Solar Panel Angle Calculator
This solar panel angle calculator gives tilt from your latitude: at 35° the year-round tilt is 35°, summer is 20° (latitude minus 15°), winter is 50°.
Solar panel angle calculator formula
A solar panel angle calculator gives three tilt angles from one number, your latitude. The formulas are year-round tilt = latitude, summer tilt = latitude − 15°, and winter tilt = latitude + 15°.
Tilt is measured from flat. A panel lying flat is 0°, and one standing upright is 90°. Enter your latitude in degrees and the calculator returns all three angles. The default of 35° gives 35°, 20° and 50°.
You can find your latitude on a map app or a weather site. Use a positive number for the northern hemisphere. In the southern hemisphere, enter the number without the minus sign, and face the panels north.
Worked examples
Example 1 is a ground mount near 35° latitude.
- Year-round: 35°
- Summer: 35 − 15 = 20°
- Winter: 35 + 15 = 50°
Example 2 is a cabin at 47° latitude.
- Year-round: 47°
- Summer: 47 − 15 = 32°
- Winter: 47 + 15 = 62°
An adjustable rack that moves between the summer and winter angles changes the tilt twice a year. A fixed rack picks the year-round value.
Tilt angles by latitude
| Latitude | Summer | Year-round | Winter |
|---|---|---|---|
| 25° | 10° | 25° | 40° |
| 30° | 15° | 30° | 45° |
| 35° | 20° | 35° | 50° |
| 40° | 25° | 40° | 55° |
| 45° | 30° | 45° | 60° |
| 50° | 35° | 50° | 65° |
Matching a roof pitch
On a roof, the panels usually lie on the roof, so the tilt is the roof’s angle. Roof pitch is written as a rise over a run of 12.
| Roof pitch | Angle |
|---|---|
| 3/12 | 14.0° |
| 4/12 | 18.4° |
| 6/12 | 26.6° |
| 8/12 | 33.7° |
| 10/12 | 39.8° |
| 12/12 | 45.0° |
At 35° latitude, an 8/12 roof at 33.7° is almost exactly the year-round tilt. A 4/12 roof at 18.4° is flatter than the ideal, but the loss in yearly output from a modest difference is usually small. A solar installer can run the numbers for your roof and give you a production estimate.
Direction matters as much as angle
- In the northern hemisphere, point the panels true south. In the southern hemisphere, point them true north.
- True south is not the same as magnetic south on a compass. Check your local declination.
- East and west faces make less in total but spread output across the day, which can suit some households.
- Shade from trees, chimneys and neighboring buildings can cost more than a small angle error. Check the sun path on the site.
How to use the result
- For a ground mount you can adjust, use the summer and winter angles and change them in spring and fall.
- For a fixed ground mount, use the year-round angle, or one a little flatter if most of your use is in summer.
- For an off-grid system, size for the winter, when the sun is low and the days are short.
- For a roof mount, compare the roof’s angle to the calculator, then ask an installer how much production changes.
The solar panel calculator sizes the number of panels, and the solar battery calculator sizes storage.
Common mistakes
- Using the wrong sign for the southern hemisphere. The angles use the absolute value of latitude, and the panels face north.
- Measuring the tilt from vertical. The calculator’s angles are from flat.
- Assuming that a steeper panel always makes more power. It does in winter and loses in summer.
- Ignoring snow. A steeper panel sheds snow better, which helps in cold climates.
- Skipping the safety side. Roof loads, wiring and permits are regulated, and rooftop and electrical work should be done by qualified, licensed people.
Related calculators
If your roof angle is unknown, the roof pitch calculator converts rise and run to degrees. For cost decisions, compare options in the solar lease vs buy calculator.
Frequently asked questions
What tilt angle should a fixed solar panel use?
The rule of thumb in this calculator is that the year-round tilt equals your latitude. At 35° latitude that is 35°. Many designers use a tilt a little lower than latitude to favor summer output, so treat the number as a starting point and check it with a design tool such as NREL's PVWatts.
How is the summer tilt angle calculated?
Summer tilt is the latitude minus 15°. At 35° latitude, summer tilt is 20°. The sun is higher in summer, so a flatter panel faces it more directly. Use it if you adjust your panels by season or if most of your use falls in summer.
How is the winter tilt angle calculated?
Winter tilt is the latitude plus 15°. At 35° latitude, winter tilt is 50°. The sun sits low in winter, so a steeper panel faces it more directly and also sheds snow more easily. It matters most for off-grid systems that need winter output.
Is this rule of thumb accurate enough for a real installation?
It is good for planning and for adjustable ground mounts. For a roof, the roof pitch and direction usually set the angle, and the loss from a small mismatch is modest. Shading, orientation, local weather and the roof's structure matter too, so use a licensed solar installer for the design.
Estimates only. Verify quantities with your supplier before purchasing.