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Summary of Significant Accounting Policies (Policies) | 12 Months Ended
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Dec. 31, 2020
Summary of Significant Accounting Policies |
Principles of Consolidation | Principles of Consolidation ​ The consolidated financial statements include the financial statements of the Company and its wholly-owned subsidiaries. All significant intercompany balances and transactions have been eliminated in consolidation. ​
Leases | Leases ​ The Company is a lessee in noncancelable (1) operating leases, primarily related to sale/leaseback transactions with financial institutions for deployment of the Company’s products at certain customer sites, and (2) finance leases. The Company accounts for leases in accordance with Accounting Standards Codification (ASC) Topic 842, Leases (ASC Topic 842), as amended. ​ The Company determines if an arrangement is or contains a lease at contract inception. The Company recognizes a right of use asset and a lease liability at the lease commencement date. For operating leases, the lease liability is initially measured at the present value of the unpaid lease payments at the lease commencement date. For finance leases, the lease liability is initially measured in the same manner and date as for operating leases and is subsequently measured at amortized cost using the effective interest method. ​ Key estimates and judgments include how the Company determines (1) the discount rate it uses to discount the unpaid lease payments to present value, (2) the lease term and (3) the lease payments. ​
| ● | ASC Topic 842 requires a lessee to discount its unpaid lease payments using the interest rate implicit in the lease or, if that rate cannot be readily determined, its incremental borrowing rate. Generally, the Company cannot determine the interest rate implicit in the lease because it does not have access to the lessor’s estimated residual value or the amount of the lessor’s deferred initial direct costs. Therefore, the Company generally uses its incremental borrowing rate as the discount rate for the lease. The Company’s incremental borrowing rate for a lease is the rate of interest it would have to pay on a collateralized basis to borrow an amount equal to the lease payments under similar terms. Adjustments that considered the Company’s actual borrowing rate, inclusive of securitization, as well as borrowing rates for companies of similar credit quality, were applied in the determination of the incremental borrowing rate.
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| ● | The lease term for all of the Company’s leases includes the noncancelable period of the lease, plus any additional periods covered by either a Company option to extend (or not to terminate) the lease that the Company is reasonably certain to exercise, or an option to extend (or not to terminate) the lease controlled by the lessor.
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| ● | Lease payments included in the measurement of the lease liability comprise fixed payments, and for certain finance leases, the exercise price of a Company option to purchase the underlying asset if the Company is reasonably certain at lease commencement to exercise the option.
​ The right of use asset is initially measured at cost, which comprises the initial amount of the lease liability adjusted for lease payments made at or before the lease commencement date, plus any initial direct costs incurred less any lease incentives received. For operating leases, the right of use asset is subsequently measured throughout the lease term at the carrying amount of the lease liability, plus initial direct costs, plus (minus) any prepaid (accrued) lease payments, less the unamortized balance of lease incentives received. Lease expense for lease payments is recognized on a straight-line basis over the lease term. ​ For finance leases, the right of use asset is subsequently amortized using the straight-line method from the lease commencement date to the earlier of the end of the useful life of the underlying asset or the end of the lease term unless the lease transfers ownership of the underlying asset to the Company or the Company is reasonably certain to exercise an option to purchase the underlying asset. In those cases, the right of use asset is amortized over the useful life of the underlying asset. Amortization of the right of use asset is recognized and presented separately from interest expense on the lease liability. The Company’s leases do not contain variable lease payments. ​ Right of use assets for operating and finance leases are periodically reviewed for impairment losses. The Company uses the long-lived assets impairment guidance in ASC Subtopic 360-10, Property, Plant, and Equipment – Overall, to determine whether an right of use asset is impaired, and if so, the amount of the impairment loss to recognize. ​ The Company monitors for events or changes in circumstances that require a reassessment of its leases. When a reassessment results in the remeasurement of a lease liability, a corresponding adjustment is made to the carrying amount of the corresponding right of use asset. ​ Operating and finance lease right of use assets are presented separately on the Company’s consolidated balance sheets. The current portions of operating and finance lease liabilities are also presented separately within current liabilities and the long-term portions are presented separately within noncurrent liabilities on the consolidated balance sheets. ​ The Company has elected not to recognize right of use assets and lease liabilities for short-term leases that have a lease term of 12 months or less. The Company recognizes the lease payments associated with its short-term leases as an expense on a straight-line basis over the lease term.
