Energy Savings Opportunity Scheme (ESOS) assessment

Where this applies

This record is scoped to United Kingdom. Scope is part of the claim: a rule that binds one part of a country does not bind the whole of it, and this library states the scope its sources state.

Instrument

The Energy Savings Opportunity Scheme Regulations 2014 (SI 2014/1643), Part 4 (reg. 20, duty to carry out ESOS assessment), as amended by SI 2018/1342, SI 2020/711, SI 2023/1182 and SI 2026/701. The scheme administrator is the Environment Agency (reg. 5).

Who it binds

UK undertakings that are a "large undertaking" on the qualification date, and any small or medium undertaking in the same group as one — subject to regulation 16, whose exclusions this record has not yet verified.

What it requires

Schedule 1 sets the size test: 250 or more employees, or a turnover over £44 million and a balance sheet total over £38 million — the turnover and balance-sheet limbs are cumulative, not alternatives — and reg. 15(1)(b) pulls in a small or medium group undertaking of such a large undertaking. Regulation 20 places the duty plainly: "A responsible undertaking must carry out an ESOS assessment… in accordance with this Part." Compliance periods run in four-year cycles — reg. 4(2) states that a subsequent period "(a) begins on the 6th December immediately following the end of the preceding compliance period, and (b) ends on the 5th December four years later." gov.uk gives Phase 4 a qualification date of 31 December 2026 and a compliance notification deadline of 5 December 2027. The assessment is signed off by a lead assessor and by a board-level director, and compliance is notified to the Environment Agency as scheme administrator under reg. 29; what the undertaking holds afterwards is that notification of compliance and the evidence pack it must keep under reg. 28. A participant whose energy management system is certified to ISO 50001 can be relieved of part of the duty under reg. 33 — the certification sits on the management system, and the relief is defined by how much consumption that system covers. Penalties sit in Part 8: reg. 45 (failure to undertake an energy audit) carries £50,000 or a lower amount set by the compliance body, plus up to £500 per working day subject to a maximum of 80 working days, plus a publication penalty; reg. 43 (failure to notify) carries up to £5,000 on the same daily basis; reg. 47 (false or misleading statement) carries up to £50,000.

Related records and requirements

• ISO 50001 — ESOS reg. 33 (as amended by SI 2026/701) names the standard: a participant whose energy management system is certified to ISO 50001 by an IAF- or UKAS-accredited body is deemed to have complied with Chapter 3 of Part 4 for any part of its consumption the system covers; where the system covers all of its total or significant energy consumption, it is deemed to have complied with regulation 21 and Chapters 3 and 3A of Part 4.
• Energy and Environment — The duty turns on an undertaking's size on the qualification date, not on its sector; energy consumption is what the assessment examines.