How solar panel savings are estimated

A UK solar PV system generates roughly 950 kWh per year for every kWp installed on a well-sited, south-facing roof — panels facing east/west or split SE/SW generate somewhat less. Electricity you use as it's generated (self-consumption) saves you the full import rate; anything you don't use is exported to the grid and paid at the Smart Export Guarantee (SEG) rate, which is normally lower. A battery lets you store daytime generation to use in the evening, which typically raises self-consumption from around 40% to 70% or more — at an extra upfront cost. Payback is simply the total system cost divided by the annual saving; the 25-year figure assumes today's rates stay flat and ignores gradual panel degradation, so treat both as a rough guide, not a guarantee.