Inter-Row Spacing for Solar Panels: Formula & GCR

Last updated: November 2026.

Rows of panels shade each other when the sun is low, so the gap between them has to be set from the sun angle you care about. This guide gives the formula, a spreadsheet version and the GCR trade-off.

SurgePV publishes this guide and sells solar design software. PVsyst and SAM are solar modeling programs. They appear below only as documentation sources.

Inter-Row Spacing Formula and Worked Example

Use this block first. The seven steps below explain each input.

Rows are level, identical and parallel. W is the sloped width of the panels across the row. β is the tilt angle above horizontal. α is the sun’s altitude, its angle above the horizon.

• Height rise: H = W × sin(β)
• Horizontal footprint: B = W × cos(β)
• Clear gap, sun square-on to the rows: G = H ÷ tan(α)
• Clear gap, sun at azimuth difference γ from the row normal: G = H × cos(γ) ÷ tan(α)
• Pitch: P = B + G

The cos(γ) form is plain geometry. The shadow of height H has horizontal length H ÷ tan(α) along the sun’s direction. Only the part of it that points straight at the next row reaches that row. Here γ is the angle between the sun’s azimuth and the direction the rows face. The row normal is the line at right angles to the row. PVsyst’s profile angle p is the sun’s height measured in the vertical plane perpendicular to the row. Geometrically tan(p) = tan(α) ÷ cos(γ). So you can also write the same gap as G = H ÷ tan(p).

Worked example. A hypothetical row has W = 1.134 m and β = 30°, at 50° N on the winter solstice, with the sun due south and the rows facing south. NASA lists Earth’s obliquity as 23.44°. Obliquity is the tilt of Earth’s axis. So the solstice declination, the sun’s angle north or south of the equator, is about −23.44°.

1. Noon altitude: α = 90° − |50° − (−23.44°)| = 16.56°.
2. H = 1.134 × sin(30°) = 0.567 m.
3. B = 1.134 × cos(30°) = 0.982 m.
4. G = 0.567 ÷ tan(16.56°) = 1.907 m.
5. P = 0.982 + 1.907 = 2.889 m.

So the next row’s lower edge sits 2.89 m behind this row’s lower edge. The clear gap is 1.91 m.

Row Gap per Metre of Height by Latitude

Because G = H ÷ tan(α), the clear gap grows with H. The table gives G per metre of height rise for the winter-solstice noon check in either hemisphere. In the Southern Hemisphere, use the June solstice. Altitude is α = 90° − latitude − 23.44°. The last column is 1 ÷ tan(α).

To use it, multiply by H. Take 40° latitude and the example row (H = 0.567 m, B = 0.982 m). Then G = 0.567 × 2.00 = 1.134 m and P = 0.982 + 1.134 = 2.116 m. The table covers one instant. At 60° the sun is only 6.56° above the horizon at noon, so the noon-based gap grows fast. Compare annual yield before you adopt it.

Solar Panel Row Spacing Calculator in a Spreadsheet

A row spacing calculator needs four inputs: panel width W, tilt β, latitude and the sun position you want to clear. Use the winter-noon case above, with rows facing the equator. Put W in A1, tilt in B1 and latitude in C1. This spreadsheet formula gives pitch in the same unit as W:

=A1*COS(RADIANS(B1))+A1*SIN(RADIANS(B1))/TAN(RADIANS(90-ABS(C1)-23.44))

With W = 1.134, tilt = 30 and latitude = 50 it returns 2.889. For a specific date and hour, use the sun angle calculator. It gives solar elevation, azimuth, shadow length and the inter-row spacing they imply.

How the Cross-Row Gap Changes Through the Day

In the table below, noon gives the shortest cross-row gap, not the longest. It uses the same row (H = 0.567 m) at 50° N on the winter solstice, with rows facing south. Altitude and azimuth come from the standard solar-position equations. The hour angle is HRA = 15° × (hours from solar noon), per PVEducation. The azimuth equation is on its azimuth page. Then G = H × cos(γ) ÷ tan(α).

Check one row: at 09:00, G = 0.567 × cos(40.8°) ÷ tan(6.45°) = 0.567 × 0.757 ÷ 0.1130 = 3.80 m. A noon-based gap of 1.91 m therefore leaves the next row partly shaded in the early morning and late afternoon of the solstice. Step 5 covers whether that matters for energy.

Step 1: Define the distances before calculating

A drawing labelled “spacing” can mean several different measurements. State which one you mean. Use the same meaning in the model and the installation plan.

Here, P = B + G. Mounting clearance above the ground is not the same as H. Equal mounting heights cancel out in this simplified two-row calculation. Rows at different elevations do not cancel out.

W may be one module’s dimension. It may also be the full width of a table with several modules up its slope. Include the spaces between modules and any inactive structure in the geometry when they affect shadows. Do not just use a product’s advertised “width”. Check how it is mounted first.

