Solar panel row spacing calculation
Row spacing is the gap that keeps the front row's shadow off the row behind it. Designers usually size it for the winter solstice, when the sun is lowest. Here is the formula with worked examples.
The formula
Gap d = h ÷ tan α
Pitch = L × cos β + dL: sloped length of the table, β: tilt, α: sun altitude at the design time. Equator-facing rows on flat ground.
Which sun altitude to use
At solar noon on the winter solstice the sun altitude is 90° − latitude − 23.44° (northern hemisphere). At 36° N that is about 30.6°. Sizing only for noon leaves shading in the morning and afternoon, so a common rule is "no shading between 9:00 and 15:00 solar time on the winter solstice". The sun is then lower and off to the side, so you use the north-south component of the shadow.
Example: 4 m table at 30° tilt
h = 4 × sin 30° = 2.0 m, and the table's footprint is 4 × cos 30° = 3.46 m.
| Latitude | Design rule | Sun altitude | Gap d | Pitch |
|---|---|---|---|---|
| 34.5° | Solstice noon | 32.1° | 3.19 m | 6.65 m |
| 36.0° | Solstice noon | 30.6° | 3.39 m | 6.85 m |
| 37.5° | Solstice noon | 29.1° | 3.60 m | 7.06 m |
| 34.5° | Solstice 9:00 to 15:00 | 18.0° | 4.50 m | 7.96 m |
| 36.0° | Solstice 9:00 to 15:00 | 16.9° | 4.83 m | 8.29 m |
| 37.5° | Solstice 9:00 to 15:00 | 15.8° | 5.21 m | 8.67 m |
The 9:00 to 15:00 rows use the sun's altitude and its azimuth (about 43° from due south) to get the north-south shadow length.
What happens if rows are tighter
Tighter rows put more panels on the same land but add winter shading loss. Depending on land cost, grid capacity and power price, a little shading for more capacity can pay off. Compare annual energy for several spacings rather than fixing one number.
On sloped ground
- Slope facing the equator: back rows sit higher, so you can reduce the gap.
- Slope facing away from the equator: back rows sit lower, so you need a bigger gap.
- East or west slopes: each table ends up at a different height and angle. A 3D terrain model is far more accurate than hand calculation.
Compare spacings in seconds
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Try it free →FAQ
Is there a standard row spacing for solar panels?
There is no single standard. Most designers size it from the winter solstice sun, then compare energy against land use. Local rules may set setbacks from roads or property lines.
What is the difference between pitch and gap?
The gap is the empty ground between the back edge of one table and the front edge of the next. Pitch is front edge to front edge: table footprint plus gap.
Does a lower tilt allow tighter spacing?
Yes. A lower tilt reduces the height difference, so shadows are shorter. Each panel may make slightly less energy.