Stem (STEM) 10-K 28 Feb 22 2021 FY Annual report Financial data

Cover

Cover - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2021	Feb. 17, 2022	Jun. 30, 2021
Cover [Abstract]
Document Type	10-K
Document Annual Report	true
Document Period End Date	Dec. 31, 2021
Current Fiscal Year End Date	--12-31
Document Transition Report	false
Entity Registrant Name	STEM, INC.
Entity Incorporation, State or Country Code	DE
Entity File Number	333-251397
Entity Tax Identification Number	85-1972187
Entity Address, Address Line One	100 California St., 14th Fl
Entity Address, City or Town	San Francisco
Entity Address, State or Province	CA
Entity Address, Postal Zip Code	94111
Country Region	1
City Area Code	877
Local Phone Number	374-7836
Title of 12(b) Security	Common Stock, par value $0.0001
Trading Symbol	STEM
Security Exchange Name	NYSE
Entity Well-known Seasoned Issuer	No
Entity Voluntary Filers	No
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Entity Filer Category	Large Accelerated Filer
Entity Small Business	false
Entity Emerging Growth Company	false
ICFR Auditor Attestation Flag	false
Entity Shell Company	false
Entity Public Float			$ 4,998
Entity Common Stock, Shares Outstanding		153,443,756
Documents Incorporated by Reference	Certain information required to be furnished pursuant to Part III of this Form 10-K is set forth in, and is incorporated by reference from, Stem’s definitive proxy statement for its 2022 Annual Meeting of Stockholders, to be filed by Stem with the Securities and Exchange Commission (“SEC”) pursuant to Regulation 14A within 120 days after December 31, 2021 (the “2022 Proxy Statement”).
Entity Central Index Key	0001758766
Document Fiscal Year Focus	2021
Document Fiscal Period Focus	FY
Amendment Flag	false

Audit Information

Audit Information	12 Months Ended
	Dec. 31, 2021
Audit Information [Abstract]
Auditor Firm ID	34
Auditor Name	DELOITTE & TOUCHE LLP
Auditor Location	San Francisco, California

CONSOLIDATED BALANCE SHEETS

CONSOLIDATED BALANCE SHEETS - USD ($) $ in Thousands	Dec. 31, 2021	Dec. 31, 2020
Current assets:
Cash and cash equivalents	$ 747,780	$ 6,942
Short-term investments	173,008	0
Accounts receivable, net	61,701	13,572
Inventory, net	22,720	20,843
Other current assets (includes $213 and $123 due from related parties as of December 31, 2021 and December 31, 2020, respectively)	18,641	7,920
Total current assets	1,023,850	49,277
Energy storage systems, net	106,114	123,703
Contract origination costs, net	8,630	10,404
Goodwill	1,741	1,739
Intangible assets, net	13,966	12,087
Operating leases right-of-use assets	12,998	358
Other noncurrent assets	24,531	8,282
Total assets	1,191,830	205,850
Current liabilities:
Accounts payable	28,273	13,749
Accrued liabilities	25,993	16,072
Accrued payroll	7,453	5,976
Notes payable, current portion	0	33,683
Convertible promissory notes (includes $0 and $45,271 due to related parties as of December 31, 2021 and December 31, 2020, respectively)	0	67,590
Financing obligation, current portion	15,277	14,914
Deferred revenue, current portion	9,158	36,942
Other current liabilities (includes $306 and $399 due to related parties as of December 31, 2021 and December 31, 2020, respectively)	1,813	1,589
Total current liabilities	87,967	190,515
Deferred revenue, noncurrent	28,285	15,468
Asset retirement obligation	4,135	4,137
Notes payable, noncurrent	1,687	4,612
Convertible notes, noncurrent	316,542	0
Financing obligation, noncurrent	73,204	73,128
Warrant liabilities	0	95,342
Lease liability, noncurrent	12,183	57
Total liabilities	524,003	383,259
Commitments and contingencies
Stockholders’ equity (deficit):
Preferred stock, $0.0001 par value; 1,000,000 shares authorized as of December 31, 2021 and December 31, 2020, respectively; 0 shares issued and outstanding as of December 31, 2021 and December 31, 2020, respectively	0	0
Common stock, $0.0001 par value; 500,000,000 shares authorized as of December 31, 2021 and December 31, 2020; 144,671,624 and 40,202,785 issued and outstanding as of December 31, 2021 and December 31, 2020, respectively	14	4
Additional paid-in capital	1,176,845	230,620
Accumulated other comprehensive income (loss)	20	(192)
Accumulated deficit	(509,052)	(407,841)
Total stockholders’ equity (deficit)	667,827	(177,409)
Total liabilities and stockholders’ equity (deficit)	$ 1,191,830	$ 205,850

CONSOLIDATED BALANCE SHEETS (Pa

CONSOLIDATED BALANCE SHEETS (Parenthetical) - USD ($) $ in Thousands	Dec. 31, 2021	Dec. 31, 2020
Statement of Financial Position [Abstract]
Due from related parties	$ 213	$ 123
Convertible promissory notes, due to related parties	0	45,271
Other current liabilities, due to related parties	$ 306	$ 399
Preferred stock, par value (in dollars per share)	$ 0.0001	$ 0.0001
Preferred stock, shares authorized (in shares)	1,000,000	1,000,000
Preferred stock, shares issued (in shares)	0	0
Preferred stock, shares outstanding (in shares)	0	0
Common stock, par value (in dollars per share)	$ 0.0001	$ 0.0001
Common stock, shares authorized (in shares)	500,000,000	500,000,000
Common stock, shares issued (in shares)	144,671,624	40,202,785
Common stock, shares outstanding (in shares)	144,671,624	40,202,785

CONSOLIDATED STATEMENTS OF OPER

CONSOLIDATED STATEMENTS OF OPERATIONS - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Total revenue	$ 127,371	$ 36,307	$ 17,552
Cost of revenue	126,124	40,219	20,812
Gross margin	1,247	(3,912)	(3,260)
Operating expenses:
Sales and marketing	19,950	14,829	17,462
Research and development	22,723	15,941	14,703
General and administrative	41,648	14,705	12,425
Total operating expenses	84,321	45,475	44,590
Loss from operations	(83,074)	(49,387)	(47,850)
Other income (expense), net:
Interest expense	(17,395)	(20,806)	(12,548)
Loss on extinguishment of debt	(5,064)	0	0
Change in fair value of warrants and embedded derivative	3,424	(84,455)	1,493
Other income (expenses), net	898	(1,471)	(503)
Total other income (expense)	(18,137)	(106,732)	(11,558)
Income (loss) before income taxes	(101,211)	(156,119)	(59,408)
Income tax expense	0	(5)	(6)
Net loss	$ (101,211)	$ (156,124)	$ (59,414)
Net loss per share attributable to common shareholders, basic (in dollars per share)	$ (0.96)	$ (4.13)	$ (1.51)
Net loss per share attributable to common shareholders, diluted (in dollars per share)	$ (0.96)	$ (4.13)	$ (1.51)
Weighted-average shares used in computing net loss per share, basic (in shares)	105,561,139	40,064,087	42,811,383
Weighted-average shares used in computing net loss per share, diluted (in shares)	105,561,139	40,064,087	42,811,383
Service revenue
Total revenue	$ 20,463	$ 15,645	$ 13,482
Cost of revenue	28,177	21,187	16,958
Hardware revenue
Total revenue	106,908	20,662	4,070
Cost of revenue	$ 97,947	$ 19,032	$ 3,854

CONSOLIDATED STATEMENTS OF COMP

CONSOLIDATED STATEMENTS OF COMPREHENSIVE LOSS - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Statement of Comprehensive Income [Abstract]
Net loss	$ (101,211)	$ (156,124)	$ (59,414)
Other comprehensive income (loss):
Unrealized loss on available-for-sale securities	(175)	0	0
Foreign currency translation adjustment	387	(246)	54
Total comprehensive income (loss)	$ (100,999)	$ (156,370)	$ (59,360)

CONSOLIDATED STATEMENTS OF STOC

CONSOLIDATED STATEMENTS OF STOCKHOLDERS’EQUITY (DEFICIT) - USD ($) $ in Thousands	Total	Convertible Notes	Warrant	Previously Reported	Retroactive application of recapitalization	Series 1 Convertible Preferred Stock	Series 1 Convertible Preferred StockPreviously Reported	Series 1 Convertible Preferred StockRetroactive application of recapitalization	Common Stock	Common StockConvertible Notes	Common StockWarrant	Common StockPreviously Reported	Common StockRetroactive application of recapitalization	Additional Paid-In Capital	Additional Paid-In CapitalConvertible Notes	Additional Paid-In CapitalWarrant	Additional Paid-In CapitalPreviously Reported	Additional Paid-In CapitalRetroactive application of recapitalization	Accumulated Other Comprehensive Income (Loss)	Accumulated Other Comprehensive Income (Loss)Previously Reported	Accumulated Other Comprehensive Income (Loss)Retroactive application of recapitalization	Accumulated Deficit	Accumulated DeficitPreviously Reported	Accumulated DeficitRetroactive application of recapitalization
Beginning balance (in shares) at Dec. 31, 2018	0			186,466,181	(186,466,181)
Beginning balance at Dec. 31, 2018	$ 0			$ 218,931	$ (218,931)
Ending balance (in shares) at Dec. 31, 2019	0
Ending balance at Dec. 31, 2019	$ 0
Beginning balance (in shares) at Dec. 31, 2018						0	3,405	(3,405)	42,223,732			9,583,163	32,640,569
Beginning balance at Dec. 31, 2018	8,890			$ (210,041)	$ 218,931	$ 0	$ 0	$ 0	$ 3			$ 0	$ 3	$ 219,483			$ 555	$ 218,928	$ 0	$ 0	$ 0	$ (210,596)	$ (210,596)	$ 0
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Effect of exchange transaction (in shares)									(3,368,264)
Effect of exchange transaction	(4,990)													(15,946)								10,956
Issuance of warrants to purchase common stock	1,217													1,217
Issuance of shares upon conversion of promissory note (in shares)									4,245,330
Issuance of shares upon conversion of promissory note	28,144													28,144
Settlement of litigation (in shares)									(2,905)
Issuance of shares upon exercise of stock options and warrants (in shares)									91,302
Issuance of common stock upon exercise of stock options and warrants	36													36
Stock-based compensation	1,531													1,531
Unrealized loss on available-for-sale securities	0
Foreign currency translation adjustment	54																		54
Net loss	(59,414)																					(59,414)
Ending balance (in shares) at Dec. 31, 2019						0			43,189,195
Ending balance at Dec. 31, 2019	(24,532)					$ 0			$ 3					234,465					54			(259,054)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Effect of exchange transaction (in shares)									(3,448,648)
Effect of exchange transaction	(3,268)													(10,605)								7,337
Cancellation of exchange transaction by shareholder (in shares)									184,520
Recognition of beneficial conversion feature related to convertible notes	1,629													1,629
Issuance of warrants to purchase common stock	168													168
Issuance of shares upon exercise of stock options and warrants (in shares)									277,718
Issuance of common stock upon exercise of stock options and warrants	422								$ 1					421
Stock-based compensation	4,542													4,542
Unrealized loss on available-for-sale securities	0
Foreign currency translation adjustment	(246)																		(246)
Net loss	(156,124)																					(156,124)
Ending balance (in shares) at Dec. 31, 2020						0			40,202,785
Ending balance at Dec. 31, 2020	(177,409)					$ 0			$ 4					230,620					(192)			(407,841)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Merger and PIPE financing (in shares)									70,428,326
Merger and PIPE financing	248,144								$ 7					248,137
Conversion of securities into common stock (in shares)										10,921,548	2,759,970
Conversion of securities into common stock		$ 77,748	$ 60,568							$ 1					$ 77,747	$ 60,568
Exchange of warrants into common stock (in shares)									4,683,349
Exchange of warrants into common stock	168,647								$ 1					168,646
Issuance of common stock warrants for services	9,183													9,183
Public Warrant exercises (in shares)									12,638,723
Public Warrant exercises	312,116								$ 1					312,115
Issuance of 2028 Convertible Notes, net	130,979													130,979
Purchase of capped call options	$ (66,700)													(66,700)
Stock option exercises, net of statutory tax withholdings (in shares)	3,235,713								2,667,384
Stock option exercises, net of statutory tax withholdings	$ (9,574)													(9,574)
Legacy stock warrant exercises (in shares)									369,539
Legacy stock warrant exercises	418													418
Stock-based compensation	14,706													14,706
Unrealized loss on available-for-sale securities	(175)																		(175)
Foreign currency translation adjustment	387																		387
Net loss	(101,211)																					(101,211)
Ending balance (in shares) at Dec. 31, 2021						0			144,671,624
Ending balance at Dec. 31, 2021	$ 667,827					$ 0			$ 14					$ 1,176,845					$ 20			$ (509,052)

CONSOLIDATED STATEMENTS OF CASH

CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
OPERATING ACTIVITIES
Net loss	$ (101,211)	$ (156,124)	$ (59,414)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation and amortization expense	24,473	17,736	13,889
Non-cash interest expense, including interest expenses associated with debt issuance costs	9,648	10,044	4,759
Stock-based compensation	13,546	4,542	1,531
Change in fair value of warrant liability and embedded derivative	(3,424)	84,455	(1,493)
Noncash lease expense	896	589	906
Accretion expense	229	217	303
Impairment of energy storage systems	4,320	1,395	295
Issuance of warrants for services	9,183	0	0
Net (accretion of discount) amortization of premium on investments	664	0	0
Other	(50)	(129)	(76)
Changes in operating assets and liabilities:
Accounts receivable	(48,125)	(6,988)	(5,112)
Inventory	(1,877)	(17,263)	(1,553)
Other assets	(24,783)	(5,329)	(1,860)
Right-of-use assets	(199)	0	0
Contract origination costs, net	(2,622)	(2,552)	(1,302)
Accounts payable and accrued expenses	33,462	5,684	10,562
Deferred revenue	(14,967)	31,682	9,007
Lease liabilities	(303)	(646)	(230)
Other liabilities	(126)	(984)	110
Net cash used in operating activities	(101,266)	(33,671)	(29,678)
INVESTING ACTIVITIES
Purchase of available-for-sale investments	(189,858)	0	0
Sale of available-for-sale investments	16,011	0	0
Purchase of energy storage systems	(3,604)	(6,196)	(40,995)
Capital expenditures on internally-developed software	(5,970)	(5,828)	(5,356)
Purchase of equity method investment	(1,212)	0	0
Purchase of property and equipment	(600)	(12)	(7)
Net cash used in investing activities	(185,233)	(12,036)	(46,358)
FINANCING ACTIVITIES
Proceeds from exercise of stock options and warrants	148,532	422	36
Payments for taxes related to net share settlement of stock options	(12,622)	0	0
Net contributions from Merger and PIPE financing, net of transaction costs of $58,061	550,322	0	0
Proceeds from financing obligations	7,839	16,222	32,310
Repayment of financing obligations	(9,587)	(10,689)	(7,309)
Proceeds from issuance of convertible notes, net of issuance costs of $14,299, $240 and $2,308 for the years ended December 31, 2021, 2020 and 2019, respectively	446,827	33,081	63,250
Purchase of capped call options	(66,700)	0	0
Proceeds from issuance of notes payable, net of issuance costs of $0, $1,502 and $0 for the years December 31, 2021, 2020 and 2019, respectively	3,930	23,498	4,710
Repayment of notes payable	(41,446)	(22,240)	(25,796)
Net cash provided by financing activities	1,027,095	40,294	67,201
Effect of exchange rate changes on cash and cash equivalents	242	(534)	(170)
Net increase (decrease) in cash and cash equivalents	740,838	(5,947)	(9,005)
Cash and cash equivalents, beginning of period	6,942	12,889	21,894
Cash and cash equivalents, end of period	747,780	6,942	12,889
SUPPLEMENTAL DISCLOSURE OF CASH FLOW INFORMATION
Cash paid for interest	10,188	9,665	8,937
Cash paid for income taxes	0	2	3
NON-CASH INVESTING AND FINANCING ACTIVITIES
Change in asset retirement costs and asset retirement obligation	231	1,839	(636)
Exchange of warrants for common stock	168,647	0	0
Conversion of warrants upon Merger	60,568	0	0
Conversion of convertible notes upon Merger	77,748	0	0
Conversion of accrued interest into outstanding note payable	337	644	0
Right-of-use asset obtained in exchange for lease liability	13,337	0	0
Settlement of warrant liability into common stock due to exercise	167,050	0	0
Settlement of warrant liability into common stock due to redemption	2,121	0	0
Issuance of common stock warrants	0	168	1,216
Stock-based compensation capitalized to internal-use software	1,160	0	0
Purchase of energy storage systems in accounts payable	0	1,806	950
Conversion of convertible promissory notes and accrued interest into Series D preferred stock	$ 0	$ 0	$ 28,144

CONSOLIDATED STATEMENTS OF CA_2

CONSOLIDATED STATEMENTS OF CASH FLOWS (Parenthetical) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Transaction costs	$ 58,061
Noncash lease expense	896	$ 589	$ 906
Convertible Notes
Payment of debt issuance costs	14,299	240	2,308
Notes Payable
Payment of debt issuance costs	$ 0	$ 1,502	$ 0

BUSINESS

BUSINESS	12 Months Ended
	Dec. 31, 2021
Organization, Consolidation and Presentation of Financial Statements [Abstract]
BUSINESS	BUSINESS Description of the Business Stem, Inc. and its subsidiaries (together, “Stem” or the “Company”) is one of the largest digitally connected, intelligent energy storage networks, providing customers (i) with an energy storage system, sourced from leading, global battery original equipment manufacturers (“OEMs”), that the Company delivers through its partners, including solar project developers and engineering, procurement and construction firms and (ii) through its Athena® artificial intelligence (“AI”) platform (“Athena”), with ongoing software-enabled services to operate the energy storage systems for up to 20 years. In addition, in all the markets where the Company operates its customers’ systems, the Company has agreements to manage the energy storage systems using the Athena platform to participate in energy markets and to share the revenue from such market participation. The Company delivers its battery hardware and software-enabled services through its Athena platform to its customers. The Company’s hardware and recurring software-enabled services mitigate customer energy costs through services such as time-of-use and demand charge management optimization and by aggregating the dispatch of energy through a network of virtual power plants. The resulting network created by the Company’s growing customer base increases grid resilience and reliability through the real-time processing of market-based demand cycles, energy prices and other factors in connection with the deployment of renewable energy resources to such customers. Additionally, the Company’s energy storage solutions support renewable energy generation by alleviating grid intermittency issues and thereby reducing customer dependence on traditional, fossil fuel resources. The Company operated as Rollins Road Acquisition Company (f/k/a Stem, Inc.) (“Legacy Stem”) prior to the Merger (as defined below). Stem, Inc. was incorporated on March 16, 2009 in the State of Delaware and is headquartered in San Francisco, California. Star Peak Acquisition Corp. Merger On December 3, 2020, the Company entered into an Agreement and Plan of Merger (the “Merger Agreement”) with Star Peak Transition Corp. (“STPK”), an entity listed on the New York Stock Exchange under the trade symbol “STPK”, and STPK Merger Sub Corp., a Delaware corporation and wholly-owned subsidiary of STPK (“Merger Sub”), providing for, among other things, and subject to the conditions therein, the combination of the Company and STPK pursuant to the merger of Merger Sub with and into the Company with the Company continuing as the surviving entity (the “Merger”). On April 28, 2021, shareholders of STPK approved the Merger, under which Stem received approximately $550.3 million, net of fees and expenses as follows (in thousands): Recapitalization Cash — STPK trust and working capital cash $ 383,383 Cash — PIPE (as described below) 225,000 Less: transaction costs and advisory fees paid (58,061) Merger and PIPE financing $ 550,322 Immediately prior to the closing of the Merger, (i) all issued and outstanding shares of Legacy Stem preferred stock, par value $0.00001 per share (the “Legacy Stem Preferred Stock”), were converted into shares of Legacy Stem common stock, par value $0.000001 per share (the “Legacy Stem Common Stock”) in accordance with Legacy Stem’s amended and restated certificate of incorporation, (ii) all outstanding convertible promissory notes of Legacy Stem (the “Legacy Stem Convertible Notes”) were converted into Legacy Stem Preferred Stock in accordance with the terms of the Legacy Stem Convertible Notes and (iii) certain warrants issued by Legacy Stem to purchase Legacy Stem Common Stock and Legacy Stem Preferred Stock (the “Legacy Stem Warrants”) were exercised by holders into Legacy Stem Common Stock in accordance with the terms thereof. Upon the consummation of the Merger, each share of Legacy Stem common stock then issued and outstanding was canceled and converted into the right to receive shares of common stock of Stem using an exchange ratio of 4.6432. In connection with the execution of the Merger Agreement, STPK entered into separate subscription agreements (each, a “Subscription Agreement”) with a number of investors (each a “Subscriber”), pursuant to which the Subscribers agreed to purchase, and STPK agreed to sell to the Subscribers, an aggregate of 22,500,000 shares of common stock (the “PIPE Shares”), for a purchase price of $10 per share and an aggregate purchase price of $225.0 million, in a private placement pursuant to the subscription agreements (the “PIPE”). The PIPE investment closed simultaneously with the consummation of the Merger. The Merger is accounted for as a reverse recapitalization in accordance with U.S. generally accepted accounting principles (“GAAP”). Under this method of accounting, STPK was treated as the “acquired” company for financial reporting purposes. Accordingly, for accounting purposes, the Merger was treated as the equivalent of Stem issuing stock for the net assets of STPK, accompanied by a recapitalization. The net liabilities of STPK of $302.2 million, comprised primarily of the warrant liabilities associated with the Public and Private Placement Warrants discussed in Note 13 - Warrants , are stated at historical cost, with no goodwill or other intangible assets recorded. Liquidity The accompanying consolidated financial statements have been prepared in accordance with GAAP and with the instructions to Form 10-K and Regulation S-X, assuming the Company will continue as a going concern. As of December 31, 2021, the Company had cash and cash equivalents of $747.8 million, short-term investments of $173.0 million, an accumulated deficit of $509.1 million and net working capital of $935.9 million, with $15.3 million of financing obligation coming due within the next 12 months. During the year ended December 31, 2021, the Company incurred a net loss of $101.2 million and had negative cash flows from operating activities of $101.3 million. However, the net proceeds from the Merger of $550.3 million, the proceeds of $145.3 million from the exercise of Public Warrants (as described in Note 13 - Warrants ), and the net proceeds of $445.7 million from the issuance of the Company’s 0.50% Green Convertible Senior Notes due 2028 (the “2028 Convertible Notes”) (as described in Note 12 - Convertible Promissory Notes ) provided the Company with a significant amount of cash proceeds. As discussed in Note 21 - Subsequent Events , the Company completed the acquisition of 100% of the outstanding shares of AlsoEnergy, Inc., (“AlsoEnergy”) for an aggregate purchase price of $695.0 million, consisting of approximately 75% in cash. The Company believes that its cash position is sufficient to meet capital and liquidity requirements for at least the next 12 months after the date that the financial statements are available to be issued. The Company’s business prospects are subject to risks, expenses, and uncertainties frequently encountered by companies in the early stages of commercial operations. Prior to the Merger, the Company had been funded primarily by equity financings, convertible promissory notes and borrowings from affiliates. The attainment of profitable operations is dependent upon future events, including obtaining adequate financing to complete the Company’s development activities, securing adequate supplier relationships, building its customer base, successfully executing its business and marketing strategy, and hiring and retaining appropriate personnel. Failure to generate sufficient revenues, achieve planned gross margins and operating profitability, control operating costs, or secure additional funding may require the Company to modify, delay or abandon some of its planned future expansion or development, or to otherwise enact operating cost reductions available to management, which could have a material adverse effect on the Company’s business, operating results and financial condition. COVID-19 The ongoing COVID-19 pandemic has resulted and may continue to result in widespread adverse impacts on the global and U.S. economies. Ongoing g overnment and business responses to COVID-19, along with the COVID-19 Omicron variant and resurgence of related disruptions, could have a continued material adverse effect on economic and market conditions and trigger a period of continued global and U.S. economic slowdown. The Company’s industry is currently facing shortages and shipping delays affecting the supply of energy storage systems, batteries, modules and component parts for inverters and battery energy storage systems available for purchase. These shortages and delays can be attributed in part to the COVID-19 pandemic and resulting government action. While a majority of the Company’s suppliers have secured sufficient quantities to permit them to continue delivery and installing through the end of 2022, if these shortages and delays persist into 2023, they could adversely affect the timing of when energy storage systems can be delivered and installed and when the Company can begin to generate revenue from those systems. The Company cannot predict the full effect the COVID-19 pandemic will have on its business, cash flows, liquidity, financial condition and results of operations at this time due to numerous uncertainties. The Company will continue to monitor developments affecting its workforce, its customers and its business operations generally, and will take actions it determines are necessary in order to mitigate these effects.

