Move an 800 W panel from a garden frame to an east-facing wall and you lose about half its output. Move it from Brighton to Inverness and you lose about a third. Most calculators only ask you the second question.
What this assumes
Payback needs an all-in cost, and nobody can currently source one for the UK. We would rather leave the box empty than fill it with a plausible number, so there is no payback line on this page until a price can be cited.
Thirteen regions, four mountings, kWh a year for a compliant 800 W device. Queried from PVGIS on 13 September 2026.
| Region | Garden frame | Roof pitch | South wall | East or west wall |
|---|---|---|---|---|
| South East | 890 | 897 | 645 | 424 |
| South West | 816 | 822 | 594 | 417 |
| East of England | 795 | 802 | 594 | 412 |
| Wales | 792 | 798 | 575 | 385 |
| London | 789 | 795 | 582 | 409 |
| East Midlands | 754 | 760 | 564 | 391 |
| West Midlands | 746 | 752 | 555 | 389 |
| Yorkshire | 729 | 736 | 550 | 376 |
| North East | 727 | 734 | 558 | 372 |
| Northern Ireland | 708 | 714 | 534 | 367 |
| North West | 684 | 689 | 505 | 359 |
| Scotland, south | 656 | 661 | 491 | 337 |
| Scotland, north | 623 | 628 | 470 | 321 |
Read across a row, not down a column. The best region beats the worst by about 43 per cent on an ideal roof. An ideal roof beats an east wall by about double, in the same place.
A regional average is a starting point. Your actual roofline, fence and shading are what decide it.
Tell us the postcode and where you are thinking of putting it. We will run the numbers for your exact spot rather than a regional average, and tell you if the permitted development rules rule it out before you spend anything.