Air (and Ground) Source Heat Pumps

[9873210]

Yes only an ASHP (as opposed to a GSHP) can provide cooling, but not all will. To provide cooling, an ASHP needs to be of the 'air-to-air' type. An ASHP of the 'air-to-water' type will not (AFAIK) have any cooling capability.

There is a great deal of confusion in the mind of the Great British Public, many of whom are under the impression an ASHP is the same thing as an air-to-air heat pump. We see it constantly in these threads about heat pumps.

I thought I posted this before, but it seems to have vanished.

You are not helping the confusion.

A heat pump has two sides, outside and inside. The outside can be air source or ground source. This determines if it is an air source or ground source. Either source can be used for A/C or heat.

It's the inside that determines if it can be used for A/C. The inside can be directly to an air handler; or it can be to water (with hot water run through radiators or underfloor coils); or you can run the freon through underfloor coils and radiators. If you use an air handler you can have a single central air handler with duct work or multiple room sized air handlers (e.g. mini-splits).

Systems with different heat exchangers in different zones are not unknown.

In theory any interior arrangement can be used for cooling. However there will be condensation if you cool the air below the dew point. In reality this will happen in most climates and particularly in the UK's maritime climate. No one wants wet floors or radiators.

In practice this means no cooling with traditional radiators or underfloor coils, only with a direct air handler is designed to collect and drain the condensate. But a ground-to-air heat pump is just a competent as an air-to-air heat pump as an A/C unit. In hot climates ground-to-air heat pumps are used specifically as A/C units with heat as a secondary function.

[Howard]

So I'm still a happy ASHP user, for localised heating on demand. When our gas central heating boiler needs replacing I will certainly consider a larger heat pump system as a replacement.

regards

Howard

Afternoon Howard,

You are one of the few heat pump users who gives practical input.

From your experience to date, would you re-use your wet central heating pipework and radiators or would you decommission the system and install a purely warm air system to all rooms. Do you think there would be any rooms, like bathroom which would need electric towel rails to prevent condensation/mould.

Do you think that your future heat pump electricity bills would be higher than your current gas bills ?

Your experience and input is vital to those of us who may have to make such decisions in the near future.


Not looking for nth degree of accuracy.

Thanks in advance.

As you are aware, it’s difficult to forecast the energy (and our own) situation but our previous experience with warm air heating in the seventies was a good one.

Forgive the nostalgia - our first house in the North East was built by Greensitt and Barratt. If you watched the Likely Lads, it was virtually identical to Bob and Thelma’s house - but posher because it was “link detached” not a semi ... It had gas-fired warm air heating and whilst not insulated to modern standards was warm and comfortable and didn’t cost much to heat. Hot water was generated by an immersion heater. We used to travel to parents for Christmas and New Year and left the house unheated during fierce Northumberland winters. When we came back, we put the heating on and within half an hour the house felt warm throughout. Mrs H reminded me that with only single glazing and a young family we did have to wipe the condensation from windows in the winter.

Now, living in the effete South we have a larger house built 25 years ago. It is pointless heating all of our rooms with just two of us occupying the house. It’s well insulated so we have most of our TRVs turned down and a high capacity system boiler running only half of our eighteen radiators most of the time. Our family came for tea today, so I turned on the two radiators in our sitting room. It’s quite large and on the North side of the house and from 8 degrees this morning would require the radiators on all day plus the high output gas fire to get it up to 20 degrees. In fact I put two 2kW convectors in on full power and they raised the air temperature in just over quarter of an hour for less than 50p according to the smart meter.

As you suggest, when the gas boiler needs to be changed we have a decision to make. Whilst it’s a modern condensing boiler it is no cheaper to run than the original Potterton. To increase the size of most of our radiators would, I guess, cost many thousand pounds so I would be very tempted to switch to a warm air ASHP system with an immersion for the hot water. The problem might be how to channel hot air to all the key downstairs rooms using a visually acceptable solution. Fan units on the walls wouldn’t be appropriate. Upstairs this would be simple using the loft for ducting. Bathrooms would be included. Perhaps electric towel rails would be suitable as in most hotels. With good double glazing condensation hasn't been a problem.

So, to answer your question, our experience of warm air heating many years ago and our current ASHP will make me look seriously at a heat pump if we are forced to upgrade the heating. Given our lifestyle, I doubt if it would cost more to run than a gas system.