SUMMARY OF SIGNIFICANT ACCOUNTI

SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES	12 Months Ended
	Dec. 31, 2021
Accounting Policies [Abstract]
SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES	SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES Basis of Presentation The Company's consolidated financial statements have been prepared in accordance with GAAP. Immaterial Out-of-Period Corrections During the year ended December 31, 2021, the Company recorded certain out-of-period corrections related to prior interim and annual periods pertaining to the amortization of contract origination costs and valuation of energy storage systems that were decommissioned. The impact of out-of-period corrections to the year ended December 31, 2021 was an increase of $2.8 million to net loss, and increase to cost of service revenue of $1.7 million, and an increase to sales and marketing expenses of $1.1 million. The following table presents the amount of the errors identified for energy storage systems, net and contract origination costs, net as of the end of each period, and the amounts and periods in which the errors related to cost of service revenue and sales and marketing originated (in millions): (overstatement)/understatement Year Ended December 31, 2020 2019 Periods prior to 2019 Energy storage systems, net $ (1.7) $ (1.5) $ (0.9) Contract origination costs, net $ (1.1) $ (0.3) $ (0.1) Cost of service revenue $ 0.2 $ 0.6 $ 0.9 Sales and marketing $ 0.8 $ 0.2 $ 0.1 The Company corrected the out of period errors in the quarter ended December 31, 2021. The impact of the out-of-period correction for the quarter ended December 31, 2021 included corrections for the prior quarterly periods presented below. The impact to the quarter ended December 31, 2021, was an increase of $4.2 million to net loss, increase to cost of service revenue of $1.8 million and increase to sales and marketing expenses of $2.4 million. The following table presents the amounts of the errors identified for energy storage systems, net and contract origination costs, net as of the end of each period, as well as the quarterly periods in which the errors related to cost of service revenue and sales and marketing originated (in millions): (overstatement)/understatement Quarter ended September 30, 2021 Quarter ended June 30, 2021 Quarter ended March 31, 2021 Energy storage systems, net $ (1.8) $ (1.7) $ (1.7) Contract origination costs, net $ (2.4) $ (1.6) $ (1.4) Cost of service revenue $ 0.1 $ — $ — Sales and marketing $ 0.8 $ 0.2 $ 0.3 The errors and out of period corrections had no impact to the Company’s net cash used in operating activities for any of the periods presented. The Company performed a quantitative and qualitative evaluation of these out-of-period adjustments and has concluded that the amounts are not material in relation to the year ended December 31, 2021, or any prior interim or annual periods. Reclassifications Certain prior year amounts have been reclassified for consistency with the current year presentation. Such reclassifications have no impact on previously reported net loss, stockholders' equity (deficit), or cash flows. Principles of Consolidation The consolidated financial statements include the accounts of the Company, its wholly-owned subsidiaries, and consolidated variable interest entities (“VIEs”). All intercompany balances and transactions have been eliminated in consolidation. Variable Interest Entities The Company forms special purpose entities (“SPEs”), some of which are VIEs, with its investors in the ordinary course of business to facilitate the funding and monetization of its energy storage systems. A legal entity is considered a VIE if it has either a total equity investment that is insufficient to finance its operations without additional subordinated financial support or whose equity holders lack the characteristics of a controlling financial interest. The Company’s variable interests arise from contractual, ownership, or other monetary interests in the entity. The typical condition for a controlling financial interest ownership is holding a majority of the voting interests of an entity; however, a controlling financial interest may also exist in entities, such as VIEs, through arrangements that do not involve controlling voting interests. The Company consolidates a VIE if it is deemed to be the primary beneficiary. The Company determines it is the primary beneficiary if it has the power to direct the activities that most significantly impact the VIEs’ economic performance and has the obligation to absorb losses or has the right to receive benefits of the VIE that could potentially be significant to the VIE. The Company evaluates its relationships with its VIEs on an ongoing basis to determine whether it is the primary beneficiary. Equity Method Investments The Company has ownership interests in SPEs which it does not control. Where the Company holds an interest in these SPEs of greater than 20% and has the ability to exercise significant influence, the Company uses the equity method to account for its investments in these SPEs. Under the equity method of accounting, investments are stated at initial cost and are adjusted for subsequent additional investments and the Company’s proportionate share of earnings or losses and distributions. Such proportionate share of earnings or losses is included within other expenses, net in the consolidated statements of operations. The Company considers whether its equity method investments are impaired when events or circumstances suggest that the carrying amount may not be recoverable. An impairment charge is recognized in the consolidated statements of operations for a decline in value that is determined to be other-than-temporary. In determining if and when a decline in the fair value of these investments below their carrying value is other-than-temporary, the Company evaluates the market condition, trends of earnings and cash flows and other key measures of performance and recognizes such loss which is deemed to be other-than-temporary. No such losses have been recognized during the years ended December 31, 2021, 2020, and 2019. Use of Estimates The preparation of consolidated financial statements in conformity with GAAP requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities, the 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. The Company bases its estimates on historical experience and on various other assumptions believed to be reasonable. Actual results could differ from those estimates and such differences could be material to the financial position and results of operations. Significant estimates and assumptions reflected in these consolidated financial statements include, but are not limited to, depreciable life of energy systems; the amortization of financing obligations; deferred commissions and contract fulfillment costs; the valuation of energy storage systems, internally developed software, and asset retirement obligations; and the fair value of financial instruments, equity-based instruments, debt, warrant liabilities and embedded derivatives. Segment Information Operating segments are defined as components of an entity for which discrete financial information is available that is regularly reviewed by the Chief Operating Decision Maker (“CODM”) in deciding how to allocate resources to an individual segment and in assessing performance. The Company’s Chief Executive Officer is the CODM. The CODM reviews financial information presented on a consolidated basis for purposes of making operating decisions, allocating resources, and evaluating financial performance. As such, management has determined that the Company operates as one operating segment that is focused exclusively on innovative technology services that transform the way energy is distributed and consumed. Net assets outside of the U.S. were less than 10% of total net assets as of December 31, 2021 and 2020. Cash and Cash Equivalents The Company considers all highly liquid investments with an original maturity date of three months or less at the date of purchase to be cash equivalents. Cash and cash equivalents are maintained at financial institutions. The Company maintains all cash in a highly liquid form to meet current obligations. Short-Term Investments Investments with a maturity date greater than three months that the Company intends to convert to cash or cash equivalents within a year or less are classified as short-term investments in the Company’s consolidated balance sheets. Additionally, in accordance with ASC 320, Investments - Debt Securities , the Company has classified all short-term investments as available-for-sale securities and changes in fair market value are reported in other comprehensive income (loss). The Company utilizes its short-term investments as an alternative form of cash and, if the cash needs arise, could liquidate the investments at any point in time regardless of the contractual maturity of the investments. All of the Company’s investments are tradable on an active market and could be sold at fair value at any point in time. Accounts Receivable, Net Accounts receivable are recorded at the invoiced amount, net of allowance for doubtful accounts. Accounts receivable also include unbilled accounts receivable, which is composed of the monthly energy optimization services provided and recognized but not yet invoiced as of the end of the reporting period. The allowance for doubtful accounts is based on the Company’s best estimate and is determined based upon a variety of factors, including analyses of specific customer receivables, aging, and overall assessments of collectability. Accounts receivable balances are charged against the allowance when the Company believes it is probable that the receivable will not be recovered. The allowance for doubtful accounts balance was $0.1 million as of each December 31, 2021 and 2020. Concentrations of Credit Risk and Other Uncertainties Financial instruments that potentially subject the Company to concentration of credit risk consist of cash and cash equivalents and accounts receivable. The Company’s cash balances are primarily invested in money market funds or on deposit at high credit quality financial institutions in the U.S. The Company’s cash and cash equivalents are held at financial institutions where account balances may at times exceed federally insured limits. Management believes the Company is not exposed to significant credit risk due to the financial strength of the depository institution in which the cash is held. The Company has no financial instruments with off-balance sheet risk of loss. At times, the Company may be subject to a concentration of credit risk in relation to certain customers due to the purchase of large energy storage systems made by such customers. The Company routinely assesses the creditworthiness of its customers. The Company has not experienced any material losses related to receivables from individual customers, or groups of customers during the years ended December 31, 2021, 2020 and 2019. The Company does not require collateral. Due to these factors, no additional credit risk beyond amounts provided for collection losses is believed by management to be probable in the Company’s accounts receivable. Significant Customers A significant customer represents 10% or more of the Company’s total revenue or accounts receivable, net balance at each reporting date. For each significant customer, revenue as a percentage of total revenue and accounts receivable as a percentage of total accounts receivable are as follows: Accounts Receivable Revenue December 31, Year Ended December 31, 2021 2020 2021 2020 2019 Customers: Customer A 23 % * 11 % * * Customer B 15 % * 10 % 12 % * Customer C 13 % 17 % 10 % 25 % * Customer D * 30 % * * * Customer E * 20 % * * * *Total less than 10% for the respective period Inventory Inventory consists of batteries and related components either in-process at the Company’s OEM suppliers or as a finished product at the Company’s warehouse, which are sold and delivered directly to customers under the Company’s partnership arrangements as individual assets or assembled systems. Inventory is stated at lower of cost or net realizable value with cost being determined by the specific identification method. The Company periodically reviews its inventory for potentially slow-moving or obsolete items and writes down specific items in inventory to net realizable value based on its assessment of market conditions. Energy Storage Systems, Net The Company sells energy optimization services to host customers through the use of energy storage systems installed at customer locations. The Company determined that it does not transfer control of these energy storage systems to the customer, which are operated and controlled via the Company’s proprietary cloud-based software (“SaaS”) platform; therefore, these energy storage systems do not qualify as a leased asset. The energy storage systems are stated at cost, less accumulated depreciation and impairment (as applicable). Energy storage systems, net is comprised of equipment costs, which include components such as batteries, inverters, and other electrical equipment, and associated design, installation, and interconnection costs required to begin providing the energy optimization services to customers. Depreciation of the energy storage systems is a component of cost of revenues within the consolidated statements of operations and is calculated using the straight-line method over the estimated useful lives of the energy storage systems, or 10 years, once the respective energy storage systems have been installed and interconnected to the power grid, the Company has received permission to operate, and the Company has begun to provide energy optimization services to the customer (i.e., energy storage system is live). Repairs and maintenance costs are expensed as incurred. Impairment charges related to energy storage system that were determined to no longer be recoverable totaled $4.3 million, $1.4 million and $0.3 million for the years ended December 31, 2021, 2020, and 2019, respectively. Contract Origination Costs, Net Contract origination costs, net is stated at gross contract origination costs less accumulated amortization. Contract origination costs consists of sales commissions earned by the Company’s sales team, as well as related payroll taxes and other relevant fringe benefits that are direct, incremental, and recoverable costs of obtaining a contract with a customer. As a result, these amounts have been capitalized on the consolidated balance sheets. The Company deferred incremental costs of obtaining a contract of $3.0 million and $2.6 million during the years ended December 31, 2021 and 2020, respectively. Contract origination costs are amortized over the expected period of benefit. The period of benefit is estimated by considering factors such as the timing of fulfillment of performance obligations, historical customer attrition rates, the useful life of the Company’s technology, and the impact of competition in its industry. Amortization of contract costs were $3.9 million, $0.8 million and $0.5 million for the years ended December 31, 2021, 2020, and 2019, respectively, and are included in sales and marketing expense in the accompanying consolidated statements of operations. The Company also recorded $0.5 million, $0.1 million and $0.5 million in impairment losses in sales and marketing expense in the statements of operations related to the contract origination costs that were determined to no longer be recoverable during the years ended December 31, 2021, 2020, and 2019, respectively. Business Combinations The Company accounts for business acquisitions under ASC 805, Business Combinations . The total purchase consideration for an acquisition is measured as the fair value of the assets given, equity instruments issued and liabilities assumed at the acquisition date. Costs that are directly attributable to the acquisition are expensed as incurred. Identifiable assets (including intangible assets), liabilities assumed (including contingent liabilities) and noncontrolling interests in an acquisition are measured initially at their fair values at the acquisition date. The Company recognizes goodwill if the fair value of the total purchase consideration and any noncontrolling interests is in excess of the net fair value of the identifiable assets acquired and the liabilities assumed. The Company recognizes a bargain purchase gain within other income (expense), net, on the consolidated statement of operations if the net fair value of the identifiable assets acquired and the liabilities assumed is in excess of the fair value of the total purchase consideration and any noncontrolling interests. The Company includes the results of operations of the acquired business in the consolidated financial statements beginning on the acquisition date. Intangible Assets Internal-use software The Company capitalizes costs incurred in the development of internal-use software during the application development stage. Costs related to preliminary project activities and post-implementation activities are expensed as incurred. Capitalized internal-use software is amortized on a straight-line basis over the estimated useful life of the software once it is ready for its intended use. The estimated useful life of costs capitalized is generally five years. The Company recorded amortization for internal-use software of $5.0 million, $4.0 million and $3.0 million in cost of revenues in the accompanying consolidated statements of operations for the years ended December 31, 2021, 2020, and 2019, respectively. Finite-lived Intangible Assets Finite-lived intangible assets consist of developed technology acquired in a business combination. Finite-lived intangible assets acquired in business combinations are initially recorded at fair value and subsequently presented net of accumulated amortization. These intangible assets are amortized on a straight-line basis over their estimated useful lives. The Company amortizes its developed technology over five years. These intangible assets were fully amortized as of December 31, 2021. Amortization of these intangible assets was not material for the years ended December 31, 2020 and 2019. Impairment of Long-Lived Assets The Company reviews its long-lived assets, which primarily consist of energy storage systems, right-of- use assets, and finite-lived intangible assets for impairment whenever events or changes in circumstances indicate that the carrying amount of an asset may not be recoverable or that the useful life is shorter than originally estimated. Recoverability of assets is measured by comparing the carrying amount of an asset to future undiscounted net cash flows expected to be generated by the asset over its remaining useful life. If such assets are impaired, the impairment recognized is measured by the amount by which the carrying amount of the assets exceeds the fair value of the assets. If the useful life is shorter than originally estimated, the Company depreciates or amortizes the remaining carrying value over the revised shorter useful life. Assets to be disposed of by sale are reflected at the lower of their carrying amount or fair value less cost to sell. Leases The Company determines if an arrangement is or contains a lease at inception by assessing whether the arrangement contains an identified asset and whether it has the right to control the identified asset. Right-of-use (“ROU”) assets represent the Company’s right to use an underlying asset for the lease term and lease liabilities represent the Company’s obligation to make lease payments arising from the lease. The classification of the Company’s leases as operating or finance leases along with the initial measurement and recognition of the associated ROU assets and lease liabilities is performed at the lease commencement date. The measurement of ROU assets and lease liabilities is based on the present value of future lease payments over the lease term. The ROU asset also includes the effect of any lease payments made prior to or on lease commencement and excludes lease incentives and initial direct costs incurred, as applicable. As the implicit rate in the Company’s leases is generally unknown, the Company uses its incremental borrowing rate based on the information available at the lease commencement date in determining the present value of future lease payments. The Company considers its credit risk, term of the lease, total lease payments and adjusts for the impacts of collateral, as necessary, when calculating its incremental borrowing rates. The lease terms may include options to extend or terminate the lease when it is reasonably certain the Company will exercise any such options. Rent expense for the Company’s operating leases is recognized on a straight-line basis over the lease term. Variable lease payments are recorded as an expense in the period incurred. The Company has elected to not separate lease and non-lease components for any leases within its existing classes of assets and, as a result, accounts for any lease and non-lease components as a single lease component. The Company has also elected to not apply the recognition requirement to any leases within its existing classes of assets with a term of 12 months or less. Convertible Preferred Stock Warrant Liabilities The Company evaluates whether its warrants for shares of convertible redeemable preferred stock are freestanding financial instruments that obligate the Company to redeem the underlying preferred stock at some point in the future and determined that each of its outstanding warrants for preferred stock are liability classified. The warrants are subject to re-measurement at each balance sheet date, and any change in fair value is recognized in the change in fair value of warrants and embedded derivatives in the consolidated statements of operations. As discussed in Note 13 - Warrants , upon effectiveness of the Merger, substantially all of the outstanding convertible preferred stock warrants were converted into shares of common stock of Stem. As such, the associated warrant liability was reclassified to additional paid-in-capital upon the Merger and was no longer an outstanding Level 3 financial instrument as of December 31, 2021. Common Stock Warrants The Company evaluates common stock warrants under ASC 815-40, Derivatives and Hedging—Contracts in Entity’s Own Equity. The Company assesses whether common stock warrants are freestanding financial instruments and whether they meet the criteria to be classified in stockholders’ equity, or classified as a liability. Where common stock warrants do not meet the conditions to be classified in equity, the Company assesses whether they meet the definition of a liability under ASC 815. Common stock warrants that meet the definition of a liability are recognized on the balance sheet at fair value. Subsequent changes in their respective fair values are recognized in the consolidated statement of operations at each reporting date. As indicated in Note 13 - Warrants , a s part of STPK’s initial public offering, the Company issued Public Warrants and Private Warrants, which upon issuance met the criteria for liability classification under ASC 815. Asset Retirement Obligations The Company recognizes a liability for the fair value of asset retirement obligations (“ARO”) associated with its energy storage systems in the period in which there is a legal obligation associated with the retirement of such assets and the amount can be reasonably estimated. The associated asset retirement costs are capitalized as part of the carrying amount of the energy storage systems and depreciated over the asset’s remaining useful life. This liability includes costs related to the removal of its energy storage systems at the conclusion of each respective customer contract. Subsequent to initial measurement, the asset retirement liability is accreted each period and such accretion is recognized as an expense in the consolidated statements of operations. If there are changes in the estimated amount or timing of cash flows, a revision is recorded to both the asset retirement obligation and the asset retirement capitalized cost. Financing Obligations The Company has formed various SPEs to finance the development and construction of its energy storage systems. These SPEs, which are structured as limited liability companies, obtain financing in the form of large upfront payments from outside investors and purchase energy storage systems from the Company under master purchase agreements. The Company accounts for the large upfront payments received from the fund investor as a borrowing by recording the proceeds received as a financing obligation, which will be repaid through host customer payments and incentives received from the utilities that will be received by the investor. The financing obligation is non-recourse once the associated energy storage systems have been placed in-service and the associated customer arrangements have been assigned to the SPE. However, the Company is responsible for any warranties, performance guarantees, accounting, performance reporting, and all other costs associated with the operation of the energy storage systems. Despite such energy storage systems being legally sold to the SPEs, the Company recognizes host customer payments and incentives as revenue during the period as discussed in Note 3 - Revenue . The amounts received by the fund investor from customer payments and incentives are recognized as interest using the effective interest method, and the balance is applied to reduce the financing obligation. The effective interest rate is the interest rate that equates the present value of the cash amounts to be received by a fund investor in relation to the underlying Projects with the present value of the cash amounts paid by the investor to the Company, adjusted for any payments made by the Company. Fair Value of Financial Instruments Assets and liabilities recorded at fair value in the consolidated financial statements are categorized based upon the level of judgment associated with the inputs used to measure their fair value. The fair value of the Company’s financial assets and liabilities reflects management’s estimate of amounts that the Company would have received in connection with the sale of the assets or paid in connection with the transfer of the liabilities in an orderly transaction between market participants at the measurement date. In connection with measuring the fair value of its assets and liabilities, the Company seeks to maximize the use of observable inputs (market data obtained from independent sources) and to minimize the use of unobservable inputs (internal assumptions about how market participants would price assets and liabilities). Hierarchical levels which are directly related to the amount of subjectivity associated with the inputs to the valuation of these assets or liabilities are as follows: Level 1 — Unadjusted quoted prices in active markets for identical assets or liabilities that the Company has the ability to access as of the measurement date. Level 2 — Inputs other than quoted prices included within Level 1 that are directly observable for the asset or liability or indirectly observable through corroboration with observable market data. Level 3 — Unobservable inputs for the asset or liability only used when there is little, if any, market activity for the asset or liability at the measurement date. This hierarchy requires the Company to use observable market data, when available, and to minimize the use of unobservable inputs when determining fair value. Assets and liabilities measured at fair value are classified in their entirety based on the lowest level of input that is significant to their fair value measurement. The Company’s assessment of the significance of a specific input to the fair value measurement in its entirety requires management to make judgments and consider factors specific to the asset or liability. Financial assets and liabilities held by the Company measured at fair value on a recurring basis as of December 31, 2021 and 2020, include cash and cash equivalents, short-term investments, warrant liabilities and embedded derivatives which are bifurcated from the host financial instrument. Revenue Recognition Revenues are recognized when control of the promised goods or services are transferred to the Company’s customers in an amount that reflects the consideration that is expected to be received in exchange for those goods or services. The Company generates all of its revenues from contracts with its customers. The Company recognizes revenue through two types of arrangements with customers, host customer arrangements and partnership arrangements as described below. Host Customer Arrangements Host customer contracts are generally entered into with commercial entities that have traditionally relied on power supplied directly from the grid. Host customer arrangements consist of a promise to provide energy optimization services through the Company’s proprietary SaaS platform coupled with a dedicated energy storage system owned and controlled by the Company throughout the term of the contract. The host customer does not obtain legal title to, or ownership of the dedicated energy storage system at any point in time. The host customer is the end consumer of the energy that directly benefits from the energy optimization services provided by the Company. The term for the Company’s contracts with host customers generally ranges from 5 to 10 years, which may include certain renewal options to extend the initial contract term or certain termination options to reduce the initial contract term. Although the Company installs an energy storage system at the host customer site in order to provide the energy optimization services, the Company directs how and for what purpose the asset is used through the operation of its SaaS platform and, as such, retains control of the energy storage system; therefore, the contract does not contain a lease. The Company determines the various energy optimization services provided throughout the term of the contract, which may include services such as remote monitoring, performance reporting, preventative maintenance and other ancillary services necessary for the safe and reliable operation of the energy storage system, are part of a combined output of energy optimization services and the Company provides a single distinct combined performance obligation representing a series of distinct days of services. The Company determines the transaction price at the outset of the arrangement, primarily based on the contractual payment terms dictated by the contract with the customer. Fees charged to customers for energy optimization services generally consist of recurring fixed monthly payments throughout the term of the contract. In certain arrangements, the transaction price may include incentive payments that are earned by the host customer from utility companies in relation to the services provided by the Company. Under such arrangements, the rights to the incentive payments are assigned by the host customer to the Company. These incentives may be in the form of fixed upfront payments, variable monthly payments, or annual performance-based payments over the first five years of the customer contract term. Incentive payments may be contingent on approval from utility companies or actual future performance of the energy storage system. Substantially all of the Company’s arrangements provide customers the unilateral ability to terminate for convenience prior to the conclusion of the stated contractual term or the contractual term is shorter than the estimated benefit period, which the Company has determined to be 10 years based on the estimated useful life of the underlying energy storage systems and the period over which the customer can benefit from the energy optimization services utilizing such energy storage systems. In these instances, the Company determined that upfront incentive payments received from its customers represent a material right that is, in effect, an advance payment for future energy optimization services to be recognized throughout the estimated benefit period. In contracts where the customer does not have the unilateral ability to terminate for convenience without a penalty during the estimated benefit period, the Company determined the upfront incentive payments do not represent a material righ

REVENUE

REVENUE	12 Months Ended
	Dec. 31, 2021
Revenue from Contract with Customer [Abstract]
REVENUE	REVENUE Disaggregation of Revenue The following table provides information on the disaggregation of revenue as recorded in the consolidated statements of operations (in thousands): Year ended December 31, 2021 2020 2019 Partnership hardware and service revenue $ 107,135 $ 20,713 $ 4,076 Host customer service revenue 20,236 15,594 13,476 Total revenue $ 127,371 $ 36,307 $ 17,552 Remaining Performance Obligations Remaining performance obligations represent contracted revenue that has not been recognized, which includes contract liabilities (deferred revenue) and amounts that will be billed and recognized as revenue in future periods. As of December 31, 2021, the Company had $217.8 million of remaining performance obligations, and the approximate percentages expected to be recognized as revenue in the future are as follows (in thousands, except percentages): Total remaining Percent Expected to be Recognized as Revenue Less than Two to Greater than Service revenue $ 169,758 12 % 50 % 38 % Hardware revenue 48,039 100 % — % — % Total revenue $ 217,797 Contract Balances Deferred revenue primarily includes cash received in advance of revenue recognition related to energy optimization services and incentives. The following table presents the changes in the deferred revenue balance (in thousands): 2021 2020 2019 Beginning balance as of Beginning balance as of January 1, $ 52,410 $ 20,728 $ 11,859 Upfront payments received from customers 89,951 40,481 6,698 Upfront or annual incentive payments received 6,614 8,015 8,240 Revenue recognized related to amounts that were included in beginning balance of deferred revenue (33,585) (9,764) (4,830) Revenue recognized related to deferred revenue generated during the period (77,947) (7,050) (1,239) Ending balance as of Ending balance as of December 31, $ 37,443 $ 52,410 $ 20,728

SHORT-TERM INVESTMENTS

SHORT-TERM INVESTMENTS	12 Months Ended
	Dec. 31, 2021
Investments, Debt and Equity Securities [Abstract]
SHORT-TERM INVESTMENTS	SHORT-TERM INVESTMENTS The following tables summarize the estimated fair value of the Company’s cash equivalents and debt securities and the gross unrealized holding gains and losses as of December 31, 2021 (in thousands): Amortized cost Unrealized gain Unrealized Loss Estimated Fair Value Assets Cash equivalents: Money market fund $ 127,261 $ — $ — $ 127,261 Total cash equivalents $ 127,261 $ — $ — $ 127,261 Debt securities: Corporate debt securities $ 42,174 $ 11 $ (52) $ 42,133 Commercial paper 20,743 — — 20,743 U.S. government bonds 86,265 — (135) 86,130 Certificate of deposits 21,501 6 — 21,507 Other 2,500 — (5) 2,495 Total debt securities $ 173,183 $ 17 $ (192) $ 173,008 Classified as: Cash equivalents $ 127,261 Short-term debt securities 173,008 Long-term debt securities —

FAIR VALUE MEASUREMENTS

FAIR VALUE MEASUREMENTS	12 Months Ended
	Dec. 31, 2021
Fair Value Disclosures [Abstract]
FAIR VALUE MEASUREMENTS	FAIR VALUE MEASUREMENTS Fair value accounting is applied for all financial assets and liabilities that are recognized or disclosed at fair value in the financial statements on a recurring basis. At December 31, 2021 and December 31, 2020, the carrying amount of accounts receivable, other current assets, accounts payable, and accrued and other current liabilities approximated their estimated fair value due to their relatively short maturities. There were no assets or liabilities classified as Level 3 as of December 31, 2021. The following table provides the financial instruments measured at fair value on a recurring basis (in thousands): December 31, 2021 Level 1 Level 2 Level 3 Total Assets Cash equivalents: Money market fund $ 127,261 $ — $ — $ 127,261 Debt securities Corporate debt securities — 42,133 — 42,133 Commercial paper — 20,743 — 20,743 U.S. government bonds — 86,130 — 86,130 Certificate of deposits — 21,507 — 21,507 Other — 2,495 — 2,495 Total financial assets $ 127,261 $ 173,008 $ — $ 300,269 December 31, 2020 Level 1 Level 2 Level 3 Total Assets Cash equivalents: Money market fund $ 67 $ — $ — $ 67 Liabilities Convertible preferred stock warrant liability $ — $ — $ 95,342 $ 95,342 The Company’s money market funds are classified as Level 1 because they are valued using quoted market prices. The Company’s short-term investments consist of available-for-sale securities and are classified as Level 2 because their value is based on valuations using significant inputs derived from or corroborated by observable market data. The convertible preferred stock warrant liabilities are defined as Level 3 in the fair value hierarchy as the valuations are based on significant unobservable inputs, which reflect the Company’s own assumptions incorporated in valuation techniques used to determine fair value; further discussion of these assumptions is set forth below. There were no transfers into or out of Level 3 of the fair value hierarchy during the periods presented. 2028 Convertible Note s In November 2021, the Company issued $460.0 million aggregate principal amount of its 2028 Convertible Notes. Upon issuance, the Company bifurcated the 2028 Convertible Notes for accounting purposes between a liability component and an equity component. The liability component was determined using a binomial lattice model by estimating the fair value of a hypothetical issuance of an identical offering excluding the conversion feature of the 2028 Convertible Notes. The initial carrying amount of the equity component was calculated as the difference between the liability component and the face value of the 2028 Convertible Senior Notes (See Note 12 - Convertible Promissory Notes ). The estimated fair value of the 2028 Convertible Notes, which differs from their carrying value, is influenced by interest rates, the price of the Company’s common stock, the volatility, the expected term, and the prices for the notes observed in the market trading. The estimated fair value of the 2028 Convertible Notes, which are considered Level 2 financial instruments, was $324.8 million at issuance on November 22, 2021, and $447.8 million as of December 31, 2021 . Capped Call Options with respect to the 2028 Senior Notes In connection with the issuance of the 2028 Convertible Notes, the Company entered into the capped call options with certain financial institutions. The capped calls cover 15,730,390 shares of common stock (subject to anti-dilution and certain other adjustments), which is the same number of shares of common stock that initially underlie the 2028 Convertible Notes. The Capped Calls have an initial strike price of approximately $29.2428 per share, which corresponds to the initial conversion price of the 2028 Convertible Notes, and have a cap price of approximately $49.6575 per share (See Note 12 - Convertible Promissory Notes ). The strike price and cap price are subject to anti-dilution adjustments generally similar to those applicable to the 2028 Convertible Notes. These instruments meet certain accounting criteria to be classified in stockholders’ equity (deficit), and are not subsequently remeasured as long as the conditions for equity classification continue to be met. Convertible Preferred Stock Warrant Liabilities As discussed in Note 13 - Warrants , upon effectiveness of the Merger, substantially all of the outstanding convertible preferred stock warrants were converted into shares of common stock of Stem. As such, the associated warrant liability was reclassified to additional paid-in-capital upon the Merger and was no longer an outstanding Level 3 financial instrument as of December 31, 2021. The fair value of the convertible preferred stock warrants as of December 31, 2020 was determined using the Black-Scholes method as well as a discount for lack of marketability. Black-Scholes inputs used to value the warrants are based on information from purchase agreements and within valuation reports prepared by an independent third party for the Company. Inputs include exercise price, selection of guideline public companies, volatility, fair value of common or preferred stock, expected dividend rate and risk-free interest rate. The key assumptions used for the valuation of the preferred stock warrant liabilities upon remeasurement were as follows: Year Ended December 31, 2021 Volatility 65.0 % Risk-free interest rate 0.1 % Expected term (in years) 1.5 Dividend yield — % Discount for lack of marketability 12.3 % The following table presents the changes in the liability for the Company’s warrants during the years ended December 31, 2021 and 2020 (in thousands): December 31, 2021 2020 Balance as of January 1, $ 95,342 $ 6,094 Changes in estimated fair value 488 85,623 Assumption of warrant liability upon Merger 302,556 — Issuance of warrants — 3,633 Conversion of warrants upon Merger (60,568) — Exchange of warrants (168,647) — Exercise of warrants (169,171) (8) Balance as of December 31, $ — $ 95,342

GOODWILL AND INTANGIBLE ASSETS,

GOODWILL AND INTANGIBLE ASSETS, NET	12 Months Ended
	Dec. 31, 2021
Goodwill and Intangible Assets Disclosure [Abstract]
GOODWILL AND INTANGIBLE ASSETS, NET	GOODWILL AND INTANGIBLE ASSETS, NET Goodwill Goodwill consists of the following (in thousands): December 31, 2021 2020 Goodwill $ 1,625 $ 1,625 Effect of foreign currency translation 116 114 Total goodwill $ 1,741 $ 1,739 Intangible Assets, Net Intangible assets, net, consists of the following (in thousands): December 31, 2021 2020 Developed technology $ 500 $ 500 Internally developed software 29,706 22,545 Intangible assets 30,206 23,045 Less: Accumulated amortization (16,276) (10,993) Add: Currency translation adjustment 36 35 Total intangible assets, net $ 13,966 $ 12,087 Amortization expense for intangible assets was $5.3 million, $4.5 million and $3.1 million for the years ended December 31, 2021, 2020, and 2019, respectively, of which substantially all represents amortization of internally developed software recognized in cost of goods sold in the consolidated statements of operations.

