The units we use up here will work flawlessly down to about 10f, and keep working until approximately -20f. Thanks to climate change, I haven't seen -20f at night in several years, but the last time it happened, the heat pump struggled to keep my house warm but still managed to do it.
"Most" of Canada only gets about this cold, where "most" is the majority of the population that lives near the border.
How far north are you (IECC climate zone)? What is the make and model of your unit? Is it a cold climate air-source heap pump (ccASHP)?
* https://ashp.neep.org/#!/
* https://neep.org/heating-electrification/ccashp-specificatio...
Because there are folks in Climate Zone 7 in the northern tip of Maine (Caribou) that use heat pumpss
* https://www.youtube.com/watch?v=OcwIz6heDss&t=43m21s
Mitsubishis can work down to -13F/-25C and still have a COP of 2.08 (1=resistive heating):
* https://www.mitsubishicomfort.com/articles/keep-warm-this-wi...
* https://mylinkdrive.com/viewPdf?srcUrl=http://enter.mehvac.c...