Free OnlineCalculators & Converters
Solar Panel Calculator
Calculate how many solar panels you need based on monthly electricity usage. Get system size, annual output, CO2 offset, and estimated cost.
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Key Features — Solar Panel Calculator
Panel count from monthly kWh
System size in kW
Annual energy production
CO2 offset per year
Estimated installation cost
Why Use This Tool — Solar Panel Calculator
Free Online Solar panel calculatorHow many solar panels do i need — for EveryoneFast & Easy Solar system size calculatorSolar energy calculator — 100% FreeFree Online Solar cost calculator
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Get instant results with zero wait time. No server delays, no loading screens.
Works Everywhere
Use on any device — desktop, tablet, or phone. No downloads or plugins needed.
Frequently Asked Questions — Solar Panel Calculator
How many solar panels do I need?
Daily kWh / (peak sun hours × efficiency) = system kW. Divide by panel kW for panel count. 900 kWh/month home: ~18–19 panels at 400W.
What are peak sun hours?
Daily solar energy equivalent to full sunlight (1,000 W/m²). US average is 4–6 hrs. Phoenix: 7.5; Seattle: 3.5.
What does a solar system cost?
$2.50–$3.50/watt installed before the 30% federal tax credit in 2025.