[superkuh]

Spoken like someone with no lived experience of winter. But yes, the vast majority of people do live in temperate regions on the coasts. And for them heat pumps are a great idea. I'm not anti-heat pump. It's great technology.

But saying, "It's not a complex issue at all." is an extremely provincial mindset. For California? Yes. But there's more to the USA than the coasts and south.

And re: capital cost, because of the required in-ground loops the payback is much, much longer than air units which require no excavation. Still, a great choice for new construction if there's a normal heating backup and you can roll in the extra cost to the bank loan. Not so attractive for existing houses.