Savings depend on how much of your solar you use yourself, which depends on how much electricity you use and when. These broad ranges use the 1 October to 31 December 2026 Ofgem price cap of 26.32p/kWh (no VAT on household electricity from 1 October 2026 to 31 March 2027).
How the figures are worked out (a 5 kW system making about 4,000 kWh a year):
- Bill saving: £260–£530 a year. Each unit of solar you use yourself is a unit you don't buy at 26.32p/kWh. The low end is a typical home using 2,500 kWh a year (Ofgem), which uses about 1,000 kWh of its solar directly. The high end is a home using about 5,000 kWh, for example with an EV or heat pump, which uses about 2,000 kWh.
- Export income: £80–£360 a year. The rest is exported, paid at 4.1p/kWh on an open export tariff up to 12p/kWh on a tariff that needs Octopus as your electricity supplier. This is a payment to you, not a lower bill. A home that uses less electricity has more left to export, so the top of this range is a typical home on the higher rate and the bottom a higher-use home on the open rate.
- Total benefit: £390–£770 a year, bill saving plus export income, worked out for each household on each export rate.
- A battery adds £60–£200 a year in our worked examples. It stores some daytime surplus, loses some in the round trip and gives up the export payment on what it stores. At £5,000–£8,000 (Energy Saving Trust), it doesn't pay for itself within its expected life in these worked examples.
- The standing charge (54.83p a day at the cap) is unaffected and is not included in any figure.
The direct-use shares are illustrative assumptions, not measurements: a household cannot use more solar than it uses electricity, and generation peaks in summer while use peaks on winter evenings.
What affects your savings:
- System size — a larger array generates more electricity
- Roof orientation and shading — south-facing is ideal, but east/west split roofs can also work well
- Your energy habits — working from home, an EV or an electric shower can raise how much solar you use
- Export tariff — the rate you are paid for exported electricity varies widely between tariffs
We provide a free, no-obligation savings report based on your roof, usage and tariff before you commit to anything.
