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We have a community Pea Patch that has 2 older refrigerators that are empty 5 days a week and used to store produce on 2 of those days. Does it take less energy to leave them running for those 5 days, and is it better for the refrigerator, than to uplug it for that time? I think they should be unplugged, but the person in charge doesn't.

If we were to fill them with jugs of water on the empty days, it would need to be re-cooled after the two days of use.

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The jugs of water trick is for when you're going to be opening the fridge alot -- so you have thermal mass and less air that exchanges each time you open the door. –  Joe Jun 17 at 21:58
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You can use a kill-a-watt to measure the energy consumption for one week with each strategy. –  RedGrittyBrick Jun 17 at 23:02

3 Answers 3

It's probably a false economy to turn it off and you run the risk of having them develop a smell unless you take these precautions.

If you do turn them off you need to open the door and wipe it out with some chlorine bleach to prevent any mold developing. Opening the door allows it to dry out again helping to prevent mold. If you have a holiday home that lies vacant for several months, yes turn off the fridge assuming it's empty and there are no frozen items in the freezer section that you want to keep.

In your case, I'd leave it. Running a fridge for 5 days when the door is never opened will not cost you that much at all. However, having a fridge develop a smell you can't eliminate will cost you a new fridge.

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I think unplugging the refrigerators will both save electricity and reduce wear on the compressors, although I agree with others that if possible you should measure the usage, in part to decide whether any (possibly small) savings is worth the effort.

Energy Savings

Empty refrigerators are less efficient, since the compressor needs to cycle on and off more frequently due to relatively low thermal mass. If you unplugged the fridge when you weren't using it, I suspect when you plugged it back in it would only take a few hours to cool down. Under normal usage a fridge will have its compressor running about 1/3 of the time, so this will be a meaningful savings. (The fridge uses the vast majority of its electricity running the compressor, so how long it's running for is a good proxy for electricity consumption.)

Wear on Refrigerator

Cycling of the fridge compressor on and off is a primary cause of wear, so unplugging the fridge should be a benefit in that respect. Plus there will be total fewer runtime hours. I don't see how unplugging the fridge for days at a time could possibly damage it. (If you were unplugging it twice a day and forcing it to warm up to room temperature and the cool down, that would be another story.)

Other Considerations

  • When the fridges are off you will need to make sure they don't get moldy or develop smells. The easiest thing would be to leave the doors open so any moisture can evaporate. Leaving a dry hand towel over the door can help ensure the door doesn't close accidentally.
  • If you have the means to measure the electricity savings, I would do so. You may find that the savings are small and not worth the effort.
  • Water jugs will not help you if you are unplugging the fridge, in fact they will make it worse. The purpose of the water is to retain cold and stabilize the temperature. If you let the water warm up to room temperature with the rest of the fridge you will just be creating more work for the compressor when you plug it back in. On the other hand, if you decide to keep the keep the fridge plugged in all the time, leaving jugs might help a bit (but only if you leave them in all the time... do not remove them).
  • Do you really need two fridges at all? Maybe a cooler and some cold packs could supplement any overflow those 2 days/week?
  • Old fridges can be big power hogs. I'm sure you could save a lot of electricity with a new model (maybe a single bigger one). Whether a new fridge could pay for itself in a reasonable amount of time depends on a number of factors, but it might be something to consider.
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This is hard to tell and may largely be determined by your refrigerators. Energy Star came into existence around 1992 I believe, so if your fridges are older than that they are probably energy leeches regardless of leaving them plugged in or not. This article claims a fridge left unplugged overnight would not net significant energy savings. This comes to 1/3 time unplugged over the course of a week. Your situation, with 5/7 time unplugged over a week, is just over double the 1/3 time unplugged per week. This may save some energy, but with much older fridges, they will strain to cool down again and you could put a lot of stress on the compressor and use a ton of energy to recool the unit. Maybe it will save some energy, but maybe it will blow out your fridge.

Perhaps a month long experiment is in order. Try your fridge unplugged hypothesis for a month with all other energy usage remaining the same. At the end of the month, compare energy costs with the last month and see if the savings are significant and use this as a guide for the future.

Also, check out the energy saving tips on this page to help cut down on waste. For example, leaving it on the highest temperature settings while not in use can help cut down on energy consumption.

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And, of course, the highest temperature setting is OFF –  User58220 Jun 17 at 23:53

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