Solar Panel Tilt Calculator
Panel tilt, facing, and seasonal pair from latitude.
What it does
Solar panels harvest most facing the sun dead on, and the sun rides lower in winter than summer. Latitude plus seasonal arithmetic sets fixed mounts near their yearly best.
The tool above takes latitude with season. It returns tilt degrees, compass facing, and the seasonal pair.
The default latitude 40 winter tilts 55 degrees facing true south, with summer 25 in the pair. The latitude 30 summer case tilts 15.
Energy department solar guidance and photovoltaic lab research bracket fixed tilt near latitude with winter plus 15 and summer minus 15. Southern sites mirror toward true north.
Angles start installs; roofs finish them. Shade, wind loads, and mounting limits override pure math, while adjustable racks earn their keep with twice yearly swings.
How to use
- Type the latitude.
- Pick year, winter, or summer.
- Read tilt first.
- Read facing beside it.
- Read the seasonal pair last.
- Correct magnetic to true.
Formula
- lat
- Site latitude, -65 to 65.
- season
- Year, winter, or summer season.
- tilt
- Degrees from horizontal.
DOE solar planning guidance and NREL photovoltaic research frame tilt near latitude with plus 15 winter and minus 15 summer seasonal rules. Southern latitudes mirror with true north facing. Rules plan fixed mounts; shade and roof geometry govern final installs.
Worked example
Example: winter at latitude 40
Defaults: latitude 40, winter.
- Site: latitude 40, winter season.
- Rule: winter tilt = latitude + 15.
- Tilt: 40 + 15 = 55 degrees.
- Face: northern hemisphere faces true south.
- Pair: summer 25 with winter 55.
- Tool shows 55° tilt, Faces true south, Summer 25°, winter 55°.
Reference table
| Season | Rule | At 40 |
|---|---|---|
| Year round | Latitude | 40° |
| Winter | Latitude + 15 | 55° |
| Summer | Latitude minus 15 | 25° |
| Equator | Flat | 0° |
Limits
- Fixed mount planning rules.
- Shade and roof override.
- Tropics gain little from tilt.
- Snow and wind apart.
Common mistakes
- Aiming magnetic south.
- Ignoring seasonal swings.
- Tilting steep in the tropics.
- Forgetting shade surveys.
- Mixing tilt with azimuth.
Try it yourself
Quick checks. Answers sit tucked under each question.
Latitude 30, summer?
15° tilt facing true south, pair summer 15, winter 45.
Latitude minus 40, winter?
55° tilt facing true north, pair summer 25, winter 55.
Latitude 80?
Past 65 sits outside planning bands: enter -65 to 65.
Questions
Tilt rules?
Year equals latitude, winter adds 15, summer subtracts 15 floored at 0. Adjustable mounts beat fixed picks.
Face which way?
South in the north hemisphere, north in the south. Equator mounts lie flat or either way.
Gains?
Up to 10 to 25% seasonal harvest, less at low latitudes where the sun rides high.
True or magnetic?
True south, not magnetic: correct for declination before aiming.
Roof limits?
Yes, shade, tilt limits, and wind loads override pure angles. Microinverters forgive partial shade.
Adjust how often?
Twice yearly swings capture most adjustable gains; monthly tweaks add crumbs.