The other issue here in SF and near the coast is that for older, poorly insulated homes and those with high ceilings (mine are 12 feet), the real problem with an air heat pump is how slow it is to heat the volume. Unless you want to pay to keep your house warm 24-7 it will take an hour to warm up the whole house. I would love to kick my 10 year old forced air gas furnace to the curb, but I don't see how, even if I get solar. Contractors are charging a fortune for installing heat pumps these days too.