Geothermal energy: pros and cons?!

Then we have completely different problems. :P

That would be off-topic, though, and someone would have complained that the thread was hijacked.

Yes, it was probably about a water source.. as happened in our neighboring village. Who is to "blame" for that?

But with this heating principle, no water source is tapped...

It works with geothermal energy, which has nothing to do with water sources.

You pump a carrier medium down in a piping system, it is heated by the warmer earth and pumped back up again.

There are also water/water geothermal heat pumps. Warm groundwater is pumped up on one side, passed through the heating system, and cold on the other side pumped back into the ground through a drainage well.

To return to the original question: I think every heating system has its advantages and disadvantages. As a layperson, you can't really keep track of everything and should definitely consult a professional planner. The most important thing was actually already said in the second post: the most important thing is precise planning and execution.

We were originally also on the track of geothermal heat pumps and it definitely had to be a deep drilling. After we then found out based on the heating load calculation and a geological report that, due to the soil conditions of our property, we would have had to do 3 drillings of almost 100 m each, we quickly abandoned the idea. The drillings alone would have cost us nearly €20,000. The money can't even be recouped remotely.

After we then determined, based on the heat load calculation and a geological report, that due to the soil conditions of our property we would have had to drill 3 boreholes of almost 100 m each, we very quickly dropped the idea. The drilling alone would have cost us just under €20,000. The money is not even remotely recoverable.

For us, the boreholes are designed for an output of 7.8 kW (I don’t have the exact depth in mind). Two boreholes were created. The total cost for the drilling (including brine filling, connection, etc.) was about €7,150. In addition, there is the Vaillant heat pump.

Has anyone ever heard that a source from a deep borehole has run dry after a few years?

As already mentioned above, this probably concerns water-to-water heat pump technology. I can’t say anything precise about the causes.

If the heat demand was calculated incorrectly or the entire system is undersized, it can also lead to (temporary) cooling of the borehole.
For example, with my layman’s understanding, I considered activating the underfloor heating via geothermal heating to dry the screed. The general contractor advised against this, noting that this could lead to "overstrain of the borehole and thus to temporary cooling. If drying the screed becomes necessary, it would be better to use construction dryers or similar."
The general contractor said that overstraining the borehole does not necessarily have to happen, but the risk should rather be kept low.
If cooling actually occurs, the borehole can regenerate again. It's just annoying if the hole cools down in winter .

Oh, and if a specialist reads this: I am just a layman—so please don't take certain formulations, etc. too literally.

Regarding the opening thread: When I hear Russia’s threat regarding gas, I am glad that from Nov/Dec we will be heating with geothermal energy. Although this is possibly still a simplistic calculation, since the heat pump runs on electricity. And where does that come from? Exactly! But I think it will be somewhat cheaper than conventional gas heating.