Plug Power (PLUG) 10-Q 11 May 15 2015 Q1 Quarterly report Financial data

Document_and_Entity_Informatio

Document and Entity Information	3 Months Ended
	Mar. 31, 2015	8-May-15
Document and Entity Information:
Entity Registrant Name	PLUG POWER INC
Document Type	10-Q
Document Period End Date	31-Mar-15
Amendment Flag	FALSE
Entity Central Index Key	1093691
Current Fiscal Year End Date	-19
Entity Common Stock, Shares Outstanding		173,439,521
Entity Filer Category	Large Accelerated Filer
Entity Current Reporting Status	Yes
Document Fiscal Year Focus	2015
Document Fiscal Period Focus	Q1

Consolidated_Balance_Sheets

Consolidated Balance Sheets (USD $)	Mar. 31, 2015	Dec. 31, 2014
Current assets:
Cash and cash equivalents	$131,537,210	$146,205,071
Accounts receivable	7,770,863	16,094,788
Inventory	32,092,915	24,735,601
Prepaid expenses and other current assets	6,422,763	5,709,766
Total current assets	177,823,751	192,745,226
Restricted cash	1,218,181	500,000
Property, plant, and equipment, net	5,195,295	5,311,907
Leased property under capital lease, net	1,807,703	1,936,826
Note receivable	431,489	447,408
Intangible assets, net	881,875	1,490,319
Other assets	1,907,664	1,719,055
Total assets	189,265,958	204,150,741
Current liabilities:
Accounts payable	8,616,761	10,185,085
Accrued expenses	7,051,257	8,749,356
Product warranty reserve	1,227,369	1,311,442
Deferred revenue	2,701,200	3,318,919
Obligations under capital lease	396,061	586,879
Other current liabilities	2,137,736	1,554,960
Total current liabilities	22,130,384	25,706,641
Deferred revenue	6,863,347	6,771,485
Common stock warrant liability	7,649,618	9,418,413
Finance obligation	2,408,294	2,426,028
Other liabilities		392,335
Total liabilities	39,051,643	44,714,902
Redeemable preferred stock
Series C redeemable convertible preferred stock, $0.01 par value per share (aggregate involuntary liquidation preference $16,663,782) 10,431 shares authorized; Issued and outstanding: 5,231 at March 31, 2015 and December 31, 2014	1,152,720	1,152,720
Stockholders' equity:
Common stock, $0.01 par value per share; 450,000,000 shares authorized; Issued (including shares in treasury): 173,793,580 at March 31, 2015 and 173,644,532 at December 31, 2014	1,737,936	1,736,445
Additional paid-in capital	1,098,246,504	1,096,391,668
Accumulated other comprehensive income	897,807	897,807
Accumulated deficit	-949,158,617	-938,080,766
Less common stock in treasury: 378,116 at March 31, 2015 and at December 31, 2014	-2,662,035	-2,662,035
Total stockholders' equity (deficit)	149,061,595	158,283,119
Total liabilities, redeemable preferred stock, and stockholders' equity (deficit)	$189,265,958	$204,150,741

Consolidated_Balance_Sheets_Pa

Consolidated Balance Sheets (Parentheticals) (USD $)	Mar. 31, 2015	Dec. 31, 2014
Consolidated Balance Sheets
Series C redeemable convertible Preferred Stock, par value (in dollars per share)	$0.01	$0.01
Series C redeemable convertible Preferred Stock, shares authorized	10,431
Series C redeemable convertible Preferred Stock, shares issued	5,231	5,231
Series C redeemable convertible Preferred Stock, shares outstanding	5,231	5,231
Series C redeemable convertible Preferred Stock, aggregate involuntary liquidation preference (in dollars)	$16,663,782	$16,663,782
Common Stock, par value (in dollars per share)	$0.01	$0.01
Common Stock, shares authorized	450,000,000	245,000,000
Common Stock, shares issued	173,793,580	173,644,532
Common stock in treasury, shares	378,116	378,116

Consolidated_Statements_of_Ope

Consolidated Statements of Operations (USD $)	3 Months Ended
	Mar. 31, 2015	Mar. 31, 2014
Revenue
Product revenue	$4,067,476	$3,162,327
Service revenue	5,303,063	2,065,715
Research and development contract revenue	45,000	346,399
Total revenue	9,415,539	5,574,441
Cost of product revenue	3,837,935	3,444,964
Cost of service revenue	7,637,863	4,018,382
Cost of research and development contract revenue	51,153	417,917
Research and development expense	2,900,944	1,253,396
Selling, general and administrative expenses	7,140,969	3,252,009
Amortization of intangible assets	-608,444	-565,944
Operating loss	-12,761,769	-7,378,171
Interest and other income	31,176	45,009
Change in fair value of common stock warrant liability	1,768,795	-68,433,468
Interest and other expense	-90,023	-90,469
Net loss attributable to the Company	-11,051,821	-75,857,099
Preferred stock dividends declared	-26,030	-51,909
Net loss attributable to common shareholders	($11,077,851)	($75,909,008)
Loss per share:
Basic and diluted (in dollars per share)	($0.06)	($0.57)
Weighted average number of common shares outstanding (in shares)	173,365,830	133,750,522

Consolidated_Statements_of_Com

Consolidated Statements of Comprehensive Loss (USD $)	3 Months Ended
	Mar. 31, 2015	Mar. 31, 2014
Consolidated Statements of Comprehensive Loss
Net loss attributable to the Company	($11,051,821)	($75,857,099)
Other comprehensive income (loss):
Comprehensive loss	($11,051,821)	($75,857,099)

Consolidated_Statements_of_Sto

Consolidated Statements of Stockholders' Equity (Deficit) (USD $)	3 Months Ended
	Mar. 31, 2015	Mar. 31, 2014	Dec. 31, 2014
Increase (Decrease) in Stockholders' Equity
Balance	$158,283,119
Balance (in shares)	173,644,532
Net loss attributable to the Company	-11,051,821	-75,857,099
Stock based compensation	1,697,130
Stock option exercises	133,167
Balance	149,061,595
Balance (in shares)	173,793,580
Common Stock
Increase (Decrease) in Stockholders' Equity
Balance	1,736,445
Balance (in shares)	173,644,532
Stock based compensation	233
Stock based compensation (in shares)	23,280
Stock dividend	91
Stock dividend (in shares)	9,101
Stock option exercises	1,167
Stock option exercises (in shares)	116,667
Balance	1,737,936
Balance (in shares)	173,793,580
Additional Paid-in-Capital
Increase (Decrease) in Stockholders' Equity
Balance	1,096,391,668
Stock based compensation	1,696,897
Stock dividend	25,939
Stock option exercises	132,000
Balance	1,098,246,504
Accumulated Other Comprehensive Income
Increase (Decrease) in Stockholders' Equity
Balance			897,807
Balance	897,807		897,807
Treasury Stock
Increase (Decrease) in Stockholders' Equity
Balance			-2,662,035
Balance (in shares)			378,116
Balance	-2,662,035		-2,662,035
Balance (in shares)	378,116		378,116
Accumulated Deficit
Increase (Decrease) in Stockholders' Equity
Balance	-938,080,766
Net loss attributable to the Company	-11,051,821
Stock dividend	-26,030
Balance	($949,158,617)

Consolidated_Statements_of_Cas

Consolidated Statements of Cash Flows (USD $)	3 Months Ended
	Mar. 31, 2015	Mar. 31, 2014
Cash Flows From Operating Activities:
Net loss attributable to the Company	($11,051,821)	($75,857,099)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation of property, plant and equipment, and investment in leased property	475,194	457,735
Amortization of intangible assets	608,444	565,944
Stock-based compensation	1,697,130	648,750
Change in fair value of common stock warrant liability	-1,768,795	68,433,468
Changes in operating assets and liabilities that provide (use) cash, net of effects of acquisition:
Accounts receivable	8,323,925	87,084
Inventory	-7,357,314	-1,537,404
Prepaid expenses and other assets	-901,606	-945,646
Note receivable	15,919	15,465
Accounts payable, accrued expenses, product warranty reserve and other liabilities	-3,160,055	-1,115,631
Deferred revenue	-525,857	360,324
Net cash used in operating activities	-13,644,836	-8,887,010
Cash Flows From Investing Activities:
Purchase of property, plant and equipment	-229,459	-286,451
Net cash (used in) provided by investing activities	-229,459	-286,451
Cash Flows From Financing Activities:
Change in restricted cash	-718,181
Proceeds from exercise of warrants		18,311,658
Proceeds from issuance of common stock and warrants		52,400,005
Common stock issuance costs		-3,120,762
Proceeds from exercise of stock options	133,167
Principal payments on obligations under capital lease and finance obligation	-208,552	-187,106
Net cash provided by financing activities	-793,566	67,403,795
Effect of exchange rate changes on cash		-25,206
Increase (decrease) in cash and cash equivalents	-14,667,861	58,230,334
Cash and cash equivalents, beginning of period	146,205,071	5,026,523
Cash and cash equivalents, end of period	131,537,210	63,231,651
Cash paid for interest	$90,594	$115,130

