Solar & battery
Solar Roof Area Calculator
Roof area a system needs, and how much capacity a given roof will actually take.
Result
Usable roof is always smaller than measured roof. Fire code setbacks along ridges and eaves, access pathways, vents, chimneys, skylights and anything that casts a shadow all take space, and a quarter to a third is a normal loss.
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About this calculator
How much roof per kW?
Roughly 55 to 70 square feet per kW with current panels. Older or lower-efficiency modules need more.
Why do setbacks take so much?
Fire codes in most jurisdictions require clear pathways along ridges and setbacks from edges so firefighters can work on the roof. On a cut-up roof with several planes the loss can exceed a third.
The formula
area = panels x area per panel; panels = system watts / panel watts
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Estimating is the easy part
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