Here’s something that surprises most people when they find out: the electricity in a “100% renewable” tariff isn’t necessarily generated anywhere near when or where you use it. The green label on your energy bill is backed by certificates called REGOs — Renewable Energy Guarantees of Origin — and understanding what those actually mean is worth a few minutes of your time, whether you’re choosing a home tariff or signing a business energy contract.
This isn’t a reason to dismiss green tariffs. But it is a reason to understand what you’re buying.
What a REGO Actually Is
A REGO is a certificate issued by Ofgem for every megawatt-hour of electricity generated by a renewable source: wind, solar, hydro, biomass, and so on. The generator gets one REGO per MWh produced. They can then sell that electricity to the grid (or directly to suppliers) and separately sell or transfer the REGO to whoever wants to claim that the electricity was renewable.
When an energy supplier offers you a “100% renewable” tariff, what they’re typically doing is buying enough REGOs to match your total electricity consumption. If you use 3,000 kWh a year, they retire 3 REGOs (3 x 1 MWh) on your behalf, proving that somewhere, 3 MWh of renewable electricity was generated.
This is sometimes called “certificate-backed” renewable energy, and it’s perfectly legal and Ofgem-regulated. Almost every major UK energy supplier offers tariffs backed this way. British Gas, EDF, E.ON, Octopus, OVO, Scottish Power — all of them offer green tariffs built on REGO certificates.
The Bit That Gets Complicated
The issue, if you’re looking for one, is that the REGO can be bought separately from the electricity. A wind farm generates electricity and REGOs. It sells the electricity to the grid, where it gets mixed with electricity from gas plants, nuclear stations, and everyone else. Then a supplier buys the REGOs separately, often from a different time or location than when you were actually consuming power.
This means the “green” electricity you’re buying and the electricity physically flowing through your sockets are two entirely different things. The electrons are the same electrons either way. But the certificate ensures that somewhere in the system, an equivalent amount of renewable generation occurred.
Critics — particularly among environmental scientists and energy researchers — argue this doesn’t actually reduce fossil fuel generation in any direct way. Whether a renewable generator’s REGO was claimed by a green tariff customer or not, the generator was going to produce that electricity regardless. The REGO doesn’t build new renewable capacity; it just allocates credit for existing generation.
Supporters point out that green tariffs create demand signals that support the economic case for new renewable investment, and that certificate schemes are how every major renewable energy market in Europe works. The UK’s REGO system is broadly equivalent to similar schemes in Germany, France, and the Netherlands.
Both positions have some truth to them. The REGO system isn’t a scam, but it also isn’t the same as directly powering your home from a wind turbine.
What Power Purchase Agreements Actually Mean
Some energy suppliers — Ecotricity, Good Energy, and a few others — go further than REGOs. They sign long-term power purchase agreements (PPAs) directly with specific UK renewable generators, buying both the electricity and the certificates from identifiable sources.
This is a stronger claim. It means the supplier is genuinely contracted to receive electricity from UK wind farms or solar arrays, and the REGOs are matched to actual generators the supplier has a commercial relationship with. The electricity is still mixed in the grid, but the traceability is better.
Good Energy publishes a breakdown of where its electricity comes from — specific farms and generating sites — which is something very few suppliers do. Ecotricity builds and operates its own wind and solar capacity, which is a different model again.
If the provenance of your renewable energy matters to you beyond the certificate, look for suppliers who can demonstrate PPAs with named UK generators rather than just REGO retirement from the wholesale market.
For Businesses: Why REGOs Matter More
For businesses with sustainability reporting obligations, REGOs matter for a specific reason: they provide the documentary evidence that supports Scope 2 (electricity consumption) emissions claims.
Under market-based accounting for greenhouse gas emissions (the framework most large businesses use for annual sustainability reports), you can claim zero Scope 2 emissions for electricity covered by REGOs or equivalent certificates. Without the certificates, you’d have to use the UK grid average emissions factor, which is significantly higher.
This is why corporate renewable energy claims are almost always backed by REGOs (or the equivalent in other countries). The certificates are the audit trail. When a company says “100% of our UK electricity is from renewable sources,” they typically mean they’ve purchased and retired REGOs equivalent to their consumption.
The criticism that applies at the individual consumer level applies here too. But for corporate accounting purposes, the market-based framework is the accepted standard.
Choosing a Green Tariff That Reflects Your Values
If you’re comfortable with the REGO system as it works: almost any supplier’s green tariff will give you the certificate coverage at a competitive price. Octopus Green and similar products from major suppliers are fine.
If you want stronger provenance: look for suppliers with named PPA arrangements or who publish their generation portfolio. Good Energy’s annual “fuel mix disclosure” shows exactly which farms and generators contributed to their supply. The tariffs typically cost a little more, but not dramatically.
If your primary concern is actually decarbonising the grid: consider whether your decisions on demand shifting, battery storage, and EV charging might have a more direct effect than tariff choice alone. Using electricity when renewable generation is high (which Octopus Agile prices reflect directly) reduces the need for gas peaking plants in a way that REGO purchasing doesn’t.
None of this is to say REGOs are worthless — they’re not. They’re the standard mechanism for renewable energy accounting across Europe. But knowing what’s behind the green label on your bill means you can make a more genuinely informed choice about whether it’s enough for your purposes.
Practical note: You can verify your supplier’s REGOs through the ECOES (Electricity Central Online Enquiry Service) registry or by requesting their annual fuel mix disclosure, which all UK licensed suppliers are required to publish. Ofgem’s website has the full requirements.