Tecogen (TGEN) 10-Q 15 May 18 2018 Q1 Quarterly report Financial data

Document and Entity Information

Document and Entity Information Document and Entity Information - shares	3 Months Ended
	Mar. 31, 2018	Apr. 30, 2018
Document and Entity Information [Abstract]
Entity Registrant Name	TECOGEN INC.
Entity Central Index Key	1,537,435
Current Fiscal Year End Date	--12-31
Entity Filer Category	Smaller Reporting Company
Document Type	10-Q
Document Period End Date	Mar. 31, 2018
Document Fiscal Year Focus	2,018
Document Fiscal Period Focus	Q1
Amendment Flag	false
Entity Common Stock, Shares Outstanding		24,819,646

Condensed Consolidated Balance

Condensed Consolidated Balance Sheets - USD ($)	Mar. 31, 2018	Dec. 31, 2017
Current assets:
Cash and cash equivalents	$ 1,202,334	$ 1,673,072
Accounts receivable, net	11,790,537	9,536,673
Unbilled revenue	4,745,320	3,963,133
Inventory, net	5,096,023	5,130,805
Due from related party	0	585,492
Prepaid and other current assets	870,680	771,526
Total current assets	23,704,894	21,660,701
Property, plant and equipment, net	12,048,483	12,265,711
Intangible assets, net	2,948,359	2,896,458
Goodwill	13,365,655	13,365,655
Other assets	462,870	482,551
TOTAL ASSETS	52,530,261	50,671,076
Current liabilities:
Accounts payable	6,835,299	5,095,285
Accrued expenses	1,705,890	1,416,976
Deferred revenue	1,509,224	1,293,638
Loan due to related party	850,000	850,000
Interest payable, related party	64,840	52,265
Total current liabilities	10,965,253	8,708,164
Long-term liabilities:
Deferred revenue, net of current portion	303,002	538,100
Unfavorable contract liability, net	7,464,950	7,729,667
Total liabilities	18,733,205	16,975,931
Commitments and contingencies
Tecogen Inc. shareholders’ equity:
Common stock, $0.001 par value; 100,000,000 shares authorized; 24,807,096 and 24,766,892 issued and outstanding at March 31, 2018 and December 31, 2017, respectively	24,807	24,767
Additional paid-in capital	56,264,398	56,176,330
Accumulated other comprehensive loss-investment securities	0	(165,317)
Accumulated deficit	(22,940,803)	(22,796,246)
Total Tecogen Inc. stockholders’ equity	33,348,402	33,239,534
Noncontrolling interest	448,654	455,611
Total stockholders’ equity	33,797,056	33,695,145
TOTAL LIABILITIES AND STOCKHOLDERS’ EQUITY	$ 52,530,261	$ 50,671,076

Condensed Consolidated Balance3

Condensed Consolidated Balance Sheets (Parenthetical) - $ / shares	Mar. 31, 2018	Dec. 31, 2017
Statement of Financial Position [Abstract]
Common stock, par value	$ 0.001	$ 0.001
Common stock, shares authorized	100,000,000	100,000,000
Common stock, shares issued	24,807,096	24,766,892
Common stock, shares outstanding	24,807,096	24,766,892

Condensed Consolidated Statemen

Condensed Consolidated Statements of Operations - USD ($)	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Revenues
Products	$ 3,673,506	$ 2,807,347
Services	4,719,386	4,039,420
Energy production	1,782,535	0
Total revenues	10,175,427	6,846,767
Cost of sales
Products	2,409,115	1,756,849
Services	2,782,854	2,175,245
Energy production	1,145,655	0
Total cost of sales	6,337,624	3,932,094
Gross profit	3,837,803	2,914,673
Operating expenses
General and administrative	2,789,549	2,208,905
Selling	675,118	447,452
Research and development	302,230	180,614
Total operating expenses	3,766,897	2,836,971
Income from operations	70,906	77,702
Other expense
Interest income and other expense, net	(1,072)	(1,213)
Interest expense	(13,013)	(31,702)
Unrealized loss on investment securities	(19,681)	0
Total other expense, net	(33,766)	(32,915)
Consolidated net income	37,140	44,787
Income attributable to the noncontrolling interest	(16,381)	0
Net income attributable to Tecogen Inc.	$ 20,759	$ 44,787
Net income per share - basic (in USD per share)	$ 0	$ 0
Net income per share - diluted (in USD per share)	$ 0	$ 0
Weighted average shares outstanding - basic (shares)	24,803,527	20,037,795
Weighted average shares outstanding - diluted (shares)	24,881,185	20,317,142

Condensed Consolidated Stateme5

Condensed Consolidated Statements of Cash Flows - USD ($)	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
CASH FLOWS FROM OPERATING ACTIVITIES:
Consolidated net income	$ 37,140	$ 44,787
Adjustments to reconcile net income to net cash used in operating activities:
Depreciation, accretion and amortization, net	199,181	64,281
Provision (recovery) of inventory reserve	1,000	(36,000)
Stock-based compensation	40,416	48,842
Non-cash interest expense	0	203
Loss on sale of assets	4,120	2,909
Provision for losses on accounts receivable	4,600	0
Changes in operating assets and liabilities, net of effects of acquisitions
Accounts receivable	(1,496,737)	(471,660)
Unbilled revenue	(549,647)	(77,410)
Inventory, net	33,782	(1,265,013)
Due from related party	0	(75,705)
Prepaid expenses and other current assets	(99,153)	(199,561)
Other non-current assets	19,681	(69,875)
Increase (decrease) in:
Accounts payable	855,949	644,323
Accrued expenses and other current liabilities	288,913	(224,394)
Deferred revenue	(64,122)	61,364
Interest payable, related party	12,575	0
Net cash used in operating activities	(712,302)	(1,552,909)
CASH FLOWS FROM INVESTING ACTIVITIES:
Purchases of property and equipment	(145,326)	(73,330)
Proceeds from sale of assets	3,606	0
Purchases of intangible assets	(83,856)	(53,608)
Cash acquired in asset acquisition	442,786	0
Expenses associated with asset acquisition	(553)	0
Distributions to noncontrolling interest	(23,338)	0
Net cash provided by (used in) investing activities	193,319	(126,938)
CASH FLOWS FROM FINANCING ACTIVITIES:
Proceeds from the exercise of stock options	48,245	106,835
Net cash provided by financing activities	48,245	106,835
Change in cash and cash equivalents	(470,738)	(1,573,012)
Cash and cash equivalents, beginning of the period	1,673,072	3,721,765
Cash and cash equivalents, end of the period	1,202,334	2,148,753
Non-cash investing and financing activities:
Cash paid for interest	0	31,150
Exchange of stock for non-controlling interest in Ilios	$ 0	$ 330,852