LEASES

LEASES	12 Months Ended
	Dec. 31, 2021
Leases [Abstract]
LEASES	LEASES The Company leases and subleases certain office spaces with lease terms ranging from 3 to 8 years. These leases require monthly lease payments that may be subject to annual increases throughout the lease term. Certain of these leases also include renewal options at the election of the Company to renew or extend the lease for an additional five years. These optional periods have not been considered in the determination of the ROU assets or lease liabilities associated with these leases as the Company did not consider the exercise of these options to be reasonably certain. The Company performed evaluations of its contracts and determined each of its identified leases are operating leases. For the years ended December 31, 2021, 2020, and 2019, the Company incurred $1.3 million, $0.8 million and $1.2 million, respectively, of rent expense included in operating expenses in the consolidated statements of operations in relation to its operating leases, inclusive of short-term and variable lease expense which was immaterial. Cash paid for amounts included in the measurement of operating lease liabilities for the years ended December 31, 2021, 2020, and 2019 was $0.5 million $0.7 million and $0.9 million, respectively, and was included in net cash used in operating activities in the Company’s consolidated statements of cash flows. As of December 31, 2021, future payments associated with the Company’s operating lease liabilities were as follows (in thousands): Operating Leases 2022 $ 1,818 2023 2,473 2024 2,239 2025 2,109 2026 2,172 Thereafter 4,937 Total lease payments 15,748 Less: imputed interest (2,325) Total operating lease liability future lease payments $ 13,423 Reported as of December 31, 2021 and 2020 (in thousands): December 31, 2021 2020 Current portion of operating lease liabilities included within other current liabilities $ 1,240 $ 333 Non-current portion of operating lease liabilities 12,183 57 Total $ 13,423 $ 390 The following summarizes additional information related to operating leases: December 31, 2021 2020 Weighted average remaining operating lease term (in years) 6.7 0.8 Weighted average discount rate 4.5 % 11.3 %

ASSET RETIREMENT OBLIGATION

ASSET RETIREMENT OBLIGATION	12 Months Ended
	Dec. 31, 2021
Asset Retirement Obligation Disclosure [Abstract]
ASSET RETIREMENT OBLIGATION	ASSET RETIREMENT OBLIGATION The information below details the asset retirement obligation for the years ended December 31, 2021 and 2020 as follows (in thousands): December 31, 2021 2020 Beginning balance at January 1, $ 4,137 $ 5,759 Asset retirement obligation — 771 Settlement of asset retirement obligation — (1,375) Retirement cost revaluation (231) (1,235) Accretion expense 229 217 Ending balance at December 31, $ 4,135 $ 4,137

ENERGY STORAGE SYSTEMS, NET

ENERGY STORAGE SYSTEMS, NET	12 Months Ended
	Dec. 31, 2021
Property, Plant and Equipment [Abstract]
ENERGY STORAGE SYSTEMS, NET	ENERGY STORAGE SYSTEMS, NET Energy Storage Systems, Net Energy storage systems, net, consists of the following (in thousands): December 31, 2021 December 31, 2020 Energy storage systems placed into service $ 143,592 $ 144,425 Less: accumulated depreciation (45,250) (33,389) Energy storage systems not yet placed into service 7,772 12,667 Total energy storage systems, net $ 106,114 $ 123,703 Depreciation expense for energy storage systems was approximately $14.4 million, $13.9 million and $9.7 million for the years ended December 31, 2021, 2020, and 2019, respectively. Depreciation expense is recognized in cost of service revenue.

BALANCE SHEET COMPONENTS

BALANCE SHEET COMPONENTS	12 Months Ended
	Dec. 31, 2021
Organization, Consolidation and Presentation of Financial Statements [Abstract]
BALANCE SHEET COMPONENTS	BALANCE SHEET COMPONENTS Inventory Inventory consists of the following (in thousands): December 31, 2021 2020 Work in process inventory $ 20,582 $ 15,296 Batteries 2,138 5,547 Total inventory $ 22,720 $ 20,843 Other Current Assets Other current assets consist of the following (in thousands): December 31, 2021 2020 Deferred costs with suppliers $ 13,744 $ 6,204 Prepaid expenses 3,137 698 Utility program deposits 353 891 Due from related parties 213 123 Other 1,194 4 Total other current assets $ 18,641 $ 7,920 Other Noncurrent Assets Other noncurrent assets consist of the following (in thousands): December 31, 2021 2020 Prepaid warranties and maintenance $ 15,991 $ 1,088 Receivable from SPEs (Note 16) 3,565 3,583 Deferred SPAC costs — 1,256 Self-generation incentive program deposits 940 1,036 Investment in VIEs 1,924 744 Revolver debt issuance costs — 73 Property and equipment, net 512 44 Other 1,599 458 Total other noncurrent assets $ 24,531 $ 8,282 Depreciation expense for property and equipment was immaterial for each of the years ended December 31, 2021, 2020 and 2019. Accrued Liabilities Accrued liabilities consist of the following (in thousands): December 31, 2021 2020 Accrued payables $ 25,062 $ 9,799 Accrued interest – notes payable 344 6,149 Other accrued liabilities 587 124 Total accrued liabilities $ 25,993 $ 16,072 Other Current Liabilities Other current liabilities consist of the following (in thousands): December 31, 2021 2020 System advances $ 267 $ 640 Lease liabilities – current portion 1,240 333 Due to related parties 306 399 Other — 217 Total other current liabilities $ 1,813 $ 1,589

NOTES PAYABLE

NOTES PAYABLE	12 Months Ended
	Dec. 31, 2021
Debt Disclosure [Abstract]
NOTES PAYABLE	NOTES PAYABLE Revolving Loan Due to SPE Member In April 2017, the Company entered into a revolving loan agreement with an affiliate of a member of certain of the Company’s special purpose entities (“SPE”). This agreement was, from time to time, subsequently amended. The purpose of this revolving loan agreement was to finance the Company’s purchase of hardware for its various energy storage system projects. The agreement had a total revolving loan capacity of $45.0 million that bore fixed interest at 10% with a maturity date of June 2020. In May 2020, concurrent with the 2020 Credit Agreement discussed below, the Company entered into an amendment to the revolving loan agreement, which reduced the loan capacity to $35.0 million and extended the maturity date to May 2021. The amendment increased the fixed interest rate for any borrowings outstanding more than nine months to 14% thereafter. Additionally, under the original terms of the revolving loan agreement, the Company was able to finance 100% of the value of the hardware purchased up to the total loan capacity. The amendment reduced the advance rate to 85%, with an additional reduction to 70% in August 2020. The amendment was accounted for as a modification of the debt, which did not have a material impact on the consolidated financial statements. As of December 31, 2020, the Company had $7.4 million outstanding under the revolving loan agreement. In April 2021, the Company repaid the remaining outstanding balance of this facility with the proceeds received from the Merger. The facility was terminated after the repayment in April 2021. Term Loan Due to SPE Member In December 2018, the Company entered into a term loan in the amount of $13.3 million with an affiliate of a member of certain SPEs with the Company. The term loan bore fixed interest of 12.5% on the outstanding principal balance with a final balloon payment of $3.0 million due at the maturity date of June 30, 2020. In May 2020, the Company repaid the remaining outstanding balance of $5.9 million with the proceeds received through the 2020 Credit Agreement discussed below. Term Loan Due to Former Non-Controlling Interest Holder In June 2018, the Company acquired the outstanding member interests of an entity controlled by the Company for $8.1 million. The Company financed this acquisition by entering into a term loan agreement with the noncontrolling member bearing fixed interest of 4.5% per quarter (18.0% per annum) on the outstanding principal balance. The loan required fixed quarterly payments throughout the term of the loan, which was scheduled to be paid in full by April 1, 2026. In May 2020, the Company amended the term loan and, using the proceeds from the 2020 Credit Agreement discussed below, prepaid $1.5 million of principal and interest on the note, of which $1.0 million was towards the outstanding principal balance, thereby reducing the fixed quarterly payment due to the lender. In relation to this amendment, the Company was required to issue warrants for 400,000 shares of common stock resulting in a discount to the term loan of $0.2 million. As of December 31, 2020, the outstanding balance was $5.8 million. In April 2021, the Company repaid the remaining outstanding balance of this facility with the proceeds received from the Merger. Upon prepayment of this facility, the Company incurred $2.6 million in prepayment penalties that were recorded to loss on extinguishment of debt in the Company’s statement of operations. The facility was terminated after the repayment in April 2021. 2020 Credit Agreement In May 2020, the Company entered into a credit agreement (“2020 Credit Agreement”) with a new lender that provided the Company with proceeds of $25.0 million to provide the Company with access to working capital towards the purchase of energy storage system equipment. The 2020 Credit Agreement has a maturity date of the earlier of (1) May 2021, (2) the maturity date of the revolving loan agreement, or (3) the maturity date of the Pre-Merger Convertible Promissory Notes discussed below in Note 12 - Convertible Promissory Notes . The loan bore interest of 12% per annum, of which 8% was paid in cash and 4% added back to principal of the loan balance every quarter. The Company used a portion of the proceeds towards payments associated with existing debt as previously discussed. As of December 31, 2020, the outstanding balance was $25.6 million. In April 2021, the Company repaid the remaining outstanding balance of this facility with the proceeds received from the Merger. Upon prepayment of this facility, the Company incurred $1.4 million in prepayment penalties that were recorded to loss on extinguishment of debt in the Company’s statement of operations. The facility was terminated after the repayment in April 2021. 2021 Credit Agreement In January 2021, the Company, through a wholly owned Canadian entity, entered into a credit agreement to provide a total of $2.7 million towards the financing of certain energy storage systems. The credit agreement is structured on a non-recourse basis and the system will be operated by the Company. The credit agreement has a stated interest of 5.45% and a maturity date of June 2031. The Company received an advance under the credit agreement of $1.8 million in January 2021. The repayment of advances received under this credit agreement is determined by the lender based on the proceeds generated by the Company through the operation of the underlying energy storage systems. As of December 31, 2021, the outstanding balance was $1.9 million. The Company was in compliance with all covenants contained in the 2021 Credit Agreement as of December 31, 2021. The Company’s outstanding debt consisted of the following as of December 31, 2021 (in thousands): December 31, 2021 Outstanding principal $ 1,902 Unamortized discount (215) Carrying value of debt $ 1,687 As of December 31, 2020, the Company had various convertible notes outstanding to investors. The Company refers to the collective group of all such note instruments as the “Pre-Merger Convertible Promissory Notes.” As of December 31, 2020, these Pre-Merger Convertible Promissory Notes had a balance of $67.6 million. During the year ended December 31, 2021, the Company issued additional convertible notes, including convertible promissory notes issued and sold in January 2021 (the “Q1 2021 Convertible Notes”) and the 2028 Convertible Notes. Upon effectiveness of the Merger on April 28, 2021, all outstanding Pre-Merger Convertible Promissory Notes were converted to common stock and cancelled (see “—Conversion and Cancellation of Convertible Promissory Notes Upon Merger” below). As of December 31, 2021, the Pre-Merger Convertible Promissory Notes and the Q1 2021 Convertible Notes were no longer outstanding. Q1 2021 Convertible Notes In January 2021, the Company issued and sold the Q1 2021 Convertible Notes under the same terms as the then existing Pre-Merger Convertible Promissory Notes to various investors with aggregate gross proceeds of $1.1 million. The Company evaluated the conversion option within the Q1 2021 Convertible Notes and determined the effective conversion price was beneficial to the note holders. Conversion and Cancellation of Convertible Promissory Notes Upon Merger Immediately prior to the effectiveness of the Merger, the entire balance of the Company’s outstanding Pre-Merger Convertible Promissory Notes issued by Legacy Stem automatically converted into shares of Legacy Stem Common Stock. Upon the effectiveness of the Merger, these shares of Legacy Stem Common Stock automatically converted into 10,921,548 shares of common stock of Stem. The balance associated with the outstanding Pre-Merger Convertible Promissory Notes totaling $77.7 million, including $7.7 million of interest accrued on the notes through the date of Merger, was reclassified to additional paid-in-capital. The unamortized portion of the debt discount associated with the outstanding Q1 2021 Convertible Notes totaling $1.1 million was fully expensed to loss on extinguishment of debt on the Company’s statement of operations. 2028 Convertible Notes and Capped Call Options 2028 Convertible Notes On November 22, 2021, the Company issued $460.0 million aggregate principal amount of its 2028 Convertible Notes in a private placement offering to qualified institutional buyers (the “Initial Purchasers”) pursuant to Rule 144A under the Securities Act of 1933, as amended. The 2028 Convertible Notes are senior, unsecured obligations of the Company and bear interest at a rate of 0.5% per year, payable in cash semi-annually in arrears in June and December of each year, beginning in June 2022. The notes will mature on December 1, 2028, unless earlier repurchased, redeemed or converted in accordance with their terms prior to such date. Upon conversion, the Company may choose to pay or deliver, as the case may be, cash, shares of common stock or a combination of cash and shares of common stock. The Notes are redeemable for cash at the Company’s option at any time given certain conditions (as discussed below), at an initial conversion rate of 34.1965 shares of common stock per $1,000 principal amount of 2028 Convertible Notes, which is equivalent to an initial conversion price of approximately $29.24 (the “2028 Conversion Price”) per share of the Company’s common stock. The conversion rate is subject to customary adjustments for certain events as described in the Indenture. The Company may redeem for cash all or any portion of the 2028 Convertible Notes, at the Company’s option, on or after December 5, 2025 if the last reported sale price of the Company’s common stock has been at least 130% of the 2028 Conversion Price then in effect for at least 20 trading days at a redemption price equal to 100% of the principal amount of the 2028 Convertible Notes to be redeemed, plus accrued and unpaid interest. The Company’s net proceeds from this offering were approximately $445.7 million, after deducting the Initial Purchasers’ discounts and debt issuance costs. To minimize the impact of potential dilution to the Company’s common stockholders upon conversion of the 2028 Convertible Notes, the Company entered into separate capped calls transactions (the “Capped Calls”) as described below. In accordance with accounting guidance for debt with conversion and other options, the Company separately accounted for the liability and equity components of the 2028 Convertible Notes by allocating the proceeds between the liability component and the equity component, due to the Company's ability to settle the 2028 Convertible Notes in cash, its common Stock, or a combination of cash and common Stock at the option of the Company. The carrying amount of the liability component was calculated by measuring the fair value of a similar liability that does not have an associated conversion feature. The equity component of the 2028 Convertible Notes was recognized as a debt discount and represents the difference between the gross proceeds from the issuance of the 2028 Convertible Notes and the fair value of the liability component of the 2028 Convertible Notes on the date of issuance. The debt discount is amortized to interest expense using the effective interest method over approximately seven years, or the expected life of the 2028 Convertible Notes. The equity component is not remeasured as long as it continues to meet the conditions for equity classification. After allocating the proceeds of the liability and equity components, the Company further allocated $14.3 million initial purchasers’ debt discount and debt issuance cost of $12.4 million and $1.9 million, respectively. The initial purchaser’s discount and debt issuance costs primarily consisted of underwriters, advisory, legal, and accounting fees. These costs were allocated to the debt and equity components based on the allocation of the proceeds as follows (in thousands): Amount Equity Component Debt Component Initial Purchaser’s Debt Discount $ 12,420 $ 3,650 $ 8,770 Debt Issuance Costs 1,871 550 1,321 Total $ 14,291 $ 4,200 $ 10,091 The portion allocated to the debt component is amortized to interest expense using the effective interest method over the expected life of the 2028 Convertible Notes, or approximately its seven-year term. The effective interest rate on the liability component of the 2028 Convertible Notes for the period from the date of issuance through December 2028 is 5.96%, which remains unchanged from the date of issuance. The outstanding 2028 Convertible Notes balances as of December 31, 2021 , are summarized in the following table (in thousands): December 31, 2021 Debt Component Outstanding principal $ 460,000 Unamortized initial purchaser’s debt discount and debt issuance cost (143,458) Net carrying amount $ 316,542 At the original issuance date, the fair value of the debt component of the Company’s 2028 Convertible Notes was $324.8 million and the estimated fair value of the equity component was $135.2 million, as measured on the date of issuance, resulting in a total fair value of $460.0 million for the 2028 Convertible Notes. The 2028 Convertible Notes were priced at par at the valuation date resulting in the fair value of the 2028 Convertible Notes equal to the principal amount of $460.0 million. The fair value of the equity component has been calculated as the residual amount between the fair value of the 2028 Convertible Notes and the fair value of the debt component. The following table presents total interest expense recognized related to the 2028 Convertible Notes during the year ended December 31, 2021 (in thousands) : December 31, 2021 Cash interest expense Contractual interest expense $ 249 Non-cash interest expense Amortization of debt discount and debt issuance cost $ 1,812 Total interest expense $ 2,061 Capped Call Options On November 17, 2021, in connection with the pricing of the 2028 Convertible Notes, and on November 19, 2021, in connection with the exercise in full by the Initial Purchasers of their option to purchase additional Notes, the Company entered into Capped Calls with certain counterparties. The Company used $66.7 million of the net proceeds to pay the cost of the Capped Calls. The Capped Calls have an initial strike price of $29.2428 per share, which corresponds to the initial conversion price of the 2028 Convertible Notes and is subject to anti-dilution adjustments. The Capped Calls have a cap price of $49.6575 per share, subject to certain adjustments. The Capped Calls are considered separate transactions entered into by and between the Company and the Capped Calls counterparties, and are not part of the terms of the 2028 Convertible Notes. The Company recorded a reduction to additional paid-in capital of $66.7 million during the year ended December 31, 2021 related to the premium payments for the Capped Calls. These instruments meet the conditions outlined in ASC 815 to be classified in stockholders’ equity (deficit) and are not subsequently remeasured as long as the conditions for equity classification continue to be met.

CONVERTIBLE PROMISSORY NOTES

CONVERTIBLE PROMISSORY NOTES	12 Months Ended
	Dec. 31, 2021
Debt Disclosure [Abstract]
CONVERTIBLE PROMISSORY NOTES	NOTES PAYABLE Revolving Loan Due to SPE Member In April 2017, the Company entered into a revolving loan agreement with an affiliate of a member of certain of the Company’s special purpose entities (“SPE”). This agreement was, from time to time, subsequently amended. The purpose of this revolving loan agreement was to finance the Company’s purchase of hardware for its various energy storage system projects. The agreement had a total revolving loan capacity of $45.0 million that bore fixed interest at 10% with a maturity date of June 2020. In May 2020, concurrent with the 2020 Credit Agreement discussed below, the Company entered into an amendment to the revolving loan agreement, which reduced the loan capacity to $35.0 million and extended the maturity date to May 2021. The amendment increased the fixed interest rate for any borrowings outstanding more than nine months to 14% thereafter. Additionally, under the original terms of the revolving loan agreement, the Company was able to finance 100% of the value of the hardware purchased up to the total loan capacity. The amendment reduced the advance rate to 85%, with an additional reduction to 70% in August 2020. The amendment was accounted for as a modification of the debt, which did not have a material impact on the consolidated financial statements. As of December 31, 2020, the Company had $7.4 million outstanding under the revolving loan agreement. In April 2021, the Company repaid the remaining outstanding balance of this facility with the proceeds received from the Merger. The facility was terminated after the repayment in April 2021. Term Loan Due to SPE Member In December 2018, the Company entered into a term loan in the amount of $13.3 million with an affiliate of a member of certain SPEs with the Company. The term loan bore fixed interest of 12.5% on the outstanding principal balance with a final balloon payment of $3.0 million due at the maturity date of June 30, 2020. In May 2020, the Company repaid the remaining outstanding balance of $5.9 million with the proceeds received through the 2020 Credit Agreement discussed below. Term Loan Due to Former Non-Controlling Interest Holder In June 2018, the Company acquired the outstanding member interests of an entity controlled by the Company for $8.1 million. The Company financed this acquisition by entering into a term loan agreement with the noncontrolling member bearing fixed interest of 4.5% per quarter (18.0% per annum) on the outstanding principal balance. The loan required fixed quarterly payments throughout the term of the loan, which was scheduled to be paid in full by April 1, 2026. In May 2020, the Company amended the term loan and, using the proceeds from the 2020 Credit Agreement discussed below, prepaid $1.5 million of principal and interest on the note, of which $1.0 million was towards the outstanding principal balance, thereby reducing the fixed quarterly payment due to the lender. In relation to this amendment, the Company was required to issue warrants for 400,000 shares of common stock resulting in a discount to the term loan of $0.2 million. As of December 31, 2020, the outstanding balance was $5.8 million. In April 2021, the Company repaid the remaining outstanding balance of this facility with the proceeds received from the Merger. Upon prepayment of this facility, the Company incurred $2.6 million in prepayment penalties that were recorded to loss on extinguishment of debt in the Company’s statement of operations. The facility was terminated after the repayment in April 2021. 2020 Credit Agreement In May 2020, the Company entered into a credit agreement (“2020 Credit Agreement”) with a new lender that provided the Company with proceeds of $25.0 million to provide the Company with access to working capital towards the purchase of energy storage system equipment. The 2020 Credit Agreement has a maturity date of the earlier of (1) May 2021, (2) the maturity date of the revolving loan agreement, or (3) the maturity date of the Pre-Merger Convertible Promissory Notes discussed below in Note 12 - Convertible Promissory Notes . The loan bore interest of 12% per annum, of which 8% was paid in cash and 4% added back to principal of the loan balance every quarter. The Company used a portion of the proceeds towards payments associated with existing debt as previously discussed. As of December 31, 2020, the outstanding balance was $25.6 million. In April 2021, the Company repaid the remaining outstanding balance of this facility with the proceeds received from the Merger. Upon prepayment of this facility, the Company incurred $1.4 million in prepayment penalties that were recorded to loss on extinguishment of debt in the Company’s statement of operations. The facility was terminated after the repayment in April 2021. 2021 Credit Agreement In January 2021, the Company, through a wholly owned Canadian entity, entered into a credit agreement to provide a total of $2.7 million towards the financing of certain energy storage systems. The credit agreement is structured on a non-recourse basis and the system will be operated by the Company. The credit agreement has a stated interest of 5.45% and a maturity date of June 2031. The Company received an advance under the credit agreement of $1.8 million in January 2021. The repayment of advances received under this credit agreement is determined by the lender based on the proceeds generated by the Company through the operation of the underlying energy storage systems. As of December 31, 2021, the outstanding balance was $1.9 million. The Company was in compliance with all covenants contained in the 2021 Credit Agreement as of December 31, 2021. The Company’s outstanding debt consisted of the following as of December 31, 2021 (in thousands): December 31, 2021 Outstanding principal $ 1,902 Unamortized discount (215) Carrying value of debt $ 1,687 As of December 31, 2020, the Company had various convertible notes outstanding to investors. The Company refers to the collective group of all such note instruments as the “Pre-Merger Convertible Promissory Notes.” As of December 31, 2020, these Pre-Merger Convertible Promissory Notes had a balance of $67.6 million. During the year ended December 31, 2021, the Company issued additional convertible notes, including convertible promissory notes issued and sold in January 2021 (the “Q1 2021 Convertible Notes”) and the 2028 Convertible Notes. Upon effectiveness of the Merger on April 28, 2021, all outstanding Pre-Merger Convertible Promissory Notes were converted to common stock and cancelled (see “—Conversion and Cancellation of Convertible Promissory Notes Upon Merger” below). As of December 31, 2021, the Pre-Merger Convertible Promissory Notes and the Q1 2021 Convertible Notes were no longer outstanding. Q1 2021 Convertible Notes In January 2021, the Company issued and sold the Q1 2021 Convertible Notes under the same terms as the then existing Pre-Merger Convertible Promissory Notes to various investors with aggregate gross proceeds of $1.1 million. The Company evaluated the conversion option within the Q1 2021 Convertible Notes and determined the effective conversion price was beneficial to the note holders. Conversion and Cancellation of Convertible Promissory Notes Upon Merger Immediately prior to the effectiveness of the Merger, the entire balance of the Company’s outstanding Pre-Merger Convertible Promissory Notes issued by Legacy Stem automatically converted into shares of Legacy Stem Common Stock. Upon the effectiveness of the Merger, these shares of Legacy Stem Common Stock automatically converted into 10,921,548 shares of common stock of Stem. The balance associated with the outstanding Pre-Merger Convertible Promissory Notes totaling $77.7 million, including $7.7 million of interest accrued on the notes through the date of Merger, was reclassified to additional paid-in-capital. The unamortized portion of the debt discount associated with the outstanding Q1 2021 Convertible Notes totaling $1.1 million was fully expensed to loss on extinguishment of debt on the Company’s statement of operations. 2028 Convertible Notes and Capped Call Options 2028 Convertible Notes On November 22, 2021, the Company issued $460.0 million aggregate principal amount of its 2028 Convertible Notes in a private placement offering to qualified institutional buyers (the “Initial Purchasers”) pursuant to Rule 144A under the Securities Act of 1933, as amended. The 2028 Convertible Notes are senior, unsecured obligations of the Company and bear interest at a rate of 0.5% per year, payable in cash semi-annually in arrears in June and December of each year, beginning in June 2022. The notes will mature on December 1, 2028, unless earlier repurchased, redeemed or converted in accordance with their terms prior to such date. Upon conversion, the Company may choose to pay or deliver, as the case may be, cash, shares of common stock or a combination of cash and shares of common stock. The Notes are redeemable for cash at the Company’s option at any time given certain conditions (as discussed below), at an initial conversion rate of 34.1965 shares of common stock per $1,000 principal amount of 2028 Convertible Notes, which is equivalent to an initial conversion price of approximately $29.24 (the “2028 Conversion Price”) per share of the Company’s common stock. The conversion rate is subject to customary adjustments for certain events as described in the Indenture. The Company may redeem for cash all or any portion of the 2028 Convertible Notes, at the Company’s option, on or after December 5, 2025 if the last reported sale price of the Company’s common stock has been at least 130% of the 2028 Conversion Price then in effect for at least 20 trading days at a redemption price equal to 100% of the principal amount of the 2028 Convertible Notes to be redeemed, plus accrued and unpaid interest. The Company’s net proceeds from this offering were approximately $445.7 million, after deducting the Initial Purchasers’ discounts and debt issuance costs. To minimize the impact of potential dilution to the Company’s common stockholders upon conversion of the 2028 Convertible Notes, the Company entered into separate capped calls transactions (the “Capped Calls”) as described below. In accordance with accounting guidance for debt with conversion and other options, the Company separately accounted for the liability and equity components of the 2028 Convertible Notes by allocating the proceeds between the liability component and the equity component, due to the Company's ability to settle the 2028 Convertible Notes in cash, its common Stock, or a combination of cash and common Stock at the option of the Company. The carrying amount of the liability component was calculated by measuring the fair value of a similar liability that does not have an associated conversion feature. The equity component of the 2028 Convertible Notes was recognized as a debt discount and represents the difference between the gross proceeds from the issuance of the 2028 Convertible Notes and the fair value of the liability component of the 2028 Convertible Notes on the date of issuance. The debt discount is amortized to interest expense using the effective interest method over approximately seven years, or the expected life of the 2028 Convertible Notes. The equity component is not remeasured as long as it continues to meet the conditions for equity classification. After allocating the proceeds of the liability and equity components, the Company further allocated $14.3 million initial purchasers’ debt discount and debt issuance cost of $12.4 million and $1.9 million, respectively. The initial purchaser’s discount and debt issuance costs primarily consisted of underwriters, advisory, legal, and accounting fees. These costs were allocated to the debt and equity components based on the allocation of the proceeds as follows (in thousands): Amount Equity Component Debt Component Initial Purchaser’s Debt Discount $ 12,420 $ 3,650 $ 8,770 Debt Issuance Costs 1,871 550 1,321 Total $ 14,291 $ 4,200 $ 10,091 The portion allocated to the debt component is amortized to interest expense using the effective interest method over the expected life of the 2028 Convertible Notes, or approximately its seven-year term. The effective interest rate on the liability component of the 2028 Convertible Notes for the period from the date of issuance through December 2028 is 5.96%, which remains unchanged from the date of issuance. The outstanding 2028 Convertible Notes balances as of December 31, 2021 , are summarized in the following table (in thousands): December 31, 2021 Debt Component Outstanding principal $ 460,000 Unamortized initial purchaser’s debt discount and debt issuance cost (143,458) Net carrying amount $ 316,542 At the original issuance date, the fair value of the debt component of the Company’s 2028 Convertible Notes was $324.8 million and the estimated fair value of the equity component was $135.2 million, as measured on the date of issuance, resulting in a total fair value of $460.0 million for the 2028 Convertible Notes. The 2028 Convertible Notes were priced at par at the valuation date resulting in the fair value of the 2028 Convertible Notes equal to the principal amount of $460.0 million. The fair value of the equity component has been calculated as the residual amount between the fair value of the 2028 Convertible Notes and the fair value of the debt component. The following table presents total interest expense recognized related to the 2028 Convertible Notes during the year ended December 31, 2021 (in thousands) : December 31, 2021 Cash interest expense Contractual interest expense $ 249 Non-cash interest expense Amortization of debt discount and debt issuance cost $ 1,812 Total interest expense $ 2,061 Capped Call Options On November 17, 2021, in connection with the pricing of the 2028 Convertible Notes, and on November 19, 2021, in connection with the exercise in full by the Initial Purchasers of their option to purchase additional Notes, the Company entered into Capped Calls with certain counterparties. The Company used $66.7 million of the net proceeds to pay the cost of the Capped Calls. The Capped Calls have an initial strike price of $29.2428 per share, which corresponds to the initial conversion price of the 2028 Convertible Notes and is subject to anti-dilution adjustments. The Capped Calls have a cap price of $49.6575 per share, subject to certain adjustments. The Capped Calls are considered separate transactions entered into by and between the Company and the Capped Calls counterparties, and are not part of the terms of the 2028 Convertible Notes. The Company recorded a reduction to additional paid-in capital of $66.7 million during the year ended December 31, 2021 related to the premium payments for the Capped Calls. These instruments meet the conditions outlined in ASC 815 to be classified in stockholders’ equity (deficit) and are not subsequently remeasured as long as the conditions for equity classification continue to be met.

