Current energy scores vary enormously between local authorities. Potential scores barely vary at all. Once you notice that, the map of British housing looks different.
The Isles of Scilly has the lowest average energy score of any local authority in England or Wales. Its 842 homes average 46.3 on the SAP scale that EPC ratings are built from, against a national average of 67.1. Nowhere else comes close to that far below the line.
Now look at the second number on the same certificates. Asked what those homes could reach with the specific improvements each certificate already lists, the answer for Scilly is 80.1. The national figure is 81.3.
A gap of twenty-one points at the bottom. A gap of one at the top.
That pattern holds nationally, and it is the most striking thing in this dataset. Current scores are spread across nearly thirty points of the scale. Potential scores are bunched into eight. Whatever a place looks like today, the certificates keep pointing at roughly the same destination: high seventies, low eighties, more or less everywhere.
The ceiling is flat. The floor is what moves.
So the interesting question stops being which areas score badly, and becomes which ones have the furthest to climb. Five authorities stand clear of the rest. Four of the five are Welsh, and all five are rural.
| Authority | Current | Potential | Climb |
|---|---|---|---|
| Isles of Scilly | 46.3 | 80.1 | 33.8 |
| Ceredigion | 57.8 | 81.8 | 23.9 |
| Gwynedd | 56.7 | 80.4 | 23.7 |
| Isle of Anglesey | 59.0 | 82.0 | 23.0 |
| Powys | 60.0 | 82.1 | 22.0 |
Scilly's position has an obvious culprit once you look at how the islands are heated. Nationally, 72.4% of homes are on mains gas. On the Isles of Scilly the figure is 0.2%. There is no gas grid twenty-eight miles out into the Atlantic, so almost every property is running on electricity, oil or bottled fuel, and SAP scoring treats that expensive heat unkindly. Add a housing stock where more than a quarter of homes predate 1900 and the floor drops a long way below the national line.
None of which changes where the certificates say those homes could get to. The islands sit twenty-one points below the country today and land within a point and a half of it on paper. For anyone deciding where retrofit money buys the most movement, that distance is the whole argument.