Description of business and bas

Description of business and basis of presentation	3 Months Ended
	Mar. 31, 2018
Accounting Policies [Abstract]
Description of business and basis of presentation	Description of Business and Basis of Presentation Description of business Tecogen Inc., or the Company, we, our or us produces commercial and industrial, natural-gas-fueled engine-driven, combined heat and power (CHP) products that reduce energy costs, decrease greenhouse gas emissions and alleviate congestion on the national power grid. The Company’s products supply electric power or mechanical power for cooling, while heat from the engine is recovered and purposefully used at a facility. The Company also installs, owns, operates and maintains complete energy systems and other complementary systems at customer sites and sells electricity, hot water, heat and cooling energy under long-term contracts at prices guaranteed to the customer to be below conventional utility rates. The majority of the Company’s customers are located in regions with the highest utility rates, typically California, the Midwest and the Northeast. The Company's common stock is listed on NASDAQ under the ticker symbol TGEN. On May 18, 2017, the Company acquired 100% of the outstanding common stock of American DG Energy Inc., formerly a related entity, in a stock-for-stock merger (see Note 4. Acquisition of American DG Energy Inc. ). Basis of Presentation The accompanying unaudited condensed consolidated financial statements have been prepared in accordance with generally accepted accounting principles for interim financial information and with the instructions to Form 10-Q and Article 8 of Regulation S-X. Accordingly, they do not include all of the information and footnotes required by generally accepted accounting principles for complete financial statements. In the opinion of management, all adjustments considered necessary for a fair presentation have been included. Operating results for the three months ended March 31, 2018 are not necessarily indicative of the results that may be expected for the year ending December 31, 2018 . The condensed consolidated balance sheet at December 31, 2017 has been derived from the audited consolidated financial statements at that date but does not include all of the information and footnotes required by generally accepted accounting principles for complete financial statements. For further information, refer to the consolidated financial statements and footnotes thereto included in Tecogen Inc.'s Annual Report on Form 10-K for the year ended December 31, 2017 . There have been certain changes in accounting principles as discussed below in the section entitled "Significant New Accounting Standards Adopted this Period.". The accompanying unaudited condensed consolidated financial statements include the accounts of the Company and entities in which it has a controlling financial interest. Those entities include the Company's wholly-owned subsidiaries American DG Energy Inc., TTcogen LLC, and a joint venture, American DG New York, LLC, in which American DG Energy Inc. holds a 51.0% interest. Investments in partnerships and companies in which the Company does not have a controlling financial interest but where we have significant influence are accounted for under the equity method. Any intercompany transactions have been eliminated in consolidation. The Company’s operations are comprised of two business segments. Our Products and Services segment designs, manufactures and sells industrial and commercial cogeneration systems as described above. Our Energy Production segment sells energy in the form of electricity, heat, hot water and cooling to our customers under long-term sales agreements. Reclassification Certain prior period amounts have been reclassified to conform with current year presentation. Use of Estimates The preparation of financial statements in conformity with accounting principles generally accepted in the United States of America requires 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. Income Taxes The provisions for income taxes in the accompanying unaudited consolidated statements of operations differ from that which would be expected by applying the federal statutory tax rate primarily due to losses for which no benefit is recognized. Significant New Accounting Standards Adopted this Period Revenue Recognition In May 2014, the Financial Accounting Standards Board ("FASB") issued an accounting standard update (ASU 2014-09) related to revenue from contracts with customers, which, along with amendments issued in 2015 and 2016, supersedes nearly all current U.S. GAAP guidance on this topic and eliminates industry-specific guidance. The underlying principle is to recognize revenue when promised goods or services are transferred to customers in an amount that reflects the consideration that is expected to be received for those goods or services. The Company adopted this accounting standard update on a modified retrospective basis in the first quarter of 2018. See Note 2. , Revenue for further discussion. Investments in Equity Securities In January 2016, the FASB issued an accounting standard update related to investments in equity securities requiring unrealized holding gains and losses to be included in net income. Prior to this update, unrealized holding gains and losses related to available-for-sale securities were included in accumulated other comprehensive income and not included in determining net income. This accounting standard update became effective for the Company beginning in the first quarter of 2018 and is applied by means of a cumulative-effect adjustment to the balance sheet as of January 1, 2018. The Company adopted this accounting standard update in the first quarter of 2018 which resulted in reclassification of $165,317 of cumulative unrealized holding losses from accumulated other comprehensive loss to accumulated deficit. The future impact of recognizing unrealized holding gains or losses in net income is dependent on the movement in the stock prices related to such investments. Significant New Accounting Standards or Updates Not Yet Effective Leases In February 2016, the FASB issued an accounting standard update related to leases requiring lessees to recognize operating and financing lease liabilities on the balance sheet, as well as corresponding right-of-use assets. The new lease standard also makes some changes to lessor accounting and aligns key aspects of the lessor accounting model with the revenue recognition standard. In addition, disclosures will be required to enable users of financial statements to assess the amount, timing, and uncertainty of cash flows arising from leases. The accounting standard update will be effective for the Company beginning in the first quarter of fiscal 2019 on a modified retrospective basis, and early adoption is permitted. The Company is currently evaluating the impact of this accounting standard update on its consolidated financial statements.

Revenue

Revenue	3 Months Ended
	Mar. 31, 2018
Revenue Recognition [Abstract]
Revenue	Revenue Revenue is recognized when performance obligations under the terms of a contract with our customer are satisfied; generally this occurs with the transfer of control of our products, services and energy production. Revenue is measured as the amount of consideration we expect to receive in exchange for transferring goods or providing services or energy to customers. Shipping and handling fees billed to customers in a sales transaction are recorded in revenue and shipping and handling costs incurred are recorded in cost of sales. The Company has elected to exclude from revenue any value add, sales and other taxes which it collects concurrent with revenue-producing activities. These accounting policy elections are consistent with the manner in which the Company historically recorded shipping and handling fees and taxes. Incremental costs incurred by us in obtaining a contract with a customer are negligible, if any, and are expensed ratably in proportion to the related revenue recognized. The adoption and application of ASU 2014-09 did not have an impact upon adoption or on the amounts reported for the interim period ended March 31, 2018 as compared with the guidance that was in effect before the adoption and application of ASU 2014-09. Disaggregated Revenue In general, the Company's business segmentation is aligned according to the nature and economic characteristics of its products and customer relationships and provides meaningful disaggregation of each business segment's results of operations. The following table further disaggregates our revenue by major source by segment for the three months ended March 31, 2018 . Products and Services Energy Production Total Products $ 3,673,506 $ — $ 3,673,506 Installation services 2,405,655 — 2,405,655 Maintenance services 2,313,731 — 2,313,731 Energy production — 1,782,535 1,782,535 Total revenue $ 8,392,892 $ 1,782,535 $ 10,175,427 Product and Services Segment Products. We transfer control and generally recognize a sale when we ship a product from our manufacturing facility at which point a customer takes ownership to the product. Payment terms on product sales are generally 30 days. We recognize revenue in certain circumstances before delivery to the customer has occurred (commonly referred to as bill and hold transactions). We recognize revenue related to such transactions once, among other things, the customer has made a written fixed commitment to purchase the product(s) under normal billing and credit terms, the customer has requested the product(s) be held for future delivery as scheduled and designated by them, risk of ownership has been assumed by the customer, and the product(s) are tagged as sold and segregated for storage awaiting further direction from the customer. Due to the infrequent nature and duration of bill and hold arrangements, the value associated with custodial storage services is deemed immaterial in the context of the contract and in total, and accordingly, none of the transaction price is allocated to such service. Depending on the product and terms of the arrangement, we may defer the recognition of a portion of the transaction price received because we have to satisfy a future obligation (e.g., product start-up service). Amounts allocated to product start-up services are recognized as revenue when the start-up service has been completed. We use an observable selling price to determine standalone selling prices where available and either a combination of an adjusted market assessment approach, an expected cost plus a margin approach, and/or a residual approach to determine the standalone selling prices for separate performance obligations as a basis for allocating contract consideration when an observable selling price is not available. Amounts received but not recognized pending completion of performance are recognized as contract liabilities and are recorded as deferred revenue along with deposits by customers. Installation Services. We provide both complete turnkey installation services and what we refer to as light installation services. Complete turnkey installation services typically include all necessary engineering and design, labor, subcontract labor and service, and ancillary products and parts necessary to install a cogeneration unit including integration into the customers’ existing electrical and mechanical systems. Light installation services typically include some engineering and design as well as certain ancillary products and parts necessary for the customers’ installation of a cogeneration unit. Under light installation contracts, revenue related to ancillary products and parts is recognized when we transfer control of such items to the customer, generally when we ship them from our manufacturing facility, with revenue related to engineering and design services being recognized at the point where the customer can benefit from the service, generally as completed. Generally billings under light installation contracts are made when shipped and/or completed, with payment terms generally being 30 days. Under complete turnkey installation service contracts revenue is recognized over time using the percentage-of-completion method determined on a cost to cost basis. Our performance obligation under such contracts is satisfied progressively over time as enhancements are made to customer owned and controlled properties. We measure progress towards satisfaction of the performance obligation based on an input method based on cost which we believe is the most faithful depiction of the transfer of products and services to the customer under these contracts. When the financial metrics of a contract indicate a loss, our policy is to record the entire expected loss as soon as it is known. Contract costs and profit recognized to date under the percentage-of-completion method in excess of billings are recognized as contract assets and are recorded as unbilled revenue. Billings in excess of contract costs and profit are recognized as contract liabilities and are recorded as deferred revenue. Generally billings under complete turnkey installation contracts are made when contractually determined milestones of progress have been achieved, with payment terms generally being 30 days. Maintenance Services. Maintenance services are provided under either long-term maintenance contracts or one time maintenance contracts. Revenue under one time maintenance contracts is recognized when the maintenance service is completed. Revenue under long-term maintenance contracts is recognized either ratably over the term of the contract where the contract price is fixed or when the periodic maintenance activities are completed where the invoiced cost to the customer is based on run hours or kilowatts produced in a given period. We use an output method to measure progress towards completion of our performance obligation which results in the recognition of revenue on the basis of a direct measurement of the value to the customer of the services transferred to date relative to the remaining services promised under the contract. We use the practical expedient at ASC 606-10-55-18 of recognizing revenue in an amount equal to that amount to which we have the right to invoice the customer under the contract. Energy Production Segment Energy Production. Revenue from energy contracts is recognized when electricity, heat, hot and/or chilled water is produced by the Company owned on-site cogeneration systems. Each month we bill the customer and recognize revenue for the various forms of energy delivered, based on meter readings which capture the quantity of the various forms of energy delivered in a given month, under a contractually defined formula which takes into account the current month's cost of energy from the local power utility. As the various forms of energy delivered by us under energy production contracts are simultaneously delivered and consumed by the customer, our performance obligation under these contracts is considered to be satisfied over time. We use an output method to measure progress towards completion of our performance obligation which results in the recognition of revenue on the basis of a direct measurement of the value to the customer of the services transferred to date relative to the remaining services promised under the contract. We use the practical expedient at ASC 606-10-55-18 of recognizing revenue in an amount equal to that amount to which we have the right to invoice the customer under the contract. Payment terms on invoices under these contracts are generally 30 days. Contract Balances The timing of revenue recognition, billings and cash collections result in billed accounts receivable, unbilled revenue (contract assets) and deferred revenue, consisting of customer deposits and billings in excess of revenue recognized (contract liabilities) on the Consolidated Condensed Balance Sheets. Revenue recognized during the interim period ended March 31, 2018 that was included in unbilled revenue at the beginning of the period was approximately $2.6 million . Approximately $1.8 million of revenue was billed in this period that had been recognized in previous periods. Revenue recognized during the interim period ended March 31, 2018 that was included in deferred revenue at the beginning of the period was approximately $1.6 million . The decrease in the deferred revenue balance during the interim period ended March 31, 2018 is primarily a result of $1.6 million of revenue recognized during the period that was included in the deferred revenue balance at the date of adoption, offset by cash payments of $1.5 million received in advance of satisfying performance obligations. Remaining Performance Obligations Remaining performance obligations related to ASC 606 represent the aggregate transaction price allocated to performance obligations with an original contract term greater than one year, excluding certain maintenance contracts and all energy production contracts where a direct measurement of the value to the customer is used as a method of measuring progress towards completion of our performance obligation. Exclusion of these remaining performance obligations is due in part to the inability to quantify values based on unknown future levels of delivery and in some cases rates used to bill customers. Remaining performance obligations therefore consist of unsatisfied or partially satisfied performance obligations related to fixed price maintenance contracts and installation contracts. As of March 31, 2018 , the aggregate amount of the transaction price allocated to remaining performance obligations was approximately $1.8 million . The Company expects to recognize revenue of approximately 99% of the remaining performance obligations over the next 24 months, 77% recognized in the first 12 months and 22% recognized over the subsequent 12 months, and the remainder recognized thereafter.

