Ok, where I live in IL it is cold/cool for at least 7 months out of the year. Further, my refrigerator is on an outside wall in my kitchen. Why couldn’t there be a small duct connected to the back of the frig so that the heat exchanger could be exposed to outdoor air during the winter? It is just sort of odd, here I am paying to heat the place, and then paying more to cool this box down when there is perfectly free frigid air to be had outside. Wouldn’t the frig be much more efficient in the winter if it had access to outside air? Couldn’t there be two heat exchangers, one for summer use inside and one remote one to be used in spring fall and winter? A simple valve could switch between the two. What am I missing here?
You’re missing the fact of how big your “heat exchanger” is. If you put your fridge right up against the outside wall and cut a hole in the wall to expose the coils on the back of your fridge to the cold outside air, it would be like a really huge 2 foot by 2 foot dryer vent, and like a dryer vent, it would be letting cold air into your house. Most of us think it’s a bad idea to let cold air into the house in the wintertime, but YMMV. 
And then, of course, you’d have a two foot by two foot hole in the outside wall of your house.
How a fridge works.
The refrigerant keeps cycling back and forth, around and around through the coils. One could probably run a longer set of coils outside and hang them on the outside wall of the house so as to expose them to colder temperatures in the winter, but the question would be, why? It’s pretty efficient as it is, and besides, you’d have the problem of ice and snow accumulations on the coils, not to mention pigeons roosting there.
And it’s possible the coils and refrigerant aren’t meant to freeze, anyway, I dunno.
And it doesn’t look to me like you could switch between two different sets of coils–it looks like it has to be a closed loop, full of refrigerant, with a compressor halfway.
Outdoor condensor coils would be inconvenient and more expensive, and the energy savings might not compensate for this.
If you don’t mind the extra work and expense, why not just modify your fridge to move the condensor outdoors? No? A few bucks a month energy savings isn’t worth the trouble? If you think not, then probably everyone else has the same idea.
PS
Your fridge is keeping your kitchen warm. Your furnace will run that much less. If you have electrical heat, it doesn’t cost any more to run a fridge than to run the baseboard heaters a bit longer w/no fridge helping.
I didn’t mean to cut a hole in the wall! 
I guess you are right though, the duct work might let a wee bitt too much air in. So on to plan B! You could have two exchangers, in a closed system and just bypass to the outdoor one in the winter, I don’t think the coolant will freeze, and it would have to save energy. I guess it isn’t worth the trouble.
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I guess you are right bbeaty, but if I were doing new construction…
It’s not a bad idea, but it does add a lot of complexity to the fridge, as well as some to home construction. You’ll need to arrange ducting to the outside which will limit the flexibility of where you locate the freezer. You need some intelligence in the heat exchangers to sense the outside temperatures and select accordingly. More complexity. Like heat exchangers, this is a type of appliance that works best in specific climates. It wouldn’t be terribly useful in Texas, but would work great in North Dakota.
Now, what do you gain? A typical 25.2 cu foot refrigerator uses around 653 kWh/year. At ten cents per kilowatt hour, that’s $65.30/year.
In New England, not one of the warm spots of the nation, we can only reliably assume below freezing temperatures 2 1/2 months a year and below 40 degrees maybe three or four months. So let’s be wildly optimistic and assume you can cut the cost of your freezer by 50%/year. That would be maybe $32.50/year. What’s more, the energy used to run the freezer is being converted to waste heat during just those months that you’d get the maximum benefit from this waste heat is when your idea would work best.
So is it worth the complexity to save less than $30/year? Multiplied by the maybe 30-40 million households that could benefit? Beats me.
>> So is it worth the complexity to save less than $30/year?
There’s no way you can save that or even close to that. I measured my refrigerator’s consumption over a year and it was something like $60/year.
In a huge industrial installation little things like this may be worth looking into. In a home refrigerator they are not.
At any rate, a refrigerator is designed to work in a range of temperatures and will not work properly if it is colder or hotter.
sailor’s last comment is important. Standard fridges (and freezers) for home use work poorly (or not at all) when used in areas that get quite cold in the winter (unheated standalone garages, porches, etc.) You can damage the equipment doing this. So modifying a consumer fridge so it “takes advantage of” cold outside air is Not A Good Idea. This is stressed at a lot of “What’s wrong with my appliance?” web sites.
In fairness sailor, Finagle did say s/he was making a wildly optimistic assumption…in order to demonstrate this point.
And my point is that the assumption is not "wildly optimistic"as much as “completely impossible”. I have a simpler idea. for the three coldest months of the year just switch off your refrigerator completely and bury your food in the snow outside. how much do you think you are going to shave off your annual refrigeratoir bill? Maybe 6 or $8 because and, as has been said, you’d still have to add those 6-8 in heating the house, so the answer is you would save $0.00. And that’s disconnecting the refrigerator.
ftg, keeping the refrigerator in a place which is too cold should not damage it but the refrigerator will not keep proper temperature in the freezer. The thermostat is in the lower part and the sysytem is balanced so that the compressor has to run often enough that low temperature will be kept in the freezer. If it is very cold outside, then the compressor doesn’t run often enough to keep the freezer frozen.
I dont get it. I would think that you would want the refrigerator to help warm up the house, since youre keeping the food inside at a constant cold temperature anyway.
I would think the problem is during the hotter months when your refrigerator has to work extra hard to pump the heat out of the box. Cooling that down during the hot months would be a better way to save than to shut off the fridge during the colder months then turning up the thermostat a little higher to get warm.
From Repair Clinic.com
is an example of what I’ve seen.
Ok, well it looks to be obvious that there is little to be gained by moding a commercial unit, and that the costs of new development aren’t worth it for the energy savings.
I had this other idea about sinking a pipe 100’ into the ground and circulating water through it to cool the frig part, no cfcs required you see, but that is probably not worth it either. Ok, well thanks as always for the enlightening thoughts and explanations.
Sticking a pipe 100 feet into the ground would get you heat, not cold. And this one works (a little.)
They work both ways.
“Third, during the summer, the ground source heat pump “reverses” into cooling mode. This fact makes the ground-source heat pump more energy efficient for cooling than a traditional air conditioner”
Get a strong box, metal, and put it outside. When it is freezing outside consistently ( no melting you’re sure) you can store food inside.
Make sure it’s reflective, not colored and epsecially not black.
You should have a thermometer inside.
Or if you like, you could put bags of ice on the inside of the wall of the box - it won’t melt in the cold, but if it climbns to 40 degrees your food won’t necessarily spoil.
Exactly my point. Except that in the hot months the air outside is. . . . hot!
ftg, thanks for sharing that. I had not thought about that aspect.