Hydrogeological Report - Geothermal Energy, Air-Water Heat Pump or Ice Storage?

Good evening everyone,

we want to replace our gas heating system (over 30 years old) with a new one. In addition, we want to remove the traditional radiators and install underfloor heating throughout the entire house. We intended to mill this into the screed. Unless a complete renewal with new screed, etc., is more sensible?

1) Hydrogeological expert report: We had considered a geothermal heat pump as the heating system (geothermal energy). However, since the building is located in a water protection area, a so-called hydrogeological expert report is required to check whether geothermal energy is permitted and to what extent (depth, brine, number of boreholes). Unfortunately, the water authority is very strict. I have attached the information sheet with the requirements for the report.

Have you ever heard of such a hydrogeological expert report and do you know how much it costs? We honestly can’t estimate the whole thing and wanted to inquire whether anyone has had similar experiences.

2) Comparison of air-to-water heat pump and geothermal energy: The two systems are always compared with each other. One person says this, another says that. But I haven’t really heard or found any solid facts on the matter yet. Geothermal energy is said to be more efficient, but air-to-water heat pumps are now also very powerful and therefore more worthwhile. The trend is also rather towards the air-to-water heat pump, which is somewhat cheaper to purchase than the geothermal system. Prices have risen sharply everywhere at the moment. Can someone provide us with further information on the topic that would help us in our decision?

3) Ice storage heating: The heating/well engineer even suggested an ice storage heating system as an alternative, since no approval is required there. However, I don’t know anyone who uses such a heating system. What do you think about it?

Many thanks for your help and best regards!

we want to replace our gas heating system (over 30 years old) with a new one. In addition, we want to remove the traditional radiators and install underfloor heating throughout the entire house.

What about: facade insulation, cellar ceiling/roof/upper floor ceiling insulation, new windows, etc.? Just underfloor heating + heat pump does not directly mean low heating costs. What does the room-by-room heating load calculation say?

Unless a complete renovation with new screed, etc. is more sensible?

I always see that as more sensible because then you can lay pipes more flexibly (different (larger) pipe sizes and spacing - a heat pump needs flow, flow, and flow) and it is also not really more expensive. Keep in mind that not only the pure heating system but also the related work is subsidized.

2) Comparison of air-water heat pump and geothermal energy: The two systems are always compared with each other. One says this, the other says that. But I haven’t really heard or found real facts about it yet. Geothermal is supposed to be more efficient, but air-water heat pumps are now also very powerful and therefore more worthwhile. The trend is thus more towards the air-water heat pump, which is somewhat cheaper to buy than the geothermal system. Prices have risen sharply everywhere at the moment. Can someone give us more information on this topic that would help us with the decision?

Both systems actually work very well. Assume that you cannot recover the additional investment for geothermal over the lifetime (due to drilling, it often costs tens of thousands of euros more than the “simple” air-water heat pump. Far from “somewhat cheaper.”). The higher efficiency means, for a new building, €47 heating costs instead of €50 monthly with the air-water heat pump.

The heating/well builder even suggested an ice storage heating system as an alternative,

Exotic, but apparently works. However, I have never seen it live in over 20 years in the construction (financing) industry. Due to the combination of geothermal energy and ice storage, it is by far the most expensive option (the ice storage alone is likely to cost five figures - additionally). As far as I know, suitable for houses with very high heating and cooling demand – so commercial properties.

The multiple efficiency means €47 heating costs instead of €50 monthly with the air-water heat pump in a new building.

But could that not possibly become relevant for an older house with a large living area? Just asking.

Unfortunately, I don't have much to contribute, except that my parents are currently facing similar questions. (Water protection area but not the highest protection class, I would have to ask again exactly what. Old, large house, but several insulation measures have already been carried out. The oil heating system is due to be replaced soon and no one really knows what to switch to...)

Could this possibly become relevant for an older house with a large living area? Just asking.

Yes, of course. The worse the house, the more likely you are to recoup the extra cost for geothermal energy. Accordingly, the current energy consumption as well as the planned consumption after renovation would be important.
It would also be relevant in which area the house is located and what temperatures to expect in winter.

Could that possibly become relevant with an older house and a large living area? Just asking.

Yes, it can. Then the difference shrinks. BUT: The additional effort with the old building can be better invested in further energy measures. Because then the house probably consumes less energy than with the efficient brine heat pump.

We are also building in the [Wasserschutzgebiet] and planning a brine heat pump. Deep drilling is not allowed, but surface collectors are. I spoke with the lower water authority and it was basically no problem… there are a few requirements regarding the installation depth (x meters above groundwater), pressure monitoring of the brine circuit to detect leaks (easy), and regarding the brine itself (easy). Connection by a specialist company, that's about it as far as I remember.

We are planning a trench collector.
The hydrogeological report probably refers to the groundwater level, we don't need it since the collector is only installed at a maximum depth of 2m and our groundwater is much deeper.