Nature_of_Operations

Nature of Operations	9 Months Ended
	Sep. 30, 2014
Nature Of Operations.
Nature of Operations.
	1.  Nature of Operations
	Description of Business
	Plug Power Inc., or the Company, is a leading provider of alternative energy technology focused on the design, development, commercialization and manufacture of hydrogen fuel cell systems used primarily for the material handling and stationary power market.
	We are focused on proton exchange membrane, or PEM, fuel cell and fuel processing technologies, fuel cell/battery hybrid technologies, and associated hydrogen storage and dispensing infrastructure from which multiple products are available. A fuel cell is an electrochemical device that combines hydrogen and oxygen to produce electricity and heat without combustion. Hydrogen is derived from hydrocarbon fuels such as liquid petroleum gas, or LPG, natural gas, propane, methanol, ethanol, gasoline or biofuels. Hydrogen can also be obtained from the electrolysis of water, or produced on-site at consumer locations through a process known as reformation. Plug Power develops complete hydrogen delivery, storage and refueling solutions for customer locations.
	We sell and continue to develop fuel cell product solutions to replace lead-acid batteries in material handling vehicles and industrial trucks for some of North America’s largest distribution and manufacturing businesses. We are focusing our efforts on material handling applications (forklifts) at multi-shift high volume manufacturing and high throughput distribution sites where our products and services provide a unique combination of productivity, flexibility and environmental benefits. Our current product line includes: GenDrive, our hydrogen fueled PEM fuel cell system providing power to material handling vehicles; GenFuel, our hydrogen fueling delivery system; GenCare, our ongoing maintenance program for both the GenDrive fuel cells and GenFuel products; ReliOn, our stationary fuel cell solution providing scalable, modular PEM fuel cell power to support the backup and grid-support power requirements of the telecommunications, transportation, and utility sectors; and GenKey, our turn-key solution coupling together GenDrive or ReliOn, GenFuel and GenCare, offering complete simplicity to customers transitioning to fuel cell power.
	We sell our products worldwide, with a primary focus on North America, through our direct product sales force, leveraging relationships with original equipment manufacturers, or OEMs, and their dealer networks. We are party to a joint venture based in France with Axane, S.A. (Axane), a subsidiary of Air Liquide, under the name HyPulsion, to develop and sell hydrogen fuel cell systems for the European material handling market.  We sell to businesses and government agencies.
	We were organized in the State of Delaware on June 27, 1997.
	Unless the context indicates otherwise, the terms “Company,” “Plug Power,” “we,” “our” or “us” as used herein refers to Plug Power Inc. and its subsidiaries.
	Liquidity
	Our cash requirements relate primarily to working capital needed to operate and grow our business, including funding operating expenses, growth in inventory to support both shipments of new units and servicing the installed base, funding the growth in our GenKey “turn-key” solution which also includes the installation of our customer’s hydrogen infrastructure as well as delivery of the hydrogen molecule, and continued development and expansion of our products. Our ability to achieve profitability and meet future liquidity needs and capital requirements will depend upon numerous factors, including the timing and quantity of product orders and shipments; attaining positive gross margins; the timing and amount of our operating expenses; the timing and costs of working capital needs; the timing and costs of building a sales base; the ability of our customers to obtain financing to support commercial transactions; the timing and costs of developing marketing and distribution channels; the timing and costs of product service requirements; the timing and costs of hiring and training product staff; the extent to which our products gain market acceptance; the timing and costs of product development and introductions; the extent of our ongoing and new research and development programs; and changes in our strategy or our planned activities. If we are unable to fund our operations without additional external financing and therefore cannot sustain future operations, we may be required to delay, reduce and/or cease our operations and/or seek bankruptcy protection.
	We have experienced and continue to experience negative cash flows from operations and net losses.  The Company incurred net losses attributable to common shareholders of $11.1 million for the three months ended March 31, 2015 and $88.6 million, $62.8 million and $31.9 million for the years ended December 31, 2014, 2013 and 2012, respectively, and has an accumulated deficit of $949.2 million at March 31, 2015.
	Net cash used in operating activities for the three months ended March 31, 2015 was $13.6 million. Additionally, on March 31, 2015, we had cash and cash equivalents of $131.5 million and net working capital of $155.7 million. By comparison, net working capital at December 31, 2014 was $167.0 million.
	During 2014, we received gross proceeds of $176.7 million from three underwritten public offerings.  Net proceeds after underwriting discounts and commissions and other estimated fees and expenses were $165.7 million.  In addition, during 2014 we received $18.3 million from the exercise of previously issued common stock warrants.
	To date, we have funded our operations primarily through public and private offerings of common and preferred stock, a sale-leaseback of our building, and our previous line of credit. The Company believes that its current cash, cash equivalents, cash anticipated to be generated from future sales and, to the extent exercised, cash generated from the exercise of outstanding warrants will provide sufficient liquidity to fund operations for at least the next twelve months. This projection is based on our current expectations regarding product sales, cost structure, cash burn rate and other operating assumptions.

Summary_of_Significant_Account

Summary of Significant Accounting Policies	3 Months Ended
	Mar. 31, 2015
Basis of Presentation
Summary of Significant Accounting Policies
	2. Summary of Significant Accounting Policies
	Principles of Consolidation
	The accompanying unaudited interim 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.
	Interim Financial Statements
	The accompanying unaudited interim consolidated financial statements have been prepared pursuant to the rules and regulations of the Securities and Exchange Commission (SEC). In the opinion of management, all adjustments, which consist solely of normal recurring adjustments, necessary to present fairly, in accordance with U.S. generally accepted accounting principles (GAAP), the financial position, results of operations and cash flows for all periods presented, have been made. The results of operations for the interim periods presented are not necessarily indicative of the results that may be expected for the full year.
	Certain information and footnote disclosures normally included in annual consolidated financial statements prepared in accordance with GAAP have been condensed or omitted. These unaudited interim consolidated financial statements should be read in conjunction with the Company’s audited consolidated financial statements and notes thereto included in the Company’s Annual Report on Form 10-K, filed for the fiscal year ended December 31, 2014.
	The information presented in the accompanying consolidated balance sheet as of December 31, 2014 has been derived from the Company’s December 31, 2014 audited consolidated financial statements.  All other information has been derived from the unaudited interim consolidated financial statements of the Company.
	Cash Equivalents and Restricted Cash
	Cash equivalents consist of money market accounts with an initial term of less than three months. For purposes of the unaudited 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.  The Company’s cash and cash equivalents are deposited with financial institutions located in the U.S. and may at times exceed insured limits.
	The Company has restricted cash of $1.2 million at March 31, 2015 related to balances held in escrow associated with leasing arrangements.
	Revenue Recognition
	The Company recognizes revenue under arrangements for products and services, which may include the sale of products and related services, including revenue from installation, service and maintenance, spare parts, hydrogen fueling services (which may include hydrogen supply as well as hydrogen fueling infrastructure) and leased units. The Company also recognizes revenue under research and development contracts, which are primarily cost reimbursement contracts associated with the development of PEM fuel cell technology.
	Products and Services
	The Company enters into revenue arrangements that may contain a combination of fuel cell systems and equipment, installation, service, maintenance, spare parts, hydrogen fueling and other support services. Revenue arrangements containing fuel cell systems and equipment may be sold, or under a limited number of arrangements, leased to customers. For the above multiple deliverable arrangements, the Company accounts for each separate deliverable as a separate unit of accounting if the delivered item or items have value to the customer on a standalone basis. The Company considers a deliverable to have standalone value if the item is sold separately by us or another entity or if the item could be resold by the customer. The Company allocates revenue to each separate deliverable based on its relative selling price. For a majority of our deliverables, the Company determines relative selling prices using its best estimate of the selling price as vendor-specific objective evidence and third-party evidence is generally not available for the deliverables involved in its revenue arrangements due to a lack of a competitive environment in selling fuel cell technology. When determining estimated selling prices, the Company may consider the cost to produce the deliverable, the anticipated margin on that deliverable, the selling price and profit margin for similar products and services, the Company’s ongoing pricing strategy and policies, the value of any enhancements that have been built into the deliverable and the characteristics of the varying markets in which the deliverable is sold, as applicable. The Company determines estimated selling prices for deliverables in its arrangements based on the specific facts and circumstances of each arrangement and analyzes the estimated selling prices used for its allocation of consideration of each arrangement.
	Once relative selling prices are determined, the Company proportionately allocates the sale consideration to each element of the arrangement. The allocated sales consideration related to fuel cell systems and equipment, spare parts, and hydrogen infrastructure is recognized as revenue at shipment if title and risk of loss have passed to the customer, there is persuasive evidence of an arrangement, the sales price is fixed or determinable, collection of the related receivable is reasonably assured, and customer acceptance criteria, if any, have been successfully demonstrated. The allocated sales consideration related to installation, service, maintenance, and hydrogen molecule delivery is generally recognized as revenue when completed or on a straight-line basis over the term of the contract, as appropriate.
	The Company does not include a right of return on its products other than rights related to warranty provisions that permit repair or replacement of defective goods. The Company accrues for anticipated warranty costs at the same time that revenue is recognized for the related product.
	The Company has also sold extended warranty contracts that generally provide for a five to ten year warranty from the date of product installation. These types of contracts are accounted for as a separate deliverable, and accordingly, revenue generated from these transactions is deferred and recognized in income over the warranty period, generally on a straight-line basis. Additionally, the Company may enter into annual service and maintenance contracts that are billed monthly. Revenue generated from these transactions is recognized in income on a straight-line basis over the term of the contract.
	At March 31, 2015 and December 31, 2014, the Company had unbilled amounts from product and service revenues of approximately $918,000 and $616,000, respectively, which is included in other current assets in the accompanying unaudited consolidated balance sheets.
	Research and Development Contracts
	Contract accounting is used for research and development contract revenue. The Company generally shares in the cost of these programs with cost sharing percentages ranging from 30% to 50% of total project costs. Revenue from time and material contracts is recognized on the basis of labor hours expended plus other reimbursable contract costs incurred during the period. All allowable work performed through the end of each calendar quarter is billed, subject to limitations in the respective contracts. We expect to continue research and development contract work that is directly related to our current product development efforts. At March 31, 2015 and December 31, 2014, the Company had unbilled amounts from research and development contract revenue in the amount of approximately $938,000 and $1,047,000, respectively, which is included in other current assets in the accompanying unaudited consolidated balance sheets. Unbilled amounts are expected to be billed during the following quarter.
	Common Stock Warrant Accounting
	The Company accounts for common stock warrants in accordance with applicable accounting guidance provided in Accounting Standards Codification (ASC) Subtopic 815-40, Derivatives and Hedging — Contracts in Entity’s Own Equity, as either derivative liabilities or as equity instruments depending on the specific terms of the warrant agreement. In compliance with applicable securities law, registered common stock warrants that require the issuance of registered shares upon exercise and do not sufficiently preclude an implied right to cash settlement are accounted for as derivative liabilities. We currently classify these derivative warrant liabilities on the accompanying unaudited consolidated balance sheets as a long-term liability, which is revalued at each balance sheet date subsequent to the initial issuance using the Black-Scholes pricing model. The Black-Scholes pricing model, which is based, in part, upon unobservable inputs for which there is little or no market data, requires the Company to develop its own assumptions. Changes in the fair value of the warrants are reflected in the accompanying unaudited consolidated statements of operations as change in fair value of common stock warrant liability.
	Joint Venture
	On February 29, 2012 we completed the formation of our joint venture with Axane, under the name HyPulsion (the JV). The principal purpose of the JV is to develop and sell hydrogen fuel cell systems for the European material handling market. Axane contributed in exchange for an initial 55% ownership of the JV, subject to certain conditions. We contributed to the JV the right to use our technology, including design and technology know-how on GenDrive systems, in exchange for an initial 45% ownership of the JV. We have not contributed any cash to the JV and we are not obligated to contribute any cash.
	On April 19, 2013, Axane purchased an additional 25% ownership interest in HyPulsion from the Company for a cash purchase price of $3.2 million (Euro 2.5 million). We own 20% and Axane owns 80% of the JV, and we will share in 20% of the profits from the JV. The Company has the right to purchase an additional 60% of the JV from Axane at any time between January 4, 2018 and January 29, 2018 at a formula price. If the Company exercises its purchase right, Axane will have the right, at any time between February 1, 2018 and December 31, 2021, to require the Company to buy the remaining 20% interest at a formula price.
	In addition, the Company and HyPulsion also entered into an engineering service agreement under which, among other things, the Company will provide HyPulsion with engineering and technical services for a new fuel cell assembly line and manufacturing execution system. Under the service agreement, HyPulsion has paid the Company approximately $659,000 (Euro 500,000) in the aggregate for services to be performed by the Company.
	In accordance with the equity method of accounting, the Company will increase its investment in the JV by its share of any earnings, and decrease its investment in the JV by its share of any losses. Losses in excess of the investment are not recognized and must be restored from future profits before the Company’s proportionate share of profits can be recognized. As of March 31, 2015, the Company had a zero basis for its investment in the JV.
	Use of Estimates
	The unaudited interim consolidated financial statements have been prepared in conformity with GAAP, 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 financial statements and the reported amounts of revenues and expenses during the reporting period. Actual results could differ from those estimates.
	Reclassifications
	Reclassifications are made, whenever necessary, to prior period financial statements to conform to the current period presentation.  These reclassifications did not impact the results of operations or net cash flows in the periods presented.
	Recent Accounting Pronouncements
	In February 2015, amended accounting guidance was issued which changes the evaluation of variable interest entities regarding whether they should consolidate limited partnerships and similar entities, or whether fees are paid to a decision maker or service provider, or whether they are held by related parties. This accounting update is effective for reporting periods beginning after December 15, 2015.  We do not expect the adoption of this update to have a significant effect on our consolidated financial statements.
	In January 2015, an accounting update was issued which simplifies the income statement presentation by eliminating the concept of extraordinary items from GAAP.  The concept of separately presenting an extraordinary item after income from continuing operations will no longer be required.  This accounting update is effective for reporting periods beginning after December 31, 2015.  We do not expect this update to have a significant effect on our consolidated financial statements, absent any future transactions that would have qualified for extraordinary item presentation under the prior guidance.
	In August 2014, an accounting update was issued relating to how management assesses conditions and events that could raise substantial doubt about an entity’s ability to continue as a going concern. This accounting update is effective for reporting periods beginning after December 31, 2016. We do not expect the adoption of this update to have a significant effect on our consolidated financial statements.
	In June 2014, an accounting update was issued relating to accounting for share-based payments with a performance target that could be achieved after the requisite service period.  The adoption of this accounting guidance is effective for reporting periods beginning after December 31, 2015. We do not expect the adoption of this update to have a significant effect on our consolidated financial statements.
	In June 2014, an accounting update was issued that replaces the existing revenue recognition framework regarding contracts with customers. In April 2015, the Financial Accounting Standards Board (FASB) proposed a one year delay in the required adoption date from January 1, 2017 to January 1, 2018.  We are evaluating the effect this update will have on our consolidated financial statements and have not yet selected a transition method.

