> This is borderline a tangent, but I think manufactures should be required to provide data regarding efficiency at specific temperatures.
These are available, and there are standards for EnergyStar approval and for being able to call yourself a "cold climate" air source heat pump (ccASHP):
Mine isn't listed. My takeaway is that it isn't rated for cold climates. For what it is worth, I know the HSPF rating is 8.8 but I don't know at what temperature that is calculated at.