Clean Energy Fuels (CLNE) 10-Q6 May 212021 Q1 Quarterly reportFinancial data

Company Profile

Document and Entity Information

Document and Entity Information - shares	3 Months Ended
Document and Entity Information - shares	Mar. 31, 2021	Apr. 30, 2021
Document and Entity Information
Document Type	10-Q
Document Quarterly Report	true
Document Transition Report	false
Document Period End Date	Mar. 31, 2021
Entity File Number	001-33480
Entity Registrant Name	CLEAN ENERGY FUELS CORP.
Entity Incorporation, State or Country Code	DE
Entity Tax Identification Number	33-0968580
Entity Address, Address Line One	4675 MacArthur Court, Suite 800
Entity Address, City or Town	Newport Beach
Entity Address, State or Province	CA
Entity Address, Postal Zip Code	92660
City Area Code	949
Local Phone Number	437-1000
Title of 12(b) Security	Common stock
Trading Symbol	CLNE
Security Exchange Name	NASDAQ
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Entity Filer Category	Accelerated Filer
Entity Small Business	false
Entity Emerging Growth Company	false
Entity Shell Company	false
Entity Common Stock, Shares Outstanding (in shares)		199,917,559
Current Fiscal Year End Date	--12-31
Document Fiscal Year Focus	2021
Document Fiscal Period Focus	Q1
Entity Central Index Key	0001368265
Amendment Flag	false

Condensed Consolidated Balance

Condensed Consolidated Balance Sheets - USD ($) $ in Thousands	Mar. 31, 2021	Dec. 31, 2020
Current assets:
Cash and cash equivalents	$ 116,696	$ 108,977
Short-term investments	29,529	29,528
Accounts receivable, net of allowance of $1,335 and $1,295 as of December 31, 2020 and March 31, 2021, respectively	64,175	61,784
Other receivables	25,669	23,655
Inventory	27,523	28,100
Prepaid expenses and other current assets	13,384	9,404
Derivative assets, related party	385	1,591
Total current assets	277,361	263,039
Operating lease right-of-use assets	35,231	25,967
Land, property and equipment, net	283,364	290,911
Long-term portion of restricted cash	7,003	11,000
Notes receivable and other long-term assets, net	32,582	27,299
Long-term portion of derivative assets, related party	962	4,057
Investments in other entities	26,608	27,962
Goodwill	64,328	64,328
Intangible assets, net	317	464
Total assets	727,756	715,027
Current liabilities:
Current portion of debt	6,761	3,592
Current portion of finance lease obligations	809	840
Current portion of operating lease obligations	3,134	2,822
Accounts payable	17,461	17,310
Accrued liabilities	53,162	52,637
Deferred revenue	4,499	2,642
Total current liabilities	85,826	79,843
Total long-term debt	80,044	82,088
Long-term portion of finance lease obligations	2,709	2,552
Long-term portion of operating lease obligations	32,342	23,698
Other long-term liabilities	5,729	3,996
Total liabilities	206,650	192,177
Commitments and contingencies (Note 17)
Stockholders' equity:
Preferred stock, $0.0001 par value. 1,000,000 shares authorized; no shares issued and outstanding	0	0
Common stock, $0.0001 par value. 304,000,000 shares authorized; 198,491,204 shares and 199,815,018 shares issued and outstanding as of December 31, 2020 and March 31, 2021, respectively	20	20
Additional paid-in capital	1,198,374	1,191,791
Accumulated deficit	(685,265)	(678,096)
Accumulated other comprehensive loss	(1,089)	(209)
Total Clean Energy Fuels Corp. stockholders' equity	512,040	513,506
Noncontrolling interest in subsidiary	9,066	9,344
Total stockholders' equity	521,106	522,850
Total liabilities and stockholders' equity	$ 727,756	$ 715,027

Condensed Consolidated Balanc_2

Condensed Consolidated Balance Sheets (Parenthetical) - USD ($) $ in Thousands	Mar. 31, 2021	Dec. 31, 2020
Statement of Financial Position [Abstract]
Accounts receivable, allowance for doubtful accounts	$ 1,295	$ 1,335
Preferred stock, par value (in dollars per share)	$ 0.0001	$ 0.0001
Preferred stock, authorized (in shares)	1,000,000	1,000,000
Preferred stock, issued (in shares)	0	0
Preferred stock, outstanding (in shares)	0	0
Common stock, par value (in dollars per share)	$ 0.0001	$ 0.0001
Common stock, authorized (in shares)	304,000,000	304,000,000
Common stock, issued (in shares)	199,815,018	198,491,204
Common stock, outstanding (in shares)	199,815,018	198,491,204

Condensed Consolidated Statemen

Condensed Consolidated Statements of Operations - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Revenues [Abstract]
Total revenue	$ 77,143	$ 86,006
Cost of sales (exclusive of depreciation and amortization shown separately below):
Change in fair value of derivative warrants		405
Selling, general and administrative	21,441	18,259
Depreciation and amortization	11,735	11,924
Total operating expenses	83,577	83,520
Operating income (loss)	(6,434)	2,486
Interest expense	(1,436)	(2,210)
Interest income	254	381
Other income, net	678	175
Income (loss) from equity method investments	(426)	145
Income (loss) before income taxes	(7,364)	977
Income tax expense	(83)	(78)
Net income (loss)	(7,447)	899
Loss attributable to noncontrolling interest	278	805
Net income (loss) attributable to Clean Energy Fuels Corp.	$ (7,169)	$ 1,704
Net income (loss) attributable to Clean Energy Fuels Corp. per share:
Basic (in dollars per share)	$ (0.04)	$ 0.01
Diluted (in dollars per share)	$ (0.04)	$ 0.01
Weighted-average common shares outstanding:
Basic (in shares)	198,995,453	204,992,555
Diluted (in shares)	198,995,453	206,040,099
Product revenue
Revenues [Abstract]
Total revenue	$ 67,692	$ 75,702
Cost of sales (exclusive of depreciation and amortization shown separately below):
Cost of sales	44,808	46,673
Service revenue
Revenues [Abstract]
Total revenue	9,451	10,304
Cost of sales (exclusive of depreciation and amortization shown separately below):
Cost of sales	$ 5,593	$ 6,259

Condensed Consolidated Statem_2

Condensed Consolidated Statements of Comprehensive Income (Loss) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Net income (loss)	$ (7,447)	$ 899
Other comprehensive income (loss), net of tax:
Foreign currency translation adjustments, net of $0 tax in 2020 and 2021	(880)	(1,921)
Unrealized gains on available-for-sale securities, net of $0 tax in 2020 and 2021		6
Total other comprehensive loss	(880)	(1,915)
Comprehensive loss	(8,327)	(1,016)
Clean Energy Fuels Corp.
Net income (loss)	(7,169)	1,704
Other comprehensive income (loss), net of tax:
Foreign currency translation adjustments, net of $0 tax in 2020 and 2021	(880)	(1,921)
Unrealized gains on available-for-sale securities, net of $0 tax in 2020 and 2021		6
Total other comprehensive loss	(880)	(1,915)
Comprehensive loss	(8,049)	(211)
Noncontrolling Interest in Subsidiary
Net income (loss)	(278)	(805)
Other comprehensive income (loss), net of tax:
Comprehensive loss	$ (278)	$ (805)

Condensed Consolidated Statem_3

Condensed Consolidated Statements of Comprehensive Income (Loss) (Parenthetical) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Statement of Comprehensive Income [Abstract]
Foreign currency translation adjustment, tax	$ 0	$ 0
Unrealized gains on available-for sale securities, tax	$ 0	$ 0

Condensed Consolidated Statem_4

Condensed Consolidated Statements of Stockholders' Equity - USD ($) $ in Thousands	Common stock	Additional Paid-In Capital	Accumulated Deficit	Accumulated Other Comprehensive Income (Loss)	Noncontrolling Interest in Subsidiary	Total
Beginning balance at Dec. 31, 2019	$ 20	$ 1,203,186	$ (668,232)	$ (1,566)	$ 9,621	$ 543,029
Beginning balance (in shares) at Dec. 31, 2019	204,723,055
Increase (Decrease) in Stockholders' Equity
Issuance of common stock		194				194
Issuance of common stock (in shares)	871,010
Repurchase of common stock		(4,244)				(4,244)
Repurchase of common stock (in shares)	(2,810,449)
Stock-based compensation		1,054				1,054
Net income (loss)			1,704		(805)	899
Other comprehensive loss				(1,915)		(1,915)
Increase in ownership in subsidiary		(1,388)			1,388
Ending balance at Mar. 31, 2020	$ 20	1,198,802	(666,528)	(3,481)	10,204	539,017
Ending balance (in shares) at Mar. 31, 2020	202,783,616
Beginning balance at Dec. 31, 2020	$ 20	1,191,791	(678,096)	(209)	9,344	$ 522,850
Beginning balance (in shares) at Dec. 31, 2020	198,491,204					198,491,204
Increase (Decrease) in Stockholders' Equity
Issuance of common stock		3,216				$ 3,216
Issuance of common stock (in shares)	1,323,814
Repurchase of common stock (in shares)						0
Stock-based compensation		3,367				$ 3,367
Net income (loss)			(7,169)		(278)	(7,447)
Other comprehensive loss				(880)		(880)
Ending balance at Mar. 31, 2021	$ 20	$ 1,198,374	$ (685,265)	$ (1,089)	$ 9,066	$ 521,106
Ending balance (in shares) at Mar. 31, 2021	199,815,018					199,815,018

Condensed Consolidated Statem_5

Condensed Consolidated Statements of Cash Flows - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Cash flows from operating activities:
Net income (loss)	$ (7,447)	$ 899
Adjustments to reconcile net income (loss) to net cash (used in) provided by operating activities:
Depreciation and amortization	11,735	11,924
Provision for credit losses and inventory	380	166
Stock-based compensation expense	3,367	1,054
Change in fair value of derivative instruments	2,045	(5,227)
Amortization of discount and debt issuance cost	13	(85)
Loss (gain) on disposal of property and equipment	46	(14)
Gain from sale of certain assets of subsidiary		(176)
Loss (income) from equity method investments	426	(145)
Non-cash lease expense	740	676
Deferred income taxes	33	30
Changes in operating assets and liabilities:
Accounts and other receivables	(1,786)	(180)
Inventory	(176)	51
Prepaid expenses and other assets	(7,666)	(2,682)
Operating lease liabilities	(1,048)	(851)
Accounts payable	446	(5,594)
Deferred revenue	1,857	(2,437)
Accrued liabilities and other	292	(1,667)
Net cash (used in) provided by operating activities	3,257	(4,258)
Cash flows from investing activities:
Purchases of short-term investments	(58,299)	(29,284)
Maturities and sales of short-term investments	58,301	56,500
Purchases of and deposits on property and equipment	(3,328)	(3,658)
Disbursements for loans receivable	(3,828)	(40)
Payments on and proceeds from sales of loans receivable	128	609
Cash received from sale of certain assets of subsidiary, net	887	5,628
Proceeds from disposal of property and equipment	7	685
Net cash provided by (used in) investing activities	(6,132)	30,440
Cash flows from financing activities:
Issuance of common stock	3,216	194
Repurchase of common stock		(4,244)
Proceeds for Adopt-a-Port program	2,520
Proceeds from debt instruments	1,900	200
Repayments of debt instruments and finance lease obligations	(1,108)	(1,700)
Net cash (used in) provided by financing activities	6,528	(5,550)
Effect of exchange rates on cash, cash equivalents and restricted cash	69	(328)
Net increase in cash, cash equivalents and restricted cash	3,722	20,304
Cash, cash equivalents and restricted cash, beginning of period	119,977	53,222
Cash, cash equivalents and restricted cash, end of period	123,699	73,526
Supplemental disclosure of cash flow information:
Income taxes paid		29
Interest paid, net of $98 and $0 capitalized, respectively	$ 1,052	$ 2,104

Condensed Consolidated Statem_6

Condensed Consolidated Statements of Cash Flows (Parenthetical) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Statement of Cash Flows [Abstract]
Interest paid, capitalized	$ 0	$ 98

General

General	3 Months Ended
General	Mar. 31, 2021
Organization, Consolidation and Presentation of Financial Statements [Abstract]
General	Clean Energy Fuels Corp. and Subsidiaries Notes to Condensed Consolidated Financial Statements (Unaudited) Note 1—General Nature of Business Clean Energy Fuels Corp., together with its majority and wholly owned subsidiaries (hereinafter collectively referred to as the “Company,” unless the context or the use of the term indicates or requires otherwise) is a leading renewable energy company focused on the procurement and distribution of renewable natural gas (“RNG”) and conventional natural gas, in the form of compressed natural gas (“CNG”) and liquefied natural gas (“LNG”), for the United States and Canadian transportation markets. The Company is also focused on developing, owning, and operating dairy and other livestock waste RNG projects and supplying RNG (procured from our own projects or from third parties) to its customers in the heavy and medium -duty commercial transportation sector. As a comprehensive clean energy solution provider, the Company also designs and builds, as well as operates and maintains (“O&M”), public and private vehicle fueling stations in the United States and Canada; sells and services compressors and other equipment used in RNG production and at fueling stations; transports and sells its fuels via “virtual” natural gas pipelines and interconnects; sells U.S. federal, state and local government credits (collectively, “Environmental Credits”) it generates by selling RNG as a vehicle fuel, including Renewable Identification Numbers (“RIN Credits” or “RINs”) under the federal Renewable Fuel Standard Phase 2 and credits under the California and the Oregon Low Carbon Fuel Standards (collectively, “LCFS Credits”); and obtains federal, state and local tax credits, grants and incentives. Basis of Presentation The accompanying interim unaudited condensed consolidated financial statements include the accounts of the Company and its subsidiaries, and, in the opinion of management, reflect all adjustments, which include only normal recurring adjustments, necessary to state fairly the Company’s consolidated financial position as of March 31, 2021, results of operations, comprehensive loss, and stockholders’ equity, and cash flows for the three months ended March 31, 2020 and 2021. All intercompany accounts and transactions have been eliminated in consolidation. The results of operations for the three month periods ended March 31, 2020 and 2021 are not necessarily indicative of the results to be expected for the year ending December 31, 2021 or for any other interim period or any future year. Certain information and disclosures normally included in the notes to consolidated financial statements have been condensed or omitted pursuant to the rules and regulations of the Securities and Exchange Commission (the “SEC”), but the resultant disclosures contained herein are in accordance with accounting principles generally accepted in the United States of America (“U.S. GAAP”) as they apply to interim reporting. The accompanying condensed consolidated financial statements should be read in conjunction with the consolidated financial statements as of and for the year ended December 31, 2020 that are included in the Company’s Annual Report on Form 10-K filed with the SEC on March 9, 2021. Use of Estimates The preparation of condensed consolidated financial statements in conformity with U.S. GAAP requires management to make estimates and assumptions that affect the amounts reported in the accompanying condensed consolidated financial statements and these notes. Actual results could differ from those estimates and may result in material effects on the Company’s operating results and financial position. Significant estimates made in preparing the accompanying condensed consolidated financial statements include (but are not limited to) those related to revenue recognition, fair value measurements, goodwill and long-lived asset valuations and impairment assessments, income tax valuations and stock-based compensation expense. Recently Adopted Accounting Pronouncements In December 2019, the Financial Accounting Standards Board (“FASB”) issued Accounting Standards Update ("ASU") No. 2019-12, Income Taxes (Topic 740): Simplifying the Accounting for Income Taxes

