Annual report [Section 13 and 15(d), not S-K Item 405]

Stockholders' equity - Stock Option Activity (Details)

v3.25.1
Stockholders' equity - Stock Option Activity (Details) - USD ($)
12 Months Ended
Dec. 31, 2024
Dec. 31, 2023
Exercise Price Per Share [Abstract]    
Outstanding, Exercise Price Lower Range Limit (usd per share) $ 0.71 $ 0.71
Outstanding, Exercise Price Upper Range Limit (usd per share) 3.93  
Granted, Exercise Price Lower Range Limit (usd per share) 0.77  
Granted, Exercise Price Upper Range Limit (usd per share)   $ 10.33
Exercised, Exercise Price Per Share (usd per share) 0.71  
Canceled and Forfeited, Exercise Price Lower Range Limit (usd per share) 0.71  
Canceled and Forfeited, Exercise Price Upper Range Limit (usd per share) $ 10.33  
Tecogen    
Stock Options Outstanding [Roll Forward]    
Beginning (shares) 3,638,122  
Granted (shares) 125,000  
Canceled and forfeited (shares) (910,160)  
Ending (shares) 2,752,962 3,638,122
Exercisable (shares) 1,839,212  
Vested and expected to vest (shares) 2,615,900  
Weighted Average Exercise Price [Roll Forward]    
Beginning (usd per share) $ 1.49  
Granted (usd per share) 0.77  
Exercised (usd per share) 0.71  
Canceled and forfeited (usd per share) 2.54  
Ending (usd per share) 1.14 $ 1.49
Vested and expected to vest (usd per share) 1.15  
Exercisable (usd per share) $ 1.25  
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Additional Disclosures [Abstract]    
Outstanding, Aggregate Intrinsic Value $ 1,348,684 $ 127,811
Exercised, Aggregate Intrinsic Value 75,500  
Exercisable, Aggregate Intrinsic Value 838,184  
Vested and expected to vest, Aggregate Intrinsic Value $ 1,272,109  
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 8 months 12 days 6 years 8 months 12 days