Your refrigerator could be the largest consumer of electricity in your off the grid home. Selecting the right one for you is less about aesthetics and more about size versus power usage.
Less than two decades ago it made sense to purchase a propane refrigerator for two reasons:
- Solar electricity was prohibitively expensive
- AC power inverters were expensive, inefficient and most made a poor quality electricity such as the infamous modified sine wave.
There were many propane choices such as Danby, Servel and Dometic. Dometic was a common choice as they make smaller and rugged fridges designed for the RV and marine industries.
The downside of the propane fridge is the cost. They are expensive to purchase and operate. Expect to pay up to $2500 initially and $15 to $30 per month for the operation of your propane fridge. If you only use it for a few months in the summer, this extra cost is insignificant. However year round use is expensive and inconvenient.
As solar energy became a bit more affordable the DC fridge gained some traction. The common recommended DC refrigerators were the Sunfrost from Arcata California. These fridges are high end, 12 or 24 volt, and very efficient. When you added the 25% or so gained by not using a modified sine wave inverter, they were and are a good choice. The downside is they are made one at a time and are priced from $1500-$3000 and even higher. They must be crated and shipped by truck which can easily add another $500-$1000 to the total cost. If something were to go wrong like a compressor burning out, repairs are very difficult. No one stocks parts for these beautiful machines and no one seems to know how to repair them, although they don’t operate any differently than a 120 volt version. If you can afford one, we still highly recommend the Sunfrost refrigerators and freezers.
Now that solar is more affordable and inverters are much more efficient the “off the shelf” refrigerator is probably the best solution for most of us.
For the average off grid homestead, a good quality off the shelf fridge is the answer. You should be able to go to your local Sears or Home Depot and find a refrigerator/freezer that consumes about 1 kWh per day. That is definitely within the range a solar home can handle.
Types of Refrigerator Cooling Systems
Fridges are usually cooled by one of three methods:
- The condenser is a series of pipes or fins on the back of the fridge.
- The condenser is located on the rear or on the bottom of the fridge and it looks like a car radiator or car air conditioning condenser. This small radiator like device is cooled by a fan.
- There is no compressor. The fridge is cooled via a heating element that drives the cooling system via absorption.
We prefer the second type as there are options for making the fridge more efficient by adding some duct work to the outside or a cool area of your home. By doing this you can supply cold air to the condenser instead of the hot air surrounding the fridge.
The #3 type absorption fridge is never efficient. It is essentially an electric heating element that uses a lot of electricity. This type of refrigerator has been reserved for the RV and marine industry but now can be found in some hotels and conference centers. We are not sure why anyone would use one other than they are very quiet and have no moving mechanical parts.
If you find two fridges that are relatively the same as far as size and efficiency but are cooled by different methods as above, buy type number 2.
Choosing a Refrigerator (“Off the Shelf”) Considerations
The most efficient type of refrigerator is the fridge only model. These are quite rare and not likely what you will want, but they are still worth mentioning.
The most efficient fridge/freezer is the freezer on top. Cold air is heavy and falls from the freezer chamber to the fridge using no fan or pump. The bottom freezer model all use electricity to move the cold freezer air up to the fridge compartment. The side by side models are usually not that efficient either and are best avoided.
Ice makers consume too much electricity. Do not buy a fridge with an automatic ice maker. You can spend a few minutes a month filling the ice cube tray.
Do not buy a fridge with auto defrost. These refrigerators use a timer and electrical heating elements that consume a huge amount of electricity every so many days. This can add many kWhs per year of operating electricity. The second problem with auto defrost is the timers/computers can be confused by generators or poor quality sine waves making the auto defrost cycle happen more than normal.
Do not use a new fridge with a modified sine wave inverter. Today’s refrigerators use fancy electronics and computers for temperature regulation. It is not uncommon for a new fridge to be completely destroyed in a short time by a poor quality sine wave.
Only purchase the size of fridge that you NEED. An 18 cubic foot or so should be plenty for the average family of 5 or 6. A large fridge with empty space will waste energy.
Do not purchase a fridge with condensation control or anti sweat system. As refrigerator manufacturers have realized that condensation on the outside of a fridge might bother a consumer they have added heating elements to prevent it. Rather than insulating the refrigerator better, (which would eliminate condensation) they add electric elements on the outside panels of the doors and sides. These elements operate 24 hours per day or just when they sense humidity. This is not what you want if you are trying to save energy. If you get stuck with this type of fridge turn it off via the “energy saving switch” or cut the wires.
How to Purchase the Most Efficient Refrigerator?
It might seem too easy but the best way to buy an efficient fridge is by locating one without all the bells and whistles and looking at the “Energy Guide” label or documentation.
We are not talking about Energy Star or some other sort of bogus certification.
Simply look at the label that states how many kWh per year the fridge will use. You should be able to find an 18 to 20 cubic foot unit with an energy consumption of under 365 kWh per year. If you keep to this standard you will be able to operate your fridge with about 1000 watts of solar modules, even in the worst of climates.