WARRANTS

WARRANTS	12 Months Ended
	Dec. 31, 2021
Equity [Abstract]
WARRANTS	WARRANTS Legacy Stem Warrants Since inception the Company has issued warrants to purchase shares of Legacy Stem’s preferred stock in conjunction with various debt financings. See Note 5 - Fair Value Measurements, for further information regarding fair value measurements associated with the resulting warrant liabilities, which are remeasured on a recurring basis each period. The Company has also issued warrants to purchase shares of Legacy Stem’s common stock. Upon effectiveness of the Merger, the Company had 50,207,439 warrants outstanding, of which substantially all were converted into 2,759,970 shares of common stock of Stem. Upon conversion of the warrants, the existing warrant liabilities were remeasured to fair value resulting in a gain on remeasurement of $100.9 million and a total warrant liability of $60.6 million, which was then reclassified to additional paid-in-capital. As of December 31, 2021, there were 23,673 Legacy Stem Warrants outstanding. These instruments are exercisable into the Company’s common stock and are equity classified. Public Warrants and Private Placement Warrants As part of STPK’s initial public offering, under the Warrant Agreement dated as of August 20, 2020 (the “Warrant Agreement”) and, prior to the effectiveness of the Merger, STPK issued 12,786,168 warrants each of which entitled the holder to purchase one share of common stock at an exercise price of $11.50 per share of common stock (the “Public Warrants”). Simultaneously with the closing of the Initial Public Offering, STPK completed the private sale of 7,181,134 million warrants to STPK’s sponsor (the “Private Warrants”). Upon issuance, these warrants met the criteria for liability classification. Upon the effectiveness of the Merger, Stem assumed the outstanding Public Warrants and Private Warrants, which continued to meet the criteria for liability classification, resulting in assumed warrant liabilities of $185.9 million and $116.7 million, respectively, or a total warrant liability of $302.6 million. Such warrants were initially recorded at fair value and remeasured to fair value at each reporting period. The fair value of the Private Warrants was determined using the Black-Scholes method as well as a discount for lack of marketability. Black-Scholes inputs used to value the warrants are based on information from purchase agreements and within valuation reports prepared by an independent third party for the Company. Inputs include exercise price, selection of guideline public companies, volatility, fair value of common stock, expected dividend rate and risk-free interest rate. On June 25, 2021, the Company entered into an exchange agreement (the “Exchange Agreement”) with the holders of the 7,181,134 outstanding Private Placement Warrants, pursuant to which such holders received 4,683,349 shares of the Company’s common stock on June 30, 2021, in exchange for the cancellation of the outstanding Private Placement Warrants. The Exchange Shares were issued in reliance upon the exemption provided by Section 3(a)(9) of the Securities Act of 1933, as amended. Immediately prior to the exchange, the Private Warrants were marked to fair value, resulting in a loss of $52.0 million. As a result of the Exchange Agreement, there were no Private Warrants outstanding as of December 31, 2021. On August 20, 2021, the Company issued an irrevocable notice for redemption of all 12,786,129 of the Company’s outstanding public warrants at 5:00 p.m. Eastern time on September 20, 2021 (“Redemption Date”). Pursuant to the notice of redemption, holders exercised 12,638,723 Public Warrants for a purchase price of $11.50 per share, for proceeds to the Company of approximately $145.3 million. The Company redeemed all remaining outstanding Public Warrants that had not been exercised as of 5:00 p.m. Eastern time on the Redemption Date. As a result of the settlement of the Public Warrants, the Company recorded a gain of $134.9 million on the revaluation of the warrant liability. The Company also recorded a gain of $2.1 million on the redemption of unexercised public warrants. These gains are recorded in “change in fair value of warrants and embedded derivative” in the consolidated statements of operation in the year ended December 31, 2021. The public warrants have been delisted from the NYSE, and there are no public warrants left outstanding. Warrants Issued for Services On April 7, 2021, the Company entered into a strategic relationship with an existing shareholder not deemed to be a related party to jointly explore on a non-exclusive basis possible business opportunities to advance projects in the United States, the United Kingdom, Europe and Asia. As consideration for the strategic relationship, upon closing of the Merger, the Company issued warrants to purchase 350,000 shares of the Company’s common stock at an exercise price of $0.01 per share. These warrants were deemed to have been fully earned as of the grant date. The warrants were valued at fair market value as of the grant date totaling $9.2 million and recorded to general and administrative expense in the Company’s statement of operations. In May 2021, all of these warrants were exercised for shares of the Company’s common stock.

COMMON STOCK

COMMON STOCK	12 Months Ended
	Dec. 31, 2021
Equity [Abstract]
COMMON STOCK	COMMON STOCK The Company had reserved shares of common stock for issuance as follows: December 31, Shares reserved for warrants 23,673 Options issued and outstanding 8,766,466 Shares available for future issuance under equity incentive plan 20,844,788 Conversion of 2028 Convertible Notes 20,842,773 Total 50,477,700 As of December 31, 2021, the Company had 23,722,254 shares of common stock reserved for future issuance under equity incentive plans corresponding to the 2021 Equity Incentive Plan

STOCK-BASED COMPENSATION

STOCK-BASED COMPENSATION	12 Months Ended
	Dec. 31, 2021
Share-based Payment Arrangement [Abstract]
STOCK-BASED COMPENSATION	STOCK-BASED COMPENSATION Under both the Stem, Inc. 2009 Equity Incentive Plan (the “2009 Plan”) and the Stem Inc. 2021 Equity Incentive Plan (the “2021 Plan,” and together with the 2009 Plan, the “Plans”), the Company may grant stock options, stock appreciation rights, restricted stock, restricted stock units (“RSUs”) and other awards that are settled in shares of the Company’s common stock. The Plans permit net settlement of vested awards, pursuant to which the award holder forfeits a portion of the vested award to satisfy the purchase price (in the case of stock options), the holder’s withholding tax obligation, if any, or both. When the holder net settles the tax obligation, the Company pays the amount of the withholding tax to the U.S. government in cash, which is accounted for as an adjustment to additional paid-in-capital. The Company does not intend to grant new awards under the 2009 Plan. At December 31, 2021, 7,754,811 stock options were outstanding under the 2009 Plan. In May 2021, the Company began issuing awards under the 2021 Plan, with 23,722,254 shares reserved thereunder. Stock Options Under the Plans, the exercise price of an option cannot be less than 100% of the fair value of one share of common stock for incentive or non-qualified stock options, and not less than 110% of the fair value for stockholders owning greater than 10% of all classes of stock, as determined by the Company’s Board of Directors (the “Board”). Options under the Plans generally expire after 10 years. Under the Plans, the Compensation Committee of the Board determines when the options granted will become exercisable. Options granted under the Plans generally vest 1/4 one year from the grant date and then 1/48 each month over the following three years and are exercisable for 10 years from the date of the grant. The Plans allow for exercise of unvested options with repurchase rights over the restricted common stock issued at the original exercise price. The repurchase rights lapse at the same rate as the options vest. The following table summarizes the stock option activity for the period ended December 31, 2021: Number of Weighted- Weighted- Aggregate Balances as of December 31, 2020 51,379,939 $ 0.56 7.2 $ 46,516 Retroactive application of recapitalization (40,314,281) 2.05 — — Adjusted Balance as of December 31, 2020 11,065,658 2.61 7.2 46,516 Options granted 1,079,583 28.73 Options exercised (3,235,713) 1.64 Options forfeited (129,102) 15.18 Options expired (13,960) 0.53 Balances as of December 31, 2021 8,766,466 $ 6.01 7.1 $ 123,570 Options vested and exercisable — December 31, 2021 6,298,675 $ 2.61 6.4 $ 103,100 The weighted-average grant date fair value of stock options granted to employees was $18.84, $3.79 and $1.58 during the years ended December 31, 2021, 2020, and 2019, respectively. The intrinsic value of options exercised was $56.1 million, $1.1 million and less than $0.1 million during the years ended December 31, 2021, 2020, and 2019, respectively. During the year ended December 31, 2021, the Company issued 1,054,594 shares of common stock from the net settlement of 1,648,463 stock options and shares granted. The Company paid $12.6 million in withholding taxes in connection with the net share settlement of these awards. Significant Assumptions in Estimating Option Fair Value The Company uses the Black-Scholes model for estimating the fair value of options granted. The weighted-average assumptions used in the Black-Scholes are as follows: December 31, 2021 2020 2019 Expected volatility 74.00 % 71.41 % 69.10 % Risk-free interest rate 1.06 % 0.49 % 2.47 % Expected term (years) 6.23 5.82 5.83 Dividend yield — — — Restricted Stock Units RSUs represent a right to receive one share of the Company’s common stock that is both non-transferable and forfeitable unless and until certain conditions are satisfied. RSUs generally, either cliff vest on the third anniversary of the award grant date, or vest 1/4 per year over a four-year period, subject to continued employment through each anniversary. During the year ended December 31, 2021 , the Company granted RSUs, which vest 1/5 per year over approximately a seven-year period starting in April 2024. The fair value of restricted stock units is determined on the grant date and is amortized over the vesting period on a straight-line basis. The following table summarizes the RSU activity for the period ended December 31, 2021: Number of Weighted- Balances as of December 31, 2020 — $ — RSUs granted 1,801,831 36.0 RSUs vested — — RSUs forfeited (2,154) 26.1 Balances as of December 31, 2021 1,799,677 36.0 The fair value of all RSUs granted during the year ended December 31, 2021 was $64.8 million . During the year ended December 31, 2021 , no RSUs vested. Stock-Based Compensation Expense The following table summarizes stock-based compensation expense recorded in each component of operating expenses in the Company’s consolidated statements of operations and comprehensive loss (in thousands): Year Ended December 31, 2021 2020 2019 Sales and marketing $ 1,723 $ 396 $ 364 Research and development 2,367 1,211 901 General and administrative 9,456 2,935 266 Total stock-based compensation expense $ 13,546 $ 4,542 $ 1,531 As of December 31, 2021, the Company had approximately $21.1 million of remaining unrecognized stock-based compensation expense for stock options, which is expected to be recognized over a weighted average period of 3.2 years. As of December 31, 2021, the Company had approximately $56.5 million of remaining unrecognized stock-based compensation expense for RSUs, which is expected to be recognized over a weighted average period of 4.9 years. Research and development expenses of $1.2 million corresponding to i nternal-use software, were capitalized during the year ended December 31, 2021.

SPECIAL PURPOSE ENTITIES

SPECIAL PURPOSE ENTITIES	12 Months Ended
	Dec. 31, 2021
Organization, Consolidation and Presentation of Financial Statements [Abstract]
SPECIAL PURPOSE ENTITIES	SPECIAL PURPOSE ENTITIES The Company has formed various SPEs to finance the development and construction of its energy storage systems. These SPEs, which are structured as limited liability companies, obtain financing from outside investors and purchase projects from the Company under master purchase agreements by making an upfront payment to the Company for such energy storage systems. As discussed in Note 2 - Summary of Significant Accounting Policies , the Company accounts for the large upfront payment received from the SPE as a financing obligation. The legal purchase of the energy storage system does not affect the Company’s legal or constructive obligation to the host customer. Consolidated VIE In September 2013, the Company entered into agreements to form SCF 1, LLC (“SCF 1”) and consolidated this SPE under the VIE consolidation model. During 2018, the Company acquired the outstanding non-controlling interests of SCF 1 which remained a VIE upon reconsideration at the acquisition. As of December 31, 2021 and 2020 , the Company’s consolidated total assets include the assets of SCF 1 that can only be used to settle the liabilities, if any, of SCF 1. The assets and liabilities of SCF 1 are comprised primarily of the following: December 31, 2021 2020 Energy storage systems, net $ 649 $ 1,463 Deferred revenue, current $ 283 $ 283 Deferred revenue, noncurrent $ 753 $ 1,047 Other liabilities $ 159 $ 239 Unconsolidated VIEs SPV II, SPV III, and SPV IV On January 23, 2015, June 7, 2016, and June 30, 2017 the Company entered into agreements to form three Limited Liability Companies: Stem Finance SPV II, LLC (“SPV II”), Stem Finance SPV III, LLC (“SPV III”), and Generate-Stem LCR, LLC (“SPV IV”), respectively. These agreements are accounted for as unconsolidated VIEs because the Company lacks the power to direct the activities that most significantly impact the economics of these entities. Although the Company is not the primary beneficiary of these entities, due to its significant continuing involvement in the generation of cash flows of the energy storage systems and legal responsibilities under the host customer contract, the Company is required to include the assets, liabilities, revenues, and expenses of these entities in its consolidated financial statements. The significant activities involve deciding which energy storage systems to be purchased by the SPE and setting of the annual operating budgets which govern the ongoing operation and maintenance of the energy storage systems. Both of these activities significantly impact the revenue, expenses, and resulting residual returns or losses that will accrue to the investors of the SPE and require approval by both Stem and the other third-party investor. Stem, the non-managing member of the SPE, shares power through its rights to (i) agree on SPE purchases of energy storage systems in the master purchase agreement, and (ii) approve the annual operating budgets in the operating and maintenance agreement. The other investor shares power through its rights as the managing member in the SPE. As a result, power is shared with the other investors in the SPE who are not considered related parties (including de facto agency relationships) of the Company. Investments in such SPEs are accounted for under the equity method of accounting and are recorded within other noncurrent assets on the consolidated balance sheets. The Company’s maximum loss exposure from these entities is limited to the aggregate carrying amount of its equity method investments. As of December 31, 2021, the Company had not provided, and is not required to provide, financial support through a liquidity arrangement or otherwise, to its SPEs, including circumstances in which it could be exposed to further losses (e.g., cash shortfalls). The Company’s cumulative share of the earnings/(losses) in SPV II, SPV III and SPV IV was $0.1 million, $0.1 million, and $0.2 million for the years ended December 31, 2021, 2020, and 2019, respectively . Copec During March 2020, the Company entered into the JV Agreement with Compania de Petroleos de Chile Copec S.A. (“Copec”), a leading wholesaler and distributor of petroleum products, that supplies fuel, lubricants, and other retail services such as carwash and foods through its series of service stations. The Company operates more than 650 service stations in Chile and more than 2,500 through different subsidiaries companies around South America, Central America, and the United States. The purpose of the JV Agreement is to form an entity with equity contributions from both Stem and Copec to explore and develop business opportunities within the commercial and industrial space, including utilities and grid operators, in Latin America with the focus of providing intelligent energy storage solutions that leverage advanced software analytics and controls (principally through the Athena Platform developed by Stem). Stem’s technology and expertise will be combined with the strength of Copec’s scale, distribution network, energy knowledge and other expertise areas to develop business in certain territories as defined in the JV Agreement. The JV entity is a VIE and the Company holds a variable interest in the JV Entity. However, the Company does not have the power to direct activities that most significantly impact the economics of the JV Entity and, as such, is not the primary beneficiary. Accordingly, the Company does not consolidate the JV Entity. The Company has concluded that it has the ability to exercise significant influence over the JV Entity, and accounts for the investment using the equity method. The following table summarizes additional information about the Company’s equity method investments, SPV II, SPV III, SPV IV and Copec: SPV II SPV III SPV IV COPEC Date formed January 23, 2015 June 7, 2016 June 30, 2017 March 24, 2020 Initial ownership % 49 % 50 % 50 % 49 % Stem’s interest 100% of Class A shares 100% of Class B shares 100% of Class B shares 100% of Class A shares Initial distributions: Class A 10% (Stem) 80% (Stem — 50%) 97.5 % To be determined Class B 90 % 20% (Stem — 100%) 2.5% (Stem) N/A As of December 31, 2021 and 2020 , the Company’s investment in its unconsolidated SPE’s, recorded within other noncurrent assets on the consolidated balance sheets, was as follows (in thousands): December 31, 2021 2020 Investment in SPV II $ — $ — Investment in SPV III 421 487 Investment in SPV IV 291 257 Copec 1,212 — Total equity method investments $ 1,924 $ 744 As discussed in Note 2 - Summary of Significant Accounting Policies , the Company accounts for the legal sales of the energy storage systems to the SPEs as a financing obligation. This is because the Company has significant continuing involvement in the generation of cash flows of the energy storage systems and continue to be legally responsible under the host customer contract. Accordingly, in addition to the equity method investment, the Company has the following financing obligations associated with energy storage systems legally sold to the unconsolidated SPEs (in thousands): December 31, 2021 2020 Financing obligation, current portion $ 15,277 $ 14,914 Financing obligation, noncurrent $ 73,204 $ 73,128 Interest expense related to the financing obligations was $8.5 million, $6.9 million, and $5.8 million for the years ended December 31, 2021, 2020, and 2019, respectively . As a result of being the accounting owner of energy storage systems sold to the SPEs and retaining the obligation to provide energy optimization services to host customers, the Company records the carrying value of energy storage system assets and obligations under the customer host contracts on its consolidated balance sheet. These balances were as follows as of December 31, 2021 and 2020 (in thousands): December 31, 2021 2020 Energy storage systems, net $ 92,426 $ 91,593 Deferred revenue, current $ 4,417 $ 3,713 Deferred revenue, noncurrent $ 10,835 $ 8,265 Other liabilities $ 3,586 $ 3,178 Because the Company is the legal party responsible for providing services to the host customer and significantly involved in generating the revenue under the host customer arrangements, the Company records the revenue associated with services, and separately records payments to the VIE as debt and interest payments. Revenues recognized by the Company associated with energy storage systems legally sold to the unconsolidated SPEs were $16.9 million, $12.8 million, and $8.8 million for the years ended December 31, 2021, 2020, and 2019, respectively . Such revenues are inclusive of incentive fees, consistent with the Company’s revenue policy. Depreciation expense recognized within cost of service revenue by the Company for the energy storage systems legally sold to the unconsolidated SPEs was $12.8 million, $11.8 million and $7.1 million for the years ended December 31, 2021, 2020, and 2019 , respectively.

NET LOSS PER SHARE

NET LOSS PER SHARE	12 Months Ended
	Dec. 31, 2021
Earnings Per Share [Abstract]
NET LOSS PER SHARE	NET LOSS PER SHAREThe following table sets forth the computation of basic and diluted net loss per share attributable to common stockholders (in thousands, except share and per share amounts): Year Ended December 31, 2021 2020 2019 Numerator - Basic and Diluted: Net loss $ (101,211) $ (156,124) $ (59,414) Less: Deemed Dividend — (9,484) (5,353) Net loss attributable to common stockholders, basic and diluted (101,211) (165,608) (64,767) Denominator: Weighted-average number of shares outstanding used to compute net loss per share attributable to common stockholders, basic and diluted 105,561,139 40,064,087 42,811,383 Net loss per share attributable to common stockholders, basic and diluted $ (0.96) $ (4.13) $ (1.51) The following potentially dilutive shares were not included in the calculation of diluted shares outstanding for the periods presented as the effect would have been anti-dilutive: December 31, 2021 2020 2019 Outstanding Pre-Merger Convertible Promissory Notes — 10,495,111 5,202,697 Outstanding 2028 Convertible Notes 15,730,390 — — Outstanding stock options 8,766,466 11,065,658 9,227,850 Outstanding warrants 23,673 10,832,616 7,672,810 Outstanding RSUs 1,799,677 — — Total 26,320,206 32,393,385 22,103,357

INCOME TAXES

INCOME TAXES	12 Months Ended
	Dec. 31, 2021
Income Tax Disclosure [Abstract]
INCOME TAXES	INCOME TAXES The components of loss before provision for income taxes for the years ended December 31, 2021, 2020, and 2019 are as follows (in thousands): December 31, 2021 2020 2019 Domestic $ (101,211) $ (156,119) $ (59,408) Foreign — — — Loss before income taxes $ (101,211) $ (156,119) $ (59,408) Due to the Company’s net losses, the Company did not record a provision for federal income taxes during the years ended December 31, 2021, 2020 and 2019, respectively. The Company continues to maintain a full valuation allowance for its net U.S. federal and state deferred tax assets. The components of the provision for income tax expense for the years ended December 31, 2021, 2020, and 2019 are as follows (in thousands): December 31, 2021 2020 2019 Current: Federal $ — $ — $ — State — 5 6 Total current — 5 6 Deferred: Federal — — — State — — — Total deferred — — — Total provision for income taxes $ — $ 5 $ 6 The effective tax rate of the Company’s provision (benefit) for income taxes differs from the federal statutory rate as follows: December 31, 2021 2020 2019 Statutory rate 21.00 % 21.00 % 21.00 % State tax 3.15 % 3.19 % 7.13 % Foreign income and withholding taxes 1.61 % 0.41 % 0.08 % Stock-based compensation 6.17 % (0.60) % (0.51) % Change in fair value of warrants 0.71 % (11.36) % 0.53 % Other (1.19) % — % (0.04) % Non-deductible interest expense (2.53) % (1.51) % (2.63) % Valuation allowance (28.92) % (11.13) % (25.56) % Total — % — % — % — % Deferred income taxes arise from temporary differences between the carrying amounts of assets and liabilities for financial reporting purposes and the amounts used for income tax reporting purposes, as well as net operating losses (“NOLs”) and tax credit carryforwards. Significant components of the Company’s deferred tax assets and liabilities as of December 31, 2021 and 2020 are as follows (in thousands): December 31, 2021 2020 Deferred tax assets: Net operating losses $ 92,160 $ 59,960 Tax credits 741 761 Depreciable assets 604 635 Operating lease liabilities 3,558 — Accruals and allowances 1,803 575 Stock-based compensation 1,359 83 Deferred revenue 24,734 27,962 Interest expense 1,209 — Other 3,989 3,035 Total gross deferred tax assets 130,157 93,011 Less: Valuation allowance (125,082) (91,315) Net deferred tax assets 5,075 1,696 Deferred tax liabilities: Amortization of asset retirement obligation (768) (944) Intangibles (862) (752) Right-of-use assets (3,445) — Total gross deferred tax liabilities (5,075) (1,696) Net deferred taxes $ — $ — As of December 31, 2021 and 2020 , the Company had federal NOL carryforwards of approximately $300.8 million and $199.8 million, respectively, and state NOL carryforwards of approximately $274.6 million and $200.5 million, respectively. The federal and state NOL carryforwards will both begin to expire in 2029. As of December 31, 2021 and 2020 , the Company had federal research and development tax credit carryforwards of $0.7 million and $0.7 million, respectively, which begin to expire in 2029 if not utilized. As of December 31, 2021 and 2020 , the Company had foreign NOL carryforwards of approximately $9.0 million and zero, respectively. As of December 31, 2021 and 2020 , the Company had California research and development tax credit carryforwards of $0.7 million and $0.7 million, respectively, which do not expire. As of December 31, 2021 and 2020 , the Company had California Enterprise Zone tax credits of zero and $0.1 million, respectively, which began to expire in 2021. In assessing the realizability of deferred tax assets, management considers whether it is more likely than not that some portion or all of the deferred tax assets will not be realized. As a result of a history of taxable losses and uncertainties as to future profitability, the Company recorded a full valuation allowance against its deferred tax assets. The valuation allowance was $125.1 million and $91.3 million as of December 31, 2021 and 2020 , respectively. Utilization of the NOL carryforwards and tax credit forwards may be subject to a substantial annual limitation due to ownership change limitations that may have occurred or that could occur in the future, as required by the Internal Revenue Code Section 382, as well as similar state provisions. In general, an “ownership change,” as defined by the code, results from a transaction or series of transactions over a three- year period resulting in an ownership change of more than 50 percentage points of the outstanding stock of a company by certain stockholders or public groups. Any limitation may result in expiration of all or a portion of the NOL or tax credit carryforwards before utilization. The Company has not performed a detailed analysis to determine whether an ownership change under Section 382 of the Code has previously occurred. As a result, the Company’s ability to utilize existing carryforwards could be restricted. The Company had gross unrecognized tax benefits of $0.7 million and $0.8 million as of December 31, 2021 and 2020, respectively . There were no material additions, reductions or settlements of unrecognized tax benefits for years ended December 31, 2021 and 2020 . The Company expects resolution of unrecognized tax benefits, if created, would occur while the full valuation allowance of deferred tax assets is maintained. The Company does not expect to have any unrecognized tax benefits that, if recognized, would affect the effective tax rate. As of December 31, 2021 , the Company does not have a liability for potential penalties or interest. The Company does not expect its unrecognized tax benefits to change significantly over the next 12 months.

