ESOS is the UK’s mandatory energy assessment scheme for large organisations. Phase 4 runs to 5 December 2027 and qualification is judged on your position on 31 December 2026. The obligation is unavoidable for those in scope, and the audit that satisfies it is also where the cost savings are found.
Verification
- Verified as at:
- Source:
- gov.uk ESOS guidance; Environment Agency; SI 2014/1643 as amended
- Last reviewed by:
- Omnium
Figures in this sheet were current at the verification date above. Regulated charges reset each April. If you are relying on a figure, check the source or ask us.
Designed A4 fact sheet, ready to print or circulate.
The dates and thresholds
Status: LawThe dates and thresholds below are set in the ESOS regulations and apply to every organisation in scope.
| What | Detail |
|---|---|
| Qualification date | 31 December 2026. Your position on that day decides whether you are in scope. |
| Compliance deadline | 5 December 2027. Notification must reach the Environment Agency by then, via MESOS. |
| Coverage | 95 per cent of total energy consumption must be covered by the assessment. This was raised from 90 per cent for Phase 4. |
| Large undertaking test | 250 or more UK employees, or turnover above £44m together with a balance sheet total above £38m. |
Qualification is assessed afresh each phase. Not qualifying last time does not carry forward, and an organisation that missed the Phase 3 snapshot on 31 December 2022 may qualify now after four years of growth.
Full Phase 4 guidance is expected in early 2027. Where detail is still to come we will say so rather than fill the gap.
The group rule, which is the one most miss
If any single UK entity in a corporate group meets the test, every UK entity in that group is brought into scope, including ones individually well below the threshold.
That is the trap. A group can be captured by one qualifying subsidiary, and the entities that did not expect to be in scope are usually the ones with no data ready.
ESOS is not the SECR test
Status: LawThe two regimes use different tests and are routinely confused. ESOS is 250 or more employees on its own, or both financial thresholds together. SECR is two of three.
The same company can sit inside one regime and outside the other. Work it through on your actual figures rather than assuming that qualifying for one settles the other.
What Phase 4 requires
| Requirement | What it means |
|---|---|
| Measure total energy | Energy use across buildings, transport and industrial processes over a twelve-month reference period that includes the qualification date. |
| Audit 95 per cent of it | Significant energy consumption must be audited by, or signed off under, an approved ESOS lead assessor. |
| Identify savings | The audit must set out cost-effective energy saving opportunities with the energy and cost savings quantified. |
| Action plan and progress | An action plan is required, and progress against previous commitments must now be reported. Display Energy Certificates and Green Deal Assessments are no longer valid compliance routes. |
| Notify the regulator | A compliance notification to the Environment Agency, or the devolved nation equivalent, by 5 December 2027. |
What to do with the audit
ESOS is written as a compliance obligation, so it is usually handled as one: commission the assessment, file the notification, move on. That treats the most valuable part as overhead.
The audit produces a quantified list of cost-effective savings across the estate. Whether anything is done with that list is the difference between a compliance cost and a return.
We would rather help you act on the list than help you file it.
Related sheets
- Streamlined Energy and Carbon Reporting
Which companies and LLPs must disclose energy and emissions in their annual accounts, what has to be in the disclosure, and where SECR usually goes wrong.
- Carbon reporting and the three scopes
What Scope 1, 2 and 3 actually cover, how reporting goes beyond the legal minimum, and why customers now ask for it.
- The net zero roadmap
The order to decarbonise a building or portfolio in, and why measuring and reducing before generating and offsetting costs less.
Take this sheet into a meeting
ESOS Phase 4 is available as a designed A4 fact sheet, dated and set for printing or circulation.
If this sheet raises a question about your own sites, speak to us.