Comparison of groundwater / brine / air heat pump

https://www.hausbau-forum.de/threads/lwwp-aktueller-verbrauch-und-daten.36616/post-479572

Read from here, it was about cost comparison drilling versus a normal heat pump.

Basically, hire an energy consultant who does a room-by-room heating load calculation, with installation distances for the underfloor heating and no fictitious room temperature values but living room at 22, bathroom 24 "without additional heating but wall heating via underfloor heating" at least 20 in the bedroom, etc.

Then a modulating one that qualifies for bafa.

So one that has a COP of 4.0

Then find out if geothermal energy is possible and what your region requires for the drilling. Here, a 10,000 euro difference is possible. Until you save that, you can heat for many years.

If you have a huge plot, then ring trench collector is an option here with a lot of possible own effort.

At 140m2 you can luckily not go too wrong.

The design of the underfloor heating is important, that is clear to me. It has to match the heat pump. What exactly matters in this, I still need to research (I would be grateful for tips/links).

No, that is wrong, the design of the underfloor heating must fit the house and your temperature preferences, and this is where the biggest mistakes are often made. Which heat generator supplies it is initially irrelevant. https://www.hausbau-forum.de/threads/Erdwärmepumpe-fuer-ein-kleines-erdgeschossiges-einfamilienhaus.38696/post-486058

Purely monetarily speaking, a gas heating system would be the best choice - preferably with the classic radiators attached... but here it's not about the cheapest solution, it's about heat pumps. Bookstar himself - if you read his posts - is not a fan of heat pumps and certainly not of ground source heat pumps. I am a big fan of them and have installed one myself in our new build (or rather, it will be installed soon).

In general, an air-to-water heat pump is sufficient for many house sizes, as there are different performance classes. I would worry less about that. More important, as T_im_Norden already said, is the proper design of the underfloor heating and the H,T value (transmission heat coefficient) of your house. Roughly speaking, for underfloor heating the rule is: minimum 16x2mm pipe, 10cm spacing (in the bathroom gladly less), and max. 80-90m per heating circuit. Everything else increases your flow temperature and thus also the heating costs.

With a groundwater heat pump, it strongly depends on the soil conditions and the groundwater level. If this is too deep and difficult to access, the drilling costs can become immense. If your soil is suitable, the water authority grants permission, and the extra costs compared to a ground source heat pump don't matter to you, then go for it. Personally, I find the additional costs too high even with better efficiency. With the €10,000 additional costs you mentioned, you could pay €300/year more for heating for the next 30 years with another heat pump and still come off cheaper.

I find the ground source heat pump attractive in terms of price. Especially if you are not completely unskilled and have the suitable land to install a trench collector on your own. For us, including excavation work as three people (2 pipe layers, 1 excavator driver), it took less than a whole day and cost less than €2,500. There is some additional effort for commissioning (about €1,500) compared to the air-to-water heat pump, but the extra costs are worth it to me for better efficiency/annual performance factor.

If already heat pump, then brine-water heat pump. At least somewhat efficient in operation. Air-water heat pumps are exactly inefficient when the outdoor temperature is particularly low (keyword defrosting) and at the same time especially much energy is needed. Photovoltaics as large as possible with as steep a roof pitch as possible. When a lot of (heating) electricity is needed, in winter, the sun shines the shortest and is at its lowest. If then there is snow and ice on the 22* roof... Financially all expensive play, regarding investment/operating costs natural gas is unbeatable nowadays. Just makes Mr. Putin rich The best energy in the long run is the one your house doesn’t lose.

Gas was meant seriously, of course, as it is by far the cheapest and most trouble-free way to heat.

Heat pumps are still very expensive and often prone to errors. Of course, you can also be lucky and the thing runs. Durability is also a matter. Often something major is already broken after 5 to 10 years.

Air-water heat pumps and brine-water heat pumps do not differ that much in efficiency anymore.

If a heat pump and photovoltaics with battery are planned anyway, I would reconsider controlled residential ventilation and immediately go for KfW40+.