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Summary of Significant Accounting Policies - Accounts Receivable (Details)	12 Months Ended
	Dec. 31, 2020
Accounting Policies [Abstract]
Payment terms	30 days

X

- Definition

Contract With Customer, Payment Terms

+ References

No definition available.

+ Details

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Namespace Prefix:	efoi_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

X

- References

No definition available.

+ Details

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration