Air heat pump or use gas and solar?

Wow, that surprises me now. I thought the recommendation would clearly lean towards gas....

But good to know that no junk was chosen.

Well, it sounded like an air-to-water heat pump was not desired. Additionally, your general contractor makes it significantly more expensive compared to gas. If you basically want a heat pump, you can certainly choose that.

I have the problem that I still do not understand why a distinction is made between air heat pumps and air-to-water heat pumps.

If the device is good, I am not fundamentally against a heat pump. I am just skeptical because with the Nibe F 750 in our rental apartment we have not had good experiences. However, a lot went wrong with the installation. The ventilation system was not even adjusted at the beginning.

I do not think that the heat pump is significantly more expensive compared to gas from the general contractor. When I see comparison examples on the internet with bills for heat pumps vs. gas, the investment costs for gas & solar are always significantly lower compared to the heat pump than in our case! What is about €2,500 difference? I sometimes read about differences of more than twice that amount.

I have to find someone on Monday to calculate it for me. I can live very well with both and would then take the one that is probably cheaper. If it is roughly equal after 10 years, I would probably tend to gas because I do not see price increases like with electricity. If it looks different, a heat pump could well be an option.

Otherwise, I was also rather against a heat pump because I once (unfortunately I can no longer find the place) read that a pure air heat pump is not necessarily suitable for a house of our size.

I have the problem that I still don't understand why a distinction is made between air heat pumps and air-water heat pumps.

Because the operating principle is indeed the same, namely the extraction of energy from the provided medium. But the medium is fundamentally different, namely air or water.

And thus the efficiency of air heat pumps compared to air-water heat pumps is, to put it bluntly, abysmal.

In addition, air heat pumps simply fail at certain subzero temperatures because they can no longer extract anything from the air. Air-water heat pumps, on the other hand, continue to operate effectively well below zero.

The architect also said something like yesterday that there is a heating system for which you have to access the groundwater, and if I want, we can inquire about it. But why, if the linked device is already referred to as an air-to-water heat pump?

I believe this is just imprecisely formulated.

It is bad if the energy source is the EXHAUST AIR of the house, it can still be called an "air-XY heat pump."
It is also bad if the heat is released into the house by air, that is then an "XY-air heat pump." That is simply uncomfortable. It is common in passive houses, where it makes sense, otherwise not.
What is meant by "air heat pump" ... presumably it simply means an air-water heat pump, just like the one you linked.

Energy from groundwater is a water-water heat pump and the most effective you can have. Very good! But rarely feasible. Municipalities often find it uncool to drill into the groundwater and insert a probe.
It's a pity that the general contractor makes the surface collector (or trench collector) so outrageously expensive. Both the collector costs and the earthworks are totally excessive. This type of geothermal energy is also subsidized by BAFA, I think 4,000€.