Summary: A renewable energy tariff doesn't always mean the electricity flowing into your home was generated from wind, solar or hydro. Suppliers can label a tariff "100% renewable" simply by buying Renewable Energy Guarantee of Origin (REGO) certificates to match their customers' usage - even if the energy itself came from fossil fuels. To genuinely lower your carbon footprint, choose a supplier that buys both the electricity and the REGO directly from renewable generators, such as Octopus Energy, Ecotricity, Good Energy or 100 Green.
A lot of us want to be greener and do our part to reduce emissions at home. When it comes to the gas and electricity we use, though, it can be hard to know where to start. Most UK energy suppliers now advertise at least one tariff as "green" or "100% renewable" - but a renewable energy tariff doesn't always mean what you'd expect.
This guide explains exactly what a renewable energy tariff is, how REGO certificates work, why some "green" tariffs are accused of greenwashing, and which UK suppliers are the genuinely greenest in 2026.
Wherever your energy comes from, lowering your consumption is the single biggest thing you can do for both the planet and your bills. Here are more than 100 ways to cut your gas and electricity usage at home.
What is renewable energy?
Renewable energy is electricity (or heat) generated from natural resources that won't run out on any human timescale. The traditional way of generating power - burning fossil fuels like coal and gas - relies on finite resources and produces large volumes of greenhouse gases such as carbon dioxide, nitrous oxide, sulphur dioxide and methane. These gases trap heat in the atmosphere and worsen air quality.
Renewable generation, on the other hand, harnesses forces that nature replenishes naturally:
Solar. Photovoltaic panels convert sunlight directly into electricity.
Wind. Onshore and offshore turbines turn moving air into power - the UK's single biggest renewable source.
Hydropower. Generators driven by flowing water from rivers, dams or reservoirs.
Geothermal. Heat from beneath the Earth's surface is used for both electricity and direct heating.
Tidal and wave power. Generators that capture the movement of the ocean to produce electricity.
Biomass. Organic material (wood pellets, agricultural waste) burned for energy - classed as renewable, though more controversial than wind or solar.
In 2024, 50.8% of the UK's electricity came from renewable sources - the first full year renewables generated more power than fossil fuels.
What is a renewable energy tariff?
A renewable energy tariff is a domestic gas or electricity plan that your supplier markets as being matched, in whole or in part, to renewable generation. In practice, the electricity flowing through your wires is identical to your neighbour's - the National Grid mixes power from every source together. What changes is the accounting behind the scenes.
On a typical green electricity tariff, your supplier promises that for every unit of electricity you use, an equivalent unit of renewable generation has been added to the grid somewhere in the UK. They prove this by holding a Renewable Energy Guarantee of Origin certificate - one for every megawatt-hour you consume.
That sounds robust. The problem is that the rules around REGOs are looser than most customers assume.
How REGO certificates actually work
A Renewable Energy Guarantee of Origin certificate is issued by Ofgem for every megawatt-hour of electricity generated from a renewable source in the UK. Each REGO is essentially a receipt: it proves that one unit of renewable power entered the grid.
In an ideal world, REGOs would always travel with the electricity they represent. In reality, generators are allowed to sell the electricity and the REGO separately. A wind farm can sell its power to one buyer (say, a fossil-fuel-heavy supplier) and its REGOs to a completely different buyer.
This means a supplier can buy cheap electricity on the wholesale market - much of it generated by burning gas - and then buy spare REGOs in bulk to "match" that energy on paper. The customer sees a "100% renewable" label; the supplier has done nothing to fund new renewable generation.
This practice is sometimes called "greenwashing" by critics. The Centre for Sustainable Energy explains the REGO loophole in detail, and Ofgem has been consulting on tightening the rules since 2024.
A REGO can be sold for as little as 50p per megawatt-hour - meaning a supplier can label a year of household electricity as "100% green" for under £2 per customer, without buying any renewable power directly.
The three types of "green" tariff (and how they differ)
Not every renewable energy tariff is created equal. Most fall into one of three broad categories:
How different "green" tariffs source their electricity | ||
Tariff type | What it actually buys | Real impact on emissions |
|---|---|---|
REGO-only ("matched") | Wholesale electricity (often fossil) plus separately bought REGO certificates | Minimal - no new renewable generation is funded |
Power Purchase Agreement (PPA) | Electricity bought directly from a named wind, solar or hydro generator under a long-term contract | High - directly supports new and existing renewables |
Owned generation | Supplier generates its own renewable electricity from assets it owns | Highest - the supplier is building the renewables itself |
When you're choosing a renewable energy tariff, the question to ask is which of these three categories your supplier falls into. If they only buy REGOs, your money isn't really driving the transition.
Which UK energy suppliers are the greenest?
The greenest UK suppliers are the ones that buy both renewable electricity and the matching REGO directly from generators (PPAs), or generate their own. Independent rankings by Uswitch, Which?, and the energy regulator Ofgem consistently put the same names at the top:
Octopus Energy. The UK's largest renewable supplier. Generates and invests in its own solar and wind generation, and its smart tariffs (Agile, Go, Cosy) reward customers for using electricity when renewable output is high.
Ecotricity. Builds its own wind and solar farms and reinvests profits into new renewable infrastructure. Also offers Britain's only certified green gas tariff that includes biogas.
Good Energy. Buys directly from a network of around 2,000 small independent UK renewable generators via long-term PPAs.
