How Many Solar Panels Do I Need? A UK Sizing Guide

“How many panels do I need?” is usually the first question we hear — and the honest answer is that it depends on four things: how much electricity you use, how much roof you have, which way it faces, and what you want the system to achieve.

Start with your usage, not your roof

A typical UK home uses around 2,700–4,100 kWh of electricity a year — more with an EV, a heat pump, or a full house of home workers. A modern 440W panel in the North West generates roughly 330–400 kWh per year depending on aspect and pitch. Divide one by the other and you get a first estimate:

• Low usage (~2,700 kWh): 8–10 panels (3.5–4.4 kWp)
• Average usage (~3,500 kWh): 10–12 panels (4.4–5.3 kWp)
• High usage (~4,500+ kWh): 12–16 panels (5.3–7 kWp)
• EV or heat pump in the mix: 14–16+ panels, and a battery earns its keep

Then check the roof

A panel occupies roughly 2m² of roof. A typical semi-detached roof face takes 8–12 panels; a detached home often carries 14–16 across two faces. Chimneys, velux windows, vents and shading all knock panels off the plan — which is why we design from photographs, satellite imagery and a physical survey rather than a postcode guess.

South-facing is the classic ideal, but don’t write off east–west. A split east/west array generates around 80–85% of a south-facing one, spread more usefully across morning and evening — which matches when most households actually use electricity.

Don’t oversize for export

The Smart Export Guarantee pays 5–15p per exported unit, while grid electricity costs around 24p. Exporting is fine; buying less is better. Beyond a certain size, extra panels mostly generate cheap export rather than offsetting expensive import — unless you add a battery, which soaks up the surplus for evening use and changes the maths entirely.

What matching the system to the house looks like

Two identical families in identical houses can need different systems: one charges an EV overnight on a cheap tariff (battery does the heavy lifting), the other works from home all day (solar self-consumption is already high, battery adds less). This is why our quotes come from an engineer after a real conversation, not from a phone script.

The short answer

For most UK homes: 10–14 panels, around 4.4–6 kWp, usually with a battery. But the right answer for your home takes a survey — ours are free, and there’s no obligation attached.