For the quarterly period ended March 31, 2016

Indicate by check mark whether the registrant (1) has filed all reports required to be filed by Section 13 or 15(d) of the Securities Exchange Act of 1934 during the preceding 12 months (or for such shorter period that the registrant was required to file such reports), and (2) has been subject to such filing requirements for the past 90 days. Yes x No o

Indicate by check mark whether the registrant has submitted electronically and posted on its corporate Web site, if any, every Interactive Data File required to be submitted and posted pursuant to Rule 405 of Regulation S-T (§232,405 of this chapter) during the preceding 12 months (or for such shorter period that the registrant was required to submit and post such files). Yes x No o

Indicate by check mark whether the registrant is a shell company (as defined by Rule 12b-2 of the Act). Yes o No x

As of May 1, 2016, there were 105,397,670 shares of the registrant’s common stock, par value $0.0001 per share, issued and outstanding.

(In thousands, except share data, Unaudited)

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 otherwise) is engaged in the business of selling natural gas fueling solutions to its customers, primarily in the United States and Canada.

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 financial position, results of operations, comprehensive loss and cash flows as of and for the three months ended March 31, 2015 and 2016. All intercompany accounts and transactions have been eliminated in consolidation. The three month periods ended March 31, 2015 and 2016 are not necessarily indicative of the results to be expected for the year ending December 31, 2016 or for any other interim period or for any future year.

Certain information and disclosures normally included in the notes to the 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 (“US GAAP”) as they apply to interim reporting. The condensed consolidated financial statements should be read in conjunction with the consolidated financial statements as of and for the year ended December 31, 2015 that are included in the Company’s Annual Report on Form 10-K filed with the SEC on March 3, 2016.

During the three months ended March 31, 2016, the Company adopted Accounting Standards Update (ASU) No. 2015-03, Interest - Imputation of Interest, which requires that debt issuance costs be presented in the balance sheet as a deduction from the carrying amount of the related liability, rather than as a deferred charge. The standard is required to be applied on a retrospective basis. As a result of applying the standard, unamortized debt issuance costs of $273 were reclassed from Prepaid expenses and other current assets to Current portion of long-term debt and capital lease obligations and $4,991 were reclassed from Notes receivable and other long-term assets to Long-term debt and capital lease obligations as of March 31, 2015.

Use of Estimates:  The preparation of condensed consolidated financial statements in conformity with US GAAP requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities and the disclosure of contingent assets and liabilities at the date of the condensed consolidated financial statements and revenues and expenses recorded during the reporting period. Actual results could differ from those estimates. Significant estimates made in preparing the condensed consolidated financial statements include (but are not limited to) those related to revenue recognition, goodwill and long-lived intangible asset valuations and impairment assessments, income tax valuations, and stock-based compensation expense.

Revenue Recognition: Effective January 1, 2016, the Company implemented a cost tracking system that provides for a detailed tracking of costs incurred on its station construction projects on a project by project basis. As a result of implementing this tracking system, the Company is able to make reliable estimates as to the percentage that a project is complete at the end of each reporting period. Beginning January 1, 2016, the Company began using the percentage of completion method to recognize revenue for station construction projects using the cost-to-cost method. Under this method, the Company estimates the percentage of completion based on the costs incurred to date for each contract in comparison to the estimated total costs for such contract at completion. The Company historically recognized revenue on station construction projects using the completed-contract method because it did not have a reliable means to make estimates of the percentage of

Station construction contracts are generally short-term with an exception for larger more complex stations, which can take up to 24 months to complete. Management evaluates the performance of contracts on an individual contract basis. Contract price and cost estimates are reviewed periodically as work progresses and adjustments proportionate to the percentage of completion are reflected in contract revenues in the reporting period when such estimates are revised. The nature of accounting for contracts is such that refinements of the estimating process for changing conditions and new developments are continuous and characteristic of the process. Many factors can and do change during a contract performance period which can result in a change to contract profitability including differing site conditions, the availability of skilled contract labor, the performance of major suppliers and subcontractors, and unexpected changes in material costs. These factors may result in revision to costs and income and are recognized in the period in which the revisions become known. Provisions for estimated losses on uncompleted contracts are made in the period in which such losses become known. During the three months ended March 31, 2016, there were no losses on open contracts.

