Solar panel angle in Dehiwala-Mount Lavinia
In Dehiwala-Mount Lavinia, fixed panels collect the most energy over a year tilted 6° from horizontal and facing south. But anything between 0° and 15° is within 2% of the best, so the pitch you already have is probably fine.
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Every roof, scored
Percentage of the maximum possible annual yield, for each combination of orientation and pitch in Dehiwala-Mount Lavinia.
| Roof faces | 0° | 15° | 30° | 45° | 60° | 90° |
|---|---|---|---|---|---|---|
| South | 100% | 99% | 93% | 82% | 67% | 38% |
| South-east / south-west | 100% | 99% | 93% | 83% | 71% | 45% |
| East / west | 100% | 97% | 91% | 82% | 71% | 49% |
| North-east / north-west | 100% | 95% | 87% | 75% | 62% | 39% |
| North | 100% | 95% | 85% | 70% | 54% | 29% |
Where "tilt equals your latitude" happens to work
The rule of thumb says tilt your panels at your latitude — 7° for Dehiwala-Mount Lavinia. The real optimum is 6°, so here the rule happens to be about right.
The rule breaks down further from the equator, where the optimum falls increasingly below the latitude — by around 10 degrees at 50°, and 15 by 65°. Close to the equator the two happen to coincide, so here the rule of thumb is genuinely fine.
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 | 6° | south |
| Summer | 0° | south |
| Winter | 32° | south |
| Flat on the ground | 0° | — |
A flat installation here keeps 100% of the maximum; mounted vertically on a wall, 38%.
Other cities in Sri Lanka
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.