Go renewable, keep up to £400 in your pocket

Five main sources: wind, solar, hydro, geothermal and biomass. Nuclear is low-carbon but not renewable because uranium fuel is finite. Suppliers must use Ofgem-registered REGO certificates to call any tariff "100% renewable".

It depends. A tariff matched to REGO certificates only means the supplier has bought paperwork — not necessarily extra clean energy. A tariff matched to direct Power Purchase Agreements (PPAs) with wind or solar farms is much stronger. Our best green supplier guide separates the two.

For most UK homes, yes. A 4 kW system costs around £6,000–£8,000 installed and can save / earn back £700 a year through self-consumption and the Smart Export Guarantee. Payback typically sits at 10–14 years. The energy harvesting guide runs the maths.

Green gas (biomethane) is produced by fermenting food and farm waste, then upgraded to grid-quality methane and injected into the gas network. It is chemically identical to natural gas but carbon-neutral. See the green gas guide.

Yes — through the Smart Export Guarantee (SEG). Every UK supplier with 150,000+ customers is required to offer a price for every kWh you export, with rates running from around 1 p / kWh to over 15 p / kWh depending on the supplier.

No, but it is part of the low-carbon mix. Nuclear produces almost no CO₂ at the point of generation but the uranium fuel is finite and radioactive waste must be managed. The UK plan keeps nuclear central to its 2050 strategy alongside renewables.