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What will a power station run, and for how long?

List what you want to power, choose a power station or type in its capacity, and see an estimated runtime. The math is shown, so you can check it.

Runtime calculator

Pick a quick-pick modelCapacity (Wh)Rated AC output (W, optional)Efficiency (%)Hours you want it to run (optional)

Device	Watts	How many	% of time running

Example rows are round numbers to show the method, not measurements. Use the watts on your own device labels. This runs in your browser; nothing is sent anywhere.

How the estimate works

Runtime (hours) = capacity (Wh) × efficiency ÷ average load (W)

Capacity is the power station's rated watt-hours from the brand's listing.
Efficiency is an assumption. We use 85% by default to allow for losses when the battery's DC power is turned into 120 V AC by the inverter, plus other conversion losses. It is not a measured figure for any model. Real results vary with the model, the load and the temperature, so change it if the maker publishes a figure.
Average load adds up each device's watts × how many × the share of time it actually runs. A refrigerator cycles on and off. Virginia Cooperative Extension suggests dividing the time a refrigerator is plugged in by three to estimate the time it runs at full wattage, which is why the example fridge row uses 33%.
Watts are on the device's label or nameplate. The extension guide notes this is the maximum the device draws, and that if only amps are listed you can multiply amps by volts (120 V for most US plug-in devices).

Check the output rating too

Capacity sets how long it runs. The rated AC output (W) sets how much it can run at the same time. If your devices together need more watts than the station's rated output, it will not run them all at once, however big the battery is. Motors and compressors can need extra power for a moment when they start, so check the brand's surge rating for those.

Worked example

A 1,024 Wh power station running a load that averages 100 W: 1,024 × 0.85 ÷ 100 = about 8.7 hours.

Frequently asked questions

How long will a 1,000 Wh power station run a fridge?

It depends on the fridge's wattage and how often its compressor runs. Using the formula above, a fridge that averages 50 W (150 W running about a third of the time) would run for about 1,000 × 0.85 ÷ 50 = 17 hours. Use your fridge's label and the calculator for your own estimate.

Why not use the full rated capacity?

Some energy is lost turning the battery's DC power into AC and in other conversions. We assume 85% efficiency by default. That is an assumption, not a measurement, and you can change it.

Is this a test of these power stations?

No. We have not tested these products. The calculator uses brand-listed capacity and output figures and a stated efficiency assumption.

Next: compare current prices in the Black Friday quick picks and power station deals, or size a bigger system with the home backup calculator.

Estimates only. Specs and prices for listed models are from each brand's product page, checked Nov 3, 2026.

Need more than about 3 kWh between recharges, or 240 V? That is the home backup tier: see home backup power and how much battery do I need?