SOLAR
How Many Solar Panels Do You Need?
Estimate how many solar panels a home needs to offset its bill — with the free panel count calculator.
The number of panels you need comes from three numbers: your annual kWh usage, your area's peak sun hours, and each panel's wattage. Most homes land between 16 and 23 panels.
THE SHORT ANSWER
The short answer
A typical U.S. home using 900 kWh/month needs about 21 panels of 400 W — an 8.2 kW system. Homes range from 10 panels (low usage, sunny) to 30+ (high usage, cloudy).
The formula
Annual usage ÷ (sun hours × 365 × loss factor) = system kW. Then system kW × 1,000 ÷ panel wattage = panel count. A 20% loss factor covers inverter, wiring and temperature losses.
- Average home: 16–23 panels
- System size: usually 6–9 kW
- 400 W panels are the current standard
- Loss factor: 20% is a safe default
What changes the number
High electricity use (EVs, pools, electric heat) needs more panels. Sun-rich states need fewer for the same bill. Roof orientation and shading can add or subtract a few panels from the ideal count.
Try the panel count calculator
Enter your monthly usage, panel wattage, sun hours and losses to see your recommended panel count and system size.