Siting and sizing solar panels — tilt and azimuth by season and latitude, daily-output math, and DC wiring.
Tilt angle
| Season | Panel tilt |
|---|---|
| Spring / Fall | Set to your latitude (latitude 38° → panels at 38°). |
| Summer | Latitude minus 10–15° (38° → 23–28°). |
| Winter | Latitude plus 10–15° (38° → 48–53°). |
These angles are for maximum performance. For a fixed, year-round setting, use the Spring/Fall (latitude) value. For reference, a 4:12 roof pitch is 18.5°, 6:12 is 28.5°, 8:12 is 33.8°, and 12:12 is 45°.
Azimuth (east–west aim)
Point the panels due south with a compass, then rotate by your local magnetic declination — if your declination is 5° East, rotate the panels 5° East. If you don’t know your declination, approximate it: the Mississippi River is about 0°, the NW tip of Washington about 20° East, and the NE tip of Maine about 20° West.
Simple daily power output
E = (P × N × T) / 1000
Sunlight hours vary by region and season — check the solar-radiation map for your area.