Revenue from Contracts with Cus

Revenue from Contracts with Customers	3 Months Ended
Revenue from Contracts with Customers	Mar. 31, 2021
Revenue from Contract with Customer [Abstract]
Revenue from Contracts with Customers	Note 2—Revenue from Contracts with Customers Revenue Recognition Overview The Company recognizes revenue when control of the promised goods or services is transferred to its customers, in an amount that reflects the consideration to which it expects to be entitled in exchange for the goods or services. To achieve that core principle, a five-step approach is applied: (1) identify the contract with a customer, (2) identify the performance obligations in the contract, (3) determine the transaction price, (4) allocate the transaction price to the performance obligations in the contract, and (5) recognize revenue allocated to each performance obligation when the Company satisfies the performance obligation. A performance obligation is a promise in a contract to transfer a distinct good or service to the customer, and is the unit of account for revenue recognition. The Company is generally the principal in its customer contracts because it has control over the goods and services prior to their transfer to the customer, and as such, revenue is recognized on a gross basis. Sales and usage-based taxes are excluded from revenue. Revenue is recognized net of allowances for returns and any taxes collected from customers, which are subsequently remitted to governmental authorities. The table below presents the Company’s revenue disaggregated by revenue source (in thousands): Three Months Ended March 31, 2020 2021 Volume-related (1) $ 75,060 $ 68,126 Station construction sales 5,522 4,535 AFTC (2) 5,424 4,482 Total revenue $ 86,006 $ 77,143 (1) Includes changes in fair value of derivative instruments related to the Company’s commodity swap and customer fueling contracts associated with the Company’s Zero Now truck financing program. The amounts are classified as revenue because the Company’s commodity swap contracts are used to economically offset the risk associated with the diesel-to-natural gas price spread resulting from customer fueling contracts under the Company’s Zero Now truck financing program. See Note 6 for more information about these derivative instruments. For the three months ended March 31, 2020 and 2021, aggregate changes in the fair value of commodity swaps and customer fueling contracts amounted to a gain of $5.6 million and a loss of $2.0 million, respectively. (2) Represents the federal alternative fuel excise tax credit that we refer to as “AFTC,” which was extended for vehicle fuel sales made beginning January 1, 2021 through December 31, 2021. See Note 19 for more information. Remaining Performance Obligations Remaining performance obligations represent the transaction price of customer orders for which the work has not been performed. As of March 31, 2021, the aggregate amount of the transaction price allocated to remaining performance obligations was $9.6 million, which related to the Company’s station construction sale contracts. The Company expects to recognize revenue on the remaining performance obligations under these contracts over the next 12 For volume-related revenue, the Company has elected to apply an optional exemption, which waives the requirement to disclose the remaining performance obligation for revenue recognized through the ‘ Contract Balances The timing of revenue recognition, billings and cash collections results in billed accounts receivable, unbilled receivables (contract assets), and customer advances and deposits (contract liabilities) in the accompanying condensed consolidated balance sheets. As of December 31, 2020 and March 31, 2021, the Company’s contract balances were as follows (in thousands): December 31, March 31, 2020 2021 Accounts receivable, net $ 61,784 $ 64,175 Contract assets - current $ 729 $ 812 Contract assets - non-current 3,998 3,951 Contract assets - total $ 4,727 $ 4,763 Contract liabilities - current $ 1,638 $ 2,561 Contract liabilities - non-current 59 59 Contract liabilities - total $ 1,697 $ 2,620 Accounts Receivable, Net "Accounts receivable, net" in the accompanying condensed consolidated balance sheets includes amounts billed and currently due from customers. The amounts due are stated at their net estimated realizable value. The Company maintains an allowance to provide for the estimated amount of receivables that will not be collected. The allowance is based upon an assessment of customer creditworthiness, historical payment experience, the age of outstanding receivables, and economic conditions that may affect a customer’s ability to pay. Contract Assets Contract assets include unbilled amounts typically resulting from the Company’s station construction sale contracts, when the cost-to-cost method of revenue recognition is utilized and revenue recognized exceeds the amount billed to the customer, and right to payment is not just subject to the passage of time. Amounts may not exceed their net realizable value. Contract assets are classified as current or noncurrent based on the timing of billings. The current portion is included in “Prepaid expenses and other current assets” and the noncurrent portion is included in “Notes receivable and other long-term assets, net” in the accompanying condensed consolidated balance sheets. Contract Liabilities Contract liabilities consist of billings in excess of revenue recognized from the Company’s station construction sale contracts and payments received primarily from customers of NG Advantage, LLC (“NG Advantage”) in advance of the performance obligations and are classified as current or noncurrent based on when the related revenue is expected to be recognized. The current portion and noncurrent portion of contract liabilities are included in “Deferred revenue” and “Other long-term liabilities,” respectively, in the accompanying condensed consolidated balance sheets. Revenue recognized during the three months ended March 31, 2020 related to the Company’s contract liability balances as of December 31, 2019 was $3.9 million. The increase in the contract liability balances for the three months ended March 31, 2021 is primarily driven by billings in excess of revenue recognized, offset by $1.5 million of revenue recognized related to the Company’s contract liability balances as of December 31, 2020.

Investments in Other Entities a

Investments in Other Entities and Noncontrolling Interest in a Subsidiary	3 Months Ended
	Mar. 31, 2021
Investments, All Other Investments [Abstract]
Investments in Other Entities and Noncontrolling Interest in a Subsidiary	Note 3— Investments in Other Entities and Noncontrolling Interest in a Subsidiary Total Joint Venture On March 3, 2021, the Company entered an agreement (“Total JV Agreement”) with Total S.E. (“Total”) that created a 50/50 joint venture (“Total JV”) to develop anaerobic digester gas (“ADG”) RNG production facilities in the United States. The Total JV Agreement contemplates that the Total JV will invest up to $400.0 million of equity in production projects, and Total and the Company each committed to initially provide $50.0 million for the Total JV (the “Total JV Equity Obligations”). To fund the Company’s Total JV Equity Obligations, the Company has the option to borrow $20.0 million from Société Générale pursuant to the term credit agreement described in Note 12. bp Joint Venture On April 13, 2021, the Company entered an agreement (“bp JV Agreement”) with BP Products North America Inc. (“bp”) that created a 50/50 joint venture (“bpJV”) to develop, own and operate new ADG RNG production facilities in the United States. Pursuant to the bp JV Agreement, bp and the Company have committed to provide $50.0 million and $30.0 million, respectively, with bp SAFE&CEC S.r.l. On November 26, 2017, the Company, through its former subsidiary IMW Industries Ltd. (formerly known as Clean Energy Compression Corp.) (“CEC”), entered into an investment agreement with Landi Renzo S.p.A. (“LR”), an alternative fuels company based in Italy. Pursuant to the investment agreement, the Company and LR agreed to combine their respective natural gas compressor fueling systems manufacturing subsidiaries, CEC and SAFE S.p.A, in a new company, SAFE&CEC S.r.l. (such combination transaction is referred to as the “CEC Combination”). SAFE&CEC S.r.l. is focused on manufacturing, selling and servicing natural gas fueling compressors and related equipment for the global natural gas fueling market. As of the closing of the CEC Combination on December 29, 2017, the Company owns 49% of SAFE&CEC S.r.l., and LR owns 51% of SAFE&CEC S.r.l. The Company accounts for its interest in SAFE&CEC S.r.l. using the equity method of accounting because the Company does not control but has the ability to exercise significant influence over SAFE&CEC S.r.l.’s operations. For the three months ended March 31, 2020 and 2021, the Company recorded income of $0.0 million and a loss of $0.4 million from this investment, respectively. As of December 31, 2020 and March 31, 2021, the Company had an investment balance in SAFE&CEC S.r.l. of $24.7 million and $23.3 million, respectively. NG Advantage On October 14, 2014, the Company entered into a Common Unit Purchase Agreement (“UPA”) with NG Advantage for a 53.3% controlling interest in NG Advantage. NG Advantage is engaged in the business of transporting CNG in high-capacity trailers to industrial and institutional energy users, such as hospitals, food processors, manufacturers and paper mills that do not have direct access to natural gas pipelines. As of March 31, 2021, the Company’s controlling interest in NG Advantage was 93.3%. The Company recorded a loss attributable to the noncontrolling interest in NG Advantage of $0.8 million and $0.3 million for the three months ended March 31, 2020 and 2021, respectively. The value of the noncontrolling interest was $9.3 million and $9.1 million as of December 31, 2020 and March 31, 2021, respectively.

Cash, Cash Equivalents, and Res

Cash, Cash Equivalents, and Restricted Cash	3 Months Ended
Cash, Cash Equivalents, and Restricted Cash	Mar. 31, 2021
Cash and Cash Equivalents [Abstract]
Cash, Cash Equivalents, and Restricted Cash	Note 4—Cash, Cash Equivalents and Restricted Cash Cash, cash equivalents and restricted cash as of December 31, 2020 and March 31, 2021 consisted of the following (in thousands): December 31, March 31, 2020 2021 Current assets: Cash and cash equivalents $ 108,977 $ 116,696 Total cash and cash equivalents $ 108,977 $ 116,696 Long-term assets: Restricted cash - standby letters of credit $ 4,000 $ — Restricted cash - held as collateral 7,000 7,003 Total long-term portion of restricted cash $ 11,000 $ 7,003 Total cash, cash equivalents and restricted cash $ 119,977 $ 123,699 The Company considers all highly liquid investments with maturities of three months or less on the date of acquisition to be cash equivalents. The Company places its cash and cash equivalents with high credit quality financial institutions. At times, such balances may be in excess of the Federal Deposit Insurance Corporation (“FDIC”) and Canadian Deposit Insurance Corporation (“CDIC”) limits. Financial instruments that potentially subject the Company to concentrations of credit risk consist principally of cash deposits. The amounts in excess of FDIC and CDIC limits were approximately $107.6 million and $115.4 million as of December 31, 2020 and March 31, 2021, respectively. The Company classifies restricted cash as short-term and a current asset if the cash is expected to be used in operations within a year or to acquire a current asset. Otherwise, the restricted cash is classified as long-term.

Short-Term Investments

Short-Term Investments	3 Months Ended
Short-Term Investments	Mar. 31, 2021
Investments, Debt and Equity Securities [Abstract]
Short-Term Investments	Note 5—Short-Term Investments Short-term investments include available-for-sale debt securities and certificates of deposit. Available-for-sale debt securities are carried at fair value, inclusive of unrealized gains and losses. Unrealized gains and losses on available-for-sale debt securities are recognized in other comprehensive income (loss), net of applicable income taxes. Gains or losses on sales of available-for-sale debt securities are recognized on the specific identification basis. The Company reviews available-for-sale debt securities for declines in fair value below their cost basis each quarter and whenever events or changes in circumstances indicate that the cost basis of an asset may not be recoverable, and evaluates the current expected credit loss. This evaluation is based on a number of factors, including historical experience, market data, issuer-specific factors, economic conditions, and any changes to the credit rating of the security. As of March 31, 2021, the Company has not recorded a credit loss related to available-for-sale debt securities and believes the carrying values for its available-for-sale debt securities are properly recorded. Short-term investments as of December 31, 2020 consisted of the following (in thousands): Gross Amortized Unrealized Estimated Cost Gain (Loss) Fair Value Municipal bonds and notes $ 28,998 $ — $ 28,998 Certificates of deposit 530 — 530 Total short-term investments $ 29,528 $ — $ 29,528 Short-term investments as of March 31, 2021 consisted of the following (in thousands): Gross Amortized Unrealized Estimated Cost Gain (Loss) Fair Value Municipal bonds and notes $ 28,999 $ — $ 28,999 Certificates of deposit 530 — 530 Total short-term investments $ 29,529 $ — $ 29,529

