Power — motorhome tools Power Tools

Daily power consumption calculator

For UK and EU motorhome and campervan trips. Tick what you use, set watts and hours, and see watt-hours per day plus amp-hours at 12 V and 24 V.

Planning estimate · daily Wh and Ah at 12 V and 24 V

Total energy

0Wh / day

At 12 V

0Ah / day

Wh ÷ 12

At 24 V

0Ah / day

Wh ÷ 24

Breakdown by appliance

    Start from a preset

    Saved on this device

    Appliances

    Edit watts, hours per day, and quantity. Untick anything you will not use.

    How to use

    1. Choose a preset if you want a head start, or keep the defaults.
    2. Tick only the appliances you will run, then set watts from the label or manual.
    3. Enter hours of use per day. For a fridge, hours means compressor run-time, not time switched on.
    4. Totals update as you type. Refresh the page: your numbers stay on this device.

    FAQ

    How many amp hours does a campervan use per day?

    There is no single number. A light weekend for two people is often a few tens of Ah at 12 V. A family week with a kettle or induction hob through an inverter can be a few hundred Ah. Use the totals above for your own kit rather than a rule of thumb.

    Wh vs Ah — what’s the difference?

    Watt-hours (Wh) measure energy. Amp-hours (Ah) are that energy divided by battery voltage: Ah = Wh ÷ volts. Wh is useful for comparing loads. Ah is useful once you know whether the battery is 12 V or 24 V.

    12V or 24V — which Ah number do I use?

    Use the Ah figure that matches your leisure-battery voltage. The same daily Wh is half the Ah on 24 V (Wh ÷ 24) compared with 12 V (Wh ÷ 12). Do not mix the two.

    Why is the fridge often the biggest load?

    A compressor fridge may only draw 40–60 W, but it cycles for many hours. That daily watt-hour total often beats lights, phones and a laptop combined. Hours here means compressor run-time, not time the fridge is switched on.

    Is this calculator accurate enough for battery sizing?

    It is a planning estimate, not a design or a guarantee. Weather, fridge duty cycle, cable losses, battery age and inverter efficiency all change the real figure. Use it to compare setups and leave a margin; get a qualified installer for safety-critical work.

    Should I add inverter loss?

    Tick it if you run 230 V kit (kettle, hob, laptop brick) through an inverter. The extra 12% is a simple allowance, not a measured efficiency. 12 V loads such as the fridge do not need it on their own.

    Next: size a battery, solar, inverter, then cable

    Your daily watt-hours stay on this device. Open Battery for a 12 V Ah size to buy, Solar for panel watts, Inverter for continuous watts, and Wire & fuse for mm² and amps.

    Open Battery Open Solar Open Inverter Open Wire & fuse

    Guides

    Short reads on Motorhome Tools. They do not change the numbers on this calculator.