Six inputs, instant answer: annual generation, self-use savings and export income for your setup — with every assumption shown, not buried. Then get the roof surveyed properly.
Estimate annual savings from self-use plus export income. Assumptions shown below the result — adjust inputs to your home.
Indicative estimate using UK yield averages — roof survey confirms the real numbers.
UK systems yield roughly 850–950 kWh per kWp annually on unshaded south-facing roofs; we use 900 and scale for orientation. Self-use depends on daytime occupancy — the biggest single variable households control. Export income uses your SEG rate; see current SEG guidance to make sure you’re not on a default few-pence tariff.
In order: your import rate (every self-used kWh saves the full rate), occupancy/self-use share, orientation, then export rate. Shading isn’t modelled here — a real survey with irradiance measurement handles that, and optimiser/micro-inverter choices follow from it.
Costs in 2026: ~£5,000–£7,000 for 4kWp, ~£7,000–£9,500 for 6kWp, 0% VAT applied. Against calculator savings of £600–£1,100/yr for typical homes, payback runs 6–10 years on 25-year warrantied panels. Check grant routes first — WH:LG funded solar in 38% of its installations to end-July 2026.
Facts checked 21 August 2026. We link to official sources and show when facts were last verified. If a scheme changes, we update the page.
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