Every unit of electricity on the national grid is mixed together. You cannot physically choose the electrons that arrive at your meter, so a green tariff works differently: it changes where your money goes and how much renewable generation is bought on your behalf. In practice, your supplier matches some or all of the electricity you use with renewable generation — typically wind, solar, hydro or a share of biomass — and buys the certificates to prove it.
Those certificates are called Renewable Energy Guarantees of Origin, usually shortened to REGOs. For every megawatt hour of renewable electricity generated, one REGO is issued. When a supplier buys REGOs to cover your annual usage, it can describe the tariff as renewable. That is a legitimate system, but it is also why two tariffs that both say "100% green" can be very different in the real world.
Under UK rules, every supplier must publish its fuel mix — the breakdown of sources behind the electricity it sells. This is your first practical check. Look at the renewables percentage and compare it with the national average, which sits at roughly 40–45% renewable in recent years, with the rest made up of gas, nuclear and a small amount of coal.
A supplier claiming 100% renewable should show 100% in its disclosed fuel mix. If the numbers do not line up, ask why. Some suppliers legitimately use a small amount of non-renewable electricity for grid losses or backup, and honest ones tend to say so.
The certificate system has a well-known weakness. A supplier can buy cheap REGOs from wind farms built years ago, attach them to a standard tariff, and call it green — without funding a single new turbine. It is legal, but the climate benefit is thin. Stronger tariffs look like this:
If a tariff is cheap and green, it is worth asking how. There is often an honest answer — a supplier with low overheads and its own generation — but sometimes there is not.
Switching is straightforward and usually takes around three weeks, with no interruption to supply. Work through it in this order:
A green tariff changes the source of your electricity, but it does not shrink your bill or your footprint on its own. Reducing how much you use is still the cheapest and cleanest option, and it makes any tariff go further. Draught-proofing doors and windows, topping up loft insulation to 270mm, fitting LED bulbs and setting your heating to 18–19°C are low-cost moves that pay back quickly.
For bigger steps, consider a smart thermostat with zoned heating, solar panels if your roof faces roughly south, and — when your boiler reaches the end of its life — a heat pump. Because most UK homes use far more energy for heating and hot water than for electricity, cutting gas demand often matters more than the tariff itself.
Before signing, ask the supplier directly: what percentage of my electricity is matched by renewable generation, and is it backed by REGOs? Do you buy from specific generators or the open certificate market? Are you investing in new renewable capacity? What is the exit fee, and does the tariff support community energy?
A good supplier will answer these plainly. A vague one is telling you something useful too. Combine a well-chosen tariff with modest efficiency improvements, and your home will be doing more for the grid than most — which is a quiet, practical sort of progress worth having.
Low Carbon Living shares practical, down-to-earth guidance on practical low-carbon living and sustainability for uk homes and communities for readers across the UK.
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