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The FDA recommends a freezer temperature of 0˚F (-18˚C). Warmer temperatures risk bacterial growth and quality problems. But what are the reasons not to set the freezer colder? My Bosch freezer can be set as low as -8˚F (-22˚C).

The only downsides I can see are increased electricity usage, increased thaw times during food preparation, and more wear on the freezer compressor. But advantages include colder ice cubes and faster freeze times for new items. Are there any other reasons not to set my freezer to the coldest setting?

Doug
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  • *faster freeze times* - how do you define "freeze"? – Caius Jard Sep 21 '21 at 15:11
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    I would like to see empirical evidence surrounding this. I always set my freezers to their coldest setting on the assumption that colder=longer storage, but I have nothing to support this position. Interesting question! – James Geddes Sep 21 '21 at 15:19
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    @CaiusJard How do *you* define it? Colder freezer means heat loss from food will be faster, means food freezes faster (albeit not much faster) – SiHa Sep 21 '21 at 15:27
  • @JamesGeddes when it comes to chemical processes colder it is slower they are. So in principle you are right. – Alchimista Sep 21 '21 at 17:31
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    Another consideration is this: refrigerators are often cooled by blowing cold air from the freezer into the fridge. If the freezer is too cold, the drafting air will freeze some things on the top shelf – AdamO Sep 21 '21 at 20:04
  • @AdamO I could be wrong, but I assumed OP was talking about freezers only, not the freezer section of a refrigerator. – Glen Yates Sep 22 '21 at 14:47
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    Get it too cold (or too pressurized), and you'll see phase changes between the different crystalline forms of ice! Okay, I'll go back to the chemistry SE now. – neph Sep 23 '21 at 20:00
  • Side note, you appear to be using the masculine ordinal `º`, \u00BA instead of the degree symbol `°` \u00B0. Pedantic, but it looks especially odd in the underlined link where it more or less looks like it's double-underlined. – Doktor J Oct 05 '21 at 21:22
  • Is your freezer part of a fridge/freezer combo, or is it a separate deep freeze? That changes some of the dynamic referenced in the answers. – PoloHoleSet Oct 06 '21 at 13:10
  • @PoloHoleSet I actually only have a fridge/freezer combo, but the considerations for dedicated freezers are interesting too. Sounds like the main combo consideration was a too-cold freezer causing things in the refrigerator to freeze. Fortunately I haven't experienced that with my unit, even with very cold freezer temps. – Doug Oct 06 '21 at 18:26
  • @Doug - I use my dedicated deep freeze for storage, so any frozen treats or ice cream get moved to the fridge/freezer, as opposed to getting it directly from the deep freeze. – PoloHoleSet Oct 13 '21 at 13:02

5 Answers5

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One possible consideration is that some frozen desserts (most notably ice creams and sorbets) can be very difficult to scoop if your freezer is too cold. Optimal serving temperature for ice cream is between about 5 & 10°F (-15°C & -12°C); colder freezers may result in difficult scooping and/or needing to leave the ice cream out to thaw.

The proposed advantage of "colder ice cubes" is relatively small, because the vast majority of heat absorption by ice (in a drink, say) is due to it thawing. To put some numbers on it, every gram of frozen ice absorbs about 2.1 joules of heat energy when it warms up by 1°C. In contrast, that same gram of ice absorbs 335 joules of heat energy when it thaws into liquid water. If you run the numbers, this means that ice at -22°C will only absorb 2-3% more heat from your drinks than ice at -18°C.

Michael Seifert
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  • @Michael your second paragraph also explains why "reusable" ice cubes made from plastic or stone ("[whiskey stones](https://cooking.stackexchange.com/a/116440/51242)") don't really work. – henning Sep 23 '21 at 08:56
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    @henning: There are some varieties of "reusable" ice cubes that actually have a freezable liquid sealed inside them (like [these ones](https://www.amazon.com/60-Pack-Reusable-Plastic-Squares-Assorted/dp/B07MG7PSHJ/).) They actually do work moderately well. But yes, if it's just solid stone or steel or plastic, you don't get the magic of latent heat working for you. – Michael Seifert Sep 23 '21 at 11:13
  • Where did you get the 2.1 J/g/degC value? When I was at school in the 1970's the specific heat of water was 4.2 J/g/degC – uɐɪ Sep 24 '21 at 07:36
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    @uɐɪ: You're remembering the specific heat of liquid water. The specific heat of ice is different, it turns out. – Michael Seifert Sep 24 '21 at 10:49
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There is little reason, aside from the obvious ones you already mention, to avoid the coldest setting. You might be concerned with scoop-ability of some frozen desserts, but that probably will not be too much of an issue for store-bought products, which are often stabilized for texture. Also, these can be removed in advance to temper.

The Institute for Food Resources at the University of Nebraska-Lincoln, states that "most foods will maintain good quality longer if the freezer temperature is -10°F to -20°F."

The Ohio State extension states, "the colder the better."

Freezer burn is not caused by cold temperatures. It is dehydration that occurs from poor or improper packaging. It is not unsafe, but usually not pleasant.

