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Solar Payback Calculator

Solar panel payback calculator

Estimate how many years solar panels on your roof could take to pay for themselves, based on your electricity use, your unit rate, local sunshine and installed prices.

Starting values: Ofgem’s price cap unit rate and typical household use, solar output for 8 UK towns and cities from PVGIS, and the government’s median installed price for your system size. Change any of them to match your own bills and quote.

Your home

All amounts in pounds sterling.

Your home

Sets how much electricity each kW of panels generates in a year where you live.

kWh per month

Check your bill or your supplier’s app for kWh used. Average the last 12 months if you can.

pence per kWh

Starts at the Ofgem price cap average for Direct Debit. Your bill shows your own unit rate.

Solar system
kW

Leave blank to size the panels to cover your yearly use, or enter the size on your quote.

Installed price

£1.78 per watt: the median for 0–4 kW systems in the latest government cost data. Your quote may differ.

Assumptions you can change
% per year

Starts at 0.5%, the median of nearly 2,000 reported rates in an NREL review.

% per year

A scenario, not a forecast. Try 0% and 5% to see how much it matters.

%

Share of the panels’ output your home uses as it is generated. 100% assumes all of it replaces electricity you would otherwise buy, up to your annual use.

A battery only adds savings when you use less than 100% of your solar power directly. Lower “Used directly at home” under assumptions to model that.

Results

Payback period

6.9years

Cumulative savings first cover the installed cost during year 7.

Installed cost
£5,273
Published median for 0–4 kW systems
First-year savings
£711
Savings over 25 years
£24,227
Net gain after 25 years
£18,954
Return over 25 years
359%
Net gain as a share of the installed cost
System size
3.0 kW
Sized to cover your yearly use
First-year generation
2,700 kWh
Cumulative savings over 25 yearsThe line crosses the installed cost in year 7: that is when the system has paid for itself.
Year-by-year table
Generation and savings for each of the 25 years
YearGeneration (kWh)Price per kWhSaved that yearSaved so farNet position
12,700£0.263£711£711-£4,562
22,687£0.271£728£1,439-£3,834
32,673£0.279£746£2,185-£3,088
42,660£0.288£765£2,950-£2,323
52,646£0.296£784£3,734-£1,539
62,633£0.305£803£4,538-£735
72,620£0.314£823£5,361£88
82,607£0.324£844£6,205£932
92,594£0.333£865£7,070£1,797
102,581£0.343£886£7,956£2,683
112,568£0.354£908£8,864£3,591
122,555£0.364£931£9,795£4,522
132,542£0.375£954£10,749£5,476
142,530£0.387£978£11,727£6,454
152,517£0.398£1,002£12,729£7,456
162,504£0.410£1,027£13,756£8,483
172,492£0.422£1,052£14,809£9,536
182,479£0.435£1,079£15,887£10,614
192,467£0.448£1,105£16,993£11,720
202,455£0.462£1,133£18,126£12,853
212,442£0.475£1,161£19,287£14,014
222,430£0.490£1,190£20,477£15,204
232,418£0.504£1,219£21,696£16,423
242,406£0.519£1,250£22,946£17,673
252,394£0.535£1,281£24,227£18,954

Savings count only electricity your home no longer buys. Power sent to the grid is valued at zero. Grid emissions data has not been verified yet, so no carbon figure is shown. See the methodology for every formula and source.

Frequently asked questions

How long do solar panels take to pay back in the UK?
It depends on your unit rate, how much sun your roof gets, how much of the output you use at home and the installed price. The starting values use the Ofgem price cap average, typical household use and the government’s median installed price for the system size, so you get an estimate straight away. Replace them with your own figures for a better one.
Does it include Smart Export Guarantee payments?
No. Electricity you export is valued at zero, so the estimate does not depend on an export tariff. If you are paid for exported electricity, your payback will be shorter than shown.
Where does the installed price come from?
From the Department for Energy Security and Net Zero’s solar PV cost data for the 2025/26 financial year, based on the MCS installation database. The calculator uses the median cost per kW for the size band your system falls in: 0–4 kW, 4–10 kW or 10–50 kW. Choose “Price per watt” or “Total quoted price” to use your own quote instead.
Which unit rate is used?
The starting value is Ofgem’s average electricity unit rate for Direct Debit customers in England, Scotland and Wales, for 1 October to 31 December 2026. Many tariffs differ, so use the unit rate on your own bill if you can. Northern Ireland is not covered by the price cap.
How accurate is the solar output for my town?
Each town’s figure comes from PVGIS for a roof-mounted, south-facing array at a 30° pitch with 14% system losses, averaged over 2005 to 2023. Shading, a different roof angle or an east or west-facing roof will change it. Choose “Somewhere else” to enter a PVGIS figure for your own address.