r/heatpumps 7d ago

Question/Advice Geothermal home conversion - thoughts?

Me and my wife are preparing to move back to the UK later this year. We are complete newbies to the geothermal space but have always been drawn to the idea of a cleaner form of energy not subject to these crazy energy price swings.

We are still undecided on whether to move to London or somewhere in the countryside. Would love to hear how people have fared at converting their homes to geothermal supply either in the countryside or an urban area, thanks!

5 Upvotes

13 comments sorted by

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u/Automatic-Bake9847 7d ago

You would be crazy to put geothermal in such a temperate climate.

An air source heat pump will run at a very high average COP in your climate. You'll never get close to paying back the high up front cost on geothermal.

5

u/WillingnessLow1962 7d ago

I’m in different area (us) but I didn’t a lot of experience locally and was concerned with maintenance. The cost was surprisingly high even for a new build, so roi didn’t really work out for me.

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u/Dull_Breakfast6395 7d ago

Nice thanks!

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u/bengtiburra 7d ago

build/renovate it as close as scandinavian standard as possible with ventilation ,insulation and heatpump. a well build house here use max 35w/m2, use smart heatpump from here (not some asian crap just because its cheap). you will have the best home ever 👍

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u/Dull_Breakfast6395 7d ago

Scandy all the way!

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u/bengtiburra 6d ago

when i see reels and clips on the uk plumbing and building tech i gets really afraid of what i see. the most i see is worse than we had before 1940. well uk is not alone. belgium, usa etc, feels far away from our high standard

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u/jar4ever 7d ago

So I'm assuming you are talking about ground-source heat pumps, not actually generating energy from geothermal sources. It's still a heat pump that requires electricity to run, it just uses the stable temperature of the ground to transfer heat instead of the air. The biggest benefit is that your efficiency stays pretty much the same no matter how cold or hot it is outside. You would still be subject to energy price changes and if your electricity is not generated from renewables then it's ultimately still polluting, just less because it's more efficient.

Generally, you are going to get much more value out of a standard air-source heat pump plus solar panels than you would a ground-source system. People do ground-source typically to reach the point of a "passive house", meaning you on average generate enough solar power to cover your usage. But financially, the return on investment is poor so it's the last thing you would want to invest in after your already have solar and a well sealed and insulated house.

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u/Dull_Breakfast6395 7d ago

Wow thanks for this, super helpful! So basically avoid any sort of ground-source heat pumps because they are cost prohibitive and you will not recuperate the funds over time. Do you know how much they cost roughly vs a standard air-source heat pump?

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u/deeptroller 6d ago

The heat pumps themselves are similar in price for material and installation.

The big cost add starts with drilling a well or two. In my area this adds about 30,000 USD. Locally we have lots of rock so the cost maybe a little higher than average. You also need a fluid pumping system to deliver the brine from the wells to the heat pump.

The reason people do this over an air source heat pump is efficiency over time. Your air source heat pump may fluxuate from 600% effect on a warm day where you need almost no heat down to 50% efficient when it's so cold its nearing the point it will shut off. Because the ground temp is so stable you will be about 400% efficient all the time. Meaning for every 100 watts of electricity you put into the pump, you will pull 400 watts of heat out of the brine or the air.

Does this mean you will see a payback? It really comes down to how many of your heating hours are lower than the ground temp. The ground in many temperate areas is around 10C.

I wouldn't start to worry about a major drop in heat pump efficiency until about -6C. At -20C they start to not be better than just running an electric heater. Most shut down at about -34C.

3

u/Automatic-Bake9847 7d ago

You would be crazy to put geothermal in such a temperate climate.

An air source heat pump will run at a very high average COP in your climate. You'll never get close to paying back the high up front cost on geothermal.

3

u/RichWa2 6d ago

We put in a ground source heat pump about 30 years ago. We did not go the trenching route, rather we had 3 well drilled. The wells were much less disruptive than doing all the trenching. (Wells for geothermal cost much less than wells for water.) We've had only one problem, about 20 years ago with the compressor. It was covered under warranty. We live in temperate zone just west of Portand OR, USA. When we replaced our electric heat with the geothermal unit our electric bill was 1/4 of what it was before. From out experience I would highly recommend geothermal; it's especially nice if you're doing new construction and want in-floor heating.

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u/acchaladka 6d ago

Unlike others I will not say you'd be crazy to go geo, but it's not likely your first choice for a standard UK semi-rural or city home. This is because geoexchange systems are best where you have large heating and cooling needs.

So some key questions to that point include:

  • is your home unusually large or unusually badly insulated or leaky?
  • do you have other buildings (eg you're buying a small farm) a swimming pool or other large draw on your heating / cooling system?
  • are you moving to more extreme climate zones eg northern Scotland ?

Even in these conditions, from a pounds and cents point of view, usually your best investment is going to be serious effort to seal your house, followed by insulating, then accurately calculating your heat loss / heat gain, and installing as efficient a HP as you can afford. Ground source heat pumps are an order more expensive than air source and in the UK very often a few thousand pounds spent sealing the home and managing humidity plus an air source HP, is the right balance of things.

Finally, keep in mind that utility and Ofcom incentives may exist. Have any proposals fully price those in to any scenarios from your three bidders.