Derivative Instruments and Hedg

Derivative Instruments and Hedging Activities	3 Months Ended
Derivative Instruments and Hedging Activities	Mar. 31, 2021
Derivative Instruments and Hedging Activities Disclosure [Abstract]
Derivative Instruments and Hedging Activities	Note 6 - Derivative Instruments and Hedging Activities In October 2018, the Company executed two commodity swap contracts with Total Gas & Power North America, an affiliate of Total and THUSA (as defined in Note 12), for a total of 5.0 million diesel gallons annually from April 1, 2019 to June 30, 2024. These commodity swap contracts are used to manage diesel price fluctuation risks related to the natural gas fuel supply commitments the Company makes in its fueling agreements with fleet operators that participate in the Zero Now The Company has entered into fueling agreements with fleet operators under the Zero Now Derivatives and embedded derivatives as of December 31, 2020 consisted of the following (in thousands): Gross Amounts Gross Amounts Net Amount Recognized Offset Presented Assets: Commodity swaps: Current portion of derivative assets, related party $ 1,591 $ — $ 1,591 Long-term portion of derivative assets, related party 4,057 — 4,057 Fueling agreements: Prepaid expenses and other current assets 249 — 249 Notes receivable and other long-term assets, net 542 — 542 Total derivative assets $ 6,439 $ — $ 6,439 Liabilities: Fueling agreements: Accrued liabilities $ 283 $ — $ 283 Other long-term liabilities 273 — 273 Total derivative liabilities $ 556 $ — $ 556 Derivatives and embedded derivatives as of March 31, 2021 consisted of the following (in thousands): Gross Amounts Gross Amounts Net Amount Recognized Offset Presented Assets: Commodity swaps: Current portion of derivative assets, related party $ 385 $ — $ 385 Long-term portion of derivative assets, related party 962 — 962 Fueling agreements: Prepaid expenses and other current assets 658 — 658 Notes receivable and other long-term assets, net 1,863 — 1,863 Total derivative assets $ 3,868 $ — $ 3,868 Liabilities: Fueling agreements: Accrued liabilities $ 11 $ — $ 11 Other long-term liabilities 19 — 19 Total derivative liabilities $ 30 $ — $ 30 As of December 31, 2020 and March 31, 2021, the Company had a total volume on open commodity swap contracts of 16.9 million and 15.6 million diesel gallons, respectively, at a weighted-average price of approximately $3.18 per gallon. The following table reflects the weighted-average price of open commodity swap contracts as of December 31, 2020 and March 31, 2021, by year with associated volumes: December 31, 2020 March 31, 2021 Volumes Weighted-Average Price per Volumes Weighted-Average Price per Year (Diesel Gallons) Diesel Gallon (Diesel Gallons) Diesel Gallon 2021 5,000,000 $ 3.18 3,750,000 $ 3.18 2022 5,000,000 $ 3.18 5,000,000 $ 3.18 2023 5,000,000 $ 3.18 5,000,000 $ 3.18 2024 1,875,000 $ 3.18 1,875,000 $ 3.18

Fair Value Measurements

Fair Value Measurements	3 Months Ended
Fair Value Measurements	Mar. 31, 2021
Fair Value Disclosures [Abstract]
Fair Value Measurements	Note 7—Fair Value Measurements The Company follows the authoritative guidance for fair value measurements with respect to assets and liabilities that are measured at fair value on a recurring basis and non-recurring basis. Under the standard, fair value is defined as the exit price, or the amount that would be received to sell an asset or paid to transfer a liability in an orderly transaction between market participants, as of the measurement date. The standard also establishes a hierarchy for inputs used in measuring fair value that maximizes the use of observable inputs and minimizes the use of unobservable inputs by requiring that the most observable inputs be used when available. Observable inputs are inputs market participants would use in valuing the asset or liability developed based on market data obtained from sources independent of the Company. Unobservable inputs are inputs that reflect the Company’s assumptions about the factors market participants would use in valuing the asset or liability developed based upon the best information available in the circumstances. The hierarchy consists of the following three levels: Level 1 inputs are quoted prices (unadjusted) in active markets for identical assets or liabilities; Level 2 inputs include quoted prices for similar assets or liabilities in active markets, quoted prices for identical or similar assets or liabilities in markets that are not active, and inputs (other than quoted prices) that are observable for the asset or liability, either directly or indirectly; Level 3 inputs are unobservable inputs for the asset or liability. Categorization within the valuation hierarchy is based upon the lowest level of input that is significant to the fair value measurement. Assets and Liabilities Measured at Fair Value on a Recurring Basis The Company’s available-for-sale debt securities and certificates of deposit are classified within Level 2 because they are valued using the most recent quoted prices for identical assets in markets that are not active and quoted prices for similar assets in active markets. The Company used the income approach to value its outstanding commodity swap contracts and embedded derivatives in its fueling agreements under the Zero Now The Company estimated the fair value of its outstanding commodity swap contracts based on the following inputs as of December 31, 2020 and March 31, 2021: December 31, 2020 March 31, 2021 Significant Unobservable Inputs Input Range Weighted Average Input Range Weighted Average ULSD Gulf Coast Forward Curve $1.47 - $1.54 $ 1.50 $1.66 - $1.72 $ 1.69 Historical Differential to PADD 3 Diesel $0.81 - $1.58 $ 0.99 $0.81 - $1.58 $ 1.00 Historical Differential to PADD 5 Diesel $1.66 - $2.58 $ 2.01 $1.75 - $2.58 $ 2.04 The Company estimated the fair value of embedded derivatives in its fueling agreements under the Zero Now December 31, 2020 March 31, 2021 Significant Unobservable Inputs Input Range Weighted Average Input Range Weighted Average ULSD Gulf Coast Forward Curve $1.47 - $1.54 $ 1.50 $1.66 - $1.72 $ 1.69 Historical Differential to PADD 3 Diesel $0.81 - $1.58 $ 0.99 $0.81 - $1.58 $ 1.00 Historical Differential to PADD 5 Diesel $1.66 - $2.58 $ 2.01 $1.75 - $2.58 $ 2.04 There were no transfers of assets or liabilities between Level 1, Level 2, or Level 3 of the fair value hierarchy as of December 31, 2020 or March 31, 2021. The following tables provide information by level for assets and liabilities that are measured at fair value on a recurring basis as of December 31, 2020 and March 31, 2021 (in thousands): December 31, 2020 Level 1 Level 2 Level 3 Assets: Available-for-sale securities (1) Municipal bonds and notes $ 28,998 $ — $ 28,998 $ — Certificates of deposit (1) 530 — 530 — Commodity swap contracts (2) 5,648 — — 5,648 Embedded derivatives (3) 791 — — 791 Liabilities: Embedded derivatives (3) $ 556 $ — $ — $ 556 March 31, 2021 Level 1 Level 2 Level 3 Assets: Available-for-sale securities (1) Municipal bonds and notes $ 28,999 $ — $ 28,999 $ — Certificates of deposit (1) 530 — 530 — Commodity swap contracts (2) 1,347 — — 1,347 Embedded derivatives (3) 2,521 — — 2,521 Liabilities: Embedded derivatives (3) $ 30 $ — $ — $ 30 (1) Included in "Short-term investments" in the accompanying condensed consolidated balance sheets. See Note 5 for more information. (2) Included in "Derivative assets, related party" and "Long-term portion of derivative assets, related party" in the accompanying condensed consolidated balance sheets. See Note 6 for more information. (3) Included in "Prepaid expenses and other current assets," “Notes receivable and other long-term assets, net," “Accrued liabilities” and “Other long-term liabilities” in the accompanying condensed consolidated balance sheets. See Note 6 for more information. The following table provides a reconciliation of the beginning and ending balances of items measured at fair value on a recurring basis as shown in the tables above that used significant unobservable inputs (Level 3), as well as the change in unrealized gains or losses for the periods included in earnings (in thousands): Assets: Assets: Liabilities: Liabilities: Commodity Embedded Commodity Embedded Liabilities: Swap Contracts Derivatives Swap Contracts Derivatives Warrants Balance as of December 31, 2019 $ 3,270 $ 723 $ (164) $ (81) $ (40) Settlements, net (24) — 56 — — Total gain (loss) 9,299 (580) 108 (3,227) (405) Balance as of March 31, 2020 $ 12,545 $ 143 $ — $ (3,308) $ (445) Balance as of December 31, 2020 $ 5,648 $ 791 $ — $ (556) $ — Settlements, net (225) — 38 — — Total gain (loss) (4,076) 1,730 (38) 526 — Balance as of March 31, 2021 $ 1,347 $ 2,521 $ — $ (30) $ — Change in unrealized gain (loss) for the three months ended March 31, 2020 included in earnings $ 9,275 $ (580) $ 164 $ (3,227) $ (405) Change in unrealized gain (loss) for the three months ended March 31, 2021 included in earnings $ (4,301) $ 1,730 $ — $ 526 $ — Other Financial Assets and Liabilities The carrying amounts of the Company’s cash, cash equivalents and restricted cash, receivables and payables approximate fair value due to the short-term nature of those instruments. The carrying amounts of the Company’s debt instruments approximated their respective fair values as of December 31, 2020 and March 31, 2021. The fair values of these debt instruments were estimated using a DCF analysis based on interest rates offered on loans with similar terms to borrowers of similar credit quality, which are Level 3 inputs. See Note 12 for more information about the Company’s debt instruments.

Other Receivables

Other Receivables	3 Months Ended
Other Receivables	Mar. 31, 2021
Receivables [Abstract]
Other Receivables	Note 8—Other Receivables Other receivables as of December 31, 2020 and March 31, 2021 consisted of the following (in thousands): December 31, March 31, 2020 2021 Loans to customers to finance vehicle purchases $ 394 $ 394 Accrued customer billings 6,335 6,280 Fuel tax credits 10,556 11,454 Other 6,370 7,541 Total other receivables $ 23,655 $ 25,669

Inventory

Inventory	3 Months Ended
Inventory	Mar. 31, 2021
Inventory Disclosure [Abstract]
Inventory	Note 9—Inventory Inventory consists of raw materials and spare parts, work in process and finished goods and is stated at the lower of cost (first-in, first-out) or net realizable value. The Company evaluates inventory balances for excess quantities and obsolescence by analyzing estimated demand, inventory on hand, sales levels and other information, and reduces inventory balances to net realizable value for excess and obsolete inventory based on this analysis. Inventory as of December 31, 2020 and March 31, 2021 consisted of the following (in thousands): December 31, March 31, 2020 2021 Raw materials and spare parts $ 28,100 $ 27,523 Total inventory $ 28,100 $ 27,523

Land, Property and Equipment

Land, Property and Equipment	3 Months Ended
Land, Property and Equipment	Mar. 31, 2021
Property, Plant and Equipment [Abstract]
Land, Property and Equipment	Note 10—Land, Property and Equipment Land, property and equipment, net as of December 31, 2020 and March 31, 2021 consisted of the following (in thousands): December 31, March 31, 2020 2021 Land $ 3,476 $ 3,476 LNG liquefaction plants 94,633 94,633 Station equipment 344,839 346,961 Trailers 79,860 80,465 Other equipment 89,276 89,651 Construction in progress 73,272 72,872 685,356 688,058 Less accumulated depreciation (394,445) (404,694) Total land, property and equipment, net $ 290,911 $ 283,364 Included in "Land, property and equipment, net" are capitalized software costs of $32.3 million and $32.7 million as of December 31, 2020 and March 31, 2021, respectively. Accumulated amortization of the capitalized software costs is $28.8 million and $29.4 million as of December 31, 2020 and March 31, 2021, respectively. The Company recorded amortization expense related to capitalized software costs of $0.7 million and $0.5 million for the three months ended March 31, 2020 and 2021, respectively. As of March 31, 2020 and 2021, $2.1 million and $1.4 million, respectively, is included in "Accounts payable" and "Accrued liabilities," which amounts are related to purchases of property and equipment. These amounts are excluded from the accompanying condensed consolidated statements of cash flows as they are non-cash investing activities.

Accrued Liabilities

Accrued Liabilities	3 Months Ended
Accrued Liabilities	Mar. 31, 2021
Payables and Accruals [Abstract]
Accrued Liabilities	Note 11—Accrued Liabilities Accrued liabilities as of December 31, 2020 and March 31, 2021 consisted of the following (in thousands): December 31, March 31, 2020 2021 Accrued alternative fuels incentives (1) $ 18,175 $ 20,117 Accrued employee benefits 4,282 3,300 Accrued gas and equipment purchases 9,897 10,819 Accrued interest 512 868 Accrued property and other taxes 3,094 4,878 Accrued salaries and wages 7,646 2,918 Embedded derivatives 283 11 Other (2) 8,748 10,251 Total accrued liabilities $ 52,637 $ 53,162 (1) Includes the amount of RINs, LCFS Credits and the amount of AFTC payable to third parties. (2) No individual item in “Other” exceeds 5% of total current liabilities .

