Heating concept for single-family house new build approx. 190m²: Split heat pump vs. ground source (brine)

According to our heating engineer, a brine heat pump with surface collectors is not possible in our case due to the size of the property/garden. That means my price refers to ground probes with a borehole depth of 70m.

Brine heat pumps with surface collectors are hardly seen anymore these days – precisely because drilling has become massively cheaper.

I would also briefly inquire just to be on the safe side whether drilling is even allowed with you. For example, no drilling permits are issued here.

As I interpret the feedback so far, I am actually slowly tending more towards the Split heat pump. The outdoor units of a Split heat pump are significantly smaller than those of a "real" air-to-water heat pump. The heating engineer advised against the "real" air-to-water heat pump due to the installation size of the outdoor unit and the small price difference compared to the ground source heat pump (~€2,000). I will follow up on the tip regarding the approval.

Have you ever checked the consumption data of the heat pump in the consumption database to see how the consumptions of the two devices are there? An efficient air-to-water heat pump is not that far away from a brine-to-water heat pump anymore, if the air-to-water heat pump is rather crawling around a seasonal performance factor of 3, it can look different.

That means my price refers to ground probes with a borehole depth of 70m.

What should the drilling cost? For example, we had an offer here of €65/m gross (depth 85m). Calculated on your 70m, that would be €4,600. If I then assume that both devices cost about the same in purchase and installation, the different subsidy amount from BAFA should actually almost compensate for the additional drilling cost.

So maybe start by looking at the costs for the source.

Have you ever checked the consumption database for heat pumps to see how the consumption of the two devices compares there? An efficient air-to-water heat pump is not that far off from a ground-to-water heat pump anymore; if the air-to-water heat pump is struggling around a seasonal performance factor of 3, it might look different.

I looked up the Buderus Logaplus WPLS.2 (the split unit), it appears once in the database with a seasonal performance factor of about 3 in 2018. I can’t find the ground-source machine offered in the database (Buderus Logatherm 8K-1).
I am currently reading into the topics of trench collector and, in parallel, the popular Panasonic monoblock.
With the Panasonic, I am wondering how long the water pipes to the outdoor unit to the utility room are allowed to be since the garage is attached directly to the utility room and I would have to place the outdoor unit several meters away already (or on the garage?!)

@Dr. Hix: Could you maybe provide me the contact via PM? You’re from NRW as well. I have borehole costs here of a gross €10,600 (2 boreholes at 70 meters each including accessories, including pipe trench up to 20 m including fault-dependent borehole insurance), so that would come to a steep €151 per meter.
With your price, after deducting the subsidy, I would be pretty much the same, that’s right.