How long will my battery run my fridge?

Runtime = usable battery capacity ÷ (daily use − daily solar). The hard part is knowing your fridge's real average draw, which depends on the fridge, the set temperature, the weather and how often you open the lid.

Getting the numbers right

Average draw, not running current

A compressor fridge cycles on and off, so its draw while running is much higher than its 24-hour average. The best figure comes from a battery monitor or a plug-in 12V meter over a full day in the conditions you camp in. Some fridge makers publish an average consumption figure (often in Ah per day or Ah per hour) at a stated ambient temperature, so check your manual and note the test conditions.

Usable capacity

Don't assume you can use 100% of a battery's rated capacity. Lead-acid and AGM batteries are commonly kept to about 50% depth of discharge for lifespan, and lithium batteries are usually rated for deeper discharge. Enerdrive, for example, quotes its B-TEC G2 cycle life at 80% depth of discharge.^[1] Use your battery maker's figure.

Solar is a daily average

Enter what your panel actually puts back on a typical day, not its rated watts. Shade, season and cloud make a big difference.

If you're working out how to recharge while driving, use the DC-DC charger size calculator.

Sources

This is general information, not a substitute for the manuals for your specific charger, battery and vehicle. Fixed wiring and anything near the starter battery should be installed by a qualified auto electrician.

Last updated: 15 October 2026