A 12V fridge is almost always the largest single load in a touring setup, and it's the one people most often get wrong. The number on the box is measured in a lab; the number you live with depends on where you camp and how you pack.
The short answer
As a rough planning figure, expect roughly 15–25 Ah per day for a 15–30 L fridge, 25–35 Ah for a 35–50 L, 30–45 Ah for a 55–75 L, and 40–60 Ah for an 80 L+ or dual-zone unit. Those are daily totals over 24 hours, in reasonable Australian conditions.
The same fridge can sit at either end of its range depending on ambient temperature alone. A 40 L fridge that draws 28 Ah on a mild coastal day can push past 45 Ah parked in full sun in the Kimberley.
Why the rated figure misleads
Manufacturers usually quote current draw while the compressor is running — something like "2.5 A". That is true, but a fridge doesn't run continuously. It cycles: the compressor pulls down to the set temperature, stops, and restarts when the box warms up.
What matters is the duty cycle — the share of each hour the compressor actually runs. In mild conditions that might be 25%, so 2.5 A becomes an average of 0.6 A, or about 15 Ah per day. In 35°C heat the same fridge might run 60% of the time, which is closer to 36 Ah. The rated draw hasn't changed; the duty cycle has.
What actually moves the number
- Ambient temperature. The dominant factor. The compressor works against the difference between inside and outside, so a hot day costs far more than a warm one.
- Where it sits. A fridge in direct sun in a closed canopy is in a hotter environment than the air temperature suggests. Shade and airflow around the condenser are worth real amp-hours.
- Freezer mode. Running a fridge as a freezer typically adds around a third to daily consumption, sometimes more.
- How often you open it. Every opening dumps cold air. Frequent short openings are worse than one considered one.
- How full it is. A well-packed fridge holds temperature better through each off cycle. Chilling warm food and drink from scratch is what costs energy.
Turning that into battery size
Fridge draw alone doesn't tell you what battery to buy — you need your whole daily total, how long you'll go without charging, and how deeply your battery can be discharged. A lithium battery is usable to about 85% of its capacity, while AGM is closer to 50%, so the same daily load implies a very different bank.
As a worked example: a 50 L fridge at about 30 Ah/day, plus lights and phone charging at roughly 7 Ah, is about 37 Ah per day. Cover two days without charge on lithium and you need about 87 Ah of usable capacity — call it a 100 Ah battery. The same requirement on AGM needs closer to 150 Ah.
Worth knowing: a fridge runs 24 hours a day, so it's the load that keeps drawing overnight when there's no solar. That's why two setups with the same daily total can behave very differently — one that's mostly fridge is much harder on the battery overnight than one dominated by daytime device charging.
Measuring your own
Estimates get you a system that's about right. If you want certainty, a battery monitor or shunt showing amp-hours in and out will tell you your real consumption within a couple of days of camping — and it's the same instrument that tells you whether your solar is actually keeping up.
You can put your own fridge, gear and travel pattern into the 12V calculator and see the battery, solar and charger sizing that follows from it.