Guidance

Energy Savings Opportunity Scheme (ESOS)

Find out if you qualify for ESOS and how to comply.

From:
Department for Energy Security and Net Zero, Environment Agency and Department for Business, Energy & Industrial Strategy
Published
26 June 2014
Last updated
3 October 2024 — See all updates

October 2024 update

The extension to the deadline for submitting notifications of compliance for phase 3 of ESOS has now passed.

Any organisation that qualifies for phase 3 of ESOS and has failed to submit a notification of compliance is now at risk of enforcement action and should contact the Environment Agency immediately.

You must ensure that you respond promptly to any communication you receive from the Environment Agency.

For full details of how to comply with ESOS requirements see:

The guidance works alongside the legislation to help participants understand the requirements, but the ultimate source of ESOS requirements is the legislation.

About the Energy Savings Opportunity Scheme (ESOS)

ESOS is a mandatory energy assessment scheme for organisations in the UK that meet the qualification criteria. The Environment Agency is the UK scheme administrator.

Organisations that qualify for ESOS must carry out ESOS assessments every 4 years. These assessments are audits of the energy used by their buildings, industrial processes and transport.

The ESOS audit is designed to identify tailored and cost-effective measures to allow participating businesses to save energy and achieve carbon and cost savings. The audit costs are estimated to be significantly outweighed by the savings from implementing the recommendations.

Find out if you qualify for ESOS phase 3

ESOS applies to large UK undertakings and their corporate groups. It mainly affects businesses but can also apply to not-for-profit bodies and any other non-public sector undertakings that are large enough to meet the qualification criteria.

Your organisation qualifies for the third compliance period (ESOS phase 3) if, on 31 December 2022, it met the ESOS definition of a large undertaking.

Corporate groups qualify if at least one UK group member meets the ESOS definition of a large undertaking.

UK registered establishments of an overseas company will also need to take part in ESOS (regardless of their size) if any other part of their global corporate group activities in the UK meet the ESOS qualifying criteria.

If you’re very close to the qualification threshold or have substantially increased or decreased in size in recent years, read the full guidance on complying with ESOS. This includes additional information on how to assess if you qualify.

Public sector organisations do not usually need to comply with ESOS. For more information on organisations that do not need to comply, see section 1.2 of the full guidance on complying with ESOS

Large undertakings

For the qualification date for the third compliance period of ESOS (31 December 2022) a large undertaking is any UK company that either:

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

A person is employed by an undertaking if they are:

  • an employee
  • an owner or manager
  • a partner

An ‘employee’ is a person employed under contracts of service. Their contracted hours and status (full time or part time) are irrelevant to their classification as an employee.

For further guidance on who qualifies for ESOS, see section 1 in the full guidance.

Deadlines for ESOS compliance

Organisations that qualify for ESOS must notify the Environment Agency by a set deadline that they have complied with their ESOS obligations.

The deadline for submitting notification of compliance for phase 3 of ESOS was 5 June 2024.

Any organisation that qualifies for phase 3 of ESOS and has failed to submit a notification of compliance is now at risk of enforcement action and should contact the Environment Agency immediately.

The qualification thresholds and date have not changed; ESOS still applies to all organisations (and their corporate groups) that were classed as large undertakings on 31 December 2022.

Organisations that qualify for ESOS in Phase 3 will be required to comply with the Energy Savings Opportunities Scheme (Amendment) Regulations 2023.

Changes include:

  • standardization through strengthening requirements for audits
  • all participants are now expected to produce an ESOS report, action plan and annual progress reports
  • participants will now also be required to publicly disclose high level recommendations

ESOS regulation and penalties

Your environmental regulator is responsible for compliance and enforcement activities. It may issue civil sanctions including financial penalties if an organisation does not meet the scheme’s obligations.

Read the Environment Agency’s approach to ESOS regulation and penalties in their enforcement and sanctions policy (annex 2, section D). Other scheme regulators apply a similar approach - see section 15 of the full guidance.

A summary of the penalties imposed is available on data.gov.uk.

If you do not qualify for ESOS phase 3

If you have been contacted by the Environment Agency in the past, or you qualified for phase 1 and/or phase 2 but not for phase 3, you need to tell the Environment Agency you do not qualify.

Complete an ESOS assessment

Completing an ESOS assessment now has additional requirements, in line with the 2023 regulations.

For full details of how to comply with ESOS requirements, see:

The guidance works alongside the legislation to help participants understand the requirements, but the ultimate source of ESOS requirements is the legislation.

Summary of the steps required to complete an ESOS assessment

1. Calculate your total energy consumption

This is the energy used by assets held or activities carried out by your organisation or group. This includes the energy consumed by buildings, industrial processes and transport.

2. Identify your areas of significant energy consumption

This is the energy used by assets held, or activities carried out, by your organisation that needs to be included in an energy audit or covered by another route to compliance (see 4 below) and must account for at least 95% of your total energy consumption.

