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There is a freezer in my kitchen. It has frozen fish fingers and spinach and potato waffles and leftovers. The food stays below freezing temperature using the principle of latent heat. The freezer pumps heat from the inside of the box to the outside. The back of the freezer looks like this:

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The pipes are warm to the touch. This is where the heat taken from inside the box goes.

Suppose the freezer uses 200 Watts. I also have a small space heater that uses 200 Watts. I could leave the freezer in the kitchen with the pipes against the wall, essentially wasting the exhaust heat, and turn on the heater in the living room. Or I could move the freezer to the middle of the living room so the pipes are exposed. Then we sit on the couch and warm our hands around it.

From a heating point of view, is there any benefit to using the heater rather than the freezer?

One might imagine the heater converts electricity to heat more efficiently. But one second thought, is not every electrical device just an indirect way to convert electricity to heat? Usually a device is called inefficient if it is designed to do something other than create heat, and it makes a small amount of heat.

The more general question -- is every electrical device as good of a heater as any other? For example the big old television puts out a lot of waste heat. But that just means we can leave off the radiators, right? Or is there more to it?

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Unless it's delivering energy to the outside (e.g. radio transmitter) or pumping heat to/from the outside (heat pump, air conditioner), yes, every electrical device is as efficient as a heater as any other.

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You have a heat engine which will transfer heat from one region to another with the expenditure of less electrical energy than the amount of heat which has been transferred. So you can think of it as a device which is greater than $100\%$ efficient.

The problem is that once the fridge has reached its interior temperature the only heat you will transfer into the room will be the heat which has entered the fridge from the room. Putting something at room temperature into the fridge will temporally produce a net transfer of heat into the room but once the temperature of the object is constant there is no net gain in terms of heat transfer efficiency.

All is not lost as there will be losses in the compressor motor etc which will generate heat but then you might better off having an electric heater in the room.

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    $\begingroup$ This is nonsense. Energy is conserved. If you have 200W in, you have 200W out in the long run. Only transiently, as the device (whatever it is) is rearranging its internal energy, will the output not equal the input. $\endgroup$
    – John Doty
    Commented Jan 18, 2023 at 18:14
  • $\begingroup$ @JohnDoty Instead of Only transiently I wrote will temporally and then there is no net gain in heat transfer efficiency. And I did not use the word efficiency as I thought it to be implied. However I have now added it. My last sentence is equivalent to your third sentence. $\endgroup$
    – Farcher
    Commented Jan 18, 2023 at 23:03
  • $\begingroup$ Why would you be better off with an electric heater? $\endgroup$
    – John Doty
    Commented Jan 18, 2023 at 23:06
  • $\begingroup$ @JohnDoty An electric heater would be cheaper to buy and maintain as there is but a marginal and transient gain in using a refrigerator. To get a "useful" efficiency gain with a refrigerator one would have to keep restocking it with "warm" items to keep getting the transient situation. $\endgroup$
    – Farcher
    Commented Jan 18, 2023 at 23:13
  • $\begingroup$ Sure, but if you already have a refrigerator anyway... $\endgroup$
    – John Doty
    Commented Jan 18, 2023 at 23:15

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