Income (Loss) Per Common Share

Income (Loss) Per Common Share	3 Months Ended
	Mar. 31, 2018
Earnings Per Share [Abstract]
Income (Loss) Per Common Share	Basic and diluted income (loss) per share for the three months ended March 31, 2018 and 2017 , respectively, were as follows: Three months ended March 31, 2018 2017 Net income attributable to stockholders $ 20,759 $ 44,787 Weighted average shares outstanding - Basic 24,803,527 20,037,795 Basic income per share $ 0.00 $ 0.00 Weighted average shares outstanding - Diluted 24,881,185 20,317,142 Diluted income per share $ 0.00 $ 0.00 Anti-dilutive shares underlying stock options outstanding 77,658 — Anti-dilutive convertible debentures — 889,830

Acquisition of American DG Ener

Acquisition of American DG Energy, Inc.	3 Months Ended
	Mar. 31, 2018
Business Combinations [Abstract]
Acquisition of American DG Energy, Inc.	Acquisition of American DG Energy Inc. On May 18, 2017, we completed our acquisition, by means of a stock-for-stock merger, of 100% of the outstanding common shares of American DG Energy Inc. (“American DG Energy" or "ADGE”), a company which installs, owns, operates and maintains complete distributed generation of electricity systems, or DG systems or energy systems, and other complementary systems at customer sites and sells electricity, hot water, heat and cooling energy under long-term contracts at prices guaranteed to the customer to be below conventional utility rates, by means of a merger of one of our wholly owned subsidiaries with and into ADGE such that ADGE became a wholly owned subsidiary of Tecogen. We acquired ADGE to, among other reasons, expand our product offerings and benefit directly from the long-term contracted revenue streams generated by these installations. We gained control of ADGE on May 18, 2017 by issuing common stock of the Company to the prior stockholders of ADGE. We have included the financial results of ADGE in our condensed consolidated financial statements from the date of acquisition. For the three months ended March 31, 2018 , ADGE contributed $1,782,535 to our total revenues and $636,880 and to our gross profit. Unaudited Pro Forma Financial Information The unaudited pro forma financial information in the table below summarizes the combined results of operations for Tecogen and ADGE as though the companies were combined as of the beginning of fiscal 2017. The pro forma financial information for all periods presented also includes the business combination accounting effects resulting from the acquisition including amortization charges and credits from acquired intangible assets and liabilities (certain of which are preliminary), and depreciation adjustments related to fair value as though the aforementioned companies were combined as of the beginning of fiscal 2017. The pro forma financial information as presented below is for informational purposes only and is not indicative of the results of operations that would have been achieved if the acquisition had taken place at the beginning of fiscal 2017. Three months ended March 31, 2017 Total revenues $ 8,276,124 Net income (loss) (460,935 ) Basic earnings (loss) per share (0.02 ) Diluted earnings (loss) per share (0.02 ) One-time acquisition-related expenses related to the merger incurred during the three-month period ended March 31, 2017 are not included in the unaudited pro forma financial information as they are not expected to have a continuing impact on the consolidated results.

Property, Plant and Equipment

Property, Plant and Equipment	3 Months Ended
	Mar. 31, 2018
Property, Plant and Equipment [Abstract]
Property, Plant and Equipment	Property, Plant and Equipment Property, plant and equipment at March 31, 2018 and December 31, 2017 consisted of the following: Estimated Useful March 31, 2018 December 31, 2017 Energy systems 1 - 15 years $ 12,548,796 $ 12,466,642 Machinery and equipment 5 - 7 years 1,284,203 1,215,951 Furniture and fixtures 5 years 104,317 205,320 Computer software 3 - 5 years 233,478 115,253 Leasehold improvements * 450,772 440,519 14,621,566 14,443,685 Less - accumulated depreciation and amortization (2,573,083 ) (2,177,974 ) $ 12,048,483 $ 12,265,711 * Lesser of estimated useful life of asset or lease term Depreciation and amortization expense on property and equipment for the three months ended March 31, 2018 and 2017 was $402,336 and $39,453 , respectively.

Intangible Assets and Liabiliti

Intangible Assets and Liabilities Other Than Goodwill	3 Months Ended
	Mar. 31, 2018
Goodwill and Intangible Assets Disclosure [Abstract]
Intangible Assets and Liabilities Other Than Goodwill	Intangible Assets and Liabilities Other Than Goodwill As of March 31, 2018 and December 31, 2017 the Company had the following amounts related to intangible assets and liabilities other than goodwill: March 31, 2018 December 31, 2017 Intangible assets Cost Accumulated Amortization Total Cost Accumulated Amortization Total Product certifications $ 651,639 $ (298,874 ) $ 352,765 $ 605,704 $ (285,341 ) $ 320,363 Patents 844,309 (162,343 ) 681,966 808,323 (154,972 ) 653,351 Developed technology 240,000 (80,000 ) 160,000 240,000 (76,000 ) 164,000 Trademarks 20,540 — 20,540 19,540 — 19,540 In Process R&D 263,936 — 263,936 263,001 — 263,001 Favorable contract asset 1,561,739 (122,194 ) 1,439,545 1,561,739 (85,536 ) 1,476,203 $ 3,611,770 $ (663,411 ) $ 2,948,359 $ 3,498,307 $ (601,849 ) $ 2,896,458 Intangible liability Unfavorable contract liability $ 8,341,922 $ (876,972 ) $ 7,464,950 $ 8,341,922 $ (612,255 ) $ 7,729,667 The aggregate amortization expense related to intangible assets and liabilities exclusive of contract related intangibles for the three months ended March 31, 2018 and 2017 was $ 24,903 and $24,828 , respectively. The net credit to cost of sales related to the amortization of contract related intangible assets and liabilities for the three months ended March 31, 2018 and 2017 was $228,059 and $ 0 , respectively. Favorable/Unfavorable Contract Assets and Liabilities The favorable contract asset and unfavorable contract liability in the foregoing table represent the estimated fair value of American DG Energy's customer contracts (both positive for favorable contracts and negative for unfavorable contracts) which were acquired by the Company on May 18, 2017 (see Note 4. Acquisition of American DG Energy Inc. ). Amortization of intangibles including contract related amounts is calculated using the straight line method over the remaining useful life or contract term. Aggregate future amortization over the next five years is estimated to be as follows: Year 1 $ (628,543 ) Year 2 (517,196 ) Year 3 (524,276 ) Year 4 (535,463 ) Year 5 (494,180 )

Stock-Based Compensation

Stock-Based Compensation	3 Months Ended
	Mar. 31, 2018
Equity [Abstract]
Stock-Based Compensation	Stock-Based Compensation Stock-Based Compensation The Company adopted a 2006 Stock Option and Incentive Plan, or the Plan, under which the Board of Directors may grant incentive or non-qualified stock options and stock grants to key employees, directors, advisors and consultants of the Company. The Plan was amended at various dates by the Board of Directors to increase the reserved shares of common stock issuable under the Plan to 3,838,750 as of March 31, 2018 , or the Amended Plan. Stock options vest based upon the terms within the individual option grants, with an acceleration of the unvested portion of such options upon a change in control event, as defined in the Amended Plan. The options are not transferable except by will or domestic relations order. The option price per share under the Amended Plan cannot be less than the fair market value of the underlying shares on the date of the grant. The number of shares remaining available for future issuance under the Amended Plan as of March 31, 2018 was 2,122,356 . Stock option activity for the three months ended March 31, 2018 was as follows: Common Stock Options Number of Options Exercise Share Weighted Price Weighted Life Aggregate Value Outstanding, December 31, 2017 1,061,552 $0.79-$18.15 $ 3.60 4.95 years $ 291,449 Granted 37,000 $2.30-$2.70 $2.43 Exercised (40,204 ) $1.20 $1.20 Canceled and forfeited (35,609 ) $2.60-$6.74 $4.31 Outstanding, March 31, 2018 1,022,739 $0.79-$18.15 $ 3.62 5.41 years $ 312,550 Exercisable, March 31, 2018 811,864 $ 3.54 $ 296,630 Vested and expected to vest, March 31, 2018 991,108 $ 3.61 $ 312,550 Consolidated stock-based compensation expense for the three months ended March 31, 2018 and 2017 was $40,416 and $48,842 , respectively. No tax benefit was recognized related to the stock-based compensation recorded during the periods.

