xkcd
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Isn't that a bit backward? Compress in the cooler area, radiate heat, bring it inside and expand, absorb heat, then carry it outside.
That's what I was thinking. Expansion/absorption happens in the air handler in the house, while compression/radiation happens outside.
For heating, it usually just turns on an electric coil in the air handler.
They work in reverse too. A heat pump can heat more efficiently than a resistance heater.
If you were trying to cool a room like with an air conditioner, yes. Heat pumps literally work in reverse, bringing heat in more efficiently than any resistive heater. They output more heat energy than they use, as they are moving heat, not generating it.
They're not only for heating though, they can cool as well.
I guess I interpreted the comic backward; they're heating the room not cooling it.