What is the Solar Panel Calculator?
Estimate the number of solar panels and battery size needed for a daily load.
Enter daily energy use, peak sun hours per day, panel wattage, system efficiency and battery backup wanted and the Solar Panel Calculator returns panels needed, array size and battery capacity at 12 V. Results update as you type, and nothing you enter leaves your device.
How it is calculated
How to use it
- Enter daily energy use in kWh.
- Enter peak sun hours per day in hours.
- Enter panel wattage in W.
- Enter system efficiency in %.
- Enter battery backup wanted in days.
- Read panels needed in the results panel. It updates as you type.
- Change any value to compare scenarios, or use Share to send the result as a link.
Worked example
Common questions
What formula does the Solar Panel Calculator use?
It uses: Array (kW) = daily energy ÷ (sun hours × efficiency); Battery (Ah) = daily energy × days ÷ voltage ÷ depth of discharge (50%).
What do I need to use the Solar Panel Calculator?
You need daily energy use, peak sun hours per day, panel wattage, system efficiency and battery backup wanted. Sensible starting values are filled in so you can see how it works straight away.
Is the Solar Panel Calculator free, and is my data stored?
It is free with no sign-up. The calculation runs in your browser, so the values you enter are not sent to or stored on our server.