A solar shading calculator determines the minimum row spacing for ground-mounted or flat-roof solar arrays using your latitude and panel tilt angle. It models shadow length at winter solstice — the worst case — to ensure zero inter-row shading during productive sun hours.
Array Parameters
Spacing Results
Shadow Projection Winter Solstice
Solar Site Survey Gear
Before installing a large ground-mount solar array, you must map the site's true south (or north, in the southern hemisphere) and measure local horizon shading from trees or buildings. A simple smartphone compass is easily thrown off by magnetic interference. We highly recommend using a professional sighting compass for locking in your array's azimuth. To quickly measure the distance between rows during layout without dragging a dirty tape measure through the mud, use a laser distance measurer.
How to Calculate Solar Panel Row Spacing
When installing multiple rows of solar panels (whether on a flat roof or ground mount), the front row casts a shadow backward. If this shadow falls onto the next row, it can severely cripple your energy production, as shaded solar cells drag down the performance of the entire string. To prevent this, you must calculate the minimum row spacing based on the Winter Solsticethe day of the year when the sun is at its lowest angle in the sky, casting the longest shadows. SunClear takes your site's latitude, your panel dimensions, and your tilt angle, and calculates the exact solstice sun angle using advanced solar geometry. It then outputs the precise minimum distance required between rows to guarantee 100% shade-free operation during peak winter daylight hours.
Frequently Asked Questions
How do you calculate solar panel row spacing to avoid shading?
Row spacing depends on latitude, panel tilt angle, and panel height. The critical formula uses the winter solstice sun angle (lowest of the year): Row Spacing = Panel Height × sin(tilt) / tan(solar elevation angle). At 40° latitude, the winter solstice sun is only about 26.5° above the horizon, requiring significant spacing to prevent inter-row shading.
Why is winter solstice used for solar shading calculations?
The winter solstice (December 21 in the Northern Hemisphere) produces the lowest sun angle and longest shadows of the year. If your row spacing prevents shading at winter solstice noon, it will be shade-free for the entire year. Some designers use 9AM-3PM on winter solstice for a more conservative, real-world calculation window.
Does row spacing affect total solar panel output?
Yes — wider spacing means fewer panels fit in the same area, reducing total system capacity and energy output. But panels shaded by the row in front lose 20-80% of their output. The optimal balance depends on land costs vs. energy value. Ground-mounted farms with cheap land use wider spacing; constrained rooftops use tighter spacing and accept some winter shading.