Acquisition_of_ReliOn_Inc

Acquisition of ReliOn Inc	3 Months Ended
	Mar. 31, 2015
Acquisition of ReliOn Inc.
Acquisition of ReliOn Inc.
	3. Acquisition of ReliOn, Inc.
	On April 2, 2014, the Company completed the acquisition of ReliOn, Inc. (“ReliOn”) for an aggregate purchase price of $4,000,000. The Company acquired substantially all of the assets of ReliOn, including patents, technology and other intangible assets, equipment and other tangible assets. ReliOn is a developer of hydrogen fuel cell stack technology based in Spokane, Washington. As consideration, the Company issued 530,504 shares of common stock, and assumed certain specified liabilities of ReliOn. The total purchase price of $4,000,000 is based on the issuance of 530,504 shares of Plug Power common stock at the closing price of the Company’s stock on April 1, 2014 of $7.54.
	The following table summarizes the allocation of the purchase price to the estimated fair value of the net assets acquired:
	Cash and cash equivalents	$	414,000
	Accounts receivable	315,975
	Inventory	5,161,223
	Prepaid expenses and other assets	88,894
	Property and equipment	162,990
	Identifiable intangibles	980,000
	Accounts payable and accrued expenses	(1,682,782		)
	Note payable	(426,044		)
	Total Net Assets Acquired	$	5,014,256
	Gain on bargain purchase	(1,014,256		)
	Acquisition consideration	$	4,000,000
	The fair value of the acquired net assets exceeded the purchase consideration, and therefore a gain on bargain purchase of $1,014,256 was recognized during the year ended December 31, 2014.
	The results of operations of ReliOn are consolidated in the Company’s results of operations beginning on the acquisition date of April 2, 2014. The following unaudited pro forma financial information for the years ended December 31, 2014 and 2013 present the consolidated operations data of the Company as if the ReliOn acquisition had been made on January 1, 2013. The unaudited pro forma financial information is provided for informational purposes only and does not project the Company’s results of operations for any future period.
		Year ended			Year ended
		December 31, 2014			December 31, 2013
	Revenue	$	65,361,494		$	31,190,848
	Net loss attributable to the Company	(88,925,977		)	(69,645,886		)
	Basic and diluted loss per share	$	(0.56	)	$	(0.90	)

Inventory

Inventory	3 Months Ended
	Mar. 31, 2015
Inventory.
Inventory
	4. Inventory
	Inventory as of March 31, 2015 and December 31, 2014 consisted of the following:
		March 31, 2015		December 31, 2014
	Raw materials and supplies	$	22,654,432	$	18,501,386
	Work-in-process	2,092,409		237,268
	Finished goods	7,346,074		5,996,947
		$	32,092,915	$	24,735,601

Redeemable_Preferred_Stock

Redeemable Preferred Stock	3 Months Ended
	Mar. 31, 2015
Redeemable Preferred Stock
Redeemable Preferred Stock
	5.  Redeemable Preferred Stock
	The Company has 5,231 shares of Series C Redeemable Convertible Preferred Stock (the Preferred Stock) outstanding at both March 31, 2015 and December 31, 2014.  The holder of these shares is entitled to designate one director to the Company’s Board of Directors.  The Preferred Stock ranks senior to the Common Stock with respect to rights upon the liquidation, dissolution or winding up of the Company. In the event of any voluntary or involuntary liquidation, dissolution or winding up of the Company, or other deemed liquidation event, as defined in the Securities Purchase Agreement, the holder of the Preferred Stock will be entitled to be paid an amount per share equal to the greater of (i) the original issue price, plus any accrued but unpaid dividends or (ii) the amount per share that would have been payable had all shares of the Preferred Stock been converted to shares of common stock immediately prior to such liquidation event. The Preferred Stock may not be redeemed by the Company until May 8, 2016. After this date, the Preferred Stock is redeemable at the election of the holder of the Preferred Stock or the Company.
	The holder of the Preferred Stock is entitled to receive dividends at a rate of 8% per annum, based on the original issue price of $2,595,400, payable in equal quarterly installments in cash or in shares of Common Stock, at the Company’s option.  The Preferred Stock is convertible into shares of Common Stock with the number of shares of Common Stock issuable upon conversion determined by dividing the original issue price of $2,595,400 by the conversion price in effect at the time the shares are converted. The conversion price of the Preferred Stock as of March 31, 2015 was $0.2343.

