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Solar panel payback in Portsmouth
How fast does a 4 kWp domestic solar system pay back in Portsmouth, what does it save in year 1, and what's the 25-year net benefit? This page uses the same assumptions as our full solar calculator — only the local irradiance (PVGIS annual yield for the PO1 outcode) changes.
What makes Portsmouth different
Portsmouth's coastal south-coast position gives it among the UK's top solar yields — neck-and-neck with Brighton.
The figures above use a 4 kWp south-facing system, no battery, 3,500 kWh/yr household use, 27p/kWh import tariff, 15p/kWh SEG export and 4%/yr electricity inflation — the same defaults as the full UK solar calculator. Yield here (1025 kWh/kWp) is drawn from PVGIS satellite data for the PO1 outcode. If you want to model a battery, a larger system, east/west panels or a different tariff, open the main solar calculator — it accepts your exact postcode and full custom inputs.
Model it for your exact postcode
The numbers above assume the outcode PO1. For your postcode — which adjusts irradiance slightly — use the calculator below.
Other cities in South East England
Solar yield varies more within a region than most people expect — coast vs inland, altitude, and overcast patterns all shift the numbers by a few percent.
| City | kWh/kWp/yr | Year-1 saving | Payback | 25-yr net |
|---|---|---|---|---|
| Southampton | 1020 | £783 | 8.0 yrs | £25424 |
| Brighton | 1035 | £795 | 7.9 yrs | £25903 |
| Oxford | 985 | £756 | 8.2 yrs | £24304 |
| Milton Keynes | 970 | £745 | 8.3 yrs | £23825 |
| Reading | 990 | £760 | 8.2 yrs | £24464 |
| Slough | 985 | £756 | 8.2 yrs | £24304 |
| Portsmouth (this page) | 1025 | £787 | 7.9 yrs | £25584 |
Compare other cities
Pick any UK city to see its solar payback side-by-side with Portsmouth.
Getting accurate quotes in Portsmouth
The calculator gives a tight estimate, but three local factors decide your real payback: roof orientation (south ≥ east/west by 15–20%), shading from chimneys, trees and neighbours, and installer pricing — which varies wildly even within a single city. Get at least three MCS-certified quotes before committing.
If you're also looking at batteries, check which UK Smart Export Guarantee tariff will pay you the most — it changes the whole payback equation. And if you're considering a heat pump alongside solar, start with the heat pump vs gas boiler calculator and the £7,500 BUS grant check.