As a result of using the percentage of completion method to recognize revenues, station construction project sales during the three months ended March 31, 2016 provided $9,393 in revenues, $1,100 in operating income, and $0.01 of income per diluted share amounts for such period that would otherwise not have been recognized during such period under the completed contract method.

Note 2— Investments in Other Entities and Noncontrolling Interest in a Subsidiary

On September 16, 2014, the Company formed a joint venture with Mansfield Ventures LLC (“Mansfield”) called Mansfield Clean Energy Partners LLC (“MCEP”), which is designed to provide natural gas fueling solutions to bulk fuel haulers in the U.S. The Company and Mansfield each have a 50% ownership interest in MCEP. The Company accounts for its interest using the equity method of accounting, as the Company has the ability to exercise significant influence over MCEP’s operations. The Company recorded a loss from this investment of $204 and $74 for the three months ended March 31, 2015 and March 31, 2016, respectively, and has an investment balance of $4,695 and $4,621 at December 31, 2015 and March 31, 2016, respectively.

On October 14, 2014, the Company entered into a Common Unit Purchase Agreement (“UPA”) with NG Advantage, LLC (“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 large industrial and institutional energy users, such as hospitals, food processors, manufacturers and paper mills, which do not have direct access to natural gas pipelines. The Company viewed the acquisition as a strategic investment in the expansion of the Company’s initiative to deliver natural gas to industrial and institutional energy users .The results of NG Advantage’s operations have been included in the Company’s consolidated financial statements since October 14, 2014. The Company reported a loss from this noncontrolling interest of $380 and $299 for the three months ended March 31, 2015 and March 31, 2016, respectively. The noncontrolling interest was $26,393 and $26,094 at December 31, 2015 and March 31, 2016, respectively.

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 investments may be in excess of the Federal Deposit Insurance Corporation (“FDIC”), Canadian Deposit Insurance Corporation (“CDIC,”) and other foreign insurance limits. Financial instruments that potentially subject the Company to concentrations of credit risk consist principally of cash deposits. The amounts in excess of FDIC, CDIC and other foreign insurance limits were approximately $40,691 and $84,841 as of December 31, 2015 and March 31, 2016, 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. Restricted cash consisted of the following as of December 31, 2015 and March 31, 2016:

Note 5—Investments

The Company reviews available-for-sale investments for other-than-temporary 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. This evaluation is based on a number of factors, including the length of time and the extent to which the fair value has been below its cost basis and adverse conditions related specifically to the security, including any changes to the credit rating of the security. As of March 31, 2016, the Company believes its carrying values for its available-for-sale investments are properly recorded.

Short-term investments as of December 31, 2015 are summarized as follows:

Short-term investments as of March 31, 2016 are summarized as follows:

Other receivables at December 31, 2015 and March 31, 2016 consisted of the following:

Inventories consisted of the following as of December 31, 2015 and March 31, 2016:

Land, property and equipment at December 31, 2015 and March 31, 2016 are summarized as follows:

Included in land, property and equipment are capitalized software costs of $22,886 and $23,384 as of December 31, 2015 and March 31, 2016, respectively. The accumulated amortization on the capitalized software costs is $13,793 and $14,731 as of December 31, 2015 and March 31, 2016, respectively. The Company recorded $716 and $938 of amortization expense related to the capitalized software costs during the three months ended March 31, 2015 and March 31, 2016, respectively.

As of March 31, 2015 and March 31, 2016, $13,771 and $6,077, respectively, are included in accounts payable and accrued liabilities balances, which amounts are related to purchases of property and equipment. These amounts are excluded from the condensed consolidated statements of cash flows as they are non-cash investing activities.

Accrued liabilities at December 31, 2015 and March 31, 2016 consisted of the following:

Note 10—Debt

Debt and capital lease obligations at December 31, 2015 and March 31, 2016 consisted of the following and are further discussed below:

(1) Included in the 7.5% Notes is $65,000 in principal amount held by T. Boone Pickens, which are classified as “Long-term debt, related party” on the condensed consolidated balance sheet. See below for additional information.

On July 11, 2011, the Company entered into a loan agreement (the “CHK Agreement”) with Chesapeake NG Ventures Corporation (“Chesapeake”), an indirect wholly owned subsidiary of Chesapeake Energy Corporation, whereby Chesapeake agreed to purchase from the Company up to $150,000 of debt securities (the “CHK Financing”) pursuant to the issuance of three convertible promissory notes over a three-year period, each having a principal amount of $50,000 (each a “CHK Note” and collectively the “CHK Notes” and, together with the CHK Agreement and other transaction documents, the “CHK Loan Documents”). The first CHK Note was issued on July 11, 2011 and the second CHK Note was issued on July 10, 2012.

