the Company’s sale/leaseback transactions with third-party financial institutions are required to be accounted for as finance leases. As a result, no upfront revenue was recognized at the closing of these transactions and a finance obligation for each lease was established. The fuel cell systems and related infrastructure that are provided to customers through these PPAs are considered leased property on the consolidated balance sheets. Costs to service the leased property, depreciation of the leased property, and other related costs are considered cost of PPA revenue on the consolidated statements of operations. Interest cost associated with finance leases is presented within interest and other expense, net on the consolidated statements of operations. The Company also has sale/leaseback transactions with financial institutions, which were required to be accounted for as an operating lease. The Company has rental expense associated with these sale/leaseback agreements with financial institutions. Rental expense is recognized on a straight-line basis over the life of the agreements and is characterized as cost of PPA revenue on the consolidated statements of operations. The Company adopted ASC Topic 842, effective January 1, 2018. As part of the adoption, the Company elected the practical expedient to not separate lease and non-lease components (i.e., maintenance services) within its rental income related to all PPA-related assets. To recognize revenue, the Company, as lessee, is required to determine whether each sale/leaseback arrangement meets operating lease criteria. As part of the assessment of these criteria, the Company estimates certain key inputs to the associated calculations such as: 1) discount rate it uses to discount the unpaid lease payments to present value and 2) useful life of the underlying asset(s): · 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 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. · 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 ensure that 75% of the estimated useful life of the assets is not exceeded which allows the Company to meet the operating lease criteria. (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 Company purchases hydrogen fuel from suppliers in certain cases (and produces hydrogen onsite) and sells to its customers upon delivery. 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 over 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, 2019 and 2018, 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. Derivative Liabilities Registered common stock warrants that require the issuance of registered shares upon exercise and do not sufficiently preclude an implied right to cash settlement are accounted for as derivative liabilities. We currently classify these derivative warrant liabilities on the consolidated balance sheet as a long-term liability, which are revalued at each balance sheet date subsequent to the initial issuance, using the Black-Scholes pricing model. This pricing model, which is based, in part, upon unobservable inputs for which there is little or no market data, requires the Company to develop its own assumptions. Changes in the fair value of the warrants are reflected in the consolidated statements of operations as change in fair value of common stock warrant liability. 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 both December 31, 2019, and 2018, the allowance for doubtful accounts was $249 thousand. 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 risks and rewards of ownership have transferred. 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. Leased Property Leased property primarily consists of the cost of assets deployed related to finance leases. Depreciation expense is recorded on a straight-line basis over the shorter of the lease term or the estimated useful life of the asset, generally six to seven years, and is included in cost of revenue for PPAs in the consolidated statements of operations. Impairment of Long-Lived Assets Long-lived assets, such as property, plant, and equipment, leased property and purchased intangibles subject to amortization, are reviewed for potential impairment whenever events or changes in circumstances indicate that the carrying amount of an asset or asset group may not be recoverable. Recoverability of assets to be held and used is measured by a comparison of the carrying amount of an asset or asset group to estimated undiscounted future cash flows expected to be generated by the asset or asset group. If the carrying amount of an asset or asset group exceeds its estimated undiscounted future cash flows, an impairment charge is recognized by the amount by which the carrying amount of the asset or asset group exceeds the fair value of the asset or asset group. Fair value is determined through various valuation techniques, including discounted cash flow models, quoted market values and third-party independent appraisals, as considered necessary. Assets to be disposed of and considered held for sale would be separately presented in the consolidated balance sheet and reported at the lower of the carrying amount or fair value less costs to sell, and are no longer depreciated. The assets and liabilities of a disposal group classified as held for sale would be presented separately in the appropriate asset and liability sections of the consolidated balance sheet. Goodwill 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 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 prior to performing the two-step goodwill impairment test. If this is the case, the two-step 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 two-step goodwill impairment test is not required. The Company performs an impairment review of goodwill 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, 2019, 2018, and 2017, 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. Intangible Assets Intangible assets consist of acquired technology, customer relationships and trademarks, and are amortized using a straight-line method over their useful lives of 5 - 10 years. Additionally, the intangible assets are reviewed for impairment when certain triggering events occur. Product Warranty Reserve Aside from when included in the sale of an extended maintenance contract, the Company provides a one to two year standard product warranty to customers from date of installation of GenDrive units, and the GenSure sales generally include a two year standard product warranty. We currently estimate the costs of satisfying warranty claims based on an analysis of past experience and provide for future claims in the period the revenue is recognized. Factors that affect our warranty liability include the number of installed units, estimated material costs, estimated travel, and labor costs. The warranty reserve is included within the other current liabilities on the consolidated balance sheet. Equity Instruments Common stock warrants that meet certain applicable requirements of ASC Subtopic 815-40, Derivatives and Hedging – Contracts in Entity’s Own Equity , and other related guidance, including the ability of the Company to settle the warrants without the issuance of registered shares or the absence of rights of the grantee to require cash settlement, are accounted for as equity instruments. The Company classifies these equity instruments within additional paid-in capital on the consolidated balance sheets. Common stock warrants accounted for as equity instruments represent the warrants issued to Amazon and Walmart as discussed in Note 13, Warrant Transaction Agreements. The Company early-adopted FASB Accounting Standards Update 2019-08, Compensation – Stock Compensation (Topic 718) and Revenue from Contracts with Customers (Topic 606) (ASU 2019-08), which requires entities to measure and classify share-based payment awards granted to a customer by applying the guidance under Topic 718. The Company adopted ASU 2019-08 as of January 1, 2019. As a result, the amount recorded as a reduction of revenue will be measured based on the grant-date fair value of the warrants. Previously, this amount was measured based on vesting date fair value with estimates of fair value determined at each financial reporting date for unvested warrant shares considered to be probable of vesting. Except for the third tranche, all existing unvested warrants are using a measurement date January 1, 2019, the adoption date, in accordance with the transition requirements of ASU 2019-08. For the third tranche, the exercise price will be determined once the second tranche vests. The measurement date will be determined at that time. As a result of the adoption of ASU 2019-08 in the fourth quarter of 2019, applied with an effective date of January 1, 2019, the Company’s unaudited condensed consolidated financial information for the quarterly periods ended March 31, 2019, June 30, 2019, and September 30, 2019, has been revised. Amounts related to prior years were not impacted by the adoption of ASU 2019-08. The following table summarizes the impact of ASU 2019-08 adoption, as a reduction of revenue, by quarter on the consolidated statement of operations (in thousands): Three months ended December 31, September 30, June 30, March 31, 2019 2019 2019 2019 Total Warrant expense, pre adoption $ (2,807) $ (4,583) $ (1,483) $ (4,179) $ (13,052) Adjustment — 3,087 466 2,986 6,539 Warrant expense, post adoption (2,807) (1,496) (1,017) (1,193) (6,513) The Company uses the Black-Scholes pricing model, which is based, in part, upon unobservable inputs for which there is little or no market data, requiring the Company to develop its own assumptions. The Company estimates the fair value of unvested warrant shares, considered to be probable of vesting. Based on this estimated fair value, the Company determines the amount of warrant expense, which is recorded as a reduction of revenue on the consolidated statement of operations. In order to calculate warrant expense, the Company is required to make certain assumptions of key inputs to the Black-Scholes valuation model such as volatility and risk-free interest rate. 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 . Dividends on the redeemable preferred stock are accounted for as an increase in the net loss attributable to common stockholders. 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 . The Company recognizes in its consolidated financial statements the impact of a tax position only if that position is more likely than not to be sustained on audit, based on the technical merits of the position. 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 Costs related to research and development activities by the Company are expensed as incurred. Stock-Based Compensation The Company maintains employee stock-based compensation plans, which are described more fully in Note 15, 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, 2019, 2018 and 2017 since the Company remains in a net operating loss (NOL) position. Convertible Senior Notes $100 In March 2018, the Company issued $100.0 million in aggregate principal amount of 5.5% Convertible Senior Notes due on March 15, 2023. The Company accounts for the $100 $40 In September 2019, the Company issued The Company accounts for the issued $40 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 are made, whenever necessary, to prior period financial statements to conform to the current period presentation. 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 bei

Earnings Per Share

Earnings Per Share	12 Months Ended
	Dec. 31, 2019
Earnings Per Share
Earnings Per Share	3. Earnings Per Share 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 2017 Numerator: Net loss attributable to common stockholders $ (85,517) $ (78,167) $ (130,178) Denominator: Weighted average number of common stock outstanding 237,152,780 218,882,337 216,343,985 The dilutive potential shares common stock are summarized as follows: At December 31, 2019 2018 2017 Stock options outstanding (1) 23,013,590 21,957,150 19,872,029 Restricted stock outstanding (2) 4,608,560 2,347,347 234,744 Common stock warrants (3) 110,573,392 115,824,142 115,824,242 Preferred stock (4) 2,998,527 17,933,591 2,782,075 Convertible Senior Notes (5) 59,133,896 43,630,020 - Number of dilutive potential shares of common stock 200,327,965 201,692,250 138,713,090 (1) During the years ended December 31, 2019, 2018, and 2017, the Company granted 3,221,892, 2,679,667, and 5,485,863 stock options, respectively. (2) During the years ended December 31, 2019, 2018, and 2017, the Company granted 3,201,892, 2,367,347, and 234,744 shares of restricted stock, respectively. (3) In April 2017, the Company issued 5,250,750 warrants with an exercise price of $2.69 per warrant, as described in Note 11, Stockholders’ Equity. Of these warrants issued in April 2017, all have been exercised as of December 31, 2019. In April 2017, the Company issued warrants 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 13, Warrant Transaction Agreements. Of these warrants issued, none have been exercised as of December 31, 2019. In July 2017, the Company issued warrants 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 13, Warrant Transaction Agreements. Of these warrants issued, none have been exercised as of December 31, 2019. (4) The preferred stock amount represents the dilutive potential shares of common stock of the Series C, D and E redeemable convertible preferred stock, based on the conversion price of the preferred stock as of December 31, 2019, 2018 and 2017, respectively. Of the 10,431 Series C redeemable preferred stock issued on May 16, 2013, 7,811 had been converted to common stock through December 31, 2017, with the remainder still outstanding. Of the 18,500 Series D redeemable convertible preferred stock issued on December 22, 2016, 3,700 shares have been redeemed and the remaining 14,800 have been converted to common stock during the year ended December 31, 2017. On November 1, 2018, the Company issued 35,000 shares of Series E redeemable convertible preferred stock. As of December 31, 2019, 30,462 of the Series E Preferred Stock had been converted to common stock and 4,038 were redeemed for cash. The remainder of 500 were converted in January 2020. (5) In March 2018, the Company issued $100.0 million in aggregate principal amount of 5.5% Convertible Senior Notes. In September 2019, the Company issued a $40.0 million in aggregate principal amount of 7.5% Convertible Senior Note. See Note 10, Convertible Senior Notes.

Inventory

Inventory	12 Months Ended
	Dec. 31, 2019
Inventory
Inventory	4. Inventory Inventory as of December 31, 2019 and 2018 consists of the following (in thousands): December 31, 2019 December 31, 2018 Raw materials and supplies - production locations $ 48,011 $ 32,941 Raw materials and supplies - customer locations 9,241 6,755 Work-in-process 12,529 5,589 Finished goods 2,610 2,625 Inventory $ 72,391 $ 47,910

Property, Plant and Equipment

Property, Plant and Equipment	12 Months Ended
	Dec. 31, 2019
Property, Plant and Equipment
Property, Plant and Equipment	5. Property, Plant and Equipment Property, plant and equipment at December 31, 2019 and 2018 consists of the following (in thousands): December 31, December 31, 2019 2018 Leasehold improvements $ 862 $ 214 Software, machinery and equipment 31,514 27,058 Property, plant, and equipment 32,376 27,272 Less: accumulated depreciation (17,417) (14,403) Property, plant, and equipment, net $ 14,959 $ 12,869 Depreciation expense related to property, plant and equipment was $3.6 million, $2.6 million, and $1.9 million for the years ended December 31, 2019, 2018 and 2017, respectively. Upon the adoption of ASC 842, the Company reclassified property and equipment, subject to a finance lease, to right of use assets. See Note 18, Commitments and Contingencies – Finance Leases as Lessee.

Leased Property

Leased Property	12 Months Ended
	Dec. 31, 2019
Leased Property
Leased Property	6. Leased Property Leased property at December 31, 2019 and 2018 consists of the following (in thousands): December 31, December 31, 2019 2018 Right of use assets - operating $ 198,068 $ 76,747 Right of use assets - finance 41,475 39,905 Capitalized costs of lessor assets 41,465 41,040 Less: accumulated depreciation (36,268) (10,941) Leased property, net $ 244,740 $ 146,751 Capitalized costs of lessor assets associated with finance leases have been reclassified to right of use assets upon the adoption of ASC 842. Depreciation expense related to leased property was $8.4 million, $8.4 million, and $7.3 million the years ended December 31, 2019, 2018 and 2017, respectively.

Intangible Assets

Intangible Assets	12 Months Ended
	Dec. 31, 2019
Intangible Assets
Intangible Assets	7. Intangible Assets 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 10 years $ 8,244 $ (2,815) $ 5,429 Customer relationships 10 years 260 (150) 110 Trademark 5 years 60 (60) — $ 8,564 $ (3,025) $ 5,539 The gross carrying amount and accumulated amortization of the Company’s acquired identifiable intangible assets as of December 31, 2018 are as follows (in thousands): Weighted Average Gross Carrying Accumulated Amortization Period Amount Amortization Total Acquired technology 9 years $ 5,926 $ (2,176) $ 3,750 Customer relationships 10 years 260 (123) 137 Trademark 5 years 60 (57) 3 $ 6,246 $ (2,356) $ 3,890 The change in the gross carrying amount of the acquired technology from December 31, 2018 to December 31, 2019 As part of the agreement to acquire the intellectual property from AFC, the Company shall pay AFC milestone payments not to exceed $2.9 million in total, if certain milestones Amortization expense for acquired identifiable intangible assets for the years ended December 31, 2019 and 2018 was $0.7 million, $0.7 million, respectively. Estimated amortization expense for subsequent years is as follows (in thousands): 2020 801 2021 801 2022 801 2023 801 2024 and thereafter 2,335 Total $ 5,539

Accrued Expenses

Accrued Expenses	12 Months Ended
	Dec. 31, 2019
Accrued Expenses
Accrued Expenses	8. Accrued Expenses Accrued expenses at December 31, 2019 and 2018 consist of (in thousands): 2019 2018 Accrued payroll and compensation related costs $ 2,933 $ 2,150 Accrued accounts payable 7,254 1,790 Accrued sales and other taxes 905 1,478 Accrued interest 2,374 1,605 Accrued other 747 841 Total $ 14,213 $ 7,864

Long-Term Debt

Long-Term Debt	12 Months Ended
	Dec. 31, 2019
Long-Term Debt
Long-Term Debt	9. Long-Term Debt In March 2019, the Company, and its subsidiaries Emerging Power Inc. and Emergent Power Inc., entered Advances under the Term Loan Facility bear interest Interest and a portion of the principal amount is payable on a quarterly basis and the entire then outstanding principal balance of the Term Loan Facility, together with all accrued and unpaid interest, is due and payable on the maturity date of October 6, 2022. The Company may also be required to pay Generate Capital additional fees of up to $1.5 million if the Company is unable to provide $50.0 million of structured project financing arrangements with Generate Capital prior to December 31, 2021. All obligations under the Loan Agreement are unconditionally guaranteed by Emerging Power Inc. and Emergent Power Inc. 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. The Term Loan Facility requires the principal balance at the end of each of the following years may not exceed the following (in thousands): December 31, 2020 $ 86,159 December 31, 2021 59,373

