In the nordics it is common to have ground source heat pumps (brine in closed circuit pipe or bore hole) that are run backwards in summer to cool the house while actually assisting in storing heat back in the ground to extract in the winter. It’s a bit like regenerative breaking on electric cars.

There was a new in 1988 house in Champaign, Illinois, USA that used the same system, and i mention that because it was a normal modern house, and it's the only one i've heard of with that system.

It seems so smart.

It's expensive. A relative has one in the northern Great Lakes, they wouldn't have installed it if their house had access to natural gas.

Our house came with one and we upgraded the unit a few years ago. It's very efficient in terms of units of energy consumed, but in my area of the world gas is significantly cheaper than electricity so it ends up being expensive to run.

That said, we will install solar at some point and then it'll be "free" HVAC.

There's a pretty significant upfront cost in getting them drilled, and many homes need the vertical drilling if they don't have sufficient yard space for a horizontal system. It gets harder if you have your own septic drain field too, as that will complete for yard space.

The cost difference is pretty massive- 3-10x for a vertical system. If you live in a city or a suburb with tiny lots, that's your only option though.

Nat gas and central AC are way cheaper.

Air source heat pumps are insanely more efficient and just plain better these days too. It used to be that if the air was below 40F you couldn't heat your house with a heat pump. Now, you can heat your house even when it's -10F

If you can tolerate the price, I am _confident_ that you will pretty much always have better results using the Earth as your thermal exhaust, because you don't have to dig very far to find a large region that's pretty much always at 50 F.

The downvotes are unfair.

The price of things - heat pumps and alternatives - in different regions - even different regions within the US - varies by what people are prepared to pay not what they cost to produce.

The nordics have traditionally had cheap heat pumps whereas piped gas is only in the biggest cities and I’ve never seen bottled gas in the countryside. The competitor used to be cheap electricity and wood. Ground source heat pumps for rural install have been priced to compete with wood.

In the US the market could be shaped by regulation and taxation etc. It’s the choice of the US to have cheap fossil fuels and not embrace tech instead.

> Air source heat pumps are insanely more efficient

Citation needed?

Efficient how? I'm sure a heat pump designed for a narrow range of input temperatures AND working with water which can transport a lot more heat should easily be more efficient.

https://www.energysage.com/heat-pumps/compare-air-source-geo... Seems to disagree

I assuming he means insanely more efficient than they used to be, not more efficient than ground-source (awkward wording though). I suppose they can also be described as more efficient in installation time, cost and equipment than ground source, but clearly not in operating efficiency.

Yes air source are really good value in cost effectiveness terms, especially when a house has an existing central heating system they can connect to. But their COP - whilst dramatically improving in the last 10-20 years - is still behind ground source, particularly in the north during winter

Although if you needed a new septic field, I would think ground source thermal would be significantly deeper than a drain field which is only like a foot or so down so you could stack them.

I paid about EUR 4500 for a 114 meter drill hole including installation of brine (ethanol in my case actually) and removal of spoils. My 8kW heat+water pump was about EUR 7000.

I can spec out a gas burner for about EUR 4000 and a central AC for EUR 5000, but I bet the efficiency of the ground source heater would quickly trump the cost of buying gas regularly.

That's insanely cheap compared to what we can get around here. Most installs I've heard of from people in the US are in the $20-50,000 range, depending on the size of their home and number of wells needed.

Yet it did not feel very cheap to me. The price of the pump had increased from 4800 only a year earlier due to the war in Ukraine.

There were a number of steps I had to go through. First I had to file for permission at the County Office, where they verify that drilling in the area is acceptable and that the intended pump follows regulations with respect to cooling media, and that the drilling company was certified to drill for my needs. It did cost about 70 euros.

I needed effective zero plumbing work in the house as it was already prepared to accept heating from a pump like that. Perhaps that is one of the major costs in USA?

I don’t know what’s going on with this kind of stuff in the US - similarly I’ve heard stories of people getting quotes in the States for anything from US$10-15K for the kind of air source mini-split heat pumps you can have supplied and installed for US $1200-2000 in Australia! (That is ~3.5 to 7 kW range - super common and cheap as chips here).

Can't prove it, but it seems vendors collude in (very hot) Arizona on all sorts of necessities (plumbing, A/C, electricians). they all seem to know what each charges, and the prices seem not kept in check by any real competition.

