Energy Attribute Certificates: REGOs, GoOs and I-RECs
REGOs, Guarantees of Origin and I-RECs are all energy attribute certificates. Which one a UK business can use, what each proves, and where the limits are.
An energy attribute certificate is a tradable record that one unit of electricity was generated from a particular source. The GHG Protocol calls them energy attribute certificates, and its market-based Scope 2 method uses them as evidence. Different parts of the world issue different ones. For a UK business the question that matters is simple: which certificate counts for electricity consumed here?
The main certificate families
| Certificate | Where it applies | Issued by |
|---|---|---|
| REGO (Renewable Energy Guarantee of Origin) | Great Britain and Northern Ireland | Ofgem, one certificate per MWh |
| Guarantee of Origin (GoO) | EU member states, under the Renewable Energy Directive | National issuing bodies, at a standard size of 1 MWh; cross-border transfers run through the AIB Hub |
| I-REC(E) | Countries with an authorised I-REC issuer | Issuers under the International Tracking Standard Foundation, formerly the I-REC Standard Foundation |
Sources: Ofgem — REGO; Directive (EU) 2018/2001, Article 19; AIB — the AIB Hub; International Tracking Standard Foundation — issuers. Verified 27 Sep 2026.
For electricity used in the UK, the certificate is the REGO
REGOs and EU GoOs used to be interchangeable. The EU stopped recognising UK REGOs from 1 January 2021, and from the disclosure period beginning 1 April 2023 EU GoOs no longer count for Great Britain's fuel mix disclosure. Ofgem notes that EU GoOs remain valid for Northern Ireland's fuel mix disclosure. RE100, the corporate renewable electricity initiative, treats the UK as a distinct market for renewable electricity, so under its current criteria a claim for UK consumption cannot rest on EU certificates.
I-RECs are not an option either. The International Tracking Standard Foundation's list of issuers does not include the United Kingdom, and it says I-RECs cannot be issued in a country without an authorised issuer. For a site in Great Britain the working certificate is the REGO. Our guide to REGO certificates covers how they are issued, redeemed and checked.
Sources: Ofgem — REGO Guidance for Generators, Agents and Suppliers, v4.0 (9 March 2026) (7.2); RE100 FAQs (August 2025); International Tracking Standard Foundation. Verified 27 Sep 2026.
What every certificate has in common
- It is separate from the power. Ofgem's guidance states that REGOs can be transferred separately from the renewable electricity, and the same is true of GoOs. That is what makes certificates tradable, and it is why a certificate proves origin rather than delivery.
- It only counts once used. A REGO supports a claim when it is redeemed by a supplier or voluntarily returned for cancellation in your name, and only for UK electricity already consumed.
- It expires. A GB REGO nobody uses is cancelled 16 months after the month of generation.
- It matches over a year, not an hour. Today's rules match certificates to consumption over a reporting period. The GHG Protocol consulted in 2025–26 on hourly matching, and in July 2026 announced a joint standard with ISO to be published in late 2028. Nothing has been adopted yet.
Where a PPA fits
A certificate on its own tells you where a megawatt-hour came from. A PPA with a new generator adds something a certificate cannot: your contract is the reason the generation exists. The two work together when the PPA transfers the generator's REGOs to you, which is the clause who owns the REGOs under a solar PPA walks through.
Sources: Ofgem — REGO Guidance for Generators, Agents and Suppliers, v4.0 (9 March 2026) (5.3, 6.21, 6.33–6.48); GHG Protocol — standard development update (July 2026). Verified 27 Sep 2026.
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