3. Calculate your energy intensity ratios

You must calculate energy intensity ratios for each of:

  • buildings
  • transport
  • industrial processes
  • other energy uses outside of the above 3

An energy intensity ratio is a measurement which relates an organisation’s consumption to an appropriate indicator activity. This allows comparison of energy efficiency performance over time.

For full details on calculating energy intensity ratios, see section 6 in the full guidance.

We recommend the approach set out in the full guidance, but the legal requirement is that the indicator for each organisational purpose is: 

  • quantifiable
  • associated with the assets or activities that relate to the specific organisational purpose

You should explain the approach you have taken in your compliance notification, if it differs from the one suggested in guidance. You should also keep a record of the approach you have taken in your evidence pack.

4. Decide on your route(s) to compliance and appoint a lead assessor

You must choose one or more routes to compliance, ensuring all areas of either significant or total consumption (as appropriate) are covered.

If complying with ISO 50001, display energy certificates and/or green deal assessments, it must have been issued after 5 December 2019 and be valid at either the original compliance date (5 December 2023) or the extended compliance date (5 June 2024).

All participants need to have their ESOS assessment signed off by an ESOS lead assessor, unless 100% of your energy supplies are covered by ISO 50001,  or your total energy consumption is less than 40,000 kWh.  

For guidance on appointing a lead assessor and using an alternative compliance route, see Sections 7 and 9 in the full guidance.

5. Carry out any necessary ESOS energy audits

An ESOS compliant energy audit must meet these criteria:

  • it must be based on 12 months’ verifiable data, beginning no early than 6 December 2018 for the phase 3 compliance period
  • it must analyse the participant’s energy consumption and energy efficiency
  • it must identify energy saving opportunities
  • it must include site visits

For guidance on carrying out an ESOS energy audit, see Section 8 in the full guidance.

6. Complete the ESOS report and share with the corporate group

You must complete an ESOS report detailing your ESOS assessment (audit or alternative compliance route), unless you have zero energy supplies.

The ESOS report is a record of your assessment and includes information about the compliance route used and what it covers, the energy saving opportunities identified and energy savings achieved since the previous ESOS compliance date.

If your organisation is part of a corporate group you must provide relevant information from the ESOS report to all members of the corporate group, as detailed in the Energy Savings Opportunities Scheme (Amendment) Regulations 2023.

For more detail of the specific requirements for an ESOS report, see section 10 in the full guidance.

7. Notify the Environment Agency

When you have undertaken an ESOS assessment and are compliant with your obligations, you must submit a notification of compliance using the Managing your ESOS system.

The notification includes:

  • details about your organisation
  • how it has complied
  • energy consumption information
  • energy savings opportunities that have been identified

The deadline for submitting a compliance notification for the current (third) compliance period was 5 June 2024.

Any organisation that qualifies for phase 3 of ESOS and has failed to submit a notification of compliance is now at risk of enforcement action and should contact the Environment Agency immediately.

Before submitting the compliance notification, you must get one board level director or person exercising management control from one of the undertakings in the participant group to sign off on both the ESOS assessment and the content of the compliance notification.

See section 11 in the full guidance for more details on Director sign-off.

Use the Managing your ESOS (MESOS) system to complete your notification of compliance

You can partially complete your notification and save it for submitting later.

Start your notification of compliance now

The scheme administrator will publish the majority of the information in your compliance notification, with the exception of personal or commercially sensitive details and feedback. Appendix B of the full guidance provides details of the information that will be published.

8. Evidence pack

You need to keep records of how you have complied with ESOS in an evidence pack.

For details of what you must include in your evidence pack, see Section 14 of the full guidance.

ESOS action plan and annual progress updates

For Phase 3 onwards, ESOS will include additional compliance stages following the submission of the compliance notification: ESOS action plan and ESOS annual progress updates.

The action plan must be signed off by a board level director (or equivalent), and submitted via the compliance notification system by the action plan deadline for the third compliance period, which is 5 December 2024.

For details about ESOS action plans, see Section 12 in the full guidance.

Annual progress updates

Following submission of the action plan, you must submit an annual progress update against your action plan commitments in the 2 subsequent years.

The deadline for submitting an annual progress update is 12 months after the action plan deadline, and then 12 months after the submission deadline for the first progress update. For the third compliance period, the deadlines are 5 December 2025 and 5 December 2026.

The progress update must be signed off by a board level director (or equivalent), and submitted via the notification system, where it will be published.

For full details of ESOS annual progress updates, see Section 13 of the guidance.

List of approved registers for ESOS lead assessors

If you want to become a lead assessor, you have to be (or become) a member of an approved professional body register. Individuals cannot apply directly to the Environment Agency to be approved. You can contact the approved organisations listed here for further information about the application processes or approved lead assessors on their registers.

