Free Tools

Solar Panel Calculator UK

Find your home on the satellite map and place panels on your roof one by one, then work out your savings, payback and 25-year return at October 2026 prices.

Last updated: 2 October 2026 · Electricity 26.32p/kWh · Export 12p/kWh

Roof planner · Savings calculator · How it works

Set your roof angle, then click on your roof to place panels. Each square is one 400W panel

Solar panel placed

Avoid chimneys, skylights and the shaded side of dormers

Rotate to match your roof

0°

Drag until the preview panel lines up with your roof's ridge in the satellite view. New panels you place will use this angle.

Roof direction (for sun exposure)

Panels placed

click roof to add

System size

0 kWp

400W panels

Annual generation

0 kWh

per year

Annual saving

£0

typical household

Estimated install cost

£0

fully installed, no battery

Start clicking your roof to place panels. Most UK homes fit 8 to 16.

Each panel is 400W. Generation uses the average yield for your postcode area and assumes no shading. The saving assumes you use 40% of the electricity yourself at 26.32p/kWh and export the rest at 12p/kWh. Install cost is a typical UK price without a battery. Estimates only, not a quote.

Want the full financial breakdown?

The savings calculator below factors in your bill, tariff, export rate, a battery and an EV.

Detailed savings calculator

Postcode-adjusted generation, payback, 25-year return and a month-by-month chart. Once you have your numbers, see our best solar panels guide for the brands installers will quote you.

Your location Enter your postcode to adjust generation for your area. Solar yield varies by up to 30% across the UK.

Your roof direction Which way does your main roof face?

System size Most 3-bed homes suit 4 kWp, which is ten 400W panels.

Monthly electricity bill Drag to match your average monthly spend. We use it to estimate how much of the solar you can use yourself.

£40 £400 £120/mo

Your daytime electricity rate Solar replaces what you'd pay in the daytime, not your overnight rate.

Your export rate What you're paid for surplus sent to the grid under the Smart Export Guarantee.

Current EPC rating Solar usually lifts an EPC by one band. This doesn't change the sums.

Your setup

Add battery storage Stores unused solar for the evening. Cost is added to the payback

Battery size:

Electric vehicle at home in the day Soaks up surplus solar that would otherwise be exported

Your estimated savings

Annual generation

3,800 kWh

4 kWp · UK average

Annual savings

£674

bill savings plus export

Payback period

10.4 yrs

on £7,000 installed

25-year return

£7,900

after all costs

Solar you use

40%

rest is exported

Where your savings come from

Used directly

£400

Via the battery

£0

EV charging

£0

Export payments

£274

Monthly generation through the year

Estimates only, not a quote. Install costs are typical UK prices with 0% VAT. The 25-year figure allows for panels losing 0.5% of output a year and one inverter replacement at £1,000, and assumes energy prices stay where they are. A battery is unlikely to last the full 25 years and no replacement is included. Shading is not modelled. How the sums work.

Rates last checked: 2 October 2026 · Electricity 26.32p/kWh (October price cap) · Export 12p/kWh

How the Solar Calculator Works

Both tools start from the same place: how much electricity a kilowatt of panels produces where you live. From there the money depends on one question more than any other. How much of that electricity will you use yourself, and how much will you sell?

Step	What we assume	Why
Generation	780 to 1,110 kWh a year per kWp, by postcode area	Cornwall gets about 40% more sun than the north of Scotland. The UK average is about 950
Roof direction	South 100%, SE/SW 95%, east/west 82%, north 58%	For a typical 30 to 40 degree pitch
What you use yourself	40% of generation, capped at 45% of your annual usage	A home that's empty all day uses less. A small bill can't absorb a big system
Battery	About 200 kWh of extra self-use a year per kWh of capacity	Capped at 70% of your surplus, because summer produces more than a battery can hold and winter produces little to store
Bill saving	Each kWh you use is worth your daytime rate: 26.32p on the price cap	That is the electricity you no longer buy
Export	Each kWh you don't use earns your export rate: 12p by default	Octopus cut its standard rate from 15p to 12p in March 2026
Install cost	£4,000 for 2 kWp up to £10,000 for 6 kWp. Batteries £3,000 to £7,000	Typical 2026 prices. Yours depends on roof access, scaffolding and brand

What Moves Your Numbers Most

How much you use in the day

Every kWh you use yourself is worth 26p. Every kWh you export is worth 12p or less. Running the washing machine, dishwasher and hot water at midday is the cheapest upgrade there is.

Your export rate

The gap between a 5p basic rate and a 15p deal is about £230 a year on a 4 kWp system. Compare export tariffs →

Adding a battery

A battery lifts self-use from about 40% to 65%, but with 12p export each stored kWh only gains you about 14p. Batteries pay back faster when they also charge on a cheap overnight rate. Battery calculator →

Roof direction and shade

East and west roofs still produce about 82% of a south-facing one. Shade from a chimney or tree does more damage than a few degrees of orientation.

Paying for it: solar and batteries carry 0% VAT until 31 March 2027. If you'd rather spread the cost, the government's Warm Homes Loan Scheme will offer subsidised loans of up to £15,000 for solar and £15,000 for a battery once lenders launch. Add the monthly repayment to your sums before you compare it with the saving.

Frequently Asked Questions

How much do solar panels save a year in the UK?

A typical 4 kWp south-facing system generates about 3,800 kWh a year. At October 2026 prices, using 40% yourself at 26.32p and exporting the rest at 12p, that is worth about £670 a year. Homes that use more in the daytime, or have a better export rate, save more.

How long do solar panels take to pay for themselves?

Usually 8 to 12 years for a system without a battery. A 4 kWp system costing £7,000 and saving about £670 a year pays back in a little over 10 years. Panels are generally warrantied for 25 years, so most of their working life comes after payback.

How accurate is this solar calculator?

It should be within about 10 to 15% for an unshaded roof. It uses average yield for your postcode area and typical household behaviour, and it doesn't model shade, unusual roof pitches or your exact usage pattern. An MCS-certified installer will give you a site-specific estimate with their quote.

Is a battery worth adding to solar panels?

It depends on your tariff. Storing solar means you use a unit worth 26p instead of exporting it for 12p, a gain of about 14p. On stored solar alone a 5 kWh battery saves around £140 a year, which is a long payback on £3,000. Charging the battery overnight on a cheap tariff as well improves it a lot.

How much do you get paid for exporting solar electricity?

Under the Smart Export Guarantee, basic rates open to anyone are about 4p to 6p per kWh. Most suppliers pay about 12p if you also buy your electricity from them, and 15p or more if they installed your system. Octopus cut its standard export rate from 15p to 12p in March 2026.

How many solar panels do I need?

Most three-bedroom homes fit 8 to 12 panels, which is 3.2 to 4.8 kWp with 400W panels. Roof space is usually the limit. Use the roof planner at the top of this page to see how many fit on yours.

Do solar panels work on an east or west facing roof?

Yes. An east or west facing roof produces about 82% of what a south-facing one would, and a split east-west array spreads generation across more of the day, which can help you use more of it yourself. North-facing roofs produce a little under 60% and rarely pay back.