Geothermal vs Air to Water

3ryan

Hi I am trying to figure out whether it is better to go with geothermal or air to water heating system. I understand that the geothermal is more expensive to install but may be less expensive to run than air to water. I am just a bit concerned that air to water will leave me with huge electricity costs

Old Jim

The cost to run will depend on your insulation levels, air-tightness, thermal bridges etc.
I went with air-to-water and it has cost me ~350eur to run for the first year incl VAT for all heating and hot water. But if my house was badly insulated or had vent holes in the walls or cold bridges around windows and floors then it would cost a lot more to run.
In my case, I don't believe I would have substantially lower running costs with a geothermal HP.

Water John

Old Jim, you are very accurate. Good modern builds, with insulation and sealed envelope don't require a lot of heat and the cost figure you give, I agree with.
A cost benefit analysis on €350 would make no sense of further capital investment.
Just make sure to get a good Air to Water Heat Pump. One that can work at low air temp and also provide hot water.
If you have a sealed house a good investment, not just in terms of efficiency but also health would be to have an air exchange unit. Cost installed, about €5K.
You can use UFH or Alu Rads with the Heat Pump.

BarneyMc

Old Jim wrote: »

The cost to run will depend on your insulation levels, air-tightness, thermal bridges etc.
I went with air-to-water and it has cost me ~350eur to run for the first year incl VAT for all heating and hot water. But if my house was badly insulated or had vent holes in the walls or cold bridges around windows and floors then it would cost a lot more to run.
In my case, I don't believe I would have substantially lower running costs with a geothermal HP.

Not in my house yet but I went the same route. I put the cash I saved with going the air to water into insulation, air tightness, etc. - this will work forever at €0 running costs.

jayoerris

Also interested in this post. What would the difference in price between the two on a typical house? Whats most peoples bills on electricity per month?

Water John

I think the capital difference could be 5 or 6K. Ground to Water is a significant works. Air to Water is simply plug in.

As I say, I don't have it, sadly.
But if you look at the coefficiencies of Air to Water is above 3
Ground to Water above 4.

Say 25% difference, but if your annual running costs are €400. What is a 25% saving on that, €100.

Others may have more accurate data.

One also has to be careful with the type of ground one has.

BarneyMc

Yeah that's my thinking. With ground to water you've it all to make up and with a really well insulated and airtight house you may never do that over the life of the pump.

Water John

It is a rare situation but if one had a lake of significant stream nearby one could get a coefficient up around 6.

Tommyboy08

Water John wrote: »

It is a rare situation but if one had a lake of significant stream nearby one could get a coefficient up around 6.

It's it rare at all, and not nescessary to need a water source to achieve high cop,
A good heat pump with a well designed heat distribution system will achieve cops of 7 and above, there are companies in Ireland doing this on a daily basis and not just one offs, but consistently with their systems,

The main thing people are forgetting to mention on this post is that the bigger factor in why to go for the groundsourse heat pumps instead of the air source is the life expectancy, the annual running costs are not the biggest thing even though they are much lower with a good ground source system it's that no air source unit will last 25 years, most of the jap units will struggle to manage half that and this is why with average replacement costs of €7000 that the ground source will work out much cheaper over their life
Also I have found that the price differences are closer to €2000 between ground and air systems
But cheap jap and Chinese units are €5000 cheaper, but you defiantly get what you pay for with them.

mjp

With regards to airtightness do most people do the work themselves or do you get specialist people in who agree to seal to specific requirements as outlined in BER. Issue I have is that lot of guys who I will be getting for my selfbuild would be "old school" and have built house prior to 2010 when there wasn't as much emphasis on airtightness and insulation.

BarneyMc

mjp wrote: »

With regards to airtightness do most people do the work themselves or do you get specialist people in who agree to seal to specific requirements as outlined in BER. Issue I have is that lot of guys who I will be getting for my selfbuild would be "old school" and have built house prior to 2010 when there wasn't as much emphasis on airtightness and insulation.

