Solar Geometry
Solar Row Spacing & Shading Gap Calculator
Find the minimum gap between panel rows to avoid shading
Updated July 12, 2026 · Live
What this tool does
Works out the minimum row spacing for ground-mounted or flat-roof solar so one row does not shade the next at low winter sun.
Enter the panel slope length, tilt angle and the lowest winter sun elevation; the calculator returns the minimum row pitch and the clear gap behind each row.
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Formula Used
How the solar row spacing & shading gap works
The tilted panel rises a vertical height equal to its slope length times the sine of the tilt. At the design sun elevation that height casts a shadow behind it of the rise divided by the tangent of the sun angle. The minimum row pitch — front edge of one row to front edge of the next — is the panel’s horizontal footprint plus that shadow gap.
What you enter
Enter the panel slope length, tilt angle and the lowest winter sun elevation; the calculator returns the minimum row pitch and the clear gap behind each row. Every field is editable, and the result recalculates the moment you change a value.
Reading the result
Space rows at least at the pitch shown to keep the array unshaded at your chosen winter sun angle. Tighter spacing packs more panels in but loses winter output to inter-row shading.
Safe by design
This calculator does the arithmetic of sizing — quantities, geometry and cost. It deliberately stops at the line a certified installer must sign off. It will never tell you a cable or fuse size, an earthing arrangement, a battery charge voltage, or a roof structural load: those are regulated calculations where a wrong number causes fire, electrocution or collapse. All electrical work must be carried out by a qualified, certified installer, and this page is not an installation guide.
Assumptions and limits
This models a straight-on shadow at one sun elevation. It does not account for the sun moving east and west through the day, ground slope, or nearby obstructions. Choosing a lower design sun angle widens the rows and is more conservative.
Using it with the rest of BuildMetricLab
This calculator is one step in planning a system. Pair it with the other solar sizing, geometry and cost tools to go from an energy figure to a panel count, a layout and a costed bill of materials. Every BuildMetricLab tool runs entirely in your browser — no sign-up, nothing sent to a server, and the formula is shown on the page so the maths can be audited.
Sources & methodology
Works out the minimum row spacing for ground-mounted or flat-roof solar so one row does not shade the next at low winter sun. Every result is calculated from the values you enter, all inputs are editable, and no time-sensitive prices or tariffs are embedded.
Frequently asked questions
What sun elevation should I design for?
Designers commonly use the midday sun angle around the winter solstice, often 15–25° in mid-latitudes. A lower angle gives wider, more conservative spacing.
What is the difference between pitch and gap?
The gap is the clear ground behind a row that must stay unshaded; the pitch is front-edge to front-edge, which is the gap plus the panel’s own footprint.
Does closer spacing lose much energy?
It mainly costs winter yield, when the sun is lowest and shadows are longest. Summer output is affected far less.
Does this apply to a pitched roof?
Roof-parallel panels do not shade each other. This tool is for tilted rows on flat roofs or the ground, where one row can shade the next.
Spotted something off?
Calculations or display — let us know.