Annual report pursuant to Section 13 and 15(d)

Stockholders' equity - Stock-Based Compensation (Details)

v3.22.0.1
Stockholders' equity - Stock-Based Compensation (Details) - USD ($)
12 Months Ended
Dec. 31, 2021
Dec. 31, 2020
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]    
Options granted, exercise price range, lower limit (usd per share) $ 1.75  
Historical forfeiture rate (percent) 15.00%  
Tecogen    
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]    
Options granted 258,000 1,440,000
Options granted, exercise price range, lower limit (usd per share) $ 1.75 $ 0.71
Options granted, exercise price range, upper limit (usd per share)   $ 0.78
Award vesting period 4 years  
Award expiration period 10 years  
Fair value of options issued $ 166,474 $ 404,460
Weighted-average grant date fair value of options granted $ 0.65 $ 0.28
Exercised (shares) 0 1,000
Recognized stock-based compensation $ 202,431 $ 163,464
Compensation cost related to unvested restricted stock awards and stock option awards not yet recognized $ 470,063 $ 340,503
Compensation cost not yet recognized, weighted average period of recognition 1 year 11 months 26 days  
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 764,768 1,022,768
Remaining Options | Tecogen | Stock Options    
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]    
Award vesting period   4 years
Award expiration period   10 years