Understanding Renewable Energy Guarantee of Origin (REGO) Certificates

A Renewable Energy Guarantee of Origin, or REGO, is a certificate that Ofgem issues to renewable energy generators for every megawatt hour (MWh) of electricity they generate. The certificates are used as evidence that electricity sold by a generator and a supplier is genuinely “green”, which in turn lets suppliers and their business customers stand behind the renewable claims they make. As REGOs are given per MWh generated, it is straightforward for businesses to quantify their progress towards Net Zero and with more and more organisations setting Net Zero targets, this kind of assurance has become a key part of demonstrating progress against carbon goals. It’s also worth noting that in addition to REGOs, you can also obtain Renewable Gas Guarantees of Origin (RGGOs) certificates.

TL;DR

• REGO certificates are issued by Ofgem to renewable generators for every megawatt hour (MWh) of eligible renewable electricity they generate.
• A REGO-backed contract does not always mean your business is directly using renewable electricity, as certificates can be bought separately from the physical power.
• Bundled REGOs, PPAs and time-matched REGOs offer stronger traceability, helping businesses support renewable claims with clearer evidence.
• Businesses should review renewable energy contracts carefully, as REGO prices, generation sources and supplier claims can vary significantly.

How do REGOs work?

Signing up for a REGO-backed contract does not automatically mean the energy itself is renewable. It means that the supplier has purchased REGO certificates to effectively pair wholesale electricity with electricity that was generated from a renewable source at some stage.

If full traceability is important to a business, a Power Purchase Agreement (PPA) can be used. A PPA is a long-term contract between the supplier and a renewable generator. When the generator sells to the supplier under this arrangement, the electricity is supplied with its associated REGO certificate. These are known as bundled REGOs and allows for “pure green” electricity supply. This can then be mirrored from the supplier to a consumer to provide authentication throughout the supply chain.

Because the certificate and the underlying electricity can be split apart, REGOs are bought and sold on a secondary market in much the same way as power itself. That naturally means their price fluctuates according to the current levels of supply and demand.

In early 2020, certificates were trading at roughly £0.20 each. By October 2023 prices had risen sharply to a peak of around £25. Brexit was the main driver of this increase, as from January 2021 the EU and the UK no longer recognised each other’s certificates. This removed roughly 70 to 80 TWh of EU REGO supply from the UK market. Since that 2023 peak, prices have steadily declined as more UK renewable capacity has come online and some larger suppliers have shifted away from REGO-backed tariffs towards direct Power Purchase Agreements. As of early 2026, certificates are typically trading in the £0.50 to £2 per MWh range, although the market remains volatile and prices can vary considerably by vintage and generation source.

Any generator using an eligible renewable source can apply to receive REGO certificates, provided they have the appropriate Ofgem accreditation of the legal and technical requirements to be considered a renewable generator. In practice, applicants must register their station via the Renewables and CHP Register, evidence that the generating station uses an eligible renewable source, have settlement-grade metering in place, and confirm that the electricity is supplied to the GB grid. The eligible renewable sources include wind, solar, hydro, biomass, marine, landfill gas and sewage gas. Nuclear energy is not REGO eligible. it’s low-carbon but not classed as renewable so it sits outside the scheme. Nuclear energy is covered separately under low-carbon contracts and the CfD arrangements.

Are there any disadvantages of REGOs?

The REGO scheme has taken criticism, much of it centred on the idea of “greenwashing”, which is shorthand for businesses making themselves look greener than they really are.

A lot of that pushback comes back to the fact that the REGO certificates are not always tied to the original renewable energy that was generated. This is something that is not always made clear to consumers.

For example, a consumer may believe their electricity is fully clean. However, on a day with very little wind or sun, a large source of the electricity they are actually consuming is coming from fossil generation, even though their tariff is marketed as green and backed by REGOs. That kind of disconnect prompted OVO Energy and Good Energy to publicly step away from the scheme, arguing instead for one where the renewable claim is properly linked to renewable sources and evidenced. OVO in particular announced in April 2023 that it would back its tariffs through direct Power Purchase Agreements with renewable generators rather than purchasing standalone REGOs, becoming the first major UK supplier to take that step.

Part of the issue is that the system makes no formal distinction between an unbundled REGO, where the certificate has been picked up on its own, and a bundled one, where it travels with the related power. From our perspective bundled REGOs tend to represent a more credible way of buying renewable energy.

Where the REGOs are sourced is another key consideration as an energy supply contract may come from a mix of generation sources, including biomass along with natural renewables, such as wind, hydro and solar. Because of this, many suppliers now offer upgraded REGOs from a single source, and in some cases you can even narrow it down by geography. This offers stronger evidence against greenwashing claims, as it allows businesses to demonstrate exactly which renewable assets are backing their tariff rather than relying on anonymous certificates pulled from the secondary market.

One of the more interesting recent developments is time-matched REGOs. Historically, REGOs have only been matched to consumption on an annual basis, meaning a business’s total green claim for the year is simply set against the total renewable generation across the year. Time-matched REGOs go further by aligning consumption with renewable generation on a half-hourly or hourly basis, giving a much more accurate picture of when a customer’s energy use was genuinely covered by renewables. The trade-off is that tighter matching tends to make pricing more volatile, simply because there will be moments when the market is undersupplied with renewable energy to cover the demand.

Need help choosing the right renewable energy contract for your business?

 REGOs, bundled certificates, PPAs and time-matched renewable supply options can all play a role in supporting your sustainability goals, but the right approach depends on your usage profile, budget, carbon reporting needs and appetite for long-term commitment. Professional Energy Services can advise you on making the right choice for your business with our renewable energy procurement services, and also assessing the credibility of supplier claims, and identifying opportunities to reduce costs while strengthening your Net Zero position. Our energy consultancy services give businesses the clarity and confidence they need to procure renewable energy in a way that is commercially sound, transparent and aligned with their wider environmental objectives.