Earnings_Per_Share

Earnings Per Share	3 Months Ended
	Mar. 31, 2015
Earnings Per Share.
Earnings Per Share
	6. Earnings Per Share
	Basic earnings per common share are computed by dividing net loss attributable to common shareholders by the weighted average number of common shares outstanding during the reporting period. Diluted earnings per share reflects the potential dilution that could occur if securities or other contracts to issue common stock (such as stock options, unvested restricted stock, common stock warrants, and preferred stock) were exercised or converted into common stock or resulted in the issuance of common stock (net of any assumed repurchases) that then shared in the earnings of the Company, if any. This is computed by dividing net earnings by the combination of dilutive common share equivalents, which is comprised of shares issuable under outstanding warrants, the conversion of preferred stock, and the Company’s share-based compensation plans, and the weighted average number of common shares outstanding during the reporting period. Since the Company is in a net loss position, all common stock equivalents would be considered to be anti-dilutive and are, therefore, not included in the determination of diluted earnings per share. Accordingly, basic and diluted loss per share for the quarters ended March 31, 2015 and 2014 are equal.
	The following table provides the components of the calculations of basic and diluted earnings per share:
			Three Months Ended
			March 31, 2015			March 31, 2014
	Numerator:
	Net loss attributable to common shareholders		$	(11,077,851	)	$	(75,909,008	)
	Denominator:
	Weighted average number of common shares outstanding		173,365,830			133,750,522
	The potential dilutive common shares are summarized as follows:
			At March 31,
			2015		2014
	Stock options outstanding		8,191,928		4,785,485
	Restricted stock outstanding		395,558		650,002
	Common stock warrants (1)		4,219,442		4,250,490
	Preferred stock (2)		5,554,594		11,065,897
	Number of dilutive potential common shares		18,361,522		20,751,874
		-1		In May 2011, the Company issued 7,128,563 warrants as part of an underwritten public offering.  As a result of additional public offerings, and pursuant to the effect of the anti-dilution provisions of these warrants, the number of warrants increased to 22,995,365.  Of these warrants, 219,342 and 250,390 were unexercised as of March 31, 2015 and 2014, respectively.  In February 2013, the Company issued 23,637,500 warrants as part of an underwritten public offering.  Of these warrants, 100 were unexercised as of March 31, 2015 and 2014.  In January 2014, the Company issued 4,000,000 warrants as part of an underwritten public offering.  Of these warrants, all are unexercised as of March 31, 2015 and 2014.  As of March 31, 2015, the remaining warrants have a weighted average exercise price of $3.84.
		-2		The preferred stock amount represents the dilutive potential common shares of the Series C redeemable convertible preferred stock issued on May 16, 2013 based on the conversion price of the preferred stock as of March 31, 2015.  Of the 10,431 preferred shares issued in May 2013, 5,200 had been converted to common stock as of March 31, 2015.

Intangible_Assets

Intangible Assets	3 Months Ended
	Mar. 31, 2015
Intangible Assets.
Intangible Assets
	7. Intangible Assets
	The gross carrying amount and accumulated amortization of the Company’s acquired identifiable intangible assets as of March 31, 2015 and December 31, 2014 are as follows:
		Weighted Average	Gross Carrying		Accumulated
	March 31, 2015	Amortization Period	Amount		Amortization			Total
	Acquired technology	8 years	$	17,696,835	$	(17,107,377	)	$	589,458
	Customer relationships	8 years	1,260,000		(1,015,583		)	244,417
	Trademark	5 years	60,000		(12,000		)	48,000
			$	19,016,835	$	(18,134,960	)	$	881,875
		Weighted Average	Gross Carrying		Accumulated
	December 31, 2014	Amortization Period	Amount		Amortization			Total
	Acquired technology	8 years	$	17,696,835	$	(16,539,683	)	$	1,157,152
	Customer relationships	8 years	1,260,000		(977,833		)	282,167
	Trademark	5 years	60,000		(9,000		)	51,000
			$	19,016,835	$	(17,526,516	)	$	1,490,319

Property_Plant_and_Equipment

Property, Plant and Equipment	9 Months Ended
	Sep. 30, 2014
Property, Plant and Equipment.
Property, Plant and Equipment
	8. Property, Plant and Equipment
	Property, plant and equipment at March 31, 2015 and December 31, 2014 consist of the following:
		March 31,			December 31,
		2015			2014
	Land	$	90,000		$	90,000
	Buildings	15,332,232			15,332,232
	Building improvements	5,031,803			5,031,803
	Software, machinery and equipment	11,596,592			11,396,627
		32,050,627			31,850,662
	Less accumulated depreciation	(26,855,332		)	(26,538,755		)
	Property, plant, and equipment, net	$	5,195,295		$	5,311,907

Capital_Lease

Capital Lease	9 Months Ended
	Sep. 30, 2014
Capital Lease
Capital Lease
	9.  Capital Lease
	Leased property under capital lease at March 31, 2015 and December 31, 2014 consist of the following:
		March 31,			December 31,
		2015			2014
	Leased property under capital lease	$	3,098,921		$	3,098,921
	Less accumulated depreciation	(1,291,218		)	(1,162,095		)
	Leased property under capital lease, net	$	1,807,703		$	1,936,826

Finance_Obligation

Finance Obligation	9 Months Ended
	Sep. 30, 2014
Finance Obligation.
Finance Obligation
	10. Finance Obligation
	In connection with a sale-leaseback transaction related to the Company’s primary facility, the Company entered into an agreement pursuant to which the Company leases from the buyer a portion of the premises sold for a term of 15 years.  Liabilities relating to this agreement of $2.4 million and $68,000 have been recorded as finance obligation and current portion finance obligation (other current liabilities), respectively, in the accompanying unaudited consolidated balance sheet as of March 31, 2015.
	As part of the terms of the transaction, the Company issued a standby letter of credit to the benefit of the landlord/lessor that can be drawn by the beneficiary in the event of default on the lease. The standby letter of credit totals $500,000 and is 100% collateralized by cash balances of the Company, which are included within restricted cash on the accompanying unaudited consolidated balance sheet. The standby letter is renewable for a period of ten years and can be cancelled in part or in full if certain covenants are met and maintained by the Company.

Income_Taxes

Income Taxes	9 Months Ended
	Sep. 30, 2014
Income Taxes.
Income Taxes
	11. Income Taxes
	Under Internal Revenue Code (IRC) Section 382, the use of loss carryforwards may be limited if a change in ownership of a company occurs. If it is determined that, due to transactions involving the Company’s shares owned by its 5 percent or greater shareholders, a change of ownership has occurred under the provisions of IRC Section 382, the Company’s federal and state net operating loss carryforwards could be subject to significant IRC Section 382 limitations.
	Based upon recent IRC Section 382 studies, Section 382 ownership changes occurred that resulted in $728 million of the Company’s $776 million of federal and state net operating loss carryforwards generated through March 31, 2015 being subject to IRC Section 382 limitations. As a result of IRC Section 382 limitations, $715 million of the $728 million net operating loss carryforwards that are limited will expire prior to utilization and are not reflected in the Company’s gross deferred tax asset at March 31, 2015.
	The ownership changes also resulted in net unrealized built in losses per IRS Notice 2003-65 which should result in recognized built in losses during the five year recognition period. These recognized built in losses will translate into unfavorable book to tax add backs in the Company’s 2015 to 2018 U.S. corporate income tax returns of approximately $19.4 million that resulted in a gross deferred tax liability of $7.4 million at March 31, 2015 with a corresponding reduction to the valuation allowance. This gross deferred tax liability will offset certain existing gross deferred tax assets (i.e. capitalized research expense). This has no impact on the Company’s current financial position, results of operations, or cash flows because of the full valuation allowance.
	The Company’s remaining deferred tax assets have been offset by a full valuation allowance because it is more likely than not that the tax benefits of the net operating loss carryforwards and other tax assets may not be realized.
	The Company recognizes accrued interest and penalties related to unrecognized tax benefits as a component of income tax expense. The Company had $0.4 million of interest and penalties accrued at March 31, 2015 and December 31, 2014, respectively.

