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by gdpgreg 2671 days ago
They're not a conversion system so you don't measure them in terms efficiency, rather you use coefficient of performance, you can never have efficiencies above 100%.
1 comments

In power terms it is above 100% efficient because the watts in is lower than the watts out.
No, the heat moved is greater than the watts in. The machine itself has considerable parasitic losses, and a simple electric baseboard heater is more “efficient”, using the strict definition of the term.

The difference is that most people don’t care about “efficiency”; they care about heat moved per watt. But it matters a great deal more when you try to use a heat pump in a really cold environment, as the heat-transfer ratio of the machine plummets (which is why, in the real world, heat pumps fall back to gas or electric in cold weather).

It also matters in a scenario where you’re comparing two different machines that are powered by something small and intermittent, like a windmill.