Inter-Row Spacing (GCR) Calculator
Shadow-free row pitch for ground-mount & flat roofs
Free · No sign-up · Computed instantly on your device
Row Geometry
Minimum spacing so rows don’t shade each other — essential for ground-mount and flat-roof ballasted tables.
Module dimension up the slope × modules per row (e.g. 2.28 m = one portrait panel)
Baseline: no shading at solar noon on the winter solstice. Stricter designs guarantee a clear 9 AM–3 PM window and need wider gaps. Tighter spacing raises GCR (more kWp per acre) but increases mutual shading losses.
Minimum row pitch
2.74m
Front-edge to front-edge, row to row · winter-noon sun at 47.6° elevation
Clear gap
0.54 m
between row edges
Panel rise
0.59 m
top edge height
GCR
0.83
ground coverage ratio
Inter-Row Shadow Geometry
Side elevation, drawn to scale from your inputs.
About This Calculator
On flat roofs and ground mounts, row spacing is the trade between land and light: pack rows tighter and you fit more kW, but each row shades the one behind it in the low winter sun. This calculator returns the minimum row pitch that keeps rows shadow-free at solar noon on the winter solstice — the standard design baseline — plus the resulting ground coverage ratio (GCR).
The geometry is pure trigonometry: the winter-noon solar elevation at your latitude sets the shadow length of the raised panel edge. A GCR up to ~0.45 is conservative, ~0.45–0.6 is a balanced land-use choice, and denser designs need explicit annual shading-loss simulation before anyone signs a generation guarantee.
How the Calculation Works
To stop one row shading the next, the calculator uses the winter-solstice solar-noon sun elevation (90° − latitude − 23.45°), the vertical rise of the table (length × sin tilt) and the shadow length it casts (rise ÷ tan elevation). Row pitch is the table’s horizontal footprint plus that shadow gap, and the ground coverage ratio (GCR) is table length divided by pitch.
This is the minimum shadow-free spacing at solar noon. Designs that must stay shade-free from about 9 AM to 3 PM need a wider pitch and therefore a lower GCR — simulate before committing to a generation guarantee. See GCR for typical ranges.
Worked example (the calculator’s defaults)
- Table length 2.28 m, tilt 15°, latitude 19°N.
- Winter-noon elevation: 90 − 19 − 23.45 = 47.55°.
- Rise 2.28 × sin 15° = 0.59 m, so the shadow gap is 0.54 m; the table’s footprint is 2.28 × cos 15° = 2.20 m.
- Row pitch ≈ 2.74 m and GCR ≈ 0.83 at the solar-noon baseline; a 9 AM–3 PM shade-free design needs a wider pitch.
Go Deeper
Frequently Asked Questions
- What Is Ground Coverage Ratio (GCR)?
- The ratio of module area to ground area — collector length divided by row pitch. GCR 0.5 means half the land is covered by modules. Higher GCR fits more capacity per acre but increases inter-row shading losses.
- Is Winter-Solstice-Noon Spacing Enough?
- It is the accepted baseline. Stricter designs guarantee a shade-free window from 9 AM to 3 PM on the solstice, which requires wider spacing — worth it when a performance-ratio guarantee is on the line.
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