Fair_Value_Measurements

Fair Value Measurements	9 Months Ended
	Sep. 30, 2014
Fair Value Measurements.
Fair Value Measurements
	12. Fair Value Measurements
	The Company complies with the provisions of FASB ASC Topic No. 820, Fair Value Measurements and Disclosures (ASC 820), in measuring fair value and in disclosing fair value measurements. ASC 820 defines fair value, establishes a framework for measuring fair value and expands disclosures about fair value measurements required under other accounting pronouncements. Fair value, as defined in ASC 820, is an exit price, representing the amount that would be received to sell an asset or paid to transfer a liability in an orderly transaction between market participants. Fair value measurements also reflect the assumptions market participants would use in pricing an asset or liability based on the best information available. Assumptions include the risks inherent in a particular valuation technique (such as a pricing model) and/or the risks inherent in the inputs to the model.
	ASC 820 discusses valuation techniques, such as the market approach (comparable market prices), the income approach (present value of future income or cash flow), and the cost approach (cost to replace the service capacity of an asset or replacement cost) and utilizes a fair value hierarchy that prioritizes the inputs to valuation techniques used to measure fair value into three broad levels. The following is a brief description of those three levels:
	Level 1— Level 1 inputs are unadjusted quoted prices in active markets for assets or liabilities identical to those to be reported at fair value. An active market is a market in which transactions occur for the item to be fair valued with sufficient frequency and volume to provide pricing information on an ongoing basis.
	Level 2 — Level 2 inputs are inputs other than quoted prices included within Level 1. Level 2 inputs are observable either directly or indirectly. These inputs include: (a) Quoted prices for similar assets or liabilities in active markets; (b) Quoted prices for identical or similar assets or liabilities in markets that are not active, such as when there are few transactions for the asset or liability, the prices are not current, price quotations vary substantially over time or in which little information is released publicly; (c) Inputs other than quoted prices that are observable for the asset or liability; and (d) Inputs that are derived principally from or corroborated by observable market data by correlation or other means.
	Level 3 — Level 3 inputs are unobservable inputs for an asset or liability. These inputs should be used to determine fair value only when observable inputs are not available. Unobservable inputs should be developed based on the best information available in the circumstances, which might include internally generated data and assumptions being used to price the asset or liability.
	When determining the fair value measurements for assets or liabilities required or permitted to be recorded at and/or marked to fair value, the Company considers the principal or most advantageous market in which it would transact and considers assumptions that market participants would use when pricing the asset or liability. When possible, the Company looks to active and observable markets to price identical assets. When identical assets are not traded in active markets, the Company looks to market observable data for similar assets. Nevertheless, certain assets are not actively traded in observable markets and the Company must use alternative valuation techniques to derive a fair value measurement.
	The following tables summarize the basis used to measure certain financial instruments at fair value on a recurring basis in the consolidated balance sheets:
	Basis of Fair Value Measurements
					Quoted Prices in Active			Significant		Significant
					Markets for Identical			Other Observable		Other Unobservable
					Items			Inputs		Inputs
	Balance at March 31, 2015	Total			(Level 1)			(Level 2)		(Level 3)
	Common stock warrant liability	$	7,649,618		$	—		$	—	$	7,649,618
					Quoted Prices in Active			Significant		Significant
					Markets for Identical			Other Observable		Other Unobservable
					Items			Inputs		Inputs
	Balance at December 31, 2014	Total			(Level 1)			(Level 2)		(Level 3)
	Common stock warrant liability	$	9,418,413		$	—		$	—	$	9,418,413
	The following summarizes the valuation technique for financial instruments measured and recorded at fair value:
	Common stock warrant liability (Level 3):  For our common stock warrants, fair value is based on the Black-Scholes pricing model which is based, in part, upon unobservable inputs for which there is little or no market data, requiring the Company to develop its own assumptions. The Company used the following assumptions for its common stock warrants:
		At March 31, 2015		At December 31, 2014
	Risk-free interest rate	0.25%-1.27%		0.21%-1.35%
	Volatility	107.98%-129.6%		119.16%-136.62%
	Expected average term	1.17-3.80		1.42-4.04
	There was no expected dividend yield for the warrants granted. If factors change and different assumptions are used, the warrant liability and the change in estimated fair value could be materially different. Generally, as the market price of our common stock increases, the fair value of the warrant increases, and conversely, as the market price of our common stock decreases, the fair value of the warrant decreases. Also, a significant increase in the volatility of the market price of the Company’s common stock, in isolation, would result in a significantly higher fair value measurement; and a significant decrease in volatility would result in a significantly lower fair value measurement.
	The following tables show reconciliations of the beginning and ending balances for assets measured at fair value on a recurring basis using significant unobservable inputs (i.e. Level 3):
		Fair Value
		Measurement Using
		Significant
		Unobservable Inputs
	Common stock warrant liability	Three months ended			Three months ended
		March 31, 2015			March 31, 2014
	Beginning of period - January 1, 2015	$	9,418,413		$	28,829,849
	Change in fair value of common stock warrants	(1,768,795		)	68,433,468
	Issuance of common stock warrants	—			11,773,240
	Exercise of common stock warrants	—			(83,294,149		)
	Fair value of common stock warrant liability at March 31, 2015	$	7,649,618		$	25,742,408

Warranty_Reserves

Warranty Reserves	3 Months Ended
	Mar. 31, 2015
Warranty Reserve
Warranty Reserve
	13.   Warranty Reserve
	The GenDrive contracts we enter into generally provide a one to two year standard product warranty to customers from date of installation, and the ReliOn contracts we enter into generally provide a two to five year product warranty. The Company currently estimates the costs of satisfying warranty claims based on an analysis of past experience and provides for future claims in the period the revenue is recognized.  Factors that affect the warranty liability include the number of installed units, estimated material costs, estimated travel, and labor costs.
	The following table summarizes standard product warranty activity recorded during the three months ended March 31, 2015 and 2014:
		2015			2014
	Beginning balance - January 1	$	1,311,442		$	1,608,131
	Additions for current period deliveries	111,107			227,431
	Reductions for payments made	(195,180		)	(357,391		)
	Ending balance - March 31	$	1,227,369		$	1,478,171

Commitment_and_Contingencies

Commitment and Contingencies	9 Months Ended
	Sep. 30, 2014
Commitments and Contingencies.
Commitments and Contingencies
	14. Commitments and Contingencies
	Litigation
	Legal matters are defended and handled in the ordinary course of business.  We have established accruals for matters for which management considers a loss to be probable and reasonably estimable. It is the opinion of management that facts known at the present time do not indicate that such litigation, after taking into account insurance coverage and the aforementioned accruals, will have a material adverse impact on our results of operations, financial position, or cash flows.
	Concentrations of credit risk
	Concentrations of credit risk with respect to receivables exist due to the limited number of select customers that the Company has initial commercial sales arrangements with and government agencies. To mitigate credit risk, the Company performs appropriate evaluation of a prospective customer’s financial condition.
	At March 31, 2015, four customers comprise approximately 62.2% of the total accounts receivable balance, with each customer individually representing 30.8%, 14.4%, 10.3% and 6.7% of total accounts receivable, respectively.  At December 31, 2014, four customers comprise approximately 69.9% of the total accounts receivable balance, with each customer individually representing 30.2%, 16.0%, 13.4% and 10.3% of total accounts receivable, respectively.
	For the three months ended March 31, 2015, contracts with one customer comprised 63.5% of total consolidated revenues.  For the three months ended March 31, 2014, contracts with two customers comprised 31.6% of total consolidated revenues, with each customer individually representing 21.1% and 10.5% of total consolidated revenues, respectively.
	Letter of Credit
	In September 2011, the Company signed a letter of credit with SVB in the amount of $525,000. The standby letter of credit is required by the agreement negotiated between Air Products and Chemicals, Inc., or Air Products, and us to supply hydrogen infrastructure and hydrogen to Central Grocers at their distribution center. There are no collateral requirements associated with this letter of credit.