No it's not. It exists but it's certainly not common for individual dwelling to use ground source heat pumps, at least in Norway. It is more common in Sweden[1] but still far less common than air source and over 90% of heat pump installations in Norway are air source[2].

The only ground source installations I can think of in Norway serve large office buildings and similar. The largest heat pump installation I know of in Norway is actually a third kind: water source[3]. It takes heat from the Drammen river to provide heat for a district heating system and for keeping the town centre clear of ice in the winter as well as supplying the new hospital with heat.

I imagine that the rest of the Nordic region is similar.

See:

[1] http://publications.jrc.ec.europa.eu/repository/bitstream/JR...

[2] https://www.sciencedirect.com/science/article/pii/S221313882...

[3] https://energiteknikk.net/2023/11/drammen-fjernvarme-storst-...

In Finland around 50% of new single-family homes use ground source heat pumps. So it's definitely popular here.

3 schools in my neighborhood (barneskole, ungdomsskole & videregående) all use ground source heat pumps.

If by Nordics you mean Norway, Sweden and Finland, then the most correct way to say would be that ground source heat pumps for redidential heating are (very) common in Sweden and Finland, especially in newer and larger buildings. Norway is somewhat different in energy and climate perspective than its eastern neighbours.

The biggest reason to not install ground source heat pump is high installation cost. This means that it makes more sense for larger residential buildings. Also If you have district heating available then this might be more economical in the long run.

Shallow geothermal works fine for heating. And you can use the ground as a heat sink. But if you want to generate power, you need to get down to where temperatures can boil water. That's deeper than most oil wells. Fervo Energy claims to have found 270C at 3350 meters well depth. That's progress.

> if you want to generate power, you need to get down to where temperatures can boil water. That's deeper than most oil wells.

That’s going to be very dependant on location.

Here in NZ there are regions where water is boiling at surface level.

According to the below, 18% of our power is produced with it.

https://www.eeca.govt.nz/insights/energy-in-new-zealand/rene...

"New Zealand has an abundant supply of geothermal energy because we are located on the boundary between two tectonic plates. ... Total geothermal electricity capacity in New Zealand stands at over 900 MW, making us the fifth largest generator of geothermal in the world. It has been estimated that there is sufficient geothermal resource for another 1,000 MW of electricity generation."

That's not all that much. That total would be about equal to the 75th largest nuclear plant in the world.

Good sites where high temperatures are near the surface are rare. California has a few, but no promising locations for more.

> That's not all that much.

We don’t have many people. It gets worse’s though, we burn coal and are looking to fund a gas terminal. We have abundant other ways of generating power and subsidise an aluminium smelter for some reason.

Coming up next, data centres.

‘Clean, Green New Zealand.’

Is there any earthquake risk from drilling near tectonic plates?

> That's not all that much

May not be much in world terms but here in NZ national demand maxes out at around 5.5GW so bringing another GW on stream would be quite handy. Most of the geothermal is a lot closer to Auckland* than our hydro is so so that would be another positive aspect.

* Auckland has 25% of the population so a corresponding amount of energy has to be pushed its way.

>no promising locations for more.

Isn't there a super volcano in the middle of the country? Maybe there are some adjacent hot spots outside of the national park?

https://en.wikipedia.org/wiki/Yellowstone_National_Park

You brought the conversation in a circle, since the point of this new technology is the geology you speak of is rare.

There are also places in the US with boiling water at the surface. I live near one of those places so always curious about geothermal. There's a spot near my house in a creek bed where snow always melts even in deep winter so apparently I have some potential heat source. Our well water is cold though.

Not near me, but hot water spring, rivers and beaches made for a nice soak every now and again.

Turning them all into power plants would be a shame, but there is plenty of space for both.

You don't necessarily have to choose one or the other. The Blue lagoon in Iceland is a famous example. The water comes from a power plant nearby.

You're not required to site them that close either, because of how regional the conditions usually are. A couple miles plus or minus doesn't change things too much.

I think this looks interesting, but still very early stage. The “150 GW revolution” sounds more like theoretical potential, not something we will see soon in real deployment.

Main problems: drilling is still expensive, managing induced seismic activity is not trivial, permitting can take long time, and you also need transmission infrastructure. Also not yet proven that companies like Fervo can scale this in reliable and low-cost way.