Revenue Recognition | Revenue Recognition ​ The Company enters into contracts that may contain one or a combination of fuel cell systems and infrastructure, installation, maintenance, spare parts, fuel delivery and other support services. Contracts containing fuel cell systems and related infrastructure may be sold directly to customers or provided to customers under a PPA, discussed further below. ​ The Company does not include a right of return on its products other than rights related to standard warranty provisions that permit repair or replacement of defective goods. The Company accrues for anticipated standard warranty costs at the same time that revenue is recognized for the related product, or when circumstances indicate that warranty costs will be incurred, as applicable. Any prepaid amounts would only be refunded to the extent services have not been provided or the fuel cell systems or infrastructure have not been delivered. Revenue is measured based on the transaction price specified in a contract with a customer, subject to the allocation of the transaction price to distinct performance obligations as discussed below. The Company recognizes revenue when it satisfies a performance obligation by transferring a product or service to a customer. ​ Promises to the customer are separated into performance obligations, and are accounted for separately if they are (1) capable of being distinct and (2) distinct in the context of the contract. The Company considers a performance obligation to be distinct if the customer can benefit from the good or service either on its own or together with other resources readily available to the customer and the Company’s promise to transfer the goods or service to the customer is separately identifiable from other promises in the contract. The Company allocates revenue to each distinct performance obligation based on relative standalone selling prices. ​ Payment terms for sales of fuel cells, infrastructure and service to customers are typically 30 to 90 days. Sale/leaseback transactions with financial institutions are invoiced and collected upon transaction closing. Service is prepaid upfront in a majority of the arrangements. The Company does not adjust the transaction price for a significant financing component when the performance obligation is expected to be fulfilled within a year. ​ In 2017, in separate transactions, the Company issued to each of Amazon.com NV Investment Holdings LLC and Walmart warrants to purchase shares of the Company’s common stock. The Company presents the provision for common stock warrants within each revenue-related line item on the consolidated statements of operations. This presentation reflects a discount that those common stock warrants represent, and therefore revenue is net of these non-cash charges. The provision of common stock warrants is allocated to the relevant revenue-related line items based upon the expected mix of the revenue for each respective contract. See Note 18, “Warrant Transaction Agreements,’ for more details. ​ Nature of goods and services ​ The following is a description of principal activities from which the Company generates its revenue. ​
| (j) | Sales of Fuel Cell Systems and Related Infrastructure
​ Revenue from sales of fuel cell systems and related infrastructure represents sales of our GenDrive units, GenSure stationary backup power units, as well as hydrogen fueling infrastructure. ​ The Company uses a variety of information sources in determining standalone selling prices for fuel cells systems and related infrastructure. For GenDrive fuel cells, given the nascent nature of the Company’s market, the Company considers several inputs, including prices from a limited number of standalone sales as well as the Company’s negotiations with customers. The Company also considers its costs to produce fuel cells as well as comparable list prices in estimating standalone selling prices. The Company uses applicable observable evidence from similar products in the market to determine standalone selling prices for GenSure stationary backup power units and hydrogen fueling infrastructure. The determination of standalone selling prices of the Company’s performance obligations requires significant judgment, including periodic assessment of pricing approaches and available observable evidence in the market. Once relative standalone selling prices are determined, the Company proportionately allocates the transaction price to each performance obligation within the customer arrangement based upon standalone selling price. The allocated transaction price related to fuel cell systems and spare parts is recognized as revenue at a point in time which usually occurs at shipment (and occasionally upon delivery). Revenue on hydrogen infrastructure installations is generally recognized at the point at which transfer of control passes to the customer, which usually occurs upon customer acceptance of the hydrogen infrastructure. In certain instances, control of hydrogen infrastructure installations transfers to the customer over time, and the related revenue is recognized over time as the performance obligation is satisfied. The Company uses an input method to determine the amount of revenue to recognize during each reporting period when such revenue is recognized over time, based on the costs incurred to satisfy the performance obligation. ​ (ii)Services performed on fuel cell systems and related infrastructure ​ Revenue from services performed on fuel cell systems and related infrastructure represents revenue earned on our service and maintenance contracts and sales of spare parts. The Company uses an adjusted market assessment approach to determine standalone selling prices for services. This approach considers market conditions and constraints, the Company’s market share, pricing strategies and objectives while maximizing the use of available observable inputs obtained from a limited number of historical standalone service renewal prices and negotiations with customers. The transaction price allocated to services as discussed above is generally recognized as revenue over time on a straight-line basis over the expected service period, as customers simultaneously receive and consume the benefits of routine, recurring maintenance performed throughout the contract period. ​ In substantially all of its commercial transactions, the Company sells extended maintenance contracts that generally provide for a five-to-ten-year service period from the date of product installation in exchange for an up-front payment. Services include monitoring, technical support, maintenance and services that provide for 97% to 98% uptime of the fleet. These services are accounted for as a separate performance obligation, and accordingly, revenue