Fair Value Measurements

Fair Value Measurements	3 Months Ended
	Mar. 31, 2018
Fair Value Disclosures [Abstract]
Fair Value Measurements	Fair Value Measurements The fair value topic of the FASB Accounting Standards Codification defines fair value as the exchange price that would be received for an asset or paid to transfer a liability (an exit price) in the principal or most advantageous market for the asset or liability in an orderly transaction between market participants on the measurement date. The accounting guidance also establishes a fair value hierarchy which requires an entity to maximize the use of observable inputs, where available, and minimize the use of unobservable inputs when measuring fair value. There are three levels of inputs that may be used to measure fair value: Level 1 - Unadjusted quoted prices in active markets for identical assets or liabilities. The Company currently does not have any Level 1 financial assets or liabilities. Level 2 - Observable inputs other than quoted prices included in Level 1. Level 2 inputs include quoted prices for identical assets or liabilities in non-active markets, quoted prices for similar assets or liabilities in active markets and inputs other than quoted prices that are observable for substantially the full term of the asset or liability. Level 3 - Unobservable inputs reflecting management’s own assumptions about the input used in pricing the asset or liability. The Company does not currently have any Level 3 financial assets or liabilities. The following table presents the asset reported in the consolidated balance sheet measured at its fair value on a recurring basis as of March 31, 2018 by level within the fair value hierarchy. March 31, 2018 Quoted prices in active markets for identical assets Significant other observable inputs Significant unobservable inputs Total Level 1 Level 2 Level 3 Total gains (losses) Recurring fair value measurements Marketable equity securities EuroSite Power Inc. $ 334,570 $ — $ 334,570 $ — $ (184,998 ) Total recurring fair value measurements $ 334,570 $ — $ 334,570 $ — $ (184,998 ) The Company utilizes a Level 2 category fair value measurement to value its investment in EuroSite Power as a marketable equity security at period end. That measurement is equal to the quoted market closing price at period end. Since this security is not actively traded the Company classifies as Level 2. The following table summarizes changes in level 2 assets which are comprised of marketable equity securities for the period: Fair value at acquisition on May 17, 2017 $ 519,568 Unrealized loss included in other comprehensive loss for the year ended December 31, 2017 (165,317 ) Fair value at December 31, 2017 354,251 Unrealized loss included in net income for the quarter ended March 31, 2018 (19,681 ) Fair value at March 31, 2018 $ 334,570

Commitments and contingencies

Commitments and contingencies	3 Months Ended
	Mar. 31, 2018
Commitments and Contingencies Disclosure [Abstract]
Commitments and contingencies	Commitments and Contingencies The Company guarantees certain obligations of a former subsidiary of American DG Energy, EuroSite Power Inc. These guarantees include a payment performance guarantee in respect of collateralized equipment financing loans, with a remaining principal amount outstanding subject to the guarantee at March 31, 2018 of approximately $279,500 due ratably in equal installments through September 2021, and certain guarantees of performance in respect of certain customer contracts. Based on current conditions, the Company does not believe there to be any amounts probable of payment by the Company under any of the guarantees and has estimated the value associated with the non-contingent aspect of the guarantees is approximately $10,000 which is recorded as a liability in the accompanying financial statements. Legal Proceedings The Company is a party to a pending action in the United States District Court for the District of Massachusetts, described below, related to the merger with ADGE. Massachusetts Superior Court Action On or about February 6, 2017, ADGE, John Hatsopoulos, George N. Hatsopoulos, Charles T. Maxwell, Deanna M. Petersen, Christine Klaskin, John Rowe, Joan Giacinti, Elias Samaras, Tecogen, and the wholly owned subsidiary of the Company that merged with ADGE ("Merger Sub") were served with a Verified Complaint by William C. May ("May"), individually and on behalf of the other shareholders of ADGE as a class. The action was commenced in the Business Litigation Session of the Superior Court of the Commonwealth of Massachusetts, Civil Action No. 17-0390. The complaint alleged class action claims arising out of the proposed Merger. On May 31, 2017, May voluntarily dismissed the action and consolidated his claims with the pending federal action in the United States District Court for the District of Massachusetts, described below. If the complaint in the federal court is dismissed, it is possible that May or another plaintiff will recommence an action in state court with similar claims to those asserted by May. United States District Court Action On or about February 15, 2017, a lawsuit was filed in the United States District Court for the District of Massachusetts by Lee Vardakas (“Vardakas”), individually and on behalf of other stockholders of ADGE, naming ADGE, John N. Hatsopoulos, George N. Hatsopoulos, Benjamin Locke, Charles T. Maxwell, Deanna M. Petersen, Christine M. Klaskin, John Rowe, Joan Giacinti, Elias Samaras, Tecogen., Merger Sub., and Cassel Salpeter and Co., LLC, as defendants. The action is captioned Vardakas v. American DG Energy, Inc. , Case No. 17-CV-10247(LTS). At the time Vardakas commenced the action, his complaint challenged the proposed Merger between Tecogen and ADGE. Following the consummation of the Merger (and the appointment of May, from the Massachusetts Superior Court Action, as lead plaintiff), Vardakas filed an Amended Class Action Complaint (the “Amended Complaint”). The Amended Complaint discontinued the claims against Cassel Salpeter & Co., LLC but asserted against the remaining defendants claims under Section 14(a) of the Securities Exchange Act of 1934 (the “Exchange Act”) and SEC Rule 14a-9; claims against certain defendants for control person liability under § 20(a) of the Exchange Act (collectively, the “Federal Securities Law Claims”); and common law claims for breach of fiduciary duty and aiding and abetting (the “State Law Claims”). The Federal Securities Law Claims allege, in substance, that defendants made material nondisclosure in the proxy statement about the process leading to the Merger and about the fairness opinion relied upon by ADGE’s Board of Directors in recommending the Merger to shareholders. The State Law Claims assert, in substance, that defendants breached their fiduciary duties in negotiating and approving the Merger, which, plaintiff claims, deprived ADGE’s nonaffiliated shareholders of fair value for their shares. On July 19, 2017, defendants moved to dismiss the Amended Complaint. In their motion papers, defendants contended that the Federal Securities Law Claims are not sufficiently pleaded and fail to state a viable claim. On February 28, 2018, the parties presented their oral arguments on the defendant's motion to dismiss. On March 2, 2018 the district court rendered its decision, dismissing the Federal Securities Law Claims, but retaining the State Law Claims. The district court exercised supplemental jurisdiction over the State Law Claims and ordered the Defendants to file an answer to the Amended Complaint addressing the State Law Claims. On March 12, 2018, the Defendants filed their first answer. On May 2, 2018, the Defendants filed their amended answer to assert further defenses, and the judge in the district court ordered the parties to hold a mediation session. The Company believes that the lawsuit is without merit and intends to defend vigorously. The Amended Complaint does not specify the amount of damages claimed and the likelihood of an unfavorable outcome is not reasonably estimable.