Debt

Debt	3 Months Ended
Debt	Mar. 31, 2021
Debt Disclosure [Abstract]
Debt	Note 12—Debt Debt obligations as of December 31, 2020 and March 31, 2021 consisted of the following (in thousands): December 31, 2020 Unamortized Debt Balance, Net of Principal Balance Financing Costs Financing Costs bp Loan $ 50,000 $ — $ 50,000 NG Advantage debt 29,535 117 29,418 SG Facility 5,100 — 5,100 Other debt 1,162 — 1,162 Total debt 85,797 117 85,680 Less amounts due within one year (3,631) (39) (3,592) Total long-term debt $ 82,166 $ 78 $ 82,088 March 31, 2021 Unamortized Debt Balance, Net of Principal Balance Financing Costs Financing Costs bp Loan $ 50,000 $ — $ 50,000 NG Advantage debt 28,837 106 28,731 SG Facility 7,000 — 7,000 Other debt 1,074 — 1,074 Total debt 86,911 106 86,805 Less amounts due within one year (6,793) (32) (6,761) Total long-term debt $ 80,118 $ 74 $ 80,044 SG Credit Agreement On January 2, 2019, the Company entered into a term credit agreement (the “Credit Agreement”) with Société Générale, a company incorporated as a société anonyme under the laws of France (“SG”). The Credit Agreement provides for a term loan facility (the “SG Facility”) pursuant to which the Company may obtain, subject to certain conditions, up to $100.0 million of loans (“SG Loans”) in support of its Zero Now Zero Now The Company is required to make quarterly principal payments of $2.5 million beginning March 31, 2022 with any unpaid amount due on January 2, 2024, subject to the option to extend the maturity date for three successive terms of one year each. The Company is required to make mandatory prepayments under the SG Facility equal to any amounts the Company receives for complete or partial refunds of the incremental cost of trucks purchased or financed under the Zero Now The Credit Agreement does not include financial covenants, and the Company has not provided SG with any security for its obligations under the Credit Agreement. As described below, THUSA has entered into the Guaranty to guarantee the Company’s payment obligations to SG under the Credit Agreement. As of March 31, 2021, the Company had $7.0 million outstanding on the SG Facility, and no events of defaults had occurred. Total Credit Support Agreement The Company entered into a credit support agreement with Total Holdings USA Inc. (“THUSA”), a wholly owned subsidiary of Total, on January 2, 2019, which was subsequently amended on March 12, 2021 (as amended, the “CSA”) in conjunction with the March 12, 2021 amendment to the Credit Agreement. Under the CSA, THUSA agreed to enter into a guaranty agreement (“Guaranty”) pursuant to which it has guaranteed the Company’s obligation to repay to SG up to $100.0 million in SG Loans and interest thereon in accordance with the Credit Agreement. In consideration for the commitments of THUSA under the CSA, the Company is required to pay THUSA a quarterly guaranty fee at a rate per quarter equal to 2.5% of the average aggregate SG Loan amount for the preceding calendar quarter. Following any payment by THUSA to SG under the Guaranty, the Company would be obligated to immediately pay to THUSA the full amount of such payment plus interest on such amount at a rate equal to LIBOR plus 1.0%. In addition, the Company would be obligated to pay and reimburse THUSA for all reasonable out-of-pocket expenses it incurs in the performance of its services under the CSA, including all reasonable out-of-pocket attorneys’ fees and expenses incurred in connection with the payment to SG under the Guaranty or any enforcement or attempt to enforce any of the Company‘s obligations under the CSA. The CSA includes customary representations and warranties and affirmative and negative covenants by the Company. In addition, upon the occurrence of a “Trigger Event” and during its continuation, THUSA may, among other things: elect not to guarantee additional SG Loans; declare all or any portion of the outstanding amounts the Company owes THUSA under the CSA to be due and payable; and exercise all other rights it may have under applicable law. Each of the following events constitutes a Trigger Event: the Company defaults with respect to any payment obligation under the CSA; any representation or warranty made by the Company in the CSA was false, incorrect, incomplete or misleading in any material respect when made; the Company fails to observe or perform any material covenant, obligation, condition or agreement in the CSA; or the Company defaults in the observance or performance of any agreement, term or condition contained in any other agreement with THUSA or an affiliate of THUSA. As security for the Company’s obligations under the CSA, on January 2, 2019, the Company entered into a pledge and security agreement with THUSA and delivered a collateral assignment of contracts to THUSA, pursuant to which the Company collaterally assigned to THUSA all fueling agreements it enters into with participants in the Zero Now Zero Now Until the occurrence of a Trigger Event or Fundamental Trigger Event (as described below) under the CSA, the Company has the freedom to operate in the normal course, and there are no restrictions on the flow of funds in and out of the lockbox account established pursuant to the lockbox agreement. Upon the occurrence of a Trigger Event under the CSA, all funds in the lockbox account will be: first, used to make scheduled debt repayments under the Credit Agreement; and second, released to the Company. Further, upon the occurrence of a “Fundamental Trigger Event” under the CSA and during its continuation, in addition to exercising any of the remedies available to THUSA upon the occurrence of a Trigger Event as described above: all participants in the Zero Now The CSA will terminate following the later of: the payment in full of all of the Company’s obligations under the CSA; and the termination or expiration of the Guaranty following the maturity date of the last outstanding SG Loan or December 31, 2023, whichever is earlier. NG Advantage Debt On November 30, 2016, NG Advantage entered into a Loan and Security Agreement (the “Wintrust LSA”) with Wintrust Commercial Finance (“Wintrust”), pursuant to which Wintrust agreed to lend NG Advantage $4.7 million. The proceeds were primarily used to fund the purchases of CNG trailers and equipment. Interest and principal are payable monthly in 72 equal monthly installments at an annual rate of 5.17%. As collateral security for the prompt payment in full when due of NG Advantage’s obligations to Wintrust under the Wintrust LSA, NG Advantage pledged to and granted Wintrust a security interest in all of its right, title and interest in the CNG trailers and equipment purchased with the proceeds received under the Wintrust LSA. On December 10, 2020, NG Advantage entered an Amended and Restated Loan and Security Agreement with Berkshire Bank (“Berkshire ALA”) to substitute and replace the two existing loans with Berkshire Bank dated May 12, 2016 and January 24, 2017 (collectively, the “Original Debt”). The Berkshire ALA provides NG Advantage a 5-year NG Advantage has entered into sale and leaseback transactions with various lessors as described below. In each instance, the sale and leaseback transaction does not qualify for sale-leaseback accounting because of NG Advantage’s continuing involvement with the buyer-lessor due to a fixed price repurchase option. As a result, the transactions are recorded under the financing method, in which the assets remain on the accompanying condensed consolidated balance sheets and the proceeds from the transactions are recorded as financing liabilities. On December 18, 2017, NG Advantage entered into a sale-leaseback arrangement through a Master Lease Agreement (the “BoA MLA”) with Bank of America Leasing & Capital, LLC (“BoA”). Pursuant to the BoA MLA, NG Advantage received $2.1 million in cash for CNG trailers and simultaneously leased them back from BoA for five years commencing January 1, 2018 with interest and principal payable in 60 equal monthly installments at an annual rate of 4.86%. On March 1, 2018, NG Advantage entered into a sale-leaseback arrangement through a Master Lease Agreement (the “First National MLA”) with First National Capital, LLC (“First National”). Pursuant to the First National MLA, NG Advantage received $6.3 million in cash, net of fees and the first month’s lease payment for CNG trailers and simultaneously leased them back from First National for six years commencing March 1, 2018 with interest and principal payable in 72 equal monthly installments at an annual rate of 9.28%. On December 20, 2018 (the “Closing Date”), NG Advantage entered into a purchase agreement to sell a compression station for a purchase price of $7.0 million to an entity whose member owners were noncontrolling interest member owners of NG Advantage. On the Closing Date and immediately following the consummation of the sale of the compression station, NG Advantage entered into a lease agreement with the buyer of the station (the “Lease”) pursuant to which the station was leased back to NG Advantage for a term of five years with monthly rent payments equal to $0.1 million at an annual rate of 12.0%. bp Loan On December 18, 2020, the Company entered a Memorandum of Understanding (“MOU”) with bp to create a joint venture to develop, own, and operate RNG production facilities at dairies. Contemporaneous with the execution of the MOU, the Company and bp executed a loan agreement whereby bp advanced $50.0 million (“bp Loan”) to fund capital costs and expenses incurred prior to formation of the joint venture. The bp Loan bore interest at the rate per annum equal to LIBOR plus 4.33% . As repayment of the bp Loan, the outstanding principal balance was contributed to the bpJV in April 2021 upon entering the bp JV Agreement (Note 3). Other Debt The Company has other debt due at various dates through 2024 bearing interest at rates up to 4.75% with a weighted-average interest rate of 4.38% and 4.37% as of December 31, 2020 and March 31, 2021, respectively.

Net Income (Loss) Per Share

Net Income (Loss) Per Share	3 Months Ended
Net Income (Loss) Per Share	Mar. 31, 2021
Earnings Per Share [Abstract]
Net Income (Loss) Per Share	Note 13—Net Income (Loss) Per Share Basic net income (loss) per share is computed by dividing the net income (loss) attributable to Clean Energy Fuels Corp. by the weighted-average number of common shares outstanding and common shares issuable for little or no cash consideration during the period. Diluted net income (loss) per share is computed by dividing the net income (loss) attributable to Clean Energy Fuels Corp. by the weighted-average number of common shares outstanding and common shares issuable for little or no cash consideration during the period and potentially dilutive securities outstanding during the period, and therefore reflects the dilution from common shares that may be issued upon exercise or conversion of these potentially dilutive securities, such as stock options, warrants, convertible notes and restricted stock units. The dilutive effect of stock awards and warrants is computed under the treasury stock method. The dilutive effect of convertible notes and restricted stock units is computed under the if-converted method. Potentially dilutive securities are excluded from the computations of diluted net income (loss) per share if their effect would be antidilutive. The following table sets forth the computations of basic and diluted earnings (loss) per share for the three months ended March 31, 2020 and 2021 (in thousands except share and per share amounts): Three Months Ended March 31, 2020 2021 Net income (loss) attributable to Clean Energy Fuels Corp. $ 1,704 $ (7,169) Weighted-average common shares outstanding 204,992,555 198,995,453 Dilutive effect of potential common shares from restricted stock units and stock options 1,047,544 — Weighted-average common shares outstanding - diluted 206,040,099 198,995,453 Basic income (loss) per share $ 0.01 $ (0.04) Diluted income (loss) per share $ 0.01 $ (0.04) The following potentially dilutive securities have been excluded from the diluted net income (loss) per share calculations because their effect would have been antidilutive. Although these securities were antidilutive for these periods, they could be dilutive in future periods. Three Months Ended March 31, 2020 2021 Stock options 7,536,325 9,673,902 Convertible notes 3,164,557 — Restricted stock units 219,241 1,243,946 Total 10,920,123 10,917,848

Stock-Based Compensation

Stock-Based Compensation	3 Months Ended
Stock-Based Compensation	Mar. 31, 2021
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
Stock-Based Compensation	Note 14—Stock-Based Compensation The following table summarizes the compensation expense and related income tax benefit related to the Company’s stock-based compensation arrangements recognized in the accompanying condensed consolidated statements of operations during the three months ended March 31, 2020 and 2021 (in thousands): Three Months Ended March 31, 2020 2021 Stock-based compensation expense, net of $0 tax in 2020 and 2021 $ 1,054 $ 3,367 As of March 31, 2021, there was $30.0 million of total unrecognized compensation costs related to unvested shares subject to outstanding stock options and restricted stock units, which is expected to be expensed over a weighted-average period of approximately 2.3 years.

Stockholders' Equity

Stockholders' Equity	3 Months Ended
Stockholders' Equity	Mar. 31, 2021
Equity [Abstract]
Stockholders' Equity	Note 15—Stockholders’ Equity Share Repurchase Program On March 12, 2020, the Company’s Board of Directors approved a share repurchase program of up to $30.0 million (exclusive of fees and commissions) of the Company’s outstanding common stock (the “Repurchase Program”). The Repurchase Program does not have an expiration date, and it may be suspended or discontinued at any time. As of March 31, 2021, the Company had utilized $14.5 million under the Repurchase Program. During the three months ended March 31, 2021, the Company did not repurchase any shares of its common stock. The Repurchase Program does not obligate the Company to acquire any specific number of shares. Repurchases under the Repurchase Program may be effected from time to time through open market purchases, privately negotiated transactions, structured or derivative transactions, including accelerated share repurchase transactions, or other methods of acquiring shares, in each case subject to market conditions, applicable securities laws and other relevant factors. Repurchases may also be made under Rule 10b5-1 plans.

Income Taxes

Income Taxes	3 Months Ended
Income Taxes	Mar. 31, 2021
Income Tax Disclosure [Abstract]
Income Taxes	Note 16—Income Taxes The provision for income taxes for interim periods is determined using an estimate of the Company’s annual effective tax rate, adjusted for discrete items, if any, that are taken into account in the relevant period. Each quarter, the Company updates the estimate of the annual effective tax rate, and if the estimated tax rate changes, a cumulative adjustment is recorded. The Company’s income tax expense was $0.1 million for each of the three months ended March 31, 2020 and 2021. Tax expense for all periods consists of taxes due on the Company’s U.S. and foreign operations. The effective tax rates for the three months ended March 31, 2020 and 2021 are different from the federal statutory tax rate primarily due to losses for which no tax benefit has been recognized. The Company increased its liability for unrecognized tax benefits in the three months ended March 31, 2021 by $0.8 million. This increase is primarily attributable to the portion of AFTC revenue recognized in the period attributed to the federal fuel tax the Company collected from its customers during the three months ended March 31, 2021. The net interest incurred was immaterial for both the three months ended March 31, 2020 and 2021.

Commitments and Contingencies

Commitments and Contingencies	3 Months Ended
Commitments and Contingencies	Mar. 31, 2021
Commitments and Contingencies Disclosure [Abstract]
Commitments and Contingencies	Note 17—Commitments and Contingencies Environmental Matters The Company is subject to federal, state, local and foreign environmental laws and regulations. The Company does not anticipate any expenditures to comply with such laws and regulations that would have a material effect on the Company’s consolidated financial position, results of operations or liquidity. The Company believes that its operations comply, in all material respects, with applicable federal, state, local and foreign environmental laws and regulations. Litigation, Claims and Contingencies The Company may become party to various legal actions that arise in the ordinary course of its business. The Company is also subject to audit by tax and other authorities for varying periods in various federal, state, local and foreign jurisdictions, and disputes may arise during the course of these audits. It is impossible to determine the ultimate liabilities that the Company may incur resulting from any of these lawsuits, claims, proceedings, audits, commitments, contingencies and related matters or the timing of these liabilities, if any. If these matters were to ultimately be resolved unfavorably, it is possible that such an outcome could have a material adverse effect upon the Company’s consolidated financial position, results of operations, or liquidity. The Company does not, however, anticipate such an outcome and believes the ultimate resolution of these matters will not have a material adverse effect on the Company’s consolidated financial position, results of operations, or liquidity.

