There is nothing magical about a residential chest freezer, in its ability to cool. It is all about the extra insulation, and the fact that there is no door seal at the bottom to let the heat enter the box which the cooling unit must then remove.
The 'cold air spilling out' on a front loading fridge is given more weight by many than it actually deserves. When the Lid is opened on a chest style fridge, the very act of opening the lid is going to exchange a significant portion of the air within the box. Is it more efficient than a front loader, of course, but some would have you believe it instills magical properties. It is my opinion that the chest style is more efficient simply because there is no thin door seal at the very bottom like on a front loader, that the act of opening the door/lid will exchange a significant portion of the air inside either way.
Now if one were to leave the fridge open like many stick and brickers do when getting food, then the difference in efficiency in design would be more significant. But for a battery powered dweller, leaving the door open is unwise, and the actual difference in battery power consumed would be minimal and difficult to measure, all other factors being equal.
When powering a 120Vac refer, the inverter choice makes a huge difference. It must be big enough to handle the start up surge and it must be kept on 24/7 to provide power anytime the fridge decides to kick on.
My Wagan 400 watt PSW inverter could not handle the start up surge, and if it could, it draws 0.24amps turned on, powering nothing
My coleman 800 watt MSW inverter might handle the start up surge, but it consumes 0.62 amps turned on powering nothing.
My 12vDC Vitrifrigoc51is rarely ever consumes more than 0.8 amps per hour. It barely uses any more electricity than my MSW inverter would, turned on, powering nothing.
My front loading fridge has 3/4" foil faced foam board insulation added to it, and resides within an insulated cabinet designed to promote airflow over and through the cooling unit. I recently had a friend's ARB 50 quart chest style fridge, and it had the extra insulative cover as well. My front loading Vitrifrigo averaged about 15 to 20% less energy consumption than that ARB fridge in the 3 weeks I had it in my possession. Why, because of more insulation and better heat removal from condenser. It should be noted my VF fridge was opened more often than the ARB too.
If you seek the least battery power consumed on any compressor fridge, it is best achieved by extra insulation, and making sure the condenser is not recycling air it itself has already heated. Get a chest style compressor fridge and make a foil faced foamboard box for it making sure not to obstruct the vents for the cooling unit. If the compressor is a Danfoss BD35f, this compressor controller can handle powering 0.5 amps of computer fan. The fan which comes on most condensers consumes only 0.12 amps or so. One can hook another fan to the compressor controller and exchange the air around the unit better and increase efficiency. It is very easy to hook up another fan to the Danfoss compressor controller, and it will make up for its own energy consumption easily, and promote the lifespan of the compressor too.
Decreasing the heat of the interior of the vehicle also makes a huge difference in the fridges duty cycle and battery consumption. Keep the sun out with reflective window shades on the sunny sides, and have a means of exchanging inside air for outside air.
Computer fans do better at pushing air through a restriction rather than pulling it through a restriction and are quieter too. I removed the noisy 0.12amp 120MM fan (72 CFM) provided with my Vitrifrigo, that was mounted to pull air through the condenser, and replaced it with a Noctua NF-F12 fan which moves ~53CFM and consumes only 0.05amps. This fan is now mounted to push air through the condenser and across compressor and controller. It pulls cool filtered air from the floor below the fridge, and it forces it out of the fridge compartment with no chance to be recycled. The amount of time the fridge compressor cycled on for, instantly dropped with this simple modification, and I find it a bit perplexing why they would not employ this fan orientation from the factory.
An inverter turned on and powering nothing can consume nearly as much as a dc compressor fridge would consume in the same time frame.
Some inverters promote very low parasitic currents or advertise a standby feature, but they all seem to be high dollar units.
There is no free ride with refrigeration via battery power, no magical solution which saves money. Anything requiring an inverter is going to require more battery capacity, and more recharging ability, and that cost must be factored in, along with shorter overall battery life as they will simply be used up faster even if the charging sources are increased and they do get fully charged daily.
If one is full time van dwelling, and living primarily off of battery power, then the best option, least expensive in the long run, is a 12v compressor fridge. Add some insulation and make sure the cooling unit can breathe easily, and one can do no better at this point in time.
If one already has a huge battery bank and plenty of Solar, then that person can get away with powering an 120Vac residential fridge, and this solution also makes sense for those who drive from rv park to rv park and get to plug in to the grid on arrival. Many with larger RV's whose finicky absorption/propane/3way fridges fail prematurely or cool inadequately go the residential fridge route and are happy as they do not or rarely boondock, and likely have generator backup anyway.
The person setting up a new system for boondocking, and decides to save 350$ buying a residential fridge instead of a 12vDC fridge, will spend more than 350$ on the larger inverter, the extra battery capacity, and the extra charging capability required to run it with ease. The battery lifespan will also be shortened, even if they are recharged properly. And the likelihood that they are charged properly diminishes with a higher load cycling on and off, and the inverter itself chewing up 0.5 amps an hour just waiting for the fridge compressor to cycle back on.
Even if one already has a dorm fridge, and an inverter big enough to handle it, one needs to have enough battery capacity and recharging ability to power the energy hogs.
Is it workable? Certainly, is it economical in the long run, likely not.
If one needs to have refrigeration, bite the bullet and purchase a 12v compressor fridge. It will save you money in the long run.
