Costs for geothermal drilling - Is it worthwhile in our case?

I was at my trusted heating engineer yesterday and he said that you can forget about deep drilling at that price. We will probably switch to a trench collector. The additional costs compared to an air-to-water heat pump are estimated to be about 4-5k. However, the heat pump for the trench collector itself is somewhat cheaper than the air-to-water heat pump. If you also take the BAFA subsidy into account, it will probably be cheaper overall than an air-to-water heat pump. He said he had already installed trench collectors with an annual performance factor of 5.5. If you could achieve that, it would of course be fantastic.

According to our heating engineer, it is not possible to receive funding for air-to-water heat pumps in single-family homes, even with good systems. I also did some calculations online and it is certainly not possible in southern Germany. Maybe in the north, since different outdoor temperatures are assumed here.

We have just recently received funding from BAFA for our air-to-water heat pump.

How long did it take?

We have just recently received the BAFA subsidy for our air-to-water heat pump.

Which air-to-water heat pump do you have? When was it built? Innovation subsidy for new buildings?

Which air-to-water heat pump do you have? When was it built? Innovation subsidy for new buildings?

LWZ 504 from Stiebel Eltron, 2017, yes exactly

Ok, I can't explain that. Possibly a solar thermal system on the roof and funding through improved system efficiency?