Solar panel angle in The Valley
In The Valley, fixed panels collect the most energy over a year tilted 16° from horizontal and facing south. But anything between 5° and 25° is within 2% of the best, so the pitch you already have is probably fine.
What is your roof worth?
Every roof, scored
Percentage of the maximum possible annual yield, for each combination of orientation and pitch in The Valley.
| Roof faces | 0° | 15° | 30° | 45° | 60° | 90° |
|---|---|---|---|---|---|---|
| South | 97% | 100% | 98% | 90% | 78% | 46% |
| South-east / south-west | 97% | 98% | 95% | 88% | 77% | 51% |
| East / west | 97% | 94% | 88% | 80% | 70% | 49% |
| North-east / north-west | 97% | 90% | 80% | 67% | 54% | 35% |
| North | 97% | 88% | 75% | 59% | 44% | 23% |
Why "tilt equals your latitude" is wrong here
The rule of thumb says tilt your panels at your latitude — 18° for The Valley. The real optimum is 16°, 2° lower than the rule suggests.
Two reasons, both geometric. Summer days are much longer than winter ones, so the year's energy is weighted toward a higher sun than the annual average. And a low winter sun sends its light through a long slant of atmosphere, arriving weak — tilting to catch it costs more in summer than it wins in winter.
In fairness to the rule: following it here would cost you only 0.1%. It is wrong, but it is not expensive.
Seasonal angles
If you can adjust your panels twice a year, these are the angles to use. Most people should not bother — the gain is small and the ladder is real.
| Setting | Tilt | Facing |
|---|---|---|
| Fixed, all year | 16° | south |
| Summer | 0° | south |
| Winter | 42° | south |
| Flat on the ground | 0° | — |
A flat installation here keeps 97% of the maximum; mounted vertically on a wall, 46%.
Assumptions
- These are angles and percentages, never kilowatt-hours. Optimal angles are driven by geometry and are robust. Absolute energy output depends on measured irradiance, cloud, soiling and hardware, none of which are modelled here.
- Clear sky, no shading. Trees, chimneys, neighbouring buildings and terrain are ignored, and they can dominate everything on this page.
- Fixed panels. Trackers follow the sun and change the answer entirely.
- Ordinary ground. Reflectance is taken as 0.2, typical for grass and soil. Snow reflects far more and favours steeper tilts.