How Many Solar Panels Do I Need for My Roof?

How Many Panels by House Size

• 1–2 bed flat/house: 4–6 panels (1.6–2.4kW), ~7–10m² roof
• 3 bed semi/terrace: 10–12 panels (3.5–4kW), ~17–20m² roof
• 4–5 bed detached: 14–16 panels (5–6kW), ~24–27m² roof

How the Sizing Works

The number of panels depends on your annual electricity usage and how much generation you can expect:

• Average UK household uses 3,500–4,000 kWh/year
• 1kWp of solar generates 800–1,000 kWh/year in the UK
• So a 4kWp system generates ~3,200–4,000 kWh/year
• 4kWp ÷ 0.4kW per panel = 10 panels

Roof Orientation and Pitch

• South-facing, 30–40° pitch: 100% efficiency (ideal)
• East or west-facing: ~85% of ideal output
• Flat roof (with tilted mounts): ~90% of ideal
• North-facing: Not recommended — only ~50–60%

Cost Guide (2026)

• 3–4kW system: £5,000–7,000 installed
• 5–6kW system: £7,000–9,000 installed
• With battery storage: Add £2,500–5,000

Solar panels are VAT-free (0% VAT) for residential installations in the UK until at least March 2027.

Payback Period

At current electricity prices (~28p/kWh), a typical 4kW system saves £700–900/year through self-consumption and export payments. Payback period is typically 6–9 years.