Solar Panel ROI Calculator – UK 2026
Enter your solar system's parameters or use the simple wizard to find out the annual savings, payback period and electricity production in the UK.
Basic
| Setup 1 | |
|---|---|
| Payback period | 9.25 years |
| Annual savings | £1,229 |
| Lifetime savings | £35,650 |
| Annual production | 7000 kWh |
| CO₂ saved | 1.23 t/year |
| Self-consumption | 35 % |
This calculation is indicative and is based on the entered inputs and average values for the UK (specific yield, electricity prices, a representative Smart Export Guarantee rate rather than an exact supplier tariff). Actual production and savings depend on the specific roof, orientation, shading and installer. It does not replace a quote from a solar installer.
How solar panel ROI is calculated
Annual production is calculated as the installed capacity (kWp) multiplied by the specific yield (kWh produced per year per 1 kWp) for the given location in the UK. Part of the electricity produced is used directly by the household (self-consumption), while the rest is exported to the grid under the Smart Export Guarantee (SEG).
Annual savings are the sum of two parts: money saved on electricity that would otherwise have been bought (self-consumption × electricity price), and income from surplus exported to the grid (remaining production × SEG rate).
The payback period is the year in which cumulative savings exceed the net investment (system and any battery price, minus any subsidy). The calculator also accounts for the annual rise in electricity prices and the gradual degradation of panel output.
The calculator lets you compare 2–3 setups side by side, for example a system without a battery and one with a battery, and immediately see the difference in payback period and total savings.
Frequently asked questions
How is the annual solar production calculated?
Multiply the system size in kWp by the location's specific yield in kWh/kWp/year. In the UK, the typical figure is around 1000 kWh/kWp/year in the south-east, ranging from around 750 kWh/kWp/year in northern Scotland to 1050 kWh/kWp/year on the south coast.
What does self-consumption mean and why does it matter?
It's the share of produced electricity you use directly instead of exporting it to the grid. Higher self-consumption means a faster payback, because purchased electricity is more expensive than the SEG export rate for surplus.
Is battery storage worth it?
A battery increases self-consumption and therefore savings, but also increases the investment. Compare the setup with and without a battery in the calculator – the higher the electricity price and daytime usage, the sooner a battery pays off.
What is the Smart Export Guarantee (SEG)?
Since the older Feed-in Tariff (FIT) closed to new applicants in 2019, the SEG is the main scheme for exporting surplus solar electricity to the grid in the UK. Rates vary widely between suppliers and tariff types, from a few pence per kWh on basic fixed tariffs to much higher rates on premium or agile tariffs paired with a battery.
Why does production decrease over time?
Solar panels gradually lose a small amount of output over time (degradation, typically around 0.5% per year). The calculator accounts for this in the production and savings estimate over the system's full lifetime.
How much CO₂ does a home solar system save?
It depends on annual production and the emissions factor of the Great Britain electricity grid. The calculator converts the electricity produced into tonnes of CO₂ saved per year based on the current energy mix.