Poor Man's Efficient Refrigerator
In years past, almost all conventional refrigerators and freezers were so inefficient as to render them useless to folks living off the grid. This meant the only options were rather expensive DC units (such as Sunfrost). While these models are super efficient and work very well, it just wasn't much of an option for someone on a tight budget.
So we found a great low cost AND super efficient option. I think you’ll love it if you’re pinching pennies while going off the grid!
Conventional AC vs Specialty DC
Thanks to the current interest in energy efficiency and the energy star program, conventional 'fridges and freezers are now a feasible option for off grid users, and at a much more affordable price. The main drawbacks would be:
- The minor energy loss from an AC unit running off the inverter (as opposed to a DC unit running straight off the batteries)
- The fact that they still are not as efficient as the specialty DC units.
As mentioned earlier, while specialty DC refrigerators and freezers are wonderful options and are super energy efficient, they are also fabulously expensive (a Sun Frost can cost $2,500 to more than $3,000).
Being on a limited budget, we had to find an off grid refrigeration option that was cheaper but yet super efficient.
Mission impossible? Maybe not…
Converting a Freezer To A 'Fridge
Since we already had an older efficient AC chest freezer, I decided to convert it into a ‘fridge using an external thermostat that turns off the power to the freezer once the temperature probe reaches the temperature set point. We use this analog external thermostat but there are also good reviews for this digital one too (those are affiliate links which help support our site at no extra cost to you).
Why convert a chest freezer into a ‘fridge?
There are a couple reasons why I chose to do this:
- Freezers are more heavily insulated than refrigerators (due to colder temperatures inside), so when a freezer is converted, it is more efficient.
- Cold air is more dense and naturally falls to the lowest area. When you open the door of an upright unit, cold air is lost. When opening a chest model, there is nowhere for the cold air to escape to, and much less is lost.
How Much Power Savings?
Our 7.3 cu. ft. Vestfrost, which unfortunately is no longer made, claims an average annual usage of 197 to 279 kWh per year when being used as a…ummm…freezer :-). That breaks down to around 530 to 760 watt-hours per day. When used as a refrigerator, we have found ours to use less than 200 watt-hours per day on an average spring or fall day! That may sound like Greek to you right now, but I am giving these numbers so you can use them for comparison with other refrigerators.
When searching for a conventional ‘fridge, the yellow energy tag on the unit will give an estimate of the annual energy consumption. You can then divide that by 365 to find out how many kilowatt hours (kWh) it uses per day (roughly). Multiply that number by 1,000 to arrive at the watt-hour usage per day. That is a figure you can compare with some of the very efficient and expensive DC models.
For instance, a Sunfrost R-19 uses around 500 watt-hours per day. Yes, it is larger than our freezer/’fridge, but I have lived with an R-19 and can tell you that it doesn’t have a huge amount of extra usable space. Comparing that with our freezer/fridge conversion, we find that ours actually uses significantly less power! No, our chest model is not as convenient as an upright model, but when you need efficiency and don’t have a large budget, that’s a minor inconvenience that is livable. Bear in mind that each chest freezer is different and you’ll have to convert yours and measure it before knowing how much power it uses.
The Impact of Room Temperature
Needing to squeeze even more energy efficiency out of your ‘fridge or freezer? At our previous home, we kept our converted refrigerator in a room that was attached to the house but was unheated. It gets enough heat from the house to not freeze up but stays much cooler than the rest of the house. During the winter (when our solar system was not producing as much power) the ‘fridge didn’t have to work nearly as hard and used much less power. What an easy hack!
At our current home we do have the refrigerator inside for convenience, but we placed our freezer out in the garage to take advantage of our cold winters and use less power. Since we don’t access the freezer very frequently, it isn’t difficult at all.
If using a ‘fridge or freezer in a cold environment, be aware that some units may be adversely affected. For instance, a fridge MUST be kept above freezing (obviously!) so that your food doesn’t freeze. With a ‘fridge/freezer combo, be aware that most of the time there is only one compressor for the entire unit, and if the room temperature is cool enough to not trigger the refrigerator thermostat, the compressor will likely not run at all, and your freezer will gradually thaw out (if room temp is still above freezing) or will not be freezing as deeply as you expect (if room temp is below freezing).
And in the case of our chest freezer in the garage, we shopped for a model that specifically stated that it could operate in any cold temperatures. Some of them state that room temperature must be above 20°F, some of them need to be above 32°F and others even state that room temperature must be above 50°F! So look the manual over carefully before purchasing.