Sizing

Solar Panel Calculator UK

By Shehzad Hussain

Solar panel calculator for the UK: size your system from your bill with UK sun hours (2.7), UK electricity prices and £ costs.

Your electricity use

How do you want to enter your usage?

Monthly electricity bill (£)

Electricity rate (£ per kWh)

Your roof & system

Peak sun hours per day

Panel wattage (W)

System losses (derate, 0–1)

Installed cost per watt (£)

Estimates only. System size, production, savings and payback are estimates based on the assumptions shown with your results — real output depends on your roof, shading, weather and local rates. UK figures use typical UK sun hours and prices; export payments under the Smart Export Guarantee vary by supplier. Incentives vary by state/country and change — check current local rules. Get a quote from an MCS-certified local installer before deciding.

How the UK solar calculator works

Same formula, UK numbers. The calculator uses UK defaults: 2.7 peak sun hours a day, £0.24 per kWh, and about £1.50 per watt installed. A UK home using 300 kWh a month needs 10 ÷ 2.7 ÷ 0.8 = 4.63 kW — 12 standard 400W panels, a 4.8 kW system covering about 216 sq ft (20 m²) of roof.

Yearly production is about 3,784 kWh. At £0.24 per kWh, estimated savings are about £886 a year, and the £7,200 system pays back in about 8.1 years. UK payback is often shorter than US payback because UK electricity is expensive relative to system cost.

Panels work on daylight, not heat, so the UK climate is fine for solar — output is highest in late spring and summer and lowest in December and January. The monthly chart shows that seasonal swing for your system.

Price your system with the UK cost calculator, or check your panel count with the UK how-many calculator.

How to use the Solar Panel Calculator UK

Enter your monthly electricity bill in £ (the average UK home pays about £72 a month for 300 kWh).
Keep peak sun hours at 2.7 — the UK average — unless you know your local figure.
Set your electricity rate (£0.24 per kWh is the default) and panel wattage (400W).
Read off your system size, panel count, roof area, yearly production and estimated cost in £.

Frequently asked questions

How many solar panels do I need in the UK?

A UK home using 300 kWh a month needs about 12 panels at 400W — a 4.8 kW system covering about 216 sq ft of roof — at 2.7 peak sun hours. UK systems are smaller than US ones because UK homes use less electricity and get less sun.

How much do solar panels cost in the UK?

At about £1.50 per watt installed, a 4.8 kW system costs about £7,200. A typical 4 kW UK system runs about £5,000 to £8,000 depending on roof and installer. Get three local MCS-certified quotes.

How long is solar payback in the UK?

For the 300 kWh a month example, estimated savings are about £886 a year, giving a simple payback of about 8.1 years. UK payback is often shorter than US payback because UK electricity is expensive relative to system cost.

Do solar panels work in the UK weather?

Yes — panels work on daylight, not heat, and the UK still averages about 2.7 peak sun hours a day. Output is highest in late spring and summer and lowest in December and January. The calculator shows monthly production so you can see the seasonal swing.

More calculators from the same category.

How the UK solar calculator works

How to use the Solar Panel Calculator UK

Frequently asked questions

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