Solar Panel Calculator

Size your solar system — panels, cost, and payback in seconds

Monthly Electricity Usage (kWh)

Check your electric bill — US average is ~900 kWh/month

Average Peak Sun Hours Per Day: 4.5h

3h (Seattle)5h (Denver)7h (Phoenix)

Panel Wattage: 400W

Panel Efficiency Factor: 80%

70% (aged/ shaded)80% (typical)95% (new/ optimal)

Installed Cost Per Watt: $2.85

$2.00 (budget)$2.85 (US avg)$4.50 (premium)

Your Solar System Estimate

System Size

9.0 kW

Panels Needed

28 panels

Annual Production

11332 kWh

Est. Total Cost

$25,536

Estimated Payback Period

15.8 years(at $0.15/kWh, saving $1,620/year)

Estimates based on NREL derate factor of 0.77. Actual production depends on orientation, shading, temperature, and local weather. Always get 3+ installer quotes before committing.