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

Stockholders' equity - Stock-Based Compensation (Details)

v3.25.1
Stockholders' equity - Stock-Based Compensation (Details)
 12 Months Ended
Mar. 01, 2022
shares
Dec. 31, 2024
USD ($)
option
company
$ / shares
shares
Dec. 31, 2023
USD ($)
$ / shares
shares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]      
Options granted, exercise price range, lower limit (usd per share) | $ / shares   $ 0.77  
Options granted, exercise price range, upper limit (usd per share) | $ / shares     $ 10.33
Historical forfeiture rate (percent)   15.00%  
Number of publicly traded companies used in expected volatility rate calculation | company   4  
Tecogen      
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]      
Options granted   125,000  
Exercise of stock options (in shares)   (100,000) 0
Number of options exercised in period | option   1  
Recognized stock-based compensation | $   $ 172,987 $ 250,394
Tax benefit related to stock-based compensation expense | $   0 0
Compensation cost related to unvested restricted stock awards and stock option awards not yet recognized | $   $ 278,461 $ 451,298
Compensation cost not yet recognized, weighted average period of recognition   2 years 3 months 18 days  
Tecogen | Director      
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]      
Options granted   125,000 575,000
Award expiration period   10 years 10 years
Exercise price per share, granted (usd per share) | $ / shares   $ 0.77  
Options granted, exercise price range, lower limit (usd per share) | $ / shares     $ 0.88
Options granted, exercise price range, upper limit (usd per share) | $ / shares     $ 1.10
Award vesting period   4 years  
Fair value of options issued | $   $ 44,750 $ 244,625
Weighted-average grant date fair value of options granted | $ / shares   $ 0.36 $ 0.43
Tecogen | Director | Minimum      
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]      
Award vesting period     2 years
Tecogen | Director | Maximum      
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]      
Award vesting period     4 years
Tecogen | Amended Plan      
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]      
Options granted   0 0
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   1,108,168 243,818
Tecogen | 2022 Stock Incentive Plan | Stock Options      
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]      
Shares of common stock reserved for future issuance 3,800,000 2,950,000  
Award expiration period 10 years