Related party transactions

Related party transactions	3 Months Ended
	Mar. 31, 2018
Related Party Transactions [Abstract]
Related party transactions	Related Party Transactions In January of 2017, prior to its acquisition of American DG Energy, the Company purchased a large quantity of used equipment from American DG Energy for approximately $985,000 . Tecogen has sold a majority of this equipment to specific customers during the previous quarters. In connection with the acquisition of American DG Energy, the Company assumed a loan from John N. Hatsopoulos, the Company's Co-Chief Executive Officer and a Company Director. The loan is in the amount of $850,000 and bears interest at 6% , payable quarterly. On May 4, 2018, the Company, through payment of $919,590 , terminated the loan and all obligations under the loan. Ultra Emissions Technologies Ltd. ("Ultratek") By unanimous written consent on October 24, 2017, the shareholders of Ultratek voted to dissolve Ultratek, thus terminating the joint venture agreement dated December 28, 2015 and the license agreement between the Company and Ultratek. This joint venture agreement and license agreement is described in its entirety on the Company's Form 8-K that was filed with the Securities and Exchange Commission on December 31, 2015. Pursuant to the unanimous shareholder consent dissolving Ultratek, the Company received its full $2,000,000 investment in Ultratek upon the completion of the liquidation process. Further, upon termination of the license agreement all intellectual property immediately reverted to the Company. Upon dissolution, the Company purchased all of the remaining assets of Ultratek, including new intellectual property that Ultratek developed and other assets, for a total purchase price of $400,000 . TTcogen LLC On May 19, 2016, the Company along with Tedom a.s., a corporation incorporated in the Czech Republic and a European combined heat and power product manufacturer ("Tedom"), entered into a joint venture, where the Company held a 50% participating interest and the remaining 50% interest was held by Tedom. As part of the joint venture, the parties agreed to create a Delaware limited liability company, TTcogen LLC ("TTcogen"), to carry out the business of the venture. Tedom granted TTcogen the sole and exclusive right to market, sell, offer for sale, and distribute certain products as agreed to by the parties throughout the United States. The product offerings of the joint venture expand the current Tecogen product offerings to the MicroCHP of 35kW to large 4,000kW plants. Tecogen agreed to refer all appropriate sale leads to TTcogen regarding the products agreed to by the parties and Tecogen would have the first right to repair and maintain the products sold by TTcogen. Until the Company acquired the assets of TTcogen, the Company accounted for its interest in TTcogen's operations using the equity method of accounting. Any initial operating losses of TTcogen were borne and funded by Tedom. To the extent any such losses were borne and funded solely by Tedom, the Company did not recognize any portion of such losses given the Company did not guarantee the obligations of the joint venture nor is it committed to provide funding to the joint venture. On September 22, 2017, the Company provided written notice to Tedom and Tedom USA Inc., a Delaware subsidiary of Tedom (“Tedom USA”) that the Company is exercising its rights under the Joint Venture Agreement dated May 19, 2016 ("JVA") and the TTcogen LLC Operating Agreement ("LLC Operating Agreement"), of the immediate termination of the JVA and LLC Operating Agreement. This notice began the dissolution process under the LLC Operating Agreement. On March 27, 2018, the Company entered into a Membership Interest Purchase and Wind-Down Agreement (the “Purchase Agreement”) among the Company, Tedom, Tedom USA, and TTcogen. The Purchase Agreement follows the mutual agreement of the parties to terminate the joint venture between the Company and Tedom that resulted in the creation of TTcogen, and implements the acquisition by the Company of Tedom USA’s 50% membership interest in TTcogen for a purchase price of one dollar, plus $72,597 , which represents a portion of Tedom USA's initial investment in TTcogen, minus certain adjustments. The Purchase Agreement also grants TTcogen and the Company the exclusive right to market, sell, and distribute Tedom’s Micro T35 combined heat and power equipment within an agreed territory in the northeastern United States under certain conditions, and limits the Company’s right to sell certain competing products. The Company will provide services for Tedom equipment sold by TTcogen or the Company. The acquisition of Tedom's 50% membership interest for $72,598 was accounted for as an acquisition of assets, and not a business combination, due to the lack of an assembled workforce. The Company adopted the provisions of ASU 2017-01 "Business Combinations - Clarifying the Definition of a Business" at the beginning of 2018, which require, at a minimum, the presence of a input and substantive process that together significantly contribute to the ability to create an output. The lack of an assembled workforce results in the non presence of a substantive process. The following represents the consideration for and the fair value of assets acquired and liabilities assumed recognized at the acquisition date: Cash $ 442,786 Accounts receivable 176,235 Unbilled revenue 232,540 Fixed assets 47,508 Intangible assets 29,607 Accounts payable (811,468 ) Deferred revenue (44,610 ) Cash payable $ 72,598 The intangible asset represents contract backlog related to acquired contracts. The value assigned to contract backlog was determined based on the result of a discounted cash flow analysis, which resultant value was capped so as to preclude recognition of any amount in excess of cost after considering the fair values assigned to other assets acquired and liabilities assumed.

Segments

Segments	3 Months Ended
	Mar. 31, 2018
Segment Reporting [Abstract]
Segments	Segments As of March 31, 2018 , the Company was organized into two operating segments through which senior management evaluates the Company’s business. These segments, as described in more detail in Note 1, are organized around the products and services provided to customers and represent the Company’s reportable segments. Prior to the acquisition of ADGE (see Note 4. “Acquisition of American DG Energy Inc.”), the Company’s operations were comprised of a single segment.The following table presents information by reportable segment for the three months ended March 31, 2018 and 2017 : Products and Services Energy Production Corporate, other and elimination (1) Total Three months ended March 31, 2018 Revenue - external customers $ 8,392,892 $ 1,782,535 $ — $ 10,175,427 Intersegment revenue 355,169 — (355,169 ) — Total revenue $ 8,748,061 $ 1,782,535 $ (355,169 ) $ 10,175,427 Gross profit $ 3,200,923 $ 636,880 $ — $ 3,837,803 Identifiable assets $ 20,828,118 $ 13,394,893 $ 18,922,000 $ 53,145,011 Three months ended March 31, 2017 Revenue - external customers $ 6,846,767 $ — $ — $ 6,846,767 Intersegment revenue — — — — Total revenue $ 6,846,767 $ — $ — $ 6,846,767 Gross profit $ 2,914,673 $ — $ — $ 2,914,673 Identifiable assets $ 17,524,410 $ — $ 6,898,911 $ 24,423,321 (1) Corporate, intersegment revenue, other and elimination includes various corporate assets.

Subsequent Events

Subsequent Events	3 Months Ended
	Mar. 31, 2018
Subsequent Events [Abstract]
Subsequent Events	Subsequent Events On May 4, 2018 ("Closing Date") the Company, and its wholly owned subsidiaries, American DG Energy Inc. and TTcogen LLC (collectively, the "Borrowers"), entered into a Credit Agreement with Webster Business Credit Corporation that provides Borrowers a line of credit of up to $10 million on a revolving and secured basis, with availability based on certain accounts receivables, raw materials, and finished goods. Funds borrowed under the Agreement are payable on May 4, 2021. Borrowings under the Credit Agreement bear interest at a rate equal to, at the Borrower's option, either (1) One Month LIBOR, plus 3.00% , or (2) Lender’s Base Rate, plus 1.5% . Lender’s Base Rate is the highest of (a) the Federal Funds rate plus 0.5% , (b) Lender’s Prime Rate as adjusted by Lender from time to time, and (c) One Month LIBOR, plus 2.75% . Upon Closing, the Company borrowed funds under the Credit Agreement to repay the balance due to Mr. John N. Hatsopoulos, a director of the Company, under a $3 million Revolving Line of Credit in favor of ADGE dated December 22, 2016 (the “Revolving Line”) that the Company assumed on May 18, 2017 when it acquired ADGE. The Revolving Line was terminated on February 27, 2017, and the Company and Mr. Hatsopoulos agreed that the maturity date for the then outstanding indebtedness under the Revolving Line would be on or before May 25, 2018. ADGE had previously borrowed $850,000 under the Revolving Line, with interest at the rate of 6% per year. The payoff of the Revolving Line, including accrued interest through the Closing Date, was $919,590 . The Company has evaluated subsequent events through the date of this filing and determined that no additional subsequent events occurred that would require recognition in the consolidated financial statements or disclosure in the notes thereto.

Description of business and b18

Description of business and basis of presentation (Policies)	3 Months Ended
	Mar. 31, 2018
Accounting Policies [Abstract]
Principles of Consolidation and Basis of Presentation	Basis of Presentation The accompanying unaudited condensed consolidated financial statements have been prepared in accordance with generally accepted accounting principles for interim financial information and with the instructions to Form 10-Q and Article 8 of Regulation S-X. Accordingly, they do not include all of the information and footnotes required by generally accepted accounting principles for complete financial statements. In the opinion of management, all adjustments considered necessary for a fair presentation have been included. Operating results for the three months ended March 31, 2018 are not necessarily indicative of the results that may be expected for the year ending December 31, 2018 . The condensed consolidated balance sheet at December 31, 2017 has been derived from the audited consolidated financial statements at that date but does not include all of the information and footnotes required by generally accepted accounting principles for complete financial statements. For further information, refer to the consolidated financial statements and footnotes thereto included in Tecogen Inc.'s Annual Report on Form 10-K for the year ended December 31, 2017 . There have been certain changes in accounting principles as discussed below in the section entitled "Significant New Accounting Standards Adopted this Period.". The accompanying unaudited condensed consolidated financial statements include the accounts of the Company and entities in which it has a controlling financial interest. Those entities include the Company's wholly-owned subsidiaries American DG Energy Inc., TTcogen LLC, and a joint venture, American DG New York, LLC, in which American DG Energy Inc. holds a 51.0% interest. Investments in partnerships and companies in which the Company does not have a controlling financial interest but where we have significant influence are accounted for under the equity method. Any intercompany transactions have been eliminated in consolidation. The Company’s operations are comprised of two business segments. Our Products and Services segment designs, manufactures and sells industrial and commercial cogeneration systems as described above. Our Energy Production segment sells energy in the form of electricity, heat, hot water and cooling to our customers under long-term sales agreements.
Use of Estimates	Use of Estimates The preparation of financial statements in conformity with accounting principles generally accepted in the United States of America requires 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
Income Taxes	Income Taxes The provisions for income taxes in the accompanying unaudited consolidated statements of operations differ from that which would be expected by applying the federal statutory tax rate primarily due to losses for which no benefit is recognized.

