Basics

A heat pump - using air heat exchange - extracts heat or cold from the ambient air. There is an outside compressor, and indoor heat exchanger. A split unit. Install requires placing the heat pump outdoors, and placing one or more heat exchangers indoors.

Working Doc

This one says that it's not worthwhile below 30F [1]. How to reconcile with manufacturer claiming -13F?
It seems to be that it works very poorly at the low temps.
- 32F, COP is 3 [2] but at 10F it appears to be COP=2.
- At -5F, COP=1.3 and it shuts down, for backup heat to take over.
Pioneer mini-split page says it works to 90% capacity at -13F! [3]. just try it.