REGO and REEGO Certificates UK: What Genuine Renewable Energy Looks Like

A supplier advertising a "100% renewable" business energy tariff is not automatically misleading - but it is not automatically meaningful either. The mechanism at the centre of most such claims is the Renewable Energy Guarantees of Origin certificate, known as a REGO. Understanding how REGOs work, what they do not guarantee, and what a stronger alternative looks like helps businesses assess whether a tariff matches their sustainability commitments.

This guide explains the REGO scheme mechanics, the discontinued REEGO framework, the structural oversupply problem that has reduced the price of REGOs to near zero, and how to tell whether a tariff is backed by a genuine power purchase agreement or simply by certificate purchases made in bulk at the end of the year.

What a REGO certificate actually certifies

Ofgem administers the REGO scheme under the Renewables Obligation framework. A REGO is a certificate issued to an accredited renewable electricity generator for each megawatt-hour it produces and feeds into the grid. One certificate equals one MWh of verified renewable output from a specific installation.

The certificate contains information about the generating station: its fuel type (wind, solar, hydro, biomass and so on), its location, its accreditation number, and the period of generation. Ofgem publishes the central register of all certificates issued and redeemed.

Suppliers purchase REGOs separately from the electricity itself. The two transactions are not linked in real time. A supplier can buy electricity at any hour from any source on the wholesale market, and then purchase the corresponding volume of REGO certificates from generators to "match" that consumption on paper. This is legal under the scheme rules.

How the REGO market operates in practice

Because certificates are traded separately from electricity, a market for REGOs has developed independently of power markets. Generators sell REGOs either to their offtake counterparty or onto the open market through brokers or exchanges.

The volume of REGOs available has grown sharply as renewable capacity has expanded under the Contracts for Difference and Renewables Obligation programmes. By 2023-24, generation supported by those schemes was issuing far more certificates than the volume needed to back all tariffs marketed as green. This structural oversupply has driven REGO prices down to levels where the cost of "greening" a tariff adds only a fraction of a penny per kilowatt-hour to supplier costs.

Critics, including consumer groups and environmental organisations, have argued that cheap REGOs allow suppliers to market tariffs as renewable at minimal cost without funding any new renewable capacity or creating a direct link between the buyer's consumption and specific clean generation.

What REEGO was and why it was discontinued

REEGO stood for Renewable Energy Electricity Guarantee of Origin. It was proposed as an enhanced certification layer that would require a closer link between the certificate and the actual generation - addressing the time-matching and additionality criticisms of standard REGOs.

The scheme was developed to give buyers greater confidence that the renewable energy claim reflected genuine, traceable supply rather than bulk certificate purchases. However, REEGO did not achieve the market adoption needed to become a viable standard. Industry uptake remained low, and the framework was not continued. As of 2025, REEGO is no longer operational.

The discontinuation means the UK currently lacks a nationally administered enhanced certificate standard equivalent to the hourly matching frameworks developing in some European markets. This places more weight on contractual verification at the tariff level.

The additionality and time-matching debate

Two concepts matter when assessing the quality of a green energy claim: additionality and time-matching.

• Additionality refers to whether buying the tariff (or the underlying certificate) actually causes new renewable capacity to be built that would not otherwise exist. REGOs attached to long-established hydro stations, for example, fund no new generation.
• Time-matching refers to whether the renewable generation associated with the certificate occurred in the same hour or period as the consumption being claimed against. Annual matching allows a supplier to buy winter solar REGOs in March to cover consumption that occurred on a December evening.

Standard REGOs require neither additionality nor hourly matching. A certificate issued for generation in June can be redeemed against consumption in January of the same compliance year. This weakens the environmental signal considerably.

Power purchase agreements as an alternative

A power purchase agreement (PPA) is a direct contract between an energy buyer (or a supplier on behalf of a buyer) and a specific renewable generator. Under a PPA, the buyer commits to purchasing output from a named installation, typically at a fixed or indexed price, over a multi-year term.

PPAs offer stronger traceability because:

• The generator is identified in the contract
• The volume and timing of supply can be specified
• Some PPAs include sleeved delivery, meaning the power is tracked from generation to consumption
• Corporate PPAs can fund new-build projects, providing additionality

Some suppliers offer tariffs backed by their own PPAs rather than spot-market REGO purchases. The distinction matters for businesses with scope 2 emissions reporting obligations under frameworks such as SECR or voluntary standards like the RE100 initiative.

How to verify whether a tariff is REGO-backed or PPA-backed

Suppliers are required under Ofgem rules to provide fuel mix disclosure information showing the sources used to supply electricity sold. This appears on bills and on the supplier's website. However, fuel mix disclosure reflects a supplier's overall portfolio, not necessarily the specific tariff a business is on.

