ᐅ Comparison of Geothermal Heat Pump and Air-to-Water Heat Pump

I double-checked the invoice. People often report from memory, so I looked up the actual figures again.
The total was €8049.16, fully turnkey—including all paperwork, disposal of drilling water, trenching, house connection, insurance, and so on.
120m (394 feet) as a single probe, already including a 10m (33 feet) safety margin, with improved grouting material.

Minus €5000 BAFA subsidy, minus €1200 funding in NRW (at €10 per meter).
So, that leaves an additional cost of about €1800, although that’s not entirely accurate since you save the costs for the heat source of an air-to-water heat pump (costs for the outdoor unit with foundation, piping, labor).

All in all, the brine-water heat pump with drilling was still slightly more expensive, but not by much. The costs were so close that just avoiding the outdoor unit justified the extra expense. Plus, there are options like passive cooling, a heat source that (hopefully) will outlast us and never needs replacing, and no risk of noise complaints from neighbors, and so on.

BUT: This depends on the location. We also built with architects and I was able to choose all the contractors myself. Of course, I also spoke with idiots who gave a blanket offer of €20,000 for the drilling. Obviously, you don’t take that. Anyone building with a general contractor and tied to a single heating specialist will have to accept whatever is offered or opt for the air-to-water heat pump instead. In some regions, this might not even be approved by the authorities (building permit / planning permission), so there really isn’t one absolute truth on this topic.

guckuck2 schrieb:

I double-checked the invoice. People often report from memory, so I looked up the actual figures again.
It was €8049.16. Fully turnkey, including paperwork, disposal of drilling water, excavation, house entry, insurance, and so on.
120m (400 feet) as a single probe, already including a 10m (33 feet) safety margin with improved plugging material.

Minus €5000 BAFA subsidy, minus €1200 funding in NRW (10€ per meter).
That leaves an additional cost of about €1800, although that’s not entirely accurate because you save the cost of the heat source for the air-to-water heat pump (costs of the outdoor unit with foundation, piping, labor costs).

So overall, the brine-to-water heat pump with drilling was still slightly more expensive, but not by much. The costs were close enough that simply avoiding the outdoor unit justified the extra expense. Plus options like passive cooling, a heat source that (hopefully) lasts longer and never needs replacing, and no risk of noise issues with neighbors...

BUT: This depends on the location. We also worked with architects and I was able to choose all service providers myself. Of course, I also talked to idiots who offered drilling for €20,000 flat. You obviously don’t accept that. If you build with a general contractor and are tied to one heating specialist, you take what they offer, or you go for an air-to-water heat pump... Regional restrictions might also prevent approval, so there really is no one absolute truth on this topic.

The subsidy has now increased to 35% (for all brine-to-water heat pump costs). I’ve also heard from many general contractors about €8,000 in additional costs, which seems reasonable. You get roughly €4,000 more in subsidies, so that would mean about a €4,000 net extra cost.

Everything is changing. For us, there was still a fixed subsidy from BAFA, but there was no support at all for the air-to-water heat pump, or the criteria were realistically not achievable.

And as I said, the €8000 (about $8800) was the cost for the drilling, not the additional cost for the entire system. That is lower, since only the heat pump itself costs the same amount, but the heat source for an air-to-water heat pump is naturally included at no extra cost.
Hypothetical example:
The heat pump with accessories and installation costs €8000 (about $8800) in both cases. For the ground-source heat pump, an additional €8000 (about $8800) for the turnkey drilling is added, while for the air-to-water heat pump, it is €2000 (about $2200) for the outdoor unit. The difference is then €6000 (about $6600).

However, this is not the case with monoblock units, and air-to-water heat pumps are now also eligible for subsidies. But yes, if I had been allowed, I would have seriously considered it as well.

guckuck2 schrieb:

I double-checked the calculation. Since people often report from memory, I looked up the exact figures again.
It was €8049.16, fully turnkey, including all paperwork, disposal of drilling water, trenching, building entry, insurance, etc.
120m as a single probe, already including a 10m safety margin, with improved grout material.

Minus €5000 BAFA grant, minus €1200 subsidy in NRW (10€ per meter).
So that’s an additional cost of around €1800, although that’s not quite accurate because you save the cost of the heat source for the air-to-water heat pump (costs for the outdoor unit with foundation, piping, labor).

In the end, the brine-to-water heat pump with drilling was still slightly more expensive but not by much. The prices were so close that even just avoiding an outdoor unit justified the extra cost. Plus options like passive cooling, a heat source that (hopefully) will last us a lifetime and never needs replacing. No risk of noise complaints from neighbors, …

BUT: this depends on the location. We also worked with architects and I could choose all the contractors myself. Of course, I also spoke with idiots who included a drilling price of €20,000 in their offer. Naturally, those offers were rejected. If you work with a general contractor and are tied to one heating specialist, you take what’s offered or prefer an air-to-water heat pump… Regionally, this might not even be permitted, etc., so there isn’t one single absolute truth on this topic.

I have no further questions about the numbers. Such a small additional cost would be completely acceptable for me! Thanks for checking. As you said, elsewhere contractors completely inflate the prices for drilling.

Joedreck schrieb:

I have no more questions about the numbers. Such a small surcharge is absolutely acceptable to me! Thanks for checking. Because as you said, contractors elsewhere completely flip out over the drilling prices.

Glad to help.

Those who flip out are the ones who don’t really understand it. You can only make a valid offer if you invest a bit upfront to calculate accurately. That was also the case with the guy quoting €20,000. He was a heating engineer who only rarely installs brine-to-water heat pumps with drilling (like most do), but wanted to offer both from one source. It already started with the heat pump being oversized. I think it was a Vaillant with 8 or 9 kW he offered. If he then looks for a drilling company “just to quickly” get a price based on that size... and adds a safety margin because he doesn’t really know what he’s doing, well, then you end up with those high defensive prices.

The second heating engineer, who eventually got the job, also started with incorrect heating load calculations. For example, he didn’t want to accept that ventilation with heat recovery had to be considered, saying “that hardly makes a difference.” But in well-insulated buildings (energy efficiency class KF 55) it definitely makes a difference nowadays. Suddenly the heat pump was only 6 kW, the borehole was shallower... I commissioned the drilling separately and requested quotes from two companies. Both obtained official data on the geothermal yield from the authorities to calculate correctly. Both gave almost identical offers, and I then made a gut-feeling decision (both had already worked successfully in this new development area).

Oh yes, another hurdle with some providers is the 100 m (330 ft) limit. There is this rumor that you can’t drill deeper than 100 meters. Complete nonsense. It may apply locally, for example if there is a layer at a certain depth that is not allowed to be penetrated.
The truth is that the application process takes longer, because after 100 meters mining law has to be taken into account. Then the application from the lower water authority goes on to the mining authority (or whatever it’s called) and to the federal office responsible for searching atomic waste repositories (they give the approval that no nuclear waste is to be stored at that location ). The application procedure took about six months.
But it’s possible and saves a lot of money, because it’s better to drill once at 120 meters (395 ft) than twice at 70 meters (230 ft). Every meter of drilling costs money.
Also, multiple probes have to be connected, which again adds costs. Setting up the drilling site twice also costs extra money, which you can avoid.
In return, operating costs might be slightly higher due to the circulating pump having to work a bit harder at that depth.