What is Fuel Mix Disclosure (FMD)?

The Electricity (Fuel Mix Disclosure) Regulations 2005 (SI 2005 No. 391) introduced a requirement on all electricity suppliers in Great Britain to disclose to their customers the mix of fuels used to generate the electricity supplied annually, provided that electricity is supplied for a full disclosure period (1 April – 31 March). Suppliers must disclose this information by 1 October annually. More information on this can be found in our letter to suppliers.

This regulation was introduced into electricity suppliers’ standard licence conditions (SLC), and is now SLC 21.


Renewable Energy Guarantees of Origin certificates (REGOs) must be held in a supplier’s Renewables and CHP Register account by midday 1 July following the generation disclosure period.

At midday on 1 July, all REGOs held in a supplier account on the Renewables and CHP Register for the relevant disclosure period that are not retired or revoked will be redeemed. Ofgem does this to capture REGOs used for GB FMD.

EU Guarantees of Origin (GoOs)

The UK Government announced in July 2022 its intention to cease the recognition of EU Guarantees of Origin (GoOs) from April 2023. The Government will continue to accept EU GoOs for the 2022-23 reporting period.

For the 2022-23 reporting period suppliers may use EU GoOs that have been recognised by Ofgem relating to the disclosure period for FMD. For EU GoOs, evidence must be provided that the electricity has been supplied in Great Britain and that the GoO has not been used outside Great Britain as evidence for fuel mix.

Requests to recognise EU GoOs must be submitted by midday 1 July 2023. We also expect market participants to be able to demonstrate proof of supply to GB requirements.

Ofgem does not recognise Non-EU GoOs for GB FMD.

For more information on GoOs, please see the Guarantees of Origin webpage.

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