The article is opining about the deep "High Temp" thermal systems that are found in places like the Geysers field in California, in Iceland, and in New Zealand. Those use heat in a primary way to power heat engines to generate electricity.
You are talking about the other class of geothermal. That class is also known as "ground source heat pumps" for HVAC. Just like a reverse-cycle air-conditioner can heat as well as cool by exchanging heat with the outside air, ground source heat pumps do the same by exchanging heat with relatively shallow underground media. Typically, those have much higher heat capacities than air, which is the competition. Nobody attempts to run heat engines with such Low Temp resources as encountered in ground source heat pump applications...
1. I'm not sure what "if you hit rock" means there.
In general, you want to hit rock, and should hopefully hit it very quickly (40-50ft), because rock generally has much better thermal conductivity than stuff like clay.
2. You hopefully got a loop design report that has real details on the load of your house and the design of the loop and how it meets them. The loop design should hopefully tell you they are mostly drilling in rock :)
Hopefully it all does not look like nonsense (I'm happy to look at it if you like, as are the folks over at forums like geoexchange)
3. The only units you should consider are waterfurnace, climatemaster, and maybe bosch.
Trane, for years, was using rebadged waterfurnace units At least browsing, it looks like they still are.
In any case, you want someone who does this for real, and Trane ain't it.
Bosch is an okay unit, but they are newer at this, and not obviously better in any meaningful way.
4. The price for single family residential drilling is high in part because it's not what the drillers want to be doing.
The rig setup takes them quite a while, the actual drilling is not that bad.
For multi-family residential (or commercial), where they are drilling 100 holes, it's much more cost effective.
So you are right in that sense - the current way of drilling is not going to bring the cost down.
On top of that, keep in mind you are probably paying significant markup on the drilling because it's being subcontracted.
Bosch as a general rule has pretty solid engineering. I've used their kitchen appliances for years and am quite happy with them. Unlike some of the korean vendors (I'm looking at you Samsung and LG, it is easy and fast to get parts when things break).
You're right that they're new at this, but all of the existing major appliances in the home are Bosch. If you buy more than three major Bosch appliances, they'll give you a fairly sizable discount.
When I said American Standard/Trane, I meant for the Central Heating and Air, not for the Geothermal. They're the same hardware and come off of the same assembly line with different stickers on them.
I've got a lot of experience in this, and what you are being given sounds like a bunch of nonsense, and yes sometimes you will get a bunch of nonsense from more than 1 HVAC firm. Lots do not specialize in geothermal, and see it as a way they can make additional profit off some people.
Concretely: At the price you are being given, the drill price should be fixed and included, excepting them hitting lots of water.
The driller certainly gave a fixed price, based on the local geography and what they are gonna hit. The know exactly what they will hit in terms of rock/etc.
The variable cost thing is not drilling rock or whatever, it's controlling water and sediment.
If they hit lots of water (IE 100+gallons a minute), controlling and remove it can be expensive and unexpected - most cities/etc have strict rules on this (so they can't just run it into the street). This is the thing that is hard to tell for them - it's rare to have good enough data to know exactly whether and where you will hit water, and it can even vary from hole to hole in the same job.
Otherwise, be careful - unlike regular HVAC, Geothermal requires people who really know what they are doing, and not just doing the kind of "finger in the wind" HVAC you can often find for folks doing heat pumps/furnaces. At a minimum, make sure you are using IGHSPA/etc certified folks.
If you want to get more into this, there are lots of knowledgable drillers and installers over in places like the geoexchange forums, and they won't steer you wrong.
As for Bosch, the units they are offering in residential are super basic units last i looked.
They are neither variable-speed pump or variable speed compressor.
They are simply 1-2 stage geothermal units. They appear to at least offer variable speed blowers on some of them, but that's very basic stuff.
This is the kind of unit you would have seen 20 years ago. I would not pay what you are paying for them.
Nice geothermal units (say, the waterfurnace 7-series) these days have variable speed pumps and compressors. They match themselves exactly to the load needed by the house over time, and run continuously at part-load, modulating up and down as they day goes on, and end up being both silent and very high efficiency.
They are also much longer life - parts like scroll compressors (and most forms of rotary compressors) are much happier if you modulate load rather than start/stop.
You don’t want to dig an 6ft trench through rock, but you should be able to drill through it if you’re drilling 70’ boreholes.
I have a couple bosch things, but their reputation as German Engineering is no longer true in my opinion.
The price a year ago would have been more like 20k, but with the crazy price of lumber and all building materials going up, the HVAC companies followed suit :(
If I did it a year ago it would be 20k less :/
An almost 100% increase is quite substantial, no?
https://www.constructiondive.com/news/skyrocketing-steel-lum...
https://www.benningtonbanner.com/local-news/cost-of-building...
And as I mentioned elsewhere, if I installed a horizontal loop, I'd have to cut down a ton of beautiful 100 year old trees surrounding the home. I'd rather not do that when there are viable alternatives. The cost of higher electricity usage isn't a big deal as I've got 48 bifacial solar panels on the barn that run to the home.
The real killer was knowing full well the house sits on or around a ton of limestone and the best quote I got told me it would cost a lot more if they hit rock.
I've followed much of the advice in this cleantechnica series on this exact problem: https://cleantechnica.com/2020/10/08/home-efficiency-101-app...
I had a geo system installed last December (GeoComfort with 3 200 foot wells for a 120 year old, 1600 sqft house).
The system works great except that the point where the aux heat kicks in for my house is 25 degrees F. I am working this year to improve the envelope to reduce the need for aux heat.
For horizontal or vertical geothermal loops, the biggest cost is always going to be digging for the loops. Until they make that more affordable, they're going to have a hard time making it more ubiquitous.