Leases

Leases	3 Months Ended
Leases	Mar. 31, 2021
Leases
Leases	Note 18—Leases Lessor Accounting The Company leases fueling station equipment to customers pursuant to agreements that contain an option to extend and an end-of-term purchase option. Receivables from these leases are accounted for as finance leases, specifically sales-type leases, and are included in “Other receivables” and “Notes receivable and other long-term assets, net” in the accompanying condensed consolidated balance sheets. The Company recognizes the net investment in the lease as the sum of the lease receivable and the unguaranteed residual value, both of which are measured at the present value using the interest rate implicit in the lease. During each of the three months ended March 31, 2020 and 2021, the Company recognized $0.1 million in “Interest income” on its lease receivables. The following schedule represents the Company’s maturities of lease receivables as of March 31, 2021 (in thousands): Fiscal year: 2021 $ 1,051 2022 1,182 2023 962 2024 962 2025 962 Thereafter 3,358 Total minimum lease payments 8,477 Less amount representing interest (2,230) Present value of lease receivables $ 6,247

Alternative Fuels Excise Tax Cr

Alternative Fuels Excise Tax Credit	3 Months Ended
Alternative Fuels Excise Tax Credit	Mar. 31, 2021
Alternative Fuel Excise Tax Credit
Alternative Fuels Excise Tax Credit	Note 19—Alternative Fuel Excise Tax Credit Under separate pieces of U.S. federal legislation, the Company has been eligible to receive the AFTC for its natural gas vehicle fuel sales made between October 1, 2006 and March 31, 2021. The AFTC is equal to $0.50 per gasoline gallon equivalent of CNG that the Company sold as vehicle fuel, and $0.50 per diesel gallon of LNG that the Company sold as vehicle fuel in 2020 and 2021. AFTC is currently available for vehicle fuel sales made through December 31, 2021 and may not be reinstated for vehicle fuel sales made after December 31, 2021. Based on the service relationship with its customers, either the Company or its customers claim the credit. The Company records its AFTC, if any, as revenue in its condensed consolidated statements of operations because the credits are fully payable to the Company and do not offset income tax liabilities. As such, the credits are not deemed income tax credits under the accounting guidance applicable to income taxes.

Related Party Transactions

Related Party Transactions	3 Months Ended
Related Party Transactions	Mar. 31, 2021
Related Party Transactions [Abstract]
Related Party Transactions	Note 20—Related Party Transactions Total S.E. During the three months ended March 31, 2020 and 2021, the Company recognized revenue of $1.0 million and $0.7 million, respectively, related to RINs sold to Total and its affiliates in the ordinary course of business and settlements on commodity swap contracts (Note 6). As of December 31, 2020 and March 31, 2021, the Company had receivables from Total and its affiliates of $0.9 million and $0.1 million, respectively. During the three months ended March 31, 2020 and 2021, the Company paid Total and its affiliates $0.2 million and $0.5 million, respectively, for expenses incurred in the ordinary course of business and settlements on commodity swap contracts (Note 6), and the guaranty fee under the CSA (Note 12). As of December 31, 2020 and March 31, 2021, the amount due to Total and its affiliates was immaterial. SAFE&CEC S.r.l. During each of the three months ended March 31, 2020 and 2021, the Company received $0.1 million from SAFE&CEC S.r.l. in the ordinary course of business. As of December 31, 2020 and March 31, 2021, the Company had receivables from SAFE&CEC S.r.l. of $0.2 million and $0.1 million, respectively. During the three months ended March 30, 2020 and 2021, the Company paid SAFE&CEC S.r.l. $0.4 million and $0.8 million, respectively, for parts and equipment in the ordinary course of business. As of December 31, 2020 and March 31, 2021, the Company had payables to SAFE&CEC S.r.l. of $0.9 million.

Subsequent Events

Subsequent Events	3 Months Ended
Subsequent Events	Mar. 31, 2021
Subsequent Events [Abstract]
Subsequent Events	Note 21—Subsequent Events bp Joint Venture See description of the bpJV and the bp JV Agreement set forth above in Note 3. Amazon Warrant On April 16, 2021, in connection with execution of a Project Addendum to Fuel Pricing Agreement (“Fuel Agreement”) with Amazon Logistics, Inc., a subsidiary of Amazon.com, Inc. (“Amazon”), the Company entered into a Transaction Agreement with Amazon (the “Transaction Agreement”), pursuant to which, among other things, the Company issued to Amazon.com NV Investment Holdings LLC, a subsidiary of Amazon (“Amazon Holdings”), a warrant (the “Warrant”) to purchase up to an aggregate of 53,141,755 shares (the “Warrant Shares”) of common stock, par value $0.0001 per share, of the Company (the “Common Stock”) at an exercise price of $13.49 per share, which was a 21.3% premium to the $11.12 closing price of the Company’s common stock on April 15, 2021. The Warrant Shares vest in multiple tranches, the first of which for 13,283,445 Warrant Shares vested upon execution of the Fuel Agreement. Subsequent tranches will vest over time based on fuel purchases by Amazon and its affiliates, up to a total of $500 million, excluding any payments attributable to “Pass Through Costs,” which consist all costs associated with the delivered cost of gas and applicable taxes determined by reference to the selling price, gallons or gas sold. Importantly, if all the vesting conditions of the Amazon Warrant are satisfied, Amazon will have purchased hundreds of millions of GGEs of RNG from the Company. Under the Transaction Agreement we are required to use commercially reasonable efforts to obtain the approval of our stockholders with respect to the issuance of Warrant Shares in excess of 50,595,531 shares of Common Stock (such number of shares, the “Share Cap”), as may be required pursuant to the Nasdaq Global Select Market’s (“Nasdaq”) Listing Rule 5635(b) (the “Stockholder Approval”). Until the Stockholder Approval is obtained, Nasdaq Listing Rule 5635(b) may restrict the issuance of shares of Common Stock exceeding the Share Cap pursuant to, and upon the exercise of, the Warrant. In connection with obtaining the Stockholder Approval and pursuant to the Transaction Agreement, the Company agreed to file a proxy statement and hold a meeting of its stockholders as promptly as practicable to obtain the Stockholder Approval. To the extent the Stockholder Approval is not obtained at such stockholder meeting, at Amazon’s request, the Company is required to cause another stockholder meeting to be held every twelve (12) months until either the Stockholder Approval is obtained, or the term of the Warrant expires. The Company will seek the Stockholder Approval at its 2021 annual meeting of stockholders, which is scheduled to be held on June 14, 2021. Amazon Holdings may not exercise the Warrant to the extent such exercise would cause Amazon Holdings to beneficially own more than 4.999% of the number of shares of Common Stock outstanding immediately after giving effect to such exercise (excluding any unvested portion of the Warrant) (the “Beneficial Ownership Limitation”). Amazon Holdings may, however, waive or modify the Beneficial Ownership Limitation by providing written notice to the Company sixty-one Plains Credit Facility On May 1, 2021, the Company entered into a Loan and Security Agreement (the “Plains LSA”) with PlainsCapital Bank (“Plains”) which provides the Company a $20.0 million revolving line of credit through May 1, 2022. The interest rate on amounts outstanding under the Plains LSA is the greater of the Prime Rate or 3.25%.

General (Policies)

General (Policies)	3 Months Ended
General (Policies)	Mar. 31, 2021
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Basis of Presentation	Basis of Presentation The accompanying interim unaudited condensed consolidated financial statements include the accounts of the Company and its subsidiaries, and, in the opinion of management, reflect all adjustments, which include only normal recurring adjustments, necessary to state fairly the Company’s consolidated financial position as of March 31, 2021, results of operations, comprehensive loss, and stockholders’ equity, and cash flows for the three months ended March 31, 2020 and 2021. All intercompany accounts and transactions have been eliminated in consolidation. The results of operations for the three month periods ended March 31, 2020 and 2021 are not necessarily indicative of the results to be expected for the year ending December 31, 2021 or for any other interim period or any future year. Certain information and disclosures normally included in the notes to consolidated financial statements have been condensed or omitted pursuant to the rules and regulations of the Securities and Exchange Commission (the “SEC”), but the resultant disclosures contained herein are in accordance with accounting principles generally accepted in the United States of America (“U.S. GAAP”) as they apply to interim reporting. The accompanying condensed consolidated financial statements should be read in conjunction with the consolidated financial statements as of and for the year ended December 31, 2020 that are included in the Company’s Annual Report on Form 10-K filed with the SEC on March 9, 2021.
Use of Estimates	Use of Estimates The preparation of condensed consolidated financial statements in conformity with U.S. GAAP requires management to make estimates and assumptions that affect the amounts reported in the accompanying condensed consolidated financial statements and these notes. Actual results could differ from those estimates and may result in material effects on the Company’s operating results and financial position. Significant estimates made in preparing the accompanying condensed consolidated financial statements include (but are not limited to) those related to revenue recognition, fair value measurements, goodwill and long-lived asset valuations and impairment assessments, income tax valuations and stock-based compensation expense.
Recently Adopted Accounting Pronouncements	Recently Adopted Accounting Pronouncements In December 2019, the Financial Accounting Standards Board (“FASB”) issued Accounting Standards Update ("ASU") No. 2019-12, Income Taxes (Topic 740): Simplifying the Accounting for Income Taxes
Revenue Recognition	Revenue Recognition Overview The Company recognizes revenue when control of the promised goods or services is transferred to its customers, in an amount that reflects the consideration to which it expects to be entitled in exchange for the goods or services. To achieve that core principle, a five-step approach is applied: (1) identify the contract with a customer, (2) identify the performance obligations in the contract, (3) determine the transaction price, (4) allocate the transaction price to the performance obligations in the contract, and (5) recognize revenue allocated to each performance obligation when the Company satisfies the performance obligation. A performance obligation is a promise in a contract to transfer a distinct good or service to the customer, and is the unit of account for revenue recognition.

Revenue from Contracts with C_2

Revenue from Contracts with Customers (Tables)	3 Months Ended
Revenue from Contracts with Customers (Tables)	Mar. 31, 2021
Revenue from Contract with Customer [Abstract]
Disaggregation of revenue	The table below presents the Company’s revenue disaggregated by revenue source (in thousands): Three Months Ended March 31, 2020 2021 Volume-related (1) $ 75,060 $ 68,126 Station construction sales 5,522 4,535 AFTC (2) 5,424 4,482 Total revenue $ 86,006 $ 77,143 (1) Includes changes in fair value of derivative instruments related to the Company’s commodity swap and customer fueling contracts associated with the Company’s Zero Now truck financing program. The amounts are classified as revenue because the Company’s commodity swap contracts are used to economically offset the risk associated with the diesel-to-natural gas price spread resulting from customer fueling contracts under the Company’s Zero Now truck financing program. See Note 6 for more information about these derivative instruments. For the three months ended March 31, 2020 and 2021, aggregate changes in the fair value of commodity swaps and customer fueling contracts amounted to a gain of $5.6 million and a loss of $2.0 million, respectively. (2) Represents the federal alternative fuel excise tax credit that we refer to as “AFTC,” which was extended for vehicle fuel sales made beginning January 1, 2021 through December 31, 2021. See Note 19 for more information.
Summary of contract balances	As of December 31, 2020 and March 31, 2021, the Company’s contract balances were as follows (in thousands): December 31, March 31, 2020 2021 Accounts receivable, net $ 61,784 $ 64,175 Contract assets - current $ 729 $ 812 Contract assets - non-current 3,998 3,951 Contract assets - total $ 4,727 $ 4,763 Contract liabilities - current $ 1,638 $ 2,561 Contract liabilities - non-current 59 59 Contract liabilities - total $ 1,697 $ 2,620

Cash, Cash Equivalents, and R_2

Cash, Cash Equivalents, and Restricted Cash (Tables)	3 Months Ended
Cash, Cash Equivalents, and Restricted Cash (Tables)	Mar. 31, 2021
Cash and Cash Equivalents [Abstract]
Schedule of cash and cash equivalents	Cash, cash equivalents and restricted cash as of December 31, 2020 and March 31, 2021 consisted of the following (in thousands): December 31, March 31, 2020 2021 Current assets: Cash and cash equivalents $ 108,977 $ 116,696 Total cash and cash equivalents $ 108,977 $ 116,696 Long-term assets: Restricted cash - standby letters of credit $ 4,000 $ — Restricted cash - held as collateral 7,000 7,003 Total long-term portion of restricted cash $ 11,000 $ 7,003 Total cash, cash equivalents and restricted cash $ 119,977 $ 123,699
Schedule of components of restricted cash	Cash, cash equivalents and restricted cash as of December 31, 2020 and March 31, 2021 consisted of the following (in thousands): December 31, March 31, 2020 2021 Current assets: Cash and cash equivalents $ 108,977 $ 116,696 Total cash and cash equivalents $ 108,977 $ 116,696 Long-term assets: Restricted cash - standby letters of credit $ 4,000 $ — Restricted cash - held as collateral 7,000 7,003 Total long-term portion of restricted cash $ 11,000 $ 7,003 Total cash, cash equivalents and restricted cash $ 119,977 $ 123,699

Short-Term Investments (Tables)

Short-Term Investments (Tables)	3 Months Ended
Short-Term Investments (Tables)	Mar. 31, 2021
Investments, Debt and Equity Securities [Abstract]
Summary of short-term investments	Short-term investments as of December 31, 2020 consisted of the following (in thousands): Gross Amortized Unrealized Estimated Cost Gain (Loss) Fair Value Municipal bonds and notes $ 28,998 $ — $ 28,998 Certificates of deposit 530 — 530 Total short-term investments $ 29,528 $ — $ 29,528 Short-term investments as of March 31, 2021 consisted of the following (in thousands): Gross Amortized Unrealized Estimated Cost Gain (Loss) Fair Value Municipal bonds and notes $ 28,999 $ — $ 28,999 Certificates of deposit 530 — 530 Total short-term investments $ 29,529 $ — $ 29,529