generated from these transactions, subject to the proportional allocation of transaction price, is deferred and recognized as revenue over the term of the contract, generally on a straight-line basis. Additionally, the Company may enter into annual service and extended maintenance contracts that are billed monthly. Revenue generated from these transactions is recognized as revenue on a straight-line basis over the term of the contract. Costs are recognized as incurred over the term of the contract. When costs are projected to exceed revenues over the life of the extended maintenance contract, an accrual for loss contracts is recorded. As of December 31, 2020 and 2019, the Company recorded a loss accrual of $24.0 million and $3.7 million respectively (2019 restated). Costs are estimated based upon historical experience and consider the estimated impact of the Company’s cost reduction initiatives. The actual results may differ from these estimates. See “Extended Maintenance Contracts” below. ​ Extended maintenance contracts generally do not contain customer renewal options. Upon expiration, customers may either negotiate a contract extension or switch to purchasing spare parts and maintaining the fuel cell systems on their own. (iii)Power Purchase Agreements ​ Revenue from PPAs primarily represents payments received from customers who make monthly payments to access for the Company’s GenKey solution. ​ Revenue associated with these agreements is recognized on a straight-line basis over the life of the agreements as the customers receive the benefits from the Company’s performance of the services. The customers receive services ratably over the contract term. ​ In conjunction with entering into a PPA with a customer, the Company may enter into transactions with third-party financial institutions in which it receives proceeds from the sale/leaseback transactions of the equipment and the sale of future service revenue. The proceeds from the financial institution are allocated between the sale of equipment and the sale of future service revenue based on the relative standalone selling prices of equipment and service. The proceeds allocated to the sale of future services are recognized as finance obligations. The proceeds allocated to the sale of the equipment are evaluated to determine if the transaction meets the criteria for sale/leaseback accounting. To meet the sale/leaseback criteria, control of the equipment must transfer to the financial institution, which requires among other criteria the leaseback to meet the criteria for an operating lease and the Company must not have a right to repurchase the equipment (unless specific criteria are met). These transactions typically meet the criteria for sale/leaseback accounting and accordingly, the Company recognizes revenue on the sale of the equipment, and separately recognizes the leaseback obligations. ​ The Company recognizes a lease liability for the equipment leaseback obligation based on the present value of the future payments to the financial institutions that are attributed to the equipment leaseback. The discount rate used to determine the lease liability is the Company’s incremental borrowing rate, which is based on an analysis of the interest rates on the Company’s secured borrowings. Adjustments that considered the Company’s actual borrowing rate, inclusive of securitization, as well as borrowing rates for companies of similar credit quality, were applied in the determination of the incremental borrowing rate. The Company also records a right of use asset which is amortized over the term of the leaseback. Rental expense is recognized on a straight-line basis over the life of the leaseback and is included as a cost of PPA revenue on the consolidated statements of operations. ​ Certain of the Company’s transactions with financial institutions do not meet the criteria for sale/leaseback accounting and accordingly, no equipment sale is recognized. All proceeds from these transactions are accounted for as finance obligations. The right of use assets related to these transactions are classified as equipment related to the PPAs and fuel delivered to the customers, net in the consolidated balance sheets. Costs to service the property, depreciation of the assets related to PPAs and fuel delivered to the customers, and other related costs are included in cost of PPA revenue in the consolidated statements of operations. The Company uses its transaction-date incremental borrowing rate as the interest rate for its finance obligations that arise from these transactions. No additional adjustments to the incremental borrowing rate have been deemed necessary for the finance obligations that have resulted from the failed sale/leaseback transactions. ​ In determining whether the sales of fuel cells and other equipment to financial institutions meet the requirements for revenue recognition under sale/leaseback accounting, the Company, as lessee, determines the classification of the lease. The Company estimates certain key inputs to the associated calculations such as: 1) discount rate used to determine the present value of future lease payments, 2) fair value of the fuel cells and equipment, and 3) useful life of the underlying asset(s): ​
| ● | ASC Topic 842 requires a lessee to discount its future lease payments using the interest rate implicit in the lease or, if that rate cannot be readily determined, its incremental borrowing rate. Generally, the Company cannot determine the interest rate implicit in its leases because it does not have access to the lessor’s estimated residual value or the amount of the lessor’s deferred initial direct costs. Therefore, the Company generally uses its incremental borrowing rate to estimate the discount rate for each lease. Adjustments that considered the Company’s actual borrowing rate, inclusive of securitization, as well as borrowing rates for companies of similar credit quality were applied in the determination of the incremental borrowing rate.
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| ● | In order for the lease to be classified as an operating lease, the present value of the future lease payments cannot exceed 90% of the fair value of the leased assets. The Company estimates the fair value of the lease assets using the sales prices.
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| ● | In order for a lease to be classified as an operating lease, the lease term cannot exceed 75% (major part) of the estimated useful life of the leased asset. The average estimated useful life of the fuel cells is 10 years, and the average estimated useful life of the hydrogen infrastructure is 20 years. These estimated useful lives are compared to the term of each lease to determine the appropriate lease classification.
