I work with a food pantry at my church. We receive food on the first Thursday on the month and distribute food to those in need on the following Tuesday. We have several chest freezers which we use to separate meats (poultry, beef, pork) and a stand up freezer for things like lunch meat, hot dogs, prepared meals, sausage, bacon, and extras. My question is, would it be better to leave them plugged in and on the lowest setting, or unplugged? How long does it usually take for the freezer to get back to optimal temp when unplugged? Because there times when he freezer may need to be used at last minutes notice. Also, all but one of these freezers have been donated to the church. They have some age on them. It is good to keep stopping and starting the motor? Isn't there freon (or some kind of chemical) which keeps everything ''lubricated''? I'm open to opinions, but I REALLY could use the ADVICE of a professional fridge/freezers sales/repair person. Thank you so much~~~ Cherie
2 Answers
Freezers have very little "thermal inertia" when empty -- the compressor cycles on and off more often (which can cause more wear) in an empty freezer than one that's full (or partially full) of food, which makes it less efficient:
A full refrigerator retains cold better than an empty one. If your refrigerator is nearly empty, store water-filled containers inside. The mass of cold items will enable the refrigerator to recover more quickly after the door has been opened. On the other hand, don't overfill it, since that will interfere with the circulation of cold air inside. The simplest solution is to buy the right size for your family in the first place.
Full/empty efficiency has also been answered over in Cooking.StackExchange.com: Does keeping a fridge/freezer full significantly help energy efficiency?
I'd suggest not leaving the freezer empty when not in use, but keeping some frozen jugs of water in the freezer all of the time -- not only does this help reduce compressor cycling, but it also helps chill food faster when you load new food into the freezer.
Freezers in daily use can last decades, so I wouldn't worry about excess wear by keeping your freezers plugged in -- just don't leave them completely empty.
Fridigidaire recommends leaving their refrigerators on for periods of a few weeks, and turning them off for longer periods of time:
Leave the unit operating during vacations of less than three weeks. If the appliance will not be used for several months:
- Remove all food and unplug the power cord.
- Clean and dry the interior thoroughly.
- Leave the door open slightly, blocking it open if necessary, to prevent odor and mold growth.
Kenmore has a similar recommendation for their chest freezers.
The key additional factor is: what temp is the food when it's going into the freezer? If it has been kept in a similarly low temp environment (say, coming off of a freezer truck at 0F or below) then putting a large quantity of it into a freezer, even if the freezer was literally not turned on yet, will cause it to get the freezer pretty cold (a freezer unplugged is basically a heavy nonportable igloo cooler). In that scenario, you could save some energy by leaving the freezers open/off at all times when food is not inside them, and plug them in only when the food arrives.
If the food is not cold, say if it was transported outside of sufficient insulation for a period of 15 minutes or more, then you definitely want to drop it into a very cold freezer so you can get it back down to safe storage temp. In that case, you would be advised to not only keep the freezers on, but as another answer said you should keep some additional frozen mass in there (jugs of frozen water) to help maintain the low temp.
Every extra few degrees colder you keep that food prolongs its life (frozen at 20F is not the same as frozen at 0F which is not the same as at -10F) so it is probably worth the few dollars a month the freezers cost to run (most are rather efficient if they are in a room temp environment and not opened.) If I were in charge of the operation, I would opt to keep them running to better protect the lifespan of the food, unless I calculated the actual electrical savings and found it to be a substantial dollar figure (which no doubt can be redirected to better serve the church's mission vs throwing at the electric co).
The only situation where you are going to unduly stress the units would be to take a freezer that was not fully cold and load it with food that was not fully cold, without some additional frozen mass (other already frozen food, jugs of frozen water, etc) to keep it cold. Simply taking the units offline for some period and then firing them back up while empty will not cause excess wear, because chilling an empty freezer is a very easy task.
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