Oh, in Swedish they're both called heat pumps, i didn't realize there was such a distinction in the English language between the two systems.

In my mind they're just different kinds of heat pumps.

And yeah, drilling is pretty expensive, but once the system is installed, heating is ridiculously cheap. When my parents installed geothermal, ROI was estimated to about 5 years for their house iirc.

But then it may well be that drilling is cheaper here by virtue of being more common, idk.

There both is and isn't. If someone says heat pump in a generic heating context they don't care. However most of the time the difference is significant, so geothermo is added as a qualifier where that is what is meant, and heat pump alone means air to air. You have to guess from context which it is though - and you won't always be right.

Heat pumps are cheaper than propane at least, though I'm not sure if they are enough cheaper as to be worth the cost.

The context maters here. If a boat is being discussed, it won't be air to air.

What's your point?