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Note 7 - Debt (Details) - Summary of Debt Components (Unsecured Promissory Note - Quercus Trust [Member], USD $)
In Thousands, unless otherwise specified
Mar. 31, 2015
Dec. 31, 2014
Unsecured Promissory Note - Quercus Trust [Member]
    
Debt Instrument [Line Items]    
Unsecured promissory note - Quercus Trust (1) $ 70us-gaap_DebtInstrumentCarryingAmount
/ us-gaap_LongtermDebtTypeAxis
= efoi_UnsecuredPromissoryNoteQuercusTrustMember		 [1] $ 70us-gaap_DebtInstrumentCarryingAmount
/ us-gaap_LongtermDebtTypeAxis
= efoi_UnsecuredPromissoryNoteQuercusTrustMember		 [1]
Long-term debt $ 70us-gaap_LongTermDebt
/ us-gaap_LongtermDebtTypeAxis
= efoi_UnsecuredPromissoryNoteQuercusTrustMember		 $ 70us-gaap_LongTermDebt
/ us-gaap_LongtermDebtTypeAxis
= efoi_UnsecuredPromissoryNoteQuercusTrustMember
[1] Note matures on June 1, 2109 and bears interest at 1 percent.