Hope this is helpful.

regards

Howard

[scotview]

So, to answer your question, our experience of warm air heating many years ago and our current ASHP will make me look seriously at a heat pump if we are forced to upgrade the heating. Given our lifestyle, I doubt if it would cost more to run than a gas system.

Howard

Morning Howard, thanks for taking the time to post that interesting reply.

It will be good to get feedback from actual users as the installation of heat pumps, of whatever variety, becomes more topical.

Thank you.

[Mike4]

Yes only an ASHP (as opposed to a GSHP) can provide cooling, but not all will. To provide cooling, an ASHP needs to be of the 'air-to-air' type. An ASHP of the 'air-to-water' type will not (AFAIK) have any cooling capability.

There is a great deal of confusion in the mind of the Great British Public, many of whom are under the impression an ASHP is the same thing as an air-to-air heat pump. We see it constantly in these threads about heat pumps.

I thought I posted this before, but it seems to have vanished.

You are not helping the confusion.

A heat pump has two sides, outside and inside. The outside can be air source or ground source. This determines if it is an air source or ground source. Either source can be used for A/C or heat.

It's the inside that determines if it can be used for A/C. The inside can be directly to an air handler; or it can be to water (with hot water run through radiators or underfloor coils); or you can run the freon through underfloor coils and radiators. If you use an air handler you can have a single central air handler with duct work or multiple room sized air handlers (e.g. mini-splits).

Systems with different heat exchangers in different zones are not unknown.

In theory any interior arrangement can be used for cooling. However there will be condensation if you cool the air below the dew point. In reality this will happen in most climates and particularly in the UK's maritime climate. No one wants wet floors or radiators.

In practice this means no cooling with traditional radiators or underfloor coils, only with a direct air handler is designed to collect and drain the condensate. But a ground-to-air heat pump is just a competent as an air-to-air heat pump as an A/C unit. In hot climates ground-to-air heat pumps are used specifically as A/C units with heat as a secondary function.

And equally, your post above is adding to the confusion too in my opinion, by explaining details irrelevant to most domestic householders.

Whilst what you write is broadly correct, nothing contradicts what I wrote but remember we are talking heat pumps for the millions of modest two, three and four bedroom houses comprising the vast majority of our housing stock. Yes multiple zones of varying types might be installed inside mansions like the picture posted by A.i.Y, but I hold the vast majority will one type of the other. Either air-to-air, or air-to-water. Yes there are such things as ground-to-water, ground to air, water-to-water and water-to air, I don't have stats but I bet at least 95% of household heat pump sales are air source and inside, the majority will be 'to water' heating radiators and the hot tank. Air-to-water.

So I still hold the choice for most ordinary householders is between "air-to-air" which provides effective cooling too but no hot water, and "Air-to-water", which provided no cooling but heats the hot tank too. Simple.

[JohnB]

If installing a HP, I'd look at long term trends in electricity and gas prices. Electricity prices will get less coupled to gas prices as other generation sources come on stream, and I predict the low end electricity prices (when renewables are doing well, not necessarily nighttime) prices will get much closer to gas prices. So if you have a well insulated house with lots of thermal mass (the underfloor heating concrete slabs are ideal, but books will do!), you will be able to heat a house with time-shifting more cheaply than with gas. Abandoning gas will also save its standing charge.

Forced air systems a lot more popular in places like Colorado where temperature ranges of -20 to +35 require heating and A/C, but I found them noisy and they move dust around. With climate change I think we will need A/C part of the year, but I hope the number of days means that fewer rooms need to be covered

[88V8]

Forced air systems a lot more popular in places like Colorado where temperature ranges of -20 to +35 require heating and A/C, but I found them noisy and they move dust around.

I doubt that air/air would be practicable in most existing houses. Ducting needs to be built-in ab initio.
Most will go for air/water because that may work with legacy wet systems.

V8

[Mike4]

If installing a HP, I'd look at long term trends in electricity and gas prices. Electricity prices will get less coupled to gas prices as other generation sources come on stream, and I predict the low end electricity prices (when renewables are doing well, not necessarily nighttime) prices will get much closer to gas prices. So if you have a well insulated house with lots of thermal mass (the underfloor heating concrete slabs are ideal, but books will do!), you will be able to heat a house with time-shifting more cheaply than with gas. Abandoning gas will also save its standing charge.

Forced air systems a lot more popular in places like Colorado where temperature ranges of -20 to +35 require heating and A/C, but I found them noisy and they move dust around. With climate change I think we will need A/C part of the year, but I hope the number of days means that fewer rooms need to be covered

Point of Order...