On June 14, 2013 (the “Transfer Date”), Boone Pickens and Green Energy Investment Holdings, LLC, an affiliate of Leonard Green & Partners, L.P. (collectively, the “Buyers”), and Chesapeake entered into a note purchase agreement (“Note Purchase Agreement”) pursuant to which Chesapeake sold the outstanding CHK Notes (the “Sale”) to the Buyers. Chesapeake assigned to the Buyers all of its right, title and interest under the CHK Loan Documents (the “Assignment”), and each Buyer severally assumed all of the obligations of Chesapeake under the CHK Loan Documents arising after the Sale and the Assignment including, without limitation, the obligation to advance an additional $50,000 to the Company in June 2013 (the “Assumption”). The Company also entered into the Note Purchase Agreement for the purpose of consenting to the Sale, the Assignment and the Assumption.

Contemporaneously with the execution of the Note Purchase Agreement, the Company entered into a loan agreement with each Buyer (collectively, the “Amended Agreements”). The Amended Agreements have the same terms as the CHK Agreement, other than changes to reflect the new ownership of the CHK Notes. Immediately following execution of the Amended Agreements, the Buyers delivered $50,000 to the Company in satisfaction of the funding requirement they had

assumed from Chesapeake (the “June Advance”). In addition, the Company canceled the existing CHK Notes and re-issued replacement notes, and the Company also issued notes to the Buyers in exchange for the June Advance (the re-issued replacement notes and the notes issued in exchange for the June Advance are referred to herein as the “7.5% Notes”).

The 7.5% Notes have the same terms as the original CHK Notes, other than the changes to reflect their different holders. They bear interest at the rate of 7.5% per annum and are convertible at the option of the holder into shares of the Company’s common stock at a conversion price of $15.80 per share (the “7.5% Notes Conversion Price”). Upon written notice to the Company, the holders of the 7.5% Notes have the right to exchange all or any portion of the principal and accrued and unpaid interest under each such note for shares of the Company’s common stock at the 7.5% Notes Conversion Price. Additionally, subject to certain restrictions, the Company can force conversion of each 7.5% Note into shares of its common stock if, following the second anniversary of the issuance of a 7.5% Note, such shares trade at a 40% premium to the 7.5% Notes Conversion Price for at least 20 trading days in any consecutive 30 trading day period. The entire principal balance of each 7.5% Note is due and payable seven years following its original issuance date and the Company may repay each 7.5% Note in shares of its common stock or cash. All of the shares issuable upon conversion of the 7.5% Notes have been registered for resale by their holders pursuant to a registration statement that has been filed with and declared effective by the Securities and Exchange Commission. The Amended Agreements restrict the use of the proceeds of the 7.5% Notes to financing the development, construction and operation of LNG stations and payment of certain related expenses. The Amended Agreements also provide for customary events of default which, if any of them occurs, would permit or require the principal of, and accrued interest on, the 7.5% Notes to become, or to be declared, due and payable. No events of default under the 7.5% Notes had occurred as of March 31, 2016.

On August 27, 2013, Green Energy Investment Holdings, LLC transferred $5,000 in principal amount of its 7.5% Notes to certain third parties.

As a result of the foregoing transactions, (i) Boone Pickens holds 7.5% Notes in the aggregate principal amount of $65,000, which 7.5% Notes are convertible into approximately 4,113,924 shares of the Company’s common stock at the 7.5% Notes Conversion Price, (ii) Green Energy Investment Holdings, LLC holds 7.5% Notes in the aggregate principal amount of $80,000, which 7.5% Notes are convertible into approximately 5,063,291 shares of the Company’s common stock at the 7.5% Notes Conversion Price, and (iii) other third parties hold 7.5% Notes in the aggregate principal amount of $5,000, which 7.5% Notes are convertible into approximately 316,456 shares of the Company's common stock at the 7.5% Notes Conversion Price.

