What is a REGO certificate?

What is a REGO certificate?

When you sign up for a renewable energy tariff, you might picture wind turbines and solar panels sending power straight to your home. In reality, all electricity mixes together once it enters the National Grid. To track how much renewable electricity is actually generated, the UK uses a system called Renewable Energy Guarantees of Origin, or REGO certificates. Although renewable electricity is often described as zero-carbon, the scheme tracks eligible renewable generation rather than all zero-carbon sources.

These certificates act as a tracking system. They prove that a specific amount of renewable electricity was generated and added to the grid. Energy suppliers buy these certificates so they can officially label their tariffs as green. However, the system has flaws. Because certificates can be traded separately from the electricity itself, a supplier can buy power generated by fossil fuels, buy REGO certificates on the side, and still legally market their tariff as 100% renewable.

How the REGO scheme works

To understand REGO certificates, it helps to understand how the UK electricity network operates. The National Grid is like a giant pool. Generators pump water into the pool, and households draw water out. Once the water is in the pool, you cannot separate the clean water from the dirty water. When a wind farm or solar park generates electricity, that power goes into the grid and mixes with electricity from gas power stations and nuclear plants. When you turn on your television, the electricity flowing into your home is a mix of all these sources.

Because suppliers cannot route green electrons directly to your house, the industry needs a paper trail to track renewable generation. This is where REGO certificates come in. The scheme is run by the energy regulator, Ofgem, on behalf of the Department for Energy Security and Net Zero. Every time an accredited renewable generator produces one megawatt-hour (MWh) of electricity, Ofgem issues them one REGO certificate.

Generators can then sell these certificates to energy suppliers. Suppliers collect the certificates to prove to Ofgem that they have bought enough renewable energy to match the amount their customers have used. In May 2025, Ofgem launched a new Renewable Electricity Register to manage these certificates and keep track of who owns them.

The cost of REGOs and your energy bill

You might assume that a 100% renewable tariff costs a lot more to run than a standard tariff. In the past, green tariffs often came with a premium price tag. Today, the cost of the certificates themselves is remarkably low. As of mid-2026, a single REGO certificate costs a supplier between £1 and £2. Because one certificate covers one megawatt-hour of electricity, we can calculate exactly how much it costs to make an average household tariff green.

According to Ofgem's typical domestic consumption values, updated in July 2026, an average UK household uses roughly 2.5 MWh (2,511 kWh) of electricity a year. This means a supplier only needs to spend between £2.50 and £5.00 a year to buy enough REGOs to cover a typical home. While some older sources claim a certificate costs as little as 50p, that figure is outdated. However, the current price is still low enough that almost every major UK supplier offers a 100% renewable tariff, often priced at or below the standard price cap.

The market for these certificates has seen massive price changes over the last few years. Historically, they cost just a few pennies. In 2023, prices spiked to record highs of over £15 to £25 per MWh. This sudden jump happened because of a tightening in supply and the failure of a major government renewable funding round. Since that peak, prices crashed by up to 97%, falling to around 30p to 77p per MWh in early 2025, before settling at their current level of £1 to £2 in the summer of 2026.

The greenwashing loophole: Unbundled certificates

The biggest criticism of the REGO scheme is that it allows for a practice often described as greenwashing. This happens because the certificates do not have to be sold alongside the electricity they represent. When a wind farm generates power, it has two things it can sell: the physical electricity, and the REGO certificate. It can sell both of these together to an energy supplier. Or, it can sell the physical electricity to one buyer, and sell the REGO certificate to a completely different buyer.

This creates a loophole. An energy supplier can buy its wholesale electricity from the cheapest available source. Because coal has been effectively phased out of the UK electricity mix, this non-renewable power is now typically gas or nuclear. The supplier can then go to the certificate market and buy cheap unbundled REGOs. By matching the gas electricity with the unbundled certificates, the supplier can legally claim that its tariff is 100% renewable.

For the consumer, this means the money you pay for your energy is largely going to fossil fuel generators, while only a tiny fraction goes to renewable generators. While zero-carbon energy generators do receive government subsidies, REGOs provide a vital extra income stream that improves their returns. However, the unbundled system allows suppliers to claim green credentials without actually supporting the renewable energy industry in a meaningful way.

