Air heat pump or use gas and solar?

But I don’t know which stage you are at, nor what else you have going on.

The construction is about to start. The earthworks will probably begin in 1-2 weeks. Unfortunately, the heating load calculation came at the last minute and ruined the actual plan. Otherwise, I have quite a lot on my plate. I like to do research, but I will not carry out anything myself. The idea of using the excavator guys is out of the question. I hire professional companies for everything.

Regarding the offered "air heat pump," the manufacturer actually states air-water heat pump. I am still a bit confused whether it is a pure air heat pump or an air-water heat pump. The price difference compared to solar and gas also seems quite small to me. In sample calculations, there is always a difference of many thousands of euros in favor of gas and solar; for me, it is only about €2,100 - €2,600.

The region is NRW.

I will have it calculated. It is actually a joke that I am supposed to decide without it having been calculated. Sure, the execution planning is urgent, and it is relevant for that (exhaust shaft). Although it is not my fault that the heating load calculation only just arrived, I’m still the fool if the construction is delayed because of it.

What you write about the heating engineers, I see it the same way. I am now convinced in many areas that consulting and purchasing should be strictly separated.

Then the trench collector is out. If someone has to do that and ends up going for excavation, then that's the end of the price advantage.

I advise against a pure air heat pump.
Air-to-water heat pumps work well if you pay attention to a few things. It is important to choose a good device and have the underfloor heating perfectly designed. Then an annual performance factor of 4 is possible. That means 1 kWh of electricity = 4 kWh of heat.
That eliminates the shaft, the gas connection, and solar.
In my opinion, the air-to-water heat pump should be cheaper than gas and solar. And noticeably so.

So I am not specifically familiar with that. The heat pump looks quite good, if I have read the datasheet correctly. But I am absolutely not an expert in that.

The heat pump is already very decent. With Scroll Inverter technology (modulating heat pump). The price is quite reasonable, the heat pump is definitely in the upper price segment with the equipment.

Then I would take those, to be honest. But take another look at the planning of the [Fußbodenheizung]!

Or, if one can also live with the mid-range, inform the heating engineer so that he can find a cheaper product. 2-3T€ should be able to be saved there.