About the Energy Savings Opportunity Scheme (ESOS)

What is ESOS?

The Energy Savings Opportunity Scheme is a mandatory scheme requiring large UK organisations to report on their energy use and identify possible ways to save energy. It runs in four-year phases. 

We are now in Phase 4 – which officially started on 6 December 2023. If you are in scope, you must submit a compliance notification by 5 December 2027.

If you were in scope of Phase 3, you should be preparing to submit your second Progress Update Report by 5 December 2026.

Does my business have to comply with ESOS?

ESOS applies to “large undertakings.” This is defined as any UK company that:

  • employs 250 or more people;
  • and has an annual turnover in excess of £44 million
  • and has an annual balance sheet total in excess of £38 million.

The qualification date for Phase 4 is 31 December 2026. If your business meets the above criteria on this date, you are eligible for Phase 4. 

ESOS Action Plans and Progress Reports

Since Phase 3, ESOS has included additional requirements following the submission of the notification of compliance. These are ESOS Action Plans and ESOS annual Progress Updates. These enable organisations to set out how they are taking forward their ESOS recommendations. 

Your Action Plan should outline:

  • What you intend to do to reduce your organisation’s energy consumption over the next four years;
  • When you intend to do it;
  • Whether it was recommended through your ESOS assessment;
  • What energy savings you expect to see by carrying out your action plan; and
  • How you estimated those energy savings.

For Phase 3:

  • Progress Report 1 was due on 5 December 2025.
  • Progress Report 2 is due on 5 December 2026.

Your plan and progress updates will be made public.

Can I get started on ESOS Phase 4?

Yes – you can (and should!) start work on ESOS Phase 4 now.

We are in the Phase 4 compliance window, so you can start conducting site audits, gathering data and appointing a Lead Assessor. Sustainable Energy First has a team of qualified Lead Assessors who can support you with ESOS compliance. For advice or more information, get in touch. 

The deadline for your notification of compliance is 5 December 2027.

How is ESOS Phase 4 different to Phase 3?

Following new legislation, ESOS has been amended and the government has published new guidance for Phase 4. There are some changes compared to Phase 3:

  • Green Deal Assessments (GDAs) and Display Energy Certificates (DECs) are no longer valid compliance routes.
  • Participants must report on energy savings achieved during the compliance period. This includes a description of the measures implemented to achieve the energy savings, the level of energy savings achieved by each measure and the energy saving category of each measure.
  • Participants must carry out an Action Plan review as part of the notification of compliance – identifying any proposed measures that were not implemented and explaining why.
  • Three annual Progress Update reports are required following submission of the Action Plan: on 5 December 2029, 2030 and 2031.
  • There are reduced ESOS obligations for participants that comply solely through the ISO 50001 certification route – participants whose ISO 50001 certification covers their total or significant energy consumption do not need to produce an ESOS report or appoint a lead assessor.

Mandatory net zero requirements will be delayed to Phase 5: The government had previously announced its intention to align ESOS Phase 4 audits with net zero. These will now be postponed until Phase 5 (2027-2031).

Summary of key dates:

ESOS Phase 3:
  • Phase 3 compliance deadline: 6 August 2024
  • Submission of Action Plan: 5 March 2025 (extended from 5 December 2024)
  • Phase 3 Progress Update report deadlines: 5 December 2025 and 5 December 2026
ESOS Phase 4:
  • Phase 4 qualification date: 31 December 2026
  • Phase 4 compliance deadline: 5 December 2027
  • Phase 4 Action Plan deadline: 5 December 2028
  • Phase 4 Progress Update report deadlines: 5 December 2029, 5 December 2030 and 5 December 2031

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ESOS FAQs

We’ve put together the most frequently asked questions on ESOS, to help you meet compliance.

Go to ESOS FAQs

How to navigate ESOS?

Business guide to UK energy and carbon compliance

You will learn:

  • Overview of mandatory schemes in the UK, including SECR, ESOS, TCFD reporting and the Minimum Energy Efficiency Standards
  • Future reporting requirements, including the Sustainability Disclosure Requirements
  • Voluntary schemes to help you achieve best practice
  • Financial incentive schemes to help you decarbonise
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