Derivative Instruments and He_2

Derivative Instruments and Hedging Activities (Tables)	3 Months Ended
Derivative Instruments and Hedging Activities (Tables)	Mar. 31, 2021
Derivative Instruments and Hedging Activities Disclosure [Abstract]
Summary of commodity derivative activity	Derivatives and embedded derivatives as of December 31, 2020 consisted of the following (in thousands): Gross Amounts Gross Amounts Net Amount Recognized Offset Presented Assets: Commodity swaps: Current portion of derivative assets, related party $ 1,591 $ — $ 1,591 Long-term portion of derivative assets, related party 4,057 — 4,057 Fueling agreements: Prepaid expenses and other current assets 249 — 249 Notes receivable and other long-term assets, net 542 — 542 Total derivative assets $ 6,439 $ — $ 6,439 Liabilities: Fueling agreements: Accrued liabilities $ 283 $ — $ 283 Other long-term liabilities 273 — 273 Total derivative liabilities $ 556 $ — $ 556 Derivatives and embedded derivatives as of March 31, 2021 consisted of the following (in thousands): Gross Amounts Gross Amounts Net Amount Recognized Offset Presented Assets: Commodity swaps: Current portion of derivative assets, related party $ 385 $ — $ 385 Long-term portion of derivative assets, related party 962 — 962 Fueling agreements: Prepaid expenses and other current assets 658 — 658 Notes receivable and other long-term assets, net 1,863 — 1,863 Total derivative assets $ 3,868 $ — $ 3,868 Liabilities: Fueling agreements: Accrued liabilities $ 11 $ — $ 11 Other long-term liabilities 19 — 19 Total derivative liabilities $ 30 $ — $ 30
Schedule of weighted-average price of open commodity swap contract	The following table reflects the weighted-average price of open commodity swap contracts as of December 31, 2020 and March 31, 2021, by year with associated volumes: December 31, 2020 March 31, 2021 Volumes Weighted-Average Price per Volumes Weighted-Average Price per Year (Diesel Gallons) Diesel Gallon (Diesel Gallons) Diesel Gallon 2021 5,000,000 $ 3.18 3,750,000 $ 3.18 2022 5,000,000 $ 3.18 5,000,000 $ 3.18 2023 5,000,000 $ 3.18 5,000,000 $ 3.18 2024 1,875,000 $ 3.18 1,875,000 $ 3.18

Fair Value Measurements (Tables

Fair Value Measurements (Tables)	3 Months Ended
Fair Value Measurements (Tables)	Mar. 31, 2021
Fair Value Disclosures [Abstract]
Schedule of estimated fair value of outstanding commodity swap contracts and embedded derivatives	The Company estimated the fair value of its outstanding commodity swap contracts based on the following inputs as of December 31, 2020 and March 31, 2021: December 31, 2020 March 31, 2021 Significant Unobservable Inputs Input Range Weighted Average Input Range Weighted Average ULSD Gulf Coast Forward Curve $1.47 - $1.54 $ 1.50 $1.66 - $1.72 $ 1.69 Historical Differential to PADD 3 Diesel $0.81 - $1.58 $ 0.99 $0.81 - $1.58 $ 1.00 Historical Differential to PADD 5 Diesel $1.66 - $2.58 $ 2.01 $1.75 - $2.58 $ 2.04 The Company estimated the fair value of embedded derivatives in its fueling agreements under the Zero Now December 31, 2020 March 31, 2021 Significant Unobservable Inputs Input Range Weighted Average Input Range Weighted Average ULSD Gulf Coast Forward Curve $1.47 - $1.54 $ 1.50 $1.66 - $1.72 $ 1.69 Historical Differential to PADD 3 Diesel $0.81 - $1.58 $ 0.99 $0.81 - $1.58 $ 1.00 Historical Differential to PADD 5 Diesel $1.66 - $2.58 $ 2.01 $1.75 - $2.58 $ 2.04
Schedule of information by level for assets and liabilities that are measured at fair value on a recurring basis	The following tables provide information by level for assets and liabilities that are measured at fair value on a recurring basis as of December 31, 2020 and March 31, 2021 (in thousands): December 31, 2020 Level 1 Level 2 Level 3 Assets: Available-for-sale securities (1) Municipal bonds and notes $ 28,998 $ — $ 28,998 $ — Certificates of deposit (1) 530 — 530 — Commodity swap contracts (2) 5,648 — — 5,648 Embedded derivatives (3) 791 — — 791 Liabilities: Embedded derivatives (3) $ 556 $ — $ — $ 556 March 31, 2021 Level 1 Level 2 Level 3 Assets: Available-for-sale securities (1) Municipal bonds and notes $ 28,999 $ — $ 28,999 $ — Certificates of deposit (1) 530 — 530 — Commodity swap contracts (2) 1,347 — — 1,347 Embedded derivatives (3) 2,521 — — 2,521 Liabilities: Embedded derivatives (3) $ 30 $ — $ — $ 30 (1) Included in "Short-term investments" in the accompanying condensed consolidated balance sheets. See Note 5 for more information. (2) Included in "Derivative assets, related party" and "Long-term portion of derivative assets, related party" in the accompanying condensed consolidated balance sheets. See Note 6 for more information. (3) Included in "Prepaid expenses and other current assets," “Notes receivable and other long-term assets, net," “Accrued liabilities” and “Other long-term liabilities” in the accompanying condensed consolidated balance sheets. See Note 6 for more information.
Schedule of reconciliation of the beginning and ending balances of items measured at fair value on a recurring basis that used significant unobservable inputs (Level 3)	The following table provides a reconciliation of the beginning and ending balances of items measured at fair value on a recurring basis as shown in the tables above that used significant unobservable inputs (Level 3), as well as the change in unrealized gains or losses for the periods included in earnings (in thousands): Assets: Assets: Liabilities: Liabilities: Commodity Embedded Commodity Embedded Liabilities: Swap Contracts Derivatives Swap Contracts Derivatives Warrants Balance as of December 31, 2019 $ 3,270 $ 723 $ (164) $ (81) $ (40) Settlements, net (24) — 56 — — Total gain (loss) 9,299 (580) 108 (3,227) (405) Balance as of March 31, 2020 $ 12,545 $ 143 $ — $ (3,308) $ (445) Balance as of December 31, 2020 $ 5,648 $ 791 $ — $ (556) $ — Settlements, net (225) — 38 — — Total gain (loss) (4,076) 1,730 (38) 526 — Balance as of March 31, 2021 $ 1,347 $ 2,521 $ — $ (30) $ — Change in unrealized gain (loss) for the three months ended March 31, 2020 included in earnings $ 9,275 $ (580) $ 164 $ (3,227) $ (405) Change in unrealized gain (loss) for the three months ended March 31, 2021 included in earnings $ (4,301) $ 1,730 $ — $ 526 $ —

Other Receivables (Tables)

Other Receivables (Tables)	3 Months Ended
Other Receivables (Tables)	Mar. 31, 2021
Receivables [Abstract]
Schedule of other receivables	Other receivables as of December 31, 2020 and March 31, 2021 consisted of the following (in thousands): December 31, March 31, 2020 2021 Loans to customers to finance vehicle purchases $ 394 $ 394 Accrued customer billings 6,335 6,280 Fuel tax credits 10,556 11,454 Other 6,370 7,541 Total other receivables $ 23,655 $ 25,669

Inventory (Tables)

Inventory (Tables)	3 Months Ended
Inventory (Tables)	Mar. 31, 2021
Inventory Disclosure [Abstract]
Schedule of inventories	Inventory as of December 31, 2020 and March 31, 2021 consisted of the following (in thousands): December 31, March 31, 2020 2021 Raw materials and spare parts $ 28,100 $ 27,523 Total inventory $ 28,100 $ 27,523

Land, Property and Equipment (T

Land, Property and Equipment (Tables)	3 Months Ended
Land, Property and Equipment (Tables)	Mar. 31, 2021
Property, Plant and Equipment [Abstract]
Summary of land, property and equipment	Land, property and equipment, net as of December 31, 2020 and March 31, 2021 consisted of the following (in thousands): December 31, March 31, 2020 2021 Land $ 3,476 $ 3,476 LNG liquefaction plants 94,633 94,633 Station equipment 344,839 346,961 Trailers 79,860 80,465 Other equipment 89,276 89,651 Construction in progress 73,272 72,872 685,356 688,058 Less accumulated depreciation (394,445) (404,694) Total land, property and equipment, net $ 290,911 $ 283,364

Accrued Liabilities (Tables)

Accrued Liabilities (Tables)	3 Months Ended
Accrued Liabilities (Tables)	Mar. 31, 2021
Payables and Accruals [Abstract]
Schedule of accrued liabilities	Accrued liabilities as of December 31, 2020 and March 31, 2021 consisted of the following (in thousands): December 31, March 31, 2020 2021 Accrued alternative fuels incentives (1) $ 18,175 $ 20,117 Accrued employee benefits 4,282 3,300 Accrued gas and equipment purchases 9,897 10,819 Accrued interest 512 868 Accrued property and other taxes 3,094 4,878 Accrued salaries and wages 7,646 2,918 Embedded derivatives 283 11 Other (2) 8,748 10,251 Total accrued liabilities $ 52,637 $ 53,162 (1) Includes the amount of RINs, LCFS Credits and the amount of AFTC payable to third parties. (2) No individual item in “Other” exceeds 5% of total current liabilities .

Debt (Tables)

Debt (Tables)	3 Months Ended
Debt (Tables)	Mar. 31, 2021
Debt Disclosure [Abstract]
Schedule of long-term debt	Debt obligations as of December 31, 2020 and March 31, 2021 consisted of the following (in thousands): December 31, 2020 Unamortized Debt Balance, Net of Principal Balance Financing Costs Financing Costs bp Loan $ 50,000 $ — $ 50,000 NG Advantage debt 29,535 117 29,418 SG Facility 5,100 — 5,100 Other debt 1,162 — 1,162 Total debt 85,797 117 85,680 Less amounts due within one year (3,631) (39) (3,592) Total long-term debt $ 82,166 $ 78 $ 82,088 March 31, 2021 Unamortized Debt Balance, Net of Principal Balance Financing Costs Financing Costs bp Loan $ 50,000 $ — $ 50,000 NG Advantage debt 28,837 106 28,731 SG Facility 7,000 — 7,000 Other debt 1,074 — 1,074 Total debt 86,911 106 86,805 Less amounts due within one year (6,793) (32) (6,761) Total long-term debt $ 80,118 $ 74 $ 80,044

Net Income (Loss) Per Share (Ta

Net Income (Loss) Per Share (Tables)	3 Months Ended
Net Income (Loss) Per Share (Tables)	Mar. 31, 2021
Earnings Per Share [Abstract]
Schedule of information required to compute basic and diluted net loss per share	The following table sets forth the computations of basic and diluted earnings (loss) per share for the three months ended March 31, 2020 and 2021 (in thousands except share and per share amounts): Three Months Ended March 31, 2020 2021 Net income (loss) attributable to Clean Energy Fuels Corp. $ 1,704 $ (7,169) Weighted-average common shares outstanding 204,992,555 198,995,453 Dilutive effect of potential common shares from restricted stock units and stock options 1,047,544 — Weighted-average common shares outstanding - diluted 206,040,099 198,995,453 Basic income (loss) per share $ 0.01 $ (0.04) Diluted income (loss) per share $ 0.01 $ (0.04)
Schedule of potentially dilutive securities that have been excluded from the diluted net loss per share calculations because their effect would have been antidilutive	The following potentially dilutive securities have been excluded from the diluted net income (loss) per share calculations because their effect would have been antidilutive. Although these securities were antidilutive for these periods, they could be dilutive in future periods. Three Months Ended March 31, 2020 2021 Stock options 7,536,325 9,673,902 Convertible notes 3,164,557 — Restricted stock units 219,241 1,243,946 Total 10,920,123 10,917,848

Stock-Based Compensation (Table

Stock-Based Compensation (Tables)	3 Months Ended
Stock-Based Compensation (Tables)	Mar. 31, 2021
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
Summary of compensation expense and related income tax benefit related to the stock-based compensation expense recognized	The following table summarizes the compensation expense and related income tax benefit related to the Company’s stock-based compensation arrangements recognized in the accompanying condensed consolidated statements of operations during the three months ended March 31, 2020 and 2021 (in thousands): Three Months Ended March 31, 2020 2021 Stock-based compensation expense, net of $0 tax in 2020 and 2021 $ 1,054 $ 3,367

Leases (Tables)

Leases (Tables)	3 Months Ended
Leases (Tables)	Mar. 31, 2021
Leases
Schedule of maturities of lease receivables	The following schedule represents the Company’s maturities of lease receivables as of March 31, 2021 (in thousands): Fiscal year: 2021 $ 1,051 2022 1,182 2023 962 2024 962 2025 962 Thereafter 3,358 Total minimum lease payments 8,477 Less amount representing interest (2,230) Present value of lease receivables $ 6,247

Revenue from Contracts with C_3

Revenue from Contracts with Customers - Disaggregation of Revenue (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Revenue from Contracts with Customers
Revenue	$ 77,143	$ 86,006
Volume -Related
Revenue from Contracts with Customers
Revenue	68,126	75,060
Gain (Loss) changes in fair value	5,600	(2,000)
Station construction sales
Revenue from Contracts with Customers
Revenue	4,535	5,522
AFTC
Revenue from Contracts with Customers
Revenue	$ 4,482	$ 5,424

Revenue from Contracts with C_4

Revenue from Contracts with Customers - Remaining Performance Obligations (Details) $ in Millions	Mar. 31, 2021USD ($)
Remaining Performance Obligations
Revenue, remaining performance obligation, amount	$ 9.6
Minimum
Remaining Performance Obligations
Revenue, remaining performance obligation, expected timing of satisfaction, period	12 months
Maximum
Remaining Performance Obligations
Revenue, remaining performance obligation, expected timing of satisfaction, period	24 months

Revenue from Contracts with C_5

Revenue from Contracts with Customers - Contract Balances (Details) - USD ($) $ in Thousands	Mar. 31, 2021	Dec. 31, 2020
Revenue from Contract with Customer [Abstract]
Accounts receivable, net	$ 64,175	$ 61,784
Contract Assets - Current	812	729
Contract Assets - Noncurrent	3,951	3,998
Contract Assets - Total	4,763	4,727
Contract Liabilities - Current	2,561	1,638
Contract Liabilities - Noncurrent	59	59
Contract Liabilities - Total	$ 2,620	$ 1,697

Revenue from Contracts with C_6

Revenue from Contracts with Customers - Contract Liabilities (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020	Dec. 31, 2020
Revenue from Contract with Customer [Abstract]
Contract Liabilities - Current	$ 2,561		$ 1,638
Contract with customer, liability, revenue recognized	$ 1,500	$ 3,900