Heating the house is only 50% of the story. The other factor to consider is hot water. Hot water is just as important and heating it with electricity if an air-to-air HP is installed, undermines the financial viability of the HP in the first place.

[9873210]

Yes only an ASHP (as opposed to a GSHP) can provide cooling,

You made a simple declarative statement that was wrong. Refuting such garbage necessarily requires details.

Point of Order...

Heating the house is only 50% of the story. The other factor to consider is hot water. Hot water is just as important and heating it with electricity if an air-to-air HP is installed, undermines the financial viability of the HP in the first place.

More misinformation.

There are stand-alone air-to-domestic hot water heat pump systems. (In the UK these would be happiest in a well ventilated shed.) There are combined units that do both air to air and air to domestic hot water, some of these also run underfloor heating in different zones. Some of these even use the hot water as a heat sink when A/C and water heating are needed at the same time.

There are mini-splits that solve the problem of no ducting for retro-fits. In the simplest sense these work by pumping hot freon around the building instead of hot water.

It is true that if or when heat pumps become common there will probably be a couple of common commodity architectures, and that most users will pick one of them or pay through the nose for a custom system. It is also probably true that these will be sub-optimum in most case. But before the collective decision is made we should look at what is possible, and certainly what is installed in thousands or millions of houses around the world. Not just pick the first thing somebody heard of and then complain it doesn't work.

The ignorance and arrogance of people trained to install boilers is probably the single biggest problem. Time to replace them all with newly trained imports from the developing world, who at least won't have too many pre-existing prejudices.

[Howard]

If installing a HP, I'd look at long term trends in electricity and gas prices. Electricity prices will get less coupled to gas prices as other generation sources come on stream, and I predict the low end electricity prices (when renewables are doing well, not necessarily nighttime) prices will get much closer to gas prices. So if you have a well insulated house with lots of thermal mass (the underfloor heating concrete slabs are ideal, but books will do!), you will be able to heat a house with time-shifting more cheaply than with gas. Abandoning gas will also save its standing charge.

Forced air systems a lot more popular in places like Colorado where temperature ranges of -20 to +35 require heating and A/C, but I found them noisy and they move dust around. With climate change I think we will need A/C part of the year, but I hope the number of days means that fewer rooms need to be covered

Point of Order...

Heating the house is only 50% of the story. The other factor to consider is hot water. Hot water is just as important and heating it with electricity if an air-to-air HP is installed, undermines the financial viability of the HP in the first place.

With a tariff like Octopus Go, I guess a lot of the water heating could be done between 12.30 am and 4.30 am? Running a 3kW immersion heater for an hour or two in that period would only cost around 20p - 40p at current off peak rate of 7p per kWh? And possibly less if it doesn't run continuously. Our heat store is well insulated and keeps the water very hot for many hours.

We also have an inline electric water heater which costs only fractions of a pence to run for hand washing etc. And holiday cottages we've used have very good electric showers. I'm guessing that electric water heating solutions will get more efficient in the future?

regards

Howard

[Mike4]

Yes only an ASHP (as opposed to a GSHP) can provide cooling,

You made a simple declarative statement that was wrong. Refuting such garbage necessarily requires details.

I agree, that is piffle. I've no idea why I wrote that, when I should have written "Yes only a <whatever>-to air heat pump will provide cooling, as opposed to a <whatever>to water heat pump" which won't. Too much good wine, probably!

Point of Order...

Heating the house is only 50% of the story. The other factor to consider is hot water. Hot water is just as important and heating it with electricity if an air-to-air HP is installed, undermines the financial viability of the HP in the first place.

More misinformation.

There are stand-alone air-to-domestic hot water heat pump systems. (In the UK these would be happiest in a well ventilated shed.) There are combined units that do both air to air and air to domestic hot water, some of these also run underfloor heating in different zones. Some of these even use the hot water as a heat sink when A/C and water heating are needed at the same time.

There are mini-splits that solve the problem of no ducting for retro-fits. In the simplest sense these work by pumping hot freon around the building instead of hot water.

It is true that if or when heat pumps become common there will probably be a couple of common commodity architectures, and that most users will pick one of them or pay through the nose for a custom system. It is also probably true that these will be sub-optimum in most case. But before the collective decision is made we should look at what is possible, and certainly what is installed in thousands or millions of houses around the world. Not just pick the first thing somebody heard of and then complain it doesn't work.

