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I have a big refrigerator/freezer and barely use any of the space. I also don't necessarily need to keep things cold all the time, as I mostly use it to freeze ice packs and extend the freshness of vegetables. I think this introduces some inefficiency. What is my range of options for smaller or more intermittency-optimized refrigerator/freezers, and how much efficiency gain would I get from these options?

I believe that the optimal solution is to share my refrigerator/freezer with more people, ideally by finding roommates or something like that. But for now, let's assume that's not an option.

For context, I have looked into the power consumption of various types of freezers as estimated by various outlets on the web. It seems like the smallest "normal food freezers" around (such as here) actually have higher anticipated annual power consumption than the most efficient "normal size" refrigerator/freezers (such as here). These both seem fairly comparable to portable DC-type freezers like this one if it were to run 16 hours/day, although I have no idea how much running time it would need to achieve similar performance to the "normal" ones.

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  • Is your current fridge/freezer an upright model? What are your usage patterns like? Do you go months without any refrigeration needs? Or is it more like you're always using 10% of the available capacity? Or something else?
    – Jean-Paul Calderone
    Commented Aug 29, 2020 at 14:07
  • Thanks, good questions! My fridge is upright and probably about 10 years old. I always use about 0.3 cubic feet of fridge space and 0.2 cubic feet of freezer space. The fridge space is vegetables and the freezer space is ice packs. This arrangement doesn't really vary throughout time. Not sure what temperature I keep everything at.
    – capet
    Commented Aug 29, 2020 at 17:52

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One way to increase the efficiency of an upright refrigerator or freezer is to fill up all of the "unused" airspace with something that won't flow out of the unit every time your open the door (as air will) nor facilitate convection heat transfer from the bottom to the top of the compartment even when the door is closed. If you have some plastic containers that you would normally discard or recycle, try filling them with water and putting them in the fridge and freezer (for the freezer, make sure they're a container type that won't burst when the water freezes). The more air that you can displace with water containers, the less air there is to flow out whenever you open the door (to be replaced by warm air that requires cooling).

There's only so efficient you'll be able to make your current under-utilized unit this way but you may find it to be an appreciable improvement. You could measure the improvement relatively easily with any "kill-a-watt" style device. You can also factor into this approach the fact that you avoid buying a new device (with some embodied energy that goes into any lifecycle analysis of (in)efficiency). At worst, this might be a good intermediate strategy until your current fridge finds a new home where it can be put to better use (and can substitute for someone else's purchase of a new appliance).

Separately, to extend the storage time for vegetables, you might find that a very warm setting is sufficient. The greater the difference between the temperature inside and outside of the refrigerator, the more energy required to maintain that difference. If you bring the inside temperature closer to the ambient temperature, you can produce a significant efficiency improvement. Many vegetables will still have a very good storage time at 50°F (certainly compared to what it might be outside of the refrigerator, 70°F or 80°F or higher). Note of course that such high fridge temperatures are not safe for all foods to be careful with this option.

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  • Great ideas, thanks! I will try that.
    – capet
    Commented Aug 31, 2020 at 15:36
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So if you only need a small capacity and high energy efficiency, one model that is popular in the sailing community is https://engelcoolers.com/

They have a reputation for efficiency. Can be used with 12/24v DC or 110/220 AC

There are cheaper brands, but whether that is the most economical in the long term is another issue.

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  • Thanks! This looks perfect. Do you have a way to estimate what percent of the time it would need to be running if it were used year-round?
    – capet
    Commented Aug 31, 2020 at 13:53
  • I would try asking the manufacturer
    – barrymac
    Commented Aug 31, 2020 at 17:07
  • Thanks a lot! I did that and they directed me to this: cdn.shopify.com/s/files/1/0343/7179/7125/files/… ; can anyone guess whether the amperage draw listed there represents a) the amperage draw for the time period when the device is running or b) for the time period when it is running plus when it is not running?
    – capet
    Commented Aug 31, 2020 at 18:42
  • This is a great answer, thanks! I just picked one of the two at random.
    – capet
    Commented Sep 25, 2020 at 23:50

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