Annual report pursuant to Section 13 and 15(d)

Stockholders' equity - Stock Option Activity (Details)

v3.20.4
Stockholders' equity - Stock Option Activity (Details) - USD ($)
12 Months Ended
Dec. 31, 2020
Dec. 31, 2019
Exercise Price Per Share [Abstract]    
Granted, Exercise Price Lower Range Limit (usd per share) $ 0.71  
Granted, Exercise Price Upper Range Limit (usd per share) $ 0.78  
Tecogen    
Stock Options Outstanding [Roll Forward]    
Beginning (shares) 1,352,874  
Granted (shares) 1,440,000 88,500
Exercised (shares) (1,000) (24,515)
Canceled and forfeited (shares) (295,632)  
Ending (shares) 2,496,242 1,352,874
Exercisable (shares) 828,825  
Vested and expected to vest (shares) 2,246,565  
Weighted Average Exercise Price [Roll Forward]    
Beginning (usd per share) $ 3.57  
Granted (usd per share) 0.72  
Exercised (usd per share) 1.20  
Canceled and forfeited (usd per share) 3.42  
Ending (usd per share) $ 1.94 $ 3.57
Exercised, aggregate intrinsic value $ 20 $ 19,794
Exercisable (usd per share) $ 3.61  
Vested and expected to vest (usd per share) $ 2.04  
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Additional Disclosures [Abstract]    
Outstanding, Aggregate Intrinsic Value $ 731,744 $ 95,381
Exercisable, Aggregate Intrinsic Value 11,044  
Vested and expected to vest, Aggregate Intrinsic Value $ 623,639  
Exercise Price Per Share [Abstract]    
Outstanding, Exercise Price Lower Range Limit (usd per share) $ 0.71 $ 0.79
Outstanding, Exercise Price Upper Range Limit (usd per share) 10.33 10.33
Granted, Exercise Price Lower Range Limit (usd per share) 0.71 3.40
Granted, Exercise Price Upper Range Limit (usd per share) 0.78 $ 3.80
Exercised, Exercise Price per Share (usd per share) 1.20  
Canceled and Forfeited, Exercise Price Lower Range Limit (usd per share) 1.20  
Canceled and Forfeited, Exercise Price Upper Range Limit (usd per share) $ 5.65  
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 7 years 4 months 13 days 5 years 3 months 18 days