Solar Panel Row Spacing Calculator (Avoid Shading)
Distance between rows of tilted solar panels so that one row does not shade the next at noon on the winter solstice, with the ground coverage ratio.
Results
The dashed line marks the value you entered.
What this tool does
The sun is lowest, and shadows longest, at the winter solstice, so rows are spaced for that day: the noon sun stands 90° − latitude − 23.44° above the horizon, and each row casts a shadow of length L·sin β ÷ tan α behind it. Spacing for noon alone is the minimum; many designers prefer to stay shade-free from about 9:00 to 15:00, which needs a larger gap, and the formula assumes level ground and rows facing the equator. Steeper tilts and higher latitudes lengthen the shadow quickly, which is why high-latitude arrays often use lower tilts to pack more panels in.
Formula
α = 90° − |latitude| − 23.44° · pitch = L cos β + L sin β ÷ tan α (L = panel length along the slope, β = tilt)
Variables
| Symbol | Meaning | Unit |
|---|---|---|
la | Latitude | ° |
lp | Length of the panel along its slope | m |
tl | Tilt of the panels from horizontal | ° |
PI | Distance between rows (front edge to front edge) | m |
GP | Clear gap between the rows | m |
AL | Sun height at noon on the winter solstice | ° |
GC | Ground coverage ratio (panel length ÷ pitch) | — |
ST | Is the noon rule workable here? | — |
Worked example
- Latitude40 °
- Length of the panel along its slope1.7 m
- Tilt of the panels from horizontal30 °
- Distance between rows (front edge to front edge)3.17 m
- Clear gap between the rows1.70 m
- Sun height at noon on the winter solstice26.6 °
- Ground coverage ratio (panel length ÷ pitch)0.54
- Is the noon rule workable here?Yes
Limitations
- Declination and the equation of time come from Spencer's 1971 series, good to a small fraction of a degree. Atmospheric refraction, which lifts the Sun by about half a degree at the horizon, is not included.
- The formula assumes ideal conditions: no friction losses, no air resistance and no efficiency losses unless you enter them.