Convertible Senior Notes

Convertible Senior Notes	12 Months Ended
	Dec. 31, 2019
Convertible Senior Notes
Convertible Senior Notes	10. $40 In September 2019, the Company issued a $40.0 million in aggregate principal amount of 7.5% Convertible Senior Note due on January 5, 2023 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 are no required principal payments prior to maturity of the note. Upon maturity of the note, the Company is required to repay 120% of $40.0 million, or $48.0 million. The note bears interest at 7.5% per annum, payable quarterly in arrears on January 5, April 5, July 5 and October 5 of each year beginning on October 5, 2019 and will mature on January 5, 2023 unless earlier converted or repurchased in accordance with its terms. The note is unsecured and does not contain any financial covenants or any restrictions on the payment of dividends, or the issuance or repurchase of common stock by the Company. The note has an initial conversion rate of 387.5969, which is subject to adjustment in certain events. The initial conversion rate is equivalent to an initial conversion price of approximately $2.58 per share of common stock. The holder of the note may convert at its option at any time until the close of business on the second scheduled trading day immediately prior to the maturity date for shares of the Company’s common stock, subject to certain limitations. In addition, the note will be automatically converted if (1) the daily volume-weighted average price per share of common stock exceeds 175% of the conversion price (as described above) on each of the 20 consecutive VWAP trading days (as defined in the note) beginning after the issue date of the note and (2) certain equity conditions (as defined in the note) are satisfied. Only if both criteria are met is the note automatically converted. Upon either the voluntary or automatic conversion of the note, the Company will deliver shares of common stock based on (1) the then-effective conversion rate and (2) the original principal amount of $40.0 million and not the maturity principal amount of $48.0 million. The note does not allow cash settlement (entirely or partially) upon conversion. As such, the Company uses the if-converted method for calculating any potential dilutive effect of the conversion option on diluted earnings per share. The Company concluded the conversion features did not require bifurcation. Specifically, while the Company determined that (i) the conversion features were not clearly and closely related to the host contracts, (ii) the note (i.e., hybrid instrument) is not remeasured at fair value under otherwise applicable GAAP with changes in fair value reported in earnings as they occur and (iii) the conversion features, if freestanding, would meet the definition of a derivative, the Company concluded such conversion features meet the equity scope exception, and therefore, the conversion features are not required to be bifurcated from the note. If the Company undergoes a fundamental change prior to the maturity date, subject to certain limitations, the holder may require the Company to repurchase for cash all or a portion of the note at a cash repurchase price equal to any accrued and unpaid interest on the note (or portion thereof), plus the greater of (1) 115% of the maturity principal amount of $48.0 million (or portion thereof) and (2) 110% of the product of (i) the conversion rate in effect as of the trading day immediately preceding the date of such fundamental change; (ii) the principal amount of the $40.0 million note to be repurchased divided by $1,000; and (iii) the average of the daily volume-weighted average price per share of the Company’s common stock over the five consecutive VWAP trading days immediately before the effective date of such fundamental change. In addition, with the consent of the holder of the note, subject to certain limitations, the Company may redeem all or any portion of the note, at the Company’s option, at a cash redemption price equal to any accrued and unpaid interest on the note (or portion thereof), plus the greater of (1) 105% of the maturity principal amount of $48.0 million (or portion thereof); and (2) 115% of the product of (i) the conversion rate in effect as of the trading day immediately preceding the related redemption date; (ii) the principal amount of the $40.0 million note to be redeemed divided by $1,000; and (iii) the arithmetic average of the daily volume-weighted average price per share of common stock over the five consecutive VWAP trading days immediately before the related redemption date. While the Company concluded the fundamental change redemption option represents an embedded derivative, the Company concluded the value of the embedded derivative to be immaterial given the likelihood of the occurrence of a fundamental change was deemed to be remote. As related to the call option, the Company concluded the call option was clearly and closely related to the host contract, and therefore, did not meet the definition of an embedded derivative. The Company concluded the total debt discount at issuance of the note equaled approximately $8.0 million. This debt discount was comprised of (1) the discount of $8.0 million attributed to the fact that upon maturity, the Company is required to repay 120% of $40.0 million, or $48.0 million and (2) debt issuance costs of $1.0 million. The debt discount was recorded as debt issuance cost (presented as contra debt in the consolidated balance sheet) and is being amortized to interest expense over the term of the note using the effective interest rate method. The Principal amounts: Principal at maturity $ 48,000 Unamortized debt discount (7,400) Unamortized debt issuance costs (969) Net carrying amount $ 39,631 As of December 31, 2019, the remaining life of the note was approximately 37 months. Based on the closing price of the Company’s common stock of $3.16 on December 31, 2019, the if-converted value of the notes was greater than the principal amount. At December 31, 2019, the estimated fair value of the note was approximately $53.5 million. The Company utilized a Monte Carlo simulation model to estimate the fair value of the convertible debt as of December 31, 2019. The simulation model is designed to capture the potential settlement features of the convertible debt, in conjunction with simulated changes in the Company's stock price over the term of the note, incorporating a volatility assumption of 70%. This is considered a Level 3 fair value measurement. $100 In March 2018, the Company issued $100.0 million in aggregate principal amount of 5.5% Convertible Senior Notes due on March 15, 2023 in a private placement to qualified institutional buyers pursuant to Rule 144A under the Securities Act. There are no required principal payments prior to maturity of the The total net proceeds from the Amount (in thousands) Principal amount $ 100,000 Less initial purchasers' discount (3,250) Less cost of related capped call and common stock forward (43,500) Less other issuance costs (894) Net proceeds $ 52,356 The Each $1,000 principal 1) during any calendar quarter (and only during such calendar quarter), if the last reported sale price of the Company’s common stock for 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 is greater than or equal to 130% of the conversion price on each applicable trading day; 2) during the five business day period after any five consecutive trading day period (the measurement period) in which the trading price (as defined in the indenture governing the notes ) per $1,000 principal amount of 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 for the notes on each such trading day; 3) if the Company calls any or all of the 4) upon the occurrence of certain specified corporate events, such as a beneficial owner acquiring more than 50% of the total voting power of the Company’s common stock, recapitalization of the Company, dissolution or liquidation of the Company, or the Company’s common stock ceases to be listed on an active market exchange. On or after September 15, 2022, holders may convert all or any portion of their Upon conversion of the The conversion rate will be subject to adjustment in some events but will not be adjusted for any accrued or unpaid interest. Holders who convert their The Company may not redeem the In accounting for the issuance of the We incurred transaction costs related to the issuance of the The Principal amounts: Principal $ 100,000 Unamortized debt discount (1) (27,818) Unamortized debt issuance costs (1) (1,567) Net carrying amount $ 70,615 Carrying amount of the equity component (2) $ 37,702 1) Included in the consolidated balance sheet within 2) Included in the consolidated balance sheet within additional paid-in capital, net of $1.7 million in equity issuance costs and associated income tax benefit of $9.2 million. As of December 31, 2019 Based on the closing price of the Company’s common stock of $3.16 on December 31, 2019, the if-converted value of the notes was greater than the principal amount. At December 31, 2019, the estimated fair value of the notes was approximately $135.3 million. The Company utilized data from market activity for this instrument near December 31, 2019 to determine the fair value of this instrument. This is considered a Level 2 fair value measurement. Capped Call In conjunction with the issuance of the $100 million Convertible Senior Notes, the Company entered into capped call options, or Capped Call, on the Company’s common stock with certain counterparties at a price of $16.0 million. The net cost incurred in connection with the Capped Call has been recorded as a reduction to additional paid-in capital in the consolidated balance sheet. The Capped Call is generally expected to reduce or offset the potential dilution to the Company’s common stock upon any conversion of the $100 million Convertible Senior Notes and/or offset any cash payments the Company is required to make in excess of the principal amount of the converted 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 Capped Call transactions will initially be $3.82 per share, which represents a premium of 100% over the last 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 Capped Call. The Capped Call becomes exercisable if the conversion option is exercised. By entering into the Capped Call, the Company expects to reduce the potential dilution to its common stock (or, in the event the conversion is settled in cash, to provide a source of cash to settle a portion of its cash payment obligation) in the event that at the time of conversion its stock price exceeds the conversion price under the $100 million Convertible Senior Notes. Common Stock Forward In connection with the sale of the $100 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 sheet. The related shares were accounted for as a repurchase of common stock. The fair values of the Capped Call and Common Stock Forward are not remeasured each reporting period.

Stockholders' Equity

Stockholders' Equity	12 Months Ended
	Dec. 31, 2019
Stockholders' Equity
Stockholders' Equity	11. 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 $.01 per share. As of December 31, 2019 and 2018, there were no shares of Series A Junior Participating Cumulative Preferred Stock issued and outstanding. See Note 12, Redeemable Convertible Preferred Stock, for a description of the Company’s issued and outstanding Series C and E redeemable 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 December 2019, the Company sold 46 million shares of common stock at a public price of $2.75 per share for net proceeds of approximately $120.4 million. In September 2019, the Company issued a $40.0 million in aggregate principal amount of 7.5% convertible senior note due in 2023 ($40 million Convertible Senior Note). The Company’s total obligation, net of interest accretion, due to the holder is $48.0 million. The total net proceeds from this offering, after deducting costs of the issuance were $39.1 million. As of December 31, 2019, the outstanding balance of the note, net of related discount and issuance costs was $39.6 million. See Note 10, Convertible Senior Notes, for more details. In March 2019, the Company issued and sold in a registered direct offering an aggregate of 10 million shares of the Company’s common stock at a purchase price of $2.35 per share. The net proceeds to the Company were approximately $23.5 million. There were 303,378,515 and 219,157,998 shares of common stock outstanding as of December 31, 2019 and 2018, respectively. On December 22, 2016, the Company issued warrants to purchase 10,501,500 shares of common stock in connection with offerings of common stock and Series D Redeemable Preferred Stock at an exercise price of $1.50 per share. During 2017, additional 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 13, Warrant Transaction Agreements. At both December 31, 2019 and 2018, in connection with these agreements, warrants to acquire 26,188,434 shares of common stock, have vested and are therefore exercisable. These warrants are measured at fair value and are classified as equity instruments on the consolidated balance sheet. At Market Issuance Sales Agreement On April 3, 2017, the Company entered into an At Market Issuance Sales Agreement (the Sales Agreement) with FBR Capital Markets & Co. B. Riley FBR, , as sales agent (FBR), pursuant to which the Company may offer and sell, from time to time through FBR, shares of common stock par value $0.01 per share having an aggregate offering price of up to $75.0 million. Under the Sales Agreement, in no event shall the Company issue or sell through FBR such a number of shares that exceeds the number of shares or dollar amount of common stock registered. During the year ended December 31, 2019, the Company raised gross proceeds of $15.3

Redeemable Convertible Preferre

Redeemable Convertible Preferred Stock	12 Months Ended
	Dec. 31, 2019
Redeemable Convertible Preferred Stock
Redeemable Convertible Preferred Stock	12. Redeemable Convertible Preferred Stock Series E Preferred Stock In November 2018, the Company . During 2019, 4,038 shares were redeemed for cash of $4.0 million, and 30,462 shares were converted to 13.8 million shares of common stock. Each share of Series E Except for our Series C Preferred Stock, which shall rank senior to the Series E Holders of the Series E In the event of any voluntary or involuntary liquidation, dissolution or winding up of the Company or other deemed liquidation event, the holders of the Series E Series C Preferred Stock The Company had 2,620 shares of Series C In the event of any voluntary or involuntary liquidation, dissolution or winding up of the Company, or other deemed liquidation event, the holder of the Series C

Warrant Transaction Agreements

Warrant Transaction Agreements	12 Months Ended
	Dec. 31, 2019
Warrant Transaction Agreements
Warrant Transaction Agreements	13. 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, warrants 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 is linked to payments made by Amazon or its affiliates (directly or indirectly through third parties) pursuant to the existing commercial agreements. The majority of the Amazon Warrant Shares will 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 first tranche of 5,819,652 Amazon Warrant Shares vested upon the execution of the Amazon Transaction Agreement. Accordingly, $6.7 million, the fair value of the first tranche of Amazon Warrant Shares, was recognized as selling, general and administrative expense on the consolidated statements of operations during 2017. All future provision for common stock warrants will be recorded in revenue. The second tranche of 29,098,260 Amazon Warrant Shares will vest in four installments of 7,274,565 Amazon Warrant Shares each time Amazon 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 Amazon Warrant Shares will be $1.1893 per share. After Amazon has made payments to the Company totaling $200.0 million, the third tranche of 20,368,784 Amazon Warrant Shares will vest in eight installments of 2,546,098 Amazon Warrant Shares each time Amazon 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 Amazon 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 Amazon Warrant Shares. The Amazon Warrant Shares are exercisable through April 4, 2027. The Amazon Warrant Shares provide for net share settlement that, if elected by the holders, will reduce the number of shares issued upon exercise to reflect net settlement of the exercise price. The Amazon Warrant Shares provide 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. These warrants are classified as equity instruments. As of January 1, 2019, the Company’s adoption of ASU 2019-08 requires these share-based payment awards granted to a customer to be measured and classified by applying the guidance of ASC Topic 718. As a result, the amount recorded as a reduction in revenue is measured based on the grant-date fair value of the Amazon Warrant Shares, as opposed to the vesting date. The transition guidance of ASU 2019-08 specifies that equity instruments that are unvested and subject to its guidance as of the adoption date are to be measured at the adoption date fair value. See Equity Instruments in Note 2, Summary of Significant Accounting Policies for further information regarding the impact of adoption of ASU 2019-08. At both December 31, 2019 and 2018, 20,368,782 of the Amazon Warrant Shares had vested. The amount of provision for common stock warrants recorded as a reduction of revenue for the Amazon Warrant during the years ended December 31, 2019 and 2018 was $4.1 million and $9.8 million, respectively. 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 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 is linked to 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 Transaction Agreement. 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 will be recorded in revenue. The second tranche of 29,098,260 Walmart Warrant Shares will vest 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 will be $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 Shares are exercisable through July 20, 2027. The Walmart Warrant Shares provide for net share settlement that, if elected by the holders, will reduce the number of shares issued upon exercise to reflect net settlement of the exercise price. The Walmart Warrant Shares provide 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. These warrants are classified as equity instruments. As of January 1, 2019, the Company’s adoption of ASU 2019-08 requires these share-based payment awards granted to a customer to be measured and classified by applying the guidance of ASC Topic 718. As a result, the amount recorded as a reduction in revenue is measured based on the grant-date fair value of the Walmart Warrant Shares, as opposed to the vesting date. The transition guidance of ASU 2019-08 specifies that equity instruments that are unvested and subject to its guidance as of the adoption date are to be measured at the adoption date fair value. See Equity Instruments in Note 2, Summary of Significant Accounting Policies for further information regarding the impact of adoption of ASU 2019-08. At both December 31, 2019 and 2018, 5,819,652 of the Walmart Warrant Shares had vested. The amount of provision for common stock warrants recorded as a reduction of revenue for the Walmart Warrant during the years ended December 31, 2019 and 2018 was $2.4 million and $0.4 million, respectively.

Revenue

Revenue	12 Months Ended
	Dec. 31, 2019
Revenue
Revenue	14. Revenue Disaggregation of revenue The following table provides information about disaggregation of revenue (in thousands): Major products/services lines Year ended December 31, 2019 2018 2017 Sales of fuel cell systems $ 130,721 $ 75,146 $ 49,206 Sale of hydrogen installations and other infrastructure 19,163 32,146 13,425 Services performed on fuel cell systems and related infrastructure 25,217 22,002 16,202 Power Purchase Agreements 25,853 22,869 12,869 Fuel delivered to customers 29,099 22,469 8,167 Other 186 — 284 Net revenue $ 230,239 $ 174,632 $ 100,153 Contract balances The following table provides information about receivables, contract assets and contract liabilities from contracts with customers (in thousands): 2019 2018 Accounts receivable $ 25,448 $ 37,347 Contract assets 13,251 3,328 Contract liabilities 43,480 40,476 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). These amounts are included within deferred revenue on the consolidated balance sheet. Contract liabilities also include advance consideration received from customers prior to delivery of products. These amounts are included in other current 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, 2019 Transferred to receivables from contract assets recognized at the beginning of the period $ (1,252) Revenue recognized and not billed as of the end of the period 11,175 Net change in contract assets $ 9,923 Contract liabilities Year ended December 31, 2019 Revenue recognized that was included in the contract liability balance as of the beginning of the period $ (10,172) Increases due to cash received, net of amounts recognized as revenue during the period 13,175 Net change in contract liabilities $ 3,003 Estimated future revenue The following table includes estimated revenue 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 of services and PPAs are expected to be recognized as revenue over five to seven years) related to performance obligations that are unsatisfied (or partially unsatisfied) at the end of the reporting period, excluding provision for common stock warrants as it is not readily estimable as it depends on the valuation of the common stock warrants when revenue is recognized (in thousands): Year ended December 31, 2019 2018 Sales of fuel cell systems $ 73,491 $ 17,318 Sale of hydrogen installations and other infrastructure 72,862 9,141 Services performed on fuel cell systems and related infrastructure 87,020 73,381 Power Purchase Agreements 133,475 111,533 Other rental income 4,993 6,633 Total estimated future revenue $ 371,841 $ 218,006 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, 2019 and 2018 were $0.5 million and $0.2, respectively. Expense related to the amortization of capitalized contract costs was not significant for the year ended December 31, 2019.

Employee Benefit Plans

Employee Benefit Plans	12 Months Ended
	Dec. 31, 2019
Employee Benefit Plans
Employee Benefit Plans	15. 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, 2019, 2018, and 2017, the Company recorded expense of approximately $8.8 million, $7.4 million, and $9.0 million, respectively, in connection with the Third Amended and Restated 2011 Stock Option and Incentive Plan. At December 31, 2019, there were outstanding options to purchase approximately 23.0 million shares of Common Stock and 8.4 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 to three years in duration and expire ten years after issuance. Compensation cost associated with employee stock options represented approximately $6.0 million, $6.4 million, and $8.6 million of the total share-based payment expense recorded for the years ended December 31, 2019, 2018, and 2017, 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 3,221,892, 2,679,667and 5,485,863 options granted during the years ended December 31, 2019, 2018 and 2017, respectively, were as follows: 2019 2018 2017 Expected term of options (years) 6 6 6 Risk free interest rate 1.52% - 2.53% 2.81% - 2.88% 1.89% - 2.16% Volatility 69.32% - 87.94% 98.31% - 98.89% 99.24% - 102.16% There was no expected dividend yield for the employee stock options granted. The Company’s estimate of an expected option term was calculated in accordance with the simplified method for calculating the expected term assumption. 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, 2019 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, 2018 21,957,150 $ 2.51 7.1 $ 1,432 Granted 3,221,892 2.40 — — Exercised (1,151,307) 1.56 — — Forfeited (934,195) 3.50 — — Expired (79,950) 9.43 — — Options outstanding at December 31, 2019 23,013,590 $ 2.48 6.6 $ 22,277 Options exercisable at December 31, 2019 16,608,362 2.57 5.8 16,285 Options unvested at December 31, 2019 6,405,228 $ 2.22 8.9 $ 5,992 The weighted average grant-date fair value of options granted during the years ended December 31, 2019, 2018 and 2017 was $1.67, $1.55, and $1.67, respectively. As of December 31, 2019, there was approximately $8.1 million of unrecognized compensation cost related to stock option awards to be recognized over the next three years with all of this expected to vest. The total fair value of stock options that vested during the years ended December 31, 2019 and 2018 was approximately $6.1 million and $7.1 million, respectively. Restricted stock awards generally vest in equal installments over a period of one to three years. Restricted stock awards are valued based on the closing price of the Company’s common stock on the date of grant, and compensation cost is recorded on a straight-line basis over the share vesting period. The Company recorded expense associated with its restricted stock awards of approximately $2.8 million, $966 thousand, and $335 thousand, for the years ended December 31, 2019, 2018 and 2017, respectively. Additionally, for the years ended December 31, 2019, 2018 and 2017, there was $8.4 million, $3.9 million, and $208 thousand, 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, 2019 is as follows (in thousands except share amounts): Aggregate Intrinsic Shares Value Unvested restricted stock at December 31, 2018 2,347,347 $ — Granted 3,201,892 — Vested (920,679) — Forfeited (20,000) Unvested restricted stock at December 31, 2019 4,608,560 $ 14,563 401(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 841,539 shares and 633,827 shares of common stock to the Plug Power Inc. 401(k) Savings & Retirement Plan during 2019 and 2018, respectively. The Company’s expense for this plan was approximately $1.9 million, $1.8 million, and $1.6 million for years ended December 31, 2019, 2018 and 2017, 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 114,285, 107,389, and 148,077 shares of stock to non-employee directors as compensation for the years ended December 31, 2019, 2018, and 2017, 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 $243 thousand, $261 thousand, and $276 thousand for the years ended December 31, 2019, 2018, and 2017 respectively.

