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I am a student who studies in a different city than my home so I go home almost every weekend or second weekend. I recently brought a room sized fridge and to save electricity costs, whenever I go home, I turn off the fridge which is usually for two-three days and in case of extra vacations, more. Recently somebody told me that that isn't healthy for the fridge and the compressor will get inefficient if you keep doing this so you should just keep it on. Now my question is, if I turn it off for 2-4 days, will the compressor or fridge in any capacity be messed up? Or work less efficient? Or will there be any issue?

Thanks in advance.

  • 8
    Do you empty the fridge of perishable food when you leave it off? – Jim Stewart Jun 19 at 12:25
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    Check your fridge's energy rating or look it up with EnergyStar to get an idea of the power cost. You may be surprised at how low it is. I have a small fridge in my basement, I just looked it up. The estimated cost to run it is $27 per year. Turning it off for a day or two once a week may only save you a few dollars a year. – dwizum Jun 19 at 20:17
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    @dwizum It may not save you anything. Consider: the cost to keep it at a low temperature versus the cost of cooling it back down from room temperature, which implies a lot of continuous running. – user207421 Jun 20 at 1:09
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    I read room sized fridge, you mean full sized? I... can't imagine you needed a fridge the size of a room... – Nelson Jun 20 at 2:42
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    @Nelson I had the same initial reaction to "room sized fridge" but figured OP meant dorm room sized, aka mini-fridge or beer fridge. Khawajayy, can you clarify? – A C Jun 20 at 3:01

11 Answers 11

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Someone will close the door and...


It will fill the fridge's internal spaces with mold

Air holds moisture. Warm air is capable of holding more moisture than cold air. Everytime you open the fridge door, you let in room air. This contains more moisture than air can possibly hold at refrigerator temperatures, which means condensation occurs inside the fridge. When it occurs on the coils, it is visible as frost.

Those panels that line the fridge interior are not airtight. Air also circulates behind them and condenses there.

The upshot is, a fridge has a lot of water or ice inside it, in all sorts of inaccessible nooks and crannies. When you shut off, the interior warms to room temperature, a sealed space with more condensed water than the air can possibly hold. It hits 100% humidity and you have a petri dish for mold.

The only cure is to leave the door open enough that air circulates freely, which keeps the humidity same as ambient. However, this doesn't work. Humans have embedded programming to close any refrigerator door on sight. The entire species has 18 years of full-immersion psychological conditioning starting nearly from birth to close refrigerator doors.

Why the mold is bad

I learned this by repeatedly cleaning mold off a fridge we ran when needed. It seems a simple fix; clean off the surfaces and you're all good. However, those are not the only surfaces. There is also the backside of those surfaces, the machinery including evaporator coil, and electricals. You cannot reach those to clean them. And to be clear, the interior lining of fridges are decorative, not hermetic seals.

Exactly the same black mess is happening in the inaccessible locations, in roughly same proportion, since the humid air is convecting all over the fridge. If it happens repeatedly, the mold gets thicker since you're not cleaning it.

Obviously that can affect machinery, but this reserve of mold spores can also get on food.

