Prepare now for ESOS Phase 4. Comply with confidence and uncover practical savings.
ESOS requires qualifying organisations to assess their energy use, identify tailored and cost-effective energy-saving opportunities, and notify compliance every four years.
ReEnergise combines Lead Assessor oversight with energy engineering and commercial analysis. This helps turn the required assessment into practical information that can support future operational and investment decisions.
What needs to be done
Establish the scope
Confirm qualification, group structure, organisational boundaries and the energy consumption that must be assessed.
Assess energy use
Collect and analyse energy data that includes 31 December 2026, undertake appropriate site surveys and identify practical, cost-effective energy-saving opportunities.
Report and comply
Prepare the ESOS report and evidence pack, secure board-level approval and submit the notification of compliance through the MESOS portal by 5 December 2027.
Qualification date: 31 Dec 2026
Your 12-month energy reference period must include this date.
Could your organisation qualify?
Your organisation will need to comply if, on 31 December 2026, it:
- employs 250 or more people; or
- has an annual turnover above £44 million and a balance sheet above £38 million.
Corporate groups may qualify if at least one UK group member meets the criteria.
Organisations close to the thresholds, or whose size has changed, may need to review more than one accounting period when determining their status.
What's changing in Phase 4?
Phase 4 retains the requirement to assess at least 95% of total energy consumption and introduces stronger requirements to demonstrate and report action. Organisations will need to report progress against previous action plans - the measures implemented and the energy savings achieved during the compliance period - and explain why committed actions have not been implemented.
Important: Display Energy Certificates (DECs) and Green Deal Assessments can no longer be used as ESOS compliance routes.
Why start now?
ESOS requires total energy consumption to be calculated over 12 consecutive months, including 31 December 2026. Starting now gives you time to establish complete, verifiable records across buildings, transport and operational activities. This helps you to:
- resolve missing or inconsistent energy data;
- plan surveys around operational requirements;
- involve the right finance, estates and operational stakeholders;
- review progress against previous action plans;
- identify cost-saving opportunities earlier;
- avoid a rushed assessment and reduce compliance risk.
What we deliver
Qualification and scoping
We confirm qualification, corporate-group and organisational scope, compliance requirements, assessment boundaries and the delivery plan.
Project management
We coordinate data collection, surveys, technical assessment, reporting and approvals, with clear responsibilities and timescales.
Data collection and review
We collect and review energy data across buildings, transport, industrial processes and other operational activities, identifying gaps and anomalies that need to be resolved.
Site surveys
Our engineers examine how energy is used in practice and identify realistic opportunities for improvement without losing sight of operational requirements.
Energy analysis and benchmarking
We apply relevant benchmarks and engineering judgement to identify and prioritise practical opportunities, with estimated cost and carbon savings, implementation costs and payback periods where appropriate.
ESOS report and evidence pack
We prepare the required Phase 4 report and supporting evidence in accordance with current requirements, reviewed by a registered ESOS Lead Assessor.
Board-level approval
We prepare the information required for director review, approval and organisational sign-off.
Submission support
We support completion of the compliance notification through the Environment Agency’s MESOS portal.
The precise assessment and analysis required will depend on your organisational structure, energy use, available data and agreed scope. Our pricing is competitive, with the added value of experienced energy engineering insight.
Frequently Asked Questions
Who needs to comply with ESOS Phase 4?
ESOS applies to large UK undertakings and corporate groups containing a large UK undertaking. An undertaking may qualify if it employs 250 or more people, or has annual turnover above £44 million and an annual balance-sheet total above £38 million. Group structures and changes in organisational size can affect the assessment, so the headline thresholds should be treated as an initial check.
What is the Phase 4 qualification date?
The qualification date is 31 December 2026. Whether an organisation qualifies is determined by its status on that date, applying the relevant accounting-period and organisational rules.
When is the Phase 4 compliance deadline?
The deadline for submitting the Phase 4 notification of compliance is 5 December 2027.
Why do we need to prepare before 31 December 2026?
The total-energy-consumption calculation must use a reference period of 12 consecutive months that includes the qualification date and ends before the compliance deadline. Preparing early also creates time to confirm organisational scope, data ownership and gaps.
What energy use needs to be considered?
The total-energy-consumption calculation may include energy used by buildings, transport, industrial processes and other activities for which the participating organisation is responsible. At least 95% of total energy consumption must be included.
What has changed for Phase 4?
Display Energy Certificates and Green Deal Assessments can no longer be used as alternative compliance routes. Phase 4 also introduces stronger requirements to report achieved savings, review previous action-plan commitments and explain why proposed measures were not implemented.
What does ReEnergise provide?
ReEnergise can coordinate qualification and scoping, data review, site surveys, technical assessment, reporting, evidence preparation, Lead Assessor review, board-level approval information and MESOS notification support. Engineering or modelling beyond the agreed ESOS scope will be identified and agreed separately where it would add value.
Can we use ISO 50001 as a route to compliance?
An appropriately certified ISO 50001 energy-management system may provide a route to compliance where it covers the required energy consumption and meets the Phase 4 conditions. The precise reporting and Lead Assessor requirements depend on the extent of that coverage.