180m borehole cost per metre for ground source heat pump

[Strak]

Hi all, I've had a heat loss survey done for my house which is undergoing renovation. Heat loss is estimated at approximately 6kw. Looking at ground source heat pump as a heating option, but we only have space to drill straight down rather than lay horizontally. The different vendors I've spoken to so far have estimated a 180m borehole for this and I'm trying to figure out how much this is likely to cost.

 

Any ideas on cost per metre for drilling a borehole to help with budgeting? Would there likely be any cost advantage to me shopping around and arranging the drilling of the borehole separately to the heating company?

 

Thanks!

[Redoctober]

I have no experience on this matter but a quick internet search will give you a very rough expectation I'm sure.

 

That said, I have to say, 180 metres down! Is that correct? Surley you would expect to hit water long before then?

 

Is this your only option regarding a heating supply?  If not, then you would have to weigh up the capital outlay against any gains long term.

 

[joe90]

Are you not considering an ASHP?

[JohnMo]

10 minutes ago, Strak said:

6kw. Looking at ground source heat pump as a heating option

Why? ASHP simple to install zero issues at -10 this year.

 

We have a water bore hole about 45m deep, due to us being on a sand hill, nearly all the drilling money went on steel liners for the bore to stop collapsing. So really depends on on what they find - once you start you can't stop and you just have to pay the bill. If your rock for 10m they could be drilling for weeks 

Edited April 25 by JohnMo

[Alan Ambrose]

Suggest yes, because (a) the drilling will be done by a specialist company anyway, there will probably only be a few in your area, (b) we should all have the discipline to get multiple quotes, especially for big items, (c) the local drillers will have experience in the ground in your area which may be super useful info.

 

Sounds a deep hole. Know what kind of ground you're on? Looked to see whether there are any BGS records close to your area?

 

I think the BH hive mind generally doesn't lean towards ground source. Someone will be along shortly to ask why not air...oh, I see I'm too late already.

Edited April 25 by Alan Ambrose

[Strak]

3 minutes ago, JohnMo said:

Why? ASHP simple to install zero issues at -10 this year.

 

Mainly for the more consistent energy bill, and passive cooling in the summer. I am looking at ASHP as an option too though. Did you notice a significant drop in efficiency at -10, and did it get noisy at all?

[joe90]

From my reading a downside of a GSHP is the compressor being indoors (noise) and brine costs.

6 minutes ago, Strak said:

and passive cooling in the summer.

Some/most ASHP,s can do passive cooling.

[Kelvin]

 

14 minutes ago, Strak said:

 

Mainly for the more consistent energy bill, and passive cooling in the summer. I am looking at ASHP as an option too though. Did you notice a significant drop in efficiency at -10, and did it get noisy at all?

£100/m minimum I’d expect. What makes you believe an ASHP can’t offer consistent bills and passive cooling. They can do both. Spend the saved money on making your house as airtight as possible and is well insulated. That’s the best way to reduce bills. 
 

A correctly installed ASHP is pretty quiet in reality. Ours is more quiet than our neighbour’s wheezing oil boiler flue. Also how often and for how long do we have such low temperatures. 
 

I had a spare free 137m borehole and still fitted an ASHP. 

Edited April 25 by Kelvin

[Strak]

On 25/04/2024 at 11:24, Alan Ambrose said:

Sounds a deep hole. Know what kind of ground you're on? Looked to see whether there are any BGS records close to your area?

 

I have no experience with this type of thing to know how much it is likely to vary in a small area, but the closest deep BGS hole I can find is about half a mile from me. The hole is 102 metres with this makeup:

 

Built up ground: 1 metre

Grey/white soft chalk: 14 metres

Green clay: 37 metres

Green sands: 2 metres

Gritty black/grey mudstone: 19 metres

Gritty clay some hard horizons: 29 metres

 

Survey scan link: (removed as it shares personal information)

 

There are some 50m holes in the opposite direction but they are much older and the scans are harder to read, but they also mention clay, chalk and green sands.

 

 

Edited April 27 by Nickfromwales
Link removed

[JohnMo]

45 minutes ago, Strak said:

Did you notice a significant drop in efficiency at -10, and did it get noisy at all?

Does drop a little, and you need more heat anyway - you still get a CoP of about 2.7, for the day you are down to that level. At -2 you are mid 3 and at 7 degrees, 4.5 for CoP.

 

Noise don't really notice as the heat pump is behind the shed.

[Strak]

30 minutes ago, Kelvin said:

What makes you believe an ASHP can’t offer consistent bills and passive cooling.

 

I'm unsure on the consistent bills bit, that's why I was asking really - I find that there is a lot of conflicting information online about any form of heat pump, so it's hard to know what is factual. Regarding passive cooling - I'm referring to circulating the liquid underground to cool it to the ambient 15 ish degrees with no energy used other than to pump the liquid, then supply at 17-20 degrees inside the house, essentially for free. I (perhaps mistakenly) thought that air source wasn't capable of this because the ambient temperature is warmer, so cooling would be active - using energy.

 

It's good to know your experience is good with the noise level - it's not a huge concern - I think the likely installation point for an ASHP in our side alley would be far enough away from any windows and doors to be noticed.

