I used to live in a poorly insulates rented house with an air-source heat pump in Phoenix. The winter electric bills were fine; I got suffocated by the summer electric bill. It's too bad somebody didn't put a ground loop in that house when it was built, maybe 40 or 50 years earlier.

> The low price of natural gas is currently the biggest challenge for the success of geothermal heat pumps. If a home is equipped with a natural gas furnace for heating (and the need for cooling is limited) there is no financial reason switching to a heat pump, in fact, you’d be worse off.

Air conditioning is optional where I currently live. Cogeneration (with natural gas) and battery storage is a good intermediary step to the free-energy nirvana (fusion or whatever) that's hopefully in our future.