SettingsSettings for this calculationUS
The panel dimension running up the tilt, not across it.
For a portrait row that is the panel's long side and for a landscape row its short one, which is why the same array laid the other way needs different spacing. Where panels are stacked two high on one frame, use the whole frame's slope length — the shadow is cast by the top of the highest one.
Degrees. This is the figure the whole trade-off turns on.
Tilt more and each panel catches more sun and throws a longer shadow; tilt less and they pack closer but earn less each. On a site that is short of depth the answer is often a flatter array rather than fewer rows, and this page is how you price that choice.
Degrees above the horizon at the worst moment you will accept.
The usual criterion is no shading between 9 am and 3 pm on the winter solstice. At solar noon on that day the sun reaches about (90 − your latitude − 23.4) degrees, and it is lower at 9 am, so take the altitude at the hour you actually care about rather than at noon. A smaller figure here pushes the rows apart quickly — it is in the denominator.
Front of the first row to the back boundary.
Measured in the direction the rows step back, which is the slope of the site rather than its plan north. Leave out the access and maintenance strips before entering it; this figure is what the array itself may occupy.
Row pitch, front to front
14.6 ft
61% of the pitch is clear ground the shadow needs, at a ground coverage ratio of 39%. 5 row(s) fit the depth given.
- Clear gap behind each row
- 8.93 ft
- Ground the panel occupies
- 5.63 ft
- Height the row stands
- 3.25 ft
- Ground coverage ratio
- 38.67 %
- Rows that fit the depth
- 5 rows
They open the calculator with your figures already in it
Solar Array Row Spacing and Shading Pitch Calculator: 14.56 ft — shown in imperial, US market. The link sets both, so the result they see is the one on your screen.
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How this was calculated
Formula source(s)
- Geometry: a panel of slope length L at tilt β stands L·sin β high and occupies L·cos β of ground, so at sun altitude α its shadow reaches (L·sin β)/tan α behind it and the row pitch is the sum of the two
- The usual design criterion is no row-to-row shading between 9 am and 3 pm on the winter solstice, which is when the sun is lowest in the working day
- Ground coverage ratio is the panel footprint divided by the row pitch — the share of the site that is under panel, and the direct cost of tilting further
Inputs used
- Panel length up the slope
- 6.5 ft
- Tilt from horizontal
- 30
- Design sun altitude
- 20
- Depth available for rows
- 66 ft
Intermediate steps
- Clear gap behind each row
- 8.93 ft
- Ground the panel occupies
- 5.63 ft
- Height the row stands
- 3.25 ft
- Ground coverage ratio
- 38.67 %
- Rows that fit the depth
- 5 rows
Confidence note: 61% of the pitch is clear ground the shadow needs, at a ground coverage ratio of 39%. 5 row(s) fit the depth given.
What this calculation does not cover
- The shadow is taken at the array's worst moment with the sun square to the rows. As the sun swings off that line its shadow shortens, so a full azimuth model returns a SMALLER pitch than this one — the error here is in the safe direction, and it is deliberate.
- Flat ground is assumed. A slope falling away from the sun lets rows sit closer and a slope rising behind them pushes them further apart, and neither is a small effect: a few degrees of ground slope moves the pitch more than a few degrees of tilt does.
- Row-to-row shading only. Nothing here sees a chimney, a flue, a parapet, a tree or the next building, and on a roof those are usually what actually decides the layout.
- It is a geometric limit, not a yield model. Accepting a little winter shading is a legitimate design choice that fits more panels on the site and can produce more annual energy than a sparser array — this page tells you what you are trading, not which trade is right.
Computed in your browser — nothing you enter is uploaded. Presented in US customary units and US trade terminology. Where a formula follows a published standard, that standard and its edition are cited beside it on this page; where none governs, the page says so. Local amendments override model codes — verify against the code in force where you build.
Sources checked 2026-09-23 · v1.0.0
Regulatory standards & verification citations3
- Geometry: a panel of slope length L at tilt β stands L·sin β high and occupies L·cos β of ground, so at sun altitude α its shadow reaches (L·sin β)/tan α behind it and the row pitch is the sum of the two
- The usual design criterion is no row-to-row shading between 9 am and 3 pm on the winter solstice, which is when the sun is lowest in the working day
- Ground coverage ratio is the panel footprint divided by the row pitch — the share of the site that is under panel, and the direct cost of tilting further
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