Three ways suppliers source green energy

Because the rules allow for different ways of buying green power, energy suppliers generally fall into one of three categories. If you want to make sure your money is supporting the environment, it helps to know which approach your supplier takes.

The first approach, unbundled trading, is the cheapest way to offer a green tariff, but it does the least to support new renewable generation. The second approach, buying bundled energy, usually involves contracts called Power Purchase Agreements. This gives the independent generator a reliable income, which helps them maintain their sites and plan for the future.

The third and most direct approach is when a supplier builds and runs its own renewable generation. Some suppliers own their own wind farms and solar parks. They generate the power themselves, feed it into the grid, and claim the REGOs. When you pay your bill to one of these suppliers, you are funding a company that owns and operates renewable generation in the UK.

Additionality and why it matters

When experts talk about green energy, they often use the word additionality. Additionality means that your choice of tariff has directly resulted in more renewable energy being added to the grid than would have existed otherwise. If you buy a tariff backed by unbundled REGOs, there is almost no additionality. The wind farm that sold the certificate was already built and already generating power. Your few pounds a year for the certificate does not provide enough money to fund new turbines.

If additionality matters to you, look for clear evidence that a supplier's tariff or investments support new renewable projects. When a supplier uses the money from your bills to build a new solar farm, your choice has directly added new green power to the grid. Even large suppliers that own generation assets usually have to rely on a mix of their own power, Power Purchase Agreements, and some certificates to cover their entire customer base.

This issue is becoming more important for businesses as well as households. Corporate reporting and wider sustainability commitments mean many companies want clearer evidence of the impact of their energy choices. As a result, many businesses are moving away from unbundled REGOs and demanding contracts that directly fund new renewable projects.

How Brexit changed the certificate system

The REGO scheme was originally set up to meet European Union rules. The EU required all member states to have a system in place to track renewable energy. For many years, the UK system was linked to the European system. Suppliers in the UK used to be able to buy European Guarantees of Origin to cover the electricity they supplied to British homes. This meant a UK supplier could buy certificates from a hydroelectric dam in Norway to back up a green tariff sold in Scotland or England.

This changed after Brexit. On 1 January 2021, the EU stopped recognising UK REGOs. Later, the UK government decided to sever the link in the other direction. Since April 2023, Ofgem no longer allows UK suppliers to use European certificates to prove their domestic fuel mix. For Great Britain's Fuel Mix Disclosure, the scheme is now separate from EU Guarantees of Origin. This change was a major reason why REGO prices spiked in 2023, as suppliers could no longer rely on cheap European certificates and had to compete for a limited supply of UK ones.

The Fuel Mix Disclosure

The main reason suppliers buy REGOs is to comply with a rule called the Fuel Mix Disclosure. Ofgem requires all licensed electricity suppliers in Great Britain and Northern Ireland to publish a breakdown of where their electricity comes from. Every year, suppliers must tell their customers exactly what percentage of their power came from renewables, coal, gas, and nuclear. They must also publish the carbon emissions associated with their supply.

To claim that a certain percentage of their power is renewable, the supplier must hold the equivalent number of REGO certificates. When you look at a supplier's website, you will usually find their Fuel Mix Disclosure clearly displayed, often in a pie chart. If a supplier does not hold enough evidence to cover all of its supply, it must apply the Residual Fuel Mix to the unmatched portion. This is different from the UK Average Fuel Mix.

Should you choose a REGO-backed tariff?

Deciding whether to sign up for a green tariff depends on what you want to achieve. If your goal is simply to have a tariff that matches your usage with renewable certificates, then almost any 100% renewable tariff will do. These tariffs are widely available and do not usually cost any more than a standard gas-heavy tariff.

However, if you want your energy bills to actively fight climate change, you need to look closer at how the supplier operates. A tariff backed purely by unbundled certificates does very little to change how the UK generates its power. To make a real difference, research the supplier before you switch. Look for companies that openly discuss their Power Purchase Agreements with independent wind and solar farms. Better yet, look for suppliers that invest their profits into building their own green energy sites.

While the REGO system has flaws, it remains the main certificate scheme used to evidence renewable electricity for Fuel Mix Disclosure. By understanding how it works, you can look past the marketing claims and choose a supplier that matches your environmental goals.