What is a refrigerator duty cycle?

The duty cycle is the percentage of time the compressor actually runs. A fridge rated at 150W does not draw 150W continuously — the compressor kicks on to cool the interior, then shuts off until the temperature rises above the set point. In a 72F (22C) room, a typical duty cycle is 30-40%. In a hot garage or an RV in summer, it might climb to 50-70%. The average power draw equals the compressor wattage multiplied by the duty cycle fraction.

Can a 12V battery run a full-size household refrigerator?

Yes, but you need an inverter and a substantial battery. A standard household fridge averages 50-100W when you account for duty cycling. A 100Ah 12V LiFePO4 battery could run it for 8-16 hours through a decent inverter. For 24+ hours of runtime, you need a 200Ah or larger battery bank. The compressor startup surge (800-1,200W for 1-2 seconds) requires an inverter with adequate surge capacity.

Is a 12V DC fridge better than an AC fridge on an inverter for battery power?

A 12V DC fridge is significantly more efficient on battery power because it eliminates the inverter conversion loss (10-15%). DC fridges also use compressors designed for variable voltage and lower power draw. The trade-off: 12V fridges are expensive ($300-1,000 as of early 2026 for a quality Dometic or Engel) and smaller than residential fridges. For occasional power outage use, an inverter with your existing AC fridge is more practical. For daily off-grid living, a DC fridge saves meaningful energy.

12V Battery Fridge Runtime Calc

4 min read

A refrigerator does not run at full power all the time. The compressor cycles on and off based on the internal temperature, so the actual average power draw is much lower than the rated wattage. This calculator uses the duty cycle to give you an honest runtime estimate — not the worst-case number from the rating plate alone. For real-world power outage scenarios and setup tips, see our 12V fridge battery guide.

Refrigerator runtime on 12V batteries comparing 100Ah LiFePO4 and lead-acid at 60W draw.

Refrigerator Power Draw by Type

Fridge Type	Compressor Watts	Avg Watts (40% duty)	Runtime on 100Ah 12V
12V camping fridge (40L)	35-45W	14-18W	38-49 hours
12V camping fridge (60L)	45-65W	18-26W	26-38 hours
Dometic/Engel (80L)	55-80W	22-32W	21-31 hours
Mini fridge (residential)	80-120W	32-48W	14-21 hours
Standard fridge (through inverter)	120-200W	48-80W	8.5-14 hours
Full-size fridge/freezer (inverter)	150-300W	60-120W	5.7-11 hours

Runtimes assume 80% DoD and 90% efficiency. DC fridges connected directly to 12V skip the inverter loss, getting about 10% more runtime than AC fridges of the same wattage.

Fridge runtime hours by battery size chart for 50Ah to 200Ah at 60W draw with inverter loss. — A 200Ah battery keeps a 60W fridge running about 17.6 hours with a standard inverter.

Example: Keeping a Fridge Running During a Power Outage

Your power goes out and you need to keep the kitchen fridge running. The fridge nameplate says 150W, but the compressor only runs about 35-40% of the time in normal conditions. Average draw: 150 x 0.38 = 57W.

You have a 200Ah 12V LiFePO4 battery and a 1,000W pure sine wave inverter (90% efficiency). Usable energy: 200 x 12 x 0.80 x 0.90 = 1,728Wh. Accounting for the inverter: 1,728 x 0.90 = 1,555Wh available at the AC outlet.

Runtime: 1,555 / 57 = 27.3 hours. That covers most outages with room to spare.

Tips to extend runtime: pre-cool the fridge to its coldest setting before the power goes out, avoid opening the door, and place frozen water bottles inside as thermal mass. Each of these can extend runtime by 10-20% by reducing the duty cycle.

Worked Examples

Keeping Food Cold During a 24-Hour Power Outage

Context

Your full-size fridge draws 150W when the compressor runs and cycles about 35% of the time (52.5W average). You have a 200Ah lead-acid battery and a modified sine inverter at 50% DoD.

Calculation

Effective load: 150 x 0.35 = 52.5 W average

Usable energy: 200 x 12 x 0.50 x 0.88 = 1,056 Wh

Runtime: 1,056 / 52.5 = 20.1 hours

Interpretation

About 20 hours — close to 24 but not quite. Opening the door increases duty cycle and reduces runtime. Keep the fridge closed as much as possible during an outage.

Takeaway

For a full 24-hour outage, you need either a larger battery or a solar panel to top up during the day. Size the panel with our solar panel output calculator.

RV 12V Fridge on Battery While Driving

Context

Your RV's 12V compressor fridge draws 60W and runs about 40% duty cycle. You have a 100Ah LiFePO4 at 80% DoD running direct DC (no inverter).

Calculation

Average draw: 60 x 0.40 = 24 W

Usable: 100 x 12 x 0.80 x 0.95 = 912 Wh

Runtime: 912 / 24 = 38 hours

Interpretation

38 hours means you can park for a day and a half without plugging in and the fridge stays cold. DC-direct operation saves about 10% compared to running through an inverter.

Takeaway

For a complete RV power audit including all your other loads, use our RV battery runtime calculator.

Frequently Asked Questions

Glossary

Compressor Duty Cycle

The percentage of time the fridge compressor actually runs. A 35% duty cycle means the motor runs about 21 minutes per hour. Higher ambient temperatures, frequent door opening, and warm food all increase the duty cycle.

Average Power Draw

The effective continuous wattage calculated by multiplying the compressor wattage by the duty cycle. A 150W fridge at 35% duty cycle averages 52.5W — this is the number that matters for battery sizing.

Modified vs Pure Sine

Modified sine inverters are cheaper but produce a rough AC waveform that makes fridge compressors run hotter and less efficiently. Pure sine inverters produce clean power identical to utility grid power and are recommended for any motor-driven appliance.

Adding solar to keep your fridge running indefinitely? The <a href="/solar/how-many-batteries-for-solar-system">solar battery count calculator</a> sizes a complete off-grid system.

The key to accurate fridge runtime calculations is the duty cycle — not the nameplate wattage alone. Measure your fridge's actual duty cycle with a kill-a-watt meter for the best estimate, or use 35-40% as a starting point for indoor use and 50-60% for warm environments. If you want your fridge to run indefinitely on solar, the solar panel and battery sizing calculator designs a system that recharges faster than the fridge drains.

Last updated: March 20, 2026

Written and maintained by Dan Dadovic, Commercial Director at Ezoic Inc. & PhD Candidate in Information Sciences. He works professionally as Commercial Director at Ezoic Inc., leading revenue strategy across digital publishing.

Disclaimer: Calculator results are estimates based on theoretical formulas. Actual performance varies with temperature, battery age, load patterns, and equipment condition. For critical electrical work, consult a licensed electrician.