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    +1 I was going to write something similar (though not quite as detailed) but you beat me to it. The other point I was going to add is that a refrigerator can take many hours (manuals typically say "24 hours" but I suspect that is boilerplate copied for the last 50 years) to cool down. They take a long time because the compressor/etc. are designed "just barely big enough" to keep the price down (and enhance manufacturer profits). So when you turn it on & put in the milk you just bought, it will spoil quickly because of the delay cooling down, negating the small electricity savings. – manassehkatz Jun 19 at 14:16
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    @DaveInCaz Generally, camper/RV fridges aren't designed to avoid the listed problems. Like almost any fridge/freezer, RV fridges take time to cool down to operating temperature or dry out after being turned off. It's desirable to turn one on considerably before wanting to use it and to leave the door(s) propped open (i.e. unable to be closed) for an extended time after turning it off to prevent mold (and wipe the inside down after any ice melts to help dry it out). Any refrigerator/freezer will accumulate dirt/dust/particles during normal use, which mold can use for food. – Makyen Jun 19 at 22:39
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    I usually hang a towel over the open fridge door to indicate that it is to be left open. If that does not work, a notice or sign might. – Andrew Savinykh Jun 20 at 0:22
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    As often as I have seen refrigerators left open, I question that “embedded programming” thing. But it doesn’t matter if no one is there to see it and close it, which seems to be the situation OP is in. – WGroleau Jun 20 at 5:50
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    @manassehkatz: "Just barely big enough" compressor is not about cutting corners to save money. You always want a compressor that's just barely big enough for the cooling task at hand, because otherwise it will run with a very very short duty cycle and will not remove any significant amount of moisture before the desired temperature is reached. Yielding, once again, mold. – R.. Jun 21 at 4:56
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You're probably not saving any meaningful amount of electricity by turning it off for just 2-3 days. Sure, it won't use any for those days, but the temperature inside will raise to room temperature. After you turn it on again, it will have to work for many hours to cool down again. This could cause abnormal wear on the compressor, because it's designed to be frequently turned on and off by the thermostat just to keep the temp level, and not to work for several hours in a row to cool the whole thing down from room temp. However, this effect is probably insignificant.

By not opening the door when you're gone, you're already saving electricity. The most work the fridge has to do is to cool down all the warm products you put in and all the warm air you let in. If you're not there to open it, it's a bit electricity saved already.

The most significant part had already been covered in other answers: turning a fridge off is a multi-hour effort that involves removing food, having the frost thaw and cleaning up resulting water. Turning it on again is also non-trivial, as it requires drying it thoroughly to prevent immediate frosting. Thawing and refreezing without all this effort will damage the fridge, through mold and ice damage. The whole cleaning is well worth it when you leave for few months, but not for few days.

If you want to optimize the fridge, make sure that the hot part (usually at the back or built into the sides) has room and unobstructed airflow. Small fridges are convenient to be stuffed in cramped spaces, like under desks. Simmering in a pocket of hot air greatly increases power consumption. Observe when the compressor is running and after a while (eg when it stops) use your hand to check if the air around the element feels warm (not the element itself, it's supposed to be very warm to touch). It should not: all the air warmed up by fridge should convect away freely. In a nice, cool environment, the fridge has much less work to do. Less work = less electricity.

You can observe how often and for how long does the compressor turn on when the fridge is not opened. It should barely work at all. If the compressor is on most of the time, then it means that the insulation or seals are damaged and the best course of action is to either repair the seals or get a new fridge.

The rule of thumb that one should follow in all areas of life is to first measure the actual costs before trying to cut them. In programming we call it "premature optimization". The problem with it is that it yields insignificant savings while detracting your attention from areas that actually need improvement. Get a kill-a-watt to measure how much running the fridge actually costs you. If the fridge is very old and leaky, you could find out that moving towards more expensive non-perishable food can be financed by ditching the worn-out electricity hog entirely.

I hope your fridge has an actual compressor. Peltier-baser solid-state portable fridges are ridiculously inefficient and IMHO not worth using at all.

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    "The rule of thumb that one should follow in all areas of life is to first measure the actual costs before trying to cut them." Excellent! Put that at the top! – FreeMan Jun 21 at 15:09
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A fridge keeps a steady temperature by turning the compressor on and off. The only difference is that you exchange a few on/off cycles with one longer on-cycle when you get back. I would say that does not negatively affect fridge lifetime, and might even improve lifetime because the total on-time is reduced as well as the number of cycles.

The only thing I can recommend from experience is that you should always leave the fridge open when you turn it off. Leaving it closed will lead to mould formation.

