12v Refrigerator vs. 120

[Glennman]

In looking at refrigerators out there that are all electric, I see some 12v models. Outside of the price differences, is a 12v going to be more efficient as a 120v that is running on an inverter? Do the 12v models work as well???

[mqbus767]

You are, of course, aware that the inefficiencies in inverters will consume some percentage of the electricity and blow it off in heat. I'm reminded of this every time I open my electrical bay while my air conditioning is running. So for sure you're losing some efficiency when you use an AC fridge.

This is all theoretical, so don't take this as imperical proof for every comparison. There are at least three major components to a refrigeration system that effect it's performance/efficiency:

* Insulation
* Compressor
* Refrigerant

For a DC powered refrigerator though, you're generally gaining back more than just the inversion losses. Most DC refrigerators that I investigated had quite a bit more insulation than an equivelant AC powered fridge. I can only guess that, because these are typically used in off-grid applications, the manufacturer is trying to boost their spec. sheet numbers as much as possible. Of course the trade-off is decreased usable CU inches.

The DC powered fridges also typically have another advantage in that they use variable speed compressors (see Danfoss compressors) that allow the controller logic to ramp up/down the refrigerant circulation in a more efficient manner. Modern mini-splits also use variable speed, scroll type compressors to reduce start-up amp spikes. AC fridge compressors are usually just on/off.

In my research, the refrigerant tends to be the same between AC and DC fridges (R134a).

At the end of the day we decided to just buy a simple Lowe's AC refrigerator because of cost. An equivelant number of CU inches in a DC fridge is about double the money of an AC fridge. This also gave us a wider range of fridges to choose from since DC fridge models/manufacturers are far fewer. I plan on having ample solar power on the bus, so I'm not really worried about the inversion/compressor loses. Last I checked, after initial cooldown, I could run our fridge for at least 24 hours on the battery without any input.

[richard5933]

If you found an extremely efficient 120v fridge that can run on 1 amp @ 120vac, that would still require over 10 amps @ 12vdc. Plus any extra for the inverter loss.

We had a 12vdc fridge (Vitrifrigo) in our bus. It ran directly from 12vdc and consumed about 6 amps from the batteries when it was running - it had about a 50% duty cycle once cooled down.

How well do the 12vdc fridges work? If you eliminate the low-end models (which won't work well/for long regardless of the power source) they work extremely well. Our Vitrifrigo would be at temp within an hour or two at most, and it would keep out ice cream hard enough that it was very difficult to scoop. Never had milk go bad or any problems with the temp regulation.

There are things you can do to help any compressor fridge work well, like ensuring adequate ventilation and adding pancake fans to the compressor coils to boost the ability to shed the heat.

Like already mentioned, these 12vdc fridges were initially designed for use in the marine world and are very well insulated. They are also intended for use in vehicles and can withstand being on the road. A residential fridge may or may not like being inside a rolling earthquake.

In the end though, it's all going to come down to a few factors...how big is your battery bank, how fond are you of running the generator when necessary to recharge them, how long you plan to be off grid, and what your budget is.

If you have solar on the roof then go ahead and put whatever fridge you like. As long as you have more solar output then your constant loads you can run what you want. Otherwise, do the math on the energy use and figure out what works best for you.

[Utahclaimjumper]

 I have 400 watts of solar on the roof,, and a 4X6V battery bank..  When my RV type fridg. crapped out I went looking for a residential fridg. that would fit in the hole and be efficient on 120 inverted power..  I found it in a Frigidaire energy star rated 1 amp that was twice the inside voluum of the old one and would fit perfectly..  It has been one year ago and I couldn't be happier,, all this on less then half the cost to replace the previous one..>>>Dan  ( I also have a 3000 watt PSW inverter.)