On August 24, 2011, the Company entered into convertible note purchase agreements (each, an “SLG Agreement” and collectively the “SLG Agreements”) with each of Springleaf Investments Pte. Ltd., a wholly-owned subsidiary of Temasek Holdings Pte. Ltd., Lionfish Investments Pte. Ltd., an investment vehicle managed by Seatown Holdings International Pte. Ltd., and Greenwich Asset Holding Ltd., a wholly-owned subsidiary of RRJ Capital Master Fund I, L.P. (each, a “Purchaser” and collectively, the “Purchasers”), whereby the Purchasers agreed to purchase from the Company $150,000 of 7.5% convertible promissory notes due in August 2016 (each a “SLG Note” and collectively the “SLG Notes”). The transaction closed and the SLG Notes were issued on August 30, 2011. On March 1, 2012, Springleaf Investments Pte. LTD transferred $24,000 in principal amount of the SLG Notes to Baytree Investments (Mauritius) Pte. Ltd.

The SLG Notes bear interest at the rate of 7.5% per annum and are convertible at the option of each Purchaser into shares of the Company’s common stock at a conversion price of $15.00 per share (the “SLG Conversion Price”). Upon written notice to the Company, the holders of the SLG Notes have the right to exchange all or any portion of the principal and accrued and unpaid interest under each such note for shares of the Company’s common stock at the SLG Conversion Price. Additionally, subject to certain restrictions, the Company can force conversion of each SLG Note into shares of its common stock if, following the second anniversary of the issuance of the SLG Notes, such shares trade at a 40% premium to the SLG Conversion Price for at least 20 trading days in any consecutive 30 trading day period. The entire principal balance of each SLG Note is due and payable five years following its issuance and the Company may repay the principal balance of each SLG Note in shares of its common stock or cash. All of the shares issuable upon conversion of the SLG Notes have been registered for resale by their holders pursuant to a registration statement that has been filed with and declared effective by the Securities and Exchange Commission. The SLG Agreements also provide for customary events of default which, if any of them occurs, would permit or require the principal of, and accrued interest on, the SLG Notes to become, or to be declared, due and payable. No events of default under the SLG Notes had occurred as of March 31, 2016.

In April 2012, $1,003 of principal and accrued interest under an SLG Note was converted by the holder thereof into 66,888 shares of the Company’s common stock. In January and February 2013, $4,030 of principal and accrued interest under an SLG Note was converted by the holder thereof into 268,664 shares of the Company’s common stock.

On March 1, 2016, the Company repaid $60,000 in cash of the $145,000 outstanding principal amount and $1,812 in cash of accrued interest of the SLG Notes.

In September 2013, the Company completed a private offering of $250,000 in principal amount of 5.25% Convertible Senior Notes due 2018 (the “5.25% Notes”) and entered into an indenture governing the 5.25% Notes (the “Indenture”).

The net proceeds from the sale of the 5.25% Notes after the payment of certain debt issuance costs of $7,805 were $242,195. The Company has used, and intends to continue to use, the net proceeds from the sale of the 5.25% Notes to fund capital expenditures and for general corporate purposes.

The 5.25% Notes bear interest at a rate of 5.25% per annum, payable semi-annually in arrears on October 1 and April 1 of each year, beginning on April 1, 2014. The 5.25% Notes will mature on October 1, 2018, unless purchased, redeemed or converted prior to such date in accordance with their terms and the terms of the Indenture.

Holders may convert their 5.25% Notes, at their option, at any time prior to the close of business on the business day immediately preceding the maturity date of the 5.25% Notes. Upon conversion, the Company will deliver a number of shares of its common stock, per $1 principal amount of 5.25% Notes, equal to the conversion rate then in effect (together with a cash payment in lieu of any fractional shares). The initial conversion rate for the 5.25% Notes is 64.1026 shares of the Company’s common stock per $1 principal amount of Notes (which is equivalent to an initial conversion price of approximately $15.60 per share of the Company’s common stock). The conversion rate is subject to adjustment upon the occurrence of certain specified events as described in the Indenture. Upon the occurrence of certain corporate events prior to the maturity date of the 5.25% Notes, the Company will, in certain circumstances, in addition to delivering the number of shares of the Company’s common stock deliverable upon conversion of the 5.25% Notes based on the conversion rate then in effect (together with a cash payment in lieu of any fractional shares), pay holders that convert their 5.25% Notes a cash make-whole payment in an amount as calculated in accordance with the Indenture. The Company may, at its option, irrevocably elect to settle its obligation to pay any such make-whole payment in shares of its common stock instead of in cash. The amount of any make-whole payment, whether it is settled in cash or in shares of the Company’s common stock upon the Company’s election, will be determined based on the date on which the corporate event occurs or becomes effective and the stock price paid (or deemed to be paid) per share of the Company’s common stock in the corporate event, as described in the Indenture.

