Tilt your solar panels to 13.5° facing south in Debre Birhan. That is the most efficient fixed angle for its latitude of 9.68°. The full breakdown, including seasonal and monthly adjustments, is below.
Today, the most efficient tilt for photovoltaic panels in Debre Birhan is 5.1°, facing south. At solar noon the sun sits 84.9° above the horizon. Setting your panels to this angle keeps them as close to perpendicular to the sun as possible, which is where they generate the most electricity.
Your photovoltaic panels need to be angled facing south. Debre Birhan is in the northern hemisphere, so panels catch the most sun facing south.
If you're mounting the photovoltaic panels at a stationary angle, such as on your roof, the most efficient angle is 13.5°.
If you're planning to change the angle of your photovoltaic panels twice per year, the most efficient angle is 12° facing north in summer months and 27.7° facing south in winter months.
When changing the angle of your photovoltaic panels each season, the most efficient angle is 15.4° facing north in summer months and 32.6° facing south in winter months, and 7.2° facing south in autumn and spring months.
If you adjust your photovoltaic panels every month, the table below gives the most efficient angle for Debre Birhan throughout the year. The shallowest angle is 1.9° in April, and the steepest is 33.1° in December.
| Month | Optimal tilt | Facing | Sun angle at noon |
|---|---|---|---|
| January | 29.8° | South | 60.2° |
| February | 20.9° | South | 69.1° |
| March | 10.1° | South | 79.9° |
| April | 1.9° | North | 88.1° |
| May | 10.4° | North | 79.6° |
| June | 13.7° | North | 76.3° |
| July | 10.7° | North | 79.3° |
| August | 2.1° | North | 87.9° |
| September | 9.9° | South | 80.1° |
| October | 21.5° | South | 68.5° |
| November | 30.1° | South | 59.9° |
| December | 33.1° | South | 56.9° |
The sun angle at noon is how high the sun sits above the horizon at midday. Facing your panels south at the tilt shown for each month keeps them as close to perpendicular to the sun as possible, which is where they generate the most electricity.
It comes out of your latitude. Debre Birhan sits at 9.68°, which puts the best fixed angle at 13.5°. Near the equator the midday sun is almost overhead, so panels lie close to flat, around 3°. The further from the equator you are, the lower the sun sits, and the steeper your panels have to stand to face it squarely.
The climb is not one for one. At 30° of latitude the best fixed tilt is about 31°, but at 60° of latitude it is about 46°, not 60°. The optimum flattens off toward the poles because the winter sun is low and much of the light arriving is diffuse rather than direct. Every angle on this page comes from a curve fitted to measured optimal-slope data for 52 cities, so it follows that flattening instead of assuming tilt equals latitude. See how the two compare.
The angle is settled. Here is what is worth checking on the panels themselves: