12V Compressor Fridge Power Consumption: How Many Ah per Day, and What Battery and Solar You Need
How much a 12V compressor fridge draws per day, why rated amps only size the cable, and how to size battery and solar, with Dometic, BougeRV and Alpicool data.
A compressor fridge is the one load in a camper, van or boat that runs day and night. It is also the load VoltPlan users enter most often by hand in the diagram editor: 49 of the 609 custom components created in the 30 days to 26 October 2026 were fridges, from small Alpicool boxes to Dometic CFX3 and Kings drawer fridges. Most of them come with the same question: how many amp-hours does it use per day, and how big do battery and solar have to be?
This is a researched guide, not a hands-on test; we have not measured these fridges ourselves. All figures come from the manufacturers' product pages and data sheets. Where a manufacturer publishes no daily consumption, we say so and show how to estimate it.
Rated amps size the cable, average amps size the battery
Every compressor fridge has two numbers that are easy to mix up:
- Rated current is what the fridge draws while the compressor runs at full speed, plus start-up. Dometic rates the CFX5 45 at 9.4 A on 12 V. This number decides the cable cross-section and the fuse.
- Average consumption is what the battery sees over a day. The compressor switches on and off (or slows down), so the average is a fraction of the rated current. Dometic states 0.76 Ah per hour for the same CFX5 45 at 32 °C ambient and 4 °C inside.
The daily figure is the average times 24 hours. For the CFX5 45 that is 0.76 Ah x 24 h, about 18 Ah per day, or about 220 Wh at 12 V. Sizing the battery on 9.4 A x 24 h would give 226 Ah per day, more than twelve times too much.
The share of time the compressor runs is called the duty cycle. It is not a fixed property of the fridge: it rises with outside temperature, a colder setpoint, a freezer zone, frequent opening and poor ventilation around the condenser.
What the manufacturers publish
| Fridge | Volume | Rated draw at 12 V | Daily consumption from the maker |
|---|---|---|---|
| Dometic CFX5 45 | 46 L, single zone | 9.4 A | 0.76 Ah/h at 32 °C ambient, 4 °C inside: about 18 Ah/day |
| Dometic CFX5 75DZ | 75 L, dual zone | 9.8 A | 2.45 Ah/h with 4 °C and -15 °C zones at 32 °C ambient: about 59 Ah/day |
| BougeRV CRPRO 30QT | 30 qt (about 29 L), single zone | 60 W MAX mode, 45 W ECO mode | not published |
| Alpicool C20 | 19.8 L, single zone | 60 W, 5.0 A | not published |
The two Dometic rows show how much the freezer zone matters: the 75DZ with one side at -15 °C uses roughly three times the energy of the 45 litre fridge-only model under the same hot test condition.
For fridges without a published daily figure, estimate with a duty cycle. A compressor running about a third of the time in warm weather is a common planning value; for the Alpicool C20 that gives 5.0 A x 24 h x 0.35, about 42 Ah per day as a cautious upper estimate. Community figures for whole-day consumption cover a similar range: the womoforum.de wiki on retrofitting a compressor fridge gives typically 20 to 60 Ah per day. Your own fridge will land somewhere in that range depending on climate and use.
Sizing the battery
Multiply the daily consumption by the number of days the fridge has to run without charging, then divide by the share of the battery you want to use:
| Daily fridge use | 2 days, 80 % usable | 3 days, 80 % usable |
|---|---|---|
| 18 Ah (CFX5 45, Dometic figure) | 45 Ah | 68 Ah |
| 40 Ah (typical mid-size fridge, warm weather) | 100 Ah | 150 Ah |
| 59 Ah (CFX5 75DZ with freezer zone) | 148 Ah | 221 Ah |
The 80 % suits LiFePO4 with a reserve; with lead-acid or AGM, plan with about 50 %, which doubles the bank. The fridge is rarely the only load, so add lights, water pump, phones and heater fan before you settle on a size. The battery runtime calculator shows how long a given battery lasts for your loads, and the battery bank sizer works backwards from the days of autonomy you want.
Sizing the solar
Convert the daily amp-hours to watt-hours (Ah x 12.8 V for LiFePO4), then use the rule from our solar panel sizing guide: watt-hours x 1.5 for system losses, divided by the peak sun hours at your location.
- Summer in central Europe (about 4-5 peak sun hours): 40 Ah per day is about 510 Wh, which needs roughly 150-190 W of panel. The CFX5 45 at 18 Ah per day needs about 70-90 W.