The Company may not redeem the 5.25% Notes prior to October 5, 2016. On or after October 5, 2016, the Company may, at its option, redeem for cash all or any portion of the 5.25% Notes if the closing sale price of the Company’s common stock for at least 20 trading days (whether or not consecutive) during any 30 consecutive trading day period ending on, and including, the trading day immediately preceding the date on which notice of redemption is provided, exceeds 160% of the conversion price on each applicable trading day. In the event of the Company’s redemption of the 5.25% Notes, the redemption price will equal 100% of the principal amount of the 5.25% Notes to be redeemed, plus accrued and unpaid interest to, but excluding, the redemption date. No sinking fund is provided for in the 5.25% Notes.

If the Company undergoes a fundamental change (as defined in the Indenture) prior to the maturity date of the 5.25% Notes, subject to certain conditions as described in the Indenture, holders may require the Company to purchase, for cash, all or any portion of their 5.25% Notes at a repurchase price equal to 100% of the principal amount of the 5.25% Notes to be repurchased, plus accrued and unpaid interest to, but excluding, the fundamental change purchase date.

The Indenture contains customary events of default with customary cure periods, including, without limitation, failure to make required payments or deliveries of shares of the Company’s common stock when due under the Indenture, failure to comply with certain covenants under the Indenture, failure to pay when due or acceleration of certain other indebtedness of the Company or certain of its subsidiaries, and certain events of bankruptcy and insolvency of the Company or certain of its subsidiaries. The occurrence of an event of default under the Indenture will allow either the trustee or the holders of at least 25% in principal amount of the then-outstanding 5.25% Notes to accelerate, or upon an event of default arising from certain events of bankruptcy or insolvency of the Company, will automatically cause the acceleration of, all amounts due under the 5.25% Notes. No events of default under the 5.25% Notes had occurred as of March 31, 2016.

The 5.25% Notes are senior unsecured obligations of the Company and rank senior in right of payment to the Company’s future indebtedness that is expressly subordinated in right of payment to the 5.25% Notes; equal in right of payment to the Company’s unsecured indebtedness that is not so subordinated; effectively junior to any of the Company’s secured indebtedness to the extent of the value of the assets securing such indebtedness; and structurally junior to all indebtedness (including trade payables) of the Company’s subsidiaries.

On February 18, 2016, the Company paid $16,761 in cash to repurchase and retire $32,500 in principal amount of the 5.25% Notes, together with accrued and unpaid interest thereon, resulting in a $15,923 gain, net of related deferred financing costs.

Subsequent to March 31, 2016, on April 6, 2016, the Company repurchased and retired an additional $6,500 in principal amount of the 5.25% Notes, together with accrued and unpaid interest thereon, with $3,926 in cash, and on April 19, 2016, the Company entered into a privately negotiated exchange agreement with certain holders (the “Holders”) of the 5.25% Notes. Under the exchange agreement, the Holders agreed to exchange an aggregate principal amount of $25,000 of 5.25% Notes and accrued but unpaid interest in exchange for shares of the Company’s common stock (the “Shares”). Upon the consummation of all of the transactions contemplated by the exchange agreement, which occurred on May 4, 2016, the Company issued 6,265,829 shares to the Holders. Immediately following the exchange of the Notes contemplated by the exchange agreement, $186,000 in aggregate principal amount of the 5.25% Notes remained outstanding.

