How long can a portable battery run a household fridge?

Measure how long a nominal 1,000 Wh portable power station can keep a modern inverter-compressor household refrigerator running at its outlet. Capture the fridge's real cycling profile rather than its nameplate draw. Then translate the result into a planning number owners can trust during an outage.

We pre-chilled the fridge to its normal 4 °C interior temperature and charged the station to 100%. We plugged the fridge into the logged AC outlet with the station's low-load auto-sleep disabled. That feature shuts the output off when draw stays low, and a cycling compressor triggers it during its idle minutes.

The logger recorded instantaneous watts every second and the cycle detector stamped every compressor start. We ran the fridge until the station reached its own low-battery cutoff. We integrated the watt log to get average draw and total delivered energy. Then we counted compressor on-time against total elapsed time to derive the duty cycle.

A refrigerator is not a 108 W heater that runs forever. It is a 108 W machine that runs about a third of the time once the cabinet is cold. The insulation holds the temperature, and the compressor only needs to replace what leaks in. Dividing battery capacity by running watts answers a question nobody is asking — how long a compressor would run if it never satisfied its thermostat.

The measured duty cycle of 31% turned a headline 108 W load into a real 34 W average. That is the number the battery actually sees, and it is the number every runtime estimate should be built from.

Twenty-three hours means one full day-plus of refrigeration from a 1,000 Wh station. That carries perishables through most short outages without ever opening the freezer conversation. Public-health guidance already says a closed fridge keeps food safe for about four hours without power. A station that holds it at temperature for a full day moves that window into a different risk category.

The station's own low-battery cutoff ended our runs with the fridge still cold. A practical rule: the final two hours are margin, not runtime. Recharging the station from a 200 W solar array during daylight extends the arrangement indefinitely at mild duty cycles. That arithmetic is covered in our solar input test.

The method generalises even though the numbers will not. Take your fridge's measured average over a cycle rather than its sticker watts. Divide it into about 80% of the station's nameplate capacity — the usable fraction we measured at light loads in the companion test. The estimate should land within a few hours of a real run.

An older fixed-speed fridge in a hot kitchen might average 60–80 W and halve that runtime. A garage chest freezer cycling at 20% might stretch a smaller station further than a fridge at the same capacity. Hard-start surge is the other spec worth checking. Our inverter fridge peaked under 300 W, but a decades-old compressor can demand five times its running watts for a second — and that is what trips undersized inverters.