Size Your System in 5 Steps

How many solar panels do I need?

Size your solar system in 5 steps: STEP 1 — ANNUAL CONSUMPTION: Check your electricity bill for annual kWh. Or estimate: 1-bed flat 1,800 kWh. 2-bed 2,500. 3-bed 2,900. 4-bed 3,500. 5-bed 4,500. + EV: add 2,000. + Heat pump: add 4,500. STEP 2 — PANELS NEEDED: Divide annual kWh by 380 (annual output per panel at UK average). Result = minimum panels. STEP 3 — ROOF SPACE: Each panel needs ~2m². Measure usable roof: width × slope height. Subtract chimneys, skylights. Divide by 2 = max panels. STEP 4 — ORIENTATION ADJUSTMENT: South: use Step 2 result. East/West: multiply by 1.2. South-East/West: multiply by 1.05. STEP 5 — ROUND UP: Always round up to the nearest whole panel. Bigger is better — marginal cost is small, marginal benefit lasts 25 years. QUICK LOOKUP: 2-bed: 6-8 panels (2.4-3.2kW). 3-bed: 8-12 panels (3.2-4.8kW). 4-bed: 10-14 panels (4-5.6kW). 5-bed: 14-20 panels (5.6-8kW). Sources: PVGIS UK average yield, BEIS consumption data, EST.