So if someone set off a series of EMPs across the planet leaving only a handful of computers functional, the difficulty would adjust downward to account for it?
(I don't actually do this because I don't have a desktop computer, and it's unclear if building one at this point will pay for itself before custom integrated circuits push the bitcoin difficulty so high that GPUs become worthless)
Of course, energy has to be expended to move heat around, and there are inefficiencies. But with real-world equipment and common cold-but-not-too-cold temperatures, a single unit of electricity can be used to move several times as much heat as it would produce if you just converted it to heat directly.
A computer is as efficient as anything when it comes to converting electricity to heat. Heat pumps win because they're ultimately playing a different game.
But, thanks for clarifying.