Space and cost for geothermal heat pump

Hello everyone!

We are currently considering what and how we want to build. It is about a new building that is to be constructed by a property developer. Currently offered is a 36cm Ytong exterior wall. I would like to replace the standard heating system with a gas burner and radiators by a heat pump with underfloor heating throughout the house and thus completely do without a gas connection.
I actually do not want to use an air heat pump because I neither want the noise nor the unit in the garden, and I am not exactly enthusiastic about the decreasing efficiency during the cold season.

However, a few questions arise for me regarding the design and implementation. On the one hand, I have no estimation of how much more expensive geothermal energy is compared to an air heat pump. Do you have any rough values? I would like to work with geothermal probes, i.e. drillings, as I consider it to be the most solid method.
But what if there is damage to the system? The technician can unscrew the air heat pump and work on it. Nobody would want to dig up the geothermal probes, right?
And how much space do you need for something like that? I thought that the drilling could also be done in front of the house, i.e. between the house and the sidewalk. There would only be about 3-5m of space there. If someone ever needs to get to the pipes, the pavement would have to be removed. I won’t be able to get heavy equipment into the garden later.

To increase the efficiency of the system in the long term, I would like to add photovoltaics later, but that would have to wait a few years for cost and planning reasons.

Thank you for your help!

I can only say we have two boreholes each 70m deep behind the house. There must be at least 6m distance between the boreholes and drilling should not be closer than 3m to the property boundary. For the complete heating/sanitary program including drilling, we paid 35T... No idea what an air heat pump would have cost... It was never an option for us. Oh yes, and the boreholes should be located near the house connections.

Are you crazy? If gas is available, then gas is usually by far the cheapest and most comfortable energy source!

You can also do underfloor heating with gas, but why choose an expensive heat pump (10,000 - 25,000€) when a condensing boiler for 3,000€ will do?
Okay, you have to add the gas connection and possibly the chimney if you would omit it.

With an air heat pump, you will tend to spend more money on energy consumption than with gas, with a ground-source heat pump about the same. (current energy price. Nobody knows the future).

A gas heating system is also much more tolerant of poorly executed/calculated heating systems and there are more installers who are familiar with it.

: Can you roughly tell me what is included in the 35k€? I find the amount somewhat discouraging, to be honest. That would practically be the deal-breaker for geothermal energy.

: Well, I admit I’m not really familiar with this field (which is why I value your opinions very much), but all the calculations I have seen so far actually say that heat pump technology saves energy compared to the gas boiler. Since the efficiency of the air heat pump at low temperatures—precisely when I need it—is poor, the only “true solution” for me would be to use geothermal energy, which should still be efficient in winter. How prices will develop in the future is all speculation, but I expect all fossil fuels to increase significantly in price. On the one hand, the trend is already visible and reserves are repeatedly mentioned, but on the other hand, this is also a politically desired development.

I just took another close look in my nice Excel. Here is the rough breakdown:
8,500Euro for the drilling
24,000Euro for plumbing; this includes everything, so the underfloor heating for about 200sqm, and the complete connections for hot, cold, and wastewater in the kitchen, laundry room, and three bathrooms (3xtoilet, bidet, 3xshower, 4xsinks). I can also gladly check the exact price for the heating itself.

With an air heat pump, you will tend to spend more money on energy consumption than with gas, with a ground source heat pump about the same.

What exactly does "more money" or "about the same" mean in numbers ...? Rhineland greetings from on the road