Most large UK businesses are already familiar with ESOS — the Energy Savings Opportunity Scheme that requires qualifying organisations to carry out energy audits every four years. But ESOS Phase 4 brings meaningful changes to how compliance works, and with the deadline set for December 2027, now is the time to understand what’s coming and get ahead of it.
Who Qualifies for ESOS Phase 4?
The qualification date for Phase 4 is 31 December 2026. Your organisation qualifies if, on that date, it meets the definition of a “large undertaking” under UK law — meaning you employ 250 or more people, or you have an annual turnover above £44 million and a balance sheet total above £38 million for two consecutive years.
Crucially, if any entity within a corporate group qualifies, all other UK entities in that group are in scope too. That catches a lot of businesses that might otherwise assume they fall below the threshold.
If you qualified for ESOS in Phase 3, assume you’re in scope again for Phase 4 and plan accordingly.
The Compliance Deadline
The notification deadline for ESOS Phase 4 is 5 December 2027. To meet it, you’ll need to:
- Calculate your total energy consumption across a 12-month reference period that overlaps with 31 December 2026
- Commission a formal energy audit covering at least 95% of that total energy use
- Appoint a Lead Assessor — either an externally registered assessor or someone internally qualified
- Have a director or equivalent senior manager sign off the assessment
- Submit your compliance notification to the Environment Agency
That timeline sounds comfortable, but the reality is that Lead Assessors fill up fast. Organisations that wait until 2027 to start will struggle to secure good quality support in time. We’re already seeing demand build from clients who want to avoid the last-minute scramble that characterised previous phases.
What’s Changed in Phase 4?
Phase 4 isn’t just a repeat of Phase 3. There are several changes worth understanding.
Annual progress reporting is now required. Under Phase 3, action plans were submitted and then largely filed away. Phase 4 tightens this up significantly. Organisations must report progress against their action plan commitments annually, and if commitments haven’t been met, directors are required to provide a formal, documented explanation. These progress updates will be published by the Environment Agency within six months of each deadline, which means your energy performance will become publicly visible.
GDAs and DECs are no longer valid compliance routes. In previous phases, some organisations relied on Green Deal Assessments or Display Energy Certificates to satisfy ESOS requirements. Both have been removed from Phase 4. If your organisation used either route before, you’ll need to use a full energy audit or ISO 50001 certification this time.
Transport is firmly in scope. Energy used in business transport — fleet vehicles, company cars, freight — must be included in your ESOS assessment. Many businesses underestimated transport in earlier phases. Phase 4 requires it to be covered properly.
Net zero alignment is voluntary this phase, mandatory in Phase 5. The government introduced a voluntary net zero reporting option in Phase 4. Organisations that want to get ahead of the curve can align their ESOS work with their decarbonisation roadmap now. Those that don’t can expect it to become compulsory when Phase 5 arrives.
Why Starting Early Matters
ESOS has a reputation for last-minute scrambles. Phase 3 saw a significant number of organisations rushing to appoint assessors and gather data in the months before the deadline — and some still missed it.
Phase 4 is a longer cycle, but the increased reporting requirements and the removal of simpler compliance routes mean there’s more work involved, not less. The organisations that use this phase well will come out of it with a clear view of their energy baseline, a realistic action plan, and a head start on decarbonisation planning. Those that treat it as a compliance tick-box will miss the opportunity and face tougher questions under Phase 5.
We work with organisations at every stage of this process — from initial scoping and data collection through to lead assessment, action plan development and ongoing annual reporting support. If you’re unsure whether you qualify, or you want to understand what Phase 4 actually involves for your business, we’re happy to have that conversation.
Start the Conversation Now
ESOS Phase 4 compliance is not something to leave until 2027. If your organisation is likely to qualify — or if you’re already in scope and haven’t started planning — get in touch with the team at Green Team Consulting. We’ll help you understand what’s required, build a realistic programme, and make sure you’re not scrambling when the deadline arrives.
Find out more at www.gtconsulting.co.uk or email us at nick@gtconsulting.co.uk.