Solar Panel Payback Calculator UK 2026
Work out the payback period and 25-year return on a UK solar PV system using real yield, import and SEG export rates.
Your numbers
Results update instantly as you type or drag.
Payback period
10.2 yrs
Saving £739 a year, £10,966 net over 25 years.
- Annual generation
- 3,740 kWh
- Self-consumed
- 1,870 kWh
- Exported to grid
- 1,870 kWh
- Bill saving per year
- £458
- SEG export income
- £281
- Total annual benefit
- £739
Illustration only, based on the figures you entered. Solar Payback results are not financial advice.
MCS-certified installers only — no cold calls · We may earn a commission
How the solar payback maths works
Solar in the UK earns money two ways. Every kilowatt-hour you generate and use in the house is a kilowatt-hour you do not buy from your supplier, saving you the full import price. Everything else is exported to the grid and paid at your Smart Export Guarantee rate, which is typically well below the import price. That gap is why self-consumption — running the washing machine, dishwasher and hot water in daylight — drives the return more than panel count does.
Generation in the UK runs at roughly 850 kWh per kWp per year for a well-oriented roof. A south-facing, unshaded roof in the south of England can beat 950; an east-west split in the north-west sits nearer 750. This calculator uses 850 as the national planning figure and assumes 50% of generation is used in the home, which is typical for a household without a battery. Add a battery and self-consumption commonly climbs to 70-80%, which shortens payback but adds several thousand pounds of cost.
Solar PV is zero-rated for VAT in the UK until 2027, and the panels themselves are usually warranted for 25 years with output guaranteed around 85% of day-one performance at year 25. The inverter is the part that typically needs replacing once, around year 12, at roughly £800 to £1,500 — worth factoring into a long-run view.
The honest summary: at current unit rates a typical 4kWp system pays back in eight to eleven years and then generates free electricity for another fifteen-plus. It is a solid, unspectacular return that gets better every time electricity prices rise.
How this is calculated
Annual generation = system size (kWp) × 850 kWh. Self-consumed = 50% of generation, capped at your annual usage. Exported = generation − self-consumed. Annual saving = (self-consumed × import price) + (exported × SEG rate), converted from pence to pounds. Payback = system cost ÷ annual saving. The chart plots cumulative saving minus the upfront cost over 25 years.
- 1Enter the total installed cost quoted for your system.
- 2Enter the system size in kWp and your annual electricity usage from a bill.
- 3Adjust the import price and SEG export rate to match your tariff.
- 4Read the payback period and 25-year net return.
Frequently asked questions
Written by Dave B, BillSaverLab
Homeowner in Warrington. Every calculator here is built against my own mortgage statements, energy bills and broadband contracts before it goes live — and re-checked each time UK rates move.
Tested in Warrington · Last reviewed 2026
MCS-certified installers only — no cold calls · We may earn a commission