kWh
%
W each.
Output
Output will appear here
Click in the output to select all text
Solar Panel Calculator
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This Solar Panel Calculator works out the solar system size (in kW) and the number of panels you'd need to cover your daily energy usage, based on your location's peak sun hours and typical system losses (wiring, inverter conversion, panel soiling, and temperature effects). Enter your average daily energy usage in kWh, your area's peak sun hours (available from solar irradiance maps for your region), and your chosen panel wattage, and get an instant estimate. It's a starting point for sizing a home solar installation before getting a professional quote. Everything runs locally in your browser. Scroll down to enter your numbers.
Features
- Calculates required system size in kW
- Estimates the number of panels needed for a given wattage
- Accounts for typical system losses
- Instant recalculation as you adjust inputs
Why use this solar panel calculator?
- Quick first-pass sizing before contacting an installer
- No manual solar math required
- Fully private — nothing uploaded
- Free with unlimited use
Frequently asked questions
What are peak sun hours?
Peak sun hours represent the equivalent hours per day of standard 1000 W/m² sunlight your location receives — not daylight hours; typical values range from 3-6 depending on climate and season, and are available from regional solar irradiance data.
Why include system losses?
Real-world solar systems lose 15-25% of theoretical output to inverter conversion, wiring resistance, panel temperature, dust, and shading — ignoring this would significantly undersize the system.
Where do I find my daily energy usage?
Check your electricity bill's average daily kWh, or divide your monthly usage by roughly 30.
Does this account for seasonal variation?
No, it uses a single peak sun hours figure; for a more conservative design, use your location's lowest-sun-hour month rather than the annual average.
Is this a substitute for a professional solar quote?
No, this is a planning estimate; a professional installer will do a detailed site assessment covering shading, roof orientation, and local permitting requirements.