Thirteen points were queried across the United Kingdom. Sort them and this one lands in the middle. Average them and the mean comes out at 752.9, which is within a single kilowatt hour of what Birmingham returns. That makes this region a yardstick, so the whole site is built as an index with it set to 100.
Ideal south-facing roof at 35 degrees, 0.8 kWp, 14 per cent losses, unshaded. PVGIS, 13 September 2026. Median of the thirteen: 752. Mean: 752.9.
Two conclusions come straight off that chart, and the second one is the reason this site exists.
The first is that the country is tighter than people assume. The best point in the United Kingdom sits at 119 on this scale and the worst at 84. That is the entire national spread, from the south coast to the Highlands, on identical equipment.
The second is what happens when you stop moving house and start moving the panel.
An east-facing wall here indexes at 52. The dimmest point in the entire country, on a proper south-facing roof, indexes at 84. One decision about which way a panel points is worth several times the whole geography of Britain.
Turning kilowatt hours into an index makes them easier to compare. It does not make them truer.
| Still assumed | Consequence |
|---|---|
| Nothing shades the panel at any hour | Shade is larger than everything charted above. A tree can cost more than moving to Inverness would |
| One city stands for a whole region | Birmingham is the point queried. Shropshire is not Birmingham |
| Generation counts as benefit | Only the part used as it is produced counts, and storage sits outside the approved class |
| A single device | The connection rules cap a household at one, so the index describes a total |
Birmingham is a dot on a map. Your wall has a fence in front of it.
Send a postcode and what you are thinking of, and we will run the same query at your own coordinates, index it against this region the way the charts above do, and show the arithmetic so you can check it.
You also get the licence area we can confirm for the address and whether the planning conditions reach the mounting you described.