Choosing Your Off-Grid Refrigerator

Intermediate

Inside this Article

This Nova Kool RFU 9000 can run on 12 or 24 VDC—or 120 VAC.
This 10-cubic-foot Unique Off-Grid Appliances unit runs on 12 or 24 VDC.
DIY fridge components
Steca specializes in solar-ready applications with DC chest fridges and freezers in various sizes.
Phocos specializes in solar-ready applications with DC chest fridges and freezers in various sizes.
SunDanzer specializes in solar-ready applications with DC chest fridges and freezers in various sizes.
This thermostat control can turn your chest freezer into a refrigerator.
Dometic’s two-way (120 VAC or propane), freestanding 13.5-cubic-foot Elite 2+2 RM 1350 has a water/ice-in-door option.
The components of a propane fridge
The E-Z Freeze 21SS propane fridge.
Diamond Elite 19-cubic-foot propane fridge
Norcold 1210 Ultraline three-way propane/electric fridge.
Unique UPG18 propane fridge.
An old Servel Propane fridge ad.

Life off the grid requires a few adjustments in lifestyle and habits for most people. One of the most crucial is called “load shifting,” which is simply running large loads only when there is extra power coming in that can’t be stored, thanks to a fully charged battery bank.

Unfortunately, some very critical loads can’t be shifted. Refrigerators and freezers are two of the worst offenders—they turn themselves on and off based on internal temperature, without any regard to the status of your battery bank or incoming power.

In the world of off-grid living, the answer to “Which refrigerator is the right one?” is almost always, “It depends.” What’s the most efficient power source—120 VAC or  low-voltage DC? What sizes and models are available? What’s the most efficient arrangement of doors, compressors, and compartments? Is propane a better option? Here are a few points to consider before you buy.

Going Electric

I had to add another 1 kW of PV to run a conventional AC-powered, upright electric fridge/freezer, which replaced the 20-year-old propane model I started my off-grid life with. That big freezer up top opened new worlds for me—like the frozen-food aisle at the local wholesale club and freezing wild game from hunting. Extra bread on the counter that is at risk for growing mold or going stale? Freeze it! Herbs in the garden? Cut ’em up, put them in ice-cube trays with a little water, and pesto-freezo!

But different households have different energy budgets (and different levels of expendable income). My conventional 120 VAC refrigerator/freezer from a big box store cost me $800, plus about $700 to expand the PV array, $500 for a new controller, $2,500 for additional batteries, and another $1,400 for a new inverter I didn’t realize I would need (see “Off-Grid Fridge Vagaries” sidebar). These additions, though, helped the efficiency and performance of my entire home’s energy system. Here are some options and considerations to weigh when you’re choosing a refrigerator and/or freezer for your off-grid home.

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Comments (13)

Escape Artist's picture

Hello to all:

Grasical: Our freezers measure roughly 28" deep, 43" wide, and 35" high. We did not look for Energy Star ratings but simply standard chest freezers that were in good shape. I'd happily post photos but don't see a way to do that here.

Marc Fontana: To compare your 404 kWh/year Energy Star rating, our refrigerator set up uses 55 kWh/year.

Judith: We have the same experience and keep a large (>1 foot) sponge on the bottom of the fridge where the water pools. Each day or two, we remove it, squeeze out the excess moisture, rinse it off, and replace it. Once or twice a month, we mop it up more thoroughly. This has helped with the standing water and mold build up. I believe the moisture is a result of the horizontal positioning of the fridge and is unavoidable. We're in over 10 years with this design and tolerate it. Do any others have ideas on how to deal with this?

judith's picture

Escape Artist, I've been using a Danger Solar freezer converted to frig for several years and have had a terrible time with moisture in the frig. Water standing in the bottom from condensation causing a black mold constant battle! Mold only grows on paper labels, and around the baskets. Any suggestions? Help appreciated.

Denise Binion's picture

At homebrewing supply shops, you can get an override thermostat to control freezers to warmer temperatures for $38 to $135, depending on brand and store.

Escape Artist's picture

For those interested, our full-sized refrigerator uses 150 watt-hours/day and cost us under $300 total. After years of hauling propane tanks to our remote home, many years ago I found a previously-unused regular top-opening chest freezer on Craigslist for $150. For an additional $110, I put a mechanical thermostat at the freezer's AC outlet. I set the mechanical thermostat dial to 40 degrees F, ran the temperature probe into the freezer, and plugged the freezer into the thermostat outlet bypass. Thus, the freezer was turned into a refrigerator since is is de-powered when it reaches 40 degrees, or a standard refrigerator temperature. Based on multiple readings using a Kill-O-Watt meter, we average 150 W/h/d (0.15 kWh/d), which is less than a quarter the rating of the *best* Energy Star refrigerator listed on refrigerator comparison websites.

