Annual report pursuant to Section 13 and 15(d)

Document and Entity Information

v3.21.1
Document and Entity Information - USD ($)
$ / shares in Units, $ in Millions
 12 Months Ended
Mar. 31, 2021
Jun. 10, 2021
Sep. 30, 2020
Document Information [Line Items]      
Entity Central Index Key 0001009759    
Document Type 10-K    
Document Period End Date Mar. 31, 2021    
Document Annual Report true    
Document Transition Report false    
Entity File Number 001-15957    
Entity Registrant Name CAPSTONE GREEN ENERGY CORPORATION    
Entity Incorporation, State or Country Code DE    
Entity Tax Identification Number 95-4180883    
Entity Address, Address Line One 16640 Stagg Street    
Entity Address, City or Town Van Nuys    
Entity Address, State or Province CA    
Entity Address, Postal Zip Code 91406    
City Area Code 818    
Local Phone Number 734-5300    
Entity Listing, Par Value Per Share $ 0.001    
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 Small Business true    
Entity Emerging Growth Company false    
ICFR Auditor Attestation Flag false    
Entity Shell Company false    
Entity Public Float     $ 51.7
Entity Common Stock, Shares Outstanding   12,926,026  
Current Fiscal Year End Date --03-31    
Document Fiscal Year Focus 2021    
Document Fiscal Period Focus FY    
Amendment Flag false    
Common Stock      
Document Information [Line Items]      
Title of 12(b) Security Common Stock, par value $.001 per share    
Trading Symbol CGRN    
Security Exchange Name NASDAQ    
Series B Junior Participating Preferred Stock      
Document Information [Line Items]      
Title of 12(b) Security Series B Junior Participating Preferred Stock Purchase Rights