COMMITMENTS AND CONTINGENCIES

COMMITMENTS AND CONTINGENCIES	12 Months Ended
	Dec. 31, 2021
Commitments and Contingencies Disclosure [Abstract]
COMMITMENTS AND CONTINGENCIES	COMMITMENTS AND CONTINGENCIESContingencies The Company is party to various legal proceedings from time to time arising in the ordinary course of its business . A liability is accrued when a loss is both probable and can be reasonably estimated. Management believes that the probability of a material loss with respect to any currently pending legal proceeding is remote. However, litigation is inherently uncertain and it is not possible to definitively predict the ultimate disposition of any of these proceedings. The Company does not believe that there are any pending legal proceedings or other loss contingencies that will, either individually or in the aggregate, have a material adverse effect on the Company’s consolidated financial statements

EMPLOYER RETIREMENT PLAN

EMPLOYER RETIREMENT PLAN	12 Months Ended
	Dec. 31, 2021
Retirement Benefits [Abstract]
EMPLOYER RETIREMENT PLAN	EMPLOYER RETIREMENT PLANThe Company sponsors a 401(k) profit sharing plan covering all eligible employees. Participants may elect to defer a percentage of their compensation ranging from 1% to 75%, up to the maximum allowable by law by making contributions to the plan. The Company may match, at its discretion, the employee contributions according to the terms of the plan. During the years ended December 31, 2021, 2020, and 2019, the Company did not match any of its employees’ contributions.

SUBSEQUENT EVENTS

SUBSEQUENT EVENTS	12 Months Ended
	Dec. 31, 2021
Subsequent Events [Abstract]
SUBSEQUENT EVENTS	SUBSEQUENT EVENTS On February 1, 2022, the Company completed the acquisition of 100% of the outstanding shares of AlsoEnergy for an aggregate purchase price of $695.0 million, consisting of approximately 75% in cash and approximately 25% in shares of the Company’s common stock. The acquisition was structured on a cash-free, debt free basis and subject to other customary adjustments as set forth in the purchase agreement. The transaction combines the Company’s storage optimization capabilities with AlsoEnergy’s solar asset performance monitoring and control software. The Company will complete the initial accounting for the acquisition during the first quarter of 2022.

SUMMARY OF SIGNIFICANT ACCOUN_2

SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES (Policies)	12 Months Ended
	Dec. 31, 2021
Accounting Policies [Abstract]
Basis of Presentation	Basis of Presentation The Company's consolidated financial statements have been prepared in accordance with GAAP.
Immaterial Out-of-Period Corrections	Immaterial Out-of-Period Corrections During the year ended December 31, 2021, the Company recorded certain out-of-period corrections related to prior interim and annual periods pertaining to the amortization of contract origination costs and valuation of energy storage systems that were decommissioned. The impact of out-of-period corrections to the year ended December 31, 2021 was an increase of $2.8 million to net loss, and increase to cost of service revenue of $1.7 million, and an increase to sales and marketing expenses of $1.1 million. The following table presents the amount of the errors identified for energy storage systems, net and contract origination costs, net as of the end of each period, and the amounts and periods in which the errors related to cost of service revenue and sales and marketing originated (in millions): (overstatement)/understatement Year Ended December 31, 2020 2019 Periods prior to 2019 Energy storage systems, net $ (1.7) $ (1.5) $ (0.9) Contract origination costs, net $ (1.1) $ (0.3) $ (0.1) Cost of service revenue $ 0.2 $ 0.6 $ 0.9 Sales and marketing $ 0.8 $ 0.2 $ 0.1 The Company corrected the out of period errors in the quarter ended December 31, 2021. The impact of the out-of-period correction for the quarter ended December 31, 2021 included corrections for the prior quarterly periods presented below. The impact to the quarter ended December 31, 2021, was an increase of $4.2 million to net loss, increase to cost of service revenue of $1.8 million and increase to sales and marketing expenses of $2.4 million. The following table presents the amounts of the errors identified for energy storage systems, net and contract origination costs, net as of the end of each period, as well as the quarterly periods in which the errors related to cost of service revenue and sales and marketing originated (in millions): (overstatement)/understatement Quarter ended September 30, 2021 Quarter ended June 30, 2021 Quarter ended March 31, 2021 Energy storage systems, net $ (1.8) $ (1.7) $ (1.7) Contract origination costs, net $ (2.4) $ (1.6) $ (1.4) Cost of service revenue $ 0.1 $ — $ — Sales and marketing $ 0.8 $ 0.2 $ 0.3 The errors and out of period corrections had no impact to the Company’s net cash used in operating activities for any of the periods presented. The Company performed a quantitative and qualitative evaluation of these out-of-period adjustments and has concluded that the amounts are not material in relation to the year ended December 31, 2021, or any prior interim or annual periods.
Reclassifications	Reclassifications Certain prior year amounts have been reclassified for consistency with the current year presentation. Such reclassifications have no impact on previously reported net loss, stockholders' equity (deficit), or cash flows.
Principles of Consolidation	Principles of Consolidation The consolidated financial statements include the accounts of the Company, its wholly-owned subsidiaries, and consolidated variable interest entities (“VIEs”). All intercompany balances and transactions have been eliminated in consolidation.
Variable Interest Entities	Variable Interest Entities The Company forms special purpose entities (“SPEs”), some of which are VIEs, with its investors in the ordinary course of business to facilitate the funding and monetization of its energy storage systems. A legal entity is considered a VIE if it has either a total equity investment that is insufficient to finance its operations without additional subordinated financial support or whose equity holders lack the characteristics of a controlling financial interest. The Company’s variable interests arise from contractual, ownership, or other monetary interests in the entity. The typical condition for a controlling financial interest ownership is holding a majority of the voting interests of an entity; however, a controlling financial interest may also exist in entities, such as VIEs, through arrangements that do not involve controlling voting interests.
Equity Method Investments	Equity Method InvestmentsThe Company has ownership interests in SPEs which it does not control. Where the Company holds an interest in these SPEs of greater than 20% and has the ability to exercise significant influence, the Company uses the equity method to account for its investments in these SPEs. Under the equity method of accounting, investments are stated at initial cost and are adjusted for subsequent additional investments and the Company’s proportionate share of earnings or losses and distributions. Such proportionate share of earnings or losses is included within other expenses, net in the consolidated statements of operations. The Company considers whether its equity method investments are impaired when events or circumstances suggest that the carrying amount may not be recoverable. An impairment charge is recognized in the consolidated statements of operations for a decline in value that is determined to be other-than-temporary. In determining if and when a decline in the fair value of these investments below their carrying value is other-than-temporary, the Company evaluates the market condition, trends of earnings and cash flows and other key measures of performance and recognizes such loss which is deemed to be other-than-temporary.
Use of Estimates	Use of Estimates The preparation of consolidated financial statements in conformity with GAAP requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities, the 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. The Company bases its estimates on historical experience and on various other assumptions believed to be reasonable. Actual results could differ from those estimates and such differences could be material to the financial position and results of operations. Significant estimates and assumptions reflected in these consolidated financial statements include, but are not limited to, depreciable life of energy systems; the amortization of financing obligations; deferred commissions and contract fulfillment costs; the valuation of energy storage systems, internally developed software, and asset retirement obligations; and the fair value of financial instruments, equity-based instruments, debt, warrant liabilities and embedded derivatives.
Segment Information	Segment Information Operating segments are defined as components of an entity for which discrete financial information is available that is regularly reviewed by the Chief Operating Decision Maker (“CODM”) in deciding how to allocate resources to an individual segment and in assessing performance. The Company’s Chief Executive Officer is the CODM. The CODM reviews financial information presented on a consolidated basis for purposes of making operating decisions, allocating resources, and evaluating financial performance. As such, management has determined that the Company operates as one
Cash and Cash Equivalents	Cash and Cash Equivalents The Company considers all highly liquid investments with an original maturity date of three months or less at the date of purchase to be cash equivalents. Cash and cash equivalents are maintained at financial institutions. The Company maintains all cash in a highly liquid form to meet current obligations.
Short-Term Investments	Short-Term Investments Investments with a maturity date greater than three months that the Company intends to convert to cash or cash equivalents within a year or less are classified as short-term investments in the Company’s consolidated balance sheets. Additionally, in accordance with ASC 320, Investments - Debt Securities , the Company has classified all short-term investments as available-for-sale securities and changes in fair market value are reported in other comprehensive income (loss).
Accounts Receivable, Net	Accounts Receivable, NetAccounts receivable are recorded at the invoiced amount, net of allowance for doubtful accounts. Accounts receivable also include unbilled accounts receivable, which is composed of the monthly energy optimization services provided and recognized but not yet invoiced as of the end of the reporting period. The allowance for doubtful accounts is based on the Company’s best estimate and is determined based upon a variety of factors, including analyses of specific customer receivables, aging, and overall assessments of collectability. Accounts receivable balances are charged against the allowance when the Company believes it is probable that the receivable will not be recovered.
Concentrations of Credit Risk and Other Uncertainties	Concentrations of Credit Risk and Other Uncertainties Financial instruments that potentially subject the Company to concentration of credit risk consist of cash and cash equivalents and accounts receivable. The Company’s cash balances are primarily invested in money market funds or on deposit at high credit quality financial institutions in the U.S. The Company’s cash and cash equivalents are held at financial institutions where account balances may at times exceed federally insured limits. Management believes the Company is not exposed to significant credit risk due to the financial strength of the depository institution in which the cash is held. The Company has no financial instruments with off-balance sheet risk of loss. At times, the Company may be subject to a concentration of credit risk in relation to certain customers due to the purchase of large energy storage systems made by such customers. The Company routinely assesses the creditworthiness of its customers. The Company has not experienced any material losses related to receivables from individual customers, or groups of customers during the years ended December 31, 2021, 2020 and 2019. The Company does not require collateral. Due to these factors, no additional credit risk beyond amounts provided for collection losses is believed by management to be probable in the Company’s accounts receivable.
Significant Customers	Significant CustomersA significant customer represents 10% or more of the Company’s total revenue or accounts receivable, net balance at each reporting date.
Inventory	Inventory Inventory consists of batteries and related components either in-process at the Company’s OEM suppliers or as a finished product at the Company’s warehouse, which are sold and delivered directly to customers under the Company’s partnership arrangements as individual assets or assembled systems. Inventory is stated at lower of cost or net realizable value with cost being determined by the specific identification method. The Company periodically reviews its inventory for potentially slow-moving or obsolete items and writes down specific items in inventory to net realizable value based on its assessment of market conditions.
Energy Storage Systems, Net	Energy Storage Systems, Net The Company sells energy optimization services to host customers through the use of energy storage systems installed at customer locations. The Company determined that it does not transfer control of these energy storage systems to the customer, which are operated and controlled via the Company’s proprietary cloud-based software (“SaaS”) platform; therefore, these energy storage systems do not qualify as a leased asset. The energy storage systems are stated at cost, less accumulated depreciation and impairment (as applicable). Energy storage systems, net is comprised of equipment costs, which include components such as batteries, inverters, and other electrical equipment, and associated design, installation, and interconnection costs required to begin providing the energy optimization services to customers. Depreciation of the energy storage systems is a component of cost of revenues within the consolidated statements of operations and is calculated using the straight-line method over the estimated useful lives of the energy storage systems, or 10 years, once the respective energy storage systems have been installed and interconnected to the power grid, the Company has received permission to operate, and the Company has begun to provide energy optimization services to the customer (i.e., energy storage system is live). Repairs and maintenance costs are expensed as incurred. Impairment charges related to energy storage system that were determined to no longer be recoverable totaled $4.3 million, $1.4 million and $0.3 million for the years ended December 31, 2021, 2020, and 2019, respectively.
Contract Origination Costs, Net, Revenue Recognition, Host Customer and Partnership Arrangements	Contract Origination Costs, Net Contract origination costs, net is stated at gross contract origination costs less accumulated amortization. Contract origination costs consists of sales commissions earned by the Company’s sales team, as well as related payroll taxes and other relevant fringe benefits that are direct, incremental, and recoverable costs of obtaining a contract with a customer. As a result, these amounts have been capitalized on the consolidated balance sheets. The Company deferred incremental costs of obtaining a contract of $3.0 million and $2.6 million during the years ended December 31, 2021 and 2020, respectively. Revenue Recognition Revenues are recognized when control of the promised goods or services are transferred to the Company’s customers in an amount that reflects the consideration that is expected to be received in exchange for those goods or services. The Company generates all of its revenues from contracts with its customers. The Company recognizes revenue through two types of arrangements with customers, host customer arrangements and partnership arrangements as described below. Host Customer Arrangements Host customer contracts are generally entered into with commercial entities that have traditionally relied on power supplied directly from the grid. Host customer arrangements consist of a promise to provide energy optimization services through the Company’s proprietary SaaS platform coupled with a dedicated energy storage system owned and controlled by the Company throughout the term of the contract. The host customer does not obtain legal title to, or ownership of the dedicated energy storage system at any point in time. The host customer is the end consumer of the energy that directly benefits from the energy optimization services provided by the Company. The term for the Company’s contracts with host customers generally ranges from 5 to 10 years, which may include certain renewal options to extend the initial contract term or certain termination options to reduce the initial contract term. Although the Company installs an energy storage system at the host customer site in order to provide the energy optimization services, the Company directs how and for what purpose the asset is used through the operation of its SaaS platform and, as such, retains control of the energy storage system; therefore, the contract does not contain a lease. The Company determines the various energy optimization services provided throughout the term of the contract, which may include services such as remote monitoring, performance reporting, preventative maintenance and other ancillary services necessary for the safe and reliable operation of the energy storage system, are part of a combined output of energy optimization services and the Company provides a single distinct combined performance obligation representing a series of distinct days of services. The Company determines the transaction price at the outset of the arrangement, primarily based on the contractual payment terms dictated by the contract with the customer. Fees charged to customers for energy optimization services generally consist of recurring fixed monthly payments throughout the term of the contract. In certain arrangements, the transaction price may include incentive payments that are earned by the host customer from utility companies in relation to the services provided by the Company. Under such arrangements, the rights to the incentive payments are assigned by the host customer to the Company. These incentives may be in the form of fixed upfront payments, variable monthly payments, or annual performance-based payments over the first five years of the customer contract term. Incentive payments may be contingent on approval from utility companies or actual future performance of the energy storage system. Substantially all of the Company’s arrangements provide customers the unilateral ability to terminate for convenience prior to the conclusion of the stated contractual term or the contractual term is shorter than the estimated benefit period, which the Company has determined to be 10 years based on the estimated useful life of the underlying energy storage systems and the period over which the customer can benefit from the energy optimization services utilizing such energy storage systems. In these instances, the Company determined that upfront incentive payments received from its customers represent a material right that is, in effect, an advance payment for future energy optimization services to be recognized throughout the estimated benefit period. In contracts where the customer does not have the unilateral ability to terminate for convenience without a penalty during the estimated benefit period, the Company determined the upfront incentive payments do not represent a material right for services provided beyond the initial contractual period and are therefore a component of the initial transaction price. The Company revisits its estimate of the benefit period each reporting period. The Company’s contracts with host customers do not contain a significant financing component. The Company transfers control of its energy optimization services to its customers continuously throughout the term of the contract (a stand-ready obligation) and revenue is recognized ratably as control of these services is transferred to its customers, in an amount that reflects the consideration the Company expects to be contractually entitled to in exchange for its services. Monthly incentive payments based on the performance of the energy storage system are allocated to the distinct month in which they are earned because the terms of the payments relate specifically to the outcome from transferring the distinct time increment (month) of service and because such amounts reflect the fees to which the Company expects to be entitled for providing energy optimization services each period, consistent with the allocation objective. Annual variable performance- based payments are estimated at the inception in the transaction price using the expected value method, which takes into consideration historical experience, current contractual requirements, specific known market events and forecasted energy storage system performance patterns, and the Company recognizes such payments ratably using a time-based measure of progress of days elapsed over the term of the contract to the extent that it is probable that a significant reversal of the cumulative revenue recognized will not occur in a future period. At the end of each reporting period, the Company reassesses its estimate of the transaction price. The Company does not begin recognition of revenue until the energy storage system is live (i.e., provision of energy optimization services has commenced) or, as it relates to incentive payments, when approval has been received from the utility company, if later. Partnership Arrangements Partnership arrangements consist of promises to transfer inventory in the form of an energy storage system to a “solar plus storage” project developer and separately provide energy optimization services as described previously to the ultimate owner of the project after the developer completes the installation of the project. Under partnership arrangements, the Company’s customer is the solar plus storage project developer. The customer obtains legal title to along with ownership and control of the inventory upon delivery and the customer is responsible for the installation of the project. Once installation of the project is complete, the owner of the solar plus storage project provides energy to the end consumer through a separate contractual arrangement directly with the end consumer. The term for the Company’s contracts with customers under partnership arrangements generally ranges from 10 to 20 years. The Company determined the promise to deliver the inventory as a component of the solar plus storage project for which the customer is responsible to develop is a separate and distinct performance obligation from the promise to provide energy optimization services. The Company determines the transaction price at the outset of the arrangement, primarily based on the contractual payment terms dictated by the contract with the customer. Fees charged for the sale of inventory generally consist of fixed fees payable upon or shortly after successful delivery to the customer. Fees charged to customers for energy optimization services consist of recurring fixed monthly payments throughout the term of the contract. The Company is responsible for designing, procuring, delivering and ensuring the proper components are provided in accordance with the requirements of the contract. Although the inventory is purchased by the Company from a third-party manufacturer, the Company determined it obtains control of the inventory prior to delivery to the customer and is the principal in the arrangement. The Company is fully responsible for responding to and correcting any customer issues related to the delivery of the inventory. The Company holds title and assumes all risks of loss associated with the inventory until the customer accepts the inventory. The Company is primarily responsible for fulfilling the delivery of the inventory to the customer, assumes substantial inventory risks and has discretion in the pricing charged to the customer. The Company has not entered into any partnership arrangements where it is not the principal in the transaction. The Company allocates revenue between the hardware and energy storage services performance obligations based on the standalone selling price of each performance obligation. The standalone selling price for the hardware is established based on observable pricing. The standalone selling price for the energy optimization services is established using a residual value approach due to the significant variability in the services provided to each individual customer based on the specific requirements of each individual project and the lack of observable standalone sales of such services. The Company’s partnership arrangements do not contain a significant financing component. The Company transfers control of the inventory upon delivery and simultaneous transfer of title to the customer. The Company transfers control of its energy optimization services to its customers continuously throughout the term of the contract (a stand-ready obligation), which does not commence until the customer successfully completes the installation of the project. As a result, the time frame between when the Company transfers control of the inventory to the customer upon delivery is generally several months, and can be in excess of one year, before the Company is required to perform any subsequent energy optimization services. Revenue is recognized ratably as control of these services is transferred to its customers based on a time-based output measure of progress of days elapsed over the term of the contract, in an amount that reflects the consideration the Company expects to be entitled to in exchange for its services. In some partnership arrangements, the Company charges shipping fees for the inventory. The Company accounts for shipping as a fulfillment activity, since control transfers to the customer after the shipping is complete and includes such amounts within cost of revenue.
Business Combinations	Business Combinations The Company accounts for business acquisitions under ASC 805, Business Combinations . The total purchase consideration for an acquisition is measured as the fair value of the assets given, equity instruments issued and liabilities assumed at the acquisition date. Costs that are directly attributable to the acquisition are expensed as incurred. Identifiable assets (including intangible assets), liabilities assumed (including contingent liabilities) and noncontrolling interests in an acquisition are measured initially at their fair values at the acquisition date. The Company recognizes goodwill if the fair value of the total purchase consideration and any noncontrolling interests is in excess of the net fair value of the identifiable assets acquired and the liabilities assumed. The Company recognizes a bargain purchase gain within other income (expense), net, on the consolidated statement of operations if the net fair value of the identifiable assets acquired and the liabilities assumed is in excess of the fair value of the total purchase consideration and any noncontrolling interests. The Company includes the results of operations of the acquired business in the consolidated financial statements beginning on the acquisition date.
Internal-use software	Internal-use softwareThe Company capitalizes costs incurred in the development of internal-use software during the application development stage. Costs related to preliminary project activities and post-implementation activities are expensed as incurred. Capitalized internal-use software is amortized on a straight-line basis over the estimated useful life of the software once it is ready for its intended use.
Finite-lived Intangible Assets	Finite-lived Intangible Assets Finite-lived intangible assets consist of developed technology acquired in a business combination. Finite-lived intangible assets acquired in business combinations are initially recorded at fair value and subsequently presented net of accumulated
Impairment of Long-Lived Assets	Impairment of Long-Lived Assets The Company reviews its long-lived assets, which primarily consist of energy storage systems, right-of- use assets, and finite-lived intangible assets for impairment whenever events or changes in circumstances indicate that the carrying amount of an asset may not be recoverable or that the useful life is shorter than originally estimated. Recoverability of assets is measured by comparing the carrying amount of an asset to future undiscounted net cash flows expected to be generated by the asset over its remaining useful life. If such assets are impaired, the impairment recognized is measured by the amount by which the carrying amount of the assets exceeds the fair value of the assets. If the useful life is shorter than originally estimated, the Company depreciates or amortizes the remaining carrying value over the revised shorter useful life. Assets to be disposed of by sale are reflected at the lower of their carrying amount or fair value less cost to sell.
Leases	Leases The Company determines if an arrangement is or contains a lease at inception by assessing whether the arrangement contains an identified asset and whether it has the right to control the identified asset. Right-of-use (“ROU”) assets represent the Company’s right to use an underlying asset for the lease term and lease liabilities represent the Company’s obligation to make lease payments arising from the lease. The classification of the Company’s leases as operating or finance leases along with the initial measurement and recognition of the associated ROU assets and lease liabilities is performed at the lease commencement date. The measurement of ROU assets and lease liabilities is based on the present value of future lease payments over the lease term. The ROU asset also includes the effect of any lease payments made prior to or on lease commencement and excludes lease incentives and initial direct costs incurred, as applicable. As the implicit rate in the Company’s leases is generally unknown, the Company uses its incremental borrowing rate based on the information available at the lease commencement date in determining the present value of future lease payments. The Company considers its credit risk, term of the lease, total lease payments and adjusts for the impacts of collateral, as necessary, when calculating its incremental borrowing rates. The lease terms may include options to extend or terminate the lease when it is reasonably certain the Company will exercise any such options. Rent expense for the Company’s operating leases is recognized on a straight-line basis over the lease term. Variable lease payments are recorded as an expense in the period incurred. The Company has elected to not separate lease and non-lease components for any leases within its existing classes of assets and, as a result, accounts for any lease and non-lease components as a single lease component. The Company has also elected to not apply the recognition requirement to any leases within its existing classes of assets with a term of 12 months or less.
Convertible Preferred Stock Warrant Liabilities	Convertible Preferred Stock Warrant Liabilities The Company evaluates whether its warrants for shares of convertible redeemable preferred stock are freestanding financial instruments that obligate the Company to redeem the underlying preferred stock at some point in the future and determined that each of its outstanding warrants for preferred stock are liability classified. The warrants are subject to re-measurement at each balance sheet date, and any change in fair value is recognized in the change in fair value of warrants and embedded derivatives in the consolidated statements of operations. As discussed in Note 13 - Warrants , upon effectiveness of the Merger, substantially all of the outstanding convertible preferred stock warrants were converted into shares of common stock of Stem. As such, the associated warrant liability was reclassified to additional paid-in-capital upon the Merger and was no longer an outstanding Level 3 financial instrument as of December 31, 2021.
Common Stock Warrants	Common Stock Warrants The Company evaluates common stock warrants under ASC 815-40, Derivatives and Hedging—Contracts in Entity’s Own Equity. The Company assesses whether common stock warrants are freestanding financial instruments and whether they meet the criteria to be classified in stockholders’ equity, or classified as a liability. Where common stock warrants do not meet the conditions to be classified in equity, the Company assesses whether they meet the definition of a liability under ASC 815. As indicated in Note 13 - Warrants , a
Asset Retirement Obligations	Asset Retirement Obligations The Company recognizes a liability for the fair value of asset retirement obligations (“ARO”) associated with its energy storage systems in the period in which there is a legal obligation associated with the retirement of such assets and the amount can be reasonably estimated. The associated asset retirement costs are capitalized as part of the carrying amount of the energy storage systems and depreciated over the asset’s remaining useful life. This liability includes costs related to the removal of its energy storage systems at the conclusion of each respective customer contract. Subsequent to initial measurement, the asset retirement liability is accreted each period and such accretion is recognized as an expense in the consolidated statements of operations. If there are changes in the estimated amount or timing of cash flows, a revision is recorded to both the asset retirement obligation and the asset retirement capitalized cost.
Financing Obligations	Financing Obligations The Company has formed various SPEs to finance the development and construction of its energy storage systems. These SPEs, which are structured as limited liability companies, obtain financing in the form of large upfront payments from outside investors and purchase energy storage systems from the Company under master purchase agreements. The Company accounts for the large upfront payments received from the fund investor as a borrowing by recording the proceeds received as a financing obligation, which will be repaid through host customer payments and incentives received from the utilities that will be received by the investor. The financing obligation is non-recourse once the associated energy storage systems have been placed in-service and the associated customer arrangements have been assigned to the SPE. However, the Company is responsible for any warranties, performance guarantees, accounting, performance reporting, and all other costs associated with the operation of the energy storage systems. Despite such energy storage systems being legally sold to the SPEs, the Company recognizes host customer payments and incentives as revenue during the period as discussed in Note 3 - Revenue . The amounts received by the fund investor from customer payments and incentives are recognized as interest using the effective interest method, and the balance is applied to reduce the financing obligation. The effective interest rate is the interest rate that equates the present value of the cash amounts to be received by a fund investor in relation to the underlying Projects with the present value of the cash amounts paid by the investor to the Company, adjusted for any payments made by the Company.
Fair Value of Financial Instruments	Fair Value of Financial Instruments Assets and liabilities recorded at fair value in the consolidated financial statements are categorized based upon the level of judgment associated with the inputs used to measure their fair value. The fair value of the Company’s financial assets and liabilities reflects management’s estimate of amounts that the Company would have received in connection with the sale of the assets or paid in connection with the transfer of the liabilities in an orderly transaction between market participants at the measurement date. In connection with measuring the fair value of its assets and liabilities, the Company seeks to maximize the use of observable inputs (market data obtained from independent sources) and to minimize the use of unobservable inputs (internal assumptions about how market participants would price assets and liabilities). Hierarchical levels which are directly related to the amount of subjectivity associated with the inputs to the valuation of these assets or liabilities are as follows: Level 1 — Unadjusted quoted prices in active markets for identical assets or liabilities that the Company has the ability to access as of the measurement date. Level 2 — Inputs other than quoted prices included within Level 1 that are directly observable for the asset or liability or indirectly observable through corroboration with observable market data. Level 3 — Unobservable inputs for the asset or liability only used when there is little, if any, market activity for the asset or liability at the measurement date. This hierarchy requires the Company to use observable market data, when available, and to minimize the use of unobservable inputs when determining fair value. Assets and liabilities measured at fair value are classified in their entirety Financial assets and liabilities held by the Company measured at fair value on a recurring basis as of December 31, 2021 and 2020,
Cost of Revenue	Cost of Revenue Cost of Hardware Revenue Cost of revenue related to the sale of hardware includes the cost of the hardware sold to project developers, which generally includes the cost to purchase the hardware from a manufacturer, shipping, and other costs required to fulfill the Company’s obligation to deliver the hardware to the customer location. Cost of revenue may also include any impairment of hardware held in inventory for sale to a customer. Cost of revenue related to the sale of hardware is recognized when the delivery of the hardware is completed. Cost of Service Revenue Cost of revenue related to energy optimization services includes depreciation of the cost of energy storage systems associated with long-term host customer contracts, which includes capitalized fulfillment costs, such as installation services, permitting and other related costs. Cost of revenue may also include any impairment of energy storage systems along with energy storage system maintenance costs associated with the ongoing services provided to customers and other amounts not qualifying for capitalization pursuant to the Company’s internal use software capitalization policy. Cost of revenue is recognized as the energy optimization and other supporting services are provided to the Company’s customers throughout the term of the contract.
Sales and Marketing	Sales and MarketingSales and marketing expense consists primarily of payroll and other related personnel costs, including stock-based compensation, employee benefits, and travel for the Company’s sales & marketing department. These costs are recognized in the period incurred.
Research and Development	Research and Development Research and development expense consists primarily of payroll and other related personnel costs for engineers and third parties engaged in the design and development of products, third-party software, and technologies, including salaries, bonus and stock-based compensation expense, project material costs, services, and depreciation. The Company expenses research and development costs as they are incurred.
General and Administrative	General and Administrative General and administrative expense consists of payroll and other related personnel costs, including salaries, bonuses and stock-based compensation for executive management, legal, finance, and others. In addition, general and administrative expense includes fees for professional services and occupancy costs.
Stock Based Compensation	Stock-Based CompensationThe Company recognizes stock-based compensation expense related to employees over the requisite service period based on the grant-date fair value of the awards. The fair value of options granted is estimated using the Black-Scholes option valuation model. The Company recognizes the grant-date fair value of an award as compensation expense on a straight-line basis over the requisite service period, which typically corresponds to the vesting period for the award. The Company elects to account for forfeitures as they occur and, upon forfeiture of an award prior to vesting, the Company reverses any previously recognized compensation expense related to that award.
Income Taxes	Income Taxes The Company uses the asset and liability method of accounting for income taxes based on ASC 740, Accounting for Income Taxes . Under the asset and liability method, deferred tax assets and liabilities are recognized for the future tax consequences attributable to differences between financial statement carrying amounts and the tax basis of existing assets and liabilities. The Company records a valuation allowance to reduce tax assets to an amount for which realization is more likely than not. There are certain charges that are not deductible for tax purposes. In evaluating the ability to recover its deferred income tax assets, the Company considers all available positive and negative evidence, including its operating results, ongoing tax planning, and forecasts of future taxable income on a jurisdiction-by-jurisdiction basis. In the event the Company determines that it would be able to realize its deferred income tax assets in the future in excess of their net recorded amount, it would make an adjustment to the valuation allowance that would reduce the provision for income taxes. Conversely, in the event that all or part of the net deferred tax assets are determined not to be realizable in the future, an adjustment to the valuation allowance would be charged to earnings in the period such determination is made. The Company recognizes the tax benefit from uncertain tax positions in accordance with GAAP, which prescribes a recognition threshold and measurement attribute for the financial statement recognition and measurement of uncertain tax positions taken or expected to be taken in the Company’s tax return. No liability related to uncertain tax positions has been recognized in the financial statements.
Foreign Currency Translation	Foreign Currency Translation The Company’s foreign subsidiaries financial position and results of operations are measured using the local currency as the functional currency. The functional currency is the currency of the primary economic environment in which an entity’s operations are conducted. Assets and liabilities of foreign subsidiaries are translated at exchange rates in effect as of the balance sheet date. Revenues and expenses are translated at average exchange rates in effect during the year. Translation adjustments are recorded within accumulated other comprehensive loss, a separate component of stockholders’ equity (deficit).
Net Loss Per Share Attributable to Common Stockholders	Net Loss Per Share Attributable to Common Stockholders Basic net loss per share attributable to common stockholders is calculated by dividing the net loss attributable to common stockholders by the weighted-average number of shares of common stock outstanding for the period, without consideration for potential dilutive securities. Diluted net loss per share is computed by dividing the net loss attributable to common stockholders by the weighted- average number of common shares and common share equivalents of potentially dilutive securities outstanding for the period. For purposes of the diluted net loss per share calculation, convertible notes, warrants, restricted stock units (“RSUs”), and common stock options are considered to be potentially dilutive securities. As the Company was in a net loss position for the years ended December 31, 2021, 2020, and 2019, diluted net loss per share attributable to common stockholders is the same as basic net loss per share attributable to common stockholders because the effects of potentially dilutive securities are antidilutive.
Recently Adopted Accounting Standards And Recently Issued Accounting Standards	Recently Adopted Accounting Standards In August 2018, the FASB issued ASU 2018-15, Intangibles — Goodwill and Other — Internal-Use Software (Subtopic 350-40): Customer’s Accounting for Implementation Costs Incurred in a Cloud Computing Arrangement That Is a Service Contract (“ASU 2018-15”). The intent of this pronouncement is to align the requirements for capitalizing implementation costs incurred in a cloud computing arrangement that is a service contract with the requirements for capitalizing implementation costs incurred to develop or obtain internal-use software as defined in ASC 350-40. Under ASU 2018-15, the capitalized implementation costs related to a cloud computing arrangement will be amortized over the term of the arrangement and all capitalized implementation amounts will be required to be presented in the same line items of the financial statements as the related hosting fees. ASU 2018-15 is effective for public and private companies’ fiscal years beginning after December 15, 2019, and December 15, 2020, respectively, and interim periods within those fiscal years, with early adoption permitted. The Company adopted ASU 2018-15 as of January 1, 2021. The adoption did not have a material effect on the Company’s consolidated financial statements. In December 2019, the FASB issued ASU 2019-12, Income Taxes (Topic 740): Simplifying the Accounting for Income Taxes (“ASU 2019-12”). ASU 2019-12 removes certain exceptions to the general principles in Topic 740 and also clarifies and amends existing guidance to improve consistent application. ASU 2019-12 was effective for public entities for interim and annual periods beginning after December 15, 2020, with early adoption permitted. ASU 2019-12 will be effective for private entities for annual periods beginning after December 15, 2021, and interim periods beginning after December 15, 2020, with early adoption permitted. The Company adopted ASU 2019-12 effective May 1, 2021. The adoption of this standard did not have a material impact on the Company's consolidated financial statements. Recently Issued Accounting Standards The Company will adopt ASU 2020-06 Debt—Debt with Conversion and Other Options (Subtopic 470-20) and Derivatives and Hedging—Contracts in Entity’s Own Equity (Subtopic 815-40): Accounting for Convertible Instruments and Contracts in an Entity’s Own Equity , effective January 1, 2022 using the modified retrospective approach. As a result of the adoption of ASU 2020-06, the 2028 Convertible Notes will no longer bifurcated into separate liability and equity components in the March 31, 2022 condensed consolidated balance sheet. Rather, the $460.0 million principal amount of the Company’s 2028 Convertible Notes will be classified only as a liability prospectively in the balance sheet. Upon adoption of ASU 2020-06, an adjustment will be recorded to the convertible notes liability component, equity component (additional paid-in-capital) and retained earnings. The cumulative effect of the change will be recognized as an adjustment to the opening balance of retained earnings at the date of adoption. The comparative information will not restated and will continue to be presented according to accounting standards in effect for those periods. The adjustment will be calculated based on the carrying amount of the 2028 Convertible Notes as if it had always been treated only as a liability. Interest expense recognized in future periods will be reduced as a result of accounting for the convertible debt instrument as a single liability measured at its amortized cost. In June 2016, the FASB issued ASU 2016-13, Financial instruments — Credit Losses (Topic 326): Measurement of Credit Losses on Financial Instruments , and subsequent related ASUs, which amends the guidance on the impairment of financial instruments by requiring measurement and recognition of expected credit losses for financial assets held. This ASU is effective for public and private companies’ fiscal years, and for interim periods within those fiscal years, beginning after December 15, 2019, and December 15, 2022, respectively. As the Company is no longer an emerging growth company as of January 1, 2022, the Company plans to adopt ASU 2016-13 effective on such date, utilizing the modified retrospective transition method. The Company believes that adoption of ASU 2016-13 will not have a material impact on the Company’s consolidated financial statements. In October 2021, the FASB issued ASU 2021-08, Business Combinations (Topic 805): Accounting for Contract Assets and Contract Liabilities from Contracts with Customers . Under ASU 2021-08, an acquirer must recognize and measure contract assets and contract liabilities acquired in a business combination in accordance with Topic 606. The guidance is effective for interim and annual periods beginning after December 15, 2022, with early adoption permitted. As indicated in Note 21 - Subsequent Events , the Company completed the acquisition of AlsoEnergy on February 1, 2022. Therefore, the Company plans to adopt ASU 2021-08 on a prospective basis effective January 1, 2022 and is currently assessing the effect, if any, the guidance will have on the Company's consolidated financial statements.