Our experiment did require that we get used to top-loading organization for our groceries but this was easier than we thought it would be. In addition, we can open the fridge and leave it open for 15 minutes or longer without the guilt associated with the cold air dump that occurred every time we opened our front-loading propane refrigerator.

This also turned out to be much less expensive (and as effective) as if we had purchased one of the straight DC refrigerators. All of those were priced in the thousands of dollars and were significantly smaller.

The experiment was so successful that a few years later we added a second top-loading chest freezer on our back porch (placed there to reduce our energy use during our cold winters). We paid $150 again for one we found on Craigslist and can attest that it uses an average of 450 watt-hours/day around the year (0.45 kWh/d) without any modification, a significant energy savings from all of the other upright front-loading freezers we compared.

It's offered by Backwoods Solar, though many other mechanical thermostats would also work, as it's based on the mechanical thermostats commonly used in domestic hot water systems. (We have NO affiliation with Backwoods Solar.)

Happy to send pictures to anyone who asks.

grasical's picture

I would love to see pics. Also, can you tell me what size freezer you are using and if in your experience there are any options one should avoid or look for in selecting a freezer to modify into a fridge? i.e. Would it matter if it's energy star certified as a freezer or does that become a non-issue when overriding the thermostat?

Clark Gestring's picture

I have been doing offgrid design and construction dice 1987 and boy have things changed, refrigerators included. Up until a few years ago I recommended only propane fridges for part and full time offgrid homes. That's what I have in my part time cabin (serval now ported to natural gas). That way you can leave food in it while gone, since I recommend turning off inverter system when going for more than a few days.

For part time homes I still recommend that because even with D.C. Fridges, if something goes wrong and you kill a battery bank that's more than the cost of a new fridge. I have started recommending new tier 3 energy star fridges for full time and some part time ( were you empty fridge when you leave and still turn off power). The super low power draw of the best tier 3 is an easy add on to an ac solar home. If you want to be extra conservative put a timer on it so it only runs from 7 am to 7pm each day to conserve overnight power. With the lower cost of panels it's not a difficult option to plan fo

When I design a remote commercial bldg or cabin I have been using obsolete for the last 12 years. That way I can design system for actual appliances battery systems, determine generator requirements and size my design to meet those requirements

Final words. Full time home put in tier 3 or better traditional fridge and add panels to cover extra draw (I always include state of charge meters in my systems lead acid turn on generator when top 20% used for long battery life, Hup Solar-One, nicad (my system), or li-ion turn on generator at top 80% used

Part time for a few weeks at a time propane and leave food in it, even though you are turning off power. Part time when always for a few months at a time tier 3 or better standard ac fridge and empty it when you leave and turn off power

Edward-Dijeau's picture

Rather than one two door refrigerator with just one compressor, I used 2 separarate, manual defrost, Units. 1 "Energy Star" single door, manual defrost 11 Cu Ft. refrigerstor with a small in-the-unit freezer compartment, that is only used to provide cooling, set at 40 degrees and I place 5 bottles of 16 ounce driking water that feeezes, for fresh food storage, and one manual defrost 4.4 Cu.Ft.chest type freezer set at 10 to 15 degrees for frozen food. Each unit has it's own 1000 watt inverter that are connected separatly to the battery stack. Once they are down to "set" tempurature, each needs only 400 watts of solar panels and 400 amp hours of battery to run continuously with full daytime Sun from March through October. Compressors after the original inrush only use 115 watts and they run about 30% of the time with abiant tempuratures of 80 degrees or less. On really hot days, they will stay on longer but the days are also longer and I get the maximum charge on the batteries for nightime usage and inrush. This way, the refigerator does not demand from the freezer the lowest setting cut off when the ambient tempuraturs cool off to 40 degrees at night that would let the frezer tempuratures rise. Because the body of both the refrigerator and the freezer are outside on a deck area, in the enclosed back yard in the winter, they use the natural cold of the winter nights to use very little electricity from the limited sunlight. The refrigerator may only come on for 10 minutes every 2 hours durring the day and not come on at all at night thanks to those five bottles of frozen drinking water in the freezer compartment. The freezer only runs a couple of times each day if unopened thanks to the frozen food inside maintaing the tempurature.. I also use remote sensor outdoor transmitters inside of the units that go to the matching frquency digital reciever themometers to monitor their tempurature and a voltage dispay that show the battery stack voltage. if the battery voltage gets to low, I just charge the batteries from another power source rather than switch out the refrigeration units to another source.

Thomas Burnside's picture

Having lived with a propane fridge for years, here is a little trick. After emptying the contents into a cooler for your defrost session, throw a bucket full of warm (or hot) water in the fridge. This will expatiate the melting process and keep you from being temped to chip the ice and damaging anything.

Marilyn Kinsey 2's picture

Sailors often use a holding plate design, which acts like a "Cold Battery", reducing the need for more electric batteries, and panels. We live all summer on just 88 watts of solar panel capacity, running a Technautics holding plate system, which consumes about half the daily electric use, in addition to the autopilot, fans, lights, navigation electronics, stereo, and cell phone amplifier. Super insulated refrigeration box, with top opening lids. We can manage about 3 cloudy days, and then must supplement, running the engine. But, we usually run the engine every day or two, to power the windlass to go sailing, so we have never run the engine solely to recharge the batteries. Yes, we keep cold fresh water jugs, to maximize the efficiency. Anything touching the holding plate, at ~26 degrees, is kept frozen. ~ ~ _/) ~ ~

Meredith Bond's picture

For our off-grid cabin, we bought a more basic model standard upright refrigerator/freezer (separate doors, freezer on top, no ice maker) - in the $450 range at the big orange box store. We have had no problems with our solar/battery/inverter running this unit, although I have minimized other loads in the cabin. The ironic twist comes that we have to empty out perishables from the FREEZER in the winter. As the only heat sources in the cabin are the antique cylinder stove in the lower level and the Rumford design fireplace in the "great room," there is no heat when the human beings are not present to tote firewood and stoke the fires. We designed all the plumbing to completely drain with a few valves, and "pink" the toilets and p-traps with RV antifreeze when we leave. At 8500ft elevation in the Colorado mountains, the "usual" temperature when we arrive in the winter is in the low 30F's (we have a couple of days every winter where the recorded temperature inside the cabin is well below 0F). This basic refrigerator runs its compressor based upon the temperature in the fresh food compartment - not the freezer. So, when the cabin is resting in the low 30's when we are not there, it may be days without running the compressor - and the freezer temperature will rise above freezing, thawing foods enough to compromise safety. While there are many potential solutions to this problem, for the near term we just pull out all the perishable frozen foods by about Halloween - serves as a good annual clean-out-the-freezer exercise. Our longer term solution involves adding some baseboard hot water (or glycol or oil) heat (propane in-line heat source), enough to keep the place above freezing when we are absent. P.S. - ever see what mayonaise does after freezing? The things we learn in our off grid adventures!

craigmerrow's picture

Something that I didn't see addressed in the article is that a full refrigerator is more efficient than an empty one. Being single, I don't keep a lot of food in the fridge, so I fill mine with water jugs for the thermal mass to take up the unused space. During the winter months, I have some extra ones that I keep outside, rotating the frozen ones into the fridge.

Michael Welch's picture
That's true, specially for non-chest fridges. Every time you open the door, cold air spills out the bottom of the fridge, sucking room air in at the top. Then when you close the door again, the fridge has to cool the new air. The more stuff you have in your fridge, the less air can spill out.

This also gives a big advantage to chest-type fridges, no air can spill out when you open the lid.
Marc Fontana's picture

Great article ! I don't live off-grid but I bought a new 22.1 cu-ft Maytag fridge with a bottom mounted freezer in 2012 because it had the lowest rated energy usage for its size - 404kWh/yr, it saves energy by monitoring the ice built-up on the evaporator and only defrosts when needed. Since then, I learned that in 2014, the U.S. EPA changed the energy test requirements for refrigerators and this has resulted the Energy Guide posting higher energy use numbers. The newer Energy Guides have Yellow text over black (previously it was the reverse). As a result, the energy guide cards now have different energy numbers posted on the black/Yellow EnergyGuide (US) side and on the white EnerGuide (Canada) side. It's confusing because the numbers can be quite different. For example, the model I own is still sold, but it now has a 584kWh/year in the U.S. but in Canada, it is rated 423 kWh/year - All this makes it very difficult to compare the energy ratings between older models and newer ones. If you want to compare different new models in the store, you can use the EnergyGuide, but I wouldn't trust the rating to give you an accurate energy consumption value.

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