Solar Roof Space Calculator
See how many solar panels fit on your roof and what they would produce.
Your result
Enter your numbers and press the button. Your result appears here.
Measure the sunny, unshaded parts of the roof that face south, east or west. North-facing sections make much less power in the U.S.
How it works
Panels = usable roof area ÷ area of one panel, rounded down.
Example: 600 ft² fits 28 panels, 11.2 kW, making about 15,310 kWh a year.
At a glance
Same settings as the calculator, changing only the roof area.
| Roof area | Panels | Size | kWh a year |
|---|---|---|---|
| 200 ft² | 9 | 3.6 kW | 4,921 |
| 300 ft² | 14 | 5.6 kW | 7,655 |
| 400 ft² | 19 | 7.6 kW | 10,389 |
| 600 ft² | 28 | 11.2 kW | 15,310 |
| 800 ft² | 38 | 15.2 kW | 20,778 |
| 1,000 ft² | 47 | 18.8 kW | 25,700 |
Common questions
How big is a solar panel?
Most 400 W home panels are about 6 × 3.5 ft, or 21 ft².
Which roof directions work?
South-facing is best in the U.S. East and west work well. North-facing roofs make much less.
Sources
- NREL PVWatts v8 (20° tilt, south-facing, 14% losses), state results compiled by TheGreenWatt: https://thegreenwatt.com/average-peak-sun-hours-by-state/