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    For a REALLLLLLLLLLLLY old fridge, one might argue that a warm compressor wont seize like a cold one would. They'd probably be right, but besides this (*which is silly), @Sanchises answer makes all the sense in the world. A fridge that is off (and modern) shouldn't be hurt by not running. You might want to consider turning its temp down (or up to be precise), so that it spends less energy keeping cool and then you can leave things in it that dont spoil at cooler (vs colder) temps. Then you can enjoy a cold beer that much faster when you come back. – noybman Jun 20 at 1:29
  • and ... If it's a kerosene fridge it won't have a compressor at all. – mckenzm Jun 20 at 5:33
  • @statueuphemism The best voted answer have a point that there might be no savings (although I would argue it probably does) - and it might be a point that people feel easier voting on. – Sanchises Jun 23 at 18:57
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It's hard on the compressor because a fridge is designed to have a few number of room temperature to preset temperature cool-downs but it will maintain that temperature for several years. When it has to do this major cool-down, it runs constantly for several hours until the air inside is at the preset temperature. It would shorten the lifespan of the fridge, and it's not really saving you any money.

Sometimes those things we think are saving us a little money will cost us big money in the end.

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Turning off the fridge for 2 or 3 days every week or two weeks is not normally done and could have unexpected consequences, but even a small fridge generates some heat which would raise the temperature of the room if the room is not ventilated or even air conditioned. Presumably the room a/c is not on when you are gone, or is it?

All things considered I would leave the refrigerator on when you are gone.

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You need to open the door when you turn off the fridge. This means all the air and fridge parts that are normally cooled warm up to ambient temperature. Then when you turn if back on, all of that needs to be cooled down again. So there is a fixed extra cost to turning it off. While running on the other hand it only needs to get the warmth that creeps in through the insulation out again. So the larger and better insulated it is, the less you should turn it off.

It's unclear in the question, but if it's a mini fridge suitable for a dorm room, then likely it's small and not well insulated, so maybe it pays off to shut it off for 2 days or more. On the other hand if it's a standard full sized fridge, then it's very unlikely to pay off. If it's really a room sized fridge, you can be very sure it won't pay off.

The only way to know for sure, for your fridge and the spot where you installed it (that matters) is to use a cheap power meter and compare. They are like $20 you need to compare your power bill first to decide whether that's worth it.

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In addition to the other answers already posted, you may want to use a thermal mass (e.g. bottles of water) to take up the space in the refrigerator not used by perishable goods that you actually want there.

When you open the door during normal use (or someone opens the door while you're gone), the chilled part of the fridge exchanges relatively quickly with warmer room air, and the fridge is closer to the starting-over point than it would be if there were bottles of cold water in there. This also applies to the air that leaks in/out due to imperfections in the seals around the door etc.

If you regularly fill up the fridge right when you come back, this may not be worth it, as the fridge does have to do more work to cool down the bottle of water than just air. However, if you are regularly under-utilizing the space capacity and want to do something easy to improve efficiency, there's an idea. It also helps (slightly) with preparedness for water service outages.

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I should also check the manual that came with your fridge. I recently purchased a fridge and it comes with a 'vacation' mode. This essentially tells the fridge that you've taken anything really perishable out and it can go into an 'energy saver' mode and not have to keep everything quite as cold as it otherwise would.

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If it is a an energy efficient refrigerator ,I was told by an appliance repair man that there are issues with some getting them to restart after being disconnected.

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    Perhaps when they are disconnected and moved... At least I have had a couple fail like that... – Solar Mike Jun 21 at 11:13
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The maximum electrical and mechanical stress on the compressor occurs when it switches on. The motor has a current spike until it starts moving and the compressor has to work hard to bring the system up to pressure.

Eliminating a few days worth of start cycles will not damage the compressor as long as the fridge is not tipped or moved immediately before restarting. This can cause a liquid lock in the gas part of the system which can damage the compressor.

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It may be damaging your food (fridge take about 4h to go from 22° to 4°, more if being filled with room temp. stuff), also a fridge need relatively more energy to go cold from ambient temperature than to stay cold once cool.

If you have an 'average' empty fridge you could improve energy efficiency and also temperature 'constantness' filling the space you don't use with bottle of beverages, once cooled bottles will keep the cold in, if fridge is empty, cold air will escape as you open the door and the compressor will have to cool all the air every time you open the door.

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