Air (and Ground) Source Heat Pumps

[Clariman]

Are air source heat pumps as good as they sound? We visited a new build property the other day and all the heating and hot water came from one. The houses on the development are large and the site manager (not sales person) said that one of the new home owners has said her monthly bill is less than £90 for a 5 or 6 bedroom hours with large rooms.

Do they completely replace a conventional boiler and your only costs are electricity for lighting and cooking etc.?

Thanks

[9873210]

Are air source heat pumps as good as they sound? We visited a new build property the other day and all the heating and hot water came from one. The houses on the development are large and the site manager (not sales person) said that one of the new home owners has said her monthly bill is less than £90 for a 5 or 6 bedroom hours with large rooms.

Do they completely replace a conventional boiler and your only costs are electricity for lighting and cooking etc.?

Thanks

Heat pumps can definitely replace all other heating sources. They work in Ontario or Manitoba, so the English climate is a piece of cake. Although the colder the climate the more it favours ground source heat pumps over air source heat pumps.

I may be misreading your question, but a heat pump consumes electricity. You have to pay for that in addition to any used for light and cooking. Typically a heat pump will output something like 3 or 4 times the amount of heat as electricity it consumes.
(Energy is conserved because the heat comes from the outside air, entropy still increases because the low grade heat has less enthalpy than the electricity used.)

Low energy bills on a new build are likely to be more due to high build quality, with good insulation and airtightness than the heat pump per se. Or possibly fibbing, the claims are plausible, but you really need to check build quality and/or the builders reputation.

[Urbandreamer]

Are air source heat pumps as good as they sound?

It really depends upon what you are hearing. They are a lot better then some claim, and nowhere near as good as others claim.
A well specified one should save energy. There is also no good reason for it to cost a mint, given that almost all homes have at least one, called either a fridge or a freezer. However given that they need to do significantly more work, they will cost proportionally more.

A few things that spring to mind when talking whole house heat pumps.

1) They are very dependent upon location and installation options.
2) Air source heat pumps need to move a significant amount of air, so there will be fan noise.
3) Ground source need significant area for the collector, which the owner shouldn't dig to plant roses etc.
4) It's probable that their capacity will be limited by compromises, so top up heating will likely be required (at least on the hot water).

In warmer climates it's not uncommon to fit them to cool a house. Think of the ones used for heating as somewhat similar.

Maintenance costs and replacement parts? Well that comes down to volume. Places where everyone fits air-con have large numbers of people who maintain them and parts are mass produced. The heat pump industry is not there yet in this country, but I suspect that it will be in a decade or two.

Re new build. There are many more options on the table at that point. Structures can be designed to take the weight and absorb any vibrations of a fan unit. Pipe runs can be designed in and are easy to do during the build. As said insulation, including under floor insulation and wall insulation is easy to build in.

[Clariman]

Sorry I posted in the middle of the night when half asleep.

I meant to ask about

ground source heat pumps

[Mike4]

Are air source heat pumps as good as they sound?

It really depends upon what you are hearing. They are a lot better then some claim, and nowhere near as good as others claim.
A well specified one should save energy. There is also no good reason for it to cost a mint, given that almost all homes have at least one, called either a fridge or a freezer. However given that they need to do significantly more work, they will cost proportionally more.

A few things that spring to mind when talking whole house heat pumps.

1) They are very dependent upon location and installation options.
2) Air source heat pumps need to move a significant amount of air, so there will be fan noise.
3) Ground source need significant area for the collector, which the owner shouldn't dig to plant roses etc.
4) It's probable that their capacity will be limited by compromises, so top up heating will likely be required (at least on the hot water).

In warmer climates it's not uncommon to fit them to cool a house. Think of the ones used for heating as somewhat similar.

Maintenance costs and replacement parts? Well that comes down to volume. Places where everyone fits air-con have large numbers of people who maintain them and parts are mass produced. The heat pump industry is not there yet in this country, but I suspect that it will be in a decade or two.

