Solar Power

Solar Panel Sizing Calculator

Estimate how many watts of solar panels you need to cover your daily energy use, and how many panels that takes.

This estimates the solar panel size needed to put back what you use each day, for a camping, caravan or 4WD setup. It's a planning figure for an average day in the season you choose. Everything is worked out in your browser. Nothing is saved or sent anywhere.

1. Your daily energy use

Use what you use in a day, not the size of your battery. The Daily Energy Use & Battery Size Calculator or the Fridge Power Draw Calculator can work it out.

Only used to turn Ah into Wh.

2. Your sun and panels

Peak sun hours are the hours of full-strength sun a day adds up to. They're not the same as daylight hours. Use a figure for the season you'll be travelling in.

Winter figures are much lower than summer, especially in southern Australia.
Heat, dust, panel angle, wiring, controller and battery charging losses. 20 to 30% is a common planning figure.

3. Results

How it was worked out

    What this does and doesn't tell you

    • This is a planning estimate for an average day. Cloudy days, shade, a poor panel angle and hot panels all cut output, so many people add extra panel or battery capacity for bad weather.
    • Size for the worst season you'll travel in. A setup that keeps up in summer can fall well short in winter.
    • For peak sun hours in your area, check the Bureau of Meteorology's solar exposure maps. One kilowatt-hour per square metre (kWh/m²) is one peak sun hour, and 3.6 megajoules per square metre (MJ/m²) is the same amount.
    • It doesn't check your solar controller's voltage and current limits, or how your panels should be wired together. Check those against the controller's manual.
    • Work on 240V AC wiring, including inverter outputs and mains inlets, must be done by a licensed electrician. For high-current DC gear such as inverters, DC-DC chargers and battery links, follow the maker's installation manual and have an auto electrician check your work if you're unsure.

    Next steps

    Check how your solar and DC-DC charging compare with your daily use in the Solar & Charging Check. To see how long the panels take to refill a flat battery, use the Battery Charging Time Calculator. Choosing panels? Read Solar Blanket vs Rigid Solar Panel.

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