I'm definitely interested in heat pumps, but we also live up north - 12F average in January. Does it hold up well during polar vortexes, when you are below 0 for a few days?
The only issue I've seen is the large buildup of ice below the outside unit. The unit is elevated on legs for just this reason so it hasn't affected its operation. The ice is formed when the outside unit goes through its defrost cycle in cold weather; water dripping off freezes when it hits the ground.
They all have back-up electric heat elements that kick on when the heat pump can’t keep up. In our mid-70s build home (mediocre insulation and windows), that happens somewhere in around 15F. Basically a few nights/month in Jan and Feb. I can see the bump in electric bill when we have an unusually cold winter.
But, overall it’s not a bad system. Most of the time, it works fine. The one downside (vs radiant heat) is it can feel drafty. But that’s going to be true of any forced-air heat.
Anyway, sounds like you’re right on the edge of where a heat pump might be suitable, so you’ll need to talk to a specialist (or at least somebody else who’s used one locally). They’ve come a long way in efficiency and if it’s a new home, the better insulation will help a bunch too.