Experiences with brine heat pump

There is often a lot written and little substantiated in forums, unfortunately. I just checked again; when I compared the providers a few years ago, the geothermal drilling plus the connections would have cost 18,000 euros. The air heat pump cost 13,000 less after subsidies. Thus, the payback period for geothermal energy was about 30 years. We then decided against it and have not regretted it so far.

I contacted 4 companies back then; their prices were not much different, so I think either it has become much cheaper in the meantime (what would actually get cheaper?), people only post half the information (very likely), or it varies greatly regionally (possible).

or there are people who are biased and do not acknowledge differing opinions, insights, and facts. I, and I think the others above as well, provide absolutely true numbers. You have substantiated less than we did but generalized much more (and your numbers above: comparing an air-to-air heat pump with subsidies to a brine-to-water heat pump without subsidies is also not quite fair). I have disclosed all the numbers for the entire construction project here. Will you only believe it if I send you the invoices?

We built in 2009.
Between the then kfw60-40 standard.
Heat demand approximately 12,000 kWh.

Electricity price at that time around 15 cents/kWh.

Offer for geothermal drilling around €13,000, whereby the drilling meters were based on a heating load estimate.
The first offered air heat pump was supposed to have 12 kW heating capacity.

That seemed way too high to me.
Consequently, we had a heating load calculation made by an engineering office.
Design temperature -14 degrees.
Heating load without basement just under 6.5 kW.
With heating of our party / hobby basement room just under 8 kW.

Due to the supposedly high drilling costs (which were based on 12 kW heating capacity), we opted for a smaller Stiebel air heat pump.

Unfortunately, this air heat pump + its hydraulics were poorly installed.

Electricity consumption: 4,000-4,500 kWh (annual performance factor 2.8)

A brine heat pump would have easily achieved an annual performance factor of 4-4.5 even with "poor" installation.
The drilling costs for 6 kW would have been only about €10,000. The geothermal heat pump itself would have cost almost €2,000 less. Real additional cost for the geothermal heat pump therefore rather €8,000.

Electricity consumption with geothermal heat pump and an annual performance factor of 4.5:
12,000 kWh : 4.5 = 2,666 kWh. And that compared to our air heat pump demand of 4,000-4,500 kWh.
That means additional electricity costs to date: annually €330...

The electricity price that served as the basis for our decision for the air heat pump has increased from 14-15 cents by almost 80% to 25 cents today.

At the end of the day, we are self-critical and would not choose it again due to the negative experiences with our air heat pump.

The heating engineers are not interested in building an efficient heat pump system. Hydraulics, design of the underfloor heating, hydraulic balancing, no buffer tank, no individual room controls,... all topics that a heating engineer just installs "as usual."
And here lies our problem with our air heat pump. A brine heat pump is "more grateful" due to the constant source temperature than an air heat pump with low outdoor temperatures in winter.

The air heat pumps that you get from the usual heating engineer are unfortunately mostly just "standard" in terms of efficiency.

The best models unfortunately still come from the Far East (Panasonic, Mitsubishi, Daikin) – but a normal heating engineer does not install Daikin.

Due to the currently very good BAFA subsidy, I would clearly go for geothermal today.

Where do you all live or do you have to drill through Obsidian? Our 100 drilling meters cost around 5000 euros.

An annual performance factor of 2.8 is really terrible for a modern air heat pump system. We operate at 3.5 and as you write, a geothermal system would have 4.5+ I think.

The drilling you mentioned is of course interesting, which company was that?

Maybe we really had "bad luck" back then and asked the most expensive provider for the drilling. The other providers were only different heat pump manufacturers. I was mistaken there, after the first offer from Baugrund Süd I didn't compare anymore, I thought they were all similarly expensive. Maybe my mistake!

Well, it’s all behind us now and we are satisfied with the air heat pump, but that topic occupied me a lot back then.

Where do you all live or do you have to drill through obsidian? Our 100 meters of drilling cost around 5000 euros.

Maybe it depends on the package (see my first post here). Also funny: it depends a lot on the drilling company. My neighbor, who was the last to build here, couldn’t get a bore hole done directly on the neighboring plot (the companies "could" only do water flushing). Maybe that’s why I didn’t have the cheapest, but in the end a drilling company that was affordable for me. Annual performance factor: but many factors come into play (location, hot water, heating and ventilation behavior). I know many who have, for example, lost quite a bit of annual performance factor due to hot water and "carelessness," but most don’t care ("those few euros"). Still – there are databases on the internet with info about heat pumps in real operation (with many hundreds of devices) – for air-to-air heat pumps, 3.5 is already an absolute top value. Therefore, your comment about "really terrible" is quite an exaggeration. Just look at the data for performance factors for hot water alone, or for heating flow at about 35° with subzero temperatures. Apart from that, do you have a heat meter? I have optimized for my brine heat pump here and thanks to fortunate drilling, even after 2 months below 0° outside temperature, I still have about 5°+ brine inlet temperature, so my brine heat pump always runs with a performance factor >5. And it is precisely those 2-3 months of the year that account for two-thirds of the entire annual heating AND hot water costs for me.

Maybe it depends on the package (see my first post here).

(Probably more on the region and the underground)

Yes, certainly there are differences, but with us, proper drilling was done, not flushing, piping to the house, pressure tested, specially pressed (due to the water protection area), filled, and all the bureaucratic madness of the authority was satisfied. I don't know what else would have to be in such a package for it to be "worth more." But it doesn't help at all. I just wanted to throw a counterweight to the 13,000 or 15,000 euros mentioned here.