heat pump 80: there is heat everywhere. "refrigeration" units just move the heat away from where you don't want it, which leaves less heat, which we Joe Sixpacks generally define as "cold."
scientifically, absolute zero is the only "cold" that exists, in the vicinity of -368 degrees kelvin. water freezes at 0 kelvin.
anyway, to get more heat inside, you have to move it in from outside, thus using a refrigeration unit. used this way, it's a heat pump.
you get X amount of BTUs from running Y amount of electricity into a resistance heating element, like the emergency heat unit of an electric furnace, or the burner on a stove, or a space heater. this is a constant, X amount of BTUs for Y amount of kilowatts, no matter what the case looks like.
a heat pump doesn't use resistance heating in its efficient mode, it uses heat transfer to move refrigerant and bring heat with it from outside (outside air is common, outside ground temp via water tubes is more elegant but costly as all heck.) Y amount of kilowatts can result in up to 4X amount of heat at the transfer coil in your air duct. so it's much more efficient.
heat pump 100: if the ambient temperature in the heat capture field drops below 42, you go to a 1:1 ratio again. at that point, the system will automatically fail over to backup heating sources, and you can have this trigger on an oil, gas, or electric heating system.
your thermostat has to know the difference between the systems, work with your particular heat pump's preferred cutover point, and make it simple for you.
this is why standard dedicated heat pump thermostats cost $280 from the heating contractor plus installation, where you can get a setback unit on sale some weeks for $13.
not to say you can't get an $80 Honeywell from the big box center that won't work with a heat pump. but correctly in all modes? to be sure, it has to be on the approved list by your heat pump manufacturer.
sig: if this is a new economy, how come they still want my old-fashioned money?