Summary_of_Significant_Account1

Summary of Significant Accounting Policies (Policies)	3 Months Ended
	Mar. 31, 2015
Summary of Significant Accounting Policies
Principles of Consolidation
	Principles of Consolidation
	The accompanying unaudited interim 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.
Interim Financial Statements
	Interim Financial Statements
	The accompanying unaudited interim consolidated financial statements have been prepared pursuant to the rules and regulations of the Securities and Exchange Commission (SEC). In the opinion of management, all adjustments, which consist solely of normal recurring adjustments, necessary to present fairly, in accordance with U.S. generally accepted accounting principles (GAAP), the financial position, results of operations and cash flows for all periods presented, have been made. The results of operations for the interim periods presented are not necessarily indicative of the results that may be expected for the full year.
	Certain information and footnote disclosures normally included in annual consolidated financial statements prepared in accordance with GAAP have been condensed or omitted. These unaudited interim consolidated financial statements should be read in conjunction with the Company’s audited consolidated financial statements and notes thereto included in the Company’s Annual Report on Form 10-K, filed for the fiscal year ended December 31, 2014.
	The information presented in the accompanying consolidated balance sheet as of December 31, 2014 has been derived from the Company’s December 31, 2014 audited consolidated financial statements.  All other information has been derived from the unaudited interim consolidated financial statements of the Company.
Cash Equivalents and Restricted Cash
	Cash Equivalents and Restricted Cash
	Cash equivalents consist of money market accounts with an initial term of less than three months. For purposes of the unaudited 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.  The Company’s cash and cash equivalents are deposited with financial institutions located in the U.S. and may at times exceed insured limits.
	The Company has restricted cash of $1.2 million at March 31, 2015 related to balances held in escrow associated with leasing arrangements.
Revenue Recognition
	Revenue Recognition
	The Company recognizes revenue under arrangements for products and services, which may include the sale of products and related services, including revenue from installation, service and maintenance, spare parts, hydrogen fueling services (which may include hydrogen supply as well as hydrogen fueling infrastructure) and leased units. The Company also recognizes revenue under research and development contracts, which are primarily cost reimbursement contracts associated with the development of PEM fuel cell technology.
	Products and Services
	The Company enters into revenue arrangements that may contain a combination of fuel cell systems and equipment, installation, service, maintenance, spare parts, hydrogen fueling and other support services. Revenue arrangements containing fuel cell systems and equipment may be sold, or under a limited number of arrangements, leased to customers. For the above multiple deliverable arrangements, the Company accounts for each separate deliverable as a separate unit of accounting if the delivered item or items have value to the customer on a standalone basis. The Company considers a deliverable to have standalone value if the item is sold separately by us or another entity or if the item could be resold by the customer. The Company allocates revenue to each separate deliverable based on its relative selling price. For a majority of our deliverables, the Company determines relative selling prices using its best estimate of the selling price as vendor-specific objective evidence and third-party evidence is generally not available for the deliverables involved in its revenue arrangements due to a lack of a competitive environment in selling fuel cell technology. When determining estimated selling prices, the Company may consider the cost to produce the deliverable, the anticipated margin on that deliverable, the selling price and profit margin for similar products and services, the Company’s ongoing pricing strategy and policies, the value of any enhancements that have been built into the deliverable and the characteristics of the varying markets in which the deliverable is sold, as applicable. The Company determines estimated selling prices for deliverables in its arrangements based on the specific facts and circumstances of each arrangement and analyzes the estimated selling prices used for its allocation of consideration of each arrangement.
	Once relative selling prices are determined, the Company proportionately allocates the sale consideration to each element of the arrangement. The allocated sales consideration related to fuel cell systems and equipment, spare parts, and hydrogen infrastructure is recognized as revenue at shipment if title and risk of loss have passed to the customer, there is persuasive evidence of an arrangement, the sales price is fixed or determinable, collection of the related receivable is reasonably assured, and customer acceptance criteria, if any, have been successfully demonstrated. The allocated sales consideration related to installation, service, maintenance, and hydrogen molecule delivery is generally recognized as revenue when completed or on a straight-line basis over the term of the contract, as appropriate.
	The Company does not include a right of return on its products other than rights related to warranty provisions that permit repair or replacement of defective goods. The Company accrues for anticipated warranty costs at the same time that revenue is recognized for the related product.
	The Company has also sold extended warranty contracts that generally provide for a five to ten year warranty from the date of product installation. These types of contracts are accounted for as a separate deliverable, and accordingly, revenue generated from these transactions is deferred and recognized in income over the warranty period, generally on a straight-line basis. Additionally, the Company may enter into annual service and maintenance contracts that are billed monthly. Revenue generated from these transactions is recognized in income on a straight-line basis over the term of the contract.
	At March 31, 2015 and December 31, 2014, the Company had unbilled amounts from product and service revenues of approximately $918,000 and $616,000, respectively, which is included in other current assets in the accompanying unaudited consolidated balance sheets.
	Research and Development Contracts
	Contract accounting is used for research and development contract revenue. The Company generally shares in the cost of these programs with cost sharing percentages ranging from 30% to 50% of total project costs. Revenue from time and material contracts is recognized on the basis of labor hours expended plus other reimbursable contract costs incurred during the period. All allowable work performed through the end of each calendar quarter is billed, subject to limitations in the respective contracts. We expect to continue research and development contract work that is directly related to our current product development efforts. At March 31, 2015 and December 31, 2014, the Company had unbilled amounts from research and development contract revenue in the amount of approximately $938,000 and $1,047,000, respectively, which is included in other current assets in the accompanying unaudited consolidated balance sheets. Unbilled amounts are expected to be billed during the following quarter.
Common Stock Warrant Accounting
	Common Stock Warrant Accounting
	The Company accounts for common stock warrants in accordance with applicable accounting guidance provided in Accounting Standards Codification (ASC) Subtopic 815-40, Derivatives and Hedging — Contracts in Entity’s Own Equity, as either derivative liabilities or as equity instruments depending on the specific terms of the warrant agreement. In compliance with applicable securities law, registered common stock warrants that require the issuance of registered shares upon exercise and do not sufficiently preclude an implied right to cash settlement are accounted for as derivative liabilities. We currently classify these derivative warrant liabilities on the accompanying unaudited consolidated balance sheets as a long-term liability, which is revalued at each balance sheet date subsequent to the initial issuance using the Black-Scholes pricing model. The Black-Scholes pricing model, which is based, in part, upon unobservable inputs for which there is little or no market data, requires the Company to develop its own assumptions. Changes in the fair value of the warrants are reflected in the accompanying unaudited consolidated statements of operations as change in fair value of common stock warrant liability.
Joint Venture
	Joint Venture
	On February 29, 2012 we completed the formation of our joint venture with Axane, under the name HyPulsion (the JV). The principal purpose of the JV is to develop and sell hydrogen fuel cell systems for the European material handling market. Axane contributed in exchange for an initial 55% ownership of the JV, subject to certain conditions. We contributed to the JV the right to use our technology, including design and technology know-how on GenDrive systems, in exchange for an initial 45% ownership of the JV. We have not contributed any cash to the JV and we are not obligated to contribute any cash.
	On April 19, 2013, Axane purchased an additional 25% ownership interest in HyPulsion from the Company for a cash purchase price of $3.2 million (Euro 2.5 million). We own 20% and Axane owns 80% of the JV, and we will share in 20% of the profits from the JV. The Company has the right to purchase an additional 60% of the JV from Axane at any time between January 4, 2018 and January 29, 2018 at a formula price. If the Company exercises its purchase right, Axane will have the right, at any time between February 1, 2018 and December 31, 2021, to require the Company to buy the remaining 20% interest at a formula price.
	In addition, the Company and HyPulsion also entered into an engineering service agreement under which, among other things, the Company will provide HyPulsion with engineering and technical services for a new fuel cell assembly line and manufacturing execution system. Under the service agreement, HyPulsion has paid the Company approximately $659,000 (Euro 500,000) in the aggregate for services to be performed by the Company.
	In accordance with the equity method of accounting, the Company will increase its investment in the JV by its share of any earnings, and decrease its investment in the JV by its share of any losses. Losses in excess of the investment are not recognized and must be restored from future profits before the Company’s proportionate share of profits can be recognized. As of March 31, 2015, the Company had a zero basis for its investment in the JV.
Use of Estimates
	Use of Estimates
	The unaudited interim consolidated financial statements have been prepared in conformity with GAAP, 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 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.  These reclassifications did not impact the results of operations or net cash flows in the periods presented.
Recent Accounting Pronouncements
	Recent Accounting Pronouncements
	In February 2015, amended accounting guidance was issued which changes the evaluation of variable interest entities regarding whether they should consolidate limited partnerships and similar entities, or whether fees are paid to a decision maker or service provider, or whether they are held by related parties. This accounting update is effective for reporting periods beginning after December 15, 2015.  We do not expect the adoption of this update to have a significant effect on our consolidated financial statements.
	In January 2015, an accounting update was issued which simplifies the income statement presentation by eliminating the concept of extraordinary items from GAAP.  The concept of separately presenting an extraordinary item after income from continuing operations will no longer be required.  This accounting update is effective for reporting periods beginning after December 31, 2015.  We do not expect this update to have a significant effect on our consolidated financial statements, absent any future transactions that would have qualified for extraordinary item presentation under the prior guidance.
	In August 2014, an accounting update was issued relating to how management assesses conditions and events that could raise substantial doubt about an entity’s ability to continue as a going concern. This accounting update is effective for reporting periods beginning after December 31, 2016. We do not expect the adoption of this update to have a significant effect on our consolidated financial statements.
	In June 2014, an accounting update was issued relating to accounting for share-based payments with a performance target that could be achieved after the requisite service period.  The adoption of this accounting guidance is effective for reporting periods beginning after December 31, 2015. We do not expect the adoption of this update to have a significant effect on our consolidated financial statements.
	In June 2014, an accounting update was issued that replaces the existing revenue recognition framework regarding contracts with customers. In April 2015, the Financial Accounting Standards Board (FASB) proposed a one year delay in the required adoption date from January 1, 2017 to January 1, 2018.  We are evaluating the effect this update will have on our consolidated financial statements and have not yet selected a transition method.

Acquisition_of_ReliOn_Inc_Tabl

Acquisition of ReliOn Inc (Tables)	3 Months Ended
	Mar. 31, 2015
Acquisition of ReliOn Inc.
Summary of allocation of the purchase price to the estimated fair value of the net assets acquired
	Cash and cash equivalents	$	414,000
	Accounts receivable	315,975
	Inventory	5,161,223
	Prepaid expenses and other assets	88,894
	Property and equipment	162,990
	Identifiable intangibles	980,000
	Accounts payable and accrued expenses	(1,682,782		)
	Note payable	(426,044		)
	Total Net Assets Acquired	$	5,014,256
	Gain on bargain purchase	(1,014,256		)
	Acquisition consideration	$	4,000,000
Schedule of unaudited pro forma financial information
		Year ended			Year ended
		December 31, 2014			December 31, 2013
	Revenue	$	65,361,494		$	31,190,848
	Net loss attributable to the Company	(88,925,977		)	(69,645,886		)
	Basic and diluted loss per share	$	(0.56	)	$	(0.90	)

Inventory_Tables

Inventory (Tables)	3 Months Ended
	Mar. 31, 2015
Inventory.
Schedule of Inventory
		March 31, 2015		December 31, 2014
	Raw materials and supplies	$	22,654,432	$	18,501,386
	Work-in-process	2,092,409		237,268
	Finished goods	7,346,074		5,996,947
		$	32,092,915	$	24,735,601

Earnings_Per_Share_Tables

Earnings Per Share (Tables)	3 Months Ended
	Mar. 31, 2015
Earnings Per Share.
Schedule of components of the calculations of basic and diluted earnings per share:
			Three Months Ended
			March 31, 2015			March 31, 2014
	Numerator:
	Net loss attributable to common shareholders		$	(11,077,851	)	$	(75,909,008	)
	Denominator:
	Weighted average number of common shares outstanding		173,365,830			133,750,522
Schedule of potential dilutive common shares
			At March 31,
			2015		2014
	Stock options outstanding		8,191,928		4,785,485
	Restricted stock outstanding		395,558		650,002
	Common stock warrants (1)		4,219,442		4,250,490
	Preferred stock (2)		5,554,594		11,065,897
	Number of dilutive potential common shares		18,361,522		20,751,874
		-1		In May 2011, the Company issued 7,128,563 warrants as part of an underwritten public offering.  As a result of additional public offerings, and pursuant to the effect of the anti-dilution provisions of these warrants, the number of warrants increased to 22,995,365.  Of these warrants, 219,342 and 250,390 were unexercised as of March 31, 2015 and 2014, respectively.  In February 2013, the Company issued 23,637,500 warrants as part of an underwritten public offering.  Of these warrants, 100 were unexercised as of March 31, 2015 and 2014.  In January 2014, the Company issued 4,000,000 warrants as part of an underwritten public offering.  Of these warrants, all are unexercised as of March 31, 2015 and 2014.  As of March 31, 2015, the remaining warrants have a weighted average exercise price of $3.84.
		-2		The preferred stock amount represents the dilutive potential common shares of the Series C redeemable convertible preferred stock issued on May 16, 2013 based on the conversion price of the preferred stock as of March 31, 2015.  Of the 10,431 preferred shares issued in May 2013, 5,200 had been converted to common stock as of March 31, 2015.

