Solar panel payback calculator
A typical 4 kWp system makes about 3,200 kWh a year. Using half at home and exporting half, that is worth about £613.12 a year at the current price cap.
- Worth a year
- £613.12
- Saved on your bill
- £421.12
- Export income
- £192.00
- Electricity made
- 3,200 kWh
- Exported
- 1,600 kWh
4 kWp system making about 3,200 kWh a year, using 50% at home and exporting the rest at 12p.
At today’s prices. If electricity prices rise, payback is quicker. Panels slowly lose efficiency over time.
Payback by system size
At £1,080 per kWp, 800 kWh per kWp, 50% used at home and 12p export.
| System | Cost | Worth a year | Payback |
|---|---|---|---|
| 2 kWp | £2,160 | £306.56 | 7.0 years |
| 3 kWp | £3,240 | £459.84 | 7.0 years |
| 4 kWp | £4,320 | £613.12 | 7.0 years |
| 5 kWp | £5,400 | £766.40 | 7.0 years |
| 6 kWp | £6,480 | £919.68 | 7.0 years |
How we calculate this
We multiply your system size by how much electricity each kWp makes in a year. The part you use at home saves you your unit rate. The rest is exported and earns your Smart Export Guarantee (SEG) rate.
Payback is the installation cost divided by what the panels are worth each year. Which? says a typical 4 kWp system makes over 3,000 kWh a year.
Questions people ask
How long do solar panels take to pay back?
With our typical figures, a 4 kWp system costing £4,320 pays back in about 7 years. A higher quote, a shaded roof or a low export rate makes it longer.
How much electricity do solar panels make in the UK?
Roughly 800 kWh per kWp a year, so a 4 kWp system makes over 3,000 kWh. South-facing roofs in the south of England do best.
Do I get paid for electricity I export?
Yes, through a Smart Export Guarantee (SEG) tariff, but you have to sign up. Rates vary a lot, from a few pence to over 20p, so compare before choosing.
Is a battery worth adding?
A battery stores daytime solar for the evening, so you use more of it yourself. That raises the share you use at home, but adds to the cost. Try a higher home-use percentage to see the difference.
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