Investments in Other Entities_2

Investments in Other Entities and Noncontrolling Interest in a Subsidiary - Total Joint Venture (Details) - USD ($) $ in Millions	Mar. 03, 2021	Jan. 02, 2019
Socit Gnrale \| SG Facility
Business Acquisition [Line Items]
Maximum borrowing capacity (up to)		$ 100
ADG RNG Production Facilities \| Socit Gnrale \| SG Facility
Business Acquisition [Line Items]
Maximum borrowing capacity (up to)	$ 20
ADG RNG Production Facilities \| Total JV
Business Acquisition [Line Items]
Investment commitment of equity in production projects	400
Investment commitment in joint venture	50
ADG RNG Production Facilities \| Total JV \| Total
Business Acquisition [Line Items]
Investment commitment in joint venture	$ 50

Investments in Other Entities_3

Investments in Other Entities and Noncontrolling Interest in a Subsidiary - bp Joint Venture (Details) - USD ($) $ in Millions	Apr. 13, 2021	Dec. 18, 2020
BP Products North America \| bp Loan
Business Acquisition [Line Items]
Debt issuance amount		$ 50
ADG RNG Production Facilities \| bpJV \| Subsequent Event
Business Acquisition [Line Items]
Investment commitment in joint venture	$ 30
ADG RNG Production Facilities \| bpJV \| Class A Units \| Subsequent Event
Business Acquisition [Line Items]
Value of units received	30
ADG RNG Production Facilities \| bpJV \| Class B Units \| Subsequent Event
Business Acquisition [Line Items]
Option to commit additional funds	20
ADG RNG Production Facilities \| bpJV \| bp \| Subsequent Event
Business Acquisition [Line Items]
Investment commitment in joint venture	50
ADG RNG Production Facilities \| bpJV \| bp \| Class A Units \| Subsequent Event
Business Acquisition [Line Items]
Value of units received	30
ADG RNG Production Facilities \| bpJV \| bp \| Class B Units \| Subsequent Event
Business Acquisition [Line Items]
Value of units received	$ 20

Investments in Other Entities_4

Investments in Other Entities and Noncontrolling Interest in a Subsidiary - SAFE&CEC S.r.l. (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020	Dec. 31, 2020	Dec. 29, 2017
Acquisition and Divestitures
Income (loss) from equity method investments	$ (426)	$ 145
SAFE&CEC S.r.l.
Acquisition and Divestitures
Ownership interest				49.00%
Income (loss) from equity method investments	400	$ 0
Investment balance	$ 23,300		$ 24,700
SAFE&CEC S.r.l. \| Landi Renzo S.p.A.
Acquisition and Divestitures
Ownership interest				51.00%

Investments in Other Entities_5

Investments in Other Entities and Noncontrolling Interest in a Subsidiary - NG Advantage (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020	Feb. 28, 2021	Dec. 31, 2020	Oct. 14, 2014
Acquisition and Divestitures
Outstanding balance	$ 86,805			$ 85,680
Loss from noncontrolling interest	278	$ 805
NG Advantage
Acquisition and Divestitures
Loss from noncontrolling interest	300	$ 800
Noncontrolling interest, fair value	$ 9,100			$ 9,300
NG Advantage \| Common unit purchase agreement
Acquisition and Divestitures
Ownership interest acquired					53.30%
Ownership interest			93.30%

Cash, Cash Equivalents and Rest

Cash, Cash Equivalents and Restricted Cash (Details) - USD ($) $ in Thousands	Mar. 31, 2021	Dec. 31, 2020	Mar. 31, 2020	Dec. 31, 2019
Restricted Cash
Cash and cash equivalents	$ 116,696	$ 108,977
Total cash and cash equivalents	116,696	108,977
Long-term portion of restricted cash	7,003	11,000
Total cash, cash equivalents and restricted cash	123,699	119,977	$ 73,526	$ 53,222
Amount in excess of FDIC and CDIC limits	115,400	107,600
Standby letters of credit
Restricted Cash
Long-term portion of restricted cash		4,000
Held as collateral
Restricted Cash
Long-term portion of restricted cash	$ 7,003	$ 7,000

Short-Term Investments (Details

Short-Term Investments (Details) - USD ($) $ in Thousands	Mar. 31, 2021	Dec. 31, 2020
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	$ 29,529	$ 29,528
Estimated Fair Value	29,529	29,528
Municipal bonds and notes
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	28,999	28,998
Estimated Fair Value	28,999	28,998
Certificates of deposit
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	530	530
Estimated Fair Value	$ 530	$ 530

Derivative Instruments and He_3

Derivative Instruments and Hedging Activities - Narrative (Details) - Not Designated as Hedging Instrument - Commodity swaps gal in Millions	1 Months Ended	3 Months Ended	12 Months Ended
	Oct. 31, 2018contractgal	Mar. 31, 2021$ / galgal	Dec. 31, 2020$ / galgal
Derivative [Line Items]
Derivative asset, number of instruments held \| contract	2
Volumes (Diesel Gallons) \| gal	5	15.6	16.9
Weighted -average price per diesel gallon (in usd per gallon) \| $ / gal		3.18	3.18

Derivative Instruments and He_4

Derivative Instruments and Hedging Activities - Summary of Commodity Derivative Activity (Details) - Not Designated as Hedging Instrument - USD ($) $ in Thousands	Mar. 31, 2021	Dec. 31, 2020
Derivative Assets
Gross Amounts Recognized	$ 3,868	$ 6,439
Net Amount Presented	3,868	6,439
Derivative Liability
Gross Amounts Recognized	30	556
Net Amount Presented	30	556
Current portion of derivative assets, related party \| Commodity swaps
Derivative Assets
Gross Amounts Recognized	385	1,591
Net Amount Presented	385	1,591
Long-term portion of derivative assets, related party \| Commodity swaps
Derivative Assets
Gross Amounts Recognized	962	4,057
Net Amount Presented	962	4,057
Prepaid expenses and other current assets \| Fueling agreements
Derivative Assets
Gross Amounts Recognized	658	249
Net Amount Presented	658	249
Notes receivable and other long-term assets, net \| Fueling agreements
Derivative Assets
Gross Amounts Recognized	1,863	542
Net Amount Presented	1,863	542
Accrued liabilities \| Fueling agreements
Derivative Liability
Gross Amounts Recognized	11	283
Net Amount Presented	11	283
Other long-term liabilities \| Fueling agreements
Derivative Liability
Gross Amounts Recognized	19	273
Net Amount Presented	$ 19	$ 273

Derivative Instruments and He_5

Derivative Instruments and Hedging Activities - Schedule of Weighted-Average Price of Open Commodity Wwap Contracts (Details) - Not Designated as Hedging Instrument	3 Months Ended	12 Months Ended
	Mar. 31, 2021$ / galgal	Dec. 31, 2020$ / galgal
Commodity Swap 2021
Derivative [Line Items]
Volumes (Diesel Gallons) \| gal	3,750,000	5,000,000
Weighted -Average Price per Diesel Gallon (in usd per gallon) \| $ / gal	3.18	3.18
Commodity Swap 2022
Derivative [Line Items]
Volumes (Diesel Gallons) \| gal	5,000,000	5,000,000
Weighted -Average Price per Diesel Gallon (in usd per gallon) \| $ / gal	3.18	3.18
Commodity Swap 2023
Derivative [Line Items]
Volumes (Diesel Gallons) \| gal	5,000,000	5,000,000
Weighted -Average Price per Diesel Gallon (in usd per gallon) \| $ / gal	3.18	3.18
Commodity Swap 2024
Derivative [Line Items]
Volumes (Diesel Gallons) \| gal	1,875,000	1,875,000
Weighted -Average Price per Diesel Gallon (in usd per gallon) \| $ / gal	3.18	3.18

Fair Value Measurements - Commo

Fair Value Measurements - Commodity Swap Contracts (Details) - Not Designated as Hedging Instrument - Valuation Technique, Discounted Cash Flow - Level 3	Mar. 31, 2021	Dec. 31, 2020
Commodity swaps \| Minimum \| ULSD Gulf Coast Forward Curve
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Derivative asset, measurement input	1.66	1.47
Commodity swaps \| Minimum \| Historical Differential to PADD 3 Diesel
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Derivative asset, measurement input	0.81	0.81
Commodity swaps \| Minimum \| Historical Differential to PADD 5 Diesel
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Derivative asset, measurement input	1.75	1.66
Commodity swaps \| Maximum \| ULSD Gulf Coast Forward Curve
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Derivative asset, measurement input	1.72	1.54
Commodity swaps \| Maximum \| Historical Differential to PADD 3 Diesel
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Derivative asset, measurement input	1.58	1.58
Commodity swaps \| Maximum \| Historical Differential to PADD 5 Diesel
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Derivative asset, measurement input	2.58	2.58
Commodity swaps \| Weighted Average \| ULSD Gulf Coast Forward Curve
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Derivative asset, measurement input	1.69	1.50
Commodity swaps \| Weighted Average \| Historical Differential to PADD 3 Diesel
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Derivative asset, measurement input	1	0.99
Commodity swaps \| Weighted Average \| Historical Differential to PADD 5 Diesel
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Derivative asset, measurement input	2.04	2.01
Fueling agreements \| Minimum \| ULSD Gulf Coast Forward Curve
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Derivative asset, measurement input	1.66	1.47
Fueling agreements \| Minimum \| Historical Differential to PADD 3 Diesel
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Derivative asset, measurement input	0.81	0.81
Fueling agreements \| Minimum \| Historical Differential to PADD 5 Diesel
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Derivative asset, measurement input	1.75	1.66
Fueling agreements \| Maximum \| ULSD Gulf Coast Forward Curve
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Derivative asset, measurement input	1.72	1.54
Fueling agreements \| Maximum \| Historical Differential to PADD 3 Diesel
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Derivative asset, measurement input	1.58	1.58
Fueling agreements \| Maximum \| Historical Differential to PADD 5 Diesel
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Derivative asset, measurement input	2.58	2.58
Fueling agreements \| Weighted Average \| ULSD Gulf Coast Forward Curve
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Derivative asset, measurement input	1.69	1.50
Fueling agreements \| Weighted Average \| Historical Differential to PADD 3 Diesel
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Derivative asset, measurement input	1	0.99
Fueling agreements \| Weighted Average \| Historical Differential to PADD 5 Diesel
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Derivative asset, measurement input	2.04	2.01

Fair Value Measurements - Trans

Fair Value Measurements - Transfers (Details) - USD ($) $ in Thousands	3 Months Ended	12 Months Ended
	Mar. 31, 2021	Dec. 31, 2020
Fair Value Disclosures [Abstract]
Asset transferred from level 1 to 2	$ 0	$ 0
Asset transferred from level 2 to 1	0	0
Asset transferred level 3 net	0	0
Liabilities transferred from level 1 to 2	0	0
Liabilities transferred from level 2 to 1	0	0
Liabilities transferred level 3 net	$ 0	$ 0

Fair Value Measurements - Asset

Fair Value Measurements - Assets and Liabilities (Details) - USD ($) $ in Thousands	Mar. 31, 2021	Dec. 31, 2020
Assets:
Available-for-sale securities	$ 29,529	$ 29,528
Short-term investments	29,529	29,528
Municipal bonds and notes
Assets:
Available-for-sale securities	28,999	28,998
Certificates of deposit
Assets:
Available-for-sale securities	530	530
Fair value measured on recurring basis \| Municipal bonds and notes
Assets:
Available-for-sale securities	28,999	28,998
Fair value measured on recurring basis \| Certificates of deposit
Assets:
Short-term investments	530	530
Fair value measured on recurring basis \| Commodity swap contracts
Assets:
Derivative assets	1,347	5,648
Fair value measured on recurring basis \| Embedded derivatives
Assets:
Derivative assets	2,521	791
Liabilities:
Derivative liabilities	30	556
Fair value measured on recurring basis \| Level 2 \| Municipal bonds and notes
Assets:
Available-for-sale securities	28,999	28,998
Fair value measured on recurring basis \| Level 2 \| Certificates of deposit
Assets:
Short-term investments	530	530
Fair value measured on recurring basis \| Level 3 \| Commodity swap contracts
Assets:
Derivative assets	1,347	5,648
Fair value measured on recurring basis \| Level 3 \| Embedded derivatives
Assets:
Derivative assets	2,521	791
Liabilities:
Derivative liabilities	$ 30	$ 556

Fair Value Measurements - Fair

Fair Value Measurements - Fair Value Recognition - Assets (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Reconciliation of the beginning and ending balances of assets measured at fair value using significant unobservable inputs (Level 3)
Fair Value, Asset, Recurring Basis, Still Held, Unrealized Gain (Loss), Statement of Income [Extensible List]	Revenue from Contract with Customer, Excluding Assessed Tax	Revenue from Contract with Customer, Excluding Assessed Tax
Commodity swap contracts
Reconciliation of the beginning and ending balances of assets measured at fair value using significant unobservable inputs (Level 3)
Beginning balance	$ 5,648	$ 3,270
Settlements, net	(225)	(24)
Total gain (loss)	(4,076)	9,299
Ending balance	1,347	12,545
Fair Value, Assets Measured on Recurring Basis, Change in Unrealized Gain (Loss)	(4,301)	9,275
Embedded derivatives
Reconciliation of the beginning and ending balances of assets measured at fair value using significant unobservable inputs (Level 3)
Beginning balance	791	723
Total gain (loss)	1,730	(580)
Ending balance	2,521	143
Fair Value, Assets Measured on Recurring Basis, Change in Unrealized Gain (Loss)	$ 1,730	$ (580)

Fair Value Measurements - Fai_2

Fair Value Measurements - Fair Value Recognition - Liabilities (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Reconciliation of the beginning and ending balances of liabilities measured at fair value using significant unobservable inputs (Level 3)
Fair Value, Liability, Recurring Basis, Still Held, Unrealized Gain (Loss), Statement of Income [Extensible List]	Unrealized Gain (Loss) on Commodity Contracts	Unrealized Gain (Loss) on Commodity Contracts
Commodity swap contracts
Reconciliation of the beginning and ending balances of liabilities measured at fair value using significant unobservable inputs (Level 3)
Beginning Balance		$ (164)
Settlements, net	$ 38	56
Total gain (loss)	(38)	108
Change in unrealized gain (loss) included in earnings		164
Embedded derivatives
Reconciliation of the beginning and ending balances of liabilities measured at fair value using significant unobservable inputs (Level 3)
Beginning Balance	(556)	(81)
Total gain (loss)	526	(3,227)
Ending Balance	(30)	(3,308)
Change in unrealized gain (loss) included in earnings	$ 526	(3,227)
Warrants
Reconciliation of the beginning and ending balances of liabilities measured at fair value using significant unobservable inputs (Level 3)
Beginning Balance		(40)
Total gain (loss)		(405)
Ending Balance		(445)
Change in unrealized gain (loss) included in earnings		$ (405)