Re new build. There are many more options on the table at that point. Structures can be designed to take the weight and absorb any vibrations of a fan unit. Pipe runs can be designed in and are easy to do during the build. As said insulation, including under floor insulation and wall insulation is easy to build in.

A couple of points.

1) Let's not confuse saving energy with saving money. Yes the ASHP uses one third of the energy of a gas boiler, but that energy is electricity now instead of gas, and electricity costs 3.5 times the price of gas so any anticipated cost savings are probably an illusion.

2) Lets not confuse "air to water" heap pumps with "air to air" heat pumps. Only the latter will cool the house in summer, and most heat pumps fitted in new build houses will be the "air to water" type. They need to be "air to water" in order to heat up the hot water tank and radiators that buyers of such houses expect.

[scrumpyjack]

Are air source heat pumps as good as they sound? We visited a new build property the other day and all the heating and hot water came from one. The houses on the development are large and the site manager (not sales person) said that one of the new home owners has said her monthly bill is less than £90 for a 5 or 6 bedroom hours with large rooms.

Do they completely replace a conventional boiler and your only costs are electricity for lighting and cooking etc.?

Thanks

Heat pumps can definitely replace all other heating sources. They work in Ontario or Manitoba, so the English climate is a piece of cake. Although the colder the climate the more it favours ground source heat pumps over air source heat pumps.

I may be misreading your question, but a heat pump consumes electricity. You have to pay for that in addition to any used for light and cooking. Typically a heat pump will output something like 3 or 4 times the amount of heat as electricity it consumes.
(Energy is conserved because the heat comes from the outside air, entropy still increases because the low grade heat has less enthalpy than the electricity used.)

Low energy bills on a new build are likely to be more due to high build quality, with good insulation and airtightness than the heat pump per se. Or possibly fibbing, the claims are plausible, but you really need to check build quality and/or the builders reputation.

I have a heat pump and oil boiler both of which heat the pool. I can use either or both. I have found it cheaper to use oil!
Of course it all depends on the price of oil and the price of electricity. At present oil is about 78p per litre and a litre of heating oil produces 10.35kw of energy, ie about 7p per kw. Electricity is a lot more than 3 times that, and of course the efficiency of a heat pump reduces when the outside temperature is cold, which is when you want the heat! A modern house can be much much more efficiently insulated of course and be much less drafty.

So I agree the stories of very low heating costs are down to effective insulation, rather than the source of the heat.

To get heat pumps really going we need very cheap electricity so that it is much cheaper than gas or oil heating. Roll on fusion power, or in the meantime wind + storage

[AsleepInYorkshire]

Are air source heat pumps as good as they sound? We visited a new build property the other day and all the heating and hot water came from one. The houses on the development are large and the site manager (not sales person) said that one of the new home owners has said her monthly bill is less than £90 for a 5 or 6 bedroom hours with large rooms.

Do they completely replace a conventional boiler and your only costs are electricity for lighting and cooking etc.?

Thanks

Good morning,

Seasonal greetings and warm wishes for a great start to 2023.

The market leaders for air source heat pumps (ASHP) are Mitsubishi and Daikin.

When last I spoke with a large company in Lincoln who offer either product to the residential sector they indicated that they favoured Mitsubishi over Daikin for reliability and maintenance costs. Many housing associations have the same outlook despite Mitsubishi being a more expensive solution. ASHP's are most efficient when used in conjunction with underfloor heating (UFH). However, it should be noted that there should be sufficient zones within a larger house to achieve this kind of efficiency and UFH has a delay when it is turned on and off.

Five years ago I did some work for a company that specialised in developing large bespoke, architecturally designed, new homes ranging in price from £800K to £1.8M. They didn't use ASHP's but were looking into incorporating it into their homes at some time in the future. We had a meeting with a local company and a look around their sales area. At the time they were working for a customer who had made some money singing. The interesting part about ASHP's is they can also provide cooling in summer if the correct ducting is installed.