Intangible_Assets_Tables

Intangible Assets (Tables)	3 Months Ended
	Mar. 31, 2015
Intangible Assets.
Schedule of Intangible assets
		Weighted Average	Gross Carrying		Accumulated
	March 31, 2015	Amortization Period	Amount		Amortization			Total
	Acquired technology	8 years	$	17,696,835	$	(17,107,377	)	$	589,458
	Customer relationships	8 years	1,260,000		(1,015,583		)	244,417
	Trademark	5 years	60,000		(12,000		)	48,000
			$	19,016,835	$	(18,134,960	)	$	881,875
		Weighted Average	Gross Carrying		Accumulated
	December 31, 2014	Amortization Period	Amount		Amortization			Total
	Acquired technology	8 years	$	17,696,835	$	(16,539,683	)	$	1,157,152
	Customer relationships	8 years	1,260,000		(977,833		)	282,167
	Trademark	5 years	60,000		(9,000		)	51,000
			$	19,016,835	$	(17,526,516	)	$	1,490,319

Property_Plant_and_Equipment_T

Property, Plant and Equipment (Tables)	3 Months Ended
	Mar. 31, 2015
Property, Plant and Equipment.
Schedule of Property plant and equipment
		March 31,			December 31,
		2015			2014
	Land	$	90,000		$	90,000
	Buildings	15,332,232			15,332,232
	Building improvements	5,031,803			5,031,803
	Software, machinery and equipment	11,596,592			11,396,627
		32,050,627			31,850,662
	Less accumulated depreciation	(26,855,332		)	(26,538,755		)
	Property, plant, and equipment, net	$	5,195,295		$	5,311,907

Capital_Lease_Tables

Capital Lease (Tables)	3 Months Ended
	Mar. 31, 2015
Capital Lease
Schedule of Capital Leased Assets
		March 31,			December 31,
		2015			2014
	Leased property under capital lease	$	3,098,921		$	3,098,921
	Less accumulated depreciation	(1,291,218		)	(1,162,095		)
	Leased property under capital lease, net	$	1,807,703		$	1,936,826

Fair_Value_Measurments_Tables

Fair Value Measurments (Tables)	3 Months Ended
	Mar. 31, 2015
Fair Value Measurements.
Schedule of Fair Value, Assets and Liabilities Measured on Recurring Basis
	Basis of Fair Value Measurements
					Quoted Prices in Active			Significant		Significant
					Markets for Identical			Other Observable		Other Unobservable
					Items			Inputs		Inputs
	Balance at March 31, 2015	Total			(Level 1)			(Level 2)		(Level 3)
	Common stock warrant liability	$	7,649,618		$	—		$	—	$	7,649,618
					Quoted Prices in Active			Significant		Significant
					Markets for Identical			Other Observable		Other Unobservable
					Items			Inputs		Inputs
	Balance at December 31, 2014	Total			(Level 1)			(Level 2)		(Level 3)
	Common stock warrant liability	$	9,418,413		$	—		$	—	$	9,418,413
Assumptions used to calculate common stock warrants
		At March 31, 2015		At December 31, 2014
	Risk-free interest rate	0.25%-1.27%		0.21%-1.35%
	Volatility	107.98%-129.6%		119.16%-136.62%
	Expected average term	1.17-3.80		1.42-4.04
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation
		Fair Value
		Measurement Using
		Significant
		Unobservable Inputs
	Common stock warrant liability	Three months ended			Three months ended
		March 31, 2015			March 31, 2014
	Beginning of period - January 1, 2015	$	9,418,413		$	28,829,849
	Change in fair value of common stock warrants	(1,768,795		)	68,433,468
	Issuance of common stock warrants	—			11,773,240
	Exercise of common stock warrants	—			(83,294,149		)
	Fair value of common stock warrant liability at March 31, 2015	$	7,649,618		$	25,742,408

Warranty_Reserves_Tables

Warranty Reserves (Tables)	3 Months Ended
	Mar. 31, 2015
Warranty Reserve
Schedule of Product Warranty
		2015			2014
	Beginning balance - January 1	$	1,311,442		$	1,608,131
	Additions for current period deliveries	111,107			227,431
	Reductions for payments made	(195,180		)	(357,391		)
	Ending balance - March 31	$	1,227,369		$	1,478,171

Nature_of_Operations_Details

Nature of Operations (Details) (USD $)	3 Months Ended		12 Months Ended			0 Months Ended
	Mar. 31, 2015	Mar. 31, 2014	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012	Apr. 02, 2014	Sep. 30, 2014
Description of Business
Net loss attributable to common shareholders	$11,077,851	$75,909,008	$88,600,000	$62,800,000	$31,900,000
Accumulated deficit	949,158,617		938,080,766
Net cash used in operating activities	13,644,836	8,887,010
Cash and cash equivalents	131,537,210	63,231,651	146,205,071	5,026,523
Net working capital				$167,000,000			$155,700,000
ReliOn
Description of Business
Number of shares of common stock issued						530,504
Share price (in dollars per share)						$7.54

Nature_of_Operations_Details_2

Nature of Operations (Details 2) (USD $)	3 Months Ended		12 Months Ended
	Mar. 31, 2015	Mar. 31, 2014	Dec. 31, 2014
Nature of Operation.
Net proceeds from public offering			$165,700,000
Gross proceeds from shares of common stock sold in an underwritten public offering			176,700,000
Net proceeds from shares of common stock sold in an underwritten public offering		$52,400,005	$18,300,000
Minimum period for which we believe that our current cash, cash equivalents, cash generated from future sales, and cash generated from the exercise of outstanding warrants will provide sufficient liquidity to fund operations	12 months

Summary_of_Siginificant_Accoun

Summary of Siginificant Accounting Policies (Details)	3 Months Ended		3 Months Ended		3 Months Ended		0 Months Ended		3 Months Ended
	Mar. 31, 2015	Dec. 31, 2014	Mar. 31, 2015	Feb. 29, 2012	Mar. 31, 2015	Mar. 31, 2015	Apr. 19, 2013	Apr. 19, 2013	Mar. 31, 2015	Apr. 19, 2013	Feb. 29, 2012
	USD ($)	USD ($)	HyPulsion	HyPulsion	Minimum	Maximum	Axane, S.A.	Axane, S.A.	Axane, S.A.	Axane, S.A.	Axane, S.A.
							HyPulsion	HyPulsion	HyPulsion	HyPulsion	HyPulsion
							USD ($)	EUR (€)
Basis of Presentation
Restricted Cash and Cash Equivalents	$1,218,181	$500,000
Minimum term of extended warranty contracts sold	5 years
Maximum term of extended warranty contracts sold	10 years
Unbilled amounts from product and service revenues	918,000	616,000
Unbilled amounts	938,000	1,047,000
Joint Venture
Ownership interest percentage			20.00%	45.00%					80.00%		55.00%
Additional ownership interest purchased by counterparty from the Company										25.00%
Cash purchase price							$3,200,000	€ 2,500,000
Percentage of share in profits of joint venture			20.00%
Additional ownership interest that can be purchased by entity from counterparty at any time between January 4, 2018 and January 29, 2018 at a formula price									60.00%
Remaining ownership interest to be acquired by Company upon exercise of its purchase right									20
Research and Development
Cost Sharing Percentages of research and development contracts					30.00%	50.00%

Summary_of_Siginificant_Accoun1

Summary of Siginificant Accounting Policies (Details 2) (HyPulsion)	3 Months Ended
	Mar. 31, 2015	Apr. 19, 2013	Feb. 29, 2012
Joint Venture
Ownership interest percentage	20.00%		45.00%
Percentage of share in profits of joint venture	20.00%
Axane, S.A.
Joint Venture
Ownership interest percentage	80.00%		55.00%
Additional ownership interest purchased by counterparty from the Company		25.00%
Additional ownership interest that can be purchased by entity from counterparty at any time between January 4, 2018 and January 29, 2018 at a formula price	60.00%

Acquisition_of_ReliOn_Inc_Deta

Acquisition of ReliOn Inc (Details) (USD $)	3 Months Ended	12 Months Ended		0 Months Ended
	Mar. 31, 2014	Dec. 31, 2014	Dec. 31, 2013	Apr. 02, 2014
Preliminary allocation of the purchase price to the estimated fair value of the net assets acquired
Gain on bargain purchase		($1,014,256)
Unaudited pro forma financial information
Revenue	65,361,494		31,190,848
Net loss attributable to the Company	-88,925,977		-69,645,886
Basic and diluted loss per share (in dollars per share)	($0.56)		($0.90)
ReliOn
Description of Business
Purchase price		4,000,000		4,000,000
Number of shares of common stock issued				530,504
Closing price of the company's stock				$7.54
Preliminary allocation of the purchase price to the estimated fair value of the net assets acquired
Cash and cash equivalents		414,000
Accounts receivable, net		315,975
Inventory		5,161,223
Prepaid expenses and other assets		88,894
Property and equipment		162,990
Identifiable intangibles		980,000
Accounts payable and accrued expenses		-1,682,782
Note payable		-426,044
Total Net Assets Acquired		5,014,256
Gain on bargain purchase		-1,014,256
Acquisition consideration		$4,000,000		$4,000,000

Inventory_Details

Inventory (Details) (USD $)	Mar. 31, 2015	Dec. 31, 2014
Inventory.
Raw materials and supplies	$22,654,432	$18,501,386
Work-in-process	2,092,409	237,268
Finished goods	7,346,074	5,996,947
Total inventory	$32,092,915	$24,735,601

Redeemable_Preferred_Stock_Det

Redeemable Preferred Stock (Details) (USD $)	3 Months Ended
	Mar. 31, 2015	Dec. 31, 2014	8-May-13
Redeemable preferred stock
Redeemable stock issued (in shares)	5,231	5,231
Redeemable stock issued, par value (in dollars per share)	$0.01	$0.01
Original issue price	$2,595,400
Conversion price per share	$0.23
Series C redeemable convertible preferred stock
Redeemable preferred stock
Dividend rate	8.00%
Air Liquide | Series C redeemable convertible preferred stock
Redeemable preferred stock
Redeemable stock issued (in shares)			5,231

Earnings_Per_Share_Details

Earnings Per Share (Details) (USD $)	3 Months Ended		12 Months Ended
	Mar. 31, 2015	Mar. 31, 2014	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Numerator:
Net loss attributable to common shareholders	($11,077,851)	($75,909,008)	($88,600,000)	($62,800,000)	($31,900,000)
Denominator:
Weighted average number of common shares outstanding (in shares)	173,365,830	133,750,522

