How long will a power station run a 12V fridge?

Short answer: a lot longer than the running wattage suggests, because a 12V fridge spends much of the day switched off. A Dometic CFX3 45 on a Bluetti AC180 works out to about 84.0 hours from the car port, on a hot day by Dometic’s test figures. A small station like the EcoFlow RIVER 3 Plus still gets that fridge through 21.0 hours, which is about a day.

Why it’s not the wattage on the box

A compressor fridge cycles. It runs hard until the inside is cold, shuts off, and starts again when the temperature creeps back up. So the figure that decides runtime is how much energy it uses over a whole day, not what it pulls while the compressor is going. Dometic publishes an average current for each CFX3 at its test conditions, and we turn that into watt-hours per day. The tables spread that evenly over the day to get an average load, then divide the station’s capacity, after an efficiency factor, by that load.

The running draw still matters for one thing: whether the port or inverter can carry it. We check that against Dometic’s rated input for each model.

Everything here is calculated, not measured. We haven’t run these fridges on these stations ourselves, and the efficiency factors are our assumptions, listed under each table.

Use the 12V port

The 12V DC rows come out longer than the AC rows for two reasons. The station doesn’t have to keep its inverter running all day, and nothing has to turn AC back into DC at the fridge end. Our AC figures only count the station’s inverter loss, not that second conversion, so if anything the AC rows flatter the AC path.

The exception is the Dometic CFX3 95DZ. Its rated DC input current is above the car port rating on every station here, which is 10 A, so its DC rows say it won’t run. That rated figure is the most the fridge draws, not what it pulls all day. But a port that cuts out when the compressor starts isn’t much use, and we haven’t tested whether any of these ports actually would. For the 95DZ we’d plan on the AC outlet, or a 12V output rated for more current if your station has one. The car ports in our data don’t.

Why your hours will differ

Dometic’s figures come from a hot room with the fridge held at fridge temperature (the exact conditions are in the Mode column). That’s a fair stand-in for a summer campsite. Cooler weather means less running and more hours. Some things push the other way:

• opening the lid a lot, especially in the sun
• loading it with warm food or drinks, which the fridge then has to cool down
• setting it colder, or running a freezer zone
• packing it so tightly against a wall or other gear that the compressor can’t vent its heat

An older station also holds less than its rated capacity. If the table says you’ll just make it to the next charge, assume you won’t.

Runtime by fridge

We picked five stations from small to very large. The runtime calculator has the rest of the stations in our data.

Dometic CFX3 25

The smallest CFX3 and the lightest on the battery. Even the small station gets close to a full day.

Dometic CFX3 35

Only a little hungrier than the 25, so the hours barely move.

Dometic CFX3 45

The middle of the single-zone range. By these figures, a station around a kilowatt-hour covers a weekend without charging.

Dometic CFX3 55IM

The 55IM has a built-in ice maker, and Dometic gives a second figure with it switched on. It costs some hours, but not many.

Dometic CFX3 75DZ

A dual-zone fridge, so there are two rows per station: both zones as fridges, and the small zone as a freezer. The freezer setting cuts the runtime by about half. If you only need a freezer some of the time, that’s the setting to turn off when you’re trying to make a battery last.

Dometic CFX3 95DZ

The biggest CFX3, and the one that won’t run from the car port in our checks (see above). The AC rows are the ones to look at, and they’re the optimistic side of the estimate.

Going longer than one charge

For a trip longer than one charge, what matters is whether you can put back what the fridge uses each day, from the car while driving or from a solar panel. Our solar recharge calculator estimates how long a refill takes, and 12V fridge daily power consumption lists what each of these fridges uses in a day.