About solar panel tilt angle
The tilt angle of a solar panel is how far it leans back from horizontal, measured in degrees. It matters because a panel produces the most electricity when sunlight strikes its face head-on, at a 90 degree angle of incidence. Lay a panel flat and the midday summer sun hits it well, but the lower winter sun grazes it at a shallow angle and output drops; stand it too steeply and you lose the opposite season. The goal of this calculator is to find the tilt that captures the most energy over whatever period you care about: the whole year, summer, or winter.
The single most useful rule is that the best year-round fixed tilt is approximately equal to your latitude. A site at 35 degrees latitude wants a panel tilted around 35 degrees from horizontal. This works because, averaged over a year, the sun's midday height tracks your latitude, so matching the tilt to the latitude keeps the average angle of incidence close to ideal. The calculator starts from your latitude and then offers seasonal adjustments for installations that prioritise one part of the year.
Tilt is only half of panel orientation; the other half is azimuth, the compass direction the panel faces. In the Northern Hemisphere panels should face true south, and in the Southern Hemisphere true north, to track the sun across the day. This tool focuses on the tilt question, which is the one homeowners and small installers most often need to settle when mounting a fixed array on a roof or ground frame.
How it works
The calculator uses the well-established latitude rule and its seasonal variants. Because the sun sits about 23.5 degrees higher in summer and 23.5 degrees lower in winter (the tilt of the Earth's axis), the optimal tilt shifts with the season. A widely used simplification adds or subtracts roughly 15 degrees to bias a fixed panel toward summer or winter output.
For a panel you set once and never touch, use your latitude for the best annual yield. If your demand peaks in winter (heating, short days) tilt steeper by about 15 degrees so the array faces the low winter sun. If you want maximum summer generation, tilt shallower by about 15 degrees. Two-axis tracking mounts remove the decision entirely by following the sun, but they add cost and maintenance that fixed arrays avoid.
Worked example
Suppose you are installing a fixed roof array near Los Angeles, at latitude 34 degrees, and want the best all-year output.
- Year-round tilt: equal to the latitude, so about 34 degrees from horizontal.
- Summer bias: 34 - 15 = 19 degrees, a shallower angle for the high summer sun.
- Winter bias: 34 + 15 = 49 degrees, a steeper angle for the low winter sun.
- Orientation: face the panel true south, since Los Angeles is in the Northern Hemisphere.
Reference: optimal tilt by latitude
Approximate fixed tilt angles for the three common strategies, by site latitude.
| Latitude | Year-round | Summer (-15) | Winter (+15) |
|---|---|---|---|
| 10 (tropical) | 10 | 5 (near flat) | 25 |
| 25 (Miami, Dubai) | 25 | 10 | 40 |
| 35 (Los Angeles) | 35 | 20 | 50 |
| 42 (New York, Rome) | 42 | 27 | 57 |
| 52 (London, Berlin) | 52 | 37 | 67 |
Common pitfalls
- Laying panels flat to "catch more sky". Except near the equator, a horizontal panel sheds the low-angle winter sun and collects dirt and water. Tilt to at least roughly your latitude.
- Facing the wrong way. Tilt only helps if the panel also faces the equator: true south in the north, true north in the south. Magnetic south is not the same as true south.
- Chasing perfection on a fixed mount. A tilt within about 10 to 15 degrees of optimal loses only a few percent of annual output, so matching a roof pitch is often fine.
- Ignoring snow and self-cleaning. In snowy climates a steeper tilt sheds snow and lets rain rinse dust off, which can matter more than the theoretical optimum.
- Forgetting shading. The best tilt is worthless if a tree or chimney shades the array at midday. Clear the solar window before optimising the angle.
Frequently asked questions
What is the best tilt angle for solar panels?
For year-round output from a fixed panel, set the tilt roughly equal to your latitude. A site at 35 degrees latitude wants about a 35 degree tilt. This keeps the average angle of incidence close to ideal across the seasons. If you favour one season, tilt about 15 degrees shallower for summer or 15 degrees steeper for winter.
Should I change my panel tilt with the seasons?
Adjusting twice a year can lift annual yield by a few percent: tilt shallower (latitude minus about 15 degrees) for the high summer sun and steeper (latitude plus about 15 degrees) for the low winter sun. Whether it is worth the effort depends on roof access. Most fixed home installs simply use the latitude angle and accept the small loss.
Which direction should solar panels face?
In the Northern Hemisphere panels should face true south, and in the Southern Hemisphere true north, so they track the sun across the day. Use true south, not magnetic south, since the two differ by the local magnetic declination. Correct azimuth matters as much as tilt; a panel tilted perfectly but facing the wrong way loses significant output.
Can I just lay solar panels flat?
Only near the equator does a near-flat panel work well. At higher latitudes a flat panel poorly captures the low-angle winter sun and tends to collect dust, leaves, and standing water that reduce output and shorten life. A tilt of at least roughly your latitude both improves energy capture and helps rain rinse the surface clean.
How much output do I lose if my tilt is not optimal?
Surprisingly little for small mismatches. A fixed tilt within about 10 to 15 degrees of optimal typically loses only a few percent of annual energy, which is why matching an existing roof pitch is usually acceptable. Large errors, facing the wrong way, or shading at midday cost far more than a modest tilt deviation.