​ (iv)Fuel Delivered to Customers ​ Revenue associated with fuel delivered to customers represents the sale of hydrogen to customers that has been purchased by the Company from a third party or generated on site. The stand-alone selling price is not estimated because it is sold separately and therefore directly observable. ​ The Company purchases hydrogen fuel from suppliers in most cases (and sometimes produces hydrogen onsite) and sells to its customers. Revenue and cost of revenue related to this fuel is recorded as dispensed and is included in the respective “Fuel delivered to customers” lines on the consolidated statements of operations. ​ Contract costs ​ The Company expects that incremental commission fees paid to employees as a result of obtaining sales contracts are recoverable and therefore the Company capitalizes them as contract costs. ​ Capitalized commission fees are amortized on a straight-line basis over the period of time which the transfer of goods or services to which the assets relate occur, typically ranging from 5 to 10 years. Amortization of the capitalized commission fees is included in selling, general and administrative expenses. ​ The Company recognizes the incremental costs of obtaining contracts as an expense when incurred if the amortization period of the assets that the Company otherwise would have recognized is one year or less. These costs are included in selling, general and administrative expenses.
Cash Equivalents | Cash Equivalents ​ For purposes of the consolidated statements of cash flows, the Company considers all highly-liquid debt instruments with original maturities of three months or less to be cash equivalents. At December 31, 2020 and 2019, cash equivalents consist of money market accounts. The Company’s cash and cash equivalents are deposited with financial institutions located in the U.S. and may at times exceed insured limits. ​
Common Stock Warrant Accounting | Common Stock Warrant Accounting ​ The Company accounts for common stock warrants as either derivative liabilities or as equity instruments depending on the specific terms of the respective warrant agreements.
Accounts Receivable | ​ Accounts Receivable ​ Accounts receivable are stated at the amount billed or billable to customers and are ordinarily due between 30 and 60 days after the issuance of the invoice. Receivables are reserved or written off based on individual credit evaluation and specific circumstances of the customer. The allowance for doubtful accounts and related receivable are reduced when the amount is deemed uncollectible. As of December 31, 2020, and 2019, the allowance for doubtful accounts was $172 thousand and $249 thousand, respectively.
Inventory | Inventory ​ Inventories are valued at the lower of cost, determined on a first-in, first-out basis, and net realizable value. All inventory, including spare parts inventory held at service locations, is not relieved until the customer has received the product, at which time the customer obtains control of the goods.
Property, Plant and Equipment | Property, Plant and Equipment ​ Property, plant and equipment are originally recorded at cost or, if acquired as part of business combination, at fair value. Maintenance and repairs are expensed as costs are incurred. Depreciation on plant and equipment, which includes depreciation on the Company’s primary manufacturing facility, which is accounted for as a financing obligation, is calculated on the straight-line method over the estimated useful lives of the assets. The Company records depreciation and amortization over the following estimated useful lives: ​
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Leasehold improvements |  | 5 ‑ 10 years
Software, machinery and equipment |  | 1 ‑ 15 years
​ Gains and losses resulting from the sale of property and equipment are recorded in current operations.
Equipment related to PPAs and Fuel Delivered to Customers | Equipment related to PPAs and Fuel Delivered to Customers ​ Equipment related to PPAs and fuel delivered to customers primarily consists of the assets deployed related to PPAs and sites where we deliver fuel to customers. Equipment is depreciated over its useful life. Depreciation expense is recorded on a straight-line basis and is included in cost of revenue for PPAs or cost of fuel delivered to customers, respectively, in the consolidated statements of operations.
Impairment of Long-Lived Assets and PPA Executory Contract Considerations | ​ Impairment of Long-Lived Assets and PPA Executory Contract Considerations ​ We evaluate long-lived assets on a quarterly basis to identify events or changes in circumstances (“triggering events”) that indicate the carrying value of certain assets may not be recoverable. Long-lived assets that we evaluate include right of use lease assets, equipment deployed to our PPA’s, assets related primarily to our fuel delivery business and other company owned long-lived assets. ​ Upon the occurrence of a triggering event, long-lived assets are evaluated to determine if the carrying amounts are recoverable. The determination of recoverability is made based upon the estimated undiscounted future net cash flows of assets grouped at the lowest level for which there are identifiable cash flows independent of the cash flows of other groups. For operating assets, the Company has generally determined that the lowest level of identifiable cash flows is based on the customer sites. The assets related primarily to our fuel delivery business are considered to be their own asset group. The cash flows are estimated based on the remaining useful life of the primary asset within the asset group. ​ For assets related to our PPA agreements, we consider all underlying cash inflows related to our contract revenues and cash outflows relating to the costs incurred to service the PPA’s. Our cash flow estimates used in the recoverability test, are based upon, among other things, historical results adjusted to reflect our best estimate of future cash flows and operating performance. Development of future cash flows also requires us to make assumptions and to apply judgment, including timing of future expected cash flows, future cost savings initiatives, and determining recovery values. Changes to our key assumptions related to future performance and other economic and market factors could adversely affect the outcome of our recoverability tests and cause more asset groups to be tested for impairment. ​ If the estimated undiscounted future net cash flows for a given asset group are less than the carrying amount of the related asset group, an impairment loss is determined by comparing the estimated fair value with the carrying amount of the asset group. The impairment loss is then allocated to the long-lived assets in the asset group based on the asset’s relative carrying amounts. However, assets are not impaired below their then estimated fair values. Fair value is generally determined through various valuation techniques, including discounted cash flow models, quoted market values and third-party independent appraisals, as well as year-over-year trends in pricing of our new equipment and overall evaluation of our industry and market, as considered necessary. The Company considers these indicators with certain of its own internal indices and metrics in determining fair value in light of the nascent state of the Company’s market and industry. The estimate of fair value represents our best estimates of these factors and is subject to variability. Changes to our key assumptions related to future performance and other economic and market factors could adversely affect our impairment evaluation. ​ The Company has determined that the assets deployed for certain PPA arrangements are not recoverable based on the undiscounted estimated future cash flows of the asset group. However, the estimated fair value of the assets in the asset group equal or exceed the carrying amount of the assets or otherwise limit the amount of impairment that would have been recognized. The Company has identified the primary source of the losses as the maintenance components of the PPA arrangements and the impact of customer warrant non-cash provisions. As the PPA arrangements are considered to be executory contracts and there is no specific accounting guidance that permits loss recognition for these revenue contracts, the Company has not recognized a provision for the expected future losses under these revenue arrangements. The Company expects that it will recognize future losses for these arrangements as it continues its efforts to reduce costs of delivering the maintenance component of these arrangements.
