Your roof, in kilowatt-hours and years.

As of 6 October 2026. Every figure below is either a published rate with its source, or an EcoGrid assumption that has not yet been independently verified. Nothing here is your own tariff or a guarantee.

• Generation (EcoGrid assumption): 850 kWh a year per kWp of panels, adjusted for roof direction (south 100%, south-east or south-west 95%, east or west 85%, north 65%) and shading (none 100%, some 90%, heavy 75%). Output falls 0.4% a year.
• Electricity rates: the standard rate is 26.3p a unit, the Ofgem price cap average for electricity from 1 October to 31 December 2026 (source: ofgem.gov.uk). It is an illustrative rate, not your own tariff. The sold-back rate is 15p a unit, an EcoGrid planning figure and not a quoted tariff, and real Smart Export Guarantee rates differ by supplier.
• How much you use yourself (EcoGrid assumption): we simulate a typical day in every month, hour by hour. The panels make power across the day, and your home uses power in a pattern that depends on whether anyone is home (out all day, part of the day or mostly home). Whatever the panels make beyond what the home is using at that moment goes into the battery if you have one, and is otherwise sold back. A larger array on a smaller home therefore sells more back.
• Battery (EcoGrid assumptions, based on published Fox ESS EVO specifications): 95% of its size is usable, 92% comes back out after losses, and it charges and discharges at up to 5 kW. Its capacity fades 2.5% a year and its benefit is counted for 12 years. On a cheap night tariff it also tops up from the grid between midnight and 5am, but only as much as the next day needs. On a peak-export tariff it fills overnight and sells to the grid from 4pm to 7pm.
• Tariffs: Standard is 26.3p a unit all day with export at 15p. Cheap night is 13.89p from midnight to 5am (an EcoGrid planning rate) and 26.3p otherwise, with export at 15p. Peak export follows Octopus Flux in South Scotland, published rates as at September 2026 (source: octopus.energy): import 15.0p (2am to 5am), 25.0p, then 34.9p (4pm to 7pm), and export 4.4p overnight, 9.6p and 27.2p (4pm to 7pm). These are third-party rates that change often, so treat them as illustrative.
• Price rises (EcoGrid assumption): electricity prices rise 5% a year. Figures cover 25 years. The ranges shown also include prices staying flat.
• About the ranges: each range covers prices rising 5% a year or staying flat, and one step more or less time at home than you chose. The other assumptions on this list are not varied in the range.
• Prices: our starting prices by panel count and battery size, with a discount when you have solar and a battery together. The EV charger is from £1,695 fitted. Solar and battery installs at a home are 0% VAT until 31 March 2027 (HMRC).

Export payments are paid through the Smart Export Guarantee, which needs an MCS-certified installation. These are estimates, not guarantees: real savings depend on your usage, tariff, roof, shading and future energy prices. Every figure is listed on our estimate methodology page.