BUSINESS (Tables)

BUSINESS (Tables)	12 Months Ended
	Dec. 31, 2021
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Schedule Of Reverse Recapitalization	On April 28, 2021, shareholders of STPK approved the Merger, under which Stem received approximately $550.3 million, net of fees and expenses as follows (in thousands): Recapitalization Cash — STPK trust and working capital cash $ 383,383 Cash — PIPE (as described below) 225,000 Less: transaction costs and advisory fees paid (58,061) Merger and PIPE financing $ 550,322

SUMMARY OF SIGNIFICANT ACCOUN_3

SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES (Tables)	12 Months Ended
	Dec. 31, 2021
Accounting Policies [Abstract]
Schedule of Error Corrections and Prior Period Adjustments	The following table presents the amount of the errors identified for energy storage systems, net and contract origination costs, net as of the end of each period, and the amounts and periods in which the errors related to cost of service revenue and sales and marketing originated (in millions): (overstatement)/understatement Year Ended December 31, 2020 2019 Periods prior to 2019 Energy storage systems, net $ (1.7) $ (1.5) $ (0.9) Contract origination costs, net $ (1.1) $ (0.3) $ (0.1) Cost of service revenue $ 0.2 $ 0.6 $ 0.9 Sales and marketing $ 0.8 $ 0.2 $ 0.1 The Company corrected the out of period errors in the quarter ended December 31, 2021. The impact of the out-of-period correction for the quarter ended December 31, 2021 included corrections for the prior quarterly periods presented below. The impact to the quarter ended December 31, 2021, was an increase of $4.2 million to net loss, increase to cost of service revenue of $1.8 million and increase to sales and marketing expenses of $2.4 million. The following table presents the amounts of the errors identified for energy storage systems, net and contract origination costs, net as of the end of each period, as well as the quarterly periods in which the errors related to cost of service revenue and sales and marketing originated (in millions): (overstatement)/understatement Quarter ended September 30, 2021 Quarter ended June 30, 2021 Quarter ended March 31, 2021 Energy storage systems, net $ (1.8) $ (1.7) $ (1.7) Contract origination costs, net $ (2.4) $ (1.6) $ (1.4) Cost of service revenue $ 0.1 $ — $ — Sales and marketing $ 0.8 $ 0.2 $ 0.3
Summary of Significant Customers	For each significant customer, revenue as a percentage of total revenue and accounts receivable as a percentage of total accounts receivable are as follows: Accounts Receivable Revenue December 31, Year Ended December 31, 2021 2020 2021 2020 2019 Customers: Customer A 23 % * 11 % * * Customer B 15 % * 10 % 12 % * Customer C 13 % 17 % 10 % 25 % * Customer D * 30 % * * * Customer E * 20 % * * * *Total less than 10% for the respective period

REVENUE (Tables)

REVENUE (Tables)	12 Months Ended
	Dec. 31, 2021
Revenue from Contract with Customer [Abstract]
Disaggregation of Revenue	The following table provides information on the disaggregation of revenue as recorded in the consolidated statements of operations (in thousands): Year ended December 31, 2021 2020 2019 Partnership hardware and service revenue $ 107,135 $ 20,713 $ 4,076 Host customer service revenue 20,236 15,594 13,476 Total revenue $ 127,371 $ 36,307 $ 17,552
Remaining Performance Obligations	As of December 31, 2021, the Company had $217.8 million of remaining performance obligations, and the approximate percentages expected to be recognized as revenue in the future are as follows (in thousands, except percentages): Total remaining Percent Expected to be Recognized as Revenue Less than Two to Greater than Service revenue $ 169,758 12 % 50 % 38 % Hardware revenue 48,039 100 % — % — % Total revenue $ 217,797
Contract Balances	The following table presents the changes in the deferred revenue balance (in thousands): 2021 2020 2019 Beginning balance as of Beginning balance as of January 1, $ 52,410 $ 20,728 $ 11,859 Upfront payments received from customers 89,951 40,481 6,698 Upfront or annual incentive payments received 6,614 8,015 8,240 Revenue recognized related to amounts that were included in beginning balance of deferred revenue (33,585) (9,764) (4,830) Revenue recognized related to deferred revenue generated during the period (77,947) (7,050) (1,239) Ending balance as of Ending balance as of December 31, $ 37,443 $ 52,410 $ 20,728

SHORT-TERM INVESTMENTS (Tables)

SHORT-TERM INVESTMENTS (Tables)	12 Months Ended
	Dec. 31, 2021
Investments, Debt and Equity Securities [Abstract]
Schedule of Short-Term Investments	The following tables summarize the estimated fair value of the Company’s cash equivalents and debt securities and the gross unrealized holding gains and losses as of December 31, 2021 (in thousands): Amortized cost Unrealized gain Unrealized Loss Estimated Fair Value Assets Cash equivalents: Money market fund $ 127,261 $ — $ — $ 127,261 Total cash equivalents $ 127,261 $ — $ — $ 127,261 Debt securities: Corporate debt securities $ 42,174 $ 11 $ (52) $ 42,133 Commercial paper 20,743 — — 20,743 U.S. government bonds 86,265 — (135) 86,130 Certificate of deposits 21,501 6 — 21,507 Other 2,500 — (5) 2,495 Total debt securities $ 173,183 $ 17 $ (192) $ 173,008 Classified as: Cash equivalents $ 127,261 Short-term debt securities 173,008 Long-term debt securities —

FAIR VALUE MEASUREMENTS (Tables

FAIR VALUE MEASUREMENTS (Tables)	12 Months Ended
	Dec. 31, 2021
Fair Value Disclosures [Abstract]
Schedule of Financial Instruments Measured at Fair Value	The following table provides the financial instruments measured at fair value on a recurring basis (in thousands): December 31, 2021 Level 1 Level 2 Level 3 Total Assets Cash equivalents: Money market fund $ 127,261 $ — $ — $ 127,261 Debt securities Corporate debt securities — 42,133 — 42,133 Commercial paper — 20,743 — 20,743 U.S. government bonds — 86,130 — 86,130 Certificate of deposits — 21,507 — 21,507 Other — 2,495 — 2,495 Total financial assets $ 127,261 $ 173,008 $ — $ 300,269 December 31, 2020 Level 1 Level 2 Level 3 Total Assets Cash equivalents: Money market fund $ 67 $ — $ — $ 67 Liabilities Convertible preferred stock warrant liability $ — $ — $ 95,342 $ 95,342
Key Assumptions Used for Valuation	The key assumptions used for the valuation of the preferred stock warrant liabilities upon remeasurement were as follows: Year Ended December 31, 2021 Volatility 65.0 % Risk-free interest rate 0.1 % Expected term (in years) 1.5 Dividend yield — % Discount for lack of marketability 12.3 %
Schedule of Changes in Liability for Unobservable Inputs	The following table presents the changes in the liability for the Company’s warrants during the years ended December 31, 2021 and 2020 (in thousands): December 31, 2021 2020 Balance as of January 1, $ 95,342 $ 6,094 Changes in estimated fair value 488 85,623 Assumption of warrant liability upon Merger 302,556 — Issuance of warrants — 3,633 Conversion of warrants upon Merger (60,568) — Exchange of warrants (168,647) — Exercise of warrants (169,171) (8) Balance as of December 31, $ — $ 95,342

GOODWILL AND INTANGIBLE ASSET_2

GOODWILL AND INTANGIBLE ASSETS, NET (Tables)	12 Months Ended
	Dec. 31, 2021
Goodwill and Intangible Assets Disclosure [Abstract]
Schedule of Goodwill	Goodwill consists of the following (in thousands): December 31, 2021 2020 Goodwill $ 1,625 $ 1,625 Effect of foreign currency translation 116 114 Total goodwill $ 1,741 $ 1,739
Schedule of Intangible Assets	Intangible assets, net, consists of the following (in thousands): December 31, 2021 2020 Developed technology $ 500 $ 500 Internally developed software 29,706 22,545 Intangible assets 30,206 23,045 Less: Accumulated amortization (16,276) (10,993) Add: Currency translation adjustment 36 35 Total intangible assets, net $ 13,966 $ 12,087

LEASES (Tables)

LEASES (Tables)	12 Months Ended
	Dec. 31, 2021
Leases [Abstract]
Schedule of operating lease liabilities	As of December 31, 2021, future payments associated with the Company’s operating lease liabilities were as follows (in thousands): Operating Leases 2022 $ 1,818 2023 2,473 2024 2,239 2025 2,109 2026 2,172 Thereafter 4,937 Total lease payments 15,748 Less: imputed interest (2,325) Total operating lease liability future lease payments $ 13,423
Summary of lease information	Reported as of December 31, 2021 and 2020 (in thousands): December 31, 2021 2020 Current portion of operating lease liabilities included within other current liabilities $ 1,240 $ 333 Non-current portion of operating lease liabilities 12,183 57 Total $ 13,423 $ 390 The following summarizes additional information related to operating leases: December 31, 2021 2020 Weighted average remaining operating lease term (in years) 6.7 0.8 Weighted average discount rate 4.5 % 11.3 %

ASSET RETIREMENT OBLIGATION (Ta

ASSET RETIREMENT OBLIGATION (Tables)	12 Months Ended
	Dec. 31, 2021
Asset Retirement Obligation Disclosure [Abstract]
Summary of Asset Retirement Obligations	The information below details the asset retirement obligation for the years ended December 31, 2021 and 2020 as follows (in thousands): December 31, 2021 2020 Beginning balance at January 1, $ 4,137 $ 5,759 Asset retirement obligation — 771 Settlement of asset retirement obligation — (1,375) Retirement cost revaluation (231) (1,235) Accretion expense 229 217 Ending balance at December 31, $ 4,135 $ 4,137

ENERGY STORAGE SYSTEMS, NET (Ta

ENERGY STORAGE SYSTEMS, NET (Tables)	12 Months Ended
	Dec. 31, 2021
Property, Plant and Equipment [Abstract]
Schedule of Energy Storage Systems, Net	Energy storage systems, net, consists of the following (in thousands): December 31, 2021 December 31, 2020 Energy storage systems placed into service $ 143,592 $ 144,425 Less: accumulated depreciation (45,250) (33,389) Energy storage systems not yet placed into service 7,772 12,667 Total energy storage systems, net $ 106,114 $ 123,703

BALANCE SHEET COMPONENTS (Table

BALANCE SHEET COMPONENTS (Tables)	12 Months Ended
	Dec. 31, 2021
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Schedule of Inventory	Inventory consists of the following (in thousands): December 31, 2021 2020 Work in process inventory $ 20,582 $ 15,296 Batteries 2,138 5,547 Total inventory $ 22,720 $ 20,843
Schedule of Other Current Assets	Other current assets consist of the following (in thousands): December 31, 2021 2020 Deferred costs with suppliers $ 13,744 $ 6,204 Prepaid expenses 3,137 698 Utility program deposits 353 891 Due from related parties 213 123 Other 1,194 4 Total other current assets $ 18,641 $ 7,920
Schedule of Other Assets, Noncurrent	Other noncurrent assets consist of the following (in thousands): December 31, 2021 2020 Prepaid warranties and maintenance $ 15,991 $ 1,088 Receivable from SPEs (Note 16) 3,565 3,583 Deferred SPAC costs — 1,256 Self-generation incentive program deposits 940 1,036 Investment in VIEs 1,924 744 Revolver debt issuance costs — 73 Property and equipment, net 512 44 Other 1,599 458 Total other noncurrent assets $ 24,531 $ 8,282
Schedule of Accrued Liabilities	Accrued liabilities consist of the following (in thousands): December 31, 2021 2020 Accrued payables $ 25,062 $ 9,799 Accrued interest – notes payable 344 6,149 Other accrued liabilities 587 124 Total accrued liabilities $ 25,993 $ 16,072
Other Current Liabilities	Other current liabilities consist of the following (in thousands): December 31, 2021 2020 System advances $ 267 $ 640 Lease liabilities – current portion 1,240 333 Due to related parties 306 399 Other — 217 Total other current liabilities $ 1,813 $ 1,589

NOTES PAYABLE (Tables)

NOTES PAYABLE (Tables)	12 Months Ended
	Dec. 31, 2021
Debt Disclosure [Abstract]
Schedule of Outstanding Debt	The Company’s outstanding debt consisted of the following as of December 31, 2021 (in thousands): December 31, 2021 Outstanding principal $ 1,902 Unamortized discount (215) Carrying value of debt $ 1,687

CONVERTIBLE PROMISSORY NOTES (T

CONVERTIBLE PROMISSORY NOTES (Tables)	12 Months Ended
	Dec. 31, 2021
Debt Disclosure [Abstract]
Schedule Of Convertible Debt	These costs were allocated to the debt and equity components based on the allocation of the proceeds as follows (in thousands): Amount Equity Component Debt Component Initial Purchaser’s Debt Discount $ 12,420 $ 3,650 $ 8,770 Debt Issuance Costs 1,871 550 1,321 Total $ 14,291 $ 4,200 $ 10,091 The outstanding 2028 Convertible Notes balances as of December 31, 2021 , are summarized in the following table (in thousands): December 31, 2021 Debt Component Outstanding principal $ 460,000 Unamortized initial purchaser’s debt discount and debt issuance cost (143,458) Net carrying amount $ 316,542 The following table presents total interest expense recognized related to the 2028 Convertible Notes during the year ended December 31, 2021 (in thousands) : December 31, 2021 Cash interest expense Contractual interest expense $ 249 Non-cash interest expense Amortization of debt discount and debt issuance cost $ 1,812 Total interest expense $ 2,061

COMMON STOCK (Tables)

COMMON STOCK (Tables)	12 Months Ended
	Dec. 31, 2021
Equity [Abstract]
Common Stock Reserved For Issuance	The Company had reserved shares of common stock for issuance as follows: December 31, Shares reserved for warrants 23,673 Options issued and outstanding 8,766,466 Shares available for future issuance under equity incentive plan 20,844,788 Conversion of 2028 Convertible Notes 20,842,773 Total 50,477,700

STOCK-BASED COMPENSATION (Table

STOCK-BASED COMPENSATION (Tables)	12 Months Ended
	Dec. 31, 2021
Share-based Payment Arrangement [Abstract]
Summary of Activity Under the Plan	The following table summarizes the stock option activity for the period ended December 31, 2021: Number of Weighted- Weighted- Aggregate Balances as of December 31, 2020 51,379,939 $ 0.56 7.2 $ 46,516 Retroactive application of recapitalization (40,314,281) 2.05 — — Adjusted Balance as of December 31, 2020 11,065,658 2.61 7.2 46,516 Options granted 1,079,583 28.73 Options exercised (3,235,713) 1.64 Options forfeited (129,102) 15.18 Options expired (13,960) 0.53 Balances as of December 31, 2021 8,766,466 $ 6.01 7.1 $ 123,570 Options vested and exercisable — December 31, 2021 6,298,675 $ 2.61 6.4 $ 103,100
Schedule of Assumptions in Estimating Option Fair Value	The Company uses the Black-Scholes model for estimating the fair value of options granted. The weighted-average assumptions used in the Black-Scholes are as follows: December 31, 2021 2020 2019 Expected volatility 74.00 % 71.41 % 69.10 % Risk-free interest rate 1.06 % 0.49 % 2.47 % Expected term (years) 6.23 5.82 5.83 Dividend yield — — —
Schedule of Restricted Stock Activity	The following table summarizes the RSU activity for the period ended December 31, 2021: Number of Weighted- Balances as of December 31, 2020 — $ — RSUs granted 1,801,831 36.0 RSUs vested — — RSUs forfeited (2,154) 26.1 Balances as of December 31, 2021 1,799,677 36.0
Stock-based Compensation Expense	The following table summarizes stock-based compensation expense recorded in each component of operating expenses in the Company’s consolidated statements of operations and comprehensive loss (in thousands): Year Ended December 31, 2021 2020 2019 Sales and marketing $ 1,723 $ 396 $ 364 Research and development 2,367 1,211 901 General and administrative 9,456 2,935 266 Total stock-based compensation expense $ 13,546 $ 4,542 $ 1,531

SPECIAL PURPOSE ENTITIES (Table

SPECIAL PURPOSE ENTITIES (Tables)	12 Months Ended
	Dec. 31, 2021
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Schedule of Variable Interest Entities	The assets and liabilities of SCF 1 are comprised primarily of the following: December 31, 2021 2020 Energy storage systems, net $ 649 $ 1,463 Deferred revenue, current $ 283 $ 283 Deferred revenue, noncurrent $ 753 $ 1,047 Other liabilities $ 159 $ 239 December 31, 2021 and 2020 (in thousands): December 31, 2021 2020 Energy storage systems, net $ 92,426 $ 91,593 Deferred revenue, current $ 4,417 $ 3,713 Deferred revenue, noncurrent $ 10,835 $ 8,265 Other liabilities $ 3,586 $ 3,178
Schedule of Equity Method Investments	The following table summarizes additional information about the Company’s equity method investments, SPV II, SPV III, SPV IV and Copec: SPV II SPV III SPV IV COPEC Date formed January 23, 2015 June 7, 2016 June 30, 2017 March 24, 2020 Initial ownership % 49 % 50 % 50 % 49 % Stem’s interest 100% of Class A shares 100% of Class B shares 100% of Class B shares 100% of Class A shares Initial distributions: Class A 10% (Stem) 80% (Stem — 50%) 97.5 % To be determined Class B 90 % 20% (Stem — 100%) 2.5% (Stem) N/A As of December 31, 2021 and 2020 , the Company’s investment in its unconsolidated SPE’s, recorded within other noncurrent assets on the consolidated balance sheets, was as follows (in thousands): December 31, 2021 2020 Investment in SPV II $ — $ — Investment in SPV III 421 487 Investment in SPV IV 291 257 Copec 1,212 — Total equity method investments $ 1,924 $ 744 December 31, 2021 2020 Financing obligation, current portion $ 15,277 $ 14,914 Financing obligation, noncurrent $ 73,204 $ 73,128