Revenue (Tables)

Revenue (Tables)	3 Months Ended
	Mar. 31, 2018
Revenue Recognition [Abstract]
Disaggregation of Revenue	The following table further disaggregates our revenue by major source by segment for the three months ended March 31, 2018 . Products and Services Energy Production Total Products $ 3,673,506 $ — $ 3,673,506 Installation services 2,405,655 — 2,405,655 Maintenance services 2,313,731 — 2,313,731 Energy production — 1,782,535 1,782,535 Total revenue $ 8,392,892 $ 1,782,535 $ 10,175,427

Income (Loss) Per Common Share

Income (Loss) Per Common Share (Tables)	3 Months Ended
	Mar. 31, 2018
Earnings Per Share [Abstract]
Schedule of Income (Loss) Per Common Share, Basic and Diluted	Basic and diluted income (loss) per share for the three months ended March 31, 2018 and 2017 , respectively, were as follows: Three months ended March 31, 2018 2017 Net income attributable to stockholders $ 20,759 $ 44,787 Weighted average shares outstanding - Basic 24,803,527 20,037,795 Basic income per share $ 0.00 $ 0.00 Weighted average shares outstanding - Diluted 24,881,185 20,317,142 Diluted income per share $ 0.00 $ 0.00 Anti-dilutive shares underlying stock options outstanding 77,658 — Anti-dilutive convertible debentures — 889,830

Acquisition of American DG En21

Acquisition of American DG Energy, Inc. (Tables)	3 Months Ended
	Mar. 31, 2018
Business Combinations [Abstract]
Pro Forma Information	The pro forma financial information as presented below is for informational purposes only and is not indicative of the results of operations that would have been achieved if the acquisition had taken place at the beginning of fiscal 2017. Three months ended March 31, 2017 Total revenues $ 8,276,124 Net income (loss) (460,935 ) Basic earnings (loss) per share (0.02 ) Diluted earnings (loss) per share (0.02 )

Property, Plant and Equipment (

Property, Plant and Equipment (Tables)	3 Months Ended
	Mar. 31, 2018
Property, Plant and Equipment [Abstract]
Summary of Property, Plant and Equipment	Property, plant and equipment at March 31, 2018 and December 31, 2017 consisted of the following: Estimated Useful March 31, 2018 December 31, 2017 Energy systems 1 - 15 years $ 12,548,796 $ 12,466,642 Machinery and equipment 5 - 7 years 1,284,203 1,215,951 Furniture and fixtures 5 years 104,317 205,320 Computer software 3 - 5 years 233,478 115,253 Leasehold improvements * 450,772 440,519 14,621,566 14,443,685 Less - accumulated depreciation and amortization (2,573,083 ) (2,177,974 ) $ 12,048,483 $ 12,265,711 * Lesser of estimated useful life of asset or lease term

Intangible Assets and Liabili23

Intangible Assets and Liabilities Other Than Goodwill (Tables)	3 Months Ended
	Mar. 31, 2018
Goodwill and Intangible Assets Disclosure [Abstract]
Schedule of Intangible Assets	As of March 31, 2018 and December 31, 2017 the Company had the following amounts related to intangible assets and liabilities other than goodwill: March 31, 2018 December 31, 2017 Intangible assets Cost Accumulated Amortization Total Cost Accumulated Amortization Total Product certifications $ 651,639 $ (298,874 ) $ 352,765 $ 605,704 $ (285,341 ) $ 320,363 Patents 844,309 (162,343 ) 681,966 808,323 (154,972 ) 653,351 Developed technology 240,000 (80,000 ) 160,000 240,000 (76,000 ) 164,000 Trademarks 20,540 — 20,540 19,540 — 19,540 In Process R&D 263,936 — 263,936 263,001 — 263,001 Favorable contract asset 1,561,739 (122,194 ) 1,439,545 1,561,739 (85,536 ) 1,476,203 $ 3,611,770 $ (663,411 ) $ 2,948,359 $ 3,498,307 $ (601,849 ) $ 2,896,458 Intangible liability Unfavorable contract liability $ 8,341,922 $ (876,972 ) $ 7,464,950 $ 8,341,922 $ (612,255 ) $ 7,729,667
Schedule of Future Amortization Expense	Aggregate future amortization over the next five years is estimated to be as follows: Year 1 $ (628,543 ) Year 2 (517,196 ) Year 3 (524,276 ) Year 4 (535,463 ) Year 5 (494,180 )

Stock-Based Compensation (Table

Stock-Based Compensation (Tables)	3 Months Ended
	Mar. 31, 2018
Tecogen
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Schedule of Stock Option Activity	Stock option activity for the three months ended March 31, 2018 was as follows: Common Stock Options Number of Options Exercise Share Weighted Price Weighted Life Aggregate Value Outstanding, December 31, 2017 1,061,552 $0.79-$18.15 $ 3.60 4.95 years $ 291,449 Granted 37,000 $2.30-$2.70 $2.43 Exercised (40,204 ) $1.20 $1.20 Canceled and forfeited (35,609 ) $2.60-$6.74 $4.31 Outstanding, March 31, 2018 1,022,739 $0.79-$18.15 $ 3.62 5.41 years $ 312,550 Exercisable, March 31, 2018 811,864 $ 3.54 $ 296,630 Vested and expected to vest, March 31, 2018 991,108 $ 3.61 $ 312,550

Fair Value Measurements (Tables

Fair Value Measurements (Tables)	3 Months Ended
	Mar. 31, 2018
Fair Value Disclosures [Abstract]
Schedule of Fair Value, Assets and Liabilities Measured on Recurring Basis	The following table presents the asset reported in the consolidated balance sheet measured at its fair value on a recurring basis as of March 31, 2018 by level within the fair value hierarchy. March 31, 2018 Quoted prices in active markets for identical assets Significant other observable inputs Significant unobservable inputs Total Level 1 Level 2 Level 3 Total gains (losses) Recurring fair value measurements Marketable equity securities EuroSite Power Inc. $ 334,570 $ — $ 334,570 $ — $ (184,998 ) Total recurring fair value measurements $ 334,570 $ — $ 334,570 $ — $ (184,998 )
Fair Value of Investments	The following table summarizes changes in level 2 assets which are comprised of marketable equity securities for the period: Fair value at acquisition on May 17, 2017 $ 519,568 Unrealized loss included in other comprehensive loss for the year ended December 31, 2017 (165,317 ) Fair value at December 31, 2017 354,251 Unrealized loss included in net income for the quarter ended March 31, 2018 (19,681 ) Fair value at March 31, 2018 $ 334,570

Related Party Transactions (Tab

Related Party Transactions (Tables)	3 Months Ended
	Mar. 31, 2018
Related Party Transactions [Abstract]
Schedule of Business Acquisition	The following represents the consideration for and the fair value of assets acquired and liabilities assumed recognized at the acquisition date: Cash $ 442,786 Accounts receivable 176,235 Unbilled revenue 232,540 Fixed assets 47,508 Intangible assets 29,607 Accounts payable (811,468 ) Deferred revenue (44,610 ) Cash payable $ 72,598

Segments (Tables)

Segments (Tables)	3 Months Ended
	Mar. 31, 2018
Segment Reporting [Abstract]
Schedule of Segment Reporting Information	The following table presents information by reportable segment for the three months ended March 31, 2018 and 2017 : Products and Services Energy Production Corporate, other and elimination (1) Total Three months ended March 31, 2018 Revenue - external customers $ 8,392,892 $ 1,782,535 $ — $ 10,175,427 Intersegment revenue 355,169 — (355,169 ) — Total revenue $ 8,748,061 $ 1,782,535 $ (355,169 ) $ 10,175,427 Gross profit $ 3,200,923 $ 636,880 $ — $ 3,837,803 Identifiable assets $ 20,828,118 $ 13,394,893 $ 18,922,000 $ 53,145,011 Three months ended March 31, 2017 Revenue - external customers $ 6,846,767 $ — $ — $ 6,846,767 Intersegment revenue — — — — Total revenue $ 6,846,767 $ — $ — $ 6,846,767 Gross profit $ 2,914,673 $ — $ — $ 2,914,673 Identifiable assets $ 17,524,410 $ — $ 6,898,911 $ 24,423,321 (1) Corporate, intersegment revenue, other and elimination includes various corporate assets.