Step 2: Gather site, equipment and design inputs

Record the exact module dimensions, table arrangement, tilt from horizontal, row azimuth, mounting heights and ground or roof elevations. Also record obstructions. Record the usable area after you remove required access paths and exclusion zones.

Specify the date and time you are checking, plus latitude, longitude, time zone and the solar-position convention. Latitude affects the sun path. But latitude alone cannot give the full sun position for any given date and time. Solar noon, when the sun is highest, is not the same as noon on the clock.

For a Northern Hemisphere winter-noon check at latitude 50° N, use a solstice declination of −23.44° (NASA’s Earth obliquity). The noon altitude from geometry is:

α = 90° − |latitude − declination| = 90° − |50° − (−23.44°)| = 16.56°.

In the Southern Hemisphere the same check applies on the June solstice. For the project’s actual dates and times, use a solar-position calculation. Objects on the horizon can reduce sunlight even more.

Step 3: Calculate the row’s height and footprint

For the simplified case, let β be the collector tilt above horizontal:

H = W × sin(β)

B = W × cos(β)

Consider a hypothetical row with W = 1.134 m and β = 30°.

• H = 1.134 × sin(30°) = 0.567 m.
• B = 1.134 × cos(30°) ≈ 0.982 m.

At β = 15° with the same W, H is approximately 0.294 m and B approximately 1.095 m. Height follows the sine of the tilt angle, so it does not grow in a straight line with tilt. Turning a module from landscape to portrait changes W by its actual dimensions. It does not always double it.

Check the mounting plan against the module maker’s manual. For example, Canadian Solar’s installation manual, revision 3.1 lists mounting and load conditions for each model, covering clamps, supports and orientation.

Step 4: Calculate a shadow check for the stated sun position

Assume level ground and identical parallel rows with lower edges at the same height. Assume sunlight comes from the front, at right angles to the row’s long side. Let α be the solar altitude, a positive angle.

The horizontal shadow reach behind the upper-edge projection is:

G = H ÷ tan(α)

The smallest pitch at which the sun’s ray just reaches the next row’s lower edge is:

P = W × cos(β) + W × sin(β) ÷ tan(α)

Use degrees throughout. For H = 0.567 m and α = 16.56°:

G = 0.567 ÷ tan(16.56°) ≈ 1.907 m; P ≈ 0.982 + 1.907 = 2.889 m.

At this pitch the sun’s ray just reaches the next row’s lower edge at solar noon. Add a margin for measurement and installation errors before you issue drawings.

Reproducible comparison at two tilts

All values below use the same hypothetical W = 1.134 m, α = 16.56°, level ground and aligned sunlight. The values are rounded after calculation. No buffer is included.

A lower tilt shortens the gap by 0.92 m (1.907 − 0.987). It adds 0.113 m of footprint. So pitch falls from 2.889 m to 2.082 m. These values are geometry only. Compare yield at each tilt before you choose one.

What changes away from the aligned case?

The cross-row sun angle that matters is the profile angle. It takes the sun’s direction relative to the rows into account. PVsyst’s profile-angle definition states that PVsyst uses it for all mutual-shading calculations. For a slanted morning or afternoon sun, solar altitude alone gives the wrong cross-row shadow reach. The table above shows how G changes with γ and α.

Sloping ground, different mounting elevations, short rows, staggered tables and nearby objects also change the geometry. Model these directly. Do not just add a flat 10% allowance.

PVsyst’s sheds documentation describes the simplified two-dimensional unlimited-sheds approach. If the rows are long and continuous enough, you can ignore edge effects. Check whether that simplification fits your array.

Step 5: Choose a shading objective and check the relevant period

A winter-noon check looks at one instant. At 50° N the cross-row gap at 09:00 solar time is about twice the noon value (3.80 m against 1.91 m in the table above). So a noon-based pitch does not give a shade-free 9 AM to 3 PM window. Sun near the horizon casts very long shadows. So “worst case” needs a defined time and goal.

Decide what the design aims to do. It might limit shade during a chosen time window, get the most annual energy from an area, or give the best project value. Then test each candidate pitch over the right period. Use the same weather and equipment assumptions for all of them.

Compare total annual AC energy and specific yield separately. A kWp is one kilowatt of panel rating. A denser array can make less energy per installed kWp and still make more total energy. The simulation shows which. Neither wider nor tighter spacing is always better.

Access, maintenance, drainage, mounting and local rules are separate limits. A shade goal does not override them. Where tolerances matter, write down their basis and test their effect. Do not apply a flat safety percentage.

Step 6: Calculate GCR using the model’s definition

GCR means ground coverage ratio. It compares the panel area with the ground area each row uses. For identical continuous rows with no inactive bands or gaps inside the collector, it simplifies to:

GCR = W ÷ P.

For the 30° hypothetical example, GCR = 1.134 ÷ 2.889 ≈ 0.393.

The horizontal projected coverage is different. B ÷ P = 0.982 ÷ 2.889 ≈ 0.340. Name the area definition before you call the remainder empty ground.

