Estimate how many years your solar PV system takes to pay for itself from electricity bill savings, Smart Export Guarantee income and your own installation cost.
UK solar calculator · Payback · SEG export · ROI
Total upfront cost after any grants.
Share of generation you use yourself instead of exporting.
What your supplier pays per kWh you export.
Take the annual electricity your system generates, split it between the share you use yourself (saving on your bill) and the share you export (earning SEG income), then divide your installation cost by the combined annual benefit. A typical 4 kWp system in the UK generates around 3,800 kWh a year and delivers £700–£800 in combined savings and income at current prices.
Because you save more per kWh on electricity you use yourself than on electricity you export, homes with higher daytime consumption — or a battery to shift evening load — see faster payback.
The break-even point is the simplest way to judge a quote: installation cost divided by annual benefit. If a £6,500 system saves and earns £715 a year, the payback period is just over nine years.
Return on investment looks beyond break-even. Once the system has paid for itself, future bill savings and export income become net benefit. For a 25-year panel life, even a modest annual benefit can add up after the payback point.
The self-use share (sometimes called 'self-consumption rate') is the fraction of your solar generation that you consume directly in the home rather than exporting. Because the value of self-used electricity (saving ~24p/kWh on your bill) is typically higher than the SEG export rate (~15p/kWh), every extra percentage point of self-use adds more to your annual benefit.
Without a battery, most households self-use 30–45% of their generation. Shifting high-load appliances like dishwashers and washing machines to run during daylight hours, or charging an EV at home, can push this higher. A home battery typically raises self-use to 60–75%.
A typical 4 kWp system costing around £6,500 and generating 3,800 kWh a year will pay for itself in roughly 9–11 years at current electricity prices and SEG rates. The exact figure depends on your installation cost, how much of the electricity you use yourself, your electricity tariff, and the export rate your supplier offers. Use the calculator above with your own figures for a personalised estimate.
Enter your planned system size in kWp, total installation cost, electricity unit rate, export tariff and the share of solar generation you expect to use at home. The calculator estimates annual generation, bill savings, SEG export income and the payback period. It is designed for UK solar panel calculator searches where you want a fast break-even estimate before speaking to installers.
For most homeowners, yes — especially with electricity prices elevated since 2022. A well-positioned south-facing roof can achieve payback in under ten years and then generate free electricity for the remaining 15–20+ years of the panels' life. Properties with higher daytime electricity use (home workers, EV chargers, heat pumps) benefit most because they can use more of their own generation.
The Smart Export Guarantee (SEG) is a UK government-backed scheme that requires licensed energy suppliers with 150,000 or more customers to offer a tariff that pays you for every kWh of surplus electricity you export to the grid. Rates vary by supplier but typically range from 4p to 20p per kWh. A higher export rate reduces payback time meaningfully, especially if you export a large share of your generation.
A home battery lets you store surplus generation and use it in the evening rather than exporting it. Because the value of self-used electricity (the bill saving at ~24p/kWh) is typically higher than the SEG export rate (~15p/kWh), shifting more consumption to your own generation improves the annual benefit. However, batteries add £2,000–£5,000 to upfront costs, so you need to run the numbers on the combined system. Try increasing the self-use share in the calculator to see the effect before pricing in a battery.
A solar panel payback calculator focuses on the number of years until your bill savings and export income recover the upfront installation cost. A solar ROI calculator looks at the total return over a longer period, such as 20 or 25 years. This calculator gives the break-even point directly and shows the annual benefit, which you can use as a simple ROI signal.
Yes. Most silicon panels lose around 0.5% of their rated output per year — so a panel rated at 400 W today might produce around 380 W after ten years. This means real-world payback is slightly longer than the simple calculation suggests. Most manufacturers guarantee at least 80% of rated output after 25 years.
Yes, shading can have a disproportionate effect. Traditional string inverter systems can lose significant output even if only one panel is shaded, because all panels in a string are limited by the weakest panel. Microinverters or DC optimisers mitigate this by allowing each panel to operate independently. If your roof has chimneys, dormer windows, or nearby trees, mention this when getting quotes.