Fair Value Measurements

Fair Value Measurements	12 Months Ended
	Dec. 31, 2019
Fair Value Measurements
Fair Value Measurements	16. Fair Value Measurements As of December 31, 2019, the Company had no financial instruments measured at fair value on a recurring basis. The following table summarizes the financial instruments measured at fair value on a recurring basis in the consolidated balance sheets (in thousands) at December 31, 2018: Quoted Prices Significant Significant in Active Other Other Markets for Observable Unobservable Identical Items Inputs Inputs Total (Level 1) (Level 2) (Level 3) Common stock warrant liability $ 105 $ — $ — $ 105 Derivative Liabilities The Company’s common stock warrant liability represents the only asset or liability classified financial instrument measured at fair value on a recurring basis in the consolidated balance sheets. The fair value measurement is determined by using Level 3 inputs due to the lack of active and observable markets that can be used to price identical assets. Level 3 inputs are unobservable inputs and should be used to determine fair value only when observable inputs are not available. Unobservable inputs should be developed based on the best information available in the circumstances, which might include internally generated data and assumptions being used to price the asset or liability. Fair value of the common stock warrant liability is based on the Black-Scholes pricing model, which is based, in part, upon 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 liability-classified common stock warrants for the year ended December 31, 2018: Risk-free interest rate 1.64% - 2.66% Volatility 18.40% - 81.69% Expected average term 0.01 - 1.53 There was no expected dividend yield for the warrants granted. If factors change and different assumptions are used, the warrant liability and the change in estimated fair value could be materially different. Generally, as the market price of our common stock increases, the fair value of the warrants increases, and conversely, as the market price of our common stock decreases, the fair value of the warrants decrease. Also, a significant increase in the volatility of the market price of the Company’s common stock, in isolation, would result in significantly higher fair value measurements; and a significant decrease in volatility would result in significantly lower fair value measurements. The following table shows the activity in the common stock warrant liability (in thousands): 2019 2018 Beginning of period $ 105 $ 4,391 Change in fair value of common stock warrants (79) (4,286) Issuance of common stock warrants — — Exercise of common stock warrants (26) — End of period $ — $ 105 Equity Instruments The fair value measurement of the Company’s equity-classified common stock warrants further described in Note 13, Warrant Transaction Agreements, is determined by using Level 3 inputs due to the lack of active and observable markets that can be used to price identical instruments. The Company adopted ASU 2019-08, with retrospective adoption as of January 1, 2019. As a result, the fair value is measured based on the grant-date of warrants. Prior to that, the fair value of the warrants was measured as of the vesting date using the Monte Carlo pricing model, which is based, in part, upon 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 equity-classified common stock warrants for the years ended December 31, 2019 and 2018: Year ended January 1, 2019 December 31, 2018 Risk-free interest rate 2.60%-2.63% 2.60% - 3.02% Volatility 0.95 75.00% - 85.00% Expected average term 8.26-8.55 8.26 - 9.30 The Monte Carlo pricing models used in the determination of the fair value of the equity-classified warrants also incorporate assumptions involving future revenues associated with Amazon and Walmart, and related timing. The following table represents the fair value per warrant on the execution date of the transaction agreements and as of December 31, 2019 and 2018: Amazon Warrant Shares Walmart Warrant Shares Issuance date - first tranche $ 1.15 $ 1.88 As of vesting date - second tranche, first installment 2.16 — As of vesting date - second tranche, second installment 1.54 — As of December 2019 - second tranche 1.05 1.00 As of December 2018 - second tranche 0.98 0.92

Income Taxes

Income Taxes	12 Months Ended
	Dec. 31, 2019
Income Taxes
Income Taxes	17. Income Taxes The components of loss before income taxes and the income tax benefit for the years ended December 31, 2019, 2018 and 2017, by jurisdiction, are as follows (in thousands): 2019 2018 2017 U.S. Foreign Total U.S. Foreign Total U.S. Foreign Total Loss before income taxes $ (83,910) $ (1,555) $ (85,465) $ (85,925) $ (1,407) $ (87,332) $ (125,871) $ (1,209) $ (127,080) Income tax benefit — — — 9,217 — 9,217 — — — Net loss attributable to the Company $ (83,910) $ (1,555) $ (85,465) $ (76,708) $ (1,407) $ (78,115) $ (125,871) $ (1,209) $ (127,080) The significant components of deferred income tax expense (benefit) for the years ended December 31, 2019, 2018 and 2017, by jurisdiction, are as follows (in thousands): 2019 2018 2017 U.S. Foreign Total U.S. Foreign Total U.S. Foreign Total Deferred tax (benefit) expense $ (8,910) $ (426) $ (9,336) $ (10,182) $ 933 $ (9,249) $ 7,675 $ (531) $ 7,144 Net operating loss carryforward generated (7,254) (270) (7,524) (10,038) (665) (10,703) (19,117) (17) (19,134) Rate change impact on net operating loss carryforwards — — — — — — 23,609 — 23,609 Valuation allowance increase (decrease) 16,164 696 16,860 11,003 (268) 10,735 (12,167) 548 (11,619) Provision for income taxes $ — $ — $ — $ (9,217) $ — $ (9,217) $ — $ — $ — The Company’s effective income tax rate differed from the federal statutory rate as follows: 2019 2018 2017 U.S. Federal statutory tax rate (21.0) % (21.0) % (35.0) % Deferred state taxes 1.2 % (1.9) % (1.4) % Common stock warrant liability — % (1.0) % 4.2 % Provision to return and deferred tax asset adjustments — % — % 5.9 % Change in U.S. Federal statutory tax rate — % — % 33.5 % Other, net (0.5) % 0.4 % 2.0 % Change in valuation allowance 20.3 % 12.9 % (9.2) % 0.0 % (10.6) % 0.0 % 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, 2019 and 2018 are as follows (in thousands): U.S. Foreign Total 2019 2018 2019 2018 2019 2018 Intangible assets $ — $ — $ 1,197 $ 1,146 $ 1,197 $ 1,146 Deferred revenue 7,898 9,304 129 — 8,027 9,304 Interest expense 11,299 5,239 — — 11,299 5,239 Other reserves and accruals 699 592 — — 699 592 Tax credit carryforwards 2,590 1,865 1,253 1,200 3,843 3,065 Amortization of stock-based compensation 9,081 8,442 — — 9,081 8,442 Non-compensatory warrants 4,322 3,597 — — 4,322 3,597 Capitalized research & development expenditures 22,601 19,116 4,483 4,294 27,084 23,410 Right of use liability (operating leases) 39,237 16,715 — — 39,237 16,715 Net operating loss carryforwards 54,947 49,058 9,576 9,306 64,523 58,364 Total deferred tax asset 152,674 113,928 16,638 15,946 169,312 129,874 Valuation allowance (100,731) (84,567) (16,622) (15,926) (117,353) (100,493) Net deferred tax assets $ 51,943 $ 29,361 $ 16 $ 20 $ 51,959 $ 29,381 Intangible assets (15) (37) — — (15) (37) Convertible debt (7,718) (9,217) — — (7,718) (9,217) Right of use asset (operating leases) (40,298) (18,066) — — (40,298) (18,066) Other reserves and accruals — — (16) (20) (16) (20) Property, plant and equipment and right of use assets (3,912) (2,041) — — (3,912) (2,041) Deferred tax liability $ (51,943) $ (29,361) $ (16) $ (20) $ (51,959) $ (29,381) Net $ — $ — $ — $ — $ — $ — 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, 2019 and 2018 of approximately $117.4 million and $100.5 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 $ 7,254 $ 368 $ 7,622 Increase (decrease) in valuation allowance for current year net increase (decrease) in deferred tax assets other than net operating losses 11,845 (59) 11,786 Decrease in valuation allowance as a result of foreign currency fluctuation (2,935) — (2,935) Increase in valuation allowance due to change in tax rates — 387 387 Net increase in valuation allowance $ 16,164 $ 696 $ 16,860 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 Internal Revenue Code (IRC) Section 382, 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 IRC Section 382, the Company's federal and state net operating loss carryforwards could be subject to significant IRC Section 382 limitations. Based on studies of the changes in ownership of the Company, it has been determined that an IRC Section 382 ownership change occurred in 2013 that limited the amount of pre-change net operating losses that can be used in future years to $13.5 million. These net operating loss carryforwards will expire, if unused, at various dates from 2020 through 2033. Net operating losses of $223.1 million incurred after the most recent ownership change are not subject to IRC Section 382 and are available for use in future years. Accordingly, the Company's deferred tax assets include $236.6 million of U.S. net operating loss carryforwards. The net operating loss carryforwards available at December 31, 2019, include $27.7 million of net operating loss that was generated in 2019 and $42.2 million of net operating loss that was generated in 2018 that do not expire. The remainder, if unused, will expire at various dates from 2032 through 2037. Approximately $2.6 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, 2019. The remaining credit carryforwards will expire during the periods 2033 through 2039. At December 31, 2019, 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, 2019, 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, 2019, 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, 2019, the Company has unused French net operating loss carryforwards of approximately $17.9 million. The net operating loss may carryforward indefinitely or until the Company changes its activity. As of December 31, 2019, the Company has no un-repatriated foreign earnings or unrecognized tax benefits. The Company files income tax returns in the U.S. federal jurisdiction and various state and foreign jurisdictions. In the normal course of business, the Company is subject to examination by taxing authorities. Open tax years in the US range from 2016 and forward. Open tax years in the foreign jurisdictions range from 2009 to 2018. However, upon examination in subsequent years, if net operating losses carryforwards and tax credit carryforwards are utilized, the US and foreign jurisdictions can reduce net operating loss carryforwards and tax credit carryforwards utilized in the year being examined if they do not agree with the carryforward amount. As of December 31, 2019, the Company was not under audit in the U.S. or non-U.S. taxing jurisdictions. The Tax Cuts and Jobs Act, or the Act, was enacted on December 22, 2017. The Act makes broad and complex changes to the U.S. tax code including a reduction of the U.S. federal corporate tax rate from 35 percent to 21 percent effective for the 2018 tax year. Accordingly, federal deferred tax assets were adjusted in 2017 by $42.5 million to reflect the reduction in tax rates. Also, in 2017 the valuation allowance was reduced by $42.5 million resulting in no change to the net deferred tax asset. The deferred tax asset adjustments reduced the tax benefit of the current year losses by 33.5% as shown in the effective tax rate schedule. The valuation allowance rate impact includes an offsetting 33.5% for the tax rate reduction resulting in no change to the provision for income taxes.

Commitment and Contingencies

Commitment and Contingencies	12 Months Ended
	Dec. 31, 2019
Commitments and Contingencies
Commitments and Contingencies	18. Commitments and Contingencies Lessor Obligations As of December 31, 2019, the Company Future minimum lease payments under noncancelable operating leases (with initial or remaining lease terms in excess of one year) as of December 31, 2019 2020 $ 31,279 2021 30,316 2022 22,432 2023 18,346 2024 and thereafter 36,095 Total future minimum lease payments $ 138,468 Lessee Obligations As of December 31, 2019, the Company had operating and finance leases, as lessee, primarily associated with sale/leaseback transactions that are partially secured by restricted cash In prior periods, the Company entered into sale/leaseback transactions that were accounted for as finance leases and reported as part of finance obligations. The outstanding balance of finance obligations related to sale/leaseback transactions at December 31, 2019 and December 31, 2018 was $31.7 million and $81.9 million, respectively. The fair value of the finance obligation 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, 2019 The Company has a finance lease associated with its property and equipment in Latham, New York. Liabilities relating to this Future minimum lease payments under operating and finance leases (with initial or remaining lease terms in excess of one year) as of December 31, 2019 Other Total Operating Finance Leased Finance Leases Leases Property Obligations 2020 $ 44,849 $ 10,128 $ 414 $ 55,391 2021 44,919 9,276 407 54,602 2022 40,329 4,975 390 45,694 2023 35,738 3,150 366 39,254 2024 and thereafter 70,718 16,154 1,547 88,419 Total future minimum lease payments 236,553 43,683 3,124 283,360 Less imputed lease interest (65,226) (11,934) (887) (78,047) Sale of future services — 109,422 — 109,422 Total lease liabilities $ 171,327 $ 141,171 $ 2,237 $ 314,735 Rental expense for all operating leases was $30.6 million and $15.8 million for the years ended December 31, 2019 and 2018, respectively. The gross profit on sale/leaseback transactions for all operating leases was $26.2 million and $16.4 million for the years ended December 31, 2019 and 2018, respectively. Right of use assets obtained in exchange for new operating lease liabilities was $121.4 million and $46.3 million for the years ended December 31, 2019 and 2018, respectively. At December 31, 2019 and 2018, security deposits associated with sale/leaseback transactions were $6.0 million and $6.8 million, respectively, and Other information related to the operating leases are presented in the following table: Year ended Year ended December 31, 2019 December 31, 2018 Cash payments (in thousands) $ 29,317 $ 14,926 Weighted average remaining lease term (years) Weighted average discount rate 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). Finance lease costs were as follows (in thousands): Year ended Year ended December 31, 2019 December 31, 2018 Amortization of right of use asset $ 3,178 $ 7,549 Interest on finance obligations 4,863 6,908 Total finance lease cost $ 8,041 $ 14,457 Right of use assets obtained in exchange for new finance lease liabilities were $5.9 million and $2.2 million for the years ended December 31, 2019 and 2018, respectively. Other information related to the finance leases are presented in the following table: Year ended Year ended December 31, 2019 December 31, 2018 Cash payments (in thousands) $ 61,237 $ 33,715 Weighted average remaining lease term (years) Weighted average discount rate Restricted Cash In connection with certain of the above noted sale/leaseback agreements, cash of $125.1 million was required to be restricted as security as of December 31, 2019, which restricted cash will be released over the lease term. As of December 31, 2019, the Company also had certain letters of credit backed by security deposits totaling $103.4 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, 2019 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. The Company has established accruals for matters for which management considers a loss to be probable and reasonably estimable. It is the opinion of management that facts known at the present time do not indicate that such litigation, after taking into account insurance coverage and the aforementioned accruals, will have a material adverse impact on our results of operations, financial position, or cash flows. 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, 2019, two customers comprised approximately 63.4% of the total accounts receivable balance. At December 31, 2018, two customers comprised approximately 52.3% of the total accounts receivable balance. For the year ended December 31, 2019, 49.6% of total consolidated revenues were associated primarily with two customers. For the year ended December 31, 2018 66.7% of total consolidated revenues were associated primarily with two customers. 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.

Unaudited Quarterly Financial D

Unaudited Quarterly Financial Data	12 Months Ended
	Dec. 31, 2019
Quarterly Financial Information Disclosure
Unaudited Quarterly Financial Data	19. Unaudited Quarterly Financial Data (in thousands, except per share data) Quarters ended March 31, June 30, September 30, December 31, 2019 2019 2019 2019 Net revenue (1): Sales of fuel cell systems and related infrastructure $ 2,544 $ 38,696 $ 38,877 $ 69,767 Services performed on fuel cell systems and related infrastructure 6,343 5,341 6,205 7,328 Power Purchase Agreements 6,110 6,409 6,595 6,739 Fuel delivered to customers 6,582 7,089 7,649 7,779 Other - - 135 51 Net revenue 21,579 57,535 59,461 91,664 Gross (loss) profit (3,784) 10,619 8,349 12,782 Operating expenses 16,697 22,560 18,428 20,323 Operating loss (20,481) (11,941) (10,079) (7,541) Net loss attributable to common stockholders (31,004) (18,070) (18,155) (18,288) Loss per share: Basic and Diluted $ (0.14) $ (0.07) $ (0.08) $ (0.07) Quarters ended March 31, June 30, September 30, December 31, 2018 2018 2018 2018 Net revenue (1): Sales of fuel cell systems and related infrastructure $ 10,613 $ 18,820 $ 36,668 $ 41,191 Services performed on fuel cell systems and related infrastructure 5,483 5,691 5,156 5,672 Power Purchase Agreements 5,372 5,438 5,555 6,504 Fuel delivered to customers 4,950 5,280 5,786 6,453 Net revenue 26,418 35,229 53,165 59,820 Gross loss (3,984) (2,310) 4,409 4,507 Operating expenses 16,957 20,668 17,054 17,426 Operating loss (20,941) (22,978) (12,645) (12,919) Net loss attributable to common stockholders (19,848) (25,881) (15,578) (16,860) Loss per share: Basic and Diluted $ (0.09) $ (0.12) $ (0.07) $ (0.08) (1) The Company early-adopted Accounting Standards Update 2019-08, Compensation – Stock Compensation (Topic 718) and Revenue from Contracts with Customers (Topic 606) (ASU 2019-08), as of January 1, 2019 resulting in changes to previously reported 2019 interim financial information. See Note 2, Summary of Significant Accounting Policies, for details. Amounts related to 2018 were not impacted by the adoption of ASU 2019-08.