Steps to verify a tariff's green credentials:

1. Ask the supplier in writing for the certificate type (REGO or Guarantee of Origin) and the generation source.
2. Ask whether the tariff is backed by a direct PPA with a named generator or by certificate purchases made on the open market.
3. Ask for the generation station accreditation number and cross-reference it on the Ofgem Renewables and CHP register.
4. Check the fuel mix disclosure document, which must be published annually under Electricity (Fuel Mix Disclosure) Regulations 2005.
5. Review whether the supplier is a signatory to any third-party green energy verification scheme such as REGO Plus (where offered) or the Renewable Energy Association standards.

A supplier that cannot or will not provide generation station details beyond "REGO-backed" is likely using bulk certificate purchases rather than a dedicated supply contract.

Ofgem's role and the regulatory position

Ofgem administers the REGO scheme and publishes guidance on fuel mix disclosure requirements. It does not currently prohibit the use of standard REGOs to support green tariff claims, provided the disclosure is accurate. Suppliers must not make false or misleading statements about the environmental attributes of a tariff under the Advertising Standards Authority codes and Ofgem's supply licence conditions.

Ofgem has indicated ongoing interest in the quality of green tariff claims, and the issue has been raised in consultations on supplier licence obligations. Businesses procuring energy with sustainability criteria should monitor Ofgem guidance updates, as the regulatory framework for green tariff substantiation may evolve.

What this means for businesses with net-zero commitments

Businesses reporting scope 2 greenhouse gas emissions under SECR, the Task Force on Climate-related Financial Disclosures, or voluntary frameworks such as the Science Based Targets initiative are required to use market-based or location-based accounting methods. The Greenhouse Gas Protocol allows REGO certificates to satisfy market-based scope 2 reporting, but auditors and investors increasingly scrutinise the quality of certificates used.

Businesses with publicly stated net-zero targets or science-based targets may find that standard REGO-backed tariffs are insufficient to satisfy their reporting methodology or their board's expectations. A PPA-backed tariff, particularly one linked to a new-build generator, provides a stronger and more defensible position in sustainability disclosures.

Frequently asked questions

Editorial disclaimer: This article explains the REGO certificate framework as published by Ofgem and does not constitute energy procurement advice for any specific business situation.

Are REGO certificates the same as Guarantees of Origin?

REGOs are the UK's domestic equivalent of the European Guarantee of Origin (GoO) system. After the UK left the EU, Ofgem continued administering REGOs under domestic regulations. UK REGOs are no longer mutually recognised with EU GoOs, though some cross-border arrangements exist for imported renewable electricity under interconnector rules.

Can a supplier legally call a tariff "100% renewable" if it uses only REGOs?

Under current Ofgem rules and ASA advertising standards, a supplier can describe a tariff as renewable if it is backed by REGO certificates covering the full volume of supply. The claim must be accurate as to the volume matched. It does not require a PPA or hourly matching. Whether such a claim is environmentally meaningful is a separate question from its legal permissibility.

What happened to the REEGO scheme?

REEGO was an enhanced certificate framework designed to address the additionality and time-matching limitations of standard REGOs. It did not achieve sufficient market adoption to become a standard and is no longer in operation. The UK does not currently have a nationally administered enhanced certificate standard as a replacement.

Does switching to a REGO-backed tariff reduce a business's carbon footprint?

Under market-based scope 2 accounting in the Greenhouse Gas Protocol, purchasing electricity backed by REGO certificates allows a business to claim a zero emissions factor for that electricity in its accounts. Whether this represents a real-world carbon reduction depends on whether the certificate funds new renewable generation. Standard REGOs attached to existing capacity do not cause new clean energy to be built.

Where can a business check if a generating station is Ofgem-accredited?

The Ofgem Renewables and CHP register is publicly accessible and lists all accredited generating stations, their fuel type, capacity, and accreditation number. A supplier should be willing to provide the accreditation number of the station backing a tariff so it can be cross-referenced on that register.

How we verified this

This article draws on the Ofgem REGO scheme documentation published at ofgem.gov.uk, the Ofgem Renewables and CHP register, and the Electricity (Fuel Mix Disclosure) Regulations 2005 (legislation.gov.uk). The description of REEGO reflects publicly available information on its development and discontinuation as documented in Ofgem consultations. No aggregator, broker, or supplier-produced content was used as a primary source.

Sources

• Ofgem: Renewables Obligation scheme - ofgem.gov.uk
• Ofgem: Fuel Mix Disclosure - ofgem.gov.uk
• Electricity (Fuel Mix Disclosure) Regulations 2005 - legislation.gov.uk
• Ofgem: Guarantees of Origin and REGOs - ofgem.gov.uk

For more on choosing a green business energy tariff, see green-business-energy-uk.