ESOS: published data

Notification of compliance data

The Environment Agency publishes the data provided by organisations that submitted a notification of compliance in phases 1 and 2 of ESOS. This data is published to meet the Environment Agency’s statutory responsibility under the Energy Savings Opportunity Scheme Regulations 2014 and in alignment with government open data policies.

The published data:

  • shows the information on existing requirements that are published by the scheme administrator, as detailed in Appendix B of the full guidance on complying with ESOS
  • does not include personal data – this is protected under the General Data Protection Regulation 2018
  • contains no amendments – unless requested or to remove personal data
  • has not been verified for compliance – it is a record of notifications

Some organisations within a group may be covered by a notification of a UK parent and may not be readily identifiable.

More information about ESOS

The introduction of ESOS in 2014 addressed a finding in the 2012 UK Energy Efficiency Strategy that lack of information was a key barrier to the uptake of energy efficiency measures by business.

Government established ESOS to implement Article 8 (4 to 6) of the EU Energy Efficiency Directive (2012/27/EU). The ESOS Regulations 2014 give effect to the scheme.

The current high cost of energy and the UK’s net zero legislation has made it more important to help businesses reduce their energy and emissions since leaving the EU. A Post Implementation Review of ESOS in 2020 found businesses were unlikely to carry out energy audits unless mandated to do so, which makes ESOS an important lever in encouraging energy efficiency in business.

UK regulators

The UK regulators are:

  • Environment Agency for organisations whose registered office is in England
  • Natural Resources Wales for organisations whose registered office is in Wales
  • Northern Ireland Environment Agency for organisations whose registered office is in Northern Ireland
  • Scottish Environment Protection Agency for organisations whose registered office is in Scotland
  • Secretary of State for Department for Energy Security and Net Zero for organisations whose activities consist wholly or mainly of offshore activities

Contact details

For more information on ESOS, email esos@environment-agency.gov.uk. The Environment Agency will respond within 10 working days. Send your queries well in advance of the compliance deadline to ensure you have enough time to fulfil your obligations before submitting your notification of compliance.

For queries on the MESOS reporting system, email esos-it@environment-agency.gov.uk.

For offshore related queries, email OPRED@energysecurity.gov.uk.

Updates to this page

Published 26 June 2014
Last updated 3 October 2024 + show all updates

  1. The extension to the deadline for submitting notifications of compliance for phase 3 of ESOS has now passed.

  2. If your organisation qualifies for ESOS Phase 3 but has not yet submitted a notification of compliance, you need to do so by 6 August 2024.

  3. The Manage your Energy Savings Opportunity Scheme (MESOS) system is now available to complete your notifications of compliance.

  4. The Manage your Energy Savings Opportunity Scheme (MESOS) system is now available for you to register your Phase 3 user and organisational accounts.

  5. Guidance updated to reflect the changes for Phase 3.

  6. Removed 'ECMK Limited – ECMK ESOS lead assessor register' from the list of Approved registers of ESOS lead assessors as they are no longer taking part in the scheme.

  7. Added what a 'large undertaking' is defined as for the qualification date for the third ESOS compliance period, which will be 31 December 2022.

  8. Added information about ESOS phase 2.

  9. Added under section: ESOS regulation and penalties 'We publish a summary of the penalties imposed on data.gov.uk'.

  10. Updated link to The Institute of Environmental Management and Assessment to: https://www.iema.net/specialist-registers/join-esos/iema-esos-lead-assessor-register.

  11. Update to the ESOS compliance dataset. Removal of ‘intend to comply’ information as this is no longer relevant.

  12. This update is to reflect the latest position on ESOS notifications up to 31 January 2017.

  13. Section 'ESOS published data': data published on data.gov.uk provided by the organisations that submitted an intent to comply notification by 25 August 2016.

  14. Section 'ESOS published data': See the published data provided by the organisations that submitted a notification of compliance by 30 June 2016.

  15. New section 'ESOS published data'.

  16. If you qualify for ESOS you should have submitted your notification of compliance by 5 December 2015. Submit your notification as soon as possible if you haven’t done so already.

  17. You must inform the Environment Agency by 5 December 2015 if you cannot submit a notification of compliance, using the online form.

  18. Text updated to reflect the Environment Agency's amended Enforcement and Sanctions Guidance.

  19. ESOS workshop dates and venues announced for March 2015.

  20. Exchange rate figures added for pound sterling for the first compliance period based on the Bank of England daily spot exchange rate on 31 December 2014 (the qualification date).

  21. Updated list of approved registers. Text amended to reflect that the application process for registers is now closed.

  22. Page updated with: * the link to the online notification system * the list of approved lead assessors

  23. Update to the application process for registering qualified energy professionals to act as lead assessors for ESOS.

  24. First published.

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