Summary of Significant Accoun_2

Summary of Significant Accounting Policies (Policies)	12 Months Ended
	Dec. 31, 2019
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 The Company is a lessee in noncancelable (1) operating leases, primarily related to sale/leaseback transactions with financial institutions for deployment of the Company’s products at certain customer sites, and (2) finance leases, also primarily related to sale/leaseback transactions with financial institutions for similar commercial purposes. The Company accounts for leases in accordance with Accounting Standards Codification (ASC) Topic 842, Leases (ASC Topic 842), as amended, which was adopted in 2018 (see Recently Adopted Accounting Standards). The Company determines if an arrangement is or contains a lease at contract inception. The Company recognizes a right of use (ROU) asset and a lease liability (i.e. finance obligation) 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. · 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 the exercise price of a Company option to purchase the underlying asset if the Company is reasonably certain to exercise the option. The ROU 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 ROU 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 ROU 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 ROU asset is amortized over the useful life of the underlying asset. Amortization of the ROU asset is recognized and presented separately from interest expense on the lease liability. The Company’s leases do not contain variable lease payments. ROU 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 , to determine whether an ROU asset is impaired, and if so, the amount of the impairment loss to recognize. No impairment losses have been recognized to date. The Company monitors for events or changes in circumstances that require a reassessment of one 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 ROU asset. Operating and finance lease ROU assets are presented within leased property, net on the consolidated balance sheets. The current portion of operating and finance lease liabilities is included in finance obligations within current liabilities and the long-term portion is presented in finance obligations within noncurrent liabilities on the consolidated balance sheets. The Company has elected not to recognize ROU assets and lease liabilities for short-term leases that have a lease term of 12 months or less. The Company has elected to apply the short-term lease recognition and measurement exemption for other classes of leased assets. 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 or provided to customers under a Power Purchase Agreement (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. Only a limited number of fuel cell units are under standard warranty. 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 control over a product or service to a customer. The Company accounts for each distinct performance obligation within its arrangements as a distinct unit of accounting if the items under the performance obligation have value to the customer on a standalone basis. The Company considers a performance obligation to be distinct and have a standalone value 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. 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. Nature of goods and services The following is a description of principal activities from which the Company generates its revenue. (i) 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 considers comparable list prices, as well as historical average pricing approaches to determine standalone selling prices for GenDrive fuel cells. The Company uses 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 continual 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. 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 on 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 based on the Company’s efforts 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 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. In substantially all of its commercial transactions, the Company sells extended maintenance contracts that generally provide for a five to ten year service period from the date of product installation. Services include monitoring, technical support, maintenance and services that provide for 97% to 98% uptime of the fleet. These services are accounted for as a separate performance obligation, and accordingly, revenue generated from these transactions, subject to the proportional allocation of transaction price, is deferred and recognized in income over the term of the contract, generally on a straight-line basis. Additionally, the Company may enter into annual service and extended maintenance contracts that are billed monthly. Revenue generated from these transactions is recognized in income on a straight-line basis over the term of the contract. Costs are recognized as incurred over the term of the contract. Sales of spare parts are included within service revenue on the consolidated statements of operations. When costs are projected to exceed revenues over the life of the extended maintenance contract, an accrual for loss contracts is recorded. Costs are estimated based upon historical experience and consider the estimated impact of the Company’s cost reduction initiatives. The actual results may differ from these estimates. Upon expiration of the extended maintenance contracts, customers either choose to extend the contract 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 the Company’s GenKey solution. When fuel cell systems and related infrastructure are provided to customers through a PPA, revenues associated with these agreements are treated as rental income and recognized on a straight-line basis over the life of the agreements. In conjunction with entering into a PPA with a customer, the Company may enter into sale/leaseback transactions with third-party financial institutions, whereby the fuel cells, a majority of the related infrastructure and, in some cases, service are sold to the third-party financial institution and leased back to the Company through either an operating or finance lease. Certain of the Company’s sale/leaseback transactions with third-party financial institutions are required to be accounted for as finance leases. As a result, no upfront revenue was recognized at the closing of these transactions and a finance obligation for each lease was established. The fuel cell systems and related infrastructure that are provided to customers through these PPAs are considered leased property on the consolidated balance sheets. Costs to service the leased property, depreciation of the leased property, and other related costs are considered cost of PPA revenue on the consolidated statements of operations. Interest cost associated with finance leases is presented within interest and other expense, net on the consolidated statements of operations. The Company also has sale/leaseback transactions with financial institutions, which were required to be accounted for as an operating lease. The Company has rental expense associated with these sale/leaseback agreements with financial institutions. Rental expense is recognized on a straight-line basis over the life of the agreements and is characterized as cost of PPA revenue on the consolidated statements of operations. The Company adopted ASC Topic 842, effective January 1, 2018. As part of the adoption, the Company elected the practical expedient to not separate lease and non-lease components (i.e., maintenance services) within its rental income related to all PPA-related assets. To recognize revenue, the Company, as lessee, is required to determine whether each sale/leaseback arrangement meets operating lease criteria. As part of the assessment of these criteria, the Company estimates certain key inputs to the associated calculations such as: 1) discount rate it uses to discount the unpaid lease payments to present value and 2) useful life of the underlying asset(s): · 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 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. · 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 ensure that 75% of the estimated useful life of the assets is not exceeded which allows the Company to meet the operating lease criteria. (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 Company purchases hydrogen fuel from suppliers in certain cases (and produces hydrogen onsite) and sells to its customers upon delivery. 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 over 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, 2019 and 2018, 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.
Derivative Liabilities	Derivative Liabilities Registered common stock warrants that require the issuance of registered shares upon exercise and do not sufficiently preclude an implied right to cash settlement are accounted for as derivative liabilities. We currently classify these derivative warrant liabilities on the consolidated balance sheet as a long-term liability, which are revalued at each balance sheet date subsequent to the initial issuance, using the Black-Scholes pricing model. This pricing model, which is based, in part, upon unobservable inputs for which there is little or no market data, requires the Company to develop its own assumptions. Changes in the fair value of the warrants are reflected in the consolidated statements of operations as change in fair value of common stock warrant liability.
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 both December 31, 2019, and 2018, the allowance for doubtful accounts was $249 thousand.
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 risks and rewards of ownership have transferred.
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.
Leased Property	Leased Property Leased property primarily consists of the cost of assets deployed related to finance leases. Depreciation expense is recorded on a straight-line basis over the shorter of the lease term or the estimated useful life of the asset, generally six to seven years, and is included in cost of revenue for PPAs in the consolidated statements of operations.
Impairment of Long-Lived Assets	Impairment of Long-Lived Assets Long-lived assets, such as property, plant, and equipment, leased property and purchased intangibles subject to amortization, are reviewed for potential impairment whenever events or changes in circumstances indicate that the carrying amount of an asset or asset group may not be recoverable. Recoverability of assets to be held and used is measured by a comparison of the carrying amount of an asset or asset group to estimated undiscounted future cash flows expected to be generated by the asset or asset group. If the carrying amount of an asset or asset group exceeds its estimated undiscounted future cash flows, an impairment charge is recognized by the amount by which the carrying amount of the asset or asset group exceeds the fair value of the asset or asset group. Fair value is determined through various valuation techniques, including discounted cash flow models, quoted market values and third-party independent appraisals, as considered necessary. Assets to be disposed of and considered held for sale would be separately presented in the consolidated balance sheet and reported at the lower of the carrying amount or fair value less costs to sell, and are no longer depreciated. The assets and liabilities of a disposal group classified as held for sale would be presented separately in the appropriate asset and liability sections of the consolidated balance sheet.
Goodwill	Goodwill 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 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 prior to performing the two-step goodwill impairment test. If this is the case, the two-step 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 two-step goodwill impairment test is not required. The Company performs an impairment review of goodwill 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, 2019, 2018, and 2017, 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.
Intangible Assets	Intangible Assets Intangible assets consist of acquired technology, customer relationships and trademarks, and are amortized using a straight-line method over their useful lives of 5 - 10 years. Additionally, the intangible assets are reviewed for impairment when certain triggering events occur.
Product Warranty Reserve	Product Warranty Reserve Aside from when included in the sale of an extended maintenance contract, the Company provides a one to two year standard product warranty to customers from date of installation of GenDrive units, and the GenSure sales generally include a two year standard product warranty. We currently estimate the costs of satisfying warranty claims based on an analysis of past experience and provide for future claims in the period the revenue is recognized. Factors that affect our warranty liability include the number of installed units, estimated material costs, estimated travel, and labor costs. The warranty reserve is included within the other current liabilities on the consolidated balance sheet.
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 , and other related guidance, including the ability of the Company to settle the warrants without the issuance of registered shares or the absence of rights of the grantee to require cash settlement, are accounted for as equity instruments. The Company classifies these equity instruments within additional paid-in capital on the consolidated balance sheets. Common stock warrants accounted for as equity instruments represent the warrants issued to Amazon and Walmart as discussed in Note 13, Warrant Transaction Agreements. The Company early-adopted FASB Accounting Standards Update 2019-08, Compensation – Stock Compensation (Topic 718) and Revenue from Contracts with Customers (Topic 606) (ASU 2019-08), which requires entities to measure and classify share-based payment awards granted to a customer by applying the guidance under Topic 718. The Company adopted ASU 2019-08 as of January 1, 2019. As a result, the amount recorded as a reduction of revenue will be measured based on the grant-date fair value of the warrants. Previously, this amount was measured based on vesting date fair value with estimates of fair value determined at each financial reporting date for unvested warrant shares considered to be probable of vesting. Except for the third tranche, all existing unvested warrants are using a measurement date January 1, 2019, the adoption date, in accordance with the transition requirements of ASU 2019-08. For the third tranche, the exercise price will be determined once the second tranche vests. The measurement date will be determined at that time. As a result of the adoption of ASU 2019-08 in the fourth quarter of 2019, applied with an effective date of January 1, 2019, the Company’s unaudited condensed consolidated financial information for the quarterly periods ended March 31, 2019, June 30, 2019, and September 30, 2019, has been revised. Amounts related to prior years were not impacted by the adoption of ASU 2019-08. The following table summarizes the impact of ASU 2019-08 adoption, as a reduction of revenue, by quarter on the consolidated statement of operations (in thousands): Three months ended December 31, September 30, June 30, March 31, 2019 2019 2019 2019 Total Warrant expense, pre adoption $ (2,807) $ (4,583) $ (1,483) $ (4,179) $ (13,052) Adjustment — 3,087 466 2,986 6,539 Warrant expense, post adoption (2,807) (1,496) (1,017) (1,193) (6,513) The Company uses the Black-Scholes pricing model, which is based, in part, upon unobservable inputs for which there is little or no market data, requiring the Company to develop its own assumptions. The Company estimates the fair value of unvested warrant shares, considered to be probable of vesting. Based on this estimated fair value, the Company determines the amount of warrant expense, which is recorded as a reduction of revenue on the consolidated statement of operations. In order to calculate warrant expense, the Company is required to make certain assumptions of key inputs to the Black-Scholes valuation model such as volatility and risk-free interest rate.
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 . Dividends on the redeemable preferred stock are accounted for as an increase in the net loss attributable to common stockholders.
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 . The Company recognizes in its consolidated financial statements the impact of a tax position only if that position is more likely than not to be sustained on audit, based on the technical merits of the position.
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.
Stock-Based Compensation	Stock-Based Compensation The Company maintains employee stock-based compensation plans, which are described more fully in Note 15, 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, 2019, 2018 and 2017 since the Company remains in a net operating loss (NOL) position.
Convertible Senior Notes	Convertible Senior Notes $100 In March 2018, the Company issued $100.0 million in aggregate principal amount of 5.5% Convertible Senior Notes due on March 15, 2023. The Company accounts for the $100 $40 In September 2019, the Company issued The Company accounts for the issued $40
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.
Recent Accounting Pronouncements	Recent Accounting Pronouncements Recently Adopted Accounting Pronouncements In November 2019, Accounting Standards Update (ASU) 2019-08 , Compensation—Stock Compensation (Topic 718) and , was issued to require entities to measure and classify share-based payment awards granted to a customer (warrants) by applying the guidance in Topic 718. The Company early adopted this update during the fourth quarter of 2019 with retrospective adoption as of January 1, 2019. As a result, the amount recorded as a reduction in revenue will be measured based on the grant-date fair value of the warrants, as opposed to the vesting date. Previous guidance required the Company to measure the warrant liability and related expense using guidance under ASC Topic 606. In June 2018, an accounting update was issued to simplify the accounting for nonemployee share-based payment transactions resulting from expanding the scope of ASC Topic 718, Compensation-Stock Compensation , to include share-based payment transactions for acquiring goods and services from nonemployees. An entity applies the requirements of ASC Topic 718 to nonemployee awards except for specific guidance on inputs to an option pricing model and the attribution of cost (that is, the period of time over which share-based payment awards vest and the pattern of cost recognition over that period). The amendments specify that ASC Topic 718 applies to all share-based payment transactions in which a grantor acquires goods or services to be used or consumed in a grantor’s own operations by issuing share-based payment awards. The amendments also clarify that ASC Topic 718 does not apply to share-based payments used to effectively provide (1) financing to the issuer or (2) awards granted in conjunction with selling goods or services to customers as part of a contract accounted for under ASC Topic 606, Revenue from Contracts with Customers . The Company adopted this update on January 1, 2019 and it did not have a material effect on the consolidated financial statements. In September 2018, the Company early adopted Accounting Standards Update 2016-02, Leases (Topic 842), as amended, effective January 1, 2018 and elected the available practical expedients. This adoption had a material impact on the Company’s consolidated statements of operations in that it allowed the Company to recognize gross profit on sale/leaseback transactions. The previous accounting standard only allowed revenue on sale/leaseback transactions to be recognized up to the amount of cost of goods sold and gross profit was deferred. Under ASC Topic 842, revenue can be recognized in full. Another impact from the adoption of ASC Topic 842 was the recognition of right of use assets and finance obligations for operating leases on the consolidated balance sheet, as well as expanded disclosures. The table below summarizes the impact of this initial adoption to the consolidated balance sheet as of January 1, 2018 (in thousands): Recognition of right of use asset $ 34,416 Decrease in accrued expenses 385 Recognition of finance obligation (34,161) Decrease in prepaid expenses and other assets (3,229) Decrease in leased property, net of accumulated depreciation (563) Increase in accumulated deficit 3,487 In addition, the consolidated statement of operations for the year ended December 31, 2018 was impacted by a decrease of depreciation expenses of $0.3 million. Recently Issued and Not Yet Adopted Accounting Pronouncements In May 2019, Accounting Standards Update (ASU) 2019-05, Financial Instruments – Credit Losses , was issued to provide an option to irrevocably elect the fair value option for certain financial assets previously measured at amortized cost basis. Adoption of this update is optional and within scope of Topic 326, Financial Instruments – Credit Losses, effective for fiscal years beginning after December 15, 2019. The Company has evaluated the adoption method and determined the impact of this standard to be immaterial to the consolidated financial statements. 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). This update is effective for fiscal years beginning after December 15, 2019. The Company has evaluated the adoption method and determined the impact of this standard to be immaterial to the consolidated financial statements. In August 2018, Accounting Standards Update (ASU) 2018-05, Intangibles – Goodwill and Other – Internal-Use Software (Subtopic 350-40) , was issued to help entities evaluate the accounting for fees paid by a customer in cloud computing arrangement (hosting arrangement) by providing guidance for determining when the arrangement includes a software license. The amendments in this update are effective for public companies beginning after December 15, 2019. Early adoption of the amendments in this update are permitted. The Company has evaluated the adoption method and determined the impact of this standard to be immaterial to the consolidated financial statements. In January 2017, Accounting Standards Update (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. This accounting update is effective for fiscal years beginning after December 15, 2019. The Company has evaluated the adoption method and determined the impact of this standard to be immaterial to the consolidated financial statements. In August 2016, Accounting Standards Update (ASU) 2016-15, Statement of Cash Flows (Topic 230)s: Classification of Certain Cash Receipts and Cash Payments , was issued to reduce the existing diversity in practice in how certain cash receipts and cash payments are presented and classified in the statement of cash flows. This accounting update is effective for fiscal years beginning after December 15, 2018, and interim periods within fiscal years beginning after December 15, 2019. Early adoption is permitted, including adoption in an interim period. The Company has evaluated the adoption method and determined the impact of this standard to be immaterial to the consolidated financial statements. In June 2016, Accounting Standards Update (ASU) 2016-13, Financial Instruments - Credit Losses (Topic 326): Measurement of Credit Losses on Financial Instruments , was issued. 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. This update is effective beginning after January 1, 2020. The Company has evaluated the adoption method and determined the impact of this standard to be immaterial to the consolidated financial statements.

Summary of Significant Accoun_3

Summary of Significant Accounting Policies (Tables)	12 Months Ended
	Dec. 31, 2019
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 provision for common stock warrants	The following table summarizes the impact of ASU 2019-08 adoption, as a reduction of revenue, by quarter on the consolidated statement of operations (in thousands): Three months ended December 31, September 30, June 30, March 31, 2019 2019 2019 2019 Total Warrant expense, pre adoption $ (2,807) $ (4,583) $ (1,483) $ (4,179) $ (13,052) Adjustment — 3,087 466 2,986 6,539 Warrant expense, post adoption (2,807) (1,496) (1,017) (1,193) (6,513)
Summary of impact due to adoption of new accounting pronouncements	The table below summarizes the impact of this initial adoption to the consolidated balance sheet as of January 1, 2018 (in thousands): Recognition of right of use asset $ 34,416 Decrease in accrued expenses 385 Recognition of finance obligation (34,161) Decrease in prepaid expenses and other assets (3,229) Decrease in leased property, net of accumulated depreciation (563) Increase in accumulated deficit 3,487

Earnings Per Share (Tables)

Earnings Per Share (Tables)	12 Months Ended
	Dec. 31, 2019
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 2017 Numerator: Net loss attributable to common stockholders $ (85,517) $ (78,167) $ (130,178) Denominator: Weighted average number of common stock outstanding 237,152,780 218,882,337 216,343,985
Schedule of potential dilutive common shares	At December 31, 2019 2018 2017 Stock options outstanding (1) 23,013,590 21,957,150 19,872,029 Restricted stock outstanding (2) 4,608,560 2,347,347 234,744 Common stock warrants (3) 110,573,392 115,824,142 115,824,242 Preferred stock (4) 2,998,527 17,933,591 2,782,075 Convertible Senior Notes (5) 59,133,896 43,630,020 - Number of dilutive potential shares of common stock 200,327,965 201,692,250 138,713,090 (1) During the years ended December 31, 2019, 2018, and 2017, the Company granted 3,221,892, 2,679,667, and 5,485,863 stock options, respectively. (2) During the years ended December 31, 2019, 2018, and 2017, the Company granted 3,201,892, 2,367,347, and 234,744 shares of restricted stock, respectively. (3) In April 2017, the Company issued 5,250,750 warrants with an exercise price of $2.69 per warrant, as described in Note 11, Stockholders’ Equity. Of these warrants issued in April 2017, all have been exercised as of December 31, 2019. In April 2017, the Company issued warrants 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 13, Warrant Transaction Agreements. Of these warrants issued, none have been exercised as of December 31, 2019. In July 2017, the Company issued warrants 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 13, Warrant Transaction Agreements. Of these warrants issued, none have been exercised as of December 31, 2019. (4) The preferred stock amount represents the dilutive potential shares of common stock of the Series C, D and E redeemable convertible preferred stock, based on the conversion price of the preferred stock as of December 31, 2019, 2018 and 2017, respectively. Of the 10,431 Series C redeemable preferred stock issued on May 16, 2013, 7,811 had been converted to common stock through December 31, 2017, with the remainder still outstanding. Of the 18,500 Series D redeemable convertible preferred stock issued on December 22, 2016, 3,700 shares have been redeemed and the remaining 14,800 have been converted to common stock during the year ended December 31, 2017. On November 1, 2018, the Company issued 35,000 shares of Series E redeemable convertible preferred stock. As of December 31, 2019, 30,462 of the Series E Preferred Stock had been converted to common stock and 4,038 were redeemed for cash. The remainder of 500 were converted in January 2020. (5) In March 2018, the Company issued $100.0 million in aggregate principal amount of 5.5% Convertible Senior Notes. In September 2019, the Company issued a $40.0 million in aggregate principal amount of 7.5% Convertible Senior Note. See Note 10, Convertible Senior Notes.

