How Many Solar Panels Do I Need? UK Sizing, Output and Payback in Plain English

The quick answer

Most UK homes land on 10–14 panels (4.3–6.1kW). At today's 435W+ panel sizes, ten panels need roughly 20m² of unshaded roof — a typical semi's south-ish facing side.

What a system actually generates

A 4.3kW system in southern England typically produces ~3,800kWh a year — about a typical home's annual electricity use. But generation is lumpy: glorious in May–August, modest November–January. That mismatch is why the battery question matters more than the panel count.

Orientation and shade, honestly

• South: the ideal. East/west: ~85% of south's output, and an east+west split actually matches household usage better (morning + evening generation). Don't let a non-south roof put you off.
• North: generally not worth it.
• Shade: a chimney's shadow can cost more than a missing panel. Panel-level optimisation deals with partial shade — this is exactly what the survey assesses.

Use it or lose (most of) it

Export pays a few pence per kWh under the Smart Export Guarantee; grid electricity costs 25p+. So the economics reward self-consumption: run the dishwasher at noon, charge the car from the roof (solar-aware charger), and store the excess in a battery for the evening (battery sizing guide).

The payback maths in 2026

Installed solar is 0% VAT until March 2027. A 4.3kW system at £5,995 installed, offsetting and exporting a typical mix, returns roughly £700–£900 a year at current prices — a 7–9 year simple payback on a 25-year asset, faster with a battery and smart tariff, faster still if prices rise. Panels degrade slowly (typically warranted ~87–90% output at year 25).

What's in our installed price

Scaffolding, panel-level design, hybrid (battery-ready) inverter, DNO notification, MCS certification and Smart Export Guarantee registration — the items that quietly go missing from too-cheap quotes. Browse solar systems →