ASHP's have an input/output ratio. For example 2.2KW's will be fed into the unit with somewhere between 4-5 KW's coming out. A modern gas boiler can achieve 80%+ efficiency. An ASHP over 300%. Here's a little more on that.

I seriously doubt that the Site Manager would have a clue as to the costs involved in heating in a new home and has already been mentioned the costs will be reduced by the level of insulation installed throughout modern homes as a requirement under the Building Regulations. Modern homes also have to pass air tests to ensure they are sealed from draughts. Both work to reduce the amount of heat needed to warm a house.

If you are considering purchasing a new home my strongest advice is to ensure the build quality meets the standards required. Employing your own inspector is worth the cost. Do not rely on the developers quality control process alone, unless they have already received, for example, an NHBC Price in the Job Award. I'm not familiar with any other awards that would give me complete confidence in the workmanship and other standards achieved on site.

Here's one of the new homes I worked on - just for bragging rights of course


Hopefully that's given you something to work with, but happy to answer any questions you have or at least point you in the right direction.

Take care

AiY(D)

[AsleepInYorkshire]

Sorry I posted in the middle of the night when half asleep.

I meant to ask about

ground source heat pumps

https://www.greenmatch.co.uk/heat-pump/ ... -in-the-uk

AiY(D)

[Mike4]

The interesting part about ASHP's is they can also provide cooling in summer if the correct ducting is installed.

For the second time in this thread I feel driven to point out this is not necessarily true.

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.

[AsleepInYorkshire]

The interesting part about ASHP's is they can also provide cooling in summer if the correct ducting is installed.

For the second time in this thread I feel driven to point out this is not necessarily true.

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.

Thanks for the clarification Mike

Take care

AiY(D)

[DrFfybes]

Are air source heat pumps as good as they sound? We visited a new build property the other day and all the heating and hot water came from one. The houses on the development are large and the site manager (not sales person) said that one of the new home owners has said her monthly bill is less than £90 for a 5 or 6 bedroom hours with large rooms.

Thanks

I would suggest that figure is not at all representative of the energy use of the home at current rates.

£90 a month is £3 per day. That is 8.5kWh after the standing charge has been paid. We use about 10kWh/day, we have a fish tank, but don't use a tumble drier., LED lights, ........ and gas central heating.

The lady might have had her monthly payments set at that based on predicted (or measured) summer use, but there is no way at all that £90/month is going to heat her home all year around no matter how efficient the heating system and insulation. The only possible caveat is that there is another source of energy not mentioned, such as a large solar panel array.

Paul

[scotview]

but there is no way at all that £90/month

Paul

Good point.

Why cannot the likes of Ofgem post some reliable figures on heat pumps (all varieties), gas boilers, oil boilers, wood burners, to give Joe public at least
some comparative performance/cost guidelines. It doesn't need to be to the nth degree of accuracy. There's so much dubious sales stuff out there.

[AF62]

Why cannot the likes of Ofgem post some reliable figures on heat pumps (all varieties), gas boilers, oil boilers, wood burners, to give Joe public at least some comparative performance/cost guidelines. It doesn't need to be to the nth degree of accuracy. There's so much dubious sales stuff out there.

Probably because the numbers would not prop up the government political agenda.

Let's do some 'back of the cigarette packet' calculations.

Ofgem say that the average household uses 12,000 kWh of gas a year, and lets assume almost all of that is used for heating the home and water.

With a gas boiler at (say) a 90% efficiency and gas at the current rate of 10p kWh then that is £1,080 a year (or £90 a month).

Now lots of spurious figures are quoted for the efficiency of ASHPs but they mostly steering away from the issue that their efficiency falls off dramatically when air temperatures fall below 7C - exactly when you need the central heating to work!

But lets be generous and say a COP of 2.5, which would mean you would need 4,320 kWh of electricity to run the ASHP to match the 10,800 kWh output you got from your 90% efficiency gas boiler, and so with electricity at the current rate of 34p kWh that is £1,468 per year (or £122 a month).

