Annual report pursuant to Section 13 and 15(d)

Stockholders' equity - Weighted Average Assumptions (Details)

v3.3.1.900
Stockholders' equity - Weighted Average Assumptions (Details)
12 Months Ended
Dec. 31, 2015
Dec. 31, 2014
Tecogen    
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]    
Compensation cost not yet recognized, weighted average period of recognition 2 years 11 months 15 days  
Tecogen | Stock Options    
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]    
Expected life 6 years 3 months 6 years 3 months
Risk-free interest rate   1.51%
Risk-free interest rate, Minimum 1.63%  
Risk-free interest rate, Maximum 1.67%  
Expected volatility, Minimum 32.40% 22.70%
Expected volatility, Maximum 32.60% 32.30%
Ilois    
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]    
Compensation cost not yet recognized, weighted average period of recognition 4 months 11 days  
Ilois | Stock Options    
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]    
Expected life 6 years 3 months  
Risk-free interest rate 1.65%  
Expected volatility 35.20%