How many panels does your home need?

Last updated: 3 July 2026 · Written by the ECONEXIS team, MCS-accredited installers.

The right number of panels isn't the biggest number that fits your roof — it's the number that matches how much electricity you actually use. Here's how we size systems, and how to estimate yours before we do it properly.

Start with your usage, not your roof

A typical UK home uses around 2,700–4,200 kWh a year; larger or all-electric homes use more. Find the kWh figure on your bill (or tell us your monthly spend and we'll work it out). A modern 470–480W panel in the South East generates roughly 350–450 kWh a year, depending on orientation and shading.

Quick sizing by monthly bill

• £80–£120/month → usually 10–12 panels (4.7–5.8 kW).
• £120–£180/month → usually 12–16 panels (5.8–7.7 kW).
• £180+/month → 16–20 panels (7.7–9.6 kW), roof permitting.

Real examples from our recent designs: a 10-panel 4.7 kW system generating ~4,500 kWh/yr; a 15-panel 7.2 kW system at ~5,700 kWh/yr; and a 20-panel 9.4 kW system at ~6,200 kWh/yr. Panel count alone isn't the whole story — orientation, pitch and shading move the output, which is why two identical houses can need different designs.

Will they fit? Roof space in plain terms

Each modern panel is roughly 1.9 m². As a rule of thumb, a typical semi's rear roof slope takes 8–12 panels; add a second slope, extension or garage and 14–20 becomes realistic. East-west roofs work well by splitting the array — morning sun one side, afternoon the other. We design around chimneys, velux windows and shading automatically.

Don't forget the export limit

Your electricity network operator (DNO) sets how much your system may export to the grid, which can shape the inverter setup on bigger systems. We handle that entire application for you — here's how DNO approval works.

Get your exact answer free

Send us your address and monthly bill and we'll design your system — panel count, layout on your actual roof, battery sizing, price and savings — usually within 24 hours, free and without obligation, anywhere across Bedfordshire, Hertfordshire, Buckinghamshire, Essex & Kent.Start with our solar page or go straight to your free design.

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