Trying to sell someone an expensive ASHP which will cost 36% more to run - no wonder they don't publish the details.

[88V8]

I meant to ask about
ground source heat pumps

The people up the road have a ground-source pump. It has a collector loop under their umpteen-acre field.
It's heating a new-build wing from about ten years ago, well insulated. Heat pumps only work with a high level of insulation, and it wasn't feasible to heat their existing 300yo house with it.

We have no mains gas, so at the time their options were oil or LPG or electric.

Even before the energy price rises, the cost of pumping the water around the ground loop was very high. And when the temperature is low, it actually uses more electricity keeping the water from freezing.

I'll ask next time I see them how the economics are panning out.

V8

[richlist]

Why did they use a wet system ? Air sourced heat pumps using air to air are a good alternative.

[DrFfybes]

Let's do some 'back of the cigarette packet' calculations.

Ofgem say that the average household uses 12,000 kWh of gas a year, and lets assume almost all of that is used for heating the home and water.

With a gas boiler at (say) a 90% efficiency and gas at the current rate of 10p kWh then that is £1,080 a year (or £90 a month).

90%???

Aye, in an ideal laboratory setting. I don't reckon our new condensing boiler rated at 93% or so uses any less gas than the 35+ year old 60-odd% efficient one we replaced. Except for the pilot light - that was about 50% of our summer gas use. I'm doing meter readings more often now thoug, and in the last 8 days the daily gas use has only been 25% more than the previous fortnight, despite the colder weather. Time will tell.

Paul

[88V8]

Why did they use a wet system ? Air sourced heat pumps using air to air are a good alternative.

They had the field.
And they're not very technical.
Their architect recommended a wet system, and there it is. The same architect ran the ufh under their kitchen cabinets - yes he was also responsible for the kitchen layout so this wasn't a case of the right hand and left hand - so it may be that he had an imperfect understanding of how it all worked.

V8

[9873210]

Ofgem say that the average household uses 12,000 kWh of gas a year, and lets assume almost all of that is used for heating the home and water.

With a gas boiler at (say) a 90% efficiency and gas at the current rate of 10p kWh then that is £1,080 a year (or £90 a month).

You multiplied instead of divided.

If you use 12,000 kWh of gas at 10p/kWh thats £1,200 per year.

If you need 12,000 kWh of heat you will use 12,000/90% = 13,333 kWh of gas per hear costing £1,333.

Now lots of spurious figures are quoted for the efficiency of ASHPs but they mostly steering away from the issue that their efficiency falls off dramatically when air temperatures fall below 7C - exactly when you need the central heating to work!

At least some heat pumps will work at a COP of 4 down to about 0C. With a COP of perhaps 6 at 7C. It's a trade off between the cost of the heat pump (more efficient is more expensive) v. energy use (more efficient uses less energy). Typically you want to size it so that supplementary resistance heat is used on the coldest few nights a year, but you could avoid this if you want to.

There is also a myth that heat pumps can't provide heat quickly. If you use a 30BTU/hr heat pump (and they are available) it will heat up almost as quickly as a 30BTU/hr boiler (There may be a few minutes delay, but not more than that). Again it's a trade off of capacity v. cost.

Insulation also matters. A well insulated house does not have the temperature swings of the typical drafty and uninsulated Elizabethan. The traditional method of only heating the room you are in while you are in it assumes that things cool down fast when you turn the heat off. With a properly insulated house things will only cool down a degree or two overnight. In which case turning the heat off for most of the day just isn't that useful.

[Howard]

I'm sitting in a room warmed by an ASHP at the moment. Minus 4 degrees outside. We let our house cool down overnight. Installed as an aircon, but amazingly good at bringing a cool room up to temperature for a few pence. And cheaper than turning up the gas central heating.

Out of interest I ventured outside to listen to it dealing with low temperatures. It is marginally noisier as it goes through a coil warming cycle but still incredibly quiet given the effect indoors.

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

[scotview]

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.