Solar Panel Calculator
Estimates system size, panel count, and cost based on energy consumption and geographic location
Average monthly electricity bill
Cost per kilowatt-hour from your utility
Peak sun hours in your location
Wattage rating of each solar panel
Enter bill and rate to estimate usage
Recommended solar system size
Total panels needed for your system
Projected yearly savings on electricity
Approximate roof space needed at 18 sq ft per panel
Frequently Asked Questions
How many solar panels do I need for my home?
Divide your annual electricity usage in kWh by the production per panel. A 400W panel in an area with 5 sun-hours per day produces about 500-600 kWh per year after losses. A home using 10,000 kWh per year would need roughly 17-20 panels.
What are peak sun hours?
Peak sun hours measure the equivalent number of hours per day when solar irradiance averages 1,000 watts per square meter. An area with 5 peak sun hours does not mean 5 hours of sunshine; it means total solar energy equals 5 hours at full intensity. The US average is 4-6 hours.
How much roof space do solar panels need?
A standard residential solar panel is about 18 square feet. A typical 8 kW system with 20 panels needs roughly 360 square feet of unshaded roof. South-facing roofs in the Northern Hemisphere produce the most energy.
What is system loss in solar calculations?
System losses account for energy lost to wiring, inverter conversion, temperature, shading, and panel degradation. A typical system loss factor is 14%, meaning only 86% of the panels' rated output reaches your electrical panel. Higher quality components reduce losses.
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