More of your over-complicating tosh similar to before. This sort of stuff is not yer average mass market heat pump for yer average three bed semi. Yes all this fancy bleeding edge stuff might exist for punters with £3m houses but it is not mainstream mass market domestic product. It might be in 20 years but it certainly isn't now. I think we are talking about different markets. Mr and Mrs Normal in Egham are never gonna be fitting combined units that do both air to air and air to domestic hot water, some of these also run underfloor heating in different zones in their two bedroom bungalow. These are the houses and the potential purchasers of heat pumps I write for.

The ignorance and arrogance of people trained to install boilers is probably the single biggest problem. Time to replace them all with newly trained imports from the developing world, who at least won't have too many pre-existing prejudices.

I agree. Most of them are thick as mince.

(Edit to remove another error!)

[woolly]

Both GSHPs and ASHPs can be and are used for cooling, even in smaller domestic situations. Obviously smaller or cheaper properties will be less likely to have a GSHP, but for those smaller places that have a borehole or share a ground array GSHP cooling is more efficient than ASHP, as with heating.
GSHPs have the added benefit of two modes of cooling: active (running the heat pump in reverse cycle so that the ground array acts as a heat emitter while the underfloor pipes circulate cooled water underfoot) and passive, where the heat pump is switched off but the cold water/glycol mixture in the ground loops is circulated through a fan unit to provide cool air into a property.
The advantage of the passive mode is that there is no heat cycle involved - it costs very little just to run the circulation pumps and fan (Kensa estimates £20/year, after you stump up for the additional fan heat exchanger box of course!).
Active, reverse-cycle cooling is reserved for buildings that need greater cooling in hot summers, e.g. glass-walled office blocks, data centres and so on.
Both cooling modes have the added benefit that the heat extracted from the building gradually recharges the ground array for the winter, making the whole cycle even more efficient.

Kensa, for example, has this to say on the subject: https://www.kensaheatpumps.com/active-cooling-vs-passive-cooling/

Taking the concept even further, inter-seasonal heat storage projects can use heat pumps and ground arrays to store more summer heat for winter use for example by extracting heat from tarmac surfaces as well as buildings and storing it in the ground (https://icax.co.uk/thermal_energy_storage.html) - obviously the province of neighbourhood heating/cooling systems rather than individual properties.

But am I the only one who finds it weird that people in our little temperate island put up such resistance to a safe, clean and established technology (used for decades in other countries where it gets far colder and far hotter than here), yet as another gas-powered property blows up (https://www.bbc.co.uk/search?q=gas+explosion&d=news_ps) we collectively shrug and work hard to convince ourselves we have no other choice?

[csearle]

Moderator Message:
Team. Please remember we are all treating each other with respect here. If you disagree with something said please try to express it in a mild-mannered way rather than in a provocative way. Thanks - Chris

[funduffer]

Not sure if it is true, but I have heard that GSHP's can have an effect on your garden. If the pipework is laid out horizontally in an array under the garden / lawn, then you will extract heat from the soil, and this can have an adverse effect on what is growing in the garden. Cold soil kills plants!

Alternatively a GSHP can use vertical boreholes that go down 100's of feet to extract heat from the ground (obviously an expensive business to drill down this far!). I would imagine though the vertical boreholes provide a more reliable source of heat throughout the year, but I may be wrong.

FD

[woolly]

Not sure if it is true, but I have heard that GSHP's can have an effect on your garden. If the pipework is laid out horizontally in an array under the garden / lawn, then you will extract heat from the soil, and this can have an adverse effect on what is growing in the garden. Cold soil kills plants!

Alternatively a GSHP can use vertical boreholes that go down 100's of feet to extract heat from the ground (obviously an expensive business to drill down this far!). I would imagine though the vertical boreholes provide a more reliable source of heat throughout the year, but I may be wrong.

FD

The underground collector array is usually sited under lawns or open fields and is usually between 80cm and 2m down - well below the roots of grass and other such plants. Even large trees have the majority of their roots within the first 40cm of ground. Commonly occurring events like winter affect plants far more - GSHPs rely on the fact that the deeper you go ground temperatures remain remarkably stable year-round. The only point where cold pipes may have an effect on plants is where the header pipes get closer to the ground to go into the house - on some systems they may actually break the surface to go in through a wall - but in such cases the pipes are lagged to prevent ground freeze.
As the system extracts heat during the winter the ground around the collector array will chill and may even freeze (although system designers try to avoid this), but during summer the ground is "recharged" through solar gain. Water in the ground ensures efficient heat transfer and transfers solar gain deeper underground.

