Wonder if below a certain outdoor temperature it would make sense to use a miner to heat air the pump is intaking? 
Discussion
I'd have to assume it would be more efficient to use a hash heater as an auxiliary unit where it's heat was directly supplied to the space.
Ideally, you could create a central system that would switch between the heat pump and hash heater optimizing for whichever was most efficient at the time, or to save money on asics, simply use a cheaper miner as a supplement.
At a certain point, the money spent on the hash heater is basically wasted if the time it is used drops below a given threshold. At the very least, your ROI could be severely effected of it really doesn't end up being utilized much.
Are you able to share what book that is from? I'd be interested in finding a copy.
Asked an HVAC guy about this a few days ago. Still awaiting his thoughts.
I’m coming up with a plan to prime my water heater. Adding a heat exchanger to the inlet should be a fairly simple job.