ESOS Newsletter August 2026 Issue 43

ESOS Phase 4

The government has made changes to ESOS, which came into force on 22 July via the Energy Savings Opportunity Scheme (Amendment) Regulations 2026. The main changes, as notified in previous ESOS newsletters, are:

• Removal of Display Energy Certificates (DECs) and Green Deal Assessments (GDAs) as compliance routes.

• Progress against action plan commitments in Phase 3 to be included in the ESOS assessment.

• Where action plan commitments have not been met, participants must provide an explanation.

In addition to the main changes, additional amendments have been made relating to:

• ISO 50001 participants

• Supporting regulator and professional body functions and improving data quality.

Organisations which meet the qualification criteria on the qualification date for the fourth compliance period of ESOS, 31 December 2026, are required to comply with ESOS and these changes by 5 December 2027. The ESOS guidance explaining how to comply has been updated to reflect the changes. You can check if your organisation qualifies here.

More information about the changes to ESOS is set out below, with references to the relevant chapters of the ESOS guidance. For an illustrated comparison of differences between the Phase 3 and Phase 4 requirements, please see Annex A.

Phase 4 changes:

I) Removal of DECs and GDAs as compliance routes and changes to ISO 50001 requirements – Chapters 7 – 9

These compliance routes have been removed as they are no longer considered to meet best practice standards. This means that from Phase 4 ESOS participants must use only energy audit(s) and / or ISO 50001 certification as compliance routes.

Participants with an ISO 50001 covering either the total energy consumption (TEC) or significant energy consumption (SEC) are exempt from:

• appointing a lead assessor (in Phase 3 this exemption only applied where ISO 50001 covered the whole of the TEC)

• completing an ESOS report.

II) Progress against action plan commitments – Chapter 10.4.1

To meet this requirement, participants must provide additional details about the energy savings achieved during the compliance period. The details, which must be included in the ESOS report and notification of compliance (NOC) and which will not be published, are:

• A description of each measure implemented to achieve the energy savings

• Energy savings achieved by each measure

• Energy saving category of each measure (e.g. behaviour change, training, capital investment).

III) Action plan review – Chapter 10.5

If you were eligible to comply with ESOS in Phase 3, you were required to prepare and submit an action plan. You are now required to review your action plan as part of the ESOS assessment and the information provided in the ESOS report and NOC. The details required, which will not be published, are:

• Any measures proposed in the action plan and not implemented

• Reasons why the measures were not implemented.

IV) Additional Phase 4 changes – Chapters 7, 11, 12 and Appendices A1 & A2 and Appendix B

• Lead assessors are now required to notify their professional body of each ESOS assessment they complete/review, along with the ESOS participant’s contact details. This is to allow the professional body to seek the ESOS participant’s consent to share its ESOS report so the professional body can carry out a quality check – see section 7.3 of Chapter 7

• The NOC must include the following – see Chapter 12 and Appendix B:

a. Total number of sites covered by energy audit(s) (voluntary in Phase 3)
b. ISO 50001 certification details (voluntary in Phase 3)
c. UK SIC codes only (replacing international codes in Phase 3).

• Improvements to recording of methods and data used for calculations – see Chapter 11 and Appendices A1 & A2.

MESOS User Management

Organisations should regularly review and maintain their contacts within the MESOS reporting system to ensure information remains accurate and up to date. Removing outdated contacts, such as individuals who have changed roles or left the organisation, helps protect sensitive information, prevents missed communications, and reduces the risk of unauthorised access.

Adding new users to the organisation account

1. Select ‘Users and Accounts’.

2. Select from the ‘add a new user’ dropdown box the user type you are wishing to add. The options are ‘Advanced User’ or ‘Restricted User’ with guidance on these different user types being given on the link below the drop-down box. Press continue.

3. Add the first name, last name and email address of the individual you are adding as a user.

4. An email will be sent to that new user to confirm their identity and create their login credentials.

5. Once this has been actioned you will need to change the users status from ‘Accepted’ to ‘Active’ which will then allow the user to sign in to the organisation account.

Disabling or removing a user from your account

1. Select ‘Users and Accounts’.

2. In order to disable the user from your account on the user line change their account status to ‘Disabled’.

3. In order to remove the user from your account completely on the user line select ‘Remove’.

GOV.​UK One Login rollout to MESOS

As detailed in our recent newsletters we have introduced a new way to sign in to the Manage your Energy Savings Opportunity Scheme Reporting system (MESOS), using GOV.​UK One Login. This is the new secure way to access government services and will be rolled out across more services in the future.

Upon signing into MESOS, users can now connect their MESOS accounts to One Login – please go to the MESOS sign in page and refer to the steps at Annex A – One Login Guidance below.

Annex A – One Login Guidance

Connecting GOV.​UK One Login to your MESOS account

1. Select ‘Start now’. You’ll be taken to GOV.​UK One Login, where you can create a GOV.​UK One Login if you do not already have one.

2. GOV.​UK One Login will return you to the MESOS service.

3. Choose to connect your existing MESOS account to your GOV.​UK One Login.

4. Confirm your identity using your MESOS sign in details.

Once connected, you’ll use GOV.​UK One Login to access your MESOS account from then on.

If you have forgotten your MESOS sign in details

Resetting either a password or a two-factor authenticator app (2FA) for your MESOS account

1. During the process of connecting GOV.​UK One Login to your MESOS account, you will be asked to enter your email address and confirm your identity using your existing MESOS password and 2FA.

2. If you need to reset your password, use the ‘I have forgotten or want to change my password’ link.

3. If you need to reset your authenticator app, use the ‘I have lost access to my authenticator app’ link.

4. You will receive an email which will allow you to reset either your password or your 2FA app. Please ensure that Junk/Spam folders are also checked for these emails.

5. If you still cannot sign in after following these steps, contact the ESOS IT helpdesk.

Resetting both the password and two-factor authenticator app (2FA) for your MESOS account

1. You must first reset one of the details, either your password or the 2FA app.

2. When you are asked for the other detail, select ‘I have forgotten my password and lost access to my authenticator app’.

3. You will be taken to the ‘Reset MESOS account password and authenticator app’ form.

4. Enter your name and the email address you use to sign in to MESOS.

5. Submit the form. You’ll get an email confirming that your request has been received. Once your request has been processed, you’ll get another email with a link and instructions on how to reset your MESOS sign in details. Please ensure that Junk/Spam folders are also checked for these emails.

END OF NEWSLETTER