How many solar panels does a UK house need?
Monthly use ÷ sun hours ÷ derate, then ÷ panel wattage. Most UK homes need 10 to 14 panels at 400W. A 300 kWh a month home needs 12 panels (4.8 kW) at 2.7 peak sun hours. Larger homes, and homes with electric heating or an EV, need more.
Allow about 18 sq ft (1.7 m²) per panel including spacing: 12 panels need about 216 sq ft (20 m²) of usable roof. South-facing roofs are best; east-west split roofs also work well, producing a flatter curve across the day.
Your bill decides the number, not your house size. Check your last 12 months of bills for your real average — a single winter month will overstate what you need.
Size it fully with the UK solar panel calculator, or price it with the UK cost calculator.