Solar Roof Area Estimator

Fine Print and Sources

Estimate only. These tools use only the values you enter and simple planning math. Confirm with a pro and get a real quote. A professional solar site assessment and a written installer quote are authoritative for system sizing, production, and final purchase decisions.

This tool counts panels as system watts divided by panel watts, rounded up, then multiplies by about 18 square feet per standard residential panel. The 18 square foot figure is a common rule of thumb, not a value cited to a fetched source. Usable roof area is smaller than total roof area after fire setbacks, vents, shading, and roof orientation, so a professional site survey is authoritative.

• EnergySage solar sizing guide: explains how annual electricity use, peak sun hours, and panel wattage drive system size and panel count.
• NREL PVWatts calculator: a detailed production model that accounts for location, orientation, shading, and system losses.