Enter your usable roof area and see the maximum system size, panel count and production your roof can actually support.
This is your roof's ceiling, not necessarily what you need — check the Solar Panel Calculator to see what your usage actually requires.
Further reading: How Many Solar Panels Do You Actually Need? A Complete 2026 Guide
1.9 m² per panel reflects a standard 450W residential panel (roughly 1.9m × 1.0m) plus a small margin for mounting rail clearance. Usable area is almost always less than total roof area — fire code setbacks along ridges and edges, plus space lost to vents, chimneys and skylights, typically take 15-30% off the top.
That's normal and fine — most homes don't need to cover the whole roof. Compare this ceiling against the Solar Panel Calculator's usage-based recommendation to see how much headroom you have for a future EV or heat pump.
You have options: a higher-wattage panel (more kW in the same area), a ground-mount array if you have land — see the Off-Grid Calculator for sizing principles — or accepting a lower offset percentage paired with efficiency upgrades.