Yes, vertical drilling is messy and expensive, but enables GSHPs on sites where it would otherwise be impossible such as houses with average-sized gardens (provided the drilling truck can get in!). Such systems only go down 100m or so and still rely on the fact that the ground temperature stays at a very stable 5-10ºC year-round, but need suitable subsurface hydrology to ensure cold spots don't develop. It's different with geothermal power that taps into the increasing heat gradient much deeper underground, where pipes will go 1000m or more down. Often these are open-loop systems with warm water being pumped out of the the ground, heat extracted into the building, and the resulting cooled wastewater being pumped back down away from the extraction point, but these are not domestic-scale.

Actually I just thought I'd check on the facts in this post and I find that the British Geological Survey have kindly summarised the various ways of extracting heat from the ground here, if anyone's interested: https://www.bgs.ac.uk/geology-projects/geothermal-energy/

[88V8]

But am I the only one who finds it weird that people in our little temperate island put up such resistance to a safe, clean and established technology (used for decades in other countries where it gets far colder and far hotter than here)...

I think we have a very long way to go before there is a decent understanding of the potential, and one can invite an installer without potentially being sold bollox.
After all it can be hard to get tradesmen to do even the most elementary job without it being cocked up.

A lot of resistance - speaking for myself - has to do with the fact that heat pumps (undefined) are being touted as a boiler substitute and yet many if not most homes are inadequately insulated and have wet systems where heat pumps would not be a direct swap-in.
Ignorant guff spouted by politicians doesn't help.

If I were in the market, I would want to do what I usually do with any building trade activity, to learn how to do it myself before seeking quotes, so that I can evaluate what is suggested. Most customers don't bother, which is why the building trade is so rife with botchers, and I fear that heat pumps will be no different.

V8

[woolly]

A lot of resistance - speaking for myself - has to do with the fact that heat pumps (undefined) are being touted as a boiler substitute and yet many if not most homes are inadequately insulated and have wet systems where heat pumps would not be a direct swap-in.
Ignorant guff spouted by politicians doesn't help.

If I were in the market, I would want to do what I usually do with any building trade activity, to learn how to do it myself before seeking quotes, so that I can evaluate what is suggested. Most customers don't bother, which is why the building trade is so rife with botchers, and I fear that heat pumps will be no different.

V8

Fully agree - the situation is worse than with solar panels or insulation as heat pumps require ongoing maintenance, and too often cowboys offer poorly-designed systems that fail to deliver as promised by which time they have absconded or gone bust. My brother-in-law's firm has been installing heat pumps for over a decade (sometimes with my help!) and a scenario he sees time and again is punters who rejected his quote for being too expensive frantically phoning a year or so later asking his firm to fix the botch they opted for... as you say though, the buy cheap and regret at leisure mentality seems to be common with pretty much anything to do with building.
In fact he got so fed up with cheapskates trying to drive down his upfront prices that he tends now to concentrate on projects where buyers understand what's important is total cost of ownership rather than lowest installation cost.

As for plug-in replacements for wet systems, I seem to recall him saying there are more and more viable options - e.g. plug-and-play ASHPs that will output much hotter water for radiators - available now as manufacturers scramble to satisfy what is clearly a massive market. But the buzzword is still fabric first - any reputable installer will insist the insulation/windows are up to scratch before contemplating a heat pump and will take time to educate the customer about the different heating style required with heat pumps, as they know pretty accurately how the performance will be degraded otherwise.

While I applaud your approach to learning the trade, I would caution that while laying and pressure-testing underfloor systems is something anyone can do, designing and building a custom plant room for a heat pump installation requires specialist training beyond what most plumbers learn, which is why there is a huge shortage of installers and it's so hard to get anyone decent to do the work!
If you're interested in volunteering for educational purposes and are semi-competent an extra pair of hands is always useful - bro-in-law might be able to accommodate you...

[anon155742]

Fully agree - the situation is worse than with solar panels or insulation as heat pumps require ongoing maintenance, and too often cowboys offer poorly-designed systems that fail to deliver as promised by which time they have absconded or gone bust. My brother-in-law's firm has been installing heat pumps for over a decade (sometimes with my help!) and a scenario he sees time and again is punters who rejected his quote for being too expensive frantically phoning a year or so later asking his firm to fix the botch they opted for... as you say though, the buy cheap and regret at leisure mentality seems to be common with pretty much anything to do with building.
In fact he got so fed up with cheapskates trying to drive down his upfront prices that he tends now to concentrate on projects where buyers understand what's important is total cost of ownership rather than lowest installation cost.

