Of thirteen UK points this one comes second. The gap to the mounting you choose is several times larger than the gap to the region above.
| Arrangement | South West | Wales, for the border |
|---|---|---|
| Pitched roof, due south at 35 degrees | 822 kWh | 798 kWh |
| Frame on the ground, due south at 30 degrees | 816 kWh | 792 kWh |
| Flat against a south-facing wall | 594 kWh | 575 kWh |
| Flat against an east-facing wall | 417 kWh | 385 kWh |
All figures kWh a year. Exeter and Cardiff, queried from PVGIS on 13 September 2026 at 0.8 kWp with 14 per cent system losses, unshaded.
Across every mounting, the difference between this side of the Severn and the other is a few per cent. What is genuinely different across that border is the planning position, not the sunshine, which is why this site spends a page on the rules and a table on the numbers.
Four things have to travel with any number on this page, and a seller quoting you one of these without them is quoting you half.
| It assumes | Your house |
|---|---|
| Nothing shades the panel at any point in the day | Has a tree, a chimney, a neighbour, or a hill. Shading removes more output than the entire difference between the best and worst regions in Britain |
| The panel points due south at the stated angle | Has whatever wall it has. An east-facing wall costs about half |
| Every kilowatt hour generated is a kilowatt hour used | Is empty between eight and six, in which case most of it is exported unpaid and cannot be stored, because storage is outside the approved class |
| One representative city stands for a whole region | Is not in that city. A Cornish coast and a Cotswold valley are both in this column |
Panel wattage and output are two different numbers. The specification permits up to 2000 W of panels feeding an inverter that may deliver no more than 800 VA to the mains, so a listing advertising a large panel figure is describing the input, not what reaches your consumer unit.
Above 960 W of panel capacity the manufacturer is obliged to recommend a professional assessment of your existing installation. That is a precaution rather than a prohibition, and a listing that mentions neither figure has told you nothing about which side of it you would be on.
We publish generation because PVGIS is free, open and reproducible, and we say how we queried it. We do not publish payback for this region, because that needs retail prices we have not yet sourced from anywhere we would be willing to cite. When we have them, they will appear with the date they were checked.