[luvrbus]

Be careful with small 120v fridges some tell you they cannot be built and will not work over a 100 degrees.We install one from H/D in Tom Caffery's 4106 GM lol we both said he was better off with his old propane fridge from the 70's ,I have nothing against the propane fridges except for the price 

[oltrunt]

I just replaced the frig in my little bus with a Frigidare 1 amp 120v standard compressor.  It uses R 600 as the coolant (which is flammable under the "right" conditions) but WAY better than R 134 or R12 just as they advertised it would be.  My old frig (134) took overnight to cool the box and then ran about 60% of the time.  The new frig was down to 40 degrees in less than an hour and cycles at about 30%--and it is so quiet I have to put my hand on it to make sure it is running.  The old frig is 20 years old and used when I got it but it is still running.  I won't live another 20 years so I won't be around to report--unless the new frig craps out way sooner.  Jack

[windtrader]

If you plan on having an off-grid sized solarbattery setup, then an AC 10-11 sqft is a go to refrig. Efficient ones run around 600 watts per day, inverter runs 24x7, Starlink uses more than refrig, big deal. From all the reports, if properly mounted and secured, an ac unit lasts fine.

[luvrbus]

I have a total electric coach with 21 cf side by side counter depth fridge that has the energy star rating and  it is a energy hog for a 3 amp rated fridge

[dtcerrato]

We love our LP/120V absorption RV fridge. Also run a 12V/120V chest fridge/freezer that 400W solar keeps up with.

[chessie4905]

current travel trailer uses Norcold 110/ propane. Always ice cold no matter when outside temps over 100 degrees. The 12 volt/ 110 Norcold could NEVER provide that performance in hot weather.

[Jim Blackwood]

I think the choice should largely depend on your power source. If you are mostly connected to the grid 110v is the obvious choice. If you have solar power either of the electric options can be good ones. In my case I have onboard propane for the range and the generator anyway so a propane fridge makes the most sense as it's appetite is minuscule compared to the genset and won't even be noticed.

Jim

[dtcerrato]

In our lifelong experience with RV absorption fridges the LP mode cools the most efficiently. A simple addition on the back of an absorption fridge is a small computer fan that blows up through the upper hot coil of the fridge. We only use it in temps around a 100°F it really helps the cooling unit when it taxed with high heat. Fwiw.

[windtrader]

The absorption style on propane does use fuel. Just want to clarify that because mine was using about a tank a week and nearly it all was the refrigerator. the stove is propane but it runs for months on a tank.
I have a replacement flame pilot and the old one may have consumed excessive fuel. It's getting installed in a couple weeks but hartd to judge if it improves fuel use until some time passes.
Never know, the consumption drops a lot, I might keep the old one in a bit longer. lol

[luvrbus]

The absorption style on propane does use fuel. Just want to clarify that because mine was using about a tank a week and nearly it all was the refrigerator. the stove is propane but it runs for months on a tank.
I have a replacement flame pilot and the old one may have consumed excessive fuel. It's getting installed in a couple weeks but hartd to judge if it improves fuel use until some time passes.
Never know, the consumption drops a lot, I might keep the old one in a bit longer. lol

All the absorption fridges I ever owned used about a gal a week,could be the t stat is letting the flame  burn all the time ,water heaters will suck up some propane in hurry

[Tedsoldbus]

 I understand all the people that love this solar thing, but I guess I just hope we all like what we have.  We are used to being able to run the fridge on propane and there is a 35 gallon propane tank buried in the belly of the bus behind panels. And call me dangerous but we still run the fridge on propane going down the road like we did with our 3 previous RVs. The bus has a 35 gallon propane tank and I have the tank and valve checked once a year. But we think it is made to do what we are doing with it.

We only have 6 bay doors in the shorty. One is monster Kubota Gen that I can work on, it is pretty quiet, and it is already there. I like it, it works great, and all the wiring is set up to be happy getting juice from it.

I don't know how many batteries it takes to store the juice from a roof full of panels, but I suspect it is more than our little house battery bay wants to hold. I have not looked at cost for panels and battery bank I guess because we don't think we want to go that route.

Again there are so many options and I just hope people like what they have. We like our generator and our fridge that is propane or electric. Rita likes the gas range. We have a 200 gal fuel tank so thinking we could boondock with non stop cloudy days until we run out of water. We are just so content with how well all of it works. I don't want to start tearing into the bus to jerk out the generator, the propane tank, and drill holes in the roof.

I am not saying it is better. Just better for us. I would sing a different tune if we were full timing, but not doing that again. We like to take trips, but like having a house.

However, it is always fun going to bus gatherings to see all the different systems people have. Especially the ones they came up with on their own! All part of the "BCM" thing where individuals convert these things in so many different ways.