As for plug-in replacements for wet systems, I seem to recall him saying there are more and more viable options - e.g. plug-and-play ASHPs that will output much hotter water for radiators - available now as manufacturers scramble to satisfy what is clearly a massive market. But the buzzword is still fabric first - any reputable installer will insist the insulation/windows are up to scratch before contemplating a heat pump and will take time to educate the customer about the different heating style required with heat pumps, as they know pretty accurately how the performance will be degraded otherwise.

While I applaud your approach to learning the trade, I would caution that while laying and pressure-testing underfloor systems is something anyone can do, designing and building a custom plant room for a heat pump installation requires specialist training beyond what most plumbers learn, which is why there is a huge shortage of installers and it's so hard to get anyone decent to do the work!
If you're interested in volunteering for educational purposes and are semi-competent an extra pair of hands is always useful - bro-in-law might be able to accommodate you...

What is the cost for an air source heat pump system to replace a wet system for the average 3 bed semi?

[woolly]

Fairly current information on heat pump installation costs can be found here: https://www.which.co.uk/reviews/ground-and-air-source-heat-pumps/article/ground-and-air-source-heat-pumps/air-source-heat-pump-costs-and-savings-akySY6N5Y6Dd

ASHP installations are about £7000-£10000, but there is a Boiler Upgrade Scheme grant of £5000 available (via the installer) which brings the price down somewhat. Note that this requires an EPC less than 10 years old with improvement recommendations such as cavity wall insulation completed (but further grants may be available for that work too).

"Which" kindly provides more info here: https://www.which.co.uk/reviews/home-grants/article/what-is-the-boiler-upgrade-scheme-a17ej8Q5SpJS

[funduffer]

So, like Howard has done, I have now just installed an air conditioning unit in my lounge.

It is a 3.5kW rated Daikin Emura, and it cost £1800 to install (all in). This means it generates a maximum of 3.5kW of heat, but of course, being driven by an ASHP, the input power is 25% of this, i.e. less than 1 kW at max power.

I have gas central heating via a Vaillant combi-boiler, which I am perfectly happy with. I also have a 4.225k PV solar system.

So why did I buy this Daikin unit?

1. To boost the temperature in the lounge during winter day time. I have solar power, which often leads to excess power in the middle of the day, even in winter. I can re-direct this into the Diakin unit, and therefore not switch on the central heating during the day and save gas. Yesterday, it was 1C outside, and cloudy. Yet during the middle part of the day, on an economy setting, I could keep the lounge at a comfortable 20C only using about 200W of net imported power. Yes, the rest of the house cooled down during the day, until the central heating kicked in late afternoon, but this is not much of an inconvenience as we spend most of the time in the lounge if we are at home during the day. The house is quite well insulated, so other rooms may cool from about 20C down to around 14C on a very cold winter's day.

2. My wife suffered badly during the heatwaves last summer. I expect, this summer, with my daytime excess solar power, to cool the lounge to a comfortable 20C using just excess solar power.

3. If we go away, or out for the day, all heating is switched off. Half an hour before I return home, I can switch on the Daikin unit via my phone, and arrive back to a toasty 20C lounge. The gas central heating would have taken a couple of hours to achieve this.

I haven't done a full financial analysis of this device yet, and it is early days - I am still learning how to use it. I suspect the business case for it will very much depend on the future relative prices of electricity and gas.

...but my wife is happy, and that is the best business case of all!

FD

[OhNoNotimAgain]

I installed a GSHP 12 years ago in a 300 yr old largely stone built house, converted from an agricultural building, in Scotland.

The GS is a 200 m deep borehole in Devonian volcanics that has good ground water circulation so gives excellent heat (i.e cold) exchange.

It is our only source of heating, save for the occasional use of a solid fuel stove, although we do have a solar hot water panel which is quite effective in the summer.

Annual consumption is about 22,000 Kwh/yr which on my current fixed tariff costs me £380/month.

Initially, it just fed radiators and it was OK, but not great. Six years ago we upgraded the core two rooms of the house and installed underfloor heating and that has made a huge difference. A steady 19 or 20 degrees in the kitchen.

I get an annual service that costs about £150. We have had some issues, such as pump failures and brine leaks, so I would urge users to take out a maintenance contract otherwise no one will turn up if you get a failure.

When it is cold, like -1 or below, the 7KW immersion kicks in and that does make a huge difference to consumption but those occasions are quite rare.