Groundwater heat pump - disadvantages?

Our 4-unit building (390sqm) is still looking for the appropriate heating system to comply with the city's KfW55 requirement.

Therefore, a question about the possibility of a groundwater heat pump:

We already know that this would probably achieve high efficiency (annual performance factor >4), so that the additional cost compared to gas + solar thermal, or air-to-water heat pump, would likely be recouped quickly given our heating load (about 10-16 years). But what disadvantages might there be that we may not yet know? Is the groundwater heat pump more maintenance-intensive?


(Regarding the conditions, in case they are of interest:

According to the soil expert, it is likely that a groundwater heat pump is possible (one was successfully installed 300m away). To check if it works, a borehole would first have to be drilled to 20m to definitively determine the composition of the soil and the water. This borehole would then later serve as the infiltration well.

Cost of the first borehole including everything: €3,500, total cost of borehole and pump in the end: €16,500. We would thus be investing the first amount at risk, with the possibility that we cannot install the system and then would "only" have an expensive domestic water well. Hence the inquiry here.)

Yes, that is the risk. Plus the approval feasibility. But if it works, in my opinion, it is one of the best heating systems.

If everything fits, why not. For me, it would be too risky, as too many factors would have to align. Mineral content of the water, soil composition, flow velocity, water law approval. I wouldn’t put much stock in the statement that it could be realized 300m away. That is probably similar to the soil surveys. Geology doesn’t behave consistently. But I’m also a burnt child in this regard. Neighbors right next to us (about 10m) no rock, zero water in the excavation pit. With us, it fills up completely, so we need water management. Neighbor gets by without soil replacement, we have clay and rock. Too much of a lottery ticket for me. But if it works, it would be a good form of energy generation.

What speaks against a brine-water heat pump? With that, you save yourself the entire water quality issue and the open system, which is the case with a water-water heat pump.

In return, you probably need more drilling meters but get a closed system.

At least, that should be an adequate alternative in an emergency.

It is a groundwater protection area 3, however the lower environmental authority has explicitly pointed out the possibility of such a heat pump. Due to this, a brine heat pump is ruled out.

Do you know anything about the maintenance intensity (possibly in comparison to other systems)?

No one can say that in general. First of all, the water analysis is important so that it can be planned properly.