System size calculator
$ USDEnter what the site uses in a month and see the array that covers it: size, panel count, yearly output, roof area and installed cost. The panels draw themselves as the number changes.
System size
10.5 kW
19 panels at 550 W each
Produces a year
14,761 kWh
Roof area needed
66 m²
glass plus walkways
Installed cost
$16,720
$1.60 a watt, typical
What this assumes
- Losses of 14% for heat, dirt, wiring, shading and downtime, which is NREL PVWatts' published default. The array keeps 0.86 of its rated output.
- Panel count is always rounded up: you cannot buy part of a panel, so the size shown is the array you would actually build.
- Roof area is the panel glass plus 35% for walkways, edge setbacks and row spacing.
- Cost is a published market range for your region, not a quote. A real number needs the roof.