Description of business and b28

Description of business and basis of presentation - Additional Information (Details)	May 18, 2017	Mar. 31, 2018USD ($)segment
Business Acquisition [Line Items]
Ownerhsip interest in American DG New York, LLC (percent)		51.00%
Number of business segments | segment		2
American DG Energy, Inc.
Business Acquisition [Line Items]
Ownership interest (percent)	100.00%
AOCI Attributable to Parent | Adjustments for New Accounting Pronouncement
Business Acquisition [Line Items]
Cumulative Effect of New Accounting Principle in Period of Adoption | $		$ (165,317)

Revenue - Disaggregation of Rev

Revenue - Disaggregation of Revenue (Details) - USD ($)	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Disaggregation of Revenue [Line Items]
Products	$ 3,673,506	$ 2,807,347
Installation services	2,405,655
Maintenance services	2,313,731
Energy production	1,782,535	0
Total revenues	10,175,427	$ 6,846,767
Products and Services
Disaggregation of Revenue [Line Items]
Products	3,673,506
Installation services	2,405,655
Maintenance services	2,313,731
Energy production	0
Total revenues	8,392,892
Energy Production
Disaggregation of Revenue [Line Items]
Products	0
Installation services	0
Maintenance services	0
Energy production	1,782,535
Total revenues	$ 1,782,535

Revenue - Additional Informatio

Revenue - Additional Information (Details) $ in Millions	3 Months Ended
	Mar. 31, 2018USD ($)
Revenue Recognition [Abstract]
Payment term on product sales	30 days
Payment term on installation services	30 days
Payment term on contractually determined milestones	30 days
Payment term on energy production contract invoices	30 days
Revenue recognized that was in unbilled revenue at beginning of period	$ 2.6
Revenue billed this period that had been recognized in previous periods	1.8
Deferred Revenue, Revenue Recognized	1.6
Cash payments received in advance of satisfying performance obligations	1.5
Remaining performance obligations	$ 1.8
Performance obligation revenue expected to be recognized over the next 24 months (percent)	99.00%
Performance obligation revenue to be recognized in first 12 months (percent)	77.00%
Performance obligation revenue to be recognized over the subsequent 12 months (percent)	22.00%

Income (Loss) Per Common Shar31

Income (Loss) Per Common Share - Schedule of Income (Loss) Per Common Share, Basic and Diluted (Details) - USD ($)	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Earnings Per Share [Abstract]
Net income attributable to stockholders	$ 20,759	$ 44,787
Weighted average shares outstanding - Basic (shares)	24,803,527	20,037,795
Basic income (loss) per share (in USD per share)	$ 0	$ 0
Weighted average shares outstanding - Diluted (shares)	24,881,185	20,317,142
Diluted income (loss) per share (in USD per share)	$ 0	$ 0
Stock Options
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities (shares)	77,658	0
Convertible Debenture
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities (shares)	0	889,830

Acquisition of American DG En32

Acquisition of American DG Energy, Inc. - Additional information (Details) - USD ($)	May 18, 2017	Mar. 31, 2018	Mar. 31, 2017
Business Acquisition [Line Items]
Revenue		$ 10,175,427	$ 6,846,767
Gross profit		3,837,803	$ 2,914,673
American DG Energy, Inc.
Business Acquisition [Line Items]
Ownership interest (percent)	100.00%
Gross profit		$ 636,880

Acquisition of American DG En33

Acquisition of American DG Energy, Inc. - Pro Forma Information (Details) - American DG Energy, Inc.	3 Months Ended
	Mar. 31, 2017USD ($)$ / shares
Business Acquisition [Line Items]
Total revenues | $	$ 8,276,124
Net income (loss) | $	$ (460,935)
Basic earnings (loss) per share (in USD per share) | $ / shares	$ (0.02)
Diluted earnings (loss) per share (in USD per share) | $ / shares	$ (0.02)

Property, Plant and Equipment -

Property, Plant and Equipment - Summary of Property and Equipment (Details) - USD ($)	3 Months Ended
	Mar. 31, 2018	Dec. 31, 2017
Property, Plant and Equipment [Line Items]
Property and equipment, gross	$ 14,621,566	$ 14,443,685
Less - accumulated depreciation and amortization	(2,573,083)	(2,177,974)
Property and equipment, net, before construction in progress	12,048,483	12,265,711
Energy systems
Property, Plant and Equipment [Line Items]
Property and equipment, gross	$ 12,548,796	12,466,642
Energy systems | Minimum
Property, Plant and Equipment [Line Items]
Useful life - years	1 year
Energy systems | Maximum
Property, Plant and Equipment [Line Items]
Useful life - years	15 years
Machinery and equipment
Property, Plant and Equipment [Line Items]
Property and equipment, gross	$ 1,284,203	1,215,951
Machinery and equipment | Minimum
Property, Plant and Equipment [Line Items]
Useful life - years	5 years
Machinery and equipment | Maximum
Property, Plant and Equipment [Line Items]
Useful life - years	7 years
Furniture and fixtures
Property, Plant and Equipment [Line Items]
Property and equipment, gross	$ 104,317	205,320
Useful life - years	5 years
Computer software
Property, Plant and Equipment [Line Items]
Property and equipment, gross	$ 233,478	115,253
Computer software | Minimum
Property, Plant and Equipment [Line Items]
Useful life - years	3 years
Computer software | Maximum
Property, Plant and Equipment [Line Items]
Useful life - years	5 years
Leasehold improvements
Property, Plant and Equipment [Line Items]
Property and equipment, gross	$ 450,772	$ 440,519

Property, Plant and Equipment35

Property, Plant and Equipment - Depreciation (Details) - USD ($)	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Property, Plant and Equipment [Abstract]
Depreciation and amortization expense	$ 402,336	$ 39,453

Intangible Assets and Liabili36

Intangible Assets and Liabilities Other Than Goodwill (Details) - USD ($)	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Goodwill and Intangible Assets Disclosure [Abstract]
Amortization of intangible assets	$ 24,903	$ 24,828
Net credit to cost of sales for amortization of contract related intangible assets and liabilities	$ 228,059	$ 0

Intangible Assets and Liabili37

Intangible Assets and Liabilities Other Than Goodwill -Amounts related to intangible assets (Details) - USD ($)	Mar. 31, 2018	Dec. 31, 2017
Finite-Lived Intangible Assets [Line Items]
Intangible assets	$ 3,611,770	$ 3,498,307
Less - accumulated amortization	(663,411)	(601,849)
Intangible assets, net	2,948,359	2,896,458
Unfavorable contract liability	8,341,922	8,341,922
Less - accumulated amortization	(876,972)	(612,255)
Unfavorable contract liability, net	7,464,950	7,729,667
Product Certifications
Finite-Lived Intangible Assets [Line Items]
Intangible assets	651,639	605,704
Less - accumulated amortization	(298,874)	(285,341)
Intangible assets, net	352,765	320,363
Patents
Finite-Lived Intangible Assets [Line Items]
Intangible assets	844,309	808,323
Less - accumulated amortization	(162,343)	(154,972)
Intangible assets, net	681,966	653,351
Developed Technology
Finite-Lived Intangible Assets [Line Items]
Intangible assets	240,000	240,000
Less - accumulated amortization	(80,000)	(76,000)
Intangible assets, net	160,000	164,000
Favorable contract asset
Finite-Lived Intangible Assets [Line Items]
Intangible assets	1,561,739	1,561,739
Less - accumulated amortization	(122,194)	(85,536)
Intangible assets, net	1,439,545	1,476,203
Trademarks
Finite-Lived Intangible Assets [Line Items]
Intangible assets	20,540	19,540
Less - accumulated amortization	0	0
Intangible assets, net	20,540	19,540
In Process R&D
Finite-Lived Intangible Assets [Line Items]
Intangible assets	263,936	263,001
Less - accumulated amortization	0	0
Intangible assets, net	$ 263,936	$ 263,001

Intangible Assets and Liabili38

Intangible Assets and Liabilities Other Than Goodwill - Future Amortization of Customer Contracts (Details) - Customer Contracts	Mar. 31, 2018USD ($)
Finite-Lived Intangible Assets [Line Items]
Year 1	$ (628,543)
Year 2	(517,196)
Year 3	(524,276)
Year 4	(535,463)
Year 5	$ (494,180)

Stock-Based Compensation - Stoc

Stock-Based Compensation - Stock-Based Compensation (Details) - USD ($)	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based Compensation	$ 40,416	$ 48,842
Tecogen | Amended Plan | Stock Options
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares of common stock reserved for future issuance	3,838,750
Number of shares remaining available for future issuance	2,122,356

