Time to stop promoting air source heat pumps and ask why they don’t work in the UK

(24th July 2013. Several commenters have kindly provided detailed analysis of some of the reasons why air-to-water heat pumps may be costly to operate. Others state that the technology is not at fault and blame the poor quality of the installation. Thank you very much to all those who have given time and thought to this issue. May I strongly recommend reading the full range of comments below the text? Chris)


When temperatures in the British Isles drop to unexpectedly low levels, the pattern of traffic on this web site changes. One set of search terms dominates the inquiries. Readers are looking for information on why their air source heat pump is costing so much money to run. Sold to them as a way of saving cash, readers often seem to find that the price of heating their home has suddenly increased, sometimes quite dramatically. And, moreover, the pumps don’t heat the house properly.

Today (March 25th 2013) is unusually cold across Britain and the search term ‘problems with air source heat pump’ is the single most common inquiry. Colder countries that have been using heat pumps for decades seem to be able to install them in ways that mean that homes have inexpensive and reliable heating. In the UK, with its badly insulated houses, air source heat pumps seem to be a complete disaster for many unlucky purchasers.

Below, I copy a letter I’ve just received from a lady living in the Orkneys off the northern tip of Scotland giving her experiences. Readers may also be interested in the comments added at the end of a previous post on heat pumps, including the most recent one from Jane Smith, submitted today. Despite the increasing evidence of systematic problems with air source heat pumps, government bodies such as the Energy Savings Trust continue to say that they will save money for householders living off the gas grid. Heat pumps are also part of DECC’s ‘Renewable Heat Incentive’, a scheme that is intended to subsidise the installation of suitable and effective technologies for householders. The continuing official support for heat pumps in the face of repeated failure needs to be challenged.

(Published with permission from Ms Switsur)

Hi Chris,

I don’t need a reply to this, I am just having a grouch which might interest you.

AIR SOURCE HEAT PUMPS are USELESS for anyone on a low income. I am 72. I have £130 a week total income (Pension and Pension Credit). My house had no central heating. The Energy Savings Trust conned me into having the Government Grant of £6800 and paying £2000 extra myself to have air source central heating.

It took 11 months to install because the plumber obviously didn’t know what he was about.

The first winter my leccy bill was nearly £400, and I thought it was my fault for not using the system properly, and it took me a very long time to realise that the installer had left the hot water boost permanently on.

This winter I really, really tried to economise, turning rads down and only having it on in the cheap periods. Result? a bill of £420. As I also had unexpected vets bills and an insurance excess of £250 to pay because my car slid in the snow and did some damage, I could not pay the bill – there is only £90 left to pay but (the suppliers) are saying they will cut the leccy off if I don’t sign up to their payment scheme. I can’t afford their payment scheme anyway because it is double my weekly payment.

My electricity costs are now more than 20% of my total income even thought I was promised I would save money. I HAVE SWITCHED THE SYSTEM OFF and gone back to coal. 11 months of torture while the thing was installed, £2000 of debt to pay my share, and I am back exactly where I started.

Please do advise people on low incomes not to bother with it. It didn’t heat the house adequately in cold weather anyway.

Thank goodness I have an open fire!

Regards, Julie

Julie Switsur Ardage Burray Orkney KW17 2SS 

  1. Robert Duncan’s avatar

    Hi Martin,

    Very kind. Will try drop in to see you in early October, when I’m next up; it would be great to actually see what is being discussed.

    Thanks a lot for the advice … subsequent posts here (eg Carl) and some of the earlier ones are enough to put me off though (also considering solar/wind, so the budget might be best set in that direction first!).

    All the best,


  2. Martin H’s avatar

    Hi Robert, not a problem about you visiting in October, I do not know why Carl etc. have such a problem with ASHP, just remember we are talking Air to Air HP’s. There are 3 at the local bank here since 2002, still going strong.
    If I thought they were rubbish I would tell you.

