Solar Savings Calculator
Instant estimate of solar savings, payback, and 25-year return
Solar savings calculator
Instant estimate of annual savings, payback, and 25-year return for a UK home.
3,500 kWh
4 kW (9 x 450W)
5 kWh
£1,650
Year 1 generation
3,546
kWh
Annual saving
£677
Payback
13.1yr
Cost: £8,850
25-year return
£23,090
Includes 1.5% first-year LID, 0.5%/year panel degradation, and 3%/year electricity price inflation. Battery cost estimated at £450/kWh installed. Real results depend on your tariff, roof orientation, and usage pattern.
How this works
This calculator uses the UK average generation figure of 900 kWh per kWp per year. A 4 kW system (9 x 450W panels) generates roughly 3,600 kWh annually on a south-facing roof.
Savings come from two sources: self-consumed electricity saves you the full import rate (24.5p/kWh), while exported surplus earns the SEG export rate (12p/kWh on average).
Panels degrade at about 0.5% per year after a small first-year loss (1-2% from Light-Induced Degradation). The 25-year return figure accounts for this degradation plus 3% annual electricity price inflation.
Things to consider
- •Install costs vary from £1,200 to £2,100 per kW installed — get three quotes to find the best price.
- •Battery installation adds £400-£550 per kWh but can dramatically increase self-consumption.
- •EV owners benefit significantly more than the average — dedicated EV tariffs plus solar self-charging can halve fuel costs.
- •Your actual generation depends on roof angle, shading, and local weather — this calculator uses UK averages.
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