☀️ Solar Panel Calculator
Estimate how many solar panels you need, total system size in kW, estimated annual output, and payback period based on your electricity bill and local conditions.
Frequently Asked Questions
A typical US home uses about 900–1000 kWh per month. With 400W panels and 5 peak sun hours per day at 80% efficiency, you would need approximately 18–22 panels (7–9 kW system) to cover 100% of usage. Homes in sunnier climates may need fewer panels.
Peak sun hours are the number of hours per day when solar irradiance averages 1000 W/m². This is not the same as daylight hours. The US average is about 4–5 hours. Southwest US gets 5.5–7 hours; Northeast US gets 3.5–4.5 hours. Look up your location's peak sun hours for accurate results.
System efficiency accounts for losses from inverter conversion (typically 5–10%), wiring resistance, temperature effects, shading, and soiling. Most grid-tied residential systems operate at 75–85% efficiency. 80% is a reasonable conservative default.
The US federal Investment Tax Credit (ITC) allows homeowners to deduct 30% of the cost of a solar system from federal taxes (as of 2024–2032). Many states offer additional incentives. Enter your estimated incentive amount in the calculator to see adjusted payback period.
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