Payments For Clearing Fees

No definition available.

Name:	efoi_PaymentsForClearingFees
Namespace Prefix:	efoi_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

Payments For Placement Agent Commissions

+ References

No definition available.

+ Details

Name:	efoi_PaymentsForPlacementAgentCommissions
Namespace Prefix:	efoi_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

Payments Related To Expenses For Registered Direct Offering And Concurrent Private Placement

+ References

No definition available.

+ Details

Name:	efoi_PaymentsRelatedToExpensesForRegisteredDirectOfferingAndConcurrentPrivatePlacement
Namespace Prefix:	efoi_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

Proceeds from the Issuance of Common Stock and Warrants, Net of Issuance Costs

+ References

No definition available.

+ Details

Name:	efoi_ProceedsFromTheIssuanceOfCommonStockAndWarrantsNetOfIssuanceCosts
Namespace Prefix:	efoi_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

The cash outflow for cost incurred directly with the issuance of an equity security.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 15
-URI http://asc.fasb.org/extlink&oid=123570139&loc=d3e3291-108585

+ Details

Name:	us-gaap_PaymentsOfStockIssuanceCosts
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

The number of shares issued or sold by the subsidiary or equity method investee per stock transaction.

+ References

No definition available.

+ Details

Name:	us-gaap_SaleOfStockNumberOfSharesIssuedInTransaction
Namespace Prefix:	us-gaap_
Data Type:	xbrli:sharesItemType
Balance Type:	na
Period Type:	duration

- Definition

Per share amount received by subsidiary or equity investee for each share of common stock issued or sold in the stock transaction.

+ References

No definition available.

+ Details

Name:	us-gaap_SaleOfStockPricePerShare
Namespace Prefix:	us-gaap_
Data Type:	dtr-types:perShareItemType
Balance Type:	na
Period Type:	instant

- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References

No definition available.

+ Details

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

- Details

Name:	us-gaap_SubsidiarySaleOfStockAxis=efoi_InstitutionalInvestorMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_SubsidiarySaleOfStockAxis=us-gaap_PrivatePlacementMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Stockholders' Equity - June 2021 Equity Offering (Details) - USD ($) $ / shares in Units, $ in Thousands	1 Months Ended		3 Months Ended		9 Months Ended		12 Months Ended
	Jun. 30, 2021	Jan. 31, 2020	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020	Dec. 31, 2020
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Amount paid for clearing fees	$ 19	$ 231
Payments of Stock Issuance Costs			$ (1)	$ 0	$ (470)	$ (474)	$ (510)
Proceeds from sale of common stock and warrants	$ 4,500	$ 2,300
Institutional investors
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Sale of common stock (in shares)	990,100	688,360
Sale of common stock (USD per share)	$ 5.05	$ 3.37
Placement agent
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Amount paid for placement agent commissions	$ 400	$ 193
Amount paid related to expenses for registered direct offering and concurrent private placement	$ 51	$ 50