[fest]

On this topic I've been wondering why are the air-air heatpumps significantly cheaper than air-water units?

As far as I could tell, there's not that much of a difference (different heat-exchanger, circulation pump instead of a fan, maybe a three way valve for hot water)- but I have hard time seeing how they contribute to the price difference of several thousand EUR.

There are also quite a few conversion projects (where an air-air unit is converted to air-water), so I'm wondering if it really comes down to just higher demand for air-air?

[Gibbon1]

One thing I found out that's a bit infuriating is committee the the sets national code standards has effectively banned R290 (propane) monoblock heat pumps. No residential indoor or outdoor heat pumps with more than 144 grams of propane. You can have a 20lb tank of propane on the BBQ you store in your garage in winter. Trust us this has nothing to do with the representatives of the companies that manufacture refrigerant on the committee.

It's infuriating because a R290 monoblock air to water heat pump is something you could install yourself. And R290 is really cheap and environmentally friendly.