    Definitely a wind turbine for Caithness if you are looking to generate power (in winter), I know of people who are getting them installed for “free”, apparently they will get free electricity for allowing the “Company?” to erect Turbines on their land I will try to get more info for you.. I am not sure of the size of the towers etc. though. Storage of electricity should form part of investigation. I have read of people with Forklift Batteries for storage, Hornet Turbines information (I think).

    Regards Martin

  3. Paul D’s avatar

    Martin H on Tuesday 15 April 2014 at 8.35pm

    ‘We are all electric, and also suffered from the exorbitant costs of storage heating. Am I happy with the Mitsubishi’s? Definitely.’
    Mine is still delivering as well. About £127 for this winter’s heating.

    ‘There used to be a Guy on this forum who gave “Free calculations” for ASHP and costs etc, Paul D. You might be able to source some from past posts.’
    ‘Used to be’?

    Paul D

  4. Brian W’s avatar

    Something I’ve just discovered about my ASHP – two years after it was installed (Hitachi Yutaki) in a new build house: the supplier is now trying to sell me an annual maintenance contract at £500p.a., having provided sales information that ASHP require very little maintenance. But they say the annual maintenance contract is required as a condition of the warranty!
    So that’s £500 straight onto my total cost of heating.

  5. Paul D’s avatar

    Brian W,
    If the pump is two years old, then how long does the warranty last?

  6. Martin H’s avatar

    Sincere apologies Paul D, I am not sure I receive all the Posts. Anyway I see there are negative comments regarding ASHP’s but with my A2A in comparison to Storage Heating costs, I definitely cannot complain.

    It looks like I will have someone (Robert) come to see my Mitsubishi’s in action in October, that’s about the time it starts to cool down here

    Thanks for all the information and previous correspondence, it helped me make the RIGHT decision regarding ASHP’s.

    Anyway Paul D, glad to see your not a “Used to be” on this Forum.


  7. Paul D’s avatar

    Martin H,
    No apologies necessary; I am not sitting on a cloud just yet. I have been awful busy elsewhere for quite a while but I have learnt a lot in the process. That work has tailed off now and I am just starting to catch up here. I now know how an installer can make a heat pump cost £1000s a year to run and that on the basis of the evidence. Collecting the evidence has been expensive, hard, time-consuming graft.

    Take an A2W heat pump with a 5kW motor and make it run continuously. That is roughly 5*0.15*24*30=£540 per 30 day month or about £2500 for a winter. I was quoted a 10kW pump for my house with the same problem, so that would be a bill for £5000 for a winter. Instead, my pump (at 450watt(electrical) capacity) electricity bill has been about £127 for this winter and the gas boiler has hardly been used for space heating. There is a bit of daylight between those two, I think you will agree, but the gap is entirely rational and in accordance with the laws of physics.

    A lady from Aberdeenshire posted earlier; was it £900 for two months? Probably had a 5kW motor as well. I think that she wanted a genius to explain it; actually she only needed an engineer. Once you understand, it is dead simple.

    What I still do not understand is why the government is pushing this rubbish. That will be simple as well, when I get to the bottom of it. My MP tells me that I have been invited to a meeting at DECC; no agenda as yet. The Minister told Parliament in December that he had not heard of any hardship cases with heat pumps. He obviously does not read this blog.


  8. nik sargent’s avatar

    Been reading this with interest so thought i’d take my turn to poke the hornet’s nest with a few observations…

    1. A large thrust of complaints seem to be about cost and efficiency. The government’s scheme, by its very title, is about renewables. Anything – ANYTHING – that plugs into the grid is going to assist renewable energy strategy as the grid becomes cleaner and cleaner. Even if the grid is only 1% renewables, it’s 1% more than fossil fuel. That % will continue to increase for the grid but not for fossil fuel.

    2 furthermore, anything powered from the grid could be partially or wholly powered by solar thus becoming up to 100% renewable and up to 100% free (eventually).

