Energy Savings Opportunity Scheme (ESOS) - Phase 4

ESOS Phase 4 Compliance

What You Need to Know, at a Glance

If your organisation qualifies as a large undertaking, ESOS Phase 4 is now underway.

The qualification date is 31 December 2026, with final compliance due by 5 December 2027.

ESOS requires qualifying organisations to assess their energy use, identify cost‑effective savings, and appoint an ESOS Lead Assessor to validate compliance — all with board‑level sign‑off.

Start early to reduce risk, control costs, and turn ESOS into a strategic opportunity.

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ESOS Phase 4: A Simple 4‑Step Compliance Guide

1. Confirm ESOS Scope and Appoint a Lead Assessor

Establish whether your organisation qualifies and set the compliance framework.

This step confirms ESOS eligibility, organisational boundaries and energy use in scope. An ESOS Lead Assessor must be appointed to oversee or validate compliance, including audit methodology, coverage and outputs.

2. Collect Energy Data and Identify Significant Uses

Understand where and how energy is consumed.

Energy consumption data is gathered for the reference period across buildings, industrial activities and transport. This data is reviewed to identify significant energy uses and ensure at least 95% of total energy consumption is included within scope.

3. Complete ESOS Energy Audits and Action Planning

Identify efficiency opportunities and agree next steps.

ESOS energy audits are carried out or reviewed by the Lead Assessor to assess energy performance and identify cost‑effective savings opportunities. Findings are captured in an action plan, outlining potential measures, estimated savings and implementation priorities.

4. Secure Sign‑Off and Submit Compliance

Finalise governance and notify the regulator.

A board‑level director reviews and approves ESOS compliance. A notification of compliance is then submitted via the official ESOS reporting system, and all supporting evidence is retained for audit and future phases.

ESOS Phase 4: Key Details at a Glance

Who Needs to Comply

Your organisation must comply with ESOS Phase 4 if it qualifies as a large undertaking on the qualification date.

You are likely in scope if, on that date, your organisation:

Employs 250 or more people, or
Has an annual turnover above £44 million and a balance sheet total above £38 million

Group structures matter: if one UK entity in a corporate group qualifies, the entire UK group may fall within scope. UK branches of overseas companies may also qualify. [gov.uk], [teamenergy.com]

Key Dates

Phase start: 6 December 2023
Qualification date: 31 December 2026
Compliance deadline: 5 December 2027

Your qualification status is judged strictly on the qualification date, regardless of whether you qualify today. [teamenergy.com], [cesgb.com]

What ESOS Phase 4 Requires

Organisations in scope must:

Measure total energy consumption across buildings, transport and industrial processes
Cover at least 95% of total energy use
Complete ESOS‑compliant energy audits or use a recognised alternative route
Appoint an approved ESOS Lead Assessor
Produce and maintain an energy savings action plan
Obtain board‑level sign‑off
Submit a notification of compliance to the regulator

Supporting evidence must be retained in case of audit or enforcement action. [gov.uk], [seemoreenergy.co.uk]

Who Oversees Compliance

An ESOS Lead Assessor must be appointed. They are responsible for:

Reviewing audit scope and methodology
Confirming compliance with ESOS rules
Validating findings and recommendations

The final ESOS submission must be signed off by a board‑level director or equivalent. [gov.uk]

What Happens If You No Longer Qualify

If your organisation does not meet the thresholds on the qualification date but qualified in a previous phase, you should submit a“Do Not Qualify” (DNQ) notification through the ESOS reporting system. [energyadvicehub.org]

Why Start Early

Although the final deadline is December 2027, early preparation:

Reduces compliance risk
Makes it easier to secure a Lead Assessor
Improves data quality
Spreads cost and effort
Helps identify energy cost savings sooner

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