| Cover | 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 |
