What a renewable energy tariff really means

When you choose a renewable energy tariff, you are not asking for different electrons to flow into your home. The grid mixes everything together. Instead, you pay your supplier to match some or all of your electricity use with renewable generation. That matching happens through certificates and contracts. The result is that the same amount of renewable electricity you use is fed into the grid somewhere else, or that your payment supports renewable projects. It is a bit like buying a train ticket: you cannot prove which seat you sat in, but your ticket ensures the train runs.

Most green tariffs promise to match 100% of your electricity use with renewable sources. Some match only a portion. Others go further and invest in new wind farms or solar arrays. Before you switch, it is worth understanding the difference.

How suppliers verify their green claims

In the UK, the main verification tool is the Renewable Energy Guarantees of Origin, or REGO. Each REGO represents one megawatt-hour of renewable electricity generated. The regulator issues REGOs to generators, who can sell them separately from the actual electricity. Suppliers buy REGOs to cover your usage. When they do, they can legally call the tariff renewable.

But here is the catch: REGOs can be bought without buying the renewable electricity itself. A supplier might buy cheap REGOs from an old hydro plant while selling you electricity from the general grid mix. That is allowed, but it does little to support new renewable capacity. A stronger claim is when a supplier buys both the electricity and the REGOs from the same source, or when it owns or contracts directly with generators. Some tariffs also guarantee that a portion of your payment goes to building new renewable projects. That is called additionality.

The difference between matching and additionality

Matching means your usage is matched with renewable generation, but it may not lead to any new renewable energy being built. Additionality means your money helps bring new renewable capacity online. Most tariffs only match. A few offer additionality. If you want your tariff to make a real difference, ask about additionality.

• REGO-backed tariffs match existing renewable output. They are cheap and common.
• Direct supply tariffs mean your supplier buys from a specific wind farm, solar array, or hydro scheme.
• Green gas tariffs use biomethane, but supply is limited and often more expensive.
• Investment tariffs promise to fund new renewable generation, sometimes through a separate levy.

No single option is perfect. But knowing what you are buying helps you avoid greenwashing.

Questions to ask before you switch

When you compare tariffs, do not just look at the headline price. Ask these questions directly. A good supplier will answer clearly.

• Is the tariff 100% renewable, and how is that verified?
• Are the REGOs retired on my behalf, so they cannot be sold again?
• Does the supplier own or contract with the generators, or buy certificates separately?
• Is there a separate charge for green certificates, and does that affect the unit rate?
• What happens if I use more or less electricity than expected?
• Does the tariff include gas, and if so, is the gas green?
• Are there exit fees if I switch again?

Also check the standing charge and unit rate. A green tariff with a very high standing charge might cost you more than a standard tariff, even if the unit rate looks good.

Reading the fuel mix disclosure

Every UK supplier must publish a fuel mix disclosure. It shows the mix of sources for the electricity they supplied in the previous year. That includes coal, gas, nuclear, renewables, and other sources. But be careful: the fuel mix is a company-wide average. It is not specific to your tariff. So a supplier with a relatively dirty overall mix can still offer a 100% renewable tariff. Check the tariff-specific details, not just the company average.

Also think about when you use electricity. If you charge an electric car overnight or run a heat pump, you might want a tariff that matches renewable generation at those times. Some smart tariffs do this by linking your usage to periods when wind or solar output is high. That can reduce your carbon footprint and your bill.

Making a practical choice for your home

Start with your own usage. Find your annual electricity use in kilowatt-hours on your bill. Then compare tariffs using that figure, not just the headline rate. Decide whether you care most about matching, additionality, or price. If additionality matters, ask for evidence. A genuine green tariff will be transparent about its sourcing and verification.

Remember that energy efficiency comes first. Reducing waste is often cheaper and greener than any tariff. Insulate your loft and walls, draught-proof windows and doors, use efficient appliances, and set your heating controls wisely. A smart meter can help you see where you are using power. Then choose a renewable tariff that aligns with your values.

Finally, consider the bigger picture. Renewable tariffs are one part of a low-carbon home. If you have the budget and the right property, solar panels, battery storage, or a heat pump can cut your reliance on the grid. But whatever you do, ask questions, read the small print, and choose a tariff that is honest about how it verifies its green claims.