Daily Power Needs Calculator

List what you run, how long for, and get the daily energy your solar system has to supply, plus your peak load.

This gives a daily energy and peak load estimate for planning only. The example rows are a small workshop, so edit or remove them. Everything is worked out in your browser. Nothing is saved or sent anywhere.

1. What you run

Enter each item's watts (from the rating plate or manual), the hours it runs on a normal day, and how many you have. Power tools run in short bursts: a drop saw cutting for 15 minutes a day is 0.25 hours. Tick On together for items that could all be running at the same moment. Fridges and freezers go in step 2, not here.

2. Fridges, freezers and margin

Fridges and freezers cycle on and off, so don't use plate watts × 24 hours. Use the energy rating label: the calculator divides the kWh per year by 365. Enter 0 if you have none.

Add the labels together if you have more than one.
Used only for the peak load, as the compressor can be running at any time.
Covers inverter, battery charging and cable losses. About 20% is a common starting point.

3. Results

How it was worked out

    Before you rely on it

    • Rating plates show the maximum. Many items use less most of the time. A plug-in energy meter for a day or two gives a truer figure.
    • If your inverter stays on all day, its idle (standby) draw adds up. Add it as an item: its standby watts for 24 hours.
    • Daily energy sizes the battery and panels. The peak load sizes the inverter, and motors also draw a start-up surge. The Inverter Size Calculator allows for it.
    • This is a planning estimate only, not a system design, wiring specification or safety assessment. Real results depend on your location, weather, shading and the gear you choose. Check the manuals and specifications for your panels, battery, inverter and charge controller.
    • Safety: in Australia, any work on 240V AC wiring, including connecting an inverter, battery or solar system to a home's switchboard or fixed wiring, must be done by a licensed electrician. Grid-connected systems also need approval from your electricity network.

    Next steps

    Read the full method in How to Calculate Your Home or Workshop Power Needs. Then take your numbers to the next calculators. The buttons below carry your results across.

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