Inventory (Tables)

Inventory (Tables)	12 Months Ended
	Dec. 31, 2019
Inventory
Schedule of Inventory	Inventory as of December 31, 2019 and 2018 consists of the following (in thousands): December 31, 2019 December 31, 2018 Raw materials and supplies - production locations $ 48,011 $ 32,941 Raw materials and supplies - customer locations 9,241 6,755 Work-in-process 12,529 5,589 Finished goods 2,610 2,625 Inventory $ 72,391 $ 47,910

Property, Plant and Equipment (

Property, Plant and Equipment (Tables)	12 Months Ended
	Dec. 31, 2019
Property, Plant and Equipment
Schedule of Property plant and equipment	Property, plant and equipment at December 31, 2019 and 2018 consists of the following (in thousands): December 31, December 31, 2019 2018 Leasehold improvements $ 862 $ 214 Software, machinery and equipment 31,514 27,058 Property, plant, and equipment 32,376 27,272 Less: accumulated depreciation (17,417) (14,403) Property, plant, and equipment, net $ 14,959 $ 12,869

Leased Property (Tables)

Leased Property (Tables)	12 Months Ended
	Dec. 31, 2019
Leased Property
Schedule of Leased Property	Leased property at December 31, 2019 and 2018 consists of the following (in thousands): December 31, December 31, 2019 2018 Right of use assets - operating $ 198,068 $ 76,747 Right of use assets - finance 41,475 39,905 Capitalized costs of lessor assets 41,465 41,040 Less: accumulated depreciation (36,268) (10,941) Leased property, net $ 244,740 $ 146,751

Intangible Assets (Tables)

Intangible Assets (Tables)	12 Months Ended
	Dec. 31, 2019
Intangible Assets
Schedule of Intangible assets	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 10 years $ 8,244 $ (2,815) $ 5,429 Customer relationships 10 years 260 (150) 110 Trademark 5 years 60 (60) — $ 8,564 $ (3,025) $ 5,539 The gross carrying amount and accumulated amortization of the Company’s acquired identifiable intangible assets as of December 31, 2018 are as follows (in thousands): Weighted Average Gross Carrying Accumulated Amortization Period Amount Amortization Total Acquired technology 9 years $ 5,926 $ (2,176) $ 3,750 Customer relationships 10 years 260 (123) 137 Trademark 5 years 60 (57) 3 $ 6,246 $ (2,356) $ 3,890
Schedule of future amortization of intangible assets	Estimated amortization expense for subsequent years is as follows (in thousands): 2020 801 2021 801 2022 801 2023 801 2024 and thereafter 2,335 Total $ 5,539

Accrued Expenses (Tables)

Accrued Expenses (Tables)	12 Months Ended
	Dec. 31, 2019
Accrued Expenses
Schedule of Accrued Expenses	Accrued expenses at December 31, 2019 and 2018 consist of (in thousands): 2019 2018 Accrued payroll and compensation related costs $ 2,933 $ 2,150 Accrued accounts payable 7,254 1,790 Accrued sales and other taxes 905 1,478 Accrued interest 2,374 1,605 Accrued other 747 841 Total $ 14,213 $ 7,864

Long-Term Debt (Tables)

Long-Term Debt (Tables)	12 Months Ended
	Dec. 31, 2019
Long-Term Debt
Summary of principal payments of long term debt	The Term Loan Facility requires the principal balance at the end of each of the following years may not exceed the following (in thousands): December 31, 2020 $ 86,159 December 31, 2021 59,373

Convertible Senior Notes (Table

Convertible Senior Notes (Tables)	12 Months Ended
	Dec. 31, 2019
$40M Convertible Senior Note
Debt Instrument [Line Items]
Schedule of Convertible Senior Notes	The Principal amounts: Principal at maturity $ 48,000 Unamortized debt discount (7,400) Unamortized debt issuance costs (969) Net carrying amount $ 39,631
$100M Convertible Senior Notes
Debt Instrument [Line Items]
Schedule of net proceeds from the Convertible Senior Notes	Amount (in thousands) Principal amount $ 100,000 Less initial purchasers' discount (3,250) Less cost of related capped call and common stock forward (43,500) Less other issuance costs (894) Net proceeds $ 52,356
Schedule of Convertible Senior Notes	The Principal amounts: Principal $ 100,000 Unamortized debt discount (1) (27,818) Unamortized debt issuance costs (1) (1,567) Net carrying amount $ 70,615 Carrying amount of the equity component (2) $ 37,702 1) Included in the consolidated balance sheet within 2) Included in the consolidated balance sheet within additional paid-in capital, net of $1.7 million in equity issuance costs and associated income tax benefit of $9.2 million.

Revenue (Tables)

Revenue (Tables)	12 Months Ended
	Dec. 31, 2019
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 2017 Sales of fuel cell systems $ 130,721 $ 75,146 $ 49,206 Sale of hydrogen installations and other infrastructure 19,163 32,146 13,425 Services performed on fuel cell systems and related infrastructure 25,217 22,002 16,202 Power Purchase Agreements 25,853 22,869 12,869 Fuel delivered to customers 29,099 22,469 8,167 Other 186 — 284 Net revenue $ 230,239 $ 174,632 $ 100,153
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): 2019 2018 Accounts receivable $ 25,448 $ 37,347 Contract assets 13,251 3,328 Contract liabilities 43,480 40,476
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, 2019 Transferred to receivables from contract assets recognized at the beginning of the period $ (1,252) Revenue recognized and not billed as of the end of the period 11,175 Net change in contract assets $ 9,923 Contract liabilities Year ended December 31, 2019 Revenue recognized that was included in the contract liability balance as of the beginning of the period $ (10,172) Increases due to cash received, net of amounts recognized as revenue during the period 13,175 Net change in contract liabilities $ 3,003
Schedule of Estimated future revenue	The following table includes estimated revenue 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 of services and PPAs are expected to be recognized as revenue over five to seven years) related to performance obligations that are unsatisfied (or partially unsatisfied) at the end of the reporting period, excluding provision for common stock warrants as it is not readily estimable as it depends on the valuation of the common stock warrants when revenue is recognized (in thousands): Year ended December 31, 2019 2018 Sales of fuel cell systems $ 73,491 $ 17,318 Sale of hydrogen installations and other infrastructure 72,862 9,141 Services performed on fuel cell systems and related infrastructure 87,020 73,381 Power Purchase Agreements 133,475 111,533 Other rental income 4,993 6,633 Total estimated future revenue $ 371,841 $ 218,006

Employee Benefit Plans (Tables)

Employee Benefit Plans (Tables)	12 Months Ended
	Dec. 31, 2019
Employee Benefit Plans
Assumptions made for the purpose of estimating fair value	2019 2018 2017 Expected term of options (years) 6 6 6 Risk free interest rate 1.52% - 2.53% 2.81% - 2.88% 1.89% - 2.16% Volatility 69.32% - 87.94% 98.31% - 98.89% 99.24% - 102.16%
Schedule of Share-based Compensation, Stock Options, Activity	A summary of stock option activity for the year December 31, 2019 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, 2018 21,957,150 $ 2.51 7.1 $ 1,432 Granted 3,221,892 2.40 — — Exercised (1,151,307) 1.56 — — Forfeited (934,195) 3.50 — — Expired (79,950) 9.43 — — Options outstanding at December 31, 2019 23,013,590 $ 2.48 6.6 $ 22,277 Options exercisable at December 31, 2019 16,608,362 2.57 5.8 16,285 Options unvested at December 31, 2019 6,405,228 $ 2.22 8.9 $ 5,992
Nonvested Restricted Stock Shares Activity	A summary of restricted stock activity for the year ended December 31, 2019 is as follows (in thousands except share amounts): Aggregate Intrinsic Shares Value Unvested restricted stock at December 31, 2018 2,347,347 $ — Granted 3,201,892 — Vested (920,679) — Forfeited (20,000) Unvested restricted stock at December 31, 2019 4,608,560 $ 14,563

Fair Value Measurements (Tables

Fair Value Measurements (Tables)	12 Months Ended
	Dec. 31, 2019
Schedule of Fair Value, Assets and Liabilities Measured on Recurring Basis	The following table summarizes the financial instruments measured at fair value on a recurring basis in the consolidated balance sheets (in thousands) at December 31, 2018: Quoted Prices Significant Significant in Active Other Other Markets for Observable Unobservable Identical Items Inputs Inputs Total (Level 1) (Level 2) (Level 3) Common stock warrant liability $ 105 $ — $ — $ 105
Schedule of activity in the common stock warrant liability	The following table shows the activity in the common stock warrant liability (in thousands): 2019 2018 Beginning of period $ 105 $ 4,391 Change in fair value of common stock warrants (79) (4,286) Issuance of common stock warrants — — Exercise of common stock warrants (26) — End of period $ — $ 105
Assumptions used to calculate common stock warrants	The Company used the following assumptions for its liability-classified common stock warrants for the year ended December 31, 2018: Risk-free interest rate 1.64% - 2.66% Volatility 18.40% - 81.69% Expected average term 0.01 - 1.53
Schedule of fair value of warrants	Amazon Warrant Shares Walmart Warrant Shares Issuance date - first tranche $ 1.15 $ 1.88 As of vesting date - second tranche, first installment 2.16 — As of vesting date - second tranche, second installment 1.54 — As of December 2019 - second tranche 1.05 1.00 As of December 2018 - second tranche 0.98 0.92
Equity Instruments
Assumptions used to calculate common stock warrants	Year ended January 1, 2019 December 31, 2018 Risk-free interest rate 2.60%-2.63% 2.60% - 3.02% Volatility 0.95 75.00% - 85.00% Expected average term 8.26-8.55 8.26 - 9.30

Income Taxes (Tables)

Income Taxes (Tables)	12 Months Ended
	Dec. 31, 2019
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, 2019, 2018 and 2017, by jurisdiction, are as follows (in thousands): 2019 2018 2017 U.S. Foreign Total U.S. Foreign Total U.S. Foreign Total Loss before income taxes $ (83,910) $ (1,555) $ (85,465) $ (85,925) $ (1,407) $ (87,332) $ (125,871) $ (1,209) $ (127,080) Income tax benefit — — — 9,217 — 9,217 — — — Net loss attributable to the Company $ (83,910) $ (1,555) $ (85,465) $ (76,708) $ (1,407) $ (78,115) $ (125,871) $ (1,209) $ (127,080)
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, 2019, 2018 and 2017, by jurisdiction, are as follows (in thousands): 2019 2018 2017 U.S. Foreign Total U.S. Foreign Total U.S. Foreign Total Deferred tax (benefit) expense $ (8,910) $ (426) $ (9,336) $ (10,182) $ 933 $ (9,249) $ 7,675 $ (531) $ 7,144 Net operating loss carryforward generated (7,254) (270) (7,524) (10,038) (665) (10,703) (19,117) (17) (19,134) Rate change impact on net operating loss carryforwards — — — — — — 23,609 — 23,609 Valuation allowance increase (decrease) 16,164 696 16,860 11,003 (268) 10,735 (12,167) 548 (11,619) Provision for income taxes $ — $ — $ — $ (9,217) $ — $ (9,217) $ — $ — $ —
Schedule of Effective Income Tax Rate Reconciliation	The Company’s effective income tax rate differed from the federal statutory rate as follows: 2019 2018 2017 U.S. Federal statutory tax rate (21.0) % (21.0) % (35.0) % Deferred state taxes 1.2 % (1.9) % (1.4) % Common stock warrant liability — % (1.0) % 4.2 % Provision to return and deferred tax asset adjustments — % — % 5.9 % Change in U.S. Federal statutory tax rate — % — % 33.5 % Other, net (0.5) % 0.4 % 2.0 % Change in valuation allowance 20.3 % 12.9 % (9.2) % 0.0 % (10.6) % 0.0 %
Schedule of Deferred Tax Assets and Liabilities	Significant components of the Company’s deferred tax assets and liabilities as of December 31, 2019 and 2018 are as follows (in thousands): U.S. Foreign Total 2019 2018 2019 2018 2019 2018 Intangible assets $ — $ — $ 1,197 $ 1,146 $ 1,197 $ 1,146 Deferred revenue 7,898 9,304 129 — 8,027 9,304 Interest expense 11,299 5,239 — — 11,299 5,239 Other reserves and accruals 699 592 — — 699 592 Tax credit carryforwards 2,590 1,865 1,253 1,200 3,843 3,065 Amortization of stock-based compensation 9,081 8,442 — — 9,081 8,442 Non-compensatory warrants 4,322 3,597 — — 4,322 3,597 Capitalized research & development expenditures 22,601 19,116 4,483 4,294 27,084 23,410 Right of use liability (operating leases) 39,237 16,715 — — 39,237 16,715 Net operating loss carryforwards 54,947 49,058 9,576 9,306 64,523 58,364 Total deferred tax asset 152,674 113,928 16,638 15,946 169,312 129,874 Valuation allowance (100,731) (84,567) (16,622) (15,926) (117,353) (100,493) Net deferred tax assets $ 51,943 $ 29,361 $ 16 $ 20 $ 51,959 $ 29,381 Intangible assets (15) (37) — — (15) (37) Convertible debt (7,718) (9,217) — — (7,718) (9,217) Right of use asset (operating leases) (40,298) (18,066) — — (40,298) (18,066) Other reserves and accruals — — (16) (20) (16) (20) Property, plant and equipment and right of use assets (3,912) (2,041) — — (3,912) (2,041) Deferred tax liability $ (51,943) $ (29,361) $ (16) $ (20) $ (51,959) $ (29,381) Net $ — $ — $ — $ — $ — $ —
Schedule of Valuation Allowance	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 $ 7,254 $ 368 $ 7,622 Increase (decrease) in valuation allowance for current year net increase (decrease) in deferred tax assets other than net operating losses 11,845 (59) 11,786 Decrease in valuation allowance as a result of foreign currency fluctuation (2,935) — (2,935) Increase in valuation allowance due to change in tax rates — 387 387 Net increase in valuation allowance $ 16,164 $ 696 $ 16,860

Commitments and Contingencies (

Commitments and Contingencies (Tables)	12 Months Ended
	Dec. 31, 2019
Commitments and Contingencies
Schedule of future minimum lease payments under noncancelable operating leases - as lessor	Future minimum lease payments under noncancelable operating leases (with initial or remaining lease terms in excess of one year) as of December 31, 2019 2020 $ 31,279 2021 30,316 2022 22,432 2023 18,346 2024 and thereafter 36,095 Total future minimum lease payments $ 138,468
Schedule of future minimum lease payments under noncancelable operating leases - as lessee	Future minimum lease payments under operating and finance leases (with initial or remaining lease terms in excess of one year) as of December 31, 2019 Other Total Operating Finance Leased Finance Leases Leases Property Obligations 2020 $ 44,849 $ 10,128 $ 414 $ 55,391 2021 44,919 9,276 407 54,602 2022 40,329 4,975 390 45,694 2023 35,738 3,150 366 39,254 2024 and thereafter 70,718 16,154 1,547 88,419 Total future minimum lease payments 236,553 43,683 3,124 283,360 Less imputed lease interest (65,226) (11,934) (887) (78,047) Sale of future services — 109,422 — 109,422 Total lease liabilities $ 171,327 $ 141,171 $ 2,237 $ 314,735
Schedule of operating leases other information	Year ended Year ended December 31, 2019 December 31, 2018 Cash payments (in thousands) $ 29,317 $ 14,926 Weighted average remaining lease term (years) Weighted average discount rate
Schedule of finance lease cost	Finance lease costs were as follows (in thousands): Year ended Year ended December 31, 2019 December 31, 2018 Amortization of right of use asset $ 3,178 $ 7,549 Interest on finance obligations 4,863 6,908 Total finance lease cost $ 8,041 $ 14,457
Schedule of finance leases other information	Year ended Year ended December 31, 2019 December 31, 2018 Cash payments (in thousands) $ 61,237 $ 33,715 Weighted average remaining lease term (years) Weighted average discount rate

Unaudited Quarterly Financial_2

Unaudited Quarterly Financial Data (Tables)	12 Months Ended
	Dec. 31, 2019
Quarterly Financial Information Disclosure
Schedule of Quarterly Financial Information	Quarters ended March 31, June 30, September 30, December 31, 2019 2019 2019 2019 Net revenue (1): Sales of fuel cell systems and related infrastructure $ 2,544 $ 38,696 $ 38,877 $ 69,767 Services performed on fuel cell systems and related infrastructure 6,343 5,341 6,205 7,328 Power Purchase Agreements 6,110 6,409 6,595 6,739 Fuel delivered to customers 6,582 7,089 7,649 7,779 Other - - 135 51 Net revenue 21,579 57,535 59,461 91,664 Gross (loss) profit (3,784) 10,619 8,349 12,782 Operating expenses 16,697 22,560 18,428 20,323 Operating loss (20,481) (11,941) (10,079) (7,541) Net loss attributable to common stockholders (31,004) (18,070) (18,155) (18,288) Loss per share: Basic and Diluted $ (0.14) $ (0.07) $ (0.08) $ (0.07) Quarters ended March 31, June 30, September 30, December 31, 2018 2018 2018 2018 Net revenue (1): Sales of fuel cell systems and related infrastructure $ 10,613 $ 18,820 $ 36,668 $ 41,191 Services performed on fuel cell systems and related infrastructure 5,483 5,691 5,156 5,672 Power Purchase Agreements 5,372 5,438 5,555 6,504 Fuel delivered to customers 4,950 5,280 5,786 6,453 Net revenue 26,418 35,229 53,165 59,820 Gross loss (3,984) (2,310) 4,409 4,507 Operating expenses 16,957 20,668 17,054 17,426 Operating loss (20,941) (22,978) (12,645) (12,919) Net loss attributable to common stockholders (19,848) (25,881) (15,578) (16,860) Loss per share: Basic and Diluted $ (0.09) $ (0.12) $ (0.07) $ (0.08) (1) The Company early-adopted Accounting Standards Update 2019-08, Compensation – Stock Compensation (Topic 718) and Revenue from Contracts with Customers (Topic 606) (ASU 2019-08), as of January 1, 2019 resulting in changes to previously reported 2019 interim financial information. See Note 2, Summary of Significant Accounting Policies, for details. Amounts related to 2018 were not impacted by the adoption of ASU 2019-08. SIGNATURES Pursuant to the requirements of Section 13 or 15(d) of the Securities Exchange Act of 1934, the registrant has duly caused this report to be signed on its behalf by the undersigned, thereunto duly authorized. PLUG POWER INC. By: /s/ ANDREW MARSH Andrew Marsh President, Chief Executive Officer and Director Date: March 9, 2020

Nature of Operations (Details)

