A good 80–85L upright compressor fridge can average around 30Ah a day in mild, controlled conditions. In a real 4WD canopy or caravan, allowing 40–50Ah a day is more realistic, and a hot outback day can push the planning figure closer to 60–65Ah.
That range is wide because the badge on the fridge does not tell you how long the compressor will run. Ambient temperature, cabinet ventilation, door openings, freezer use and the temperature of the food going in all change the daily result.
Why AMP'D added this guide: in an anonymous 24-hour calculator sample ending 21 August 2026, an 85L upright fridge appeared in 12 of 22 completed calculations. It was the most common fridge choice in that sample.
The short answer: about 30–65Ah per day
| Conditions | Planning figure | What that represents |
|---|---|---|
| Mild, well ventilated | Around 30Ah/day | Efficient fridge, roughly 25°C ambient, limited door opening |
| Normal touring allowance | 40–50Ah/day | Mixed weather, regular use and some installation loss |
| Summer or hot canopy | 55–65Ah/day | High ambient heat, frequent opening or poor airflow |
These are planning ranges, not a promise for every model. A watt meter or battery monitor is the only way to know what your own fridge and installation use.
Why the manufacturer figure can look much lower
Bushman publishes an average of 1.25 amps per hour over 24 hours for its DC85-X at 25°C ambient with the fridge set to 4°C. Multiply that average by 24 hours and it works out to about 30Ah per day. Bushman's own battery-and-solar guide also lists the 85L model at about 30Ah per day.
That is useful evidence of what an efficient fridge can do, but 25°C is not a closed canopy sitting in the sun. The published number also cannot know how often your family opens the door, whether you load warm drinks, or whether the compressor compartment can get rid of heat.
AMP'D therefore uses a conservative 50Ah/day spring and autumn baseline for the generic 85L upright option. The calculator scales that to roughly 43Ah in cool conditions and 65Ah for summer or outback use. It is deliberately a system-sizing allowance rather than a claim that every upright fridge constantly draws 50Ah.
Running amps are not daily amp-hours
A compressor might draw several amps while it is running, then almost nothing after the thermostat switches it off. Reading the running current and multiplying it by 24 hours assumes the compressor never stops, which badly overstates normal use. Looking only at a low average can make the opposite mistake in hot weather.
The useful number for battery sizing is the total energy used across a full day:
Daily use (Ah) = average current across the day × 24 hours
If a battery monitor shows an average of 1.8A across a full day, the fridge used about 43Ah. If it averages 2.5A during a very hot day, that is about 60Ah.
What makes an upright fridge use more power?
- Heat around the cabinet: a dark canopy or caravan wall in full sun can be far hotter than the outside air.
- Poor ventilation: the compressor has to work harder if warm air cannot escape behind the fridge.
- Door openings: cold air drops out of an upright when the door opens, particularly when people stand there deciding what they want.
- Warm food and drinks: cooling a carton loaded at camp takes far more energy than maintaining food that was already cold.
- Freezer use: holding a freezer compartment below zero increases compressor run time.
- Low voltage at the fridge: undersized cable, long runs and weak joins can cause voltage drop, poor performance and low-voltage cut-outs.
- Dust around the condenser: restricted airflow makes it harder for the fridge to reject heat.
How long will a 100Ah battery run an 85L upright fridge?
| Fridge use | 100Ah lithium* | 100Ah AGM* |
|---|---|---|
| 30Ah/day | About 2.8 days | About 1.7 days |
| 50Ah/day | About 1.7 days | About 1 day |
| 65Ah/day | About 1.3 days | Less than 1 day |
*Fridge only, using 85% of lithium capacity and 50% of AGM capacity. Lights, phones, pumps and other gear shorten these times. Battery age, temperature and voltage cut-out settings also matter.
For a fuller explanation, see the guide to running a 12V fridge from a 100Ah battery.
How much solar should you allow?
At 50Ah per day, the fridge alone needs roughly 600Wh returned to a 12V system. In decent spring or autumn sun, 200W of well-positioned solar can theoretically cover that fridge load after normal system losses. It leaves very little room for shade, hot panels, cloudy weather or anything else running from the battery.
For an 85L upright plus normal lights and phone charging, 300W is a more useful touring starting point in mixed conditions. Roof-only solar may need more wattage if the vehicle is parked in shade; a portable panel can often do more by being moved into clear sun.
Use the guide to sizing a solar panel for a 12V fridge for the full calculation.
Will a 25A DC-DC charger keep up?
It can, especially when solar is doing part of the work. Replacing a 50Ah daily fridge load through two hours of driving needs about 27A after allowing for charging losses. That lands between common 25A and 40A sizes. Add lights, devices and a pump, or cut the drive to one hour, and 40A becomes the more practical recovery size.
If solar reliably replaces 20–30Ah while camped, a 25A charger may be plenty. The answer comes from the energy shortfall and driving time, not the fridge size by itself. See whether a 40A DC-DC charger is enough for your setup.
Installation matters as much as the fridge
Use the cable size, fuse protection, clearances and ventilation required by the fridge manufacturer. Upright compressor fridges can have a brief startup surge, so a weak cigarette-lighter socket or long undersized cable may trip even when the average daily draw looks low. A dedicated fused circuit with sound joins is the safer, more reliable approach.
Pre-cool the fridge before leaving, load cold food where possible, leave space for air to move around the compressor area, and clean dust from the vents. Those boring details can save more battery than buying another small panel and leaving the installation hot and starved of airflow.
The practical starting point
For planning an Australian touring system around an 80–85L upright compressor fridge, start with 50Ah per day. Drop toward 30Ah only when you have a proven, efficient installation in mild conditions. Allow 60–65Ah when the fridge will live in serious heat.
Then add the rest of your gear. A typical upright-fridge setup often ends up around 60–70Ah per day once lighting, phones and a water pump are included — which is why a 120Ah lithium battery, roughly 300W of solar and a 40A DC-DC charger appeared so often in AMP'D's recent calculator results. They are common outcomes, not a shopping list for every vehicle.
Put your actual gear, shade, season and driving time into the AMP'D 12V calculator before choosing a system.
Important: these are planning estimates. Follow the fridge and electrical-equipment manuals, size cable and fuses for the actual installation, and have the finished design checked by a qualified auto electrician where required.