I didn't have the time to sort out, learn how to apply and then apply so I got a specialist. Really glad I did as the job is top notch. I suppose your builder will have to get you through the regs or an agreed higher standard so that's your 'guarantee'. You can also ask for references and results they've got from previous jobs.

murphaph

Tommyboy08 wrote: »

It's it rare at all, and not nescessary to need a water source to achieve high cop,
A good heat pump with a well designed heat distribution system will achieve cops of 7 and above, there are companies in Ireland doing this on a daily basis and not just one offs, but consistently with their systems,

The main thing people are forgetting to mention on this post is that the bigger factor in why to go for the groundsourse heat pumps instead of the air source is the life expectancy, the annual running costs are not the biggest thing even though they are much lower with a good ground source system it's that no air source unit will last 25 years, most of the jap units will struggle to manage half that and this is why with average replacement costs of €7000 that the ground source will work out much cheaper over their life
Also I have found that the price differences are closer to €2000 between ground and air systems
But cheap jap and Chinese units are €5000 cheaper, but you defiantly get what you pay for with them.

I agree that an air source unit will fail several years before a ground source one, BUT there's a silver lining here...the technology improves year on year (eg modulation), so while you're still using your 25 year old ground source unit with its 25 year old tech, the other guy has a much more modern unit profiting from newer tech and probably cheaper manufacturing costs.

There is of course the argument that says any heat pump is a waste of money in a modern, really well insulated and highly airtight property. At a certain point you push the energy consumption of the property so low that spending "big money" on a heat pump of any kind can seem a waste compared to high efficiency condensing gas boiler.

delfagio

murphaph wrote:

There is of course the argument that says any heat pump is a waste of money in a modern, really well insulated and highly airtight property. At a certain point you push the energy consumption of the property so low that spending "big money" on a heat pump of any kind can seem a waste compared to high efficiency condensing gas boiler.

I would definitely agree with you on this Murphaph, but that's just my own opinion, I am sure others would disagree.

Condenser

murphaph wrote: »

I agree that an air source unit will fail several years before a ground source one, BUT there's a silver lining here...the technology improves year on year (eg modulation), so while you're still using your 25 year old ground source unit with its 25 year old tech, the other guy has a much more modern unit profiting from newer tech and probably cheaper manufacturing costs.

There is of course the argument that says any heat pump is a waste of money in a modern, really well insulated and highly airtight property. At a certain point you push the energy consumption of the property so low that spending "big money" on a heat pump of any kind can seem a waste compared to high efficiency condensing gas boiler.

I'd love to know where people get this impression that the technology is improving year on year besides buying into sales waffle. I started my apprenticeship in 1997 and was working on air conditioning units which is essentially what most "air to water" units are. Inverter units were introduced about 1999-2000 and to be honest they haven't changed much since. The efficiency gains have been miniscule and I have yet to see a system older than 12yrs that isn't on life support. A GSHP for a few K's more can last up to 30yrs.
Comparing ground source units to air source units and thinking you're getting a similar product in terms of efficiency and lifespan is completely wrong. Lifetime costs of a GSHP will be less than 1/3 that of an ASHP.

murphaph

Condenser wrote: »

I'd love to know where people get this impression that the technology is improving year on year besides buying into sales waffle. I started my apprenticeship in 1997 and was working on air conditioning units which is essentially what most "air to water" units are. Inverter units were introduced about 1999-2000 and to be honest they haven't changed much since. The efficiency gains have been miniscule and I have yet to see a system older than 12yrs that isn't on life support. A GSHP for a few K's more can last up to 30yrs.
Comparing ground source units to air source units and thinking you're getting a similar product in terms of efficiency and lifespan is completely wrong. Lifetime costs of a GSHP will be less than 1/3 that of an ASHP.

