Annual report pursuant to Section 13 and 15(d)


Cover - USD ($)
12 Months Ended
Dec. 31, 2020
Mar. 09, 2021
Jun. 30, 2020
Cover [Abstract]      
Document Type 10-K    
Document Annual Report true    
Document Period End Date Dec. 31, 2020    
Current Fiscal Year End Date --12-31    
Document Transition Report false    
Entity File Number 001-36103    
Entity Registrant Name TECOGEN INC.    
Entity Incorporation, State or Country Code DE    
Entity Tax Identification Number 04-3536131    
Entity Address, Address Line One 45 First Avenue    
Entity Address, City or Town Waltham    
Entity Address, State or Province MA    
Entity Address, Postal Zip Code 02451    
City Area Code 781    
Local Phone Number 466-6400    
Entity Well-known Seasoned Issuer No    
Entity Voluntary Filers No    
Entity Current Reporting Status Yes    
Entity Interactive Data Current Yes    
Entity Filer Category Non-accelerated Filer    
Entity Emerging Growth Company false    
Entity Small Business true    
ICFR Auditor Attestation Flag false    
Entity Shell Company false    
Entity Public Float     $ 25,611,519
Entity Common Stock, Shares Outstanding   24,850,261  
Entity Central Index Key 0001537435    
Document Fiscal Year Focus 2020    
Document Fiscal Period Focus FY    
Amendment Flag false