Nope. To efficiently tap geothermal energy, you need to boil something but not necessarily water. Isopentane, for example, boils at 28º at standard pressure, so they pressurize the secondary loop to raise the boiling point close to whatever the primary loop temperature is.

The idea that geothermal only works well at steam temperatures is outdated 20th-century thinking.

But the energy in boiling isopentane would be less right?

Yes, the efficiency is worse, but as is also the case for solar power you need to get used to not caring much about efficiency. It is nuclear energy where the primary side is provided free of charge. The Carnot efficiency is almost without relevance.

In geothermal there is still a lot of interest in efficiency and exploring different working fluids because binary systems now have efficiencies of 10-20%. That is why you see companies like Sage Geosystems working on developing / deploying supercritical CO2 turbines to try and boost practical power densities.

> But if you want to generate power, you need to get down to where temperatures can boil water.

Why is that the case? Can't you go down to where it's like 70-80 deg C and close the gap using heat pumps? Yes, you need to put some energy in, but I would expect that the whole process would still be energy-positive at some temperature that's lower than 100C?

There are so many ways around this - for a start, you can use some other working fluid that boils at a lower temperature. Or you can choose a different thermodynamic cycle that doesn't involve phase change.

Framingham, MA has a geothermal system using ground source heat pumps like what you are describing

https://www.smartcitiesdive.com/news/first-networked-geother...

I think you're describing what is known as "district energy" systems.

District heating and chilled water is uneconomical for single-family homes. It does work well in medium to high density areas.

I don't know how economical that is, but just as an anecdote - the town I'm from in Poland has district heating to all single family homes, town of about 20k people. And coincidentally, I now live in the UK and a new estate near me has district heating to all the houses they are building, not apartment blocks. So it must make some sense to someone, or they wouldn't be outfitting 100+ houses this way.

"I don't know how economical that is"

Sure you do. Think about it. Its just drilling a hole and making electricity from the heat. We have been able to do this for a very long time. So if people aren't really doing it much, its not economical. If it was now becoming economical, the article would describe some new way of doing it that makes it economical. The article doesn't, so you "know" it isn't.

PS This has been tried many time, it only works in very specific situations, usually places where building a full PP doesn't make sense or where you are making a lot of electricity for some other purpose (mining usually).

The “new” way is plasma drilling.

That's still a science project, they are piloting zapping a small hole to 100m. Very uncertain whether it will amount to anything.

> Its just drilling a hole and making electricity from the heat

District heating does not involve making electricity.

Sometimes district heating and electricity generation does combine though:

> Wärtsilä’s combined power generation and heat recovery plant offering comprises solutions for combined heat and power (CHP) including dynamic district heating (DDH), district cooling and power (DCAP) and trigeneration for applications that require both heating and cooling.

https://www.wartsila.com/energy/engine-power-plant-solutions...

Not always, but as the sibling noted, there are plenty of combined heat and power plants. They recover as much of the energy as possible from the exhaust gas streams and run pretty efficiently.

>>Sure you do. Think about it. Its just drilling a hole and making electricity from the heat

...what? What does that have to do with district heating? The one in Poland is coal fired, the one in the UK is electric.

At least in parts of Eastern Europe (especially the former GDR) district heating systems were introduced as a response to the oil crises of the 70s, resulting price shocks and the transport of coal to households being very labor and resource incentive [1].

[1] https://www.ndr.de/geschichte/schauplaetze/Windkraft-und-Erd...

It’s uneconomical in an already built out area or a non central planned economy, and also the US is special case since we have dirt cheap natural gas that is used for heating.

Digging up streets to run distribution lines, running service drops to every existing house, installing a heat exchanger and valves in every house is astronomically expensive given the amount of energy used by a single residence.

If you’re building out a new neighborhood on a greenspace plot, installing the district heating/cooling piping is much cheaper since you’re already laying electric, water, sewer, and mane gas lines.

> It’s uneconomical in an already built out area or a non central planned economy

I mean, true. But it was new developments I had in mind for a neighborhood geo install.

Isn't that similar to how neighborhood heat pumps work?

https://www.araner.com/blog/district-heating-in-sweden-effic...

Heat pumps require a specific temperate differential to work. So they work in zones with are a bit hotter or colder than you would like and so require moderate amounts of heating or cooling. They don't work in temperate zones nor in very hot or cold places. So Santa Fe or Minneapolis for example they work but Mexico City or San Francisco they don't. If you are in a place where they work and that isn't too dense or has earthquakes, go for it. If not, don't. There are businesses that will help you understand when they do and don't make sense. Those businesses don't sell heat pumps though (the businesses that sell things will almost always tell you it works, even when it doesn't, for example PV in the UK doesn't work).