Stock-Based Compensation - St40

Stock-Based Compensation - Stock Option Activity (Details) - Tecogen - USD ($)	3 Months Ended	12 Months Ended
	Mar. 31, 2018	Dec. 31, 2017
Stock Options Outstanding [Roll Forward]
Beginning (shares)	1,061,552
Granted (shares)	37,000
Exercised (shares)	(40,204)
Canceled and forfeited (shares)	(35,609)
Ending (shares)	1,022,739	1,061,552
Exercisable (shares)	811,864
Vested and expected to vest (shares)	991,108
Exercise Price Per Share [Abstract]
Exercise Price Per Share, Outstanding, Minimum (per share)	$ 0.79	$ 0.79
Exercise Price Per Share, Outstanding, Maximum (dollars per share)	18.15	18.15
Exercise Price Per Share, Exercised (dollars per share)	1.20
Weighted Average Exercise Price [Roll Forward]
Beginning (usd per share)	3.60
Granted (usd per share)	2.43
Exercised (usd per share)	1.20
Canceled and forfeited (usd per share)	4.31
Ending (usd per share)	3.62	$ 3.60
Exercisable (usd per share)	3.54
Vested and expected to vest (usd per share)	$ 3.61
Weighted Average Remaining Life	5 years 4 months 28 days	4 years 11 months 12 days
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Additional Disclosures [Abstract]
Outstanding, Aggregate Intrinsic Value	$ 312,550	$ 291,449
Exercisable, Aggregate Intrinsic Value	296,630
Vested and expected to vest, Aggregate Intrinsic Value	$ 312,550
Minimum
Exercise Price Per Share [Abstract]
Exercise Price Per Share, Granted (dollars per share)	$ 2.30
Exercise Price, Assumed in Merger (dollars per share)	3.15
Exercise Price, Canceled and Forfeited (dollars per share)	2.60
Maximum
Exercise Price Per Share [Abstract]
Exercise Price Per Share, Granted (dollars per share)	2.70
Exercise Price, Assumed in Merger (dollars per share)	30.33
Exercise Price, Canceled and Forfeited (dollars per share)	$ 6.74

Fair Value Measurements - Fair

Fair Value Measurements - Fair Value on a Recurring Basis (Details) - Fair Value, Measurements, Recurring - USD ($)	3 Months Ended	12 Months Ended
	Mar. 31, 2018	Dec. 31, 2017	May 18, 2017
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total gains (losses)	$ (184,998)
Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total recurring fair value measurements	0
Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total recurring fair value measurements	334,570
Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total recurring fair value measurements	0
Estimate of Fair Value Measurement
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total recurring fair value measurements	334,570
Eurosite Power Inc
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total gains (losses)	(184,998)	$ (165,317)
Eurosite Power Inc | Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale equity securities	0
Eurosite Power Inc | Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale equity securities	334,570	$ 354,251	$ 519,568
Eurosite Power Inc | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale equity securities	0
Eurosite Power Inc | Estimate of Fair Value Measurement
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale equity securities	$ 334,570

Fair Value Measurements - Chang

Fair Value Measurements - Change in Level 2 Assets (Details) - USD ($)	3 Months Ended	12 Months Ended
	Mar. 31, 2018	Dec. 31, 2017
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Unrealized loss included in net income for the quarter ended March 31, 2018	$ (19,681)
Fair Value, Measurements, Recurring
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Unrealized loss included in other comprehensive loss for the year ended December 31, 2017	(184,998)
Eurosite Power Inc | Fair Value, Measurements, Recurring
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Unrealized loss included in other comprehensive loss for the year ended December 31, 2017	(184,998)	$ (165,317)
Eurosite Power Inc | Fair Value, Measurements, Recurring | Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value, beginning	354,251
Fair value, ending	$ 334,570	$ 354,251

Commitments and Contingencies (

Commitments and Contingencies (Details)	Mar. 31, 2018USD ($)
Commitments and Contingencies Disclosure [Abstract]
Guarantee of obligations of Eurosite Power, Inc.	$ 279,500
Guarantee liability	$ 10,000

Related party transactions (Det

Related party transactions (Details) - USD ($)	May 04, 2018	Mar. 27, 2018	Jan. 31, 2017	Mar. 31, 2018	Mar. 31, 2017	Dec. 31, 2017	May 19, 2016
Schedule of Equity Method Investments [Line Items]
Purchase of the remaining assets of Ultratek				$ 145,326	$ 73,330
TTcogen, LLC
Schedule of Equity Method Investments [Line Items]
Equity interest in joint venture (percent)							50.00%
Tedom a.s.
Schedule of Equity Method Investments [Line Items]
Equity interest in joint venture (percent)							50.00%
Tedom USA
Schedule of Equity Method Investments [Line Items]
Equity interest in joint venture (percent)							50.00%
Initial payment to acquire Tedom USA's membership interest in TTcogen		$ 1
Payment to acquire Tedom USA'a initial investment in TTcogen, minus certain adjustments		72,597
Payment for acquisition of assets		$ 72,598
American DG Energy
Schedule of Equity Method Investments [Line Items]
Equipment purchase			$ 985,000
Co-Chief Executive Officer
Schedule of Equity Method Investments [Line Items]
Loan from related party				$ 850,000
Notes Payable | Co-Chief Executive Officer
Schedule of Equity Method Investments [Line Items]
Stated interest rate (percent)				6.00%
Subsequent Event | Co-Chief Executive Officer
Schedule of Equity Method Investments [Line Items]
Repayment of loan	$ 919,590
Ultratek | American DG Energy
Schedule of Equity Method Investments [Line Items]
Return of investment in Ultratek						$ 2,000,000
Purchase of the remaining assets of Ultratek						$ 400,000

Related party transactions - As

Related party transactions - Assets Acquired and Liabilities Assumed (Details) - Tedom USA's Membership Interest in TTcogen	Mar. 27, 2018USD ($)
Business Acquisition [Line Items]
Cash	$ 442,786
Accounts receivable	176,235
Unbilled revenue	232,540
Fixed assets	47,508
Intangible assets	29,607
Accounts payable	(811,468)
Deferred revenue	(44,610)
Cash payable	$ 72,598

Segments (Details)

Segments (Details)	3 Months Ended
	Mar. 31, 2018USD ($)segment	Mar. 31, 2017USD ($)
Segment Reporting Information [Line Items]
Number of operating divisions | segment	2
Revenue	$ 10,175,427	$ 6,846,767
Gross profit	3,837,803	2,914,673
Identifiable Assets	53,145,011	24,423,321
Products and Services
Segment Reporting Information [Line Items]
Revenue	8,748,061	6,846,767
Gross profit	3,200,923	2,914,673
Identifiable Assets	20,828,118	17,524,410
Energy Production
Segment Reporting Information [Line Items]
Revenue	1,782,535	0
Gross profit	636,880	0
Identifiable Assets	13,394,893	0
Corporate, other and elimination
Segment Reporting Information [Line Items]
Revenue	(355,169)	0
Gross profit	0	0
Identifiable Assets	18,922,000	6,898,911
Operating Segments
Segment Reporting Information [Line Items]
Revenue	10,175,427	6,846,767
Operating Segments | Products and Services
Segment Reporting Information [Line Items]
Revenue	8,392,892	6,846,767
Operating Segments | Energy Production
Segment Reporting Information [Line Items]
Revenue	1,782,535	0
Operating Segments | Corporate, other and elimination
Segment Reporting Information [Line Items]
Revenue	0	0
Intersegment Eliminations
Segment Reporting Information [Line Items]
Revenue	0	0
Intersegment Eliminations | Products and Services
Segment Reporting Information [Line Items]
Revenue	355,169	0
Intersegment Eliminations | Energy Production
Segment Reporting Information [Line Items]
Revenue	0	0
Intersegment Eliminations | Corporate, other and elimination
Segment Reporting Information [Line Items]
Revenue	$ (355,169)	$ 0

Subsequent Events (Details)

Subsequent Events (Details) - USD ($)	May 04, 2018	Mar. 31, 2018	May 18, 2017
Webster Business Credit Corporation | Subsequent Event
Subsequent Event [Line Items]
Line of credit limit	$ 10,000,000
One Month LIBOR | Webster Business Credit Corporation | Subsequent Event
Subsequent Event [Line Items]
Basis spread on variable rate (percent)	3.00%
Lender's Base Rate | Webster Business Credit Corporation | Subsequent Event
Subsequent Event [Line Items]
Basis spread on variable rate (percent)	1.50%
Lender's Base Rate - Federal Funds Rate | Webster Business Credit Corporation | Subsequent Event
Subsequent Event [Line Items]
Basis spread on variable rate (percent)	0.50%
Lender's Base Rate - One Month LIBOR | Webster Business Credit Corporation | Subsequent Event
Subsequent Event [Line Items]
Basis spread on variable rate (percent)	2.75%
Co-Chief Executive Officer
Subsequent Event [Line Items]
Loan from related party		$ 850,000
Co-Chief Executive Officer | Subsequent Event
Subsequent Event [Line Items]
Repayment of loan	$ 919,590
Co-Chief Executive Officer | John N. Hatsopoulos
Subsequent Event [Line Items]
Line of credit limit			$ 3,000,000
Notes Payable | Co-Chief Executive Officer
Subsequent Event [Line Items]
Stated interest rate (percent)		6.00%