Efficiency Impact of Adjusting Freezer Temperature

by Tim Fulton on October 7, 2009

This entry is part 2 of 2 in the series Freezer Efficiency

freezer

Last time, we talked about the efficiency impact of defrosting a freezer. Defrosting gave us around a 5% reduction in energy usage. This time, we will be seeing what reducing the freezer temperature can do for us.

freezer

The temperature adjustment for my freezer is on the front end of the left side of the freezer. You can see it in the first picture. As the freezer sat, the dial was set to 4 out of 7. At the end of our last article, this setting was using 1.15 kWh per day.

At setting number 4, the freezer stayed right around -15°F (-26°C) at the very bottom. People that are off the grid tend to keep their freezers around 0°F (-18C) to save energy yet not compromise the length of time food will keep in the freezer.

freezer

So, as you can probably imagine, I simply turned the freezer all the way down to the 1 setting. I was a bit afraid about the temperature increasing too much, but it really didn’t rise all that much. I took temperature readings after a few days and the freezer at the bottom was now around -12°F (-24°C) and roughly 0°F (-18°C) at the top. I was kind of surprised that it didn’t increase the temperature more than that. However, I was even more surprised when I saw that the freezer was now only using 1.06 kWh per day. That is a solid 8% decrease from the 1.15 kWh per day it had been using at the end of our last article. So, to date we have decreased the power consumption of the freezer by 12.5% from the original 1.21 kWh per day.

For as simple as this is to do, everyone should really take the 5 minutes to go to their freezer and just turn the dial down. Double checking the actual temperature a few days later is a good idea. If you get too far above 0°F (-18°C), you start to see a drop off in how long the food will stay good. Organizing commonly used food to the top and longer term storage food items to the bottom is a great idea if you want to start increasing temperatures further. However, it would be my guess that most freezers out there are probably running much colder than they need to be.

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Efficiency Impact of Defrosting a Chest Freezer

by Tim Fulton on September 16, 2009

This entry is part 1 of 2 in the series Freezer Efficiency

chest freezer
About a year ago when I bought my house, the previous owners offered the chest freezer that was downstairs for a reasonable price. We gladly accepted. Ever since, it has been chugging away eating up whatever amount of electricity it needs to keep itself cool. Only recently have I begun to examine it and look into what can be done to increase its efficiency. Throughout the next few weeks and months I’ll be doing what I can to get it running a bit more efficiently.

The first thing I noticed when we started using it was that it was obviously a manual defrost freezer. This was quite apparent from the 1-2 inches of ice/snow on the side of the freezer. This pleased me as I know manual defrost freezers are generally more efficient. However, at the time we moved in, it probably needed to be defrosted. Now, a year later, it really needed to be defrosted.

Before defrosting, I hooked up my Kill A Watt and monitored the energy consumption for just over 9 days. The readings came to 11.17 kWh over 222 hours. This translates to 1.21 kWh a day. With the baseline established for the freezer, I could go ahead and defrost it.

chest freezer

This was the delightful image you saw every time you opened up the freezer.  As you can see, there is a bit of build up on the inside.

chest freezer ice build up

As I started to remove the food to defrost the freezer, I figured I better measure how thick this stuff actually was. As it turns out, it was almost three inches thick!

chest freezer ice build up

With all the food out, you can see how much of the freezer wall was actually covered in ice. Thankfully, the amount of ice didn’t cover the entire inside wall.

After the freezer was defrosted and all the food was back in, I let it run for a few days to get back down to temperature. I then hooked the kill a watt back up to it and let it run for another 216 hours. This time around, it only used 10.41 kWh. A little math shows us that this is 1.15 kWh per day. So, the defrosting looks to have drop the energy usage roughly 5%.

This simple task will save a hair under 22 kWh a year or 1.83 kWh per month. I was honestly hoping for a bit more than that. But, I do have a few more things planned.

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