Most modern freezers control potential ice build up. So, that is usually not an issue either. However, some chest freezers might need the occasional, manual defrost. This would be the case regardless of your set temperature.

moscafj
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    Well increased power consumption is a pretty significant reason. Regarding storage time, is that really something to maximize? I.e. isn't the goal “long enough” rather than “as long as possible”? Also, ice cream at –10 or –20°F is nearly impossible to scoop, and it's an error-prone hassle to remove it early enough to warm up enough but not too much so it melts. It would be easy to waste more food this way than you would save with a theoretically longer storage period. – Reid Sep 21 '21 at 16:02
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    `Most modern freezers control potential ice build up` - yes, but they do that by blowing warm air through the freezer. Will that work as well at lower freezer temps - or burn a LOT more energy perhaps? – Joe M Sep 21 '21 at 16:39
  • In biology labs, the "temperature at which biological activity completely halts" is [-135C](https://blog.labtag.com/how-long-can-you-store-samples-in-the-freezer/) and they like to go lower than that to be safe. Higher temperatures lead to degradation. – SurpriseDog May 18 '23 at 02:29
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Two minor considerations (but still is an answer)

  • Even if your freezer can be set as low as -22, it is good to have some safety margin in regard to the freezer longevity.

Most machines don't like being operated at their extreme settings and they are much safer by operating somewhat off the extreme. Both energy consumption and wear are expected to double or triple (an educated guess, it can be even more) between -18 and -22.

Random failure modes like cracking or breaking internal doors or drawers or frost build-up inside the insulating foam are also much more probable.

  • You don't gain much more storage time at -22, compared to -18. I am yet to see something gone bad when stored at -18, even after years of storage. Yes, textures somewhat change, but in regard to textures, the colder is not the better anyway.

When it is good to crank your freezer lower, even all the way down to its possible minimum temperature?

  • Unreliable electricity
  • Frequent opening

These both get the temperature temporarily higher than the setting. Whatever the reason is, you will have some time until the temperature climbs above the acceptable values.

(Modern freezers automatically react to the frequent opening by lowering the temperature)

fraxinus
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There are two things that can happen if the freezer is too cold for extended periods of time:

  • You'll get more ice build-up (especially with frequent use) and
  • The food inside will have more freezer burn than expected

Note that some more modern freezers have a "quick freeze" setting that drops the freezer temperature for a few hours and then returns it to "normal", as there are no problems with having a lower freezer temperature for a couple of hours, most issues will happen after an extended period of time with too low temperature

Juliana Karasawa Souza
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    Freezer burn is caused by dehydration as a result of poor packaging, not temperatures that are too cold. Your link highlights that temps. that are too WARM are a problem....It states, "zero and below...." – moscafj Sep 21 '21 at 11:03
  • @moscafj maybe that's not the best reference - a freezer temperature too low definitely can contribute more freezer burn over extended periods of time vs the "proper" temperature. That's assuming that everything is properly packaged so the "incorrect packaging" is not the issue at hand – Juliana Karasawa Souza Sep 21 '21 at 12:13
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    I would like to see supporting evidence. I'm not convinced that is the case (given proper packaging for freezer storage). – moscafj Sep 21 '21 at 13:38
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    @moscafj - you are absolutely right. I had an old freezer set to so cold that ice cream wouldn't get soft for about 15-20 mins at room temp. Never ever had freezer burn. Now my basement freezer chest was set much higher and would get freezer burn from the process of things getting soft and refreezing. (Poor packaging also an obvious point. You leave lid off of ice cream or anything and you get freezer burn) – blankip Sep 21 '21 at 17:29
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    One of the reasons that some critical science and medical supplies are stored in dry ice or even liquid nitrogen (-196°C) is that the lower temperatures largely _prevent_ the destructive effects of a household freezer. They certainly don't exacerbate these issues. As for ice build-up: that's mostly a result of letting air (at room temperature and -humidity) into the freezer, the exact temperature make little difference on this. – leftaroundabout Sep 21 '21 at 18:23
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    Most commercially frozen foods are "quick/flash frozen" in freezers at -40 and they don't have freezer burn because of their packaging. – computercarguy Sep 21 '21 at 19:56
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    I would edit out the part about freezer burn. It is 100% untrue. – evildemonic Sep 21 '21 at 21:54
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    Yeah, sublimation (the process by which "freezer burn" occurs) is *slower* at lower temperatures, not faster. Ice build up is also questionable... the temperature could only make a difference to ice buildup which occured *while the freezer was open*, not the buildup which occurred after it was closed. – Sneftel Sep 22 '21 at 14:09
  • I was told freezer burn only happens in frost-free freezers. https://www.thekitchn.com/the-problem-with-frost-free-freezers-247588 – jcollum Sep 22 '21 at 20:07
  • @jcollum, that's not what the article says. It says freezer burn can happen more in frost-free freezers, not that frosted freezers never get freezer burn. I find their claim that the temperature raising to do auto-defrost causes more freezer burn to be sketchy. I'd like to see their research before believing that part. – computercarguy Sep 23 '21 at 22:45
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I assume you mean standalone freezer, not refrigerator+freezer combo.

There is no reason to not use the lowest temperature setting, except the obvious wear of the machine. The advantage of this is that food may keep a bit longer. The temperature within freezer is not uniform - it will be a bit warmer near the door. Depending on which location the manufacturer used for measuring, and inaccuracies of thermostat, it may vary slightly. Many food I see has label saying something like -10C: two weeks, -18 C: until expiry date. So to be extra sure it never exceeds the -18 C, just dial in couple extra degrees.

Regarding the disadvantage of thaw times - use fridge and the built-in freezer it has. The food you know you will be using soon - a week, a day - just keep it in fridge's freezer. It has higher temperature, so the food will not be as rock frozen. Whenever you use stuff from fridge, bring new ones from the freezer. I do that with ice cream - fresh from freezer, it can bend spoons, but in fridge freezer, its nice and soft. In case you need to get something thawed out now - microwaves are great for that.

Alternatively, you can rearrange things in freezer slightly - move the stuff that you want absolutely rock solid frozen deep inside, and keep the stuff you want not-as-much-frozen near the door.

Thomas
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