Power for a weekend trip: estimate what your devices need before buying

By the Overlanding.info team · Updated 21 October 2026 · Sources checked 21 October 2026

The short answer

Work out each device's watt-hours, add them up, then allow for conversion losses. Watts come from the device's label or maker page, multiplied by the hours you'll use it. Use the figures on your own devices, not the example in this guide.

Watts, watt-hours and amp-hours

Watts measure how fast a device uses power at any moment. Watt-hours measure the total energy used over time, and that is what decides how long a battery lasts. EcoFlow's watt-hours guide puts it simply: Wh = watts x hours.

Many leisure batteries are rated in amp-hours instead. To convert, multiply by the battery's voltage. EcoFlow's amp-hour guide gives Wh = Ah x V, so a 100 Ah battery at 12 V is 1,200 Wh. Always use the voltage: the same 20 Ah rating is 74 Wh at 3.7 V, not 240 Wh at 12 V.

If a label gives only volts and amps, EcoFlow's washing machine guide says to multiply them for a rough watts figure.

Step by step: the method

1. List the devices you'll run between charges, such as a phone, lights, a laptop and a cool box. The overlanding kit list can help you check what else you're taking, and the kit list builder helps you build your own list.
2. Find each device's rated watts, as set out in the next section.
3. Estimate the hours each device runs per day or per trip. Multiply watts by hours to get watt-hours for each device.
4. Add the watt-hours for every device to get your daily total.
5. Allow for conversion losses, as set out below.
6. Compare the total with your battery or station's capacity in Wh, and check its output limit.

If you're planning how to recharge between stops, power on the road covers the gap between charges. If you'll charge from the vehicle while driving, charging while driving sets out the vehicle-specific socket checks to make.

Find each device's rated watts

Start with the label on the device or its adapter, or the maker's product page. EcoFlow's washing machine guide makes the same point for appliances: where the label lists watts, use that figure. For motor-driven kit, check whether the maker gives running and starting watts, and note both.

Allow for conversion losses

Most power stations run AC devices through an inverter, and the inverter uses some of the energy. EcoFlow's watt-hours guide says modern inverters generally run at 85% to 95% efficiency, so a 100 W load for one hour can take 110 to 115 Wh from the battery. Bluetti's buying guide builds this into its runtime formula: battery Wh x 0.85, divided by device watts.

Dividing your daily total by 0.85 is the cautious choice. Where your station's maker gives its own efficiency figure, use that instead.

Worked example

Example devices, figures made up to show the method. Use the figures on your own devices.

The daily total of 750 Wh divided by 0.85 gives about 880 Wh to be drawn from the battery. Using the top of EcoFlow's range, 0.95, gives about 790 Wh, so 0.85 is the safer figure here. Your own totals will differ, so run the sums on your own devices.

Check the output limit and starting surge

Watt-hours and watts are separate limits. Bluetti's guide says a station can run several appliances as long as their total draw stays under its output rating, even when the battery holds enough energy. Fridges and motorised tools need an extra jolt to start, and Bluetti says its runtime formula does not account for that. Plug a high-surge device in on its own first, so the station does not shut off.

If you're also planning your first roof tent trip, the first roof tent weekend guide is the companion read.

FAQs

Next: compare supply with your daily figure

Once you have a daily watt-hour total, read power on the road to compare how you'll recharge against it.

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