Nature of Operations (Details) - USD ($) $ / shares in Units, $ in Thousands	Dec. 02, 2019	Oct. 29, 2019	Oct. 15, 2019	Mar. 08, 2018	Apr. 12, 2017	Apr. 03, 2017	Jan. 31, 2020	Dec. 31, 2019	Nov. 30, 2019	Sep. 30, 2019	Apr. 30, 2019	Mar. 31, 2019	Nov. 30, 2018	Mar. 31, 2018	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Liquidity
Net loss attributable to common shareholders															$ 18,288	$ 18,155	$ 18,070	$ 31,004	$ 16,860	$ 15,578	$ 25,881	$ 19,848	$ 85,517	$ 78,167	$ 130,178
Accumulated deficit								$ 1,345,807							1,345,807				1,260,290				1,345,807	1,260,290
Net cash used in operating activities																							51,522	57,617	60,182
Net loss attributable to the Company																							(85,465)	(78,115)	(127,080)
Net outflows from fluctuations in working capital and other assets and liabilities																							7,100
Non-cash charges																							41,000
Cash and cash equivalents								139,496							139,496				38,602				139,496	38,602
Net working capital								162,500							162,500				$ 9,200				162,500	9,200
Net cash used in investing activities																							(14,244)	(19,572)	(44,363)
Net cash provided by financing activities																							325,060	119,344	71,616
Proceeds from public offerings, net of transaction costs												$ 23,500											158,428	7,195	22,992
Value of shares issued																							158,429	7,016	22,992
Proceeds from issuance of preferred stock and warrants, net of transaction costs																							14,089	30,934	17,636
Increase in cash flows from new finance obligations																							83,700
Proceeds from issuance of debt																							39,052	95,856
Principal payments on long-term debt																							24,827	16,190	12,292
Proceeds from borrowing of long-term debt, net of transaction costs																							119,186		20,147
Principal amount														$ 100,000								100,000
Obligation, net of interest accretion										$ 48,000						48,000
Purchase of capped call and common stock forward																								43,500
Remaining lease payments								227,200							227,200								227,200
Security on lease								234,500							234,500								234,500
Letter of credit								103,400							$ 103,400								103,400
Cash Collateral for Borrowed Securities										15,900						15,900
Repayments of finance obligations																							61,713	$ 31,264	18,632
Payments for redemption of preferred stock																							4,040		$ 3,700
Number of common stock sold												10,000,000
Share price (in dollars per share)												$ 2.35						$ 2.35
Number of preferred shares that had been converted to common stock															30,962
Proceeds from Stock Options Exercised																							1,200
Warrants issued in December 2016
Liquidity
Shares of common stock that can be purchased from warrants issued (in shares)					5,250,750
Per share price of shares of common stock					$ 2.69
Proceeds from exercise of warrants, net of transaction costs					$ 15,100
Proceeds from Stock Options Exercised			$ 14,100
Additional Master Lease Agreements
Liquidity
Remaining lease payments								93,200							$ 93,200								93,200
Secured term loan facility
Liquidity
Proceeds from borrowing of long-term debt									$ 20,000
Wells Fargo
Liquidity
Remaining lease payments								112,800							112,800								112,800
Letter of credit								30,700							30,700								30,700
Loan and security agreement | Generate Lending, LLC
Liquidity
Repayments of finance obligations												$ 17,600
Loan and security agreement | Generate Lending, LLC | Secured term loan facility
Liquidity
Proceeds from borrowing of long-term debt											$ 15,000	85,000
Outstanding balance								112,700							112,700								112,700
Interest rate (as a percent)									12.00%
Termination of certain equipment leases												$ 50,300
Convertible Senior Notes
Liquidity
Principal amount										$ 40,000				$ 100,000		$ 40,000						$ 100,000
Interest rate (as a percent)										7.50%				5.50%		7.50%						5.50%
$40M Convertible Senior Note
Liquidity
Proceeds from issuance of debt										$ 39,100
Outstanding balance								39,600							39,600								39,600
Principal amount								$ 48,000		$ 40,000					$ 48,000	$ 40,000							$ 48,000
Interest rate (as a percent)										7.50%						7.50%
Obligation, net of interest accretion										$ 48,000						$ 48,000
Share price (in dollars per share)								$ 3.16							$ 3.16								$ 3.16
$100M Convertible Senior Notes
Liquidity
Proceeds from issuance of debt				$ 52,356										$ 95,900
Outstanding balance								$ 70,600							$ 70,600								$ 70,600
Principal amount				100,000				$ 100,000						$ 100,000	$ 100,000							$ 100,000	$ 100,000
Interest rate (as a percent)														5.50%								5.50%
Purchase of capped call and common stock forward				$ 43,500										$ 43,500
Share price (in dollars per share)								$ 3.16							$ 3.16								$ 3.16
Series E Preferred Stock
Liquidity
Number of redeemed shares							4,038									4,038
Amount of redeemed shares																$ 4,000
Number of preferred shares that had been converted to common stock							500
Series E Redeemable Convertible Preferred Stock
Liquidity
Shares issued (in shares)													35,000
Redeemable stock issued, stated value (in dollars per share)								$ 0.01					$ 0.01		0.01				$ 0.01				$ 0.01	$ 0.01
Number of shares of common stock issued on conversion of preferred stock							216,000
Aggregate proceeds from issuance of preferred stock													$ 30,900
At Market Issuance Sales Agreement
Liquidity
Proceeds from public offerings, net of transaction costs																							$ 14,500
Value of shares issued	$ 46,800	$ 46,800
Number of common stock sold																							6,300,000
Redeemable stock issued, stated value (in dollars per share)						$ 0.01
Authorized amount						$ 75,000
Public Offerings
Liquidity
Proceeds from public offerings, net of transaction costs								$ 120,400															$ 120,400
Number of common stock sold								46,000,000				10,000,000											46,000,000
Share price (in dollars per share)								$ 2.75				$ 2.35			$ 2.75			$ 2.35					$ 2.75
Number of shares of common stock issued on conversion of preferred stock															13,800,000

Summary of Significant Accoun_4

Summary of Significant Accounting Policies (Details) - USD ($) $ in Thousands	Mar. 08, 2018	Sep. 30, 2019	Mar. 31, 2018	Dec. 31, 2019	Dec. 31, 2018
Summary of Significant Accounting Policies
Upfront revenue recognized				$ 0
Principal amount			$ 100,000
Proceeds from issuance of debt				$ 39,052	$ 95,856
Maturity principal amount		$ 48,000
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%
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%
Convertible Senior Notes
Summary of Significant Accounting Policies
Principal amount		$ 40,000	$ 100,000
Interest rate (as a percent)		7.50%	5.50%
$40M Convertible Senior Note
Summary of Significant Accounting Policies
Principal amount		$ 40,000		$ 48,000
Interest rate (as a percent)		7.50%
Proceeds from issuance of debt		$ 39,100
Percentage of principal amount to be repaid at maturity		120.00%
Maturity principal amount		$ 48,000
Unamortized debt discount		$ 8,000		7,400
$100M Convertible Senior Notes
Summary of Significant Accounting Policies
Principal amount	$ 100,000		$ 100,000	100,000
Interest rate (as a percent)			5.50%
Proceeds from issuance of debt	$ 52,356		$ 95,900
Percentage of principal amount to be repaid at maturity		100.00%
Unamortized debt discount				$ 27,818

Summary of Significant Accoun_5

Summary of Significant Accounting Policies - Receivable, Inventory, And Intangible Assets (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Revenue Recognition from Customers [Abstract]
Contract with Customer, Liability	$ 43,480	$ 40,476
Accounts Receivable
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	$ 249	249
Stock-Based Compensation
Tax benefit (expense) for stock-based compensation	$ 0	$ 0	$ 0
Minimum
Sale/leaseback transactions
Lease term	6 years
Intangible Assets
Intangible asset useful lives	5 years
Maximum
Sale/leaseback transactions
Lease term	7 years
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

Summary of Significant Accoun_6

Summary of Significant Accounting Policies - Equity Instruments (Details) - USD ($) $ in Thousands	3 Months Ended				12 Months Ended
	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2019
Warrant expense	$ (2,807)	$ (1,496)	$ (1,017)	$ (1,193)	$ (6,513)
Previously Reported
Warrant expense	$ (2,807)	(4,583)	(1,483)	(4,179)	(13,052)
Restatement adjustment
Warrant expense		$ 3,087	$ 466	$ 2,986	$ 6,539

Summary of Significant Accoun_7

Summary of Significant Accounting Policies - Recent Accounting Pronouncements (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2019	Jan. 01, 2018
Summary of Significant Accounting Policies
Decrease in accrued expenses	$ 7,864	$ 14,213
Recognition of finance obligation		(171,327)
Decrease in prepaid expenses and other assets	14,357	21,192
Decrease in leased property, net of accumulated depreciation	(146,751)	(244,740)
Increase in accumulated deficit	(1,260,290)	$ (1,345,807)
Decrease of depreciation expenses	$ 300
ASU 2016-02 | Early adoption | Restatement adjustment
Summary of Significant Accounting Policies
Recognition of right of use asset			$ 34,416
Decrease in accrued expenses			385
Recognition of finance obligation			(34,161)
Decrease in prepaid expenses and other assets			(3,229)
Decrease in leased property, net of accumulated depreciation			(563)
Increase in accumulated deficit			$ 3,487

Earnings Per Share - Basic and

Earnings Per Share - Basic and Diluted Components (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Numerator:
Net loss attributable to common shareholders	$ (18,288)	$ (18,155)	$ (18,070)	$ (31,004)	$ (16,860)	$ (15,578)	$ (25,881)	$ (19,848)	$ (85,517)	$ (78,167)	$ (130,178)
Denominator:
Weighted average number of common stock outstanding									237,152,780	218,882,337	216,343,985

Earnings Per Share - Dilutive P

Earnings Per Share - Dilutive Potential Common Shares (Details) - USD ($) $ / shares in Units, $ in Thousands	Nov. 01, 2018	Apr. 12, 2017	Dec. 22, 2016	May 16, 2013	Jan. 31, 2020	Apr. 30, 2017	Dec. 31, 2019	Sep. 30, 2019	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017	Mar. 31, 2018	Mar. 08, 2018	Jul. 31, 2017	Jul. 20, 2017	Apr. 04, 2017
Earnings Per Share
Number of dilutive potential common stock									200,327,965	201,692,250	138,713,090
Exercise price of warrants (in dollars per share)															$ 2.1231
Number of preferred shares that had been converted to common stock							30,962
Principal amount												$ 100,000
Stock options
Earnings Per Share
Stock options granted									3,221,892	2,679,667	5,485,863
Warrants issued in December 2016
Earnings Per Share
Number of warrants issued (in shares)			10,501,500
Shares of common stock that can be purchased from warrants issued (in shares)		5,250,750
Number of warrants exercised (in shares)		10,501,500
Exercise price of warrants (in dollars per share)			$ 1.50
Warrants issued in April 2017
Earnings Per Share
Number of warrants issued (in shares)						5,250,750
Exercise price of warrants (in dollars per share)						$ 2.69
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)						55,286,696										55,286,696
Warrant shares vested (in shares)							20,368,782		20,368,782	20,368,782
Number of warrants exercised (in shares)									0
Tranche one of warrants issued with the Amazon.com, Inc transaction agreement
Earnings Per Share
Warrant shares vested (in shares)																5,819,652
Warrants issued with the Walmart transaction agreement
Earnings Per Share
Shares of common stock that can be purchased from warrants issued (in shares)														55,286,696
Tranche one of warrants issued with the Walmart Stores Inc transaction agreement
Earnings Per Share
Warrant shares vested (in shares)															5,819,652
Series C Preferred Stock
Earnings Per Share
Stock options granted				10,431
Conversion of preferred stock (in shares)											7,811
Series D Redeemable Convertible Preferred Stock
Earnings Per Share
Number of preferred shares that had been converted to common stock											14,800
Shares issued (in shares)			18,500
Number of shares redeemed											3,700
Series E Preferred Stock
Earnings Per Share
Number of preferred shares that had been converted to common stock					500
Conversion of preferred stock (in shares)	35,000								30,462
Number of redeemed shares					4,038			4,038
Convertible Senior Notes
Earnings Per Share
Principal amount								$ 40,000				$ 100,000
Interest rate (as a percent)								7.50%				5.50%
$40M Convertible Senior Note
Earnings Per Share
Principal amount							$ 48,000	$ 40,000	$ 48,000
Interest rate (as a percent)								7.50%
$100M Convertible Senior Notes
Earnings Per Share
Principal amount							$ 100,000		$ 100,000			$ 100,000	$ 100,000
Interest rate (as a percent)												5.50%
Stock options
Earnings Per Share
Number of dilutive potential common stock									23,013,590	21,957,150	19,872,029
Restricted stock
Earnings Per Share
Number of dilutive potential common stock									4,608,560	2,347,347	234,744
Stock options granted									3,201,892	2,367,347	234,744
Warrants
Earnings Per Share
Number of dilutive potential common stock									110,573,392	115,824,142	115,824,242
Preferred stock
Earnings Per Share
Number of dilutive potential common stock									2,998,527	17,933,591	2,782,075
Convertible Senior Notes
Earnings Per Share
Number of dilutive potential common stock									59,133,896	43,630,020

Inventory (Details)

Inventory (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Inventory
Raw materials and supplies - production locations	$ 48,011	$ 32,941
Raw materials and supplies - customer locations	9,241	6,755
Work-in-process	12,529	5,589
Finished goods	2,610	2,625
Inventory	$ 72,391	$ 47,910

Property, Plant and Equipment_2

Property, Plant and Equipment (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Property, plant and equipment
Property, plant, and equipment, gross	$ 32,376	$ 27,272
Less: accumulated depreciation	(17,417)	(14,403)
Property, plant, and equipment, net	14,959	12,869
Depreciation expense	3,600	2,600	$ 1,900
Leasehold Improvements
Property, plant and equipment
Property, plant, and equipment, gross	862	214
Software, machinery and equipment
Property, plant and equipment
Property, plant, and equipment, gross	$ 31,514	$ 27,058

Leased Property (Details)

Leased Property (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Leased Property
Right of use assets - operating	$ 198,068	$ 76,747
Right of use assets - finance	41,475	39,905
Capitalized costs of lessor assets	41,465	41,040
Less: accumulated depreciation	(36,268)	(10,941)
Leased property, net	244,740	146,751
Depreciation	$ 8,400	$ 8,400	$ 7,300

Intangible Assets - Gross Carry

Intangible Assets - Gross Carrying Amount (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017	May 31, 2019
Gross carrying amount and accumulated amortization of acquired identifiable intangible assets
Gross Carrying Amount	$ 8,564	$ 6,246
Accumulated Amortization	(3,025)	(2,356)
Total	5,539	3,890
Payments to Acquire Intangible Assets	2,404	929
Payables for acquiring Intellectual Property	14,213	7,864
Amortization of intangible assets	698	$ 693	$ 593
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
Payments to Acquire Intangible Assets	400
Payables for acquiring Intellectual Property	$ 500
Acquired technology
Gross carrying amount and accumulated amortization of acquired identifiable intangible assets
Weighted Average Amortization Period	10 years	9 years
Gross Carrying Amount	$ 8,244	$ 5,926
Accumulated Amortization	(2,815)	(2,176)
Total	$ 5,429	$ 3,750
Customer relationships
Gross carrying amount and accumulated amortization of acquired identifiable intangible assets
Weighted Average Amortization Period	10 years	10 years
Gross Carrying Amount	$ 260	$ 260
Accumulated Amortization	(150)	(123)
Total	$ 110	$ 137
Trademark
Gross carrying amount and accumulated amortization of acquired identifiable intangible assets
Weighted Average Amortization Period	5 years	5 years
Gross Carrying Amount	$ 60	$ 60
Accumulated Amortization	$ (60)	(57)
Total		$ 3

Intangible Assets - Estimated A

Intangible Assets - Estimated Amortization Expense (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Intangible Assets
Amortization of Intangible Assets	$ 698	$ 693	$ 593
Estimated amortization expense
2020	801
2021	801
2022	801
2023	801
2024 and thereafter	2,335
Total	$ 5,539	$ 3,890

Accrued Expenses (Details)

Accrued Expenses (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Accrued Expenses
Accrued payroll and compensation related costs	$ 2,933	$ 2,150
Accrued accounts payable	7,254	1,790
Accrued sales and other taxes	905	1,478
Accrued interest	2,374	1,605
Accrued other	747	841
Total	$ 14,213	$ 7,864

Long-Term Debt (Details)

Long-Term Debt (Details) - USD ($) $ in Thousands	1 Months Ended			12 Months Ended
	Nov. 30, 2019	Apr. 30, 2019	Mar. 31, 2019	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017	Mar. 31, 2018
Long-Term Debt
Loan Amount							$ 100,000
Repayments of long-term debt and accrued interest				$ 61,713	$ 31,264	$ 18,632
Minimum structured finance arrangements				$ 50,000
Percent of securities in foreign subsidiaries guaranteed to secure debt				65.00%
Principal payments of long term debt
December 31, 2020				$ 86,159
December 31, 2021				59,373
Maximum
Long-Term Debt
Additional fees				$ 1,500
Secured term loan facility
Long-Term Debt
Borrowing	$ 20,000
Effective interest rate (as a percent)				12.00%
Term of loan agreement				3 years
Generate Lending, LLC | Loan and security agreement
Long-Term Debt
Repayments of long-term debt and accrued interest			$ 17,600
Termination of certain equipment leases			50,300
Generate Lending, LLC | Loan and security agreement
Long-Term Debt
Repayments of long-term debt and accrued interest			17,600
Generate Lending, LLC | Secured term loan facility | Loan and security agreement
Long-Term Debt
Loan Amount			100,000
Borrowing		$ 15,000	85,000
Generate Lending, LLC | Secured term loan facility | Loan and security agreement
Long-Term Debt
Borrowing		$ 15,000	85,000
Interest rate (as a percent)	12.00%
Termination of certain equipment leases			$ 50,300
Long-term borrowings				$ 112,700
NY Green Bank
Long-Term Debt
Loss on extinguishment of debt				500
Cash held in escrow deposit				1,700
Long-term borrowings				$ 112,700

Convertible Senior Notes - Net

Convertible Senior Notes - Net proceeds (Details)	Mar. 08, 2018USD ($)	Sep. 30, 2019USD ($)D$ / shares	Mar. 31, 2018USD ($)	Dec. 31, 2019USD ($)$ / shares	Dec. 31, 2018USD ($)	Mar. 31, 2019$ / shares
Convertible Senior Notes
Principal amount			$ 100,000,000
Proceeds from issuance of debt				$ 39,052,000	$ 95,856,000
Maturity principal amount		$ 48,000,000
Unamortized debt discount and issuance costs		1,000,000
Closing price of the company's stock | $ / shares						$ 2.35
$40M Convertible Senior Note
Convertible Senior Notes
Principal amount		$ 40,000,000		$ 48,000,000
Interest rate (as a percent)		7.50%
Proceeds from issuance of debt		$ 39,100,000
Percentage of principal amount to be repaid at maturity		120.00%
Maturity principal amount		$ 48,000,000
Conversion rates for the notes (in shares)		387.5969
Conversion price, per share | $ / shares		$ 2.58
Consecutive trading days | D		20
Conversion price (as a percent)		175.00%
Transaction costs for issuance		$ 8,000,000
Initial purchasers' discount		8,000,000
Remaining life of the convertible senior notes				37 months
Closing price of the company's stock | $ / shares				$ 3.16
Fair value of convertible senior notes				$ 53,500,000
$40M Convertible Senior Note | Level 3 | Volatility
Convertible Senior Notes
Volatility assumption				70
$40M Convertible Senior Note | Holder may require redemption
Convertible Senior Notes
Principal amount		40,000,000
Maturity principal amount		$ 48,000,000
Consecutive trading days | D		5
Principal amount of the repurchased Convertible Senior Notes(as a percent)		115.00%
Principal amount (as a percent)		110.00%
Conversion ratio, principal amount		$ 1,000
$40M Convertible Senior Note | Company may redeem with the consent of the holder
Convertible Senior Notes
Principal amount		40,000,000
Maturity principal amount		$ 48,000,000
Consecutive trading days | D		5
Principal amount of the repurchased Convertible Senior Notes(as a percent)		105.00%
Principal amount (as a percent)		115.00%
Conversion ratio, principal amount		$ 1,000
$100M Convertible Senior Notes
Convertible Senior Notes
Principal amount	$ 100,000,000		$ 100,000,000	$ 100,000,000
Interest rate (as a percent)			5.50%
Proceeds from issuance of debt	52,356,000		$ 95,900,000
Conversion rates for the notes (in shares)		436.3002
Conversion price, per share | $ / shares		$ 2.29
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%
Ownership interest percentage		50.00%
Percentage of principal amount to be redeemed		100.00%
Carrying amount of the liability component		$ 58,200,000
Carrying amount of the equity component		$ 37,700,000		37,702,000
Effective interest rate (as a percent)		16.00%
Transaction costs for issuance		$ 4,100,000
Initial purchasers' discount	3,300,000
Other issuance costs	$ 894,000			$ 1,700,000
Transaction costs attributable to the liability component		2,400,000
Transaction costs attributable to the equity component		$ 1,700,000
Remaining life of the convertible senior notes				39 months
Closing price of the company's stock | $ / shares				$ 3.16
Fair value of convertible senior notes				$ 135,300,000

