Annual report pursuant to Section 13 and 15(d)

Stockholders' equity - Stock Option Activity (Details)

v3.3.1.900
Stockholders' equity - Stock Option Activity (Details) - USD ($)
 12 Months Ended
Dec. 31, 2015
Dec. 31, 2014
Exercise Price Per Share [Abstract]    
Granted, Exercise Price Lower Range Limit (usd per share) $ 3.39  
Granted, Exercise Price Upper Range Limit (usd per share) $ 4.05  
Tecogen    
Stock Options Outstanding [Roll Forward]    
Beginning (shares) 1,356,325  
Granted (shares) 165,000 318,325
Exercised (shares) (222,375)  
Canceled and forfeited (shares) (18,250)  
Expired (shares) (12,500)  
Ending (shares) 1,268,200 1,356,325
Exercisable (shares) 841,650  
Vested and expected to vest (shares) 1,268,200  
Weighted Average Exercise Price [Roll Forward]    
Beginning (usd per share) $ 2.77  
Granted (usd per share) 3.43  
Exercised (usd per share) 1.62  
Canceled and forfeited (usd per share) 3.52  
Expired (usd per share) 1.20  
Ending (usd per share) 3.06 $ 2.77
Exercisable (usd per share) 2.48  
Vested and expected to vest (usd per share) $ 3.06  
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Additional Disclosures [Abstract]    
Outstanding, Aggregate Intrinsic Value $ 985,578 $ 3,618,935
Exercisable, Aggregate Intrinsic Value 978,640  
Vested and expected to vest, Aggregate Intrinsic Value $ 985,578  
Exercise Price Per Share [Abstract]    
Outstanding, Exercise Price Lower Range Limit (usd per share) $ 1.20 $ 1.2
Outstanding, Exercise Price Upper Range Limit (usd per share) 5.39 5.39
Granted, Exercise Price Lower Range Limit (usd per share) 3.39 4.50
Granted, Exercise Price Upper Range Limit (usd per share) 4.05 $ 5.39
Exercised, Exercise Price Range, Lower Range Limit (usd per share) 1.20  
Exercised, Exercise Price Range, Upper Range Limit (usd per share) 2.60  
Canceled and Forfeited, Exercise Price Lower Range Limit (usd per share) 2.60  
Canceled and Forfeited, Exercise Price Upper Range Limit (usd per share) 4.50  
Expired, Exercise Price (usd per share) $ 1.20  
Ilois    
Stock Options Outstanding [Roll Forward]    
Beginning (shares) 675,000  
Granted (shares) 0  
Exercised (shares) 0  
Canceled and forfeited (shares) (25,000)  
Expired (shares) 0  
Ending (shares) 650,000 675,000
Exercisable (shares) 262,500  
Vested and expected to vest (shares) 650,000  
Weighted Average Exercise Price [Roll Forward]    
Beginning (usd per share) $ 0.32  
Granted (usd per share) 0.00  
Exercised (usd per share) 0.00  
Canceled and forfeited (usd per share) 0.50  
Expired (usd per share) 0.00  
Ending (usd per share) 0.32 $ 0.32
Exercisable (usd per share) 0.50  
Vested and expected to vest (usd per share) $ 0.32  
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Additional Disclosures [Abstract]    
Outstanding, Weighted Average Remaining Life 5 years 14 days 6 years 6 months 21 days
Outstanding, Aggregate Intrinsic Value $ 120,000 $ 120,000
Exercisable, Aggregate Intrinsic Value 0  
Vested and expected to vest, Aggregate Intrinsic Value $ 120,000  
Exercise Price Per Share [Abstract]    
Outstanding, Exercise Price Lower Range Limit (usd per share) $ 0.10 $ 0.10
Outstanding, Exercise Price Upper Range Limit (usd per share) 0.50 $ 0.50
Granted, Exercise Price (usd per share) 0.00  
Exercised, Exercise Price (usd per share) 0.00  
Canceled and Forfeited, Exercise Price (usd per share) 0.50  
Expired, Exercise Price (usd per share) $ 0.00  
Stock Options | Tecogen    
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Additional Disclosures [Abstract]    
Outstanding, Weighted Average Remaining Life 6 years 5 days 5 years 1 month 15 days