ESOS compliance — how to comply, step by step

ESOS — the Energy Savings Opportunity Scheme — is the UK’s mandatory energy assessment scheme for large undertakings, established by the ESOS Regulations 2014 (SI 2014/1643) 1 and administered by the Environment Agency. If you are new to the scheme itself, start with the ESOS overview; this page is the practical compliance guide — who qualifies, what you must do, by when, and what it costs to get it wrong.

The canonical official ESOS compliance guidance is the GOV.UK ESOS guidance 2, maintained by the Environment Agency and DESNZ. Read it alongside the ESOS (Amendment) Regulations 2023 (SI 2023/1182) 3, which raised the audit coverage requirement to 95% and added the Part 6A action plan and progress-update obligations that now run between phases.

Measure total energy consumptionRequirement 1

Calculate total energy use across buildings, transport and industrial processes for a 12-month period that includes the qualification date. This total defines the 95% that must be covered by audits or ISO 50001.

Audit at least 95% of consumptionRequirement 2

Cover at least 95% of total energy consumption through ESOS-compliant energy audits, ISO 50001 certification, or a mixed approach. The threshold was raised from 90% to 95% by SI 2023/1182. The remaining ≤5% is the de minimis exclusion.

Lead assessor reviewRequirement 3

A registered lead assessor must review and sign off the assessment, unless 100% of consumption is covered by ISO 50001 or total energy use is below 40,000 kWh a year.

Board-level director sign-offRequirement 4

A board-level director must review the assessment and confirm the organisation is compliant before the notification is submitted. This is a personal, named accountability step.

Notify via MESOSRequirement 5

Submit the compliance notification through the Environment Agency’s Manage your ESOS reporting (MESOS) service 4 by the phase deadline — 5 December 2027 for Phase 4.

Action plan + progress updatesRequirement 6

Under Part 6A (inserted by SI 2023/1182), participants must submit an ESOS action plan after notification and follow it with board-signed annual progress updates — turning ESOS from a one-off audit into a continuous obligation between phases.

Complying with the Energy Savings Opportunity Scheme means working to its four-year phase cycle. Each phase fixes a 31 December qualification date, allows roughly a year for assessment, and closes with a 5 December notification deadline 1. Since SI 2023/1182, the years between notifications are no longer quiet: the action plan and its annual progress updates keep participants reporting continuously. Phase 3 participants, for example, still owe a progress update on 5 December 2026 — the same month as the Phase 4 qualification date.

The Environment Agency applies ESOS civil penalties using the stepped approach in Annex 2 of its enforcement and sanctions policy 5 — starting from the statutory maximum for the breach, then adjusting for culpability, organisation size, history and cooperation. The statutory maxima under SI 2014/1643 include an initial penalty of up to £50,000 for failing to undertake an energy audit, up to £5,000 for failing to notify or to maintain records, and daily penalties of up to £500 per working day (capped at 80 working days) for continued breach 1.