PVsyst’s GCR documentation separates the module, shading, backtracking and bifacial definitions. Backtracking is when trackers turn back from the sun early and late in the day so rows do not shade each other. Bifacial panels collect light on both sides. PVsyst also explains that walkways and other areas may not be included. When you compare reports, record the field and the definition used. Equal GCR values from different tools can describe different geometry.

For bifacial modelling, review row geometry together with mounting height, ground reflectance, structure shading and the model assumptions. No fixed bifacial gain or GCR offset applies to all projects. Rerun the calculation each time the pitch changes.

Step 7: Compare alternatives and release a consistent drawing

A practical comparison changes the pitch and keeps tilt, equipment and weather the same. Then test other tilts separately. Record installed capacity, total production, specific yield, shade losses and cost assumptions. Count the whole number of rows that actually fit. Area-based estimates can overstate capacity at plot edges. The solar land area calculator guide shows how GCR feeds a site-level area estimate.

The SAM shading documentation defines its row spacing estimate as the length of the row side divided by GCR, measured between row bottoms. It also describes the self-shading geometry and its limits. Check that the model inputs match the drawing. That includes the difference between physical rows and electrical strings, which are groups of panels wired in series. Electrical shading losses depend on the wiring as well as the shaded area.

Use one revision number across the dimensioned plan, equipment list, electrical schedule and energy report. Record row pitch, panel width, tilt, azimuth, elevation assumptions and any open issues. Then the installer can rebuild the design.

Use the panel layout design guide for the wider roof-to-electrical handoff. When evaluating solar design software, ask it to reproduce a known geometry case, such as the worked example above. Ask it to compare several pitches on your own project inputs. Ask which terrain and shading methods it supports.

Gap Between Two Solar Panels: Module Gap vs Row Gap

The gap between two panels in the same row is a different number from the row gap. The module maker’s mounting manual sets it, not the sun. Canadian Solar’s manual (revision 3.1, November 2025, page 7) states that you need a minimum clearance of 6.5 mm (0.25 in) between modules. This lets the frames and modules expand when they heat up. On page 10, after its wiring layouts, it says the distance between two adjacent module frames should be within 50 mm on the side with mounting clamps and within 25 mm on the side without. This is to meet the system cable scheme. Other manufacturers publish their own values. Read the manual for the module you specify.

Add the module gap to W when a row has several modules up its slope, because that gap is part of the height that casts the shadow. Rows built for crops or machinery follow different spacing rules. See agrivoltaics spacing.

Troubleshooting spacing disagreements

For supporting terminology, see the solar angles guide and specific yield definition. To check a pitch on your own project, book a SurgePV demo or read how shading analysis works.

Frequently Asked Questions

What is the formula for inter-row spacing of solar panels?

For equal-height parallel rows on level ground with sunlight square-on to the rows, height H = W × sin(tilt), footprint B = W × cos(tilt), clear gap G = H ÷ tan(solar altitude), and pitch P = B + G. For sun at an angle to the row normal, multiply G by cos of that azimuth difference. Sloping ground and rows at different heights need a full geometry model.

What is a good ground coverage ratio for solar panels?

No single GCR suits every project. State the area definition. Then compare the pitches that fit on total energy, specific yield, cost and required access. In the 30° example above, GCR = W ÷ P = 0.393. Tools define GCR differently for shading, backtracking and bifacial calculations.

How do you calculate shadow length from solar panels?

Take the level-ground example with the sun square-on to the rows. The shadow reach behind the upper edge is the row’s height rise divided by the tangent of solar altitude. At 50° N on the winter solstice, noon altitude is about 16.56°, so a 0.567 m rise casts a 1.91 m shadow. For south-facing rows at that latitude, the cross-row reach grows to about 2.38 m two hours either side of noon. It grows to 3.80 m three hours either side.

Does inter-row spacing affect solar panel output?

Yes. Row geometry changes how much the rows shade each other. That changes total energy and specific yield. The size of the effect depends on sun positions, equipment wiring and model assumptions. So compare candidate pitches in a yield simulation. A winter-noon check covers one instant, not the 9 AM to 3 PM window.

What is the difference between row pitch and clear gap?

Pitch is the distance between matching edges of two consecutive rows, and clear gap is pitch minus the row’s horizontal footprint. In the 30° example the pitch is 2.889 m and the clear gap is 1.907 m. The difference is the footprint, 0.982 m. Mixing the two up is a common reason spacing values disagree between drawings.

How much gap do you need between two solar panels in a row?

Check the module maker’s installation manual, because the gap between modules in a row is not a shading number. Canadian Solar’s manual (revision 3.1) states a minimum clearance of 6.5 mm between modules for thermal expansion. It also gives frame-to-frame limits of 50 mm on the clamp side and 25 mm on the side without clamps.

Why is a winter-noon spacing check not enough?

It covers one instant, and noon is not the worst hour. At 50° N on the winter solstice the cross-row gap is 1.91 m at noon but 3.80 m at 09:00 or 15:00 for the example row. Pick a shading goal and time window first, then compare annual energy at each candidate pitch.