100 Green (formerly Green Energy UK). The only UK supplier to offer a tariff that is 100% green gas as well as 100% green electricity.
The picture is murkier with the Big Six. Several offer tariffs branded as "100% renewable electricity" but rely heavily on REGOs rather than directly funding new generation. If the marketing copy mentions "matched" or "backed by" REGOs without explaining where the underlying power comes from, that's a sign to dig deeper.
What about gas?
This is where most "green" tariffs fall down. A renewable energy tariff usually refers to electricity only - the gas you use to heat your home and cook is almost always fossil natural gas, regardless of which tariff you're on.
A small number of suppliers (notably Ecotricity, Green Energy UK and Bulb's legacy customers under Octopus) offer "green gas" tariffs, which include a percentage of biomethane - methane produced from food waste, sewage or agricultural residue. Even on these tariffs, the green gas portion is typically only 10-15% of total supply, with the rest matched via offsets such as tree planting or carbon credits.
If reducing the carbon footprint of your heating matters to you, the bigger lever is the heating system itself: replacing a gas boiler with a heat pump can cut household heating emissions by around 65%, according to the Energy Saving Trust.
How to choose a genuinely green tariff
Before you switch, run any prospective renewable energy tariff through these five questions:
1. Does the supplier own or contract its own generation?
The greenest suppliers either build their own wind and solar farms or have long-term Power Purchase Agreements with named generators. If a supplier can't answer where their renewable electricity actually comes from, the tariff is almost certainly REGO-matched only.
2. Is the green claim verified by a third party?
Ofgem's Fuel Mix Disclosure data is published annually and shows exactly how much of each supplier's electricity came from renewables, nuclear, gas and coal. Suppliers that score highly on Fuel Mix tend to be the genuine article.
3. Does the tariff include gas, and is the gas green?
If you have a gas connection, check whether the tariff includes any green gas. Most don't. Knowing this upfront avoids the surprise of an "all green" tariff that turns out to be electricity only.
4. What's the price compared to a standard tariff?
Genuinely green tariffs are sometimes a few pounds a month more expensive because directly contracted renewable electricity costs more to procure than wholesale gas-fired power. If a "100% renewable" tariff is significantly cheaper than its standard equivalent, that's often a sign it's REGO-matched.
5. Where does the supplier reinvest its profits?
Suppliers like Ecotricity publish how much they spend per customer per year on new renewable infrastructure. That figure is one of the clearest signals that your bill is doing more than just keeping your lights on.
Is switching to a renewable energy tariff worth it?
If you choose carefully, yes. Switching to a genuinely renewable energy tariff means your money goes toward building new wind, solar and hydro capacity, which displaces fossil-fuel generation on the grid over time. The carbon footprint reduction for a typical UK household on a PPA-backed renewable electricity tariff is around 1.5 tonnes of CO2 per year - roughly the same as not taking a return flight from London to New York.
If you sign up for a REGO-only tariff, the carbon saving is much smaller. You're not increasing renewable generation on the grid; you're just claiming credit for power that would have been generated anyway.
The good news is that switching is straightforward, free, and takes about ten minutes. There's no interruption to your supply - the same wires, the same meter, the same power. Only the company you pay and the accounting behind it changes.
Questions about renewable energy tariffs
Is a renewable energy tariff really 100% green?
It depends on how the supplier sources its electricity. If they directly buy renewable power and the matching REGO certificates, then yes - your usage is genuinely matched to renewable generation. If they only buy REGOs separately on the wholesale market, the electricity itself may still come from gas or coal.
What is a REGO certificate?
A Renewable Energy Guarantee of Origin certificate is issued by Ofgem for every megawatt-hour of renewable electricity generated in the UK. Suppliers use REGOs to prove how much renewable energy they're matching to their customers' consumption.
Do renewable energy tariffs cost more?
Genuinely green tariffs are often a few pounds a month more expensive than standard tariffs because long-term contracts with renewable generators cost more than buying mixed wholesale electricity. REGO-only "green" tariffs can sometimes be cheaper than standard tariffs, which is one indicator they're not directly funding new renewables.
Is the electricity in my house actually different on a green tariff?
No. The National Grid mixes electricity from every source - gas, nuclear, wind, solar, imports - and delivers a single supply to every home. The "renewable" element of your tariff is contractual: your supplier promises that an equivalent amount of renewable generation has been added to the grid to match what you've used.
Who is the greenest energy supplier in the UK?
Independent rankings consistently name Octopus Energy, Ecotricity, Good Energy and 100 Green as the greenest UK suppliers. All four buy renewable electricity directly from generators rather than relying solely on REGO certificates.
Is green gas a real thing?
Yes, but it's rare. Green gas (biomethane) is produced from anaerobic digestion of food waste, sewage and farm residue. Even the greenest gas tariffs in the UK typically include only 10-15% biomethane, with the rest matched through carbon offsets.
How do I switch to a renewable energy tariff?
Compare tariffs from suppliers that directly source renewable electricity, check the small print for how the green claim is backed up, and apply online or by phone. Switching takes around ten minutes, and there's no interruption to your supply.
Does switching to a green tariff really reduce my carbon footprint?
If you pick a supplier that funds new or existing renewable generation through Power Purchase Agreements or owns its own assets, switching can reduce your household's electricity-related emissions by around 1.5 tonnes of CO2 a year. A REGO-only tariff has a much smaller impact.
