South-facing is the UK benchmark for solar output, but it's not the only orientation that works — and the actual percentage drop for other orientations is smaller than many people assume. Here's what each orientation really costs you in generation, and how sizing should account for it.
Output by orientation, roughly
Taking due south at 30–40° tilt as the 100% baseline:
| Orientation | Output vs. south |
|---|---|
| South | 100% (benchmark) |
| South-east / South-west | 95% |
| East / West | 85% |
| Flat roof | 90% |
| North-east / North-west | 75% |
| North | 65% |
These are the planning figures our calculator uses, not a precise prediction for your own roof: actual output also depends on latitude, local shading and the specific tilt angle.
Why south-east/south-west often barely matters in practice
The gap between due south and south-east or south-west is small enough that, for most homes, roof shape and available space matter more than chasing the theoretically perfect orientation. A larger south-west face will often out-generate a smaller, more obstructed true-south face. Don't discount a SE/SW roof face just because it isn't exactly south.
What tilt angle actually does
Separately from orientation (compass direction), tilt angle (how steeply the panel is angled from flat) also affects output. For most of the UK, roughly 30–40° from horizontal is close to optimal for year-round generation — most standard pitched roofs fall naturally within or near this range, which is part of why standard roof-mounted installations work well without needing an adjusted mounting angle.
East-west split arrays: an option for flat or dual-facing roofs
Rather than concentrating all panels on one face, some installations deliberately split panels across east- and west-facing sections (common on flat roofs with tilted mounting frames, or homes with genuinely dual-aspect roofs). This produces a flatter generation profile across the day — less peak output at solar noon, but more generation spread through the morning and afternoon — which can suit households whose usage is spread throughout the day rather than concentrated around midday.
What actually matters more than perfect orientation
- Shading — a shaded south-facing roof can underperform an unshaded south-west one
- Usable roof area with proper edge clearance — see our solar guide for why naive area-based panel counts overstate what actually fits
- Whether the "wrong" orientation still generates enough to be worthwhile — even a west-facing-only system at about 85% of south's output is very often still a strong investment; don't rule out a good roof just because it isn't perfectly south-facing