- Economies or scale will solve the repair and maintenance burden... hell, it's not like a gas boiler is maintenance free...fucking things requiring serving every year and break down all the time in the UK.
- almost noone has a generator when the power goes out anyway. This is a very wealthy American perspective.
- Gas boilers are far simpler units. Less moving parts, simpler electronics, all in all fewer points of failure than a cutting edge heat pump that can actually produce heat when it's below 20f (-7c, i.e. the only kind of heatpump that might stand a chance at heating throughout the cold winters most of the northern US gets).
- Be that as it may, heat pumps at this time are cost prohibitive - making them largely something only "wealthy Americans" can afford. Many people still run old 80% efficiency units because of similar reasons to boilers: they're cheaper, simpler, and less likely to fail.
My family has one in Poland, it was -20C this winter already and it worked absolutely fine. It's some cheap unit, wouldn't call it "cutting edge". I think there's a simple resistive heater that de-ices the fins at low temps, but it kept the interior of the house at a (very toasty) 24C pretty much non stop even in those low temperatures. I have no idea why people keep saying heat pumps don't work in low temps. I had a basic split unit fitted to my home in UK, literally a basic £600 midea unit and apparently it should work down to -25C without any problem.
>>Gas boilers are far simpler units. Less moving parts, simpler electronics
Have you ever looked inside a modern gas boiler??? I hard disagree that it has less parts than a modern heat pump. A heat pump is like your fridge - there's an inverter, compressor, and a whole bunch of fins, that's about it. A gas boiler has multiple tanks, burn chamber, exhaust recirculation, at least 5-6 probes to measure every part of the process(and they all can fail in surprising ways that renders your boiler dead).
A solution doesn't work in 100% of areas can still be the best one in the 95% of the places that do make sense!
And to your cost concerns, there's a bunch of Federal money (being deployed by the states) in the IRA to specifically pay for low-income Heat Pump upgrades.
If you can afford to have them just for cooling, you can afford to have them for heating as well; in fact, the capital cost may well be lower if people just used their air conditioning systems to heat as well.
The same goes for reliability - we manage to make air conditioning acceptably reliable and the tech is basically the same.
I've lived all around the US, and don't think I've ever lived anywhere with central air. Well, that's not quite true: in New Mexico I had a roof mounted swamp cooler, but that's evaporative cooling and not a heat pump. Elsewhere I've occasionally had and used a portable compressor unit, but rarely. I hadn't realized air conditioning was so overwhelmingly prevalent. Based on people I know and associate with, I would have guessed less than half that rate.
They range from sub-$1K single zone air-to-air wall/window units, to multizone split units, to ground source hydronic boiler/chillers that integrate with baseboard or radiant floors, which can get quite expensive to install, but that's at the high end. Generally speaking they're not really much more expensive than normal air conditioning. I've seen units that come in cooling-only and heating+cooling versions, and the cost difference is marginal (<10%) in those cases.