Savings depend on system size, your export tariff and — most of all — how much of the generation you use rather than export. These broad figures use the 1 October to 31 December 2026 price cap of 26.32p/kWh.
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.
A household that is out all day and uses little electricity sits nearer the lower end. We will not present a household-specific figure until we have looked at the roof, annual consumption and tariff. The free savings report is built on your numbers, not a best-case headline.
