Same panels, same installer, same £6,000 cost, same electricity price, same export rate. The only thing that changes is where the roof is — and that alone shifts the payback by almost two years.
| Annual generation | Payback period | |
|---|---|---|
| South England | 4,200 kWh | 9.9 years |
| Scotland | 3,500 kWh | 11.8 years |
The 700 kWh/year generation gap — 20% more sunlight hitting the same-sized system in the south — is entirely a geography effect, not a product or pricing difference. Every other input to the calculation is identical.
Both numbers land well inside a panel's 25-year warrantied lifespan, so both installations are still comfortably worthwhile — the difference is in how many years of pure profit you get after payback, not whether payback happens at all. A Scottish install just needs realistic expectations set from the numbers, not a South-of-England generation figure quietly assumed by a generic calculator.
Pick your actual region and system size for an honest payback estimate.
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