About the Solar Panel Angle Calculator
This solar panel angle calculator gives the best tilt angle for fixed solar panels at your latitude, plus seasonal angles if your mounts are adjustable and a month-by-month table of the angle that points the panels straight at the midday sun. Enter your latitude (negative for the southern hemisphere) and choose a method.
It is useful for DIY ground mounts, RV and off-grid panels, and anyone deciding whether it is worth adjusting the tilt through the year. Panels in the northern hemisphere should face true south, and in the southern hemisphere true north.
The optimized method uses widely used rules of thumb fitted to annual sunshine calculations (for example 0.76 × latitude + 3.1° for a fixed year-round tilt), which slightly favour summer when days are longer. The simple method uses latitude and latitude ± 15°. Real-world differences between reasonable angles are usually only a few percent, so roof pitch is often good enough.
With the default inputs, the best fixed year-round tilt is 33.5 °. Change any value above to recalculate instantly.
How to use the solar panel angle calculator
- 1Enter your latitude — find it in any map app (negative if south of the equator).
- 2Choose the optimized or simple method.
- 3Use the year-round tilt for fixed mounts, or the seasonal tilts if you can adjust them.
- 4Pick a month to see the exact midday-sun angle and sun height.
- 5Point the panels true south (north in the southern hemisphere), not magnetic south.
Formula and method
A panel collects the most energy when sunlight hits it at right angles. At solar noon the sun’s elevation is 90° − |φ − δ|, where φ is latitude and δ is the solar declination (from −23.45° at the December solstice to +23.45° at the June solstice), so the tilt that faces the noon sun squarely on a given day is |φ − δ|. Declination is estimated with Cooper’s equation δ = 23.45° × sin(360° × (284 + n) ÷ 365).
Because days are longer in summer, the best fixed angle over a whole year is a little lower than latitude. The optimized method uses published rules of thumb fitted to annual insolation (0.87 × latitude in the tropics, 0.76 × latitude + 3.1° elsewhere); the simple method uses latitude year-round and ±15° for winter and summer.
- φ
- Latitude in degrees (negative in the southern hemisphere)
- δ
- Solar declination on the chosen day
- n
- Day of the year (1–365)
Worked examples
Latitude 40° N (e.g. Philadelphia, Denver)
At 40° the fixed year-round tilt is 0.76 × 40 + 3.1 = 33.5°. Winter is 0.9 × 40 + 29 = 65° and summer 12.5°. On June 21 the sun’s declination is about +23.45°, so it stands 73.4° high at noon and panels facing it squarely would be tilted about 16.6°.
London in December
At 51.5° N the best fixed tilt is about 42°. In late December the sun is only about 15° above the horizon at noon, so a panel would need to be tilted almost 75° to face it — close to the 75° winter setting.
Sydney with the simple method in March
In the southern hemisphere panels face true north. The simple method uses the latitude, 33.9°, year-round, adding 15° in winter (48.9°) and subtracting 15° in summer (18.9°). Near the March equinox the declination is almost zero, so the midday-sun tilt is about 33.5°.
Frequently asked questions
What is the best angle for solar panels?+
For fixed panels, a tilt a little below your latitude is usually best over a full year — roughly 0.76 × latitude + 3°. At 40° latitude that is about 33°. Differences of 5–10° from the ideal typically cost only a few percent of annual output.
Should solar panels face south or north?+
In the northern hemisphere panels should face true (geographic) south; in the southern hemisphere, true north. East or west orientations still work but usually produce around 10–20% less energy over a year.
Is it worth adjusting solar panel tilt seasonally?+
Adjusting twice a year (steeper in winter, flatter in summer) typically adds only a few percent of annual energy, and four times a year a little more. It is worthwhile for ground or pole mounts that are easy to adjust, but rarely for roof arrays.
Can I just use my roof pitch?+
Usually yes. Most roof pitches between about 15° and 40° are close enough to optimal that the output loss is small, and flush mounting is cheaper and less exposed to wind than tilted racking.
Why is the winter angle so steep?+
In winter the sun stays low in the sky, so a steeper panel faces it more directly. A steep angle also helps snow slide off, which can matter more than the geometry in snowy climates.
Sources