Extended Maintenance Contracts | Extended Maintenance Contracts ​ On a quarterly basis, we evaluate any potential losses related to our extended maintenance contracts for fuel cell systems and related infrastructure that has been sold. We measure loss accruals at the customer contract level. The expected revenues and expenses for these contracts include all applicable expected costs of providing services over the remaining term of the contracts and the related unearned net revenue. A loss is recognized if the sum of expected costs of providing services under the contract exceeds related unearned net revenue and is recorded as a provision for loss contracts related to service in the consolidated statement of operations. A key component of these estimates is the expected future service costs. In estimating the expected future service costs, the Company considers its current service cost level and applies significant judgment related to expected cost saving initiatives. The expected future cost savings will be primarily dependent upon the success of the Company’s initiatives related to increasing stack life, achieving better economies of scale on service labor, and improvements in design and operations of infrastructure. If the expected cost saving initiatives are not realized, this will increase the costs of providing services and could adversely affect our estimated contract loss accrual. ​ The following table shows the roll forward of balances in the accrual for loss contracts, including changes due to the provision (benefit) for loss accrual, releases to service cost of sales and releases due to the provision for warrants (in thousands): ​
​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​
​ | December 31, 2020 | ​ | December 31, 2019 | ​ | December 31, 2018
​ | ​ | ​ | ​ | ​ | (as restated) | ​ | ​ | (as restated)
Beginning Balance | $ | 3,702 | ​ | $ | 5,345 | ​ | $ | —
Provision (benefit) for Loss Accrual | ​ | 35,473 | ​ | ​ | (394) | ​ | ​ | 5,345
Released to Service Cost of Sales | ​ | (2,348) | ​ | ​ | (1,249) | ​ | ​ | —
Released to Provision for Warrants | ​ | (12,814) | ​ | ​ | — | ​ | ​ | —
Ending Balance | $ | 24,013 | ​ | $ | 3,702 | ​ | $ | 5,345
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Goodwill and indefinite-lived intangible asset | Goodwill and indefinite-lived intangible asset ​ Goodwill is an asset representing the future economic benefits arising from other assets acquired in a business combination that are not individually identified and separately recognized. Goodwill is reviewed for impairment at least annually. The indefinite-lived intangible asset represents in-process research and development for cumulative research and development efforts associated with dry stack electrolyzer technology acquired in connection with the Giner ELX, Inc. acquisition. ​ The Company has the option to perform a qualitative assessment to determine whether it is more-likely-than-not that the fair value of a reporting unit is less than its carrying amount. If this is the case, the quantitative goodwill impairment test is required. If it is more-likely-than-not that the fair value of a reporting unit is greater than its carrying amount, the quantitative goodwill impairment test is not required. ​ The indefinite-lived intangible asset is tested for impairment annually, and more frequently when there is a triggering event. Annually, or when there is a triggering event, the Company first performs a qualitative assessment by evaluating all relevant events and circumstances to determine if it is more likely than not that the indefinite-lived intangible asset is impaired; this includes considering any potential effect on significant inputs to determining the fair value of the indefinite-lived intangible asset. When it is more likely than not that the indefinite-lived intangible asset is impaired, then the Company calculates the fair value of the intangible asset and performs a quantitative impairment test. ​ The Company performs an impairment review of goodwill and the indefinite lived intangible asset on an annual basis at December 1, and when a triggering event is determined to have occurred between annual impairment tests. For the years ended December 31, 2020, 2019, and 2018, the Company performed a qualitative assessment of goodwill for its single reporting unit based on multiple factors including market capitalization and determined that it is not more likely than not that the fair value of its reporting unit is less than the carrying amount. For the year ended December 31, 2020, the Company performed a qualitative assessment of its indefinite lived intangible asset and determined that it is not more likely than not that its fair value is less than the carrying amount.
Intangible Assets | Intangible Assets ​ Intangible assets consist of acquired technology, customer relationships and trademarks, and are amortized using a straight-line method over their useful lives of 5–10 years. Additionally, the intangible assets are reviewed for impairment when certain triggering events occur. ​
Fair Value Measurements | Fair Value Measurements ​ The Company records the fair value of assets and liabilities in accordance with ASC 820, Fair Value Measurement (“ASC 820”). ASC 820 defines fair value as the price received to sell an asset or paid to transfer a liability in an orderly transaction between market participants at the measurement date and in the principal or most advantageous market for that asset or liability. The fair value should be calculated based on assumptions that market participants would use in pricing the asset or liability, not on assumptions specific to the entity. ​ In addition to defining fair value, ASC 820 expands the disclosure requirements around fair value and establishes a fair value hierarchy for valuation inputs. The hierarchy prioritizes the inputs into three levels based on the extent to which inputs used in measuring fair value are observable in the market. Each fair value measurement is reported in one of the three levels, which is determined by the lowest level input that is significant to the fair value measurement in its entirety. ​ These levels are: ​
| ● | Level 1 — quoted prices (unadjusted) in active markets for identical assets or liabilities.
| ● | Level 2 — quoted prices for similar assets and liabilities in active markets or inputs that are observable
for the asset or liability, either directly or indirectly through market corroboration, for substantially the full term of the financial instrument.
| ● | Level 3 — unobservable inputs reflecting management’s own assumptions about the inputs used in
pricing the asset or liability at fair value. ​ The following table summarizes the carrying amount and estimated fair value of the Company’s financial instruments at December 31, 2020 and 2019 (in thousands): ​
​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​
​ | ​ | Carrying | ​ | Fair | ​ | Fair Value Measurements
As of December 31, 2020 | ​ | Amount | ​ | Value | ​ | Level 1 | ​ | Level 2 | ​ | Level 3
Contingent consideration | $ | 9,760 | $ | 9,760 | $ | — | $ | — | $ | 9,760
Convertible senior notes | ​ | 85,640 | ​ | 1,272,766 | ​ | — | ​ | 1,272,766 | ​ | —
Long-term debt | ​ | 175,402 | ​ | 175,402 | ​ | — | ​ | — | ​ | 175,402
Finance obligations | ​ | 181,553 | ​ | 181,553 | ​ | — | ​ | — | ​ | 181,553
​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​
​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​
​ | ​ | Carrying | ​ | Fair | ​ | Fair Value Measurements
As of December 31, 2019 | ​ | Amount | ​ | Value | ​ | Level 1 | ​ | Level 2 | ​ | Level 3
Convertible senior notes | $ | 110,431 | $ | 188,775 | $ | — | $ | 135,320 | $ | 53,455
Long-term debt | ​ | 112,169 | ​ | 112,169 | ​ | — | ​ | — | ​ | 112,169
Finance obligations | ​ | 144,089 | ​ | 144,089 | ​ | — | ​ | — | ​ | 144,089
Equity Instruments | Equity Instruments ​ Common stock warrants that meet certain applicable requirements of ASC Subtopic 815-40, Derivatives and Hedging – Contracts in Entity’s Own Equity, and other related guidance, including the ability of the Company to settle the warrants without the issuance of registered shares or the absence of rights of the grantee to require cash settlement, are accounted for as equity instruments. The Company classifies these equity instruments within additional paid-in capital on the consolidated balance sheets. ​ Common stock warrants accounted for as equity instruments represent the warrants issued to Amazon and Walmart as discussed in Note 18, “Warrant Transaction Agreements.” The Company adopted FASB ASU 2019-08, Compensation – Stock Compensation (Topic 718) and Revenue from Contracts with Customers (Topic 606), which requires entities to measure and classify share-based payment awards granted to a customer by applying the guidance under Topic 718, as of January 1, 2019. ​ In order to calculate warrant charges, the Company used the Black-Scholes pricing model, which required key inputs including volatility and risk-free interest rate and certain unobservable inputs for which there is little or no market data, requiring the Company to develop its own assumptions. The Company estimated the fair value of unvested warrants, considered to be probable of vesting, at the time. Based on that estimated fair value, the Company determined warrant charges, which are recorded as a reduction of revenue in the consolidated statement of operations.
Redeemable Preferred Stock | Redeemable Preferred Stock ​ We account for redeemable preferred stock as temporary equity in accordance with applicable accounting guidance in FASB ASC Topic 480, Distinguishing Liabilities from Equity. Dividends on the redeemable preferred stock are accounted for as an increase in the net loss attributable to common stockholders. ​
Income Taxes | Income Taxes ​ Income taxes are accounted for under the asset and liability method. Deferred tax assets and liabilities are recognized for the future tax consequences attributable to differences between the financial statement carrying amounts of existing assets and liabilities and their respective tax basis and operating loss and tax credit carryforwards. Deferred tax assets and liabilities are measured using enacted tax rates expected to apply to taxable income in the years in which those temporary differences are expected to be recovered or settled. The effect on deferred tax assets and liabilities of a change in tax rates is recognized in the period that includes the enactment date. A valuation allowance is recorded to reduce the carrying amounts of deferred tax assets if it is more likely than not that such assets will not be realized. ​ The Company accounts for uncertain tax positions in accordance with FASB ASC No. 740-10-25, Income Taxes-Overall-Recognition. The Company recognizes in its consolidated financial statements the impact of a tax position only if that position is more likely than not to be sustained on audit, based on the technical merits of the position. The Company recognizes interest and penalties on the Interest and other expense, net line in the accompanying consolidated statements of operations.
Foreign Currency Translation | Foreign Currency Translation ​ Foreign currency translation adjustments arising from conversion of the Company’s foreign subsidiary’s financial statements to U.S. dollars for reporting purposes are included in accumulated other comprehensive income in stockholders’ equity on the consolidated balance sheets. Transaction gains and losses resulting from the effect of exchange rate changes on transactions denominated in currencies other than the functional currency of the Company’s operations give rise to realized foreign currency transaction gains and losses, and are included in interest and other income and interest and other expense, respectively, in the consolidated statements of operations. ​
Research and Development. | Research and Development ​ Costs related to research and development activities by the Company are expensed as incurred. Certain research and development expenses have been reclassified for 2018, 2019 and 2020, including interim periods during 2019 and 2020 (see Note 2, “Restatement of Previously Issued Consolidated Financial Statements,” and Note 3 “Unaudited Quarterly Financial data and Restatement of Previously Issued Unaudited Interim Condensed Consolidated Financial Statements).
Stock-Based Compensation | Stock-Based Compensation ​ The Company maintains employee stock-based compensation plans, which are described more fully in Note 20, “Employee Benefit Plans.” ​ Stock-based compensation represents the cost related to stock-based awards granted to employees and directors. The Company measures stock-based compensation cost at grant-date, based on the fair value of the award, and recognizes the cost as expense on a straight-line basis over the option’s requisite service period. ​ The Company estimates the fair value of stock-based awards using a Black-Scholes valuation model. Stock-based compensation expense is recorded in cost of revenue associated with sales of fuel cell systems and related infrastructure, cost of revenue for services performed on fuel cell systems and related infrastructure, research and development expense and selling, general and administrative expenses in the consolidated statements of operations based on the employees’ respective function. ​ The Company records deferred tax assets for awards that result in deductions on the Company’s income tax returns, based upon the amount of compensation cost recognized and the Company's statutory tax rate. Differences between the deferred tax assets recognized for financial reporting purposes and the actual tax deduction reported on the Company's income tax return are recorded in the income statement. No tax benefit or expense for stock-based compensation has been recorded during the years ended December 31, 2020, 2019 and 2018 since the Company remains in a full valuation allowance position.
Convertible Senior Notes | Convertible Senior Notes ​ The Company accounts for its convertible senior notes with separate liability and equity components. The carrying amount of the liability component was initially determined by estimating the fair value of a similar debt instrument that does not have an associated convertible feature. The carrying amount of the equity component representing the conversion option was determined by deducting the estimated fair value of the liability component from the par value of the convertible senior notes, as a whole as of the date of issuance. This difference represents a debt discount that is amortized to interest expense, with a corresponding increase to the carrying amount of the liability component, over the term of the convertible senior notes using the effective interest rate method. The equity component is not remeasured as long as it continues to meet the conditions for equity classification. The Company has allocated issuance costs incurred to the liability and equity components. Issuance costs attributable to the liability component are being amortized to expense over the respective term of the convertible senior notes, and issuance costs attributable to the equity components were netted with the respective equity component in additional paid-in capital.
Use of Estimates | Use of Estimates ​ The consolidated financial statements of the Company have been prepared in conformity with U.S. generally accepted accounting principles, which require management to make estimates and assumptions that affect the reported amounts of assets and liabilities and disclosure of contingent assets and liabilities at the date of the consolidated financial statements and the reported amounts of revenues and expenses during the reporting period. Actual results could differ from those estimates.