Other Receivables (Details)

Other Receivables (Details) - USD ($) $ in Thousands	Mar. 31, 2021	Dec. 31, 2020
Other Receivables
Other receivables	$ 25,669	$ 23,655
Loans to customers to finance vehicle purchases
Other Receivables
Other receivables	394	394
Accrued customer billings
Other Receivables
Other receivables	6,280	6,335
Fuel tax credits
Other Receivables
Other receivables	11,454	10,556
Other
Other Receivables
Other receivables	$ 7,541	$ 6,370

Inventory (Details)

Inventory (Details) - USD ($) $ in Thousands	Mar. 31, 2021	Dec. 31, 2020
Inventory Disclosure [Abstract]
Raw materials and spare parts	$ 27,523	$ 28,100
Total inventory	$ 27,523	$ 28,100

Land, Property and Equipment (D

Land, Property and Equipment (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020	Dec. 31, 2020
Land, Property and Equipment
Land, property and equipment, gross	$ 688,058		$ 685,356
Less accumulated depreciation	(404,694)		(394,445)
Total land, property and equipment, net	283,364		290,911
Capitalized software costs, net	32,700		32,300
Accumulated amortization on the capitalized software costs	29,400		28,800
Amortization expense related to the capitalized software costs	500	$ 700
Amount included in accounts payable balances	1,400	$ 2,100
Land
Land, Property and Equipment
Land, property and equipment, gross	3,476		3,476
LNG liquefaction plants
Land, Property and Equipment
Land, property and equipment, gross	94,633		94,633
Station equipment
Land, Property and Equipment
Land, property and equipment, gross	346,961		344,839
Trailers
Land, Property and Equipment
Land, property and equipment, gross	80,465		79,860
Other equipment
Land, Property and Equipment
Land, property and equipment, gross	89,651		89,276
Construction in progress
Land, Property and Equipment
Land, property and equipment, gross	$ 72,872		$ 73,272

Accrued Liabilities (Details)

Accrued Liabilities (Details) - USD ($) $ in Thousands	Mar. 31, 2021	Dec. 31, 2020
Payables and Accruals [Abstract]
Accrued alternative fuels incentives	$ 20,117	$ 18,175
Accrued employee benefits	3,300	4,282
Accrued gas and equipment purchases	10,819	9,897
Accrued interest	868	512
Accrued property and other taxes	4,878	3,094
Accrued salaries and wages	2,918	7,646
Embedded derivatives	11	283
Other	10,251	8,748
Total accrued liabilities	$ 53,162	$ 52,637

Debt - Schedule of Debt (Detail

Debt - Schedule of Debt (Details) - USD ($) $ in Thousands	Mar. 31, 2021	Dec. 31, 2020
Principal Balances
Total debt	$ 86,911	$ 85,797
Less amounts due within one year	(6,793)	(3,631)
Total long-term debt	80,118	82,166
Unamortized Debt Financing Costs
Total debt	106	117
Less amounts due within one year	(32)	(39)
Total long-term debt	74	78
Balance, Net of Financing Costs
Total debt	86,805	85,680
Less amounts due within one year	(6,761)	(3,592)
Total long-term debt	80,044	82,088
bp Loan
Principal Balances
Total debt	50,000	50,000
Balance, Net of Financing Costs
Total debt	50,000	50,000
NG Advantage debt
Principal Balances
Total debt	28,837	29,535
Unamortized Debt Financing Costs
Total debt	106	117
Balance, Net of Financing Costs
Total debt	28,731	29,418
SG Facility
Principal Balances
Total debt	7,000	5,100
Balance, Net of Financing Costs
Total debt	7,000	5,100
Other debt
Principal Balances
Total debt	1,074	1,162
Balance, Net of Financing Costs
Total debt	$ 1,074	$ 1,162

Debt - SG Credit and TOTAL Cred

Debt - SG Credit and TOTAL Credit Support Agreement (Details) - USD ($) $ in Thousands	Jan. 02, 2019	Mar. 31, 2021	Mar. 12, 2021	Mar. 03, 2021	Dec. 31, 2020
Long-term debt [Line Items]
Outstanding amount		$ 86,911			$ 85,797
SG Facility \| Socit Gnrale
Long-term debt [Line Items]
Maximum borrowing capacity (up to)	$ 100,000
Commitment fee percentage	0.39%
Quarterly principal payments		2,500
Covenant for debt default	$ 20,000
Outstanding amount		$ 7,000
SG Facility \| Socit Gnrale \| London Interbank Offered Rate (LIBOR)
Long-term debt [Line Items]
Basis spread on variable rate	1.30%
SG Facility \| Socit Gnrale \| Station Build Costs
Long-term debt [Line Items]
Maximum borrowing capacity (up to)			$ 45,000
SG Facility \| Socit Gnrale \| ADG RNG Production Facilities
Long-term debt [Line Items]
Maximum borrowing capacity (up to)				$ 20,000
SG Facility \| Total Holdings USA Inc.
Long-term debt [Line Items]
Maximum borrowing capacity (up to)	$ 100,000
Interest rate per quarter	2.50%
Covenant for debt default	$ 20,000
SG Facility \| Total Holdings USA Inc. \| London Interbank Offered Rate (LIBOR)
Long-term debt [Line Items]
Basis spread on variable rate	1.00%

Debt - NG Advantage Debt and Fi

Debt - NG Advantage Debt and Financing Lease Obligations (Details) $ in Millions	Dec. 10, 2020USD ($)	Dec. 20, 2018USD ($)	Mar. 01, 2018USD ($)installment	Dec. 18, 2017USD ($)installment	Mar. 31, 2021USD ($)	Dec. 31, 2020USD ($)	Nov. 30, 2016USD ($)installment
Compression Station
Long-term debt [Line Items]
Purchase price		$ 7
Sale leaseback transaction, term		5 years
Annual rate (as a percent)		12.00%
Sale leaseback transaction, monthly rental payments		$ 0.1
BoA \| BoA MLA
Long-term debt [Line Items]
Interest rate				4.86%
Proceeds from sale of equipment in sale-leaseback agreement				$ 2.1
Sale leaseback transaction, term				5 years
Number of equal monthly installments \| installment				60
First National \| First National MLA
Long-term debt [Line Items]
Interest rate			9.28%
Net proceeds, financing activities			$ 6.3
Sale leaseback transaction, term			6 years
Number of equal monthly installments \| installment			72
Loan and Security Agreement [Member] \| 5.17% Term Loan \| Wintrust Commercial Finance
Long-term debt [Line Items]
Debt issuance amount							$ 4.7
Number of monthly installments \| installment							72
Interest rate							5.17%
NG Advantage debt \| Berkshire Bank \| Interest expense
Long-term debt [Line Items]
Loss on extinguishment of debt						$ 1.2
NG Advantage debt \| Long-term portion of restricted cash \| Berkshire Bank
Long-term debt [Line Items]
Loan pledged as collateral	$ 7
NG Advantage debt \| 5% maturing on January 1, 2026 \| Berkshire Bank
Long-term debt [Line Items]
Debt issuance amount	$ 14.5
Interest rate	5.00%
Period during which the debt instrument principal balance is required to be paid following its issuance	5 years
NG Advantage debt \| Revolving line of credit \| Berkshire Bank
Long-term debt [Line Items]
Maximum borrowing capacity (up to)	$ 1
Line of credit outstanding					$ 0

Debt - BP Loan (Details)

Debt - BP Loan (Details) - bp Loan - BP Products North America $ in Millions	Dec. 18, 2020USD ($)
Debt Instrument [Line Items]
Debt issuance amount	$ 50
London Interbank Offered Rate (LIBOR)
Debt Instrument [Line Items]
Basis spread on variable rate	4.33%

Debt - Other Debt (Details)

Debt - Other Debt (Details) - Other debt	Mar. 31, 2021	Dec. 31, 2020
Long-term debt [Line Items]
Weighted average interest rate	4.37%	4.38%
Maximum
Long-term debt [Line Items]
Interest rate	4.75%

Net Income (Loss) Per Share (De

Net Income (Loss) Per Share (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Earnings Per Share [Abstract]
Net income (loss) attributable to Clean Energy Fuels Corp.	$ (7,169)	$ 1,704
Weighted average common shares outstanding	198,995,453	204,992,555
Dilutive effect of potential common shares from restricted stock units and stock options		1,047,544
Weighted average common shares outstanding - diluted	198,995,453	206,040,099
Basic income (loss) per share (in dollars per share)	$ (0.04)	$ 0.01
Diluted income (loss) per share (in dollars per share)	$ (0.04)	$ 0.01

Net Income (Loss) Per Share - A

Net Income (Loss) Per Share - Anti-dilutive Securities (Details) - shares	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Net Loss Per Share
Anti-dilutive securities (in shares)	10,917,848	10,920,123
Stock options
Net Loss Per Share
Anti-dilutive securities (in shares)	9,673,902	7,536,325
Convertibles notes
Net Loss Per Share
Anti-dilutive securities (in shares)		3,164,557
Restricted stock units
Net Loss Per Share
Anti-dilutive securities (in shares)	1,243,946	219,241

Stock-Based Compensation (Detai

Stock-Based Compensation (Details) - USD ($) $ in Thousands	3 Months Ended
Stock-Based Compensation (Details) - USD ($) $ in Thousands	Mar. 31, 2021	Mar. 31, 2020
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
Stock-based compensation expense, net of $0 tax in 2020 and 2021	$ 3,367	$ 1,054
Stock-based compensation expense, tax	0	$ 0
Unrecognized compensation cost	$ 30,000
Unrecognized compensation cost, weighted-average period	2 years 3 months 18 days

Stockholders' Equity (Details)

Stockholders' Equity (Details) - USD ($) $ in Thousands	3 Months Ended		13 Months Ended
Stockholders' Equity (Details) - USD ($) $ in Thousands	Mar. 31, 2021	Mar. 31, 2020	Mar. 31, 2021	Mar. 12, 2020
Equity [Abstract]
Approved share repurchase program				$ 30,000
Cost to repurchase common stock		$ 4,244	$ 14,500
Repurchase of common stock (in shares)	0

Income Taxes (Details)

Income Taxes (Details) - USD ($) $ in Thousands	3 Months Ended
Income Taxes (Details) - USD ($) $ in Thousands	Mar. 31, 2021	Mar. 31, 2020
Income Tax Disclosure [Abstract]
Income tax expense	$ 83	$ 78
Unrecognized tax benefits, increase from portion of AFTC revenue offset by the fuel tax	$ 800

Leases - Narrative (Details)

Leases - Narrative (Details) - USD ($) $ in Millions	3 Months Ended
Leases - Narrative (Details) - USD ($) $ in Millions	Mar. 31, 2021	Mar. 31, 2020
Leases
Sales-type lease, interest income	$ 0.1	$ 0.1

Leases - Maturities of Lease Re

Leases - Maturities of Lease Receivables (Details) $ in Thousands	Mar. 31, 2021USD ($)
Fiscal year:
2021	$ 1,051
2022	1,182
2023	962
2024	962
2025	962
Thereafter	3,358
Total minimum lease payments	8,477
Less amount representing interest	(2,230)
Present value of lease receivables	$ 6,247

Alternative Fuel Excise Tax Cre

Alternative Fuel Excise Tax Credit (Details) - $ / gal	3 Months Ended	12 Months Ended
Alternative Fuel Excise Tax Credit (Details) - $ / gal	Mar. 31, 2021	Dec. 31, 2020
Alternative Fuel Excise Tax Credit
Federal alternative fuels tax credit - CNG (in dollars per gasoline gallon equivalent)	0.50	0.50
Federal alternative fuels tax credit - LNG (in dollars per liquid gallon)	0.50	0.50

Related Party Transactions (Det

Related Party Transactions (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020	Dec. 31, 2020
TOTAL S.E.
Related Party Transaction [Line Items]
Proceeds from related party	$ 0.7	$ 1
Receivables from related party	0.1		$ 0.9
Related party expense	0.5	0.2
SAFE&CEC S.r.l.
Related Party Transaction [Line Items]
Proceeds from related party	0.1	0.1
Receivables from related party	0.1		0.2
Related party expense	0.8	$ 0.4
Payable to related parties	$ 0.9		$ 0.9

Subsequent Events (Details)

Subsequent Events (Details) - USD ($) $ / shares in Units, $ in Millions	Apr. 16, 2021	May 01, 2021	Apr. 15, 2021	Mar. 31, 2021	Dec. 31, 2020
Subsequent Event [Line Items]
Common stock, par value (in dollars per share)				$ 0.0001	$ 0.0001
Subsequent Event
Subsequent Event [Line Items]
Common stock price (in dollars per share)			$ 11.12
Subsequent Event \| Plains LSA
Subsequent Event [Line Items]
Maximum borrowing capacity (up to)		$ 20
Subsequent Event \| Minimum \| Plains LSA
Subsequent Event [Line Items]
Interest rate (as a percent)		3.25%
Subsequent Event \| Transaction Agreement
Subsequent Event [Line Items]
Aggregate number of warrant shares (in shares)	53,141,755
Common stock, par value (in dollars per share)	$ 0.0001
Number of warrants vested (in shares)	13,283,445
Total discretionary fuel purchases	$ 500
Exercise price of the warrant (in dollars per share)	$ 13.49
Exercise price premium (as a percent)	21.30%
Aggregate number of warrant shares that may require stockholder approval (in shares)	50,595,531
Notification period to waive or modify Beneficial Ownership Limitation	61 days
Subsequent Event \| Transaction Agreement \| Maximum
Subsequent Event [Line Items]
Percentage of common stock outstanding owned (as a percent)	4.999%