Here in the Chicago area, natural gas is piped in underground, and for the most part, the electrical infrastructure is above ground, and thus vulnerable to ice

Here in the Chicago area, natural gas is piped in underground, and for the most part, the electrical infrastructure is above ground, and thus vulnerable to ice and the errant vehicle taking out a pole. Thus, the risk of losing electric power is the highest at the time you would need it the most if you relied solely on a heat pump to keep your house warm, and your water pipes from freezing and then damaging everything. This is a very strong incentive to have natural gas heat, and a small generator to be able to run the fans to operate it. (Or perhaps a large UPS rated for inductive loads) I think a gas operated backup generator that could then exhaust it's waste heat as input to a heat pump would be the best of all worlds. Most of the time, it serves as insurance. On really cold days (it has gotten down to -40 in my lifetime), or when power is out, it could both run the heat pump, and serve as the "emergency heat" sometimes required for an air-source heat pump. Of course it would be better to have a ground loop heat pump, but that's not always an option.