Convertible Senior Notes (Detai

Convertible Senior Notes (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Sep. 30, 2019	Dec. 31, 2018	Mar. 31, 2018	Mar. 08, 2018
Convertible Senior Notes
Principal amount				$ 100,000
Net carrying amount	$ 110,246		$ 63,247
Convertible Senior Notes
Convertible Senior Notes
Principal amount		$ 40,000		100,000
$40M Convertible Senior Note
Convertible Senior Notes
Principal amount	48,000	40,000
Unamortized debt discount	(7,400)	(8,000)
Unamortized debt issuance costs	(969)
Net carrying amount	39,631
$100M Convertible Senior Notes
Convertible Senior Notes
Principal amount	100,000			$ 100,000	$ 100,000
Unamortized debt discount	(27,818)
Unamortized debt issuance costs	(1,567)
Net carrying amount	70,615
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	Mar. 08, 2018	Sep. 30, 2019	Mar. 31, 2018	Dec. 31, 2019	Dec. 31, 2018
Convertible Senior Notes
Debt Instrument, Face Amount			$ 100,000
Less cost of related capped call and common stock forward					$ (43,500)
Proceeds from Issuance of Debt				$ 39,052	$ 95,856
Convertible Senior Notes
Convertible Senior Notes
Debt Instrument, Face Amount		$ 40,000	100,000
$40M Convertible Senior Note
Convertible Senior Notes
Debt Instrument, Face Amount		40,000		48,000
Less initial purchasers' discount		(8,000)
Proceeds from Issuance of Debt		$ 39,100
$100M Convertible Senior Notes
Convertible Senior Notes
Debt Instrument, Face Amount	$ 100,000		100,000	100,000
Less initial purchasers' discount	(3,250)
Less initial purchasers' discount	(3,300)
Less cost of related capped call and common stock forward	(43,500)		(43,500)
Less other issuance costs	(894)			$ (1,700)
Proceeds from Issuance of Debt	$ 52,356		$ 95,900

Convertible Senior Notes - Capp

Convertible Senior Notes - Capped Call and Common Stock Forward (Details) - USD ($) $ / shares in Units, $ in Millions	1 Months Ended		12 Months Ended
	Sep. 30, 2019	Mar. 31, 2019	Dec. 31, 2019
Capped Call and Common Stock Forward
Share Price		$ 2.35
Common stock shares issued		10,000,000
Capped Call
Capped Call and Common Stock Forward
Capped call options amount	$ 16
Cap price	$ 3.82
Premium (as a percent)	100.00%
Share Price	$ 1.91
Common Stock Forward
Capped Call and Common Stock Forward
Common stock shares issued			14,397,906
Net cost incurred			$ 27.5

Stockholders' Equity - Common S

Stockholders' Equity - Common Stock and Warrants (Details) $ / shares in Units, $ in Thousands	Dec. 02, 2019USD ($)	Oct. 29, 2019USD ($)	Apr. 12, 2017USD ($)$ / sharesshares	Apr. 03, 2017USD ($)$ / shares	Dec. 22, 2016$ / sharesshares	Dec. 31, 2019USD ($)$ / sharesshares	Sep. 30, 2019USD ($)	Mar. 31, 2019USD ($)$ / sharesshares	Dec. 31, 2019USD ($)item$ / sharesshares	Dec. 31, 2018USD ($)$ / sharesshares	Dec. 31, 2017USD ($)shares	Mar. 31, 2018USD ($)	Jul. 20, 2017$ / shares
Stockholders' equity
Preferred stock, Shares authorized | shares						5,000,000			5,000,000
Preferred stock, par value | $ / shares						$ 0.01			$ 0.01
Common Stock Shares, Outstanding | shares						303,378,515			303,378,515	219,157,998
Common stock, par value (in dollars per share) | $ / shares				$ 0.01		$ 0.01			$ 0.01	$ 0.01
Principal amount												$ 100,000
Maturity principal amount							$ 48,000
Proceeds from issuance of debt									$ 39,052	$ 95,856
Number of votes per share | item									1
Common stock shares issued | shares								10,000,000
Par value, common stock | $ / shares				$ 0.01		0.01			$ 0.01	$ 0.01
Share price (in dollars per share) | $ / shares								$ 2.35
Proceeds from public offerings, net of transaction costs								$ 23,500	$ 158,428	$ 7,195	$ 22,992
Exercise price of warrants (in dollars per share) | $ / shares													$ 2.1231
Value of shares issued									$ 158,429	$ 7,016	$ 22,992
Series A Junior Participating Cumulative Preferred Stock
Stockholders' equity
Preferred stock, par value | $ / shares						$ 0.01			$ 0.01	$ 0.01
Common Stock Shares, Outstanding | shares						0			0	0
At Market Issuance Sales Agreement
Stockholders' equity
Common stock shares issued | shares									6,300,000
Proceeds from public offerings, net of transaction costs									$ 14,500
Authorized amount				$ 75,000
Value of shares issued	$ 46,800	$ 46,800
Gross proceeds from sales of fixed combination of the shares and the warrants									$ 15,300
Public Offerings
Stockholders' equity
Common stock shares issued | shares						46,000,000		10,000,000	46,000,000
Share price (in dollars per share) | $ / shares						$ 2.75		$ 2.35	$ 2.75
Proceeds from public offerings, net of transaction costs						$ 120,400			$ 120,400
Warrants issued in December 2016
Stockholders' equity
Class of Warrant or Right, Number of Securities Called by Warrants or Rights | shares			5,250,750
Class of Warrant or Right Issued | shares					10,501,500
Exercise price of warrants (in dollars per share) | $ / shares					$ 1.50
Number of warrants exercised (in shares) | shares			10,501,500
Proceeds from exercise of warrants, net of transaction costs			$ 15,100
Shares of common stock that can be purchased from warrants issued | shares			5,250,750
Per share price of shares of common stock | $ / shares			$ 2.69
Warrant Issued With Amazon And Walmart Stores Inc Transaction Agreement In 2017
Stockholders' equity
Number of warrants exercised (in shares) | shares									26,188,434	26,188,434
Warrant Issued With Amazon And Walmart Stores Inc Transaction Agreement In 2017 | Maximum
Stockholders' equity
Class of Warrant or Right Issued | shares											110,573,392
$40M Convertible Senior Note
Stockholders' equity
Principal amount						48,000	$ 40,000		$ 48,000
Interest rate (as a percent)							7.50%
Maturity principal amount							$ 48,000
Long-term borrowings						$ 39,600			$ 39,600
Proceeds from issuance of debt							$ 39,100
Share price (in dollars per share) | $ / shares						$ 3.16			$ 3.16

Redeemable Convertible Prefer_2

Redeemable Convertible Preferred Stock (Details)	Dec. 22, 2016shares	Nov. 30, 2018USD ($)shares	Dec. 31, 2019USD ($)installment$ / sharesshares	Dec. 31, 2019USD ($)installment$ / sharesshares	Dec. 31, 2017shares	Dec. 31, 2018$ / sharesshares
Redeemable preferred stock
Number of preferred shares that had been converted to common stock			30,962
Series C Redeemable Convertible Preferred Stock
Redeemable preferred stock
Conversion price per share | $ / shares			$ 0.2343	$ 0.2343		$ 0.2343
Preferred Stock, Shares Outstanding			2,620	2,620		2,620
Dividend rate				8.00%
Original issue price | $				$ 248.794
Series C Redeemable Convertible Preferred Stock | Minimum
Redeemable preferred stock
Conversion price per share | $ / shares			$ 0.1554	$ 0.1554
Series D Redeemable Convertible Preferred Stock
Redeemable preferred stock
Shares issued (in shares)	18,500
Number of preferred shares that had been converted to common stock					14,800
Series E Redeemable Convertible Preferred Stock
Redeemable preferred stock
Shares issued (in shares)		35,000
Net proceeds from public offering | $		$ 30,900,000
Number of monthly installments | installment			13	13
Redemption value for each installment | $			$ 2,700,000	$ 2,700,000
Discount on market price			15.00%	15.00%
Conversion price per share | $ / shares			$ 2.31	$ 2.31
Preferred Stock, Shares Outstanding			500	500		35,000
Number of redeemed shares				4,038
Amount of redeemed shares | $				$ 4,000,000
Number of preferred shares that had been converted to common stock				30,462
Number of shares of common stock issued on conversion of preferred stock				13,800,000
Liquidation preference percentage				125.00%
Redeemable stock issued, initial stated value (in dollars per share) | $ / shares				$ 1,000

Warrant Transaction Agreements

Warrant Transaction Agreements - Amazon.com, Inc. Transaction Agreement (Details) $ / shares in Units, $ in Thousands	Apr. 04, 2017USD ($)installment$ / sharesshares	Dec. 31, 2017USD ($)	Dec. 31, 2019USD ($)shares	Dec. 31, 2018USD ($)shares	Dec. 31, 2017USD ($)	Jul. 20, 2017$ / shares	Apr. 30, 2017shares
Class of Warrant or Right [Line Items]
Selling, general and administrative | $			$ 44,333	$ 38,198	$ 45,010
Exercise price of warrants (in dollars per share) | $ / shares						$ 2.1231
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	55,286,696						55,286,696
Cash payments to be received under agreement | $	$ 600,000
Warrant shares vested (in shares) | shares			20,368,782	20,368,782
Aggregate cash receipts for all installments | $	$ 200,000
Provision for common stock warrants | $			$ 4,100	$ 9,800
Tranche one of warrants issued with the Amazon.com, Inc transaction agreement
Class of Warrant or Right [Line Items]
Warrant shares vested (in shares) | shares	5,819,652
Selling, general and administrative | $		$ 6,700			$ 6,700
Tranche two 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	29,098,260
Warrant shares vested (in shares) | shares	29,098,260
Number of installments | installment	4
Number of shares per installment | shares	7,274,565
Cash receipt per installment | $	$ 50,000
Aggregate cash receipts for all installments | $	$ 200,000
Exercise price of warrants (in dollars per share) | $ / shares	$ 1.1893
Tranche three 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	20,368,784
Warrant shares vested (in shares) | shares	20,368,784
Number of installments | installment	8
Number of shares per installment | shares	2,546,098
Cash receipt per installment | $	$ 50,000
Aggregate cash receipts for all installments | $	$ 400,000
Exercise price calculation	The exercise price of the third tranche of Amazon 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 Amazon Warrant Shares

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, 2019USD ($)	Dec. 31, 2018USD ($)shares	Dec. 31, 2017USD ($)
Warrant Transaction Agreements
Exercise price of warrants (in dollars per share) | $ / shares	$ 2.1231
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
Warrant shares vested (in shares) | shares			5,819,652
Provision for common stock warrants | $		$ 2.4	$ 0.4
Warrants issued with the Walmart Stores, Inc transaction agreement | Maximum
Warrant Transaction Agreements
Cash payments to be received under agreement | $	$ 600
Tranche one of warrants issued with the Walmart Stores Inc transaction agreement
Warrant Transaction Agreements
Warrant shares vested (in shares) | shares	5,819,652
Provision for common stock warrants | $				$ 10.9
Tranche two of warrants issued with the Walmart Stores, Inc. Transaction Agreement
Warrant Transaction Agreements
Warrant shares vested (in shares) | shares	29,098,260
Number of installments | installment	4
Number of shares per installment | shares	7,274,565
Cash receipt per installment | $	$ 50
Aggregate cash receipts for all installments | $	$ 200
Tranche three of warrants issued with the Walmart Stores, Inc. Transaction Agreement
Warrant Transaction Agreements
Warrant shares vested (in shares) | shares	20,368,784
Number of installments | installment	8
Number of shares per installment | shares	2,546,098
Cash receipt per installment | $	$ 50
Aggregate cash receipts for all installments | $	$ 400
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
Exercise price of warrants (in dollars per share) | $ / shares	$ 1.1893

Revenue - Disaggregation of Rev

Revenue - Disaggregation of Revenue (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Revenue
Net revenue	$ 91,664	$ 59,461	$ 57,535	$ 21,579	$ 59,820	$ 53,165	$ 35,229	$ 26,418
Net revenue									$ 230,239	$ 174,632	$ 100,153
Sales of fuel cell systems
Revenue
Net revenue									130,721	75,146	49,206
Sale of hydrogen installations and other infrastructure
Revenue
Net revenue									19,163	32,146	13,425
Services performed on fuel cell systems and related infrastructure
Revenue
Net revenue	7,328	6,205	5,341	6,343	5,672	5,156	5,691	5,483	25,217	22,002	16,202
Power Purchase Agreements
Revenue
Net revenue	6,739	6,595	6,409	6,110	6,504	5,555	5,438	5,372	25,853	22,869	12,869
Fuel delivered to customers
Revenue
Net revenue	7,779	7,649	$ 7,089	$ 6,582	$ 6,453	$ 5,786	$ 5,280	$ 4,950	29,099	$ 22,469	8,167
Other
Revenue
Net revenue	$ 51	$ 135							$ 186		$ 284

Revenue - Contract balances (De

Revenue - Contract balances (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Revenue
Accounts receivable	$ 25,448	$ 37,347
Contract assets	13,251	3,328
Contract liabilities	$ 43,480	$ 40,476

Revenue - Changes in contract a

Revenue - Changes in contract assets and contract liabilities (Details) $ in Thousands	12 Months Ended
	Dec. 31, 2019USD ($)
Contract assets
Transferred to receivables from contract assets recognized at the beginning of the period	$ (1,252)
Revenue recognized and not billed as of the end of the period	11,175
Net change in contract assets	9,923
Contract liabilities
Revenue recognized that was included in the contract liability balance as of the beginning of the period	(10,172)
Increases due to cash received, net of amounts recognized as revenue during the period	13,175
Net change in contract liabilities	$ 3,003

Revenue - Estimated future reve

Revenue - Estimated future revenue (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Revenue
Total estimated future revenue	$ 371,841	$ 218,006
Sales of fuel cell systems
Revenue
Total estimated future revenue	73,491	17,318
Sale of hydrogen installations and other infrastructure
Revenue
Total estimated future revenue	72,862	9,141
Services performed on fuel cell systems and related infrastructure
Revenue
Total estimated future revenue	87,020	73,381
Power Purchase Agreements
Revenue
Total estimated future revenue	133,475	111,533
Other
Revenue
Total estimated future revenue	$ 4,993	$ 6,633
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, 2019	Dec. 31, 2018
Revenue
Capitalized contract costs	$ 0.5	$ 0.2

Employee Benefit Plans - Assump

Employee Benefit Plans - Assumptions For Estimating Fair Value (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017	May 12, 2011
Employee Benefit Plans
Compensation cost	$ 8.8	$ 7.4	$ 9
Assumptions for estimating fair value
Dividend Yield	0.00%
Stock options
Employee Benefit Plans
Number of options outstanding (in shares)	23,013,590	21,957,150
Compensation cost	$ 6	$ 6.4	$ 8.6
Stock options granted	3,221,892	2,679,667	5,485,863
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):	1.52%	2.81%	1.89%
Volatility (as a percent):	69.32%	98.31%	99.24%
Stock options | Maximum
Assumptions for estimating fair value
Risk free rate (as a percent):	2.53%	2.88%	2.16%
Volatility (as a percent):	87.94%	98.89%	102.16%
the 2011 Plan | Stock options
Employee Benefit Plans
Maximum number of common stock shares available for issuance	42,400,000			1,000,000
Aggregate number of options granted (in shares)	23,000,000
Number of options available for issuance (in shares)	8,400,000
Expiration period	10 years
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, 2019	Dec. 31, 2018	Dec. 31, 2017
Shares
Options outstanding, beginning balance (in shares)	21,957,150
Granted (in shares)	3,221,892	2,679,667	5,485,863
Exercised (in shares)	(1,151,307)
Forfeited (in shares)	(934,195)
Expired (in shares)	(79,950)
Options outstanding, end balance (in shares)	23,013,590	21,957,150
Options exercisable (in shares)	16,608,362
Options unvested (in shares)	6,405,228
Weighted Average Exercise Price
Options outstanding, beginning balance, weighted-average exercise price	$ 2.51
Granted, weighted-average exercise price	2.40
Exercised, weighted-average exercise price	1.56
Forfeited, weighted-average exercise price	3.50
Expired, weighted-average exercise price	9.43
Options outstanding, end balance, weighted-average exercise price	2.48	$ 2.51
Options exercisable, weighted-average exercise price	2.57
Options unvested, weighted-average exercise price	$ 2.22
Stock option activity additional disclosures
Options outstanding, weighted-average remaining contractual term	6 years 7 months 6 days	7 years 1 month 6 days
Options exercisable, weighted-average remaining contractual term	5 years 9 months 18 days
Options unvested, weighted-average remaining contractual term	8 years 10 months 24 days
Options outstanding, aggregate intrinsic value	$ 22,277	$ 1,432
Options exercisable, aggregate intrinsic value	16,285
Options unvested, aggregate intrinsic value	$ 5,992
Weighted-average grant date fair value of options granted (per share)	$ 1.67	$ 1.55	$ 1.67
Unrecognized compensation cost	$ 8,100
Period for recognition	3 years
Fair value of stock options that vested during the period	$ 6,100	$ 7,100

Employee Benefit Plans - Restri

Employee Benefit Plans - Restricted Stock Activity (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Employee Benefit Plans
Compensation cost	$ 8,800	$ 7,400	$ 9,000
Restricted stock
Employee Benefit Plans
Compensation cost	2,800	966	335
Unrecognized compensation cost	$ 8,400	$ 3,900	$ 208
Period for recognition	3 years
Shares
Unvested restricted stock, beginning balance (in shares)	2,347,347
Granted (in shares)	3,201,892
Vested (in shares)	(920,679)
Forfeited (in shares)	(20,000)
Unvested restricted stock, end balance (in shares)	4,608,560	2,347,347
Aggregate Intrinsic Value
Unvested restricted stock aggregate intrinsic value	$ 14,563
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, 2019	Dec. 31, 2018	Dec. 31, 2017
Employee Benefit Plan Compensation
Compensation cost	$ 8,800	$ 7,400	$ 9,000
Non Employee Director
Employee Benefit Plan Compensation
Granted (in shares)	114,285	107,389	148,077
Compensation cost	$ 243	$ 261	$ 276
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	841,539	633,827
Total expense (including issuance of shares)	$ 1,900	$ 1,800	$ 1,600

