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Cover
 12 Months Ended
Mar. 25, 2021
Dec. 31, 2020
Cover [Abstract]    
Document Type 8-K  
Entity Registrant Name   ENERGY FOCUS, INC/DE
Entity Incorporation, State or Country Code DE  
Entity File Number 001-36583  
Entity Tax Identification Number 94-3021850  
Entity Address, Address Line One 32000 Aurora Road Suite B  
Entity Address, State or Province OH  
Entity Address, Postal Zip Code 44139  
City Area Code 440  
Local Phone Number 715-1300  
Written Communications false  
Soliciting Material false  
Pre-commencement Tender Offer false  
Pre-commencement Issuer Tender Offer false  
Title of 12(b) Security Common Stock, par value $0.0001 per share  
Trading Symbol EFOI  
Security Exchange Name NASDAQ  
Entity Emerging Growth Company false  
Entity Central Index Key 0000924168  
Amendment Flag false  
Entity Addresses [Line Items]    
Entity Address, Address Line One 32000 Aurora Road Suite B  
Entity Address, Postal Zip Code 44139  
Entity Address, State or Province OH  
Entity Address, City or Town Solon,  
Document Period End Date Mar. 25, 2021  
Document Information [Line Items]    
Document Period End Date Mar. 25, 2021