Earnings_Per_Share_Details_2

Earnings Per Share (Details 2) (USD $)	0 Months Ended	1 Months Ended	3 Months Ended		0 Months Ended	1 Months Ended
	Mar. 31, 2015	31-May-11	Mar. 31, 2015	Mar. 31, 2014	Mar. 31, 2014	Feb. 28, 2013	Jan. 31, 2014	31-May-14
Dilutive potential common shares
Stock options outstanding	8,191,928		8,191,928	4,785,485	4,785,485
Restricted stock outstanding	395,558		395,558	650,002	650,002
Common stock warrants (1)	4,219,442		4,219,442	4,250,490	4,250,490
Preferred stock (2)	5,554,594		5,554,594	11,065,897	11,065,897
Number of dilutive potential common shares	18,361,522		18,361,522	20,751,874	20,751,874
Earnings Per Share
Weighted average exercise price	$3.84
Preferred stock (2)	5,554,594		5,554,594	11,065,897	11,065,897
Warrants issued in May, 2011
Earnings Per Share
Number of warrants issued (in shares)		7,128,563
Antidilutive shares excluded from calculation of diluted earnings per share		22,995,365
Number of warrants unexercised (in shares)			219,342	250,390
Warrants issued in February, 2013
Earnings Per Share
Number of warrants issued (in shares)						23,637,500
Number of warrants unexercised (in shares)	100				100
Warrants issued in January, 2014
Earnings Per Share
Number of warrants issued (in shares)							4,000,000
Series C redeemable convertible preferred stock
Dilutive potential common shares
Preferred stock (2)								10,431
Earnings Per Share
Preferred stock (2)								10,431
Number of preferred shares that had been converted to common stock	5,200

Intangible_Assets_Details

Intangible Assets (Details) (USD $)	0 Months Ended
	Mar. 31, 2015	Dec. 31, 2014	Mar. 31, 2015	Dec. 31, 2014
Gross carrying amount and accumulated amortization of acquired identifiable intangible assets
Gross Carrying Amount	$19,016,835	$19,016,835	$19,016,835	$19,016,835
Accumulated amortization	-18,134,960	-17,526,516	-18,134,960	-17,526,516
Total	881,875	1,490,319	881,875	1,490,319
Acquired technology
Gross carrying amount and accumulated amortization of acquired identifiable intangible assets
Weighted Average Amortization Period	8 years	8 years
Gross Carrying Amount	17,696,835	17,696,835	17,696,835	17,696,835
Accumulated amortization	-17,107,377	-16,539,683	-17,107,377	-16,539,683
Total	589,458	1,157,152	589,458	1,157,152
Customer relationships
Gross carrying amount and accumulated amortization of acquired identifiable intangible assets
Weighted Average Amortization Period	8 years	8 years
Gross Carrying Amount	1,260,000	1,260,000	1,260,000	1,260,000
Accumulated amortization	-1,015,583	-977,833	-1,015,583	-977,833
Total	244,417	282,167	244,417	282,167
Trademark
Gross carrying amount and accumulated amortization of acquired identifiable intangible assets
Weighted Average Amortization Period	5 years	5 years
Gross Carrying Amount	60,000	60,000	60,000	60,000
Accumulated amortization	-12,000	-9,000	-12,000	-9,000
Total	$48,000	$51,000	$48,000	$51,000

Property_Plant_and_Equipment_D

Property, Plant and Equipment (Details) (USD $)	Mar. 31, 2015	Dec. 31, 2014
Property, plant and equipment
Property, plant, and equipment, gross	$32,050,627	$31,850,662
Less accumulated depreciation	-26,855,332	-26,538,755
Property, plant, and equipment, net	5,195,295	5,311,907
Land.
Property, plant and equipment
Property, plant, and equipment, gross	90,000	90,000
Buildings.
Property, plant and equipment
Property, plant, and equipment, gross	15,332,232	15,332,232
Building improvements
Property, plant and equipment
Property, plant, and equipment, gross	5,031,803	5,031,803
Software, machinery and equipment
Property, plant and equipment
Property, plant, and equipment, gross	$11,596,592	$11,396,627

Capital_Lease_Details

Capital Lease (Details) (USD $)	Mar. 31, 2015	Dec. 31, 2014
Capital Lease
Leased property under capital lease	$3,098,921	$3,098,921
Less accumulated depreciation	-1,291,218	-1,162,095
Leased property under capital lease, net	$1,807,703	$1,936,826

Finance_Obligation_Details

Finance Obligation (Details) (USD $)	3 Months Ended
	Mar. 31, 2015	Dec. 31, 2014
Finance Obligation.
Lease term	15 years
Finance Obligation	$2,408,294	$2,426,028
Current portion of finance obligation in sale-leaseback transaction	68,000
Standby letter of credit amount	$500,000
Percentage of collateralization of standby letter of credit	100.00%
Period of renewal of standby letter of credit	10 years

Income_Taxes_Details

Income Taxes (Details) (USD $)	3 Months Ended
In Millions, unless otherwise specified	Mar. 31, 2015
Income Taxes.
Federal and state net operating loss carryforwards amount subject to IRC Section 382 limitations	$728
Unused net operating loss carryforwards	776
Amount of net operating loss carryforwards which will expire prior to utilization	715
Recognition period for net unrealized built in losses	5 years
Unfavorable book to tax add backs in U.S. corporate income tax return amount	19.4
Gross deferred tax liability	$7.40

Income_Taxes_Details_2

Income Taxes (Details 2) (USD $)	Mar. 31, 2015	Mar. 31, 2014
In Millions, unless otherwise specified
Income Taxes.
Accrued interest and penalties	$0.40	$0.40

Fair_Value_Measurements_Detail

Fair Value Measurements (Details) (Recurring basis, Warrants, USD $)	Mar. 31, 2015	Dec. 31, 2014
Significant Other Unobservable Inputs (Level 3)
Fair Value
Financial liabilities	$7,649,618	$9,418,413
Total.
Fair Value
Financial liabilities	$7,649,618	$9,418,413

Fair_Value_Measurements_Detail1

Fair Value Measurements (Details 2) (USD $)	3 Months Ended
	Mar. 31, 2014	Mar. 31, 2015
Reconciliations of the beginning and ending balances for liabilities measured at fair value on a recurring basis using significant unobservable inputs (i.e. Level 3)
Balance at the beginning of the period	$28,829,849
Change in fair value of common stock warrants	68,433,468
Issuance of common stock warrants	11,773,240
Exercise of common stock warrants	-83,294,149
Balance at the end of the period	25,742,408
Warrants
Reconciliations of the beginning and ending balances for liabilities measured at fair value on a recurring basis using significant unobservable inputs (i.e. Level 3)
Balance at the beginning of the period		9,418,413
Change in fair value of common stock warrants		-1,768,795
Balance at the end of the period		$7,649,618

Fair_Value_Measurements_Detail2

Fair Value Measurements (Details 3)	3 Months Ended	0 Months Ended
	Mar. 31, 2015	Mar. 31, 2015	Dec. 31, 2014
Valuation technique for assets measured and recorded at fair value
Expected dividend yield (as a percent)	0.00%
Minimum
Valuation technique for assets measured and recorded at fair value
Risk-free interest rate (as a percent)		0.25%	0.21%
Volatility (as a percent)		107.98%	119.16%
Expected average term		1 year 2 months 1 day	1 year 5 months 1 day
Maximum
Valuation technique for assets measured and recorded at fair value
Risk-free interest rate (as a percent)		1.27%	1.35%
Volatility (as a percent)		129.60%	136.62%
Expected average term		3 years 9 months 18 days	4 years 15 days

Warranty_Reserve_Details

Warranty Reserve (Details) (USD $)	3 Months Ended
	Mar. 31, 2015	Mar. 31, 2014
Product warranty activity
Beginning balance - January 1	$1,311,442	$1,608,131
Additions for current period deliveries	111,107	227,431
Reductions for payments made	-195,180	-357,391
Ending balance - December 31	$1,227,369	$1,478,171
GenDrive contracts | Minimum
Product warranty period, Minimum	1 year
GenDrive contracts | Maximum
Product warranty period, Maximum	2 years
ReliOn contracts | Minimum
Product warranty period, Minimum	2 years
ReliOn contracts | Maximum
Product warranty period, Maximum	5 years

Commitment_and_Contingencies_D

Commitment and Contingencies (Details) (USD $)	0 Months Ended		3 Months Ended
	Mar. 31, 2015	Dec. 31, 2014	Mar. 31, 2014	Sep. 30, 2011
			item
Commitments and Contingencies.
Letter of credit with Silicon Valley Bank				$525,000
Accounts receivable. | Credit risk | Customers
Customer Concentration
Number of customers	4	4
Concentration risk (as a percent)	62.20%	69.90%
Accounts receivable. | Credit risk | Customer one
Customer Concentration
Concentration risk (as a percent)	30.80%	30.20%
Accounts receivable. | Credit risk | Customer two
Customer Concentration
Concentration risk (as a percent)	14.40%	16.00%
Accounts receivable. | Credit risk | Customer three
Customer Concentration
Concentration risk (as a percent)	10.30%	13.40%
Accounts receivable. | Credit risk | Customer four
Customer Concentration
Concentration risk (as a percent)	6.70%	10.30%
Revenues. | Credit risk | Customers
Customer Concentration
Number of customers	1		2
Concentration risk (as a percent)	63.50%		31.60%
Revenues. | Credit risk | Customer one
Customer Concentration
Concentration risk (as a percent)			21.10%
Revenues. | Credit risk | Customer two
Customer Concentration
Concentration risk (as a percent)			10.50%