Reclassifications | Reclassifications ​ Reclassifications are made, whenever necessary, to prior period financial statements to conform to the current period presentation. ​
Subsequent Events | Subsequent Events ​ The Company evaluates subsequent events at the date of the balance sheet as well as conditions that arise after the balance sheet date but before the consolidated financial statements are issued. The effects of conditions that existed at the balance sheet date are recognized in the consolidated financial statements. Events and conditions arising after the balance sheet date but before the consolidated financial statements are issued are evaluated to determine if disclosure is required to keep the consolidated financial statements from being misleading. To the extent such events and conditions exist, if any, disclosures are made regarding the nature of events and the estimated financial effects for those events and conditions. See Note 23, “Subsequent Events.” ​
Recent Accounting Pronouncements | Recent Accounting Pronouncements ​ Recently Adopted Accounting Pronouncements ​ In June 2016, ASU 2016-13, Financial Instruments – Credit Losses (Topic 326): Measurement of Credit Losses on Financial Instruments, was issued. Also, in April 2019, Accounting Standards Update (ASU) 2019-04, Codification Improvements to Topic 326, Financial Instruments—Credit Losses, Topic 815, Derivatives and Hedging, and Topic 825, Financial Instruments, was issued to make improvements to updates 2016-01, Financial Instruments – Overall (Subtopic 825-10), 2016-13, Financial Instruments – Credit Losses (Topic 326) and 2017-12, Derivatives and Hedging (Topic 815). ASU 2016-13 significantly changes how entities account for credit losses for financial assets and certain other instruments, including trade receivables and contract assets, that are not measured at fair value through net income. The ASU requires a number of changes to the assessment of credit losses, including the utilization of an expected credit loss model, which requires consideration of a broader range of information to estimate expected credit losses over the entire lifetime of the asset, including losses where probability is considered remote. Additionally, the standard requires the estimation of lifetime expected losses for trade receivables and contract assets that are classified as current. The Company adopted these standards effective January 1, 2020 and determined the impact of the standards to be immaterial to the consolidated financial statements. ​ In January 2017, ASU 2017-04, Intangibles – Goodwill and Other (Topic 350), was issued to simplify how an entity is required to test goodwill for impairment by eliminating Step 2 from the goodwill impairment test. Step 2 measures a goodwill impairment loss by comparing the implied fair value of a reporting unit’s goodwill with the carrying amount of that goodwill. The Company adopted this standard effective January 1, 2020 and determined there to be no impact to the consolidated financial statements. ​ Recently Issued and Not Yet Adopted Accounting Pronouncements ​ In August 2020, the FASB issued ASU 2020-06, Debt - Debt with Conversion and Other Options (Subtopic 470-20) and Derivatives and Hedging - Contracts in Entity's Own Equity (Subtopic 815-40): Accounting for Convertible Instruments and Contracts in an Entity's Own Equity (“ASU 2020-06”). This ASU simplifies the complexity associated with applying GAAP for certain financial instruments with characteristics of liabilities and equity. More specifically, the amendments focus on the guidance for convertible instruments and derivative scope exception for contracts in an entity’s own equity. Under ASU 2020-06, the embedded conversion features are no longer separated from the host contract for convertible instruments with conversion features that are not required to be accounted for as derivatives under Topic 815, or that do not result in substantial premiums accounted for as paid-in capital. Consequently, a convertible debt instrument, such as the Company’s 3.75% Convertible Senior Notes, will be accounted for as a single liability measured at its amortized cost, as long as no other features require bifurcation and recognition as derivatives. The new guidance also requires the if-converted method to be applied for all convertible instruments and requires additional disclosures. This guidance is required to be adopted by January 1, 2022, and early adoption is permitted, but no earlier than fiscal years beginning after December 15, 2020. The Company has elected to early adopt this guidance on January 1, 2021 using the modified retrospective method. Under this transition method, the cumulative effect of accounting change removed the impact of recognizing the equity component of the Company’s convertible notes at issuance and the subsequent accounting impact of additional interest expense from debt discount amortization. The cumulative effect of the accounting change upon adoption on January 1, 2021 increased the carrying amount of the convertible notes by $120.7 million, reduced accumulated deficit by $9.5 million and reduced additional paid-in capital by $130.2 million. Future interest expense of the convertible notes will be lower as a result of adoption of this guidance and net loss per share will be computed using the if-converted method for convertible instruments. ​ In March 2020, ASU 2020-04, Reference Rate Reform (Topic 848): Facilitation of the Effects of Reference Rate Reform on Financial Reporting, was issued to provide temporary optional expedients and exceptions to the GAAP guidance on contract modifications and hedge accounting to ease the financial reporting burdens related to the expected market transition from the London Interbank Offered Rate (LIBOR) and other interbank offered rates to alternative reference rates. This update was effective starting March 12, 2020 and the Company may elect to apply the amendments prospectively through December 31, 2022. The adoption of this standard does not have a material impact on the Company’s consolidated financial statements. ​ In March 2020, ASU 2020-03, Codification Improvements to Financial Instruments, was issued to make various codification improvements to financial instruments to make the standards easier to understand and apply by eliminating inconsistencies and providing clarifications. This update will be effective at various dates beginning with date of issuance of this ASU. The adoption of this standard does not have a material impact on the Company’s consolidated financial statements. ​ In December 2019, Accounting Standards Update (ASU) 2019-12, Simplifying the Accounting for Income Taxes, was issued to identify, evaluate, and improve areas of GAAP for which cost and complexity can be reduced while maintaining or improving the usefulness of the information provided to users of financial statements. This update will be effective beginning after December 15, 2020. The adoption of this standard does not have a material impact on the Company’s consolidated financial statements.

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