Seeing as in Ireland hardly anyone actually methodically calculates the heat demand that the heat source needs to satisfy it's probably no wonder that people end up with hugely over sized heat pumps that cycle like mad and die an early death.

I fully accept that GSHPs last longer, but there are countless examples of 25 year old ASHPs running without issue over here. The most important step is selecting the appropriate unit for the task at hand.

Water John

Any one supplying or indeed installing UFH should calculate the demand.
Certainly the engineer of the plans should do so.
Suppliers of Air to Water Units like Glen dimplex will do it for you.
As you say, absolutely no point in oversizing.

Condenser

murphaph wrote: »

Seeing as in Ireland hardly anyone actually methodically calculates the heat demand that the heat source needs to satisfy it's probably no wonder that people end up with hugely over sized heat pumps that cycle like mad and die an early death.

I fully accept that GSHPs last longer, but there are countless examples of 25 year old ASHPs running without issue over here. The most important step is selecting the appropriate unit for the task at hand.

Ah yes the old shur they haven't a clue in Ireland fall back. Even the most naïve of homeowners should have some idea of their heat loss either through their Architect or their BER. If people start spec'ing equipment much bigger then its their own fault if they don't point that out or rule out the supplier entirely based on that alone.
I can tell you with absolute certainty that none of the ASHP's you see running for that long in Germany are any of the brands that are popular at the moment and units of high quality such as that cost more than as GSHP in the first place.

Condenser

Water John wrote: »

Any one supplying or indeed installing UFH should calculate the demand.
Certainly the engineer of the plans should do so.
Suppliers of Air to Water Units like Glen dimplex will do it for you.
As you say, absolutely no point in oversizing.

An air to water has to be oversized due to its very nature. The output drops along with the outside temp but your heating demand increases and so an ASHP therefore must be oversized.

Ronin247

Another issue with ground source heat pumps is that the area over the collector cannot be drained, as it relies on rainwater bringing heat through the soil. I have a wet lawn and cannot put drainage in because it would affect the performance of the GSHP....or so I was told .

Condenser

Ronin247 wrote: »

Another issue with ground source heat pumps is that the area over the collector cannot be drained, as it relies on rainwater bringing heat through the soil. I have a wet lawn and cannot put drainage in because it would affect the performance of the GSHP....or so I was told .

Not true. With a GSHP the collector should be installed in free draining soil where water is consistently moving. Putting a collector where water is slow moving or stagnant can lead to freezing and a drop in performance. With a collector you don't want stagnant/slow water drainage and you don't want bone dry. Everything between is absolutely fine which is about 80% of situations.

randombar

Hi All,

Apologies to piggy back on the thread but you seem to be the right people to ask.

Have a 5 year old 2500sqft story and a half house with rads, solar panels for HW and grant condensing kerosene boiler. House is well insulated, not sure of the air tightness but I think it would be decent enough. Oil cost last year was probably 500.

Doing a review of my energy costs at the minute thanks to another inspirational thread on here.

Just wondering what kind of price would I be talking for a a2w heat pump and would it be worth it?

Thanks,
Gary

KCross

GaryCocs wrote: »

Hi All,

Apologies to piggy back on the thread but you seem to be the right people to ask.

Have a 5 year old 2500sqft story and a half house with rads, solar panels for HW and grant condensing kerosene boiler. House is well insulated, not sure of the air tightness but I think it would be decent enough. Oil cost last year was probably 500.

Doing a review of my energy costs at the minute thanks to another inspirational thread on here.

Just wondering what kind of price would I be talking for a a2w heat pump and would it be worth it?

Thanks,
Gary

At 500 you would be wasting your money I'd say with a heat pump. The payback would be several decades I'd say!
Also, Heat Pumps work better with underfloor heating, rads not so much, so I'd leave it as is.

randombar

Really regretting not putting in the concrete 1st floor floors and UFH initially now.

Woulda Coulda Shoulda