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Solar Panel Tilt Angle Calculator: Latitude & Roof Pitch
Find a starting tilt angle for a fixed solar array and convert roof rise/run into degrees. This is a geometry-based planning tool, not a site-specific energy simulation.
How this solar panel angle calculator works
The annual starting tilt equals the absolute latitude, measured up from horizontal. The summer comparison uses latitude minus 15 degrees, and winter uses latitude plus 15 degrees, each limited to 0–90 degrees. These seasonal offsets are a rule of thumb for comparison, not an optimized recommendation.
The facing direction is toward the equator: generally south in the northern hemisphere or north in the southern hemisphere. At the equator, orientation and actual conditions need a project-specific review.
Worked example: 35° north, 6:12 roof
The starting fixed tilt is 35°, with 20° summer and 50° winter comparison angles. Roof pitch = arctan(6 / 12) × 180 / π = 26.6°. The difference from the latitude-based starting angle is 8.4°. That difference alone does not quantify energy lost and does not establish a need for tilted roof racks.
Roof pitch is not an energy-yield calculation
A flush-mounted array normally follows the roof plane. Roof azimuth, shading, horizon, mounting, wind loading and installation economics matter. A small angle difference may be outweighed by structural or shading constraints. Compare realistic mounting options with an hourly simulation such as PVWatts.
Latitude is a starting point
DOE's PV design guidance describes fixed-array tilt and latitude as useful design inputs. Your actual best choice may change when the goal is winter generation, evening energy value or snow management. This tool does not include hourly weather, shading or time-of-use tariffs.
Does a steeper panel always produce more?
No. Steeper angles change the seasonal distribution of sunlight received. They can help one season and reduce another. Do not change structural mounts based on this calculator; ask the installer to compare modeled annual output, weather exposure and the approved racking design.