NET LOSS PER SHARE (Tables)

NET LOSS PER SHARE (Tables)	12 Months Ended
	Dec. 31, 2021
Earnings Per Share [Abstract]
Schedule of Computation of Basic and Diluted Net Loss Per Share	The following table sets forth the computation of basic and diluted net loss per share attributable to common stockholders (in thousands, except share and per share amounts): Year Ended December 31, 2021 2020 2019 Numerator - Basic and Diluted: Net loss $ (101,211) $ (156,124) $ (59,414) Less: Deemed Dividend — (9,484) (5,353) Net loss attributable to common stockholders, basic and diluted (101,211) (165,608) (64,767) Denominator: Weighted-average number of shares outstanding used to compute net loss per share attributable to common stockholders, basic and diluted 105,561,139 40,064,087 42,811,383 Net loss per share attributable to common stockholders, basic and diluted $ (0.96) $ (4.13) $ (1.51)
Schedule of Potentially Dilutive Shares	The following potentially dilutive shares were not included in the calculation of diluted shares outstanding for the periods presented as the effect would have been anti-dilutive: December 31, 2021 2020 2019 Outstanding Pre-Merger Convertible Promissory Notes — 10,495,111 5,202,697 Outstanding 2028 Convertible Notes 15,730,390 — — Outstanding stock options 8,766,466 11,065,658 9,227,850 Outstanding warrants 23,673 10,832,616 7,672,810 Outstanding RSUs 1,799,677 — — Total 26,320,206 32,393,385 22,103,357

INCOME TAXES (Tables)

INCOME TAXES (Tables)	12 Months Ended
	Dec. 31, 2021
Income Tax Disclosure [Abstract]
Schedule of Income before Income Tax, Domestic and Foreign	The components of loss before provision for income taxes for the years ended December 31, 2021, 2020, and 2019 are as follows (in thousands): December 31, 2021 2020 2019 Domestic $ (101,211) $ (156,119) $ (59,408) Foreign — — — Loss before income taxes $ (101,211) $ (156,119) $ (59,408)
Schedule of Components of Income Tax Expense (Benefit)	The components of the provision for income tax expense for the years ended December 31, 2021, 2020, and 2019 are as follows (in thousands): December 31, 2021 2020 2019 Current: Federal $ — $ — $ — State — 5 6 Total current — 5 6 Deferred: Federal — — — State — — — Total deferred — — — Total provision for income taxes $ — $ 5 $ 6
Schedule of Effective Income Tax Rate Reconciliation	The effective tax rate of the Company’s provision (benefit) for income taxes differs from the federal statutory rate as follows: December 31, 2021 2020 2019 Statutory rate 21.00 % 21.00 % 21.00 % State tax 3.15 % 3.19 % 7.13 % Foreign income and withholding taxes 1.61 % 0.41 % 0.08 % Stock-based compensation 6.17 % (0.60) % (0.51) % Change in fair value of warrants 0.71 % (11.36) % 0.53 % Other (1.19) % — % (0.04) % Non-deductible interest expense (2.53) % (1.51) % (2.63) % Valuation allowance (28.92) % (11.13) % (25.56) % Total — % — % — % — %
Schedule of Deferred Tax Assets and Liabilities	Significant components of the Company’s deferred tax assets and liabilities as of December 31, 2021 and 2020 are as follows (in thousands): December 31, 2021 2020 Deferred tax assets: Net operating losses $ 92,160 $ 59,960 Tax credits 741 761 Depreciable assets 604 635 Operating lease liabilities 3,558 — Accruals and allowances 1,803 575 Stock-based compensation 1,359 83 Deferred revenue 24,734 27,962 Interest expense 1,209 — Other 3,989 3,035 Total gross deferred tax assets 130,157 93,011 Less: Valuation allowance (125,082) (91,315) Net deferred tax assets 5,075 1,696 Deferred tax liabilities: Amortization of asset retirement obligation (768) (944) Intangibles (862) (752) Right-of-use assets (3,445) — Total gross deferred tax liabilities (5,075) (1,696) Net deferred taxes $ — $ —

BUSINESS - Narrative (Details)

BUSINESS - Narrative (Details) $ / shares in Units, $ in Thousands	Feb. 01, 2022USD ($)	Nov. 22, 2021USD ($)	Apr. 28, 2021USD ($)$ / sharesshares	Dec. 31, 2021USD ($)$ / shares	Dec. 31, 2020USD ($)$ / shares	Dec. 31, 2019USD ($)	Apr. 27, 2021$ / shares
Description Of Merger [Abstract]
Proceeds received			$ 550,322
Preferred stock, par value (in dollars per share) | $ / shares				$ 0.0001	$ 0.0001		$ 0.00001
Common stock, par value (in dollars per share) | $ / shares				$ 0.0001	$ 0.0001		$ 0.000001
Exchange ratio			4.6432
Sale of stock, number of shares Issued in transaction (in shares) | shares			22,500,000
Sale of stock (in dollars per share) | $ / shares			$ 10
Sale of stock aggregate purchase price			$ 225,000
Net liabilities			$ 302,200
Liquidity And Going Concern [Abstract]
Cash and cash equivalents				$ 747,780	$ 6,942
Short-term investments				173,000
Accumulated deficit				509,052	407,841
Working capital				935,900
Debt financing coming due within the next 12 months				15,300
Increase of net loss				101,211	156,124	$ 59,414
Negative cash flows from operating activities				101,266	33,671	29,678
Proceeds from public exercises warrant				145,300
Proceeds from convertible notes				$ 446,827	$ 33,081	$ 63,250
AlsoEnergy, Inc | Subsequent Event
Liquidity And Going Concern [Abstract]
Percent of outstanding shares acquired	100.00%
Aggregate purchase price	$ 695,000
Cash percentage	75.00%
2028 Convertible Notes | Convertible Notes
Liquidity And Going Concern [Abstract]
Proceeds from convertible notes		$ 445,700
Energy Storage Systems
Description Of Business [Abstract]
Estimated useful life				10 years
Maximum | Energy Storage Systems
Description Of Business [Abstract]
Estimated useful life				20 years

BUSINESS - Schedule of Reverse

BUSINESS - Schedule of Reverse Recapitalization (Details) - USD ($) $ in Thousands	Apr. 28, 2021	Dec. 31, 2021
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Cash — STPK trust and working capital cash	$ 383,383
Cash — PIPE (as described below)	225,000
Less: transaction costs and advisory fees paid	(58,061)	$ (58,061)
Merger and PIPE financing	$ 550,322

SUMMARY OF SIGNIFICANT ACCOUN_4

SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - Narrative (Details)	3 Months Ended				12 Months Ended				36 Months Ended
	Dec. 31, 2021USD ($)	Sep. 30, 2021USD ($)	Jun. 30, 2021USD ($)	Mar. 31, 2021USD ($)	Dec. 31, 2021USD ($)segmentarrangement	Dec. 31, 2020USD ($)	Dec. 31, 2019USD ($)	Dec. 31, 2018USD ($)	Dec. 31, 2020USD ($)	Nov. 22, 2021USD ($)
Concentration Risk [Line Items]
Increase of net loss					$ 101,211,000	$ 156,124,000	$ 59,414,000
Cost of revenue					126,124,000	40,219,000	20,812,000
Sales and marketing					$ 19,950,000	14,829,000	17,462,000
Number of operating segments | segment					1
Allowance for doubtful accounts	$ 100,000				$ 100,000	100,000			$ 100,000
Deferred incremental costs of obtaining a contract					3,000,000	2,600,000
Amortization of contract costs	3,900,000				3,900,000	800,000	500,000		800,000
Impairment cost losses					$ 500,000	100,000	500,000
Finite-lived intangible asset, useful life					5 years
Amortization					$ 5,000,000	4,000,000	3,000,000
Number of types or revenue arrangements | arrangement					2
Accrual of interest and penalties for uncertain tax positions	0				$ 0	$ 0			0
Accounting Standards Update [Extensible Enumeration]					Accounting Standards Update 2020-06 [Member]
2028 Convertible Notes | Convertible Notes
Concentration Risk [Line Items]
Face amount										$ 460,000,000
Energy Storage Systems
Concentration Risk [Line Items]
Estimated useful life					10 years
Internally developed software
Concentration Risk [Line Items]
Finite-lived intangible asset, useful life					5 years
Host Customer Arrangements
Concentration Risk [Line Items]
Incentive period					5 years
Estimated benefit period					10 years
Minimum | Host Customer Arrangements
Concentration Risk [Line Items]
Contract term					5 years
Minimum | Partnership Arrangements
Concentration Risk [Line Items]
Contract term					10 years
Maximum | Energy Storage Systems
Concentration Risk [Line Items]
Estimated useful life					20 years
Maximum | Host Customer Arrangements
Concentration Risk [Line Items]
Contract term					10 years
Maximum | Partnership Arrangements
Concentration Risk [Line Items]
Contract term					20 years
Transfers control of inventory period					1 year
Accounts Receivable | Customer Concentration Risk | Customer A
Concentration Risk [Line Items]
Concentration risk, percentage					23.00%
Accounts Receivable | Customer Concentration Risk | Customer B
Concentration Risk [Line Items]
Concentration risk, percentage					15.00%
Accounts Receivable | Customer Concentration Risk | Customer C
Concentration Risk [Line Items]
Concentration risk, percentage					13.00%	17.00%
Accounts Receivable | Customer Concentration Risk | Customer D
Concentration Risk [Line Items]
Concentration risk, percentage						30.00%
Accounts Receivable | Customer Concentration Risk | Customer E
Concentration Risk [Line Items]
Concentration risk, percentage						20.00%
Revenue | Customer Concentration Risk | Customer A
Concentration Risk [Line Items]
Concentration risk, percentage					11.00%
Revenue | Customer Concentration Risk | Customer B
Concentration Risk [Line Items]
Concentration risk, percentage					10.00%	12.00%
Revenue | Customer Concentration Risk | Customer C
Concentration Risk [Line Items]
Concentration risk, percentage					10.00%	25.00%
Retroactive application of recapitalization
Concentration Risk [Line Items]
Increase of net loss	4,200,000								2,800,000
Cost of revenue	1,800,000	$ 100,000	$ 0	$ 0		$ 200,000	600,000	$ 900,000	1,700,000
Sales and marketing	$ 2,400,000	$ 800,000	$ 200,000	$ 300,000		$ 800,000	$ 200,000	$ 100,000	$ 1,100,000

SUMMARY OF SIGNIFICANT ACCOUN_5

SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - Time periods in errors originated (Details) - USD ($) $ in Thousands	3 Months Ended				12 Months Ended				36 Months Ended
	Dec. 31, 2021	Sep. 30, 2021	Jun. 30, 2021	Mar. 31, 2021	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2020
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Contract origination costs, net					$ 2,622	$ 2,552	$ 1,302
Cost of service revenue					126,124	40,219	20,812
Sales and marketing					$ 19,950	14,829	17,462
Retroactive application of recapitalization
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Energy storage systems, net		$ (1,800)	$ (1,700)	$ (1,700)		(1,700)	(1,500)	$ (900)
Contract origination costs, net		(2,400)	(1,600)	(1,400)		(1,100)	(300)	(100)
Cost of service revenue	$ 1,800	100	0	0		200	600	900	$ 1,700
Sales and marketing	$ 2,400	$ 800	$ 200	$ 300		$ 800	$ 200	$ 100	$ 1,100

REVENUE - Disaggregation of Rev

REVENUE - Disaggregation of Revenue (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Disaggregation of Revenue [Line Items]
Total revenue	$ 127,371	$ 36,307	$ 17,552
Partnership hardware and service revenue
Disaggregation of Revenue [Line Items]
Total revenue	107,135	20,713	4,076
Host customer service revenue
Disaggregation of Revenue [Line Items]
Total revenue	$ 20,236	$ 15,594	$ 13,476

REVENUE - Remaining Performance

REVENUE - Remaining Performance Obligations (Details) $ in Thousands	Dec. 31, 2021USD ($)
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Total remaining performance obligations	$ 217,797
Service revenue
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Total remaining performance obligations	169,758
Hardware revenue
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Total remaining performance obligations	$ 48,039
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2022-01-01 | Service revenue
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Percent Expected to be Recognized as Revenue	12.00%
Period expected to be recognized as revenue	1 year
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2022-01-01 | Hardware revenue
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Percent Expected to be Recognized as Revenue	100.00%
Period expected to be recognized as revenue	1 year
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2023-01-01 | Service revenue
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Percent Expected to be Recognized as Revenue	50.00%
Period expected to be recognized as revenue	4 years
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2023-01-01 | Hardware revenue
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Percent Expected to be Recognized as Revenue	0.00%
Period expected to be recognized as revenue	4 years
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2027-01-01 | Service revenue
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Percent Expected to be Recognized as Revenue	38.00%
Period expected to be recognized as revenue
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2027-01-01 | Hardware revenue
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Percent Expected to be Recognized as Revenue	0.00%
Period expected to be recognized as revenue

REVENUE - Contract Balances (De

REVENUE - Contract Balances (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Contract With Customer, Liability [Roll Forward]
Beginning balance	$ 52,410	$ 20,728	$ 11,859
Upfront payments received from customers	89,951	40,481	6,698
Upfront or annual incentive payments received	6,614	8,015	8,240
Revenue recognized related to amounts that were included in beginning balance of deferred revenue	(33,585)	(9,764)	(4,830)
Revenue recognized related to deferred revenue generated during the period	(77,947)	(7,050)	(1,239)
Ending balance	$ 37,443	$ 52,410	$ 20,728

SHORT-TERM INVESTMENTS (Details

SHORT-TERM INVESTMENTS (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020
Cash equivalents:
Amortized cost	$ 127,261
Cash equivalents	127,261
Debt securities:
Amortized cost	173,183
Unrealized gain	17
Unrealized Loss	(192)
Debt securities	173,008
Classified as:
Cash equivalents	127,261
Short-term debt securities	173,008	$ 0
Long-term debt securities	0
Other-than-temporary impairment losses	0
Corporate debt securities
Debt securities:
Amortized cost	42,174
Unrealized gain	11
Unrealized Loss	(52)
Debt securities	42,133
Commercial paper
Debt securities:
Amortized cost	20,743
Unrealized gain	0
Unrealized Loss	0
Debt securities	20,743
U.S. government bonds
Debt securities:
Amortized cost	86,265
Unrealized gain	0
Unrealized Loss	(135)
Debt securities	86,130
Certificate of deposits
Debt securities:
Amortized cost	21,501
Unrealized gain	6
Unrealized Loss	0
Debt securities	21,507
Other
Debt securities:
Amortized cost	2,500
Unrealized gain	0
Unrealized Loss	(5)
Debt securities	2,495
Money market fund
Cash equivalents:
Amortized cost	127,261
Cash equivalents	127,261
Classified as:
Cash equivalents	$ 127,261

FAIR VALUE MEASUREMENTS - Sched

FAIR VALUE MEASUREMENTS - Schedule of Financial Instruments Measured at Fair Value (Details) - USD ($) $ in Thousands	Dec. 31, 2021	Dec. 31, 2020
Cash equivalents:
Cash equivalents	$ 127,261
Debt securities
Debt securities	173,008
Corporate debt securities
Debt securities
Debt securities	42,133
Commercial paper
Debt securities
Debt securities	20,743
U.S. government bonds
Debt securities
Debt securities	86,130
Certificate of deposits
Debt securities
Debt securities	21,507
Other
Debt securities
Debt securities	2,495
Money market fund
Cash equivalents:
Cash equivalents	127,261
Fair Value, Recurring
Debt securities
Total financial assets	300,269
Fair Value, Recurring | Convertible preferred stock warrant liability
Liabilities
Convertible preferred stock warrant liability		$ 95,342
Fair Value, Recurring | Corporate debt securities
Debt securities
Debt securities	42,133
Fair Value, Recurring | Commercial paper
Debt securities
Debt securities	20,743
Fair Value, Recurring | U.S. government bonds
Debt securities
Debt securities	86,130
Fair Value, Recurring | Certificate of deposits
Debt securities
Debt securities	21,507
Fair Value, Recurring | Other
Debt securities
Debt securities	2,495
Fair Value, Recurring | Money market fund
Cash equivalents:
Cash equivalents	127,261	67
Level 1 | Fair Value, Recurring
Debt securities
Total financial assets	127,261
Level 1 | Fair Value, Recurring | Convertible preferred stock warrant liability
Liabilities
Convertible preferred stock warrant liability		0
Level 1 | Fair Value, Recurring | Corporate debt securities
Debt securities
Debt securities	0
Level 1 | Fair Value, Recurring | Commercial paper
Debt securities
Debt securities	0
Level 1 | Fair Value, Recurring | U.S. government bonds
Debt securities
Debt securities	0
Level 1 | Fair Value, Recurring | Certificate of deposits
Debt securities
Debt securities	0
Level 1 | Fair Value, Recurring | Other
Debt securities
Debt securities	0
Level 1 | Fair Value, Recurring | Money market fund
Cash equivalents:
Cash equivalents	127,261	67
Level 2 | Fair Value, Recurring
Debt securities
Total financial assets	173,008
Level 2 | Fair Value, Recurring | Convertible preferred stock warrant liability
Liabilities
Convertible preferred stock warrant liability		0
Level 2 | Fair Value, Recurring | Corporate debt securities
Debt securities
Debt securities	42,133
Level 2 | Fair Value, Recurring | Commercial paper
Debt securities
Debt securities	20,743
Level 2 | Fair Value, Recurring | U.S. government bonds
Debt securities
Debt securities	86,130
Level 2 | Fair Value, Recurring | Certificate of deposits
Debt securities
Debt securities	21,507
Level 2 | Fair Value, Recurring | Other
Debt securities
Debt securities	2,495
Level 2 | Fair Value, Recurring | Money market fund
Cash equivalents:
Cash equivalents	0	0
Level 3 | Fair Value, Recurring
Debt securities
Total financial assets	0
Level 3 | Fair Value, Recurring | Convertible preferred stock warrant liability
Liabilities
Convertible preferred stock warrant liability		95,342
Level 3 | Fair Value, Recurring | Corporate debt securities
Debt securities
Debt securities	0
Level 3 | Fair Value, Recurring | Commercial paper
Debt securities
Debt securities	0
Level 3 | Fair Value, Recurring | U.S. government bonds
Debt securities
Debt securities	0
Level 3 | Fair Value, Recurring | Certificate of deposits
Debt securities
Debt securities	0
Level 3 | Fair Value, Recurring | Other
Debt securities
Debt securities	0
Level 3 | Fair Value, Recurring | Money market fund
Cash equivalents:
Cash equivalents	$ 0	$ 0

FAIR VALUE MEASUREMENTS - Narra

FAIR VALUE MEASUREMENTS - Narrative (Details) - Convertible Notes - USD ($) $ / shares in Units, $ in Millions	Nov. 22, 2021	Dec. 31, 2021
Level 2
Debt Instrument [Line Items]
Outstanding principal		$ 447.8
2028 Convertible Notes
Debt Instrument [Line Items]
Face amount	$ 460
2028 Convertible Notes | Level 2
Debt Instrument [Line Items]
Outstanding principal	$ 324.8
Capped Call Options
Debt Instrument [Line Items]
Number of shares covered by capped calls (in shares)	15,730,390
Cap price (in dollars per share)	$ 49.6575

FAIR VALUE MEASUREMENTS - Key A

FAIR VALUE MEASUREMENTS - Key Assumptions Used for Valuation (Details)	Dec. 31, 2021
Volatility
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Measurement input	0.650
Risk-free interest rate
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Measurement input	0.001
Expected term (in years)
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Measurement input	1.5
Dividend yield
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Measurement input	0
Discount for lack of marketability
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Measurement input	0.123

FAIR VALUE MEASUREMENTS - Sch_2

FAIR VALUE MEASUREMENTS - Schedule of Changes in Liability for Unobservable Inputs (Details) - Warrant Liability - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning balance	$ 95,342	$ 6,094
Changes in estimated fair value	488	85,623
Assumption of warrant liability upon Merger	302,556	0
Issuance of warrants	0	3,633
Conversion of warrants upon Merger	(60,568)	0
Exchange of warrants	(168,647)	0
Exercise of warrants	(169,171)	(8)
Ending balance	$ 0	$ 95,342

GOODWILL AND INTANGIBLE ASSET_3

GOODWILL AND INTANGIBLE ASSETS, NET - Goodwill consists (Details) - USD ($) $ in Thousands	Dec. 31, 2021	Dec. 31, 2020
Goodwill and Intangible Assets Disclosure [Abstract]
Goodwill	$ 1,625	$ 1,625
Effect of foreign currency translation	116	114
Total goodwill	$ 1,741	$ 1,739

GOODWILL AND INTANGIBLE ASSET_4

GOODWILL AND INTANGIBLE ASSETS, NET - Intangible assets, net (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Acquired Finite-Lived Intangible Assets [Line Items]
Intangible assets	$ 30,206	$ 23,045
Less: Accumulated amortization	(16,276)	(10,993)
Add: Currency translation adjustment	36	35
Total intangible assets, net	13,966	12,087
Amortization expense for intangible assets	5,300	4,500	$ 3,100
Developed technology
Acquired Finite-Lived Intangible Assets [Line Items]
Intangible assets	500	500
Internally developed software
Acquired Finite-Lived Intangible Assets [Line Items]
Intangible assets	$ 29,706	$ 22,545

LEASES - Narrative (Details)

LEASES - Narrative (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Lessee, Lease, Description [Line Items]
Lessee renewal term	5 years
Operating lease rent expense	$ 1.3	$ 0.8	$ 1.2
Cash paid for operating lease liabilities	$ 0.5	$ 0.7	$ 0.9
Minimum
Lessee, Lease, Description [Line Items]
Lease term	3 years
Maximum
Lessee, Lease, Description [Line Items]
Lease term	8 years

LEASES - Operating Lease Liabil

LEASES - Operating Lease Liabilities (Details) - USD ($) $ in Thousands	Dec. 31, 2021	Dec. 31, 2020
Leases [Abstract]
2022	$ 1,818
2023	2,473
2024	2,239
2025	2,109
2026	2,172
Thereafter	4,937
Total lease payments	15,748
Less: imputed interest	(2,325)
Operating lease liability	$ 13,423	$ 390

LEASES - Summary of Lease Infor

LEASES - Summary of Lease Information (Details) - USD ($) $ in Thousands	Dec. 31, 2021	Dec. 31, 2020
Leases [Abstract]
Operating Lease, Liability, Current, Statement of Financial Position [Extensible Enumeration]	Other current liabilities (includes $306 and $399 due to related parties as of December 31, 2021 and December 31, 2020, respectively)	Other current liabilities (includes $306 and $399 due to related parties as of December 31, 2021 and December 31, 2020, respectively)
Current portion of operating lease liabilities included within other current liabilities	$ 1,240	$ 333
Lease liability, noncurrent	12,183	57
Total operating lease liability future lease payments	$ 13,423	$ 390
Weighted average remaining operating lease term (in years)	6 years 8 months 12 days	9 months 18 days
Weighted average discount rate	4.50%	11.30%

ASSET RETIREMENT OBLIGATION (De

ASSET RETIREMENT OBLIGATION (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020
Asset Retirement Obligation, Roll Forward Analysis [Roll Forward]
Beginning balance at January 1,	$ 4,137	$ 5,759
Asset retirement obligation	0	771
Settlement of asset retirement obligation	0	(1,375)
Retirement cost revaluation	(231)	(1,235)
Accretion expense	229	217
Ending balance at December 31,	$ 4,135	$ 4,137

ENERGY STORAGE SYSTEMS, NET - S

ENERGY STORAGE SYSTEMS, NET - Schedule of Energy Storage Systems, Net (Details) - USD ($) $ in Thousands	Dec. 31, 2021	Dec. 31, 2020
Property, Plant and Equipment [Line Items]
Less: accumulated depreciation	$ (45,250)	$ (33,389)
Total energy storage systems, net	106,114	123,703
Energy storage systems placed into service
Property, Plant and Equipment [Line Items]
Total energy storage systems, gross	143,592	144,425
Energy storage systems not yet placed into service
Property, Plant and Equipment [Line Items]
Total energy storage systems, gross	$ 7,772	$ 12,667

ENERGY STORAGE SYSTEMS, NET - N

ENERGY STORAGE SYSTEMS, NET - Narrative (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Property, Plant and Equipment [Abstract]
Depreciation expense	$ 14.4	$ 13.9	$ 9.7

BALANCE SHEET COMPONENTS - Inve

BALANCE SHEET COMPONENTS - Inventory (Details) - USD ($) $ in Thousands	Dec. 31, 2021	Dec. 31, 2020
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Work in process inventory	$ 20,582	$ 15,296
Batteries	2,138	5,547
Inventory, net	$ 22,720	$ 20,843

BALANCE SHEET COMPONENTS - Othe

BALANCE SHEET COMPONENTS - Other Current Assets (Details) - USD ($) $ in Thousands	Dec. 31, 2021	Dec. 31, 2020
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Deferred costs with suppliers	$ 13,744	$ 6,204
Prepaid expenses	3,137	698
Utility program deposits	353	891
Due from related parties	213	123
Other	1,194	4
Total other current assets	$ 18,641	$ 7,920

BALANCE SHEET COMPONENTS - Ot_2

BALANCE SHEET COMPONENTS - Other Noncurrent Assets (Details) - USD ($) $ in Thousands	Dec. 31, 2021	Dec. 31, 2020
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Prepaid warranties and maintenance	$ 15,991	$ 1,088
Receivable from SPEs	3,565	3,583
Deferred SPAC costs	0	1,256
Self-generation incentive program deposits	940	1,036
Total equity method investments	1,924	744
Net proceeds to pay cost	0	73
Property and equipment, net	512	44
Other	1,599	458
Other noncurrent assets	$ 24,531	$ 8,282

BALANCE SHEET COMPONENTS - Accr

BALANCE SHEET COMPONENTS - Accrued Liabilities (Details) - USD ($) $ in Thousands	Dec. 31, 2021	Dec. 31, 2020
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Accrued payables	$ 25,062	$ 9,799
Accrued interest – notes payable	344	6,149
Other accrued liabilities	587	124
Total accrued liabilities	$ 25,993	$ 16,072

BALANCE SHEET COMPONENTS - Ot_3

BALANCE SHEET COMPONENTS - Other Current Liabilities (Details) - USD ($) $ in Thousands	Dec. 31, 2021	Dec. 31, 2020
Organization, Consolidation and Presentation of Financial Statements [Abstract]
System advances	$ 267	$ 640
Current portion of operating lease liabilities included within other current liabilities	1,240	333
Due to related parties	306	399
Other	0	217
Total other current liabilities	$ 1,813	$ 1,589

NOTES PAYABLE - Revolving Loan

NOTES PAYABLE - Revolving Loan Due to SPE Member (Details) - Line of Credit - Revolving Loan Due To SPE Member - USD ($) $ in Millions	1 Months Ended
	Aug. 31, 2020	May 31, 2020	Apr. 30, 2017	Dec. 31, 2020	Jan. 01, 2020
Debt Instrument [Line Items]
Total capacity		$ 35			$ 45
Fixed interest rate, annual		14.00%			10.00%
Period threshold for interest rate		9 months
Percent of capacity usage for financing of hardware purchases	70.00%	85.00%	100.00%
Outstanding balance				$ 7.4

