2. Summary of Significant Accounting Policies

        Cash Equivalents    The Company considers only those investments that are highly liquid and readily convertible to cash with original maturities of three months or less at date of purchase as cash equivalents.

        Restricted Cash    As of March 31, 2011, the Company had maintained $1.3 million as additional security for its line of credit with Wells Fargo. During Fiscal 2012, Wells Fargo released $1.3 million of the restricted cash.

        See Note 11—Revolving Credit Facility, for discussion of the line of credit with Wells Fargo.

        Fair Value of Financial Instruments    The carrying value of certain financial instruments, including cash equivalents, accounts receivable, accounts payable, revolving credit facility and notes payable approximate fair market value based on their short-term nature. See Note 10—Fair Value Measurements, for disclosure regarding the fair value of other financial instruments.

        Accounts Receivable    The Company maintains allowances for doubtful accounts for estimated losses resulting from the inability of customers to make required payments.

        Inventories    The Company values inventories at first in first out ("FIFO") basis and lower of cost or market. The composition of inventory is routinely evaluated to identify slow-moving, excess, obsolete or otherwise impaired inventories. Inventories identified as impaired are evaluated to determine if write-downs are required. Included in the assessment is a review for obsolescence as a result of engineering changes in the Company's products. All inventories expected to be used in more than one year are classified as long-term.

        Depreciation and Amortization    Depreciation and amortization are provided for using the straight-line method over the estimated useful lives of the related assets, ranging from two to ten years. Leasehold improvements are amortized over the lease term or the estimated useful lives of the assets, whichever is shorter. Intangible assets that have finite useful lives are amortized over their estimated useful lives using the straight-line method with the exception of the backlog of 100 kW microturbines ("TA100") acquired from Calnetix Power Solutions, Inc. ("CPS"). Purchased backlog is amortized based on unit sales and presented as a component of cost of goods sold.

        Long-Lived Assets    The Company reviews the recoverability of long-lived assets, including intangible assets with finite lives, whenever events or changes in circumstances indicate that the carrying value of such assets may not be recoverable. If the expected future cash flows from the use of such assets (undiscounted and without interest charges) are less than the carrying value, the Company may be required to record a write-down, which is determined based on the difference between the carrying value of the assets and their estimated fair value. The Company performed an analysis as of March 31, 2013 and determined that no impairment was necessary. Intangible assets include a manufacturing license, trade name, technology, backlog and customer relationships. See Note 5—Intangible Assets.

        Deferred Revenue    Deferred revenue consists of deferred product and service revenue and customer deposits. Deferred revenue will be recognized when earned in accordance with the Company's revenue recognition policy. The Company has the right to retain all or part of customer deposits under certain conditions.

        Revenue    The Company's revenue consists of sales of products, parts, accessories and service, which includes a comprehensive Factory Protection Plan ("FPP"), net of discounts. Capstone's distributors purchase products, parts and FPPs for sale to end users and are also required to provide a variety of additional services, including application engineering, installation, commissioning and post-commissioning repair and maintenance service. The Company's standard terms of sales to distributors and direct end-users include transfer of title, care, custody and control at the point of shipment, payment terms ranging from full payment in advance of shipment to payment in 90 days, no right of return or exchange, and no post-shipment performance obligations by Capstone except for warranties provided on the products and parts sold.

        Revenue from the sale of products, parts and accessories is generally recognized and earned when all of the following criteria are satisfied: (a) persuasive evidence of a sales arrangement exists; (b) price is fixed or determinable; (c) collectability is reasonably assured; and (d) delivery has occurred. Delivery generally occurs when the title and the risks and rewards of ownership have substantially transferred to the customer. Service performed by the Company has consisted primarily of time and materials based contracts. The time and materials contracts are usually related to out-of-warranty units. Service revenue derived from time and materials contracts is recognized as the service is performed. The Company also provides maintenance service contracts to customers of its existing installed base. The maintenance service contracts are agreements to perform certain services to maintain a product for a specified period of time. Service revenue derived from maintenance service contracts is recognized on a straight-line basis over the contract period.

        The Company occasionally enters into agreements that contain multiple elements, such as sale of equipment, installation, engineering and/or service. The Company allocates the total contract value among each element based on a selling price hierarchy as follows, where the selling price is based on (i) vendor specific objective evidence ("VSOE"), (ii) third party evidence ("TPE") or (iii) best estimate of selling price if VSOE or TPE are not available. Revenue is the amount related to each element or recognized in accordance with the revenue recognition policies discussed above.

