The fuel-switching issue is interesting. And the fact that they have units that work down to zero F. We're on the cusp of being able to use them for heat. Since it is not uncommon to go into the teens at night and rarely below 25 during the main part of the day, some people do get by with just the air-source heat pump, but when it's in the 20s, they run and run. The overall efficiency of the house is a big factor. The neighbor with a new SIP house has no trouble. The neighbor with an old house with very little insulation has it run non-stop for weeks at a time, sometimes with huge amounts of ice building up on it.
I've also been curious carbon and cost tradeoffs. I think the cost tradeoff would be less here because electricity is expensive in CA, though with the pricing going into effect this year, there will be summer and winter rates for us and the winter rates are a lot lower.
Tiered rates are a big disincentive. If changing to electric heat pushes me into a higher tier, it means those KWH are all at the most expensive rate. If I go into Tier 3, that's 41 cents per KWH. My lowest possible rate in the winter is 23 cents. Google says the average rate in MN is 11.5 cents. So if I went to electric heat, I would be almost 2X to 4X that, which cuts into the savings from a heat pump.