On February 29, 2016, the Company entered into a Loan and Security Agreement (“LSA”) with PlainsCapital Bank (“Plains”), pursuant to which Plains agreed to lend the Company up to $50,000 on a revolving basis from time to time for a term of one year (the “Credit Facility”). All amounts advanced under the Credit Facility are due and payable on February 28, 2017. Simultaneously, the Company drew down $50,000 under this Credit Facility. The Credit Facility is evidenced by a promissory note the Company issued on February 29, 2016 in favor of Plains (the “Plains Note”). Interest on the Plains Note is payable monthly and accrues at a rate equal to the greater of (i) the then-current LIBOR rate plus 2.30% or (ii) 2.70%. As collateral security for the prompt payment in full when due of our obligations to Plains under the LSA and the Plains Note, the Company pledged to and granted Plains a security interest in all of its right, title and interest in the cash and corporate and municipal bonds rated AAA, AA or A by Standard & Poor’s Rating Services that the Company holds in an account at Plains. In connection with such pledge and security interest granted under the Credit Facility, on February 29, 2016, the Company entered into a Pledged Account Agreement with Plains and PlainsCapital Bank - Wealth Management and Trust (the “Pledge Agreement” and collectively with the LSA and the Plains Note, the “Plains Loan Documents”).The Plains Loan Documents include certain covenants and also provide for customary events of default, which, if any of them occurs, would permit or require, among other things, the principal of, and accrued interest on, the Credit Facility to become, or to be declared, due and payable. Events of default under the Plains Loan Documents include, among others, the occurrence of certain bankruptcy events, the failure to make payments when due under the Plains Note and the transfer or disposal of the collateral under the LSA. No events of default under the Plains Loan Documents had occurred as of March 31, 2016.

On March 19, 2014, Canton Renewables, LLC (“Canton”), a wholly owned subsidiary of the Company, completed the issuance of Solid Waste Facility Limited Obligation Revenue Bonds (Canton Renewables, LLC — Sauk Trail Hills Project) Series 2014 in the aggregate principal amount of $12,400 (the “Canton Bonds”).

The Canton Bonds were issued by the Michigan Strategic Fund (the “Issuer”) and the proceeds of such issuance were loaned by the Issuer to Canton pursuant to a loan agreement that became effective on March 19, 2014 (the “Loan Agreement”). The Canton Bonds are expected to be repaid from revenue generated by Canton from the sale of RNG and are secured by the revenue and assets of Canton. The Canton Bond repayments will be amortized through July 1, 2022, the average coupon interest rate on the Canton Bonds is 6.6%, and all but $1,000 of the principal amount of the Canton Bonds is non-recourse to Canton’s parent companies, including the Company.

The Loan Agreement contains customary events of default, with customary cure periods, including, without limitation, failure to make required payments when due under the Loan Agreement, failure to comply with certain covenants under the Loan Agreement, certain events of bankruptcy and insolvency of Canton, and the existence of an event of default under the indenture governing the Canton Bonds that was entered into between the Issuer and The Bank of New York Mellon Trust Company, N.A., as trustee. The occurrence of an event of default under the Loan Agreement will allow the Issuer or the trustee to accelerate all amounts due under the Loan Agreement. No events of default under the Loan Agreement had occurred as of March 31, 2016.

The Company has other debt due at various dates through 2020 bearing interest at rates up to 20.91% and with a weighted average interest rate of 6.35% and 6.65% as of December 31, 2015 and March 31, 2016, respectively.

On November 7, 2012, the Company, through two wholly owned subsidiaries (the “Borrowers”), entered into a credit agreement (as amended, the “Credit Agreement”) with General Electric Capital Corporation (“GE”). Pursuant to the Credit Agreement, GE agreed to loan to the Borrowers up to an aggregate of $200,000 to finance the development, construction and operation of two LNG plants (individually a “Project” and together the “Projects”). Concurrently with the execution of the Credit Agreement, the Company issued to GE a warrant to purchase up to 5,000,000 shares of its common stock at a price of $0.01 per share (the "GE Warrant"). See Note 11 for further information.

On December 31, 2015, the Company terminated the Credit Agreement and related documents except for the GE Warrant, which remains outstanding, although 4,000,000 shares subject to the GE Warrant will not vest and will not become exercisable. No amounts had been borrowed by the Borrowers under the Credit Agreement as of its termination. As a result of the termination of the Credit Agreement, all related unamortized deferred financing costs that were to be amortized to interest expense in future periods have been eliminated from the balance sheet and a non-cash charge totaling $54.9 million was recorded in interest expense in the fourth quarter of 2015.

The Credit Agreement included a commitment fee on the unutilized loan amounts of 0.5% per annum, which was $250 for the three months ended March 31, 2015 and was charged to interest expense in the consolidated statement of operations.