        Warranty    The Company provides for the estimated costs of warranties at the time revenue is recognized. The specific terms and conditions of those warranties vary depending upon the product sold and geography of sale. The Company's product warranties generally start from the delivery date and continue for up to eighteen months. Factors that affect the Company's warranty obligation include product failure rates, anticipated hours of product operations and costs of repair or replacement in correcting product failures. These factors are estimates that may change based on new information that becomes available each period. Similarly, the Company also accrues the estimated costs to address reliability repairs on products no longer in warranty when, in the Company's judgment, and in accordance with a specific plan developed by the Company, it is prudent to provide such repairs. The Company assesses the adequacy of recorded warranty liabilities quarterly and makes adjustments to the liability as necessary. When the Company has sufficient evidence that product changes are altering the historical failure occurrence rates, the impact of such changes is then taken into account in estimating future warranty liabilities.

        Research and Development ("R&D")    The Company accounts for grant distributions and development funding as offsets to R&D expenses and both are recorded as the related costs are incurred. Total offsets to R&D expenses amounted to $1.7 million, $0.8 million and $0.9 million for the years ended March 31, 2013, 2012 and 2011, respectively.

        Income Taxes    Deferred income tax assets and liabilities are computed for differences between the consolidated financial statement and income tax basis of assets and liabilities. Such deferred income tax asset and liability computations are based on enacted tax laws and rates applicable to periods in which the differences are expected to reverse. Valuation allowances are established, when necessary, to reduce deferred income tax assets to the amounts expected to be realized.

        Contingencies    The Company records an estimated loss from a loss contingency when information available prior to issuance of its financial statements indicates that it is probable that an asset has been impaired or a liability has been incurred at the date of the financial statements and the amount of the loss can be reasonably estimated.

        Risk Concentrations    Financial instruments that potentially subject the Company to concentrations of credit risk consist primarily of cash and cash equivalents and accounts receivable. At March 31, 2013, the majority of our cash balances were held at financial institutions located in California, in accounts that are insured by the Federal Deposit Insurance Corporation. Uninsured balances aggregate to approximately $38.6 million as of March 31, 2013. The Company places its cash and cash equivalents with high credit quality institutions. The Company performs ongoing credit evaluations of its customers and maintains an allowance for potential credit losses.

        Sales to Horizon Power Systems ("Horizon"), one of the Company's domestic distributors, accounted for 27%, 19% and 18% of revenue for the years ended March 31, 2013, 2012 and 2011, respectively. Sales to BPC Engineering ("BPC"), one of the Company's Russian distributors, accounted for 11%, 26% and 23% of revenue for the years ended March 31, 2013, 2012 and 2011, respectively. Additionally, BPC and Regatta Solutions, Inc., one of the Company's domestic distributors, accounted for 35% and 11%, respectively, of net accounts receivable as of March 31, 2013. BPC accounted for 44% of net accounts receivable as of March 31, 2012.

        Accounts receivable, net as of March 31, 2013 and 2012 includes $0.3 million and $0.1 million of other receivables, respectively from the U.S. Department of Energy ("DOE") under grants awarded in 2009 and 2010.

        The Company recorded bad debt expense of $0.3 million, $2.3 million and $0.2 million for the years ended March 31, 2013, 2012 and 2011, respectively.

        Certain components of the Company's products are available from a limited number of suppliers. An interruption in supply could cause a delay in manufacturing, which would affect operating results adversely.

        Estimates and Assumptions    The preparation of financial statements in conformity with accounting principles generally accepted in the United States of America requires management to make certain estimates and assumptions that affect the amounts reported in the financial statements and accompanying notes. Significant estimates include accounting for doubtful accounts, stock-based compensation, inventory write-downs, valuation of long-lived assets including intangible assets with finite lives, product warranties, income taxes and other contingencies. Actual results could differ from those estimates.

        Net Loss Per Common Share    Basic loss per common share is computed using the weighted-average number of common shares outstanding for the period. Diluted loss per share is also computed without consideration to potentially dilutive instruments because the Company incurred losses which would make such instruments antidilutive. Outstanding stock options at March 31, 2013, 2012 and 2011 were 11.8 million, 10.0 million and 10.1 million, respectively. Outstanding restricted stock units at March 31, 2013, 2012 and 2011 were 1.5 million, 1.1 million and 1.5 million, respectively. As of March 31, 2013, 2012 and 2011, the number of warrants excluded from diluted net loss per common share computations was approximately 26.5 million, 26.5 million and 21.7 million, respectively.

        Stock-Based Compensation    Options or stock awards are recorded at their estimated fair value at the measurement date. The Company recognizes compensation cost for options and stock awards that have a graded vesting schedule on a straight-line basis over the requisite service period for the entire award.

        Segment Reporting    The Company is considered to be a single reporting segment. The business activities of this reporting segment are the development, manufacture and sale of turbine generator sets and their related parts and service. Following is the geographic revenue information based on the primary operating location of the Company's customers (in thousands):

        The following table summarizes the Company's revenue by product (in thousands):

        Substantially all of the Company's operating assets are in the United States.