How Much Energy Is your Dometic Pulling? We Tested The Top Dometic CFX3 Refrigerators Power Consumption
Working in the off-road and overland industry has required me to become intricate with the products that I recommend and sell. Portable fridges have been in high demand, and are a popular request for someone building a vehicle.
The first question that comes up when going over the possibility of a fridge is “how much power does it use?” I scoured the internet to find answers, but nothing was readily available. So I hatched a plan to come up with a test of my own.
The Test
The concept is simple. In order to test multiple portable fridges to see how they compare to each other, a test must be created. Any good test follows some simple procedures to ensure that the data is accurate and can be used to compare results.
When developing a test for these fridges, controllable variables must be identified and eliminated. For this test I will control as many of these variables as possible to draw some accurate conclusions on overall power use.
The contenders for this test are two of the newest Dometic fridges in the CFX3 line, the 55IM and the 75DZ, and my original CFX50 that is about 5 years old. The 55IM is one of the most popular CFX3 sizes as it fits very well for most vehicle sizes. The 75DZ is the smallest dual-zone fridge that Dometic offers, and is a requirement for consumers that need a separate freezer option.
The Test Parameters
As with any scientific test, strict and consistent parameters must be adhered to.
- Three fridges in the same vehicle for a 48-hour test period
- Single battery source with 3 separate monitoring devices
- Fridges filled to 50% overall capacity with identical “ballast”
- Ballast can = 525mL stacked volume
- CFX3 55IM (53L capacity) = 50 cans
- CFX3 75DZ (75L capacity) = 72 cans
- CFX50 (46L capacity) = 44 cans
The Power Source
To complete this test, I needed a big power source. Thankfully, I had access to one in the form of a 200Ah Victron LiFePO4 battery. I modified the top of the battery to mount the other Victron products that I needed to complete this test using a custom ABS plastic plate.
Big thanks to my local Victron experts and friends at Bend Battery for both lending me the monitoring components for this test and for sanity checking my overall system design!
The BMS protects the battery from an overdraw that could damage the battery, and the three SmartShunts provide power to each fridge and allow for monitoring energy use individually. I call it, Frankenbattery.
The Test
The fridges were all loaded at the same time after being in the vehicle for a 24-hour period with the lids opened and unplugged to equalize all of the unit temperatures. They were loaded using uncooled “ballast” that were all stored in the same location leading up to the test.
After being loaded, the fridges were all plugged into AC house power and set to the designated temperature of 34ºF. Overnight, they pre-cooled to a stable interior temperature and at 9am, they were unplugged from house power and plugged into Frankenbattery.
For 48-hours, the fridges remained sealed. They were driven around with the windows open, cooling to ambient daytime temperatures. All three fridges experienced a period of time where the 4Runner was parked with the windows closed.
Overnight, the windows were cracked and the interior was allowed to cool. These conditions were meant to replicate “average” traveling conditions. For this test, the fridges were left sealed without ever being opened to eliminate another variable and to keep the data as consistent as possible.
The Results
The three fridges were monitored using the VictronConnect app constantly during the 48-hour test period. The data was recorded at the 24-hour mark and again at the 48-hour mark to draw comparisons.
Looking at the data, you can see there is a correlation between the size of the fridge and its overall energy usage. With the 55IM pulling almost 46Ah over 48-hours, you can easily expect to use the fridge over a weekend of camping without worry. On the higher end at almost 57Ah, the 75DZ might require a larger battery bank or an auxiliary energy source such as solar to keep it running trouble-free while stationary for a longer period of time.
24-Hours
– CFX3 75DZ — 31.1Ah — 1.29Ah/hr
– CFX3 55IM — 24.8Ah — 1.03Ah/hr
– CFX 50W — 21.7Ah — 0.90Ah/hr
48-Hours
– CFX3 75DZ — 56.8Ah — 1.18Ah/hr
– CFX3 55IM — 45.6Ah — 0.95Ah/hr
– CFX 50W — 40.3Ah — 0.84Ah/hr
Battery Tip
The largest battery you can fit in the 4Runner battery tray without going to a 31M (where fender cracking is common) is a Group 27.
Below are a few common battery options for the 5th gen 4Runner:
- X2Power Group 27F: Check Price
- NorthStar Group 27F: Check Price
- Odyssey Group 34: Check Price
- NorthStar Group 31: Check Price
- Odyssey Group 31: Check Price
All of this to say that one of the best batteries you can equip your 4Runner with can provide 100Ah of capacity. But, 100Ah of capacity doesn’t mean you’ll get the full 100Ah. AGM batteries will only happily produce about 2/3 of their total capacity consistently while staying healthy. So, keep that in mind when you’re calculating your fridge usage versus battery capacity.
Trail Takeaway
This test was exactly what it is named, a test. It was a proof-of-concept for this type of comparison article that I have been able to learn from as a writer, and I think that the results show it worked! What this means for me is that I can put different 12v consuming products against each other to relay the information and data to you!
For this test, the fridges performed very well and kept the “ballast” completely cold during the 48-hour period. So much so that they somehow looked a little… bluer… by the end! Comparing the 24-hour consumption to the 48-hour mark, you can see that as everything got to its ultimate static cold temperature, the fridges became more efficient with time as long as they remained unopened. For a future test, I may incorporate an open/close procedure to the list to make it as realistic as possible to a normal camping trip.
What else would you like to see us compare? Differences between different packing techniques? Different brands or models against each other?
Hi, researching a similar fridge for my Volvo XC90. Does your data have a figure for peak amperage draw on the 75? Looks like it averaged just over 1 amp of power draw. I’m trying to avoid any permanent wire taps into my under-warranty vehicle. I have three “100ah” (skeptical of performance) Chinese lithium batteries to work with as well as a 300wh commercial lithium power pack that is my main camp power now.
Great test. What was the Wh of the battery? Were all 3 fridges running off the single battery simultaneously? Trying to figure how the state of the battery charge is attributed to each fridge. Thanks.
Very thorough test! Thanks for doing the testing and sharing in this article. Questions about temperatures (conditions) outside the three portable fridges. Looks like sun would not be on the three portable fridges due to window coverings.
What was the ambient temperature?
Ambient outside temperatures, and in-the-vehicle temperatures, would be very useful to know! Even estimates from observation/feel. Do not see snow. Side window coverings, but was a windshield cover also used? Article has December date, but was testing performed right before such as mid- to late-November? Testing was done in Central Oregon? Thanks.
buying a lot of Coors for science = brilliant. BTW could you share some info on the window inserts seen in your photos.. Thanks!