Fair Value Measurements - Recur

Fair Value Measurements - Recurring Basis (Details) - Recurring basis - Warrants $ in Thousands	Dec. 31, 2018USD ($)
Fair Value
Financial liabilities	$ 105
Level 3
Fair Value
Financial liabilities	$ 105

Fair Value Measurements - Valua

Fair Value Measurements - Valuation Technique (Details) $ in Millions	Jan. 01, 2019	Dec. 31, 2018	Dec. 31, 2019USD ($)
$40M Convertible Senior Note
Valuation technique for assets and liabilities measured and recorded at fair value
Fair value of convertible senior notes			$ 53.5
$100M Convertible Senior Notes
Valuation technique for assets and liabilities measured and recorded at fair value
Fair value of convertible senior notes			$ 135.3
Volatility | $40M Convertible Senior Note | Level 3
Valuation technique for assets and liabilities measured and recorded at fair value
Debt Instrument, Measurement Input			70
Derivative Liabilities | Expected dividend yield
Valuation technique for assets and liabilities measured and recorded at fair value
Derivative Liability, Measurement Input			0
Minimum | Warrants | Risk free interest rate
Valuation technique for assets and liabilities measured and recorded at fair value
Equity Instrument, Measurement Input	2.60
Minimum | Warrants | Volatility
Valuation technique for assets and liabilities measured and recorded at fair value
Equity Instrument, Measurement Input		75
Minimum | Derivative Liabilities | Risk free interest rate
Valuation technique for assets and liabilities measured and recorded at fair value
Derivative Liability, Measurement Input		1.64
Minimum | Derivative Liabilities | Volatility
Valuation technique for assets and liabilities measured and recorded at fair value
Derivative Liability, Measurement Input		18.40
Minimum | Derivative Liabilities | Expected average term
Valuation technique for assets and liabilities measured and recorded at fair value
Derivative Liability, Expected average term		4 days
Minimum | Warrants | Risk free interest rate
Valuation technique for assets and liabilities measured and recorded at fair value
Equity Instrument, Measurement Input		2.60
Minimum | Warrants | Expected average term
Valuation technique for assets and liabilities measured and recorded at fair value
Equity Instrument Expected average term	8 years 3 months 4 days	8 years 3 months 4 days
Maximum | Warrants | Risk free interest rate
Valuation technique for assets and liabilities measured and recorded at fair value
Equity Instrument, Measurement Input	2.63
Maximum | Warrants | Volatility
Valuation technique for assets and liabilities measured and recorded at fair value
Equity Instrument, Measurement Input		85
Maximum | Warrants | Expected average term
Valuation technique for assets and liabilities measured and recorded at fair value
Equity Instrument Expected average term	8 years 6 months 18 days
Maximum | Derivative Liabilities | Risk free interest rate
Valuation technique for assets and liabilities measured and recorded at fair value
Derivative Liability, Measurement Input		2.66
Maximum | Derivative Liabilities | Volatility
Valuation technique for assets and liabilities measured and recorded at fair value
Derivative Liability, Measurement Input		81.69
Maximum | Derivative Liabilities | Expected average term
Valuation technique for assets and liabilities measured and recorded at fair value
Derivative Liability, Expected average term		1 year 6 months 11 days
Maximum | Warrants | Risk free interest rate
Valuation technique for assets and liabilities measured and recorded at fair value
Equity Instrument, Measurement Input		3.02
Maximum | Warrants | Expected average term
Valuation technique for assets and liabilities measured and recorded at fair value
Equity Instrument Expected average term		9 years 3 months 18 days
Weighted Average | Warrants | Volatility
Valuation technique for assets and liabilities measured and recorded at fair value
Equity Instrument, Measurement Input	0.95

Fair Value Measurements - Level

Fair Value Measurements - Level 3 Instruments Reconciliation (Details) - Warrants - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Reconciliations of the beginning and ending balances for liabilities measured at fair value on a recurring basis using significant unobservable inputs (i.e. Level 3)
Balance at the beginning of the period	$ 105	$ 4,391
Change in fair value of common stock warrants	(79)	(4,286)
Exercise of common stock warrants	$ (26)
Balance at the end of the period		$ 105

Fair Value Measurements - Fair

Fair Value Measurements - Fair Value of Warrants (Details)	12 Months Ended
	Dec. 31, 2019$ / shares
Tranche one of warrants issued with the Amazon.com, Inc transaction agreement
Fair Value
Fair value per warrant	$ 1.15
Tranche two of warrants issued with the Amazon.com, Inc. Transaction Agreement
Fair Value
As of vesting date, first installment - second tranche	2.16
As of vesting date, second installment - second tranche	1.54
As of period end - second tranche	1.05
As of prior period end - second tranche	0.98
Tranche one of warrants issued with the Walmart Stores Inc transaction agreement
Fair Value
Fair value per warrant	1.88
Tranche two of warrants issued with the Walmart Stores, Inc. Transaction Agreement
Fair Value
As of period end - second tranche	1
As of prior period end - second tranche	$ 0.92

Income Taxes - Components Of In

Income Taxes - Components Of Income Tax (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Components of loss before income taxes and the provision for income taxes
Loss before income taxes	$ (85,465)	$ (87,332)	$ (127,080)
Income tax benefit		(9,217)
Net loss attributable to the Company	(85,465)	(78,115)	(127,080)
significant components deferred income tax (benefit) expense
Deferred tax (benefit) expense	(9,336)	(9,249)	7,144
Net operating loss carryforward generated	(7,524)	(10,703)	(19,134)
Rate change impact on net operating loss carryforwards			23,609
Valuation allowance increase (decrease)	16,860	10,735	(11,619)
U.S.
Components of loss before income taxes and the provision for income taxes
Loss before income taxes	(83,910)	(85,925)	(125,871)
Income tax benefit		(9,217)
Net loss attributable to the Company	(83,910)	(76,708)	(125,871)
significant components deferred income tax (benefit) expense
Deferred tax (benefit) expense	(8,910)	(10,182)	7,675
Net operating loss carryforward generated	(7,254)	(10,038)	(19,117)
Rate change impact on net operating loss carryforwards			23,609
Valuation allowance increase (decrease)	16,164	11,003	(12,167)
Foreign
Components of loss before income taxes and the provision for income taxes
Loss before income taxes	(1,555)	(1,407)	(1,209)
Net loss attributable to the Company	(1,555)	(1,407)	(1,209)
significant components deferred income tax (benefit) expense
Deferred tax (benefit) expense	(426)	933	(531)
Net operating loss carryforward generated	(270)	(665)	(17)
Valuation allowance increase (decrease)	$ 696	$ (268)	$ 548

Income Taxes - Effective Income

Income Taxes - Effective Income Tax Rate Reconciliation (Details)	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Effective income tax rate reconciliation
U.S. Federal statutory tax rate	(21.00%)	(21.00%)	(35.00%)
Deferred state taxes	1.20%	(1.90%)	(1.40%)
Common stock warrant liability		(1.00%)	4.20%
Provision to return and deferred tax asset adjustments			5.90%
Change in U.S. Federal statutory tax rate			33.50%
Other, net	(0.50%)	0.40%	2.00%
Change in valuation allowance	20.30%	12.90%	(9.20%)
Total effective income tax rate	0.00%	(10.60%)	0.00%

Income Taxes - Deferred Tax Ass

Income Taxes - Deferred Tax Assets And Liabilities (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Significant components of the Company's deferred tax assets and liabilities
Intangible assets	$ 1,197	$ 1,146
Deferred revenue	8,027	9,304
Interest expense	11,299	5,239
Other reserves and accruals	699	592
Tax credit carryforwards	3,843	3,065
Amortization of stock-based compensation	9,081	8,442
Non-Compensatory Warrants	4,322	3,597
Capitalized research & development expenditures	27,084	23,410
Right Of Use Liability (Operating Leases)	39,237	16,715
Net operating loss carryforwards	64,523	58,364
Total deferred tax asset	169,312	129,874
Valuation allowance	(117,353)	(100,493)
Net deferred tax assets	51,959	29,381
Intangible assets	(15)	(37)
Convertible debt	(7,718)	(9,217)
Right Of Use Liability (Operating Leases)	(40,298)	(18,066)
Other reserves and accruals	(16)	(20)
Property, plant and equipment and right of use assets	(3,912)	(2,041)
Deferred tax liability	(51,959)	(29,381)
U.S.
Significant components of the Company's deferred tax assets and liabilities
Deferred revenue	7,898	9,304
Interest expense	11,299	5,239
Other reserves and accruals	699	592
Tax credit carryforwards	2,590	1,865
Amortization of stock-based compensation	9,081	8,442
Non-Compensatory Warrants	4,322	3,597
Capitalized research & development expenditures	22,601	19,116
Right Of Use Liability (Operating Leases)	39,237	16,715
Net operating loss carryforwards	54,947	49,058
Total deferred tax asset	152,674	113,928
Valuation allowance	(100,731)	(84,567)
Net deferred tax assets	51,943	29,361
Intangible assets	(15)	(37)
Convertible debt	(7,718)	(9,217)
Right Of Use Liability (Operating Leases)	(40,298)	(18,066)
Property, plant and equipment and right of use assets	(3,912)	(2,041)
Deferred tax liability	(51,943)	(29,361)
Foreign
Significant components of the Company's deferred tax assets and liabilities
Intangible assets	1,197	1,146
Deferred revenue	129
Tax credit carryforwards	1,253	1,200
Capitalized research & development expenditures	4,483	4,294
Net operating loss carryforwards	9,576	9,306
Total deferred tax asset	16,638	15,946
Valuation allowance	(16,622)	(15,926)
Net deferred tax assets	16	20
Other reserves and accruals	(16)	(20)
Deferred tax liability	$ (16)	$ (20)

Income Taxes - Change In Valuat

Income Taxes - Change In Valuation Allowance (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Change in valuation allowance
Increase in valuation allowance for current year increase in net operating losses	$ 7,622
Increase (decrease) in valuation allowance for current year net increase (decrease) in deferred tax assets other than net operating losses	11,786
Decrease in valuation allowance as a result of foreign currency fluctuation	(2,935)
Increase in valuation allowance due to change in tax rates	387
Net increase in Valuation allowance	16,860
Net decrease (increase) in valuation allowance	16,860	$ 10,735	$ (11,619)
U.S.
Change in valuation allowance
Increase in valuation allowance for current year increase in net operating losses	7,254
Increase (decrease) in valuation allowance for current year net increase (decrease) in deferred tax assets other than net operating losses	11,845
Decrease in valuation allowance as a result of foreign currency fluctuation	(2,935)
Net increase in Valuation allowance	16,164
Net decrease (increase) in valuation allowance	16,164	11,003	(12,167)
Foreign
Change in valuation allowance
Increase in valuation allowance for current year increase in net operating losses	368
Increase (decrease) in valuation allowance for current year net increase (decrease) in deferred tax assets other than net operating losses	(59)
Increase in valuation allowance due to change in tax rates	387
Net increase in Valuation allowance	696
Net decrease (increase) in valuation allowance	$ 696	$ (268)	$ 548

Income Taxes - Unrecognized Tax

Income Taxes - Unrecognized Tax Benefits (Details) - USD ($) $ in Thousands	12 Months Ended
	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	223,100
Deferred tax assets, U.S. net operating loss carryforwards	236,600
Unused net operating loss carryforwards	27,700	$ 42,200
Amount of net operating loss carryforwards that will expire due to IRC Section 382 limitations	2,600
Net operating loss carryforwards	64,523	58,364
Un-repatriated foreign earnings	0
Canada
Income taxes
Research and experimental development expenditure carryforwards	17,200
Canadian ITC credit carryforwards	1,300
U.S.
Income taxes
Net operating loss carryforwards	54,947	49,058
Foreign
Income taxes
Net operating loss carryforwards	9,576	$ 9,306
Foreign | French
Income taxes
Unused net operating loss carryforwards	17,900
Foreign | Canada
Income taxes
Net operating loss carryforwards	$ 14,000

Income Taxes - Tax cuts and job

Income Taxes - Tax cuts and jobs act (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Income Taxes
U.S. Federal statutory tax rate	21.00%	21.00%	35.00%
Write down of deferred tax assets	$ 42.5
Reduction in valuation allowance	$ 42.5
Reduction in tax benefit due to write down of deferred tax assets	33.5
Valuation allowance rate offsetting tax rate reduction	33.50%

Commitments and Contingencies -

Commitments and Contingencies - Operating Leases (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Future minimum lease payments under noncancellable operating leases - As Lessor
2020	$ 31,279
2021	30,316
2022	22,432
2023	18,346
2024 and thereafter	36,095
Total future minimum lease payments	138,468
Future minimum lease payments under noncancelable operating leases - As Lessee
2020	44,849
2021	44,919
2022	40,329
2023	35,738
2024 and thereafter	70,718
Total future minimum lease payments	236,553
Less imputed lease interest	(65,226)
Total lease liabilities	$ 171,327
Operating Lease, Liability, Statement of Financial Position [Extensible List]	plug:FinancingTransactionFinanceObligationAmountCurrent plug:FinancingTransactionFinanceObligationAmount
Rental expense for all operating lease	$ 30,600	$ 15,800
Gross profit on sale leaseback transactions	26,200	16,400
Right of use assets obtained in exchange for new operating lease liabilities	121,400	46,300
Prepaid rent and security deposit	6,000	6,800
Other information of operating leases
Cash payments	$ 29,317	$ 14,926
Weighted average remaining lease term (in years)	5 years 7 months 10 days	4 years 4 months 10 days
Weighted average discount rate (as a percent)	12.10%	12.10%
Minimum
Operating Leases
Lease Term - as Lessor	1 year
Lease Term - as Lessee	1 year
Maximum
Operating Leases
Lease Term - as Lessor	7 years
Lease Term - as Lessee	9 years
Sale Leaseback Agreements
Future minimum lease payments under noncancelable operating leases - As Lessee
Total lease liabilities	$ 109,400	$ 37,000
Short term operating lease obligation	15,500	5,700
Long term operating lease obligation	$ 93,900	$ 31,300

Commitments and Contingencies_2

Commitments and Contingencies - Finance Leases (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Finance lease costs
Right of use assets obtained in exchange for new finance lease liabilities	$ 5,900	$ 2,200
Restricted Cash
Restricted cash	125,100
Letter of credit	103,400
Sale Leaseback Agreements
Total Payments of future minimum lease payments
Total lease liabilities	31,700	81,900
Finance lease costs
Amortization of right of use asset	3,178	7,549
Interest on finance obligations	4,863	6,908
Total finance lease cost	8,041	14,457
Other information
Cash payments	$ 61,237	$ 33,715
Weighted average remaining lease term (years)	2 years 11 months 27 days	3 years 2 months 1 day
Weighted average discount rate	11.10%	11.80%
Finance Lease [Member]
Total Payments of future minimum lease payments
2020	$ 10,128
2021	9,276
2022	4,975
2023	3,150
2024 and thereafter	16,154
Total future minimum lease payments	43,683
Less imputed lease interest	(11,934)
Sale of future services	109,422
Total lease liabilities	141,171
Other Leased Property [Member]
Total Payments of future minimum lease payments
2020	414
2021	407
2022	390
2023	366
2024 and thereafter	1,547
Total future minimum lease payments	3,124
Less imputed lease interest	(887)
Total lease liabilities	2,237
Total Finance Lease [Member]
Total Payments of future minimum lease payments
2020	55,391
2021	54,602
2022	45,694
2023	39,254
2024 and thereafter	88,419
Total future minimum lease payments	283,360
Less imputed lease interest	(78,047)
Sale of future services	109,422
Total lease liabilities	314,735
Finance obligation
Restricted Cash
Letter of credit	500
Finance obligation | Property and equipment
Total Payments of future minimum lease payments
Total future minimum lease payments	$ 2,200

Commitments and Contingencies_3

Commitments and Contingencies - Concentrations of Credit Risk (Details) - customer	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Accounts receivable | Credit risk | Customers
Customer Concentration
Concentration Risk Number of Customers	2	2
Concentration risk (as a percent)	63.40%	52.30%
Revenues | Customer concentration
Customer Concentration
Concentration Risk Number of Customers		2
Concentration risk (as a percent)	49.60%	66.70%

Unaudited Quarterly Financial_3

Unaudited Quarterly Financial Data (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Net revenue:
Net revenue	$ 91,664	$ 59,461	$ 57,535	$ 21,579	$ 59,820	$ 53,165	$ 35,229	$ 26,418
Gross (loss) profit	12,782	8,349	10,619	(3,784)	4,507	4,409	(2,310)	(3,984)	$ 27,966	$ 2,622	$ (28,089)
Operating expenses	20,323	18,428	22,560	16,697	17,426	17,054	20,668	16,957	78,008	72,105	73,703
Operating loss	(7,541)	(10,079)	(11,941)	(20,481)	(12,919)	(12,645)	(22,978)	(20,941)	(50,042)	(69,483)	(101,792)
Net loss attributable to common shareholders	$ (18,288)	$ (18,155)	$ (18,070)	$ (31,004)	$ (16,860)	$ (15,578)	$ (25,881)	$ (19,848)	$ (85,517)	$ (78,167)	$ (130,178)
Loss per share:
Basic and diluted	$ (0.07)	$ (0.08)	$ (0.07)	$ (0.14)	$ (0.08)	$ (0.07)	$ (0.12)	$ (0.09)	$ (0.36)	$ (0.36)	$ (0.60)
Sales of fuel cell systems and related infrastructure
Net revenue:
Net revenue	$ 69,767	$ 38,877	$ 38,696	$ 2,544	$ 41,191	$ 36,668	$ 18,820	$ 10,613	$ 149,884	$ 107,292	$ 62,631
Services performed on fuel cell systems and related infrastructure
Net revenue:
Net revenue	7,328	6,205	5,341	6,343	5,672	5,156	5,691	5,483	25,217	22,002	16,202
Power Purchase Agreements
Net revenue:
Net revenue	6,739	6,595	6,409	6,110	6,504	5,555	5,438	5,372	25,853	22,869	12,869
Fuel delivered to customers
Net revenue:
Net revenue	7,779	7,649	$ 7,089	$ 6,582	$ 6,453	$ 5,786	$ 5,280	$ 4,950	29,099	$ 22,469	8,167
Other
Net revenue:
Net revenue	$ 51	$ 135							$ 186		$ 284