Does Alpine's winter freeze change what kind of heat pump I need?
Yes. A heat pump rated for mild coastal winters loses meaningful heating capacity below freezing, which matters in Alpine when overnight lows hit the 20s. We spec cold-climate-rated heat pumps here that maintain heating output in real freeze conditions, which typically costs a few hundred to about a thousand dollars more than a standard mild-climate unit but avoids a house that can't stay warm on the coldest nights.