Annual report pursuant to Section 13 and 15(d)

Stockholders' equity - Weighted Average Assumptions (Details)

v2.4.1.9
Stockholders' equity - Weighted Average Assumptions (Details) (USD $)
12 Months Ended
Dec. 31, 2014
Dec. 31, 2013
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]    
Granted, Exercise Price Lower Range Limit (usd per share) 4.50tcgn_ShareBasedCompensationSharesAuthorizedUnderStockOptionPlansGrantedExercisePriceRangeLowerRangeLimit  
Granted, Exercise Price Upper Range Limit (usd per share) 5.39tcgn_ShareBasedCompensationSharesAuthorizedUnderStockOptionPlansGrantedExercisePriceRangeUpperRangeLimit  
Tecogen    
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]    
Canceled and Forfeited, Exercise Price Lower Range Limit (usd per share) 0.12tcgn_ShareBasedCompensationSharesAuthorizedUnderStockOptionPlansCancelledAndForfeitedExercisePriceRangeLowerRangeLimit
/ dei_LegalEntityAxis
= us-gaap_ParentCompanyMember
 
Canceled and Forfeited, Exercise Price Upper Range Limit (usd per share) 4.50tcgn_ShareBasedCompensationSharesAuthorizedUnderStockOptionPlansCancelledAndForfeitedExercisePriceRangeUpperRangeLimit
/ dei_LegalEntityAxis
= us-gaap_ParentCompanyMember
 
Share-based Compensation, Shares Authorized Under Stock Option Plans, Exercised, Exercise Price Range, Lower Range Limit 1.20tcgn_SharebasedCompensationSharesAuthorizedUnderStockOptionPlansExercisedExercisePriceRangeLowerRangeLimit
/ dei_LegalEntityAxis
= us-gaap_ParentCompanyMember
 
Share-based Compensation, Shares Authorized Under Stock Option Plans, Exercised, Exercise Price Range, Upper Range Limit 2.60tcgn_SharebasedCompensationSharesAuthorizedUnderStockOptionPlansExercisedExercisePriceRangeUpperRangeLimit
/ dei_LegalEntityAxis
= us-gaap_ParentCompanyMember
 
Tecogen | Stock Options    
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]    
Expected life 6 years 3 months 0 days 5 years 7 months 18 days
Risk-free interest rate 1.51%us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsRiskFreeInterestRate
/ us-gaap_AwardTypeAxis
= us-gaap_EmployeeStockOptionMember
/ dei_LegalEntityAxis
= us-gaap_ParentCompanyMember
1.34%us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsRiskFreeInterestRate
/ us-gaap_AwardTypeAxis
= us-gaap_EmployeeStockOptionMember
/ dei_LegalEntityAxis
= us-gaap_ParentCompanyMember
Expected volatility, Minimum 22.70%us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsExpectedVolatilityRateMinimum
/ us-gaap_AwardTypeAxis
= us-gaap_EmployeeStockOptionMember
/ dei_LegalEntityAxis
= us-gaap_ParentCompanyMember
26.50%us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsExpectedVolatilityRateMinimum
/ us-gaap_AwardTypeAxis
= us-gaap_EmployeeStockOptionMember
/ dei_LegalEntityAxis
= us-gaap_ParentCompanyMember
Expected volatility, Maximum 32.30%us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsExpectedVolatilityRateMaximum
/ us-gaap_AwardTypeAxis
= us-gaap_EmployeeStockOptionMember
/ dei_LegalEntityAxis
= us-gaap_ParentCompanyMember
36.10%us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsExpectedVolatilityRateMaximum
/ us-gaap_AwardTypeAxis
= us-gaap_EmployeeStockOptionMember
/ dei_LegalEntityAxis
= us-gaap_ParentCompanyMember
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%us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsRiskFreeInterestRate
/ us-gaap_AwardTypeAxis
= us-gaap_EmployeeStockOptionMember
/ dei_LegalEntityAxis
= tcgn_IloisMember
 
Expected volatility 35.20%us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsExpectedVolatilityRate
/ us-gaap_AwardTypeAxis
= us-gaap_EmployeeStockOptionMember
/ dei_LegalEntityAxis
= tcgn_IloisMember