12V Fridge Runtime Calculator
Work out how long your 12V camping or caravan fridge will run on a 100Ah, 200Ah or 300Ah battery — or a portable power station — using an estimated average draw or your own measured figure.
Compressor fridges cycle on and off — this should be the average draw over a full day, not the peak/running wattage. Typical camping fridges average 35–65W depending on size, ambient temperature and how often the lid is opened.
Lights, phone charging, water pump, etc. Set to 0 if the fridge has a dedicated battery.
Estimated Fridge Runtime
Usable battery capacity
1.14 kWh
Fridge estimated use
1,200 Wh/day
Fridge alone — estimated runtime
22.8 hours
With other loads — estimated runtime
21.0 hours
total 1,300 Wh/day
We do not assume your fridge runs continuously at its rated compressor wattage — the "estimate" mode uses an average draw over 24 hours, since compressors cycle on and off. For the most accurate result, use a measured daily Wh figure from a battery monitor if you have one.
Why fridge wattage estimates vary so much
A 12V compressor fridge doesn't draw its rated wattage continuously — the compressor cycles on and off to maintain temperature. Actual average consumption depends on ambient temperature, fridge size and insulation quality, how full it is, and how often the lid is opened. That's why this calculator treats fridge wattage as an average 24-hour draw, and lets you enter a measured Wh/day figure instead if you have one from a battery monitor or shunt.
Worked example
A 100Ah 12V LiFePO4 battery has a rated capacity of 100 × 12 = 1,200Wh, with roughly 95% usable ≈ 1,140Wh. A fridge averaging 45W over 24 hours uses 45 × 24 = 1,080Wh/day. Runtime ≈ (1,140 ÷ 1,080) × 24 ≈ 25.3 hours on the fridge alone.
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Frequently Asked Questions
How long will a 100Ah battery run a fridge?+
For a typical camping fridge averaging 40–55W over 24 hours, a 100Ah 12V LiFePO4 battery (about 1,140Wh usable) will generally last a little over a day on the fridge alone. Enter your fridge's actual estimated or measured consumption above for a figure specific to your setup.
Should I use the rated compressor wattage or an average?+
Use an average. Rated/running wattage only applies while the compressor is actively running, which is typically well under half the time in normal use — using it as a continuous figure will significantly overestimate consumption.
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