NOTES PAYABLE - Term Loan Due t

NOTES PAYABLE - Term Loan Due to SPE Member (Details) - Term Loan Due To SPE Member - Term Loan - USD ($) $ in Millions	1 Months Ended
	May 31, 2020	Jan. 01, 2020	Dec. 31, 2018
Debt Instrument [Line Items]
Face amount			$ 13.3
Fixed interest rate, annual		12.50%
Final balloon payment		$ 3
Repayment of debt	$ 5.9

NOTES PAYABLE - Term Loan Due_2

NOTES PAYABLE - Term Loan Due to Former Non-Controlling Interest Holder (Details) - USD ($) $ in Millions	1 Months Ended
	Apr. 30, 2021	May 31, 2020	Jun. 30, 2018	Dec. 31, 2020
Debt Instrument [Line Items]
Payment to acquire noncontrolling interest			$ 8.1
Term Loan Due To Former Non-Controlling Interest Holder | Term Loan
Debt Instrument [Line Items]
Fixed interest rate, quarterly			4500.00%
Fixed interest rate, annual			18.00%
Prepaid principal and interest		$ 1.5
Prepaid principal		$ 1
Warrants issued (in shares)		400,000
Unamortized discount		$ 0.2
Long-term debt securities				$ 5.8
Debt instrument, prepayment penalties	$ 2.6

NOTES PAYABLE - 2020 and 2021 C

NOTES PAYABLE - 2020 and 2021 Credit Agreements (Details) - Line of Credit - USD ($) $ in Millions	1 Months Ended
	Apr. 30, 2021	Jan. 31, 2021	May 31, 2020	Dec. 31, 2021	Dec. 31, 2020
2020 Credit Agreement
Debt Instrument [Line Items]
Proceeds from credit agreement			$ 25
Fixed interest rate, annual			12.00%
Fixed interest rate, paid in cash			8.00%
Fixed interest rate, added back to principal			4.00%
Outstanding balance					$ 25.6
Prepayment penalties	$ 1.4
2021 Credit Agreement
Debt Instrument [Line Items]
Proceeds from credit agreement		$ 1.8
Fixed interest rate, annual		5.45%
Outstanding balance				$ 1.9
Total capacity		$ 2.7

NOTES PAYABLE - Schedule of Out

NOTES PAYABLE - Schedule of Outstanding Debt (Details) - Notes Payable $ in Thousands	Dec. 31, 2021USD ($)
Debt Instrument [Line Items]
Outstanding principal	$ 1,902
Unamortized discount	(215)
Carrying value of debt	$ 1,687

CONVERTIBLE PROMISSORY NOTES -

CONVERTIBLE PROMISSORY NOTES - Narrative (Details) $ / shares in Units, $ in Thousands	Nov. 22, 2021USD ($)day$ / shares	Nov. 19, 2021USD ($)$ / shares	Apr. 28, 2021USD ($)shares	Jan. 31, 2021USD ($)	Dec. 31, 2021USD ($)	Dec. 31, 2020USD ($)	Dec. 31, 2019USD ($)
Debt Instrument [Line Items]
Proceeds from convertible notes					$ 446,827	$ 33,081	$ 63,250
Debt conversion, converted instrument, shares issued (in shares) | shares			10,921,548
Loss on extinguishment of debt					5,064	0	$ 0
Capped Call Options
Debt Instrument [Line Items]
Cost of capped calls		$ 66,700
Initial strike price (in dollars per share) | $ / shares		$ 29.2428
Cap price (in dollars per share) | $ / shares		$ 49.6575
Convertible Notes
Debt Instrument [Line Items]
Convertible notes payable					0	$ 67,600
Convertible Notes | Q1 2021 Convertible Notes
Debt Instrument [Line Items]
Proceeds from convertible notes				$ 1,100
Convertible Notes | Convertible Promissory Notes
Debt Instrument [Line Items]
Debt conversion, converted instrument, amount			$ 77,700
Debt instrument, increase, accrued interest			$ 7,700
Loss on extinguishment of debt					1,100
Convertible Notes | 2028 Convertible Notes
Debt Instrument [Line Items]
Proceeds from convertible notes	$ 445,700
Unamortized discount	12,420
Face amount	$ 460,000
Fixed interest rate, annual	0.50%
Conversion ratio	0.0341965
Conversion price (in dollars per share) | $ / shares	$ 29.2428
Redemption price, percentage	100.00%
Term	7 years
Debt issuance costs	$ 1,871
Effective interest rate	5.96%
Outstanding principal					$ 460,000
Equity component	$ 135,200
Convertible Notes | 2028 Convertible Notes | Debt Instrument, Redemption, Period One
Debt Instrument [Line Items]
Conversion price, percentage	130.00%
Convertible Notes | 2028 Convertible Notes | Debt Instrument, Redemption, Period Two
Debt Instrument [Line Items]
Threshold trading days | day	20
Convertible Notes | Capped Call Options
Debt Instrument [Line Items]
Cap price (in dollars per share) | $ / shares	$ 49.6575

CONVERTIBLE PROMISSORY NOTES _2

CONVERTIBLE PROMISSORY NOTES - Allocated To Debt And Equity Components Based (Details) - 2028 Convertible Notes - Convertible Notes - USD ($) $ in Thousands	Dec. 31, 2021	Nov. 22, 2021
Debt Instrument [Line Items]
Unamortized discount		$ 12,420
Debt issuance costs		1,871
Total	$ 143,458	14,291
Equity Component
Initial Purchaser’s Debt Discount		3,650
Debt Issuance Costs		550
Total		4,200
Debt Component
Initial Purchaser’s Debt Discount		8,770
Debt Issuance Costs		1,321
Total		$ 10,091

CONVERTIBLE PROMISSORY NOTES _3

CONVERTIBLE PROMISSORY NOTES - Outstanding 2028 Convertible Notes (Details) - Convertible Notes - 2028 Convertible Notes - USD ($) $ in Thousands	Dec. 31, 2021	Nov. 22, 2021
Debt Instrument [Line Items]
Outstanding principal	$ 460,000
Unamortized discount	(143,458)	$ (14,291)
Carrying value of debt	$ 316,542

CONVERTIBLE PROMISSORY NOTES _4

CONVERTIBLE PROMISSORY NOTES - Interest Expense Recognized Related to Convertible Note (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Debt Instrument [Line Items]
Non-cash interest expense, including interest expenses associated with debt issuance costs	$ 9,648	$ 10,044	$ 4,759
2028 Convertible Notes | Convertible Notes
Debt Instrument [Line Items]
Contractual interest expense	249
Non-cash interest expense, including interest expenses associated with debt issuance costs	1,812
Interest expense	$ 2,061

WARRANTS (Details)

WARRANTS (Details) - USD ($) $ / shares in Units, $ in Thousands	Sep. 20, 2021	Jun. 24, 2021	Apr. 28, 2021	Apr. 07, 2021	Aug. 20, 2020	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019	Jun. 25, 2021
Class of Warrant or Right [Line Items]
Warrants outstanding (in shares)			50,207,439
Conversion of securities into common stock (in shares)			2,759,970
(Gain) loss from fair value adjustment			$ (100,900)			$ (3,424)	$ 84,455	$ (1,493)
Conversion of securities into common stock			$ 60,600
Sale of stock, number of shares Issued in transaction (in shares)			22,500,000
Number of shares called from each warrant (in shares)					1
Exercise Price (in dollars per share)				$ 0.01
Number of shares called from exchange of warrants (in shares)				350,000
Warrants and rights outstanding					$ 302,600
Issued irrevocable notice redemption (in shares)	12,786,129
Cash net of broker fees						145,300
Issuance of common stock warrants for services				$ 9,200		$ 9,183
Legacy Stem Warrants
Class of Warrant or Right [Line Items]
Warrants outstanding (in shares)						23,673
Public Warrants
Class of Warrant or Right [Line Items]
Sale of stock, number of shares Issued in transaction (in shares)					12,786,168
Exercise Price (in dollars per share)	$ 11.50				$ 11.50
Number of shares called from exchange of warrants (in shares)	12,638,723
Warrants and rights outstanding					$ 185,900
Cash net of broker fees	$ 145,300
Net gain revaluation and redemption	134,900
Gain on redemption of warrants	$ 2,100
Private Warrants
Class of Warrant or Right [Line Items]
Warrants outstanding (in shares)						0			7,181,134
(Gain) loss from fair value adjustment		$ 52,000
Number of shares called from exchange of warrants (in shares)					7,181,134				4,683,349
Warrants and rights outstanding					$ 116,700

COMMON STOCK (Details)

COMMON STOCK (Details) - shares	Dec. 31, 2021	May 31, 2021	Dec. 31, 2020
Class of Stock [Line Items]
Reserved shares of common stock for issuance ( in shares)	50,477,700
Outstanding RSUs
Class of Stock [Line Items]
RSUs outstanding, ending of period (in shares)	1,799,677		0
2021 Equity Incentive Plan
Class of Stock [Line Items]
Reserved shares of common stock for issuance ( in shares)	23,722,254	23,722,254
2021 Equity Incentive Plan | Outstanding RSUs
Class of Stock [Line Items]
RSUs outstanding, ending of period (in shares)	1,801,831
Shares reserved for warrants
Class of Stock [Line Items]
Reserved shares of common stock for issuance ( in shares)	23,673
Options issued and outstanding
Class of Stock [Line Items]
Reserved shares of common stock for issuance ( in shares)	8,766,466
Shares available for future issuance under equity incentive plan
Class of Stock [Line Items]
Reserved shares of common stock for issuance ( in shares)	20,844,788
Conversion of 2028 Convertible Notes
Class of Stock [Line Items]
Reserved shares of common stock for issuance ( in shares)	20,842,773

STOCK-BASED COMPENSATION - Narr

STOCK-BASED COMPENSATION - Narrative (Details) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2021USD ($)$ / sharesshares	Dec. 31, 2020USD ($)$ / sharesshares	Dec. 31, 2019USD ($)$ / shares	May 31, 2021shares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Options outstanding (in shares) | shares	8,766,466	11,065,658
Reserved shares of common stock for issuance ( in shares) | shares	50,477,700
Options granted, weighted-average grant date fair value (in dollars per share) | $ / shares	$ 18.84	$ 3.79	$ 1.58
Options exercised, intrinsic value	$ 56,100	$ 1,100	$ 100
Shares issued from net settlement (in shares) | shares	1,054,594
Options converted from net settlement (in shares) | shares	1,648,463
Payments for taxes related to net share settlement of stock options	$ 12,622	0	0
Remaining unrecognized stock-based compensation expense	21,100
Total stock-based compensation expense	13,546	4,542	1,531
Research and development
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total stock-based compensation expense	2,367	$ 1,211	$ 901
Research and development | Internally developed software
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total stock-based compensation expense	$ 1,200
2009 Equity Incentive Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Options outstanding (in shares) | shares	7,754,811
2021 Equity Incentive Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Options outstanding (in shares) | shares	1,075,635
Reserved shares of common stock for issuance ( in shares) | shares	23,722,254			23,722,254
Stock Options
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Exercise price as a percentage of fair value	100.00%
Exercise price as a percentage of fair value for shareholders owning specified minimum amount	110.00%
Significant shareholder threshold used for determining exercise price	10.00%
Exercise period	10 years
Payments for taxes related to net share settlement of stock options	$ 12,600
Weighted average period for recognition of stock-based compensation expense	3 years 2 months 12 days
Stock Options | Share-based Payment Arrangement, Tranche One
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting percentage	25.00%
Vesting period	1 year
Stock Options | Share-based Payment Arrangement, Tranche Two
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting percentage	2.08%
Vesting period	3 years
RSU
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Right to receive, conversion ratio	1
Fair value of grants in period	$ 64,800
RSUs vested (in shares) | shares	0
Remaining unrecognized stock-based compensation expense	$ 56,500
Weighted average period for recognition of stock-based compensation expense	4 years 10 months 24 days
RSU | 2009 Equity Incentive Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting percentage	25.00%
Vesting period	4 years
RSU | 2021 Equity Incentive Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting percentage	20.00%
Vesting period	7 years

STOCK-BASED COMPENSATION - Opti

STOCK-BASED COMPENSATION - Option Activity (Details) - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020
Number of Options Outstanding
Options outstanding, beginning of period (in shares)	11,065,658
Options granted (in shares)	1,079,583
Options exercised (in shares)	(3,235,713)
Options forfeited (in shares)	(129,102)
Options expired (in shares)	(13,960)
Options outstanding, end of period (in shares)	8,766,466	11,065,658
Options vested and exercisable (in shares)	6,298,675
Weighted- Average Exercise Price Per Share
Options outstanding, weighted average exercise price (in dollars per share)	$ 6.01	$ 2.61
Options granted, weighted average exercise price (in dollars per share)	28.73
Options exercised, weighted average exercise price (in dollars per share)	1.64
Options forfeited, weighted average exercise price (in dollars per share)	15.18
Options expired, weighted average exercise price (in dollars per share)	0.53
Options vested and exercisable, weighted-average exercise price (in dollars per share)	$ 2.61
Share-based Compensation Arrangement by Share-based Payment Award, Options, Additional Disclosures [Abstract]
Weighted average remaining contractual life, options outstanding	7 years 1 month 6 days	7 years 2 months 12 days
Weighted average remaining contractual life, options vested and exercisable	6 years 4 months 24 days
Aggregate intrinsic value, options outstanding	$ 123,570	$ 46,516
Aggregate intrinsic value, options vested and exercisable	$ 103,100
Previously Reported
Number of Options Outstanding
Options outstanding, beginning of period (in shares)	51,379,939
Options outstanding, end of period (in shares)		51,379,939
Weighted- Average Exercise Price Per Share
Options outstanding, weighted average exercise price (in dollars per share)		$ 0.56
Share-based Compensation Arrangement by Share-based Payment Award, Options, Additional Disclosures [Abstract]
Weighted average remaining contractual life, options outstanding		7 years 2 months 12 days
Aggregate intrinsic value, options outstanding		$ 46,516
Retroactive application of recapitalization
Number of Options Outstanding
Options outstanding, beginning of period (in shares)	(40,314,281)
Options outstanding, end of period (in shares)		(40,314,281)
Weighted- Average Exercise Price Per Share
Options outstanding, weighted average exercise price (in dollars per share)		$ 2.05

STOCK-BASED COMPENSATION - Assu

STOCK-BASED COMPENSATION - Assumptions in Estimating Option Fair Value (Details) - Stock Options	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Expected volatility	74.00%	71.41%	69.10%
Risk-free interest rate	1.06%	0.49%	2.47%
Expected term (years)	6 years 2 months 23 days	5 years 9 months 25 days	5 years 9 months 29 days
Dividend yield	0.00%	0.00%	0.00%

STOCK-BASED COMPENSATION - RSU

STOCK-BASED COMPENSATION - RSU Activity (Details) - RSU - $ / shares	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020
Number of RSUs Outstanding
RSUs outstanding, ending of period (in shares)	1,799,677	0
RSUs granted (in shares)	1,801,831
RSUs vested (in shares)	0
RSUs forfeited (in shares)	(2,154)
Weighted- Average Grant Date Fair Value Per Share
RSUs outstanding, weighted average grant date fair value (in dollars per share)	$ 36	$ 0
RSUs granted, weighted average grant date fair value (in dollars per share)	36
RSUs vested, weighted average grant date fair value (in dollars per share)	0
RSUs forfeited, weighted average grant date fair value (in dollars per share)	$ 26.1

STOCK-BASED COMPENSATION - Stoc

STOCK-BASED COMPENSATION - Stock-Based Compensation Expense (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total stock-based compensation expense	$ 13,546	$ 4,542	$ 1,531
Sales and marketing
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total stock-based compensation expense	1,723	396	364
Research and development
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total stock-based compensation expense	2,367	1,211	901
General and administrative
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total stock-based compensation expense	$ 9,456	$ 2,935	$ 266

SPECIAL PURPOSE ENTITIES - Asse

SPECIAL PURPOSE ENTITIES - Assets and Liabilities of Consolidated VIE (Details) - USD ($) $ in Thousands	Dec. 31, 2021	Dec. 31, 2020
Variable Interest Entity [Line Items]
Energy storage systems, net	$ 106,114	$ 123,703
Deferred revenue, current portion	9,158	36,942
Deferred revenue, noncurrent	28,285	15,468
Variable Interest Entity, Primary Beneficiary
Variable Interest Entity [Line Items]
Energy storage systems, net	649	1,463
Deferred revenue, current portion	283	283
Deferred revenue, noncurrent	753	1,047
Other liabilities	$ 159	$ 239

SPECIAL PURPOSE ENTITIES - Narr

SPECIAL PURPOSE ENTITIES - Narrative (Details) $ in Millions	12 Months Ended			29 Months Ended
	Dec. 31, 2021USD ($)	Dec. 31, 2020USD ($)	Dec. 31, 2019USD ($)	Jun. 30, 2017company	Mar. 31, 2020service_station
Variable Interest Entity [Line Items]
Number of companies formed | company				3
Depreciation expense	$ 14.4	$ 13.9	$ 9.7
Variable Interest Entity, Not Primary Beneficiary
Variable Interest Entity [Line Items]
Interest expense	8.5	6.9	5.8
Revenues	16.9	12.8	8.8
Depreciation expense	12.8	11.8	7.1
SPV II, SPV III, And SPV IV | Variable Interest Entity, Not Primary Beneficiary
Variable Interest Entity [Line Items]
Earnings from equity method investments	$ 0.1	$ 0.1	$ 0.2
COPEC | Variable Interest Entity, Not Primary Beneficiary | CHILE
Variable Interest Entity [Line Items]
Number of service stations | service_station					650
COPEC | Variable Interest Entity, Not Primary Beneficiary | South America, Central America, And United States
Variable Interest Entity [Line Items]
Number of service stations | service_station					2,500

SPECIAL PURPOSE ENTITIES - Equi

SPECIAL PURPOSE ENTITIES - Equity Method Investments (Details) - Variable Interest Entity, Not Primary Beneficiary	Dec. 31, 2021	Dec. 31, 2020
SPV II
Variable Interest Entity [Line Items]
Initial ownership	49.00%
SPV II | Class A
Variable Interest Entity [Line Items]
Stem’s interest	100.00%
Distribution percentage, parent	10.00%
SPV II | Class B
Variable Interest Entity [Line Items]
Distribution percentage	90.00%
SPV III
Variable Interest Entity [Line Items]
Initial ownership		50.00%
SPV III | Class A
Variable Interest Entity [Line Items]
Distribution percentage	80.00%
Distribution percentage, parent	50.00%
SPV III | Class B
Variable Interest Entity [Line Items]
Stem’s interest	100.00%
Distribution percentage	20.00%
Distribution percentage, parent	100.00%
SPV IV
Variable Interest Entity [Line Items]
Initial ownership	50.00%
SPV IV | Class A
Variable Interest Entity [Line Items]
Distribution percentage	97.50%
SPV IV | Class B
Variable Interest Entity [Line Items]
Stem’s interest	100.00%
Distribution percentage, parent	2.50%
COPEC
Variable Interest Entity [Line Items]
Initial ownership	49.00%
COPEC | Class A
Variable Interest Entity [Line Items]
Stem’s interest	100.00%

SPECIAL PURPOSE ENTITIES - Inve

SPECIAL PURPOSE ENTITIES - Investment in Unconsolidated SPE (Details) - USD ($) $ in Thousands	Dec. 31, 2021	Dec. 31, 2020
Class of Warrant or Right [Line Items]
Total equity method investments	$ 1,924	$ 744
Variable Interest Entity, Not Primary Beneficiary
Class of Warrant or Right [Line Items]
Total equity method investments	1,924	744
SPV II | Variable Interest Entity, Not Primary Beneficiary
Class of Warrant or Right [Line Items]
Total equity method investments	0	0
SPV III | Variable Interest Entity, Not Primary Beneficiary
Class of Warrant or Right [Line Items]
Total equity method investments	421	487
SPV IV | Variable Interest Entity, Not Primary Beneficiary
Class of Warrant or Right [Line Items]
Total equity method investments	291	257
COPEC | Variable Interest Entity, Not Primary Beneficiary
Class of Warrant or Right [Line Items]
Total equity method investments	$ 1,212	$ 0

SPECIAL PURPOSE ENTITIES - Fina

SPECIAL PURPOSE ENTITIES - Financing Obligations Associated (Details) - USD ($) $ in Thousands	Dec. 31, 2021	Dec. 31, 2020
Variable Interest Entity [Line Items]
Financing obligation, current portion	$ 15,277	$ 14,914
Financing obligation, noncurrent	73,204	73,128
Variable Interest Entity, Not Primary Beneficiary
Variable Interest Entity [Line Items]
Financing obligation, current portion	15,277	14,914
Financing obligation, noncurrent	$ 73,204	$ 73,128

SPECIAL PURPOSE ENTITIES - Carr

SPECIAL PURPOSE ENTITIES - Carrying Value of Energy Storage System Assets (Details) - USD ($) $ in Thousands	Dec. 31, 2021	Dec. 31, 2020
Variable Interest Entity [Line Items]
Energy storage systems, net	$ 106,114	$ 123,703
Deferred revenue, current portion	9,158	36,942
Deferred revenue, noncurrent	28,285	15,468
Variable Interest Entity, Not Primary Beneficiary
Variable Interest Entity [Line Items]
Energy storage systems, net	92,426	91,593
Deferred revenue, current portion	4,417	3,713
Deferred revenue, noncurrent	10,835	8,265
Other liabilities	$ 3,586	$ 3,178

NET LOSS PER SHARE - Basic and

NET LOSS PER SHARE - Basic and diluted net loss per share (Details) - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Numerator - Basic and Diluted:
Net loss	$ (101,211)	$ (156,124)	$ (59,414)
Less: Deemed Dividend	0	(9,484)	(5,353)
Net income (loss) attributable to common stockholders, basic	(101,211)	(165,608)	(64,767)
Net income (loss) attributable to common stockholders, diluted	$ (101,211)	$ (165,608)	$ (64,767)
Denominator:
Weighted-average shares used in computing net loss per share attributable to common stockholders, basic (in shares)	105,561,139	40,064,087	42,811,383
Weighted-average number of shares outstanding used to compute net loss per share attributable to common stockholders, diluted (in shares)	105,561,139	40,064,087	42,811,383
Net loss per share attributable to common shareholders, basic (in dollars per share)	$ (0.96)	$ (4.13)	$ (1.51)
Net loss per share attributable to common shareholders, diluted (in dollars per share)	$ (0.96)	$ (4.13)	$ (1.51)

NET LOSS PER SHARE - Antidiluti

NET LOSS PER SHARE - Antidilutive securities (Details) - shares	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Potentially dilutive shares (in shares)	26,320,206	32,393,385	22,103,357
Outstanding Pre-Merger Convertible Promissory Notes
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Potentially dilutive shares (in shares)	0	10,495,111	5,202,697
Outstanding 2028 Convertible Notes
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Potentially dilutive shares (in shares)	15,730,390	0	0
Outstanding stock options
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Potentially dilutive shares (in shares)	8,766,466	11,065,658	9,227,850
Outstanding warrants
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Potentially dilutive shares (in shares)	23,673	10,832,616	7,672,810
Outstanding RSUs
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Potentially dilutive shares (in shares)	1,799,677	0	0

INCOME TAXES - Components Of In

INCOME TAXES - Components Of Income Before Income Taxes (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Income Tax Disclosure [Abstract]
Domestic	$ (101,211)	$ (156,119)	$ (59,408)
Foreign	0	0	0
Income (loss) before income taxes	$ (101,211)	$ (156,119)	$ (59,408)

INCOME TAXES - Narrative (Detai

INCOME TAXES - Narrative (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Income Tax Contingency [Line Items]
Income tax expense	$ 0	$ 5	$ 6
Valuation allowance	125,082	91,315
Uncertain tax positions	700	800
Domestic Tax Authority
Income Tax Contingency [Line Items]
NOL carryforwards	300,800	199,800
Domestic Tax Authority | Research Tax Credit Carryforward
Income Tax Contingency [Line Items]
Tax credit carryforward	700	700
State and Local Jurisdiction
Income Tax Contingency [Line Items]
NOL carryforwards	274,600	200,500
State and Local Jurisdiction | Research Tax Credit Carryforward
Income Tax Contingency [Line Items]
Tax credit carryforward	0	100
Tax credit carryforward, subject to expiration	700	700
Foreign Tax Authority
Income Tax Contingency [Line Items]
NOL carryforwards	$ 9,000	$ 0

INCOME TAXES - Components Of _2

INCOME TAXES - Components Of Income Tax Expense (Benefit) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Current:
Federal	$ 0	$ 0	$ 0
State	0	5	6
Total current	0	5	6
Deferred:
Federal	0	0	0
State	0	0	0
Total deferred	0	0	0
Income tax expense	$ 0	$ 5	$ 6

INCOME TAXES - Provision (Benef

INCOME TAXES - Provision (Benefit) Of Income Taxes Federal Statutory Rate (Details)	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Income Tax Disclosure [Abstract]
Statutory rate	21.00%	21.00%	21.00%
State tax	3.15%	3.19%	7.13%
Foreign income and withholding taxes	1.61%	0.41%	0.08%
Stock-based compensation	6.17%	(0.60%)	(0.51%)
Change in fair value of warrants	0.71%	(11.36%)	0.53%
Other	(1.19%)	0.00%	(0.04%)
Non-deductible interest expense	(2.53%)	(1.51%)	(2.63%)
Valuation allowance	(28.92%)	(11.13%)	(25.56%)
Total	0.00%	0.00%	0.00%

INCOME TAXES- Deferred Tax Asse

INCOME TAXES- Deferred Tax Assets And Liabilities (Details) - USD ($) $ in Thousands	Dec. 31, 2021	Dec. 31, 2020
Deferred tax assets:
Net operating losses	$ 92,160	$ 59,960
Tax credits	741	761
Depreciable assets	604	635
Operating lease liabilities	3,558	0
Accruals and allowances	1,803	575
Stock-based compensation	1,359	83
Deferred revenue	24,734	27,962
Interest expense	1,209	0
Other	3,989	3,035
Total gross deferred tax assets	130,157	93,011
Less: Valuation allowance	(125,082)	(91,315)
Net deferred tax assets	5,075	1,696
Deferred tax liabilities:
Amortization of asset retirement obligation	(768)	(944)
Intangibles	(862)	(752)
Right-of-use assets	(3,445)	0
Total gross deferred tax liabilities	(5,075)	(1,696)
Net deferred taxes	$ 0	$ 0

EMPLOYER RETIREMENT PLAN (Detai

EMPLOYER RETIREMENT PLAN (Details) - USD ($)	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Defined Contribution Plan Disclosure [Line Items]
Employer match amount	$ 0	$ 0	$ 0
Minimum
Defined Contribution Plan Disclosure [Line Items]
Defer compensation, percentage	1.00%
Maximum
Defined Contribution Plan Disclosure [Line Items]
Defer compensation, percentage	75.00%

SUBSEQUENT EVENTS (Details)

SUBSEQUENT EVENTS (Details) - Subsequent Event - AlsoEnergy, Inc $ in Millions	Feb. 01, 2022USD ($)
Subsequent Event [Line Items]
Percent of outstanding shares acquired	100.00%
Aggregate purchase price	$ 695
Cash percentage	75.00%
Common Stock
Subsequent Event [Line Items]
Share percentage	25.00%