- Winter in central Europe (about 1-2 peak sun hours): the same 510 Wh would need 380-770 W of panel. That is why most winter campers charge from the alternator or shore power as well; our DC-DC charger comparison covers the alternator side.
The solar panel calculator runs this for your location and all your loads.
Wiring a 12 V fridge so it does not cut out
Most "my fridge keeps switching off" problems are voltage drop, not an empty battery. The compressor starts at full current, a long thin cable drops the voltage at the fridge, and the fridge's own battery protection switches it off even though the battery is fine.
- Wire it directly, not through a lighter socket. Cigarette lighter sockets and their plugs are a common source of voltage loss. A dedicated fused circuit from the distribution board or busbar is more reliable.
- Size the cable for the rated current and the length. Use the rated draw (9.4 A for the CFX5 45, 9.8 A for the 75DZ, 5.0 A for the Alpicool C20) and the full out-and-back length in the wire gauge calculator.
- Fuse the circuit at the source. The fuse protects the cable, so it follows the cable size; use the value from the fridge's manual. Our fuse sizing guide explains placement.
- Check the battery protection setting. Compressor fridges switch off below a set voltage, often with low, medium and high levels. LiFePO4 batteries hold their voltage until they are nearly empty and have their own BMS, so the setting mostly decides how much cable voltage drop the fridge tolerates. Compare the cut-off voltages in the manual with your battery and wiring.
- Give the condenser air. Built-in fridges need ventilation clearance around the compressor side; a fridge in a closed cupboard runs longer and uses more.
Which fridge for which build
- Van or camper with a 100-200 Ah LiFePO4 bank: the Dometic CFX5 45 uses vacuum insulated panels, and Dometic states its consumption under a hot test condition, which makes battery planning straightforward. Its 18 Ah per day is the lowest published figure in this list.
- Fridge plus freezer for longer trips: the Dometic CFX5 75DZ runs one zone as a freezer. Plan the battery for about 59 Ah per day in hot weather if you use the freezer zone.
- Mid-size box in the 30 quart class: the BougeRV CRPRO 30QT has an ECO mode that lowers the rated draw from 60 W to 45 W, which helps on a smaller battery.
- Car, small van or weekend use: the Alpicool C20 is a compact 20 litre box with a 5.0 A rated draw.
Our direct links for the two CFX5 models currently go to Amazon Germany; in other countries the link opens an Amazon search for the model. Prices for all four vary a lot between stores and sales, so check the current price at the retailer.
Plan it in the diagram
Put the fridge, battery, solar controller and fuses into the free VoltPlan diagram editor. The catalogue fridges come with their rated draw and a duty cycle preset, so the daily energy budget, cable size and fuse rating are calculated together, and you can adjust the duty cycle for your climate.
FAQ
How many amps does a 12V compressor fridge draw?
While the compressor runs, a typical 12 V compressor fridge draws a few amps, with rated values of about 5 to 10 A depending on model; Dometic rates the CFX5 45 at 9.4 A and the CFX5 75DZ at 9.8 A. Averaged over a day it is much less, because the compressor cycles: Dometic states 0.76 Ah per hour for the CFX5 45 at 32 °C ambient.
How many Ah per day does a 12V fridge use?
Usually between about 20 and 60 Ah per day. A well-insulated single-zone fridge like the Dometic CFX5 45 is rated at about 18 Ah per day at 32 °C ambient, while a dual-zone fridge with a freezer zone like the CFX5 75DZ reaches about 59 Ah per day under the same condition.
How long will a 100Ah battery run a 12V fridge?
With a 100 Ah LiFePO4 battery and 80 % usable capacity, about 80 Ah are available. That runs a fridge using 18 Ah per day for about four days, one using 40 Ah per day for about two days, and a dual-zone fridge with a freezer at 59 Ah per day for a little over one day, without any charging and with no other loads.
How much solar do I need to run a 12V fridge?
In a central European summer, roughly 70-90 W of panel covers an efficient fridge using about 18 Ah per day, and 150-190 W covers a fridge using 40 Ah per day. In winter, solar alone is rarely enough; plan for alternator or shore charging as well.
Can I run a 12V fridge from the cigarette lighter socket?
It works for short trips, but the socket and plug often cause voltage drop, and the fridge's low-voltage protection then switches it off. For permanent installation, wire the fridge directly with a cable sized for its rated current and its own fuse.
Why does my 12V fridge keep switching off?
Most often the voltage at the fridge falls below its battery protection threshold when the compressor starts, because the cable is too long or too thin or a connection is poor. Measure the voltage at the fridge while the compressor starts, check the cable size, and review the protection level setting.
This article was created with the assistance of AI.
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