Also, the running costs of a heat pump are reasonably comparable to gas heating, so you don't even really save money by doing this. (Plus they're more complex and expensive to replace when they break, the installation process is really disruptive and not practical for everyone, etc.) On top of that, a lot of the electricity to run them is going to come from burning gas anyway in most countries. They mostly seem to have caught on in places where gas wasn't plumbed out to so many homes, there are good reserves of dispatchable renewable sources like hydropower, or both.