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Comment by sandworm101 | Hacker News Reader

A 100w space heater will produce exactly 100w of heat. A 100w heat pump, properly installed, may turn that 100w of power into 300w of heat output on the hot side. This >100% language is marketing for people who do not understand thermodynamics or who dont want to bother with specifics.

The same is said of those scam "personal" AC devices that blow air over ice. They too are "more than 100% efficient".

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> This >100% language is marketing for people who do not understand thermodynamics or who dont want to bother with specifics.

That is a little unfair: this is the language of economics rather than physics, so if you are paying for 100w and getting 300w, that is indeed over 100% efficient. SCOP is a more "correct" term but is less clear when communicating with the public and (IMO) is mostly for professionals or people with a technical understanding of heat pumps. Nobody thinks they defy the laws of physics though.

It's not exactly just marketing, it is indeed possible to "move" heat energy by using less energy than the amount of heat energy moved, which all modern high efficiency compressor based air conditioners/refrigerators/mini splits/heat pumps can do. It's still a useful metric for comparing similar devices' efficiencies. It's called Coefficient of Performance and if it's only 1, your compressor based system has a major issue.

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