> pv in the UK doesn't work

tell that to 6% of UK electric production https://www.bbc.com/news/articles/cz947djd3d3o (up from 5% in 2024

Solar is surprisingly useful in the UK since it is anti-correlated with wind power, the UK's largest electricity source.

Solar peaked at 42% of UK electricity generation the other day:

https://www.pv-magazine.com/2026/04/24/uk-solar-generation-h...

I’ve never heard a claim that heat pumps won’t work well in a climate like San Francisco and, from looking at the annual temperature patterns, it seems like both air source and ground source heat pumps should work extremely well as they do in the “shoulder seasons” here in New England.

Wait Minneapolis is definitely very cold for about half the year.

Heat pumps have gotten a lot better, you need a pretty extreme climate for them to start to struggle, even the air-source ones.

(And PV works well enough in the UK for it to be a no-brainer to put on residentials roofs, which is on the whole the most expensive way to deploy it. Though this is in large part due to the way that it competes with retail prices and not wholesale prices)

This is nonsense, heat pumps are more efficient at smaller temperature differentials. I suspect we don't see them much in San Francisco only because there is so little need for heating and cooling the potential savings are smaller.

Whisper Valley in Austin Texas is one example of a neighborhood geothermal installation: https://www.canarymedia.com/articles/geothermal/texas-whispe...

Maybe not quite exactly what you envision.

> Maybe not quite exactly what you envision.

I'm too zonked to pick out the method from the article - but I'll offer that geo methods can be region specific. What I described fits the SE US, with our 13 month summers and abundant underground water.

13 month summers lol :) Yeah, definitely if your interested neighborhood geothermal Whisper Valley seems to be the largest by far in the US, you might check it out.

One of the problems with the data center boom is its use of fresh water. How does geo-thermal plants use water and how much?

The water at these temperature / depths has a lot of dissolved salts and minerals so it's not (human / ag) usable. Modern designs are closed loop systems where production wells bringing the hot water to the surface go through a heat exchanger to a different working fluid to drive the turbine and then is re-injected back into the reservoir. There is consumptive water use for fracking the reservoirs in these types of enhanced geothermal systems, but beyond that it's more water redistribution in the area around the well systems where re-injection and production lead to different pressurization from pumping / natural ground water replenishment rates.

> The water at these temperature / depths has a lot of dissolved salts and minerals so it's not (human / ag) usable.

To clarify, our 400' water source is the same aquifer that supplies drinking water to the state.

The water management districts will rubber-stamp permits for these wells. No one else gets off that easy.

> One of the problems with the data center boom is its use of fresh water. How does geo-thermal plants use water and how much?

Baring leaks, ground source heat pump geo will consume no water at all. Water is pumped from one layer of the aquifer and is returned to a slightly higher layer.

I dont know why this keeps coming up? It is a closed loop system. The water aren't used at all.

Many data centers use evaporative cooling.

It's a closed loop on the geo side sure.

How do you cool the steam off enough to condense so it can go and be boiler feed water again?

Lots of power plants use cooling towers for this which are typically evaporative. Some are dry, sure, but most are wet.

> It is a closed loop system. The water aren't used at all.

Our method is open on both ends. It draws from one layer of the aquifer and then returns the water to an adjacent layer.

> I always thought this method could be used to provide a/c for neighborhoods, operated as a neighborhood utility. I've not seen it done tho. I've seen neighborhood owned water supplies and sewer systems; it tells me the ownership part seems feasible.

I keep thinking this would be a great municipal code change: any time the roads are being built or ripped up for water/sewer maintenance, put in a ground loop and subsidize household connections for heat pumps so instead of having to deal with the marginal difference between 20℉ winter air you'd be working with 50-60℉ ground temperatures.

> The systems I worked on were for cooling larger structures like commercial greenhouses, gov installations and mansions. 64° degree water would be pumped up from 400' down, run thru a series of chillers (for a/c) and then returned underground - about 20° or 25° warmer.

I read this several times in the context of _geothermal_ energy, and had no clue what you were talking about.

Then I realised, you must be an American and use 'freedom units', coupled with a misunderstanding of what geothermal means.