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.

High-Efficiency Upright Refrigerator/Freezers

If having high efficiency in a standard format (i.e., upright fridge/freezer) is your priority, high-efficiency uprights come in both DC (12, 24, or 48 V) and 120 VAC versions. They feature efficient compressors, thick insulation, tight door seals, clever ways of removing condensation from the interior using natural ventilation—without running heating elements—and more. Even blank door and side panels are available so you can customize them to your décor. 

Expect to pay between $3,000 and $4,000 for a full-size, 19-cubic-foot two-door fridge/freezer. The DC versions are a bit more efficient, as they won’t have inverter losses. One advantage of a DC refrigerator compared to an AC one is that an inverter doesn’t have to be sized to handle the compressor motor startup surge—see the “Powering an Off-Grid Electric Fridge” section. Another advantage is, if the inverter fails (for example, from a nearby lightning strike), you still have refrigeration.

Going DC requires a DC circuit in your kitchen, which is likely not already wired. Either way, these appliances are an investment that will serve you well for at least a couple of  decades. The downside, in addition to the price, is that you’ll need to order these units and have them shipped and, unless you can find a local dealer, you won’t be able to inspect the product until it’s paid for and at your doorstep.

Are these specialty units really worth the extra cost, with conventional models available from the local big box store? It depends on both your situation and your budget.

Manufacturers: Northern, Nova Kool, SunDanzer, and Unique

Chest-Type Freezers & Refrigerators

If you’re looking for the highest efficiency, have plenty of floor space, and don’t mind some access inconveniences, chest-type freezers and refrigerators are a great match. These appliances capitalize on dense, cold air settling to the lowest point—unlike an upright model, in which cold air spills out the bottom every time you open the door and is replaced by room-temperature air. Combined with thick insulation, chest refrigerators are excellent, efficient choices, and at a much more reasonable cost ($1,000 to $1,500) than specialty vertical models.

Chest refrigerators have a couple of downsides. You’ll have to practice loading them so that frequently used items are readily accessible, though they come with wire baskets to help you stay organized. And, they don’t come in combination fridge/freezer models—you’ll need to buy separate units. I’ve seen some innovative kitchen solutions to this issue with the chest refrigerator on a sturdy shelving unit in easy reach, with the freezer on a heavy-duty slide-out shelf underneath it. Others may put them side-by-side, with handy shelving or wall cabinets above. Your creativity and adaptability will be key to living well with a chest refrigerator and freezer solution.

So how much room will you need? A conventional 20.1-cubic-foot refrigerator/freezer combo, for example, allocates about three-fourths of this capacity (15 cubic feet) to fresh-food storage and the remainder (5 cubic feet) to freezer space. At about 8 cubic feet, SunDanzer’s chest refrigerator offers about half of the capacity of a conventional refrigerator.

Manufacturers: Dometic, Nova Kool, Phocos, SunDanzer, Steca, and Unique

Conventional Fridges

Many U.S.-sold appliances have caught up with European ones in energy efficiency. You can now choose from a wide selection of refrigerator/freezer models, sizes, and colors, and base your decision on those factors plus the Energy Star rating and yellow EnergyGuide sticker. That’s what I did.

I didn’t want to spend money on a specialty off-grid fridge, was leery of tackling making my own built-ins, and didn’t have the kitchen space for a chest fridge and freezer, so I shopped by size, estimated kWh usage, and color. The model I chose offers 19 cubic feet of capacity, uses about 350 kWh per year (just under 1 kWh per day), and cost about $800, delivered. Once we finally learned to get along power-wise and energy-wise (see “Off-Grid Fridge Vagaries”), I was satisfied with the investment.

Be aware! When used off the grid, refrigerator “features” that no city dweller would do without can cause excessive energy use and unexpected problems. Here are a few things to look out for when selecting a standard electric refrigerator for off-grid use:

Top freezer, bottom freezer, or side-by-side configuration? Top freezers are the most efficient, as warm air rises while cold air sinks. Bottom freezers need a fan to make this heat exchange, but tub-style bottom freezers hold cold air better than door-style top freezers. Side-by-side freezer/fridge models are the least efficient, spilling more cold air from both compartments whenever opened. These should be avoided.

Ice makers. These cost you about 10% to 15% in increased energy usage as they have electric valves, actuator motors and, possibly, heating elements, to make sure the ice cubes fall cleanly into the bin. They also require a pressurized cold-water connection. I was willing to sacrifice that extra energy usage for the convenience, but you may not be able to. Refrigerator/freezers without ice makers (or in-door cold water dispensers for that matter) may be less expensive, but may have to be special ordered.

An automatic defrost cycle runs heating elements for an hour or so every few days to prevent ice crystal buildup. This is essential for the fridge’s proper function, but can often turn on when a battery bank’s state of charge is low. Time to run the generator for a couple of hours! In older refrigerators, it was possible to simply disconnect the heating element wires and defrost manually when needed, or install a switch so the defrost cycle could be turned on when it was warranted. In newer computer-controlled models, this can cause error codes that shut the entire defrost system down. In my case, I was again willing to expend the extra electrical energy for the convenience but had to sort out the bugs in the system first. It can be difficult to find full-size refrigerators that don’t have the automatic defrost feature—without it, unless you regularly defrost manually, the ice buildup can cause the fridge’s efficiency to plummet more than the efficiency losses from the defrost cycle itself.

Anti-sweat condensation control systems also use heating elements to keep moisture from condensing on the outside of the refrigerator in warm, humid climates. They should be avoided in any off-grid power system.

Powering an Off-Grid Electric Fridge

Continuous and surge load. The yellow EnergyGuide sticker will give you an idea of how many kWh the fridge will use  annually. You can extrapolate its daily energy requirements by dividing by 365. For example, an EnergyGuide sticker on a conventional fridge/freezer estimates 404 kWh per year—divided by 365, that’s 1.1 kWh/day.

The appliance’s nameplate rating (usually located inside the main compartment, next to the model and serial numbers) will tell you the maximum wattage it can draw. This includes when the defrost cycle and ice maker are running—but most of the time, it will be far less. A typical compressor load for a full-size fridge would be about 150 watts from the compressor, and 350 watts during defrost. Don’t assume that a smaller refrigerator will have lower continuous or surge ratings, either—dorm-sized models can draw as much as full-size ones. Always refer to the nameplate and EnergyGuide ratings.

When starting up, the compressor surge load will be significantly higher—often well over 1,000 watts (see sidebar), so make sure your inverter can handle it. Unfortunately, you won’t find surge load information from the refrigerator’s nameplate or in the spec sheet, so a bit of guesswork is involved. It’s possible to add a “hard-start capacitor,” which lowers the surge to the compressor, but many modern, efficient refrigerators already have one—adding another can damage the compressor.

Inverter waveform. Many modern refrigerators won’t run properly on a modified square wave inverter, with possible problems ranging from the internal controls not functioning properly (disabling the auto defrost cycle and the ice maker) to a drastic shortening of the compressor lifespan.

Non-Electric Refrigeration

Propane refrigerators use heat to generate cooling, without electricity. Propane (and even kerosene) refrigerators have been around since the early 1930s, using an absorption cooling system developed by Michael Faraday in 1824. The advantages of a common fuel source and quiet, reliable operation were huge for rural areas that had not yet been electrified, and still relied upon iceboxes and ice deliveries.

Propane refrigeration has downsides, though. Besides being a nonrenewable fossil fuel requiring drilling, refining, and transport (i.e., pollution, pollution, and pollution), propane’s price can fluctuate wildly and you may be subject to annual tank-rental fees and propane delivery charges.

With propane units, such amenities as automatic ice makers, water dispensers, and automatic defrost cycles are rare or unavailable. From the moment you first light the pilot flame, ice starts forming on the interior condenser plates. As it builds up into a miniature glacier and starts creeping ominously, it’s also impacting cooling efficiency and increasing your propane use. The only way to make the glacier recede is to remove the food (to some place that will keep it cold), fill pots and pans with hot water, and close them inside. As the water cools, this process is repeated—usually all day. You may have to do this two to three times a year, depending upon the humidity and how often you open the door. Some modern propane refrigerators have a defrost setting that bypasses the cooling system and sends burner heat directly to the compartment plates, but this still makes for a long defrosting process.

Don’t even think about jabbing at the condensers with a screwdriver or other tools to knock the ice loose—you are likely to puncture the coils, thereby ruining the fridge or freezer. You can use an electric  hair dryer and complete the task in couple of hours. But if you are off-grid and can’t spare the hair dryer’s 1,500 W, it’s hot water for you. Watch your toes.

Small rural gas cooperatives may deliver to your off-grid location—and also disclose their prices. I recently switched to a rural company after years buying fuel from one of the biggest national propane corporations. The corporate rate was $3.76 a gallon. The cooperative charges $1.79 a gallon, delivering to exactly the same location.

Portable propane tanks are an option, but you’ll be doing a lot of work swapping out tanks, even with an automatic tank-switching device. A full-size (19 cubic feet) propane fridge/freezer will burn through 1.5 to 2 pounds (0.36 to 0.47 gallons) per day, and possibly more depending on your ambient indoor temperature.

Three-way propane refrigerators, which can use propane, 120 VAC, or 12 VDC, are common in RVs, come in compact sizes, and may seem like a flexible off-grid option.  Some can automatically switch between the energy sources depending on what’s available. But don’t be fooled—these units work fine with propane, but are all very inefficient when used electrically. They do not have high-efficiency compressors and instead use an electric heating element in lieu of the propane flame. They are intended for use in an RV or boat with a 120 VAC shore power connection, or for short periods of time on 12 VDC until you can go to town and get your propane tank refilled. 

With all that said, propane refrigeration can still be an excellent option—and sometimes the only option—for homes, cabins, and RVs with smaller (or non-existent) off-grid power systems. If a home doesn’t already have a large PV system and battery bank, installing all that equipment just to have electric refrigeration may not make much sense.

Web Extras

Rebates for energy-efficient appliances • dsireusa.org

Energy Star rebate-finder • energystar.gov

Enervee • enervee.com

“Off-Grid Appliances—Ultra-Efficiency Required” by Ian Woofenden in HP140 homepower.com/140.106

“Converting a Chest Freezer to a Refrigerator” from Build-It-Solar • bit.ly/FreezerConvert

American Council for an Energy-Efficient Economy • aceee.org

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Comments (10)

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.

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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