Solar Panel Calculator
Estimate how many solar panels fit your roof, total system capacity in kW, and expected annual energy production in kWh.
Usable roof area for solar panels
Average peak sun hours in your area
Wattage rating per panel
Typical: 18-22%
Frequently Asked Questions
How many solar panels do I need for my home?
The average US home uses about 10,500 kWh per year, which typically requires 20-25 solar panels rated at 400W each. The exact number depends on your roof size, sun exposure, and energy consumption.
What is a good panel efficiency percentage?
Modern residential solar panels typically have an efficiency between 18-22%. Premium panels can reach up to 24%. Higher efficiency means more power from less roof space.
How many peak sun hours does my area get?
Peak sun hours vary by location. The US Southwest averages 6-7 hours, the Southeast 4-5 hours, the Northeast 3-4 hours, and the Pacific Northwest 3-4 hours. Check NREL's solar resource maps for your specific location.