 

Quote

I had a spare free 137m borehole and still fitted an ASHP. 

May I ask why you made this decision even with a borehole already available?

[Strak]

4 minutes ago, JohnMo said:

you still get a CoP of about 2.7, for the day you are down to that level. At -2 you are mid 3 and at 7 degrees, 4.5 for CoP.

 

Thanks - useful to see those figures, looks pretty good really.

 

If your ASHP is behind the shed, how far away is that from the house? I could potentially locate it a bit further down the garden I suppose, although may have problems doing that and keeping away from the boundary.

[Kelvin]

I didn’t want the compressor in the house nor did I really have the space. Trying to find a reliable company to install the equipment was harder than I expected which put me off. ASHPs are increasingly more common so, in theory, should be easier to maintain. The spare  borehole is close to our primary water borehole and I didn’t want any risk to that. I’ve had ASHPs in previous houses so familiar with them. Overall I couldn’t see any significant benefit in using it. 

[JohnMo]

2 minutes ago, Strak said:

ASHP is behind the shed, how far away is that from the house?

Pipe length from ASHP is about 8 to 10m to UFH manifold, each way.

 

Cooling from ASHP 

Flow at 15 degrees on a 20 degree day the EER (CoP for cooling) is about 8. Dropping to 6.5 on a 25 degree day.

[BadgerBadger]

I had some indicative quotes for 3 x 100m boreholes for GSHP a couple of years ago, they came in at approx £20k.  The economics just didn't work vs ASHP.

[Mr Punter]

On Google I get 22m hits for ASHP and 500k for GSHP.  It looks like ASHP is the way forward.  You may find GSHP difficult / impossible to maintain in the future.

Edited April 25 by Mr Punter

[saveasteading]

If it helps your decision, a develoment local to me had GSHP 80m deep, and 8 houses have abandoned them and installed ASHP.

The cost of running the gshp was much more than direct electric heating would have been.

gshp does not work in heavy clay. If you are in Iceland and above hot rocks then that is different.

 

ashp can multiply the input energy by up to 6.

gshp will be x 1.5 if you are lucky and -0.5 if as above.

 

If you are researching from scratch and looking at options then great. We here can all help with both practice and science. If you are getting advice to use gshp then you are getting very bad advice, unless in Iceland etc.

If this is from a current advisor or contractor, then its time to lose them and perhaps discard all their information and advice to date.

[JohnMo]

8 minutes ago, Mr Punter said:

On Google I get 22m hits for ASHP and 500k for GSHP.  It looks like ASHP is the way forward.  You may find GSHP difficult / impossible to maintain in the future.

There is some nonsense on this site. How many hits you get on Google is no way to make a financial decision.

 

There is the best part of zero maintenance to do on a GSHP, except maintain the anti freeze levels, the only maintenance to do on an ASHP is to clean debris out the condenser. Once either get leaks or refrigerant side failures they are good for the scrap heap - as no one will maintain either.

[Mr Punter]

14 minutes ago, JohnMo said:

How many hits you get on Google is no way to make a financial decision.

 

Hits on Google is one of the main drivers for investment and development of the internet.  Every company uses it as a metric.  In this case it is indicative of the relative popularity of the 2 systems.  GSHP looks more likely to become obsolete.

 

[saveasteading]

32 minutes ago, JohnMo said:

the best part of zero maintenance to do on a GSHP,

On the project I mentioned above they were forever working on the heat exchangers. That may have been intended as  a distraction from the real  problem though: that it wasn't working because all the available heat had already been taken from the ground.

[JohnMo]

13 minutes ago, Mr Punter said:

Hits on Google is one of the main drivers for investment and development of the internet.  Every company uses it as a metric.  In this case it is indicative of the relative popularity of the 2 systems.  GSHP looks more likely to become obsolete.

 

Just put solar thermal into to Google and got a 193 million hits and "solar thermal" with 10.7 million hits, doesn't mean I will heat my house with it. In fact just taken my thermal off because it was not as good as expected. And solar thermal is just about obsolete.

[JohnMo]

18 minutes ago, saveasteading said:

On the project I mentioned above they were forever working on the heat exchangers. That may have been intended as  a distraction from the real  problem though: that it wasn't working because all the available heat had already been taken from the ground.

If they are open loop, they may just be pulling up debris and clogging the exchangers.  Or on closed loops and if put in by monkeys never flushed correctly.

[saveasteading]

58 minutes ago, JohnMo said:

if put in by monkeys

That, and specified by parasites. they wanted the subsidies and were into greenwash.

[Kelvin]

2 hours ago, JohnMo said:

There is some nonsense on this site. How many hits you get on Google is no way to make a financial decision.

 

There is the best part of zero maintenance to do on a GSHP, except maintain the anti freeze levels, the only maintenance to do on an ASHP is to clean debris out the condenser. Once either get leaks or refrigerant side failures they are good for the scrap heap - as no one will maintain either.

Nonsense or not my difficulty finding an installer put me off if there were any problems with it in the future. My wife wouldn’t have a clue where to start with any of this and she’s likely to outlive me. 😂 

[SteamyTea]

If you want to see how badly a GSHP can go wrong, both technically and financially, take a trip to my local swimming pool.

Jubilee Pool