Annual report pursuant to Section 13 and 15(d)

Stockholders' equity - Stock Option Activity (Details)

v3.6.0.2
Stockholders' equity - Stock Option Activity (Details) - USD ($)
12 Months Ended
Dec. 31, 2016
Dec. 31, 2015
Exercise Price Per Share [Abstract]    
Granted, Exercise Price Lower Range Limit (usd per share) $ 0.79  
Granted, Exercise Price Upper Range Limit (usd per share) $ 4.27  
Tecogen    
Stock Options Outstanding [Roll Forward]    
Beginning (shares) 1,268,200  
Granted (shares) 207,701 165,000
Exercised (shares) (157,458)  
Canceled and forfeited (shares) (200,525)  
Ending (shares) 1,117,918 1,268,200
Exercisable (shares) 835,293  
Vested and expected to vest (shares) 1,075,524  
Weighted Average Exercise Price [Roll Forward]    
Beginning (usd per share) $ 3.06  
Granted (usd per share) 3.52  
Exercised (usd per share) 2.51  
Canceled and forfeited (usd per share) 3.73  
Ending (usd per share) 3.10 $ 3.06
Exercisable (usd per share) 2.64  
Vested and expected to vest (usd per share) $ 3.05  
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Additional Disclosures [Abstract]    
Outstanding, Aggregate Intrinsic Value $ 1,415,150 $ 985,578
Exercisable, Aggregate Intrinsic Value 1,395,638  
Vested and expected to vest, Aggregate Intrinsic Value $ 1,415,150  
Exercise Price Per Share [Abstract]    
Outstanding, Exercise Price Lower Range Limit (usd per share) $ 0.79 $ 1.2
Outstanding, Exercise Price Upper Range Limit (usd per share) 5.39 5.39
Granted, Exercise Price Lower Range Limit (usd per share) 0.79 3.39
Granted, Exercise Price Upper Range Limit (usd per share) 4.27 $ 4.05
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) 3.39  
Canceled and Forfeited, Exercise Price Upper Range Limit (usd per share) $ 4.96  
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 5 years 6 years 5 days