    3 people are very focused on personal cost and not the big picture. The big picture about climate change is not about the cost of your personal energy supply but about trying to limit how much we screw up the planet. There is going to be pain at every level, either in doing something, or probably worse: not doing something. time to wake up!

    A renewables energy strategy, then, is not what about what it costs you to keep warm; the technology options are not about magically delivering nearly free energy – because if that’s what they did, everyone would want one. The very fact the government is providing a subsidy by pure logic alone, suggests the solutions are not expected to deliver huge cost savings, and therefore consumers must be encouraged to jump ship, to a technology that is strategically aligned to national energy strategy.

    4 the physics is sound – so if there is really such a disastrous history with ASHP, then it points to manufacture/design and installation as the problem. Therefore this is an industry delivery (immaturity) problem, not a technology one per se. Time for the industry voices to stop moaning and start dragging it out of the 19th century and into the 21st. It’ll take time; meanwhile buyer beware.

    5 indeed we have an installer and manufacturer bemoaning the technology/industry/(not sure what exactly). Their experience is clearly vast – but it’s not really clear if this is an objective or subjective viewpoint. For sure, it’s always going to be in someone’s interest to stifle ASHP, just as it’s in someone else’s to promote it.

    6 No one is really comparing apples with apples as so many parameters are variable. Let’s take that last calculation. I can’t understand why anyone would (or would need to) run 5kw non stop per day every day, unless you actually don’t have a roof!
    To put a stake in the ground, take a 10yr old house with an average annual heat usage of about 140kwh per square metre per annum, size about 125metres sq. That’s a decent UK family 4/5 bed home. Total 17.5megawatt hours per annum.
    By comparison, 5kw continuous is 43.8megwatt hours per annum!!! Clearly if you need that kind of energy input there is something woefully wrong…
    But, I assume we were just talking winter, quoting about 5 months of non stop usage, ie 18.2mwh – that’s above total annual usage for the kind of property I’ve described – clearly not comparing apples with apples. Which sadly makes these anecdotes a bit worthless unless all the parameters are described IMHO.
    Let’s remember too, that we’re talking input power here, not output, so the example assumes to all intents and purposes a COP of 1! Obviously such a comparison is going to look unfavourable. Maybe this is to allow for winter – but it still seems unduly conservative to me.

    7 it surprises me that anyone considers oil as a sensible option if they are choosing one now. Its price has more or less doubled in the last 5 yrs. Any guesses what will happen in the next 10 or 20?

    8 I think that’s enough poking for now ;)

  9. Paul D’s avatar

    nik sargent on Tuesday 22 April 2014 at 12.46am
    I’ll buzz around a bit, if I may?

    1: I and the vast majority of people on a tight budget, I suspect, respond to the normal commercial signals of price and quality; in this case heat at lowest unit cost.

    2: Everything you plug into the grid has to be matched by generation. A lot of the generation is to be gas-fired (75%) with wind turbine economisers (25%) until (and if) the storage problem is solved. The problem with the economisers is that they cost a fortune and would not be built without massive subsidies from the real economy; a bit of contradiction there.

    3: True. You are not going to be able to sell that argument in the mass market, I am sure, and I am not about to panic and start buying junk kit.

    4.1: Defective pumps:
    These pumps with ridiculous bills are supplied and installed by the industry. The legal process for consumers to get their money back certainly needs more explanation; there are consumer mis-selling and fitness-for-purpose issues in here. The real fix is for people not to buy this junk in the first place.

    4.2: High Temperature Retrofit Heat pumps as pushed by the Domestic RHI:
    Pumping unnecessarily to high temperature wastes serious money and the level of inefficiency involved is characterised by the CoP. I tested an A2W pump this winter that had a CoP of 1.64 because it pumped to 60C. There is an advert on the web for an A2W with a CoP of 5