Solar Panel Row Spacing Calculator
Work out how far apart to set rows of panels so one row doesn't shade the next, using your latitude, panel size and tilt.
Tilted panels cast a shadow behind them. Set the rows too close and the front row shades the back one every winter morning and afternoon. Set them too far apart and you waste ground or roof you could have filled with panels.
This calculator is for people laying out a ground mount or a flat-roof array: installers, designers and homeowners with room to choose. Enter your ZIP code, the panel size and the tilt, and it gives the row spacing, the clear gap and how much of the ground the panels cover.
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Planning estimates only. Check the layout against your site, local fire code setbacks and the racking maker's instructions. Data as of October 2026.
How this calculator works
The sun is lowest on December 21, so that’s the day that sets the spacing. The tool works out how high the sun is and which way it points at the hour your shading window starts and ends, for your latitude. It then finds how long a shadow the top edge of the front row throws toward the north. The row spacing is that shadow plus the flat width the panel itself covers.
In Austin, a 5.65-foot panel at a 25-degree tilt needs 9.6 feet from the front edge of one row to the front edge of the next. The same panel at the same tilt in Seattle needs 17.5 feet, because the winter sun there stays so much lower. Ground use falls from 59% to 32%.
Choosing the shading window
Most designs keep the array clear of shade between 9 am and 3 pm. The first and last hour of the day give little energy, so a stricter window costs you ground for a small gain. The tool shows the 10 to 2, 9 to 3 and 8 to 4 results side by side, so you can see what each hour costs you in extra spacing.
Tilt and spacing
A flatter tilt shortens the shadow. In Austin, dropping from 25 degrees to 10 cuts the spacing from 9.6 feet to 7.4. The panels then make a little less energy over the year, so it comes down to what’s scarce on your site: space or sunlight. The second table shows the spacing at other tilts. The Solar Panel Tilt Angle Calculator shows what each angle does to the energy.
Tip: measure the roof or field in the north to south direction first, then use the total depth figure. It tells you how many rows fit before you buy racking.
What it doesn’t do
- It assumes flat ground. A slope that falls to the north needs more space and one that falls to the south needs less.
- It only handles the shade between rows. Trees, buildings and fire-code walkways are on top of this spacing.
Where the numbers come from
- Sun position from standard solar geometry, using a solar declination of -23.45 degrees on December 21 for the lowest sun of the year.
- Latitude for each ZIP code comes from the same location data as the other SolarYP tools.
Questions
How far apart should solar panel rows be?
It depends on your latitude, the tilt and the panel size. In Austin a 5.65-foot panel at 25 degrees needs about 9.6 feet from the front edge of one row to the next. In Seattle the same panel needs about 17.5 feet. Enter your own numbers above.
Why does the tool use December 21?
That’s the day the sun is lowest in the northern hemisphere, so it throws the longest shadows. If rows are clear of each other then, they’re clear on every other day of the year.
What does ground use mean?
It’s the length of the panel along its slope divided by the row spacing. A higher number means you fit more panels on the same land. Tilting the panels flatter or using a shorter shading window raises it.
Should I use 9 am to 3 pm or 8 am to 4 pm?
9 to 3 is the usual choice. The sun is weak in the first and last hour of the day, so the extra ground that 8 to 4 asks for buys very little energy. At high latitudes the sun may not be up at 8 am in December at all.
Are these clock times?
No, they’re solar times. At solar noon the sun is due south. In winter that is within about an hour of 12 pm on the clock, depending on where you are in your time zone.
Do I measure the spacing along the ground or along the roof?
Along the ground, from north to south. On a flat roof that’s the same as along the roof. On a ground mount with a slope, adjust for the slope.
Can I use this for panels on a pitched roof?
Usually you don’t need to. Panels mounted flush on a roof lie in one plane and don’t shade each other. This tool is for racks that tilt the panels up off a flat surface.
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