SunSizer — Roof Layout Estimator

How many panels fit one roof section? Estimates only — racking, vents, and code decide the real layout.

Fit check

Typical 400W panel ≈ 65" × 39". Check your panel spec sheet.

3 ft is common under IRC fire-access rules; your jurisdiction may differ.

Before you count on this: vents, chimneys, skylights, dormers, and racking rails eat real roof. Fire setbacks vary by jurisdiction. An installer does a shade and structural survey — this page just tells you whether the section is in the right ballpark.

Frequently asked

Do panels have to face south?

South-facing is best in the Northern Hemisphere, but east/west roofs still produce well (roughly 80–85% of south). North-facing sections are usually skipped. Azimuth matters less than avoiding shade.

How much does a panel weigh?

A typical residential panel weighs 40–50 lbs, spread over its mounting points. Most modern roofs handle this fine, but older roofs may need a structural check — your installer confirms this.

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