Note 11—Net Income (Loss) Per Share

On December 31, 2015, the Company terminated the GE Credit Agreement and as a result, 4,000,000 shares of the 5,000,000 shares subject to the GE Warrant will not vest and will not become exercisable. The remaining 1,000,000 shares of common stock issuable upon exercise of the GE Warrant are included in the basic and diluted net income (loss) per share calculations, as 500,000 shares were exercisable as of the execution of the GE Credit Agreement and an additional 500,000 shares issuable upon exercise of the GE Warrant became exercisable on December 31, 2014. See Note 10 for further information. The information required to compute basic and diluted net income (loss) per share is as follows:

Note 12—Stock-Based Compensation

As of March 31, 2016, there was $14,005 of total unrecognized compensation cost related to non-vested shares underlying outstanding stock options and restricted stock units, which is expected to be expensed over a weighted-average period of approximately 2.1 years.

Note 13—Environmental Matters, Litigation, Claims, Commitments and Contingencies

Note 14—Income Taxes

The Company’s income tax (expense) benefit for the three months ended March 31, 2015 and March 31, 2016 was $(854) and $(381), respectively.  Tax expense for all periods was comprised of taxes due on the Company’s U.S. and foreign operations. The decrease in the Company’s income tax provision for the three months ended March 31, 2016 as compared to the tax provision for the three months ended March 31, 2015 was primarily attributed to a decrease in the earnings of foreign subsidiaries. The effective tax rate for the three months ended March 31, 2015 and 2016 are different from the federal statutory tax rate primarily as a result of losses for which no tax benefit has been recognized.

The Company did not record a change in its liability for unrecognized tax benefits or penalties in the three months ended March 31, 2015 or March 31, 2016, and the net interest incurred was immaterial for such periods.

Note 15—Fair Value Measurements

As of March 31, 2016, the Company’s financial instruments consisted of available-for-sale securities, debt instruments, and liability-classified warrants (which include Series I Warrants). The Company’s available-for-sale securities 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 liability-classified warrants are classified within Level 3 because the Company uses the Black-Scholes model to estimate the fair value based on inputs that are not observable in any market. The fair value of the Company's debt instruments approximated their carrying values at December 31, 2015. As of March 31, 2016, the fair value of the Company's debt instruments approximated their carrying values, with the exception of the 5.25% Notes, for which the fair value was approximately $208,500 based on activity relating to such notes in April and May of 2016. See Note 10 for further information.

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, 2015 and March 31, 2016, respectively:

(1) Included in short-term investments in the condensed consolidated balance sheets. See Note 5 for further information.

No impairments of long-lived assets measured at fair value on a non-recurring basis have been incurred during the three months ended March 31, 2015 and 2016. The Company’s use of these non-financial assets does not differ from their highest and best use as determined from the perspective of a market participant.

Note 16—Recently Adopted Accounting Changes and Recently Issued Accounting Standards

In March 2016, the FASB issued Accounting Standards Update ("ASU") No. 2016-09, Compensation – Stock Compensation (Topic 718). The pronouncement was issued to simplify the accounting for share-based payment transactions, including income tax consequences, the classification of awards as either equity or liabilities, and the classification on the statement of cash flows. This pronouncement is effective for reporting periods beginning after December 15, 2016. Early adoption is allowed in an interim or annual accounting period. The Company is currently evaluating the impact this ASU will have on its consolidated financial statements and related disclosures.

In February 2016, the FASB issued ASU No. 2016-02, Leases. The new standard will require most leases to be recognized on the balance sheet which will increase reported assets and liabilities. Lessor accounting remains substantially similar to current guidance. The new standard is effective for annual and interim periods in fiscal years beginning after December 15, 2018, which for the Company is the first quarter of fiscal 2019 and mandates a modified retrospective transition method. The Company is currently evaluating the impact this ASU will have on its consolidated financial statements and related disclosures.

In January 2016, the FASB issued ASU No. 2016-01, Recognition and Measurement of Financial Assets and Financial Liabilities. The new standard requires equity investments to be measured at fair value with changes in fair value recognized in net income, simplifies the impairment assessment of equity investments without readily determinable fair values, eliminates the requirement to disclose the methods and significant assumptions used to estimate fair value, requires use of the exit price notion when measuring fair value, requires separate presentation in certain financial statements, and requires an evaluation of the need for a valuation allowance on a deferred tax asset related to available-for-sale securities. The new standard is effective for fiscal years beginning after December 15, 2017, which for the Company is the first quarter of fiscal 2018. The Company is currently evaluating the impact this ASU will have on its consolidated financial statements and related disclosures.

In August 2015, the FASB issued ASU 2015-14, Revenue from Contracts with Customers, Deferral of the Effective Date” which defers the new revenue guidance ASU 2014-09 to be effective for annual reporting periods beginning after 15 December 2017, including interim reporting periods within that reporting period, which for the Company is the first quarter of fiscal 2018, using one of two prescribed retrospective methods. In May 2014, the FASB issued ASU No. 2014-9, Revenue from Contracts with Customers, amending revenue recognition guidance and requiring more detailed disclosures to enable users of financial statements to understand the nature, amount, timing, and uncertainty of revenue and cash flows arising from contracts with customers. The Company is currently in the process of evaluating the impact of adoption on its consolidated financial statements and related disclosures. The Company is currently evaluating the impact this ASU will have on its consolidated financial statements and related disclosures and has not yet selected a transition method.

In August 2014, the FASB issued ASU No. 2014-15, to communicate amendments to FASB Accounting Standards Codification Subtopic 205-40, "Disclosure of Uncertainties about an Entity's Ability to Continue as a Going Concern." The ASU requires management to evaluate relevant conditions, events and certain management plans that are known or reasonably knowable as of the evaluation date when determining whether substantial doubt about an entity's ability to continue as a going concern exists. Management will be required to make this evaluation for both annual and interim reporting periods. Management will need to make certain disclosures if it concludes that substantial doubt exists or when it plans to alleviate substantial doubt about the entity's ability to continue as a going concern. The standard is effective for annual periods ending after December 15, 2016 and for interim reporting periods starting in the first quarter of 2017. Early adoption is permitted. The Company does not expect the adoption of the guidance to have a material impact on its consolidated financial statements.

Note 17—Alternative Fuels Excise Tax Credit

From October 1, 2006 through December 31, 2015, the Company was eligible to receive a federal alternative fuels tax credit (“VETC”) of $0.50 per gasoline gallon equivalent of CNG and $0.50 per liquid gallon of LNG that it sold as vehicle fuel. For 2016, the VETC credit is $0.50 per gasoline gallon equivalent of CNG and $0.50 per diesel gallon equivalent of LNG that is sold as a vehicle fuel. Based on the service relationship with its customers, either the Company or its customers claimed the credit. The Company records its VETC credits as revenue in its condensed consolidated statements of operations, as the credits are fully refundable and do not need to offset income tax liabilities to be received. In December 2015, the VETC was extended through December 31, 2016 and made retroactive to January 1, 2015. As a result, VETC revenues for the 2015 calendar year, totaling $30,986, were recognized in December 2015. The Company recognized $6,381 of VETC revenue during the three months ended March 31, 2016.

We serve fleet vehicle operators in a variety of markets, including heavy-duty trucks, airports, refuse, public transit, industrial and institutional energy users and government fleets. We believe these fleet markets will continue to present a growth opportunity for natural gas vehicle fuels for the foreseeable future. As of March 31, 2016, we serve approximately 988 fleet customers operating approximately 44,733 natural gas vehicles, and we own, operate or supply over 570 natural gas fueling stations in 42 states in the U.S. and in British Columbia and Ontario in Canada.

In evaluating our operating performance, our management focuses primarily on: (1) the amount of CNG, LNG and RNG gasoline gallon equivalents delivered (which we define as (i) the volume of gasoline gallon equivalents we sell to our customers, plus (ii) the volume of gasoline gallon equivalents dispensed at facilities we do not own but where we provide O&M services on a per-gallon fee basis, plus (iii) our proportionate share of the gasoline gallon equivalents sold as CNG by our joint venture with Mansfield Ventures, LLC called Mansfield Clean Energy Partners, LLC (“MCEP”), plus (iv) our proportionate share of the gasoline gallon equivalents sold as CNG by our joint venture in Peru (through March 2013 when we sold our interest in the joint venture in Peru), plus (v) our proportionate share (as applicable) of the gasoline gallon equivalents of RNG produced and sold as pipeline quality natural gas by the RNG production facilities we own or operate), (2) our gross margin (which we define as revenue minus cost of sales), and (3) net income (loss) attributable to us. The following tables, which should be read in conjunction with our condensed consolidated financial statements and notes included in this report and our consolidated financial statements and notes contained in our 2015 10-K, presents our key operating data for the years ended December 31, 2013, 2014, and 2015 and for the three months ended March 31, 2015 and 2016: