Green Energy

Here

H2i® models provide heating, even in outdoor temperatures as low as -13° F, producing up to 100% heating capacity at 5° F. These units offer year-round comfort even in extreme climates

Their technical documents show that they are down to about 20% of their usual heat output at that lowest temperature so they need to be sized up accordingly. The reality for most folks in an area cold enough to require these is they have backup heat sources for the coldest days anyways.

Literally any decent heat pump has a COP > 1.0 down to around -20F.

Sorry I don't speak medieval, could you translate the temperature from 16th to 21st century?