Using high-efficiency technology and making a few simple lifestyle changes can have a big impact on your daily energy use and make living off the grid much more feasible. One of the technology upgrades I’ve made that I’m happiest with is my home-modified high-efficiency refrigerator. This refrigerator has been my only refrigerator for 4 years and has performed perfectly with extremely low power consumption. In this article, I’ll describe my reasons for the switch and explain how to do the conversion so you can try it out for yourself.

My motivation to experiment with a new refrigeration strategy came from my experience with my old refrigerator. It was a fairly common style of upright fridge with a freezer section in the top third and consumed an outrageous total of 5-6kwh per day! The biggest flaw of the ordinary refrigerator is that the doors are located on the side. Proper design must take into account the fact that cold air is denser than the rest of the air in your home and will sink when it gets a chance. Well, the cold air in your fridge gets that chance every time you open the door. As you look inside to select your next meal, all the cool air rushes past your feet and is replaced by warmer air from your living space that now needs to cool down. Also, magnetic door seals, no matter how airtight they are when new, will inevitably develop blemishes and constantly allow cold air to leak in.

An efficient refrigerator design must begin with a well-insulated chest container. If you don’t want to build your own, you’re in luck because any chest freezer will work just fine. Cold air inside the unit will not leak because the door is located at the top. Also, every time you open the refrigerator to grab something to eat, the cold air will stay inside and you won’t need to re-chill it as soon as you close the door.

The obvious problem with using a chest freezer as a refrigerator is that its thermostat is set for too low a temperature range. To solve this problem, it is necessary to set up another circuit with a thermostat and a relay switch to ensure that the temperature is maintained at about 4 degrees Celsius. Basically, this circuit should turn on the freezer compressor when the temperature goes above 4 C and turn it off when the temperature drops below 4 C. The easiest option would be to find a refrigerant line voltage thermostat with a range of 0 – 10 C but I couldn’t find one so I had to use a regular heating thermostat with a range of about 0-30 C. If I set this heating thermostat to 4 C and plug it into my chest freezer it will turn on the freezer when the temperature dropped below 4 C and this would only make it colder or if the temperature was above 4 C the thermostat would never turn on the freezer! More research was needed to resolve this issue.

The solution I found was the SPDT relay switch. An SPDT relay uses the electromagnetic force of a coil to control a switch in another circuit and this relay allowed me to use a heating thermostat to properly control the freezer compressor. When the heating thermostat reads a temperature of 3 C it will close its circuit and this will allow current through the relay coil and will turn the switch to the off position. When the heating thermostat reads a temperature of 5C it will open its circuit and this will stop the current through the relay coil and close the other circuit thus turning on the freezer compressor.

To connect the wires to the new thermostat inside the refrigerator, I opened the drain plug in the bottom corner of the unit. The hole is taped shut on the inside. The relay switch is hidden between the wall and the refrigerator for now. I’ll build a nice circuit box for it at some point.

I can store all the same foods in this chest refrigerator, but the organization has changed because the door is on the top. I found two Rubbermaid containers that fit quite nicely in the large storage area. I stack one on top of the other and only pull the top one out when I want to get to things at the bottom. I thought this process might get annoying, but I’ve found that I rarely have to do this if I just put my long-term storage items in the bottom bin and all my everyday items in the top bin.

Since the main reason for this project was energy conservation, I must tell you about the performance of this chest refrigerator. I hooked my energy meter up to this unit for a few days and found it used around 200Wh per day on average. That’s only 2 cents a day of electricity and a big drop from my previous power sucking model that used 5-6 kwh a day. The most efficient refrigerators you can buy new today use about 1 kWh per day and this design uses only a fifth of that!

This difference in power consumption only means a few dollars a year on my power bill if you’re already connected to the grid, but if you’re considering buying solar panels to power your home technology, then this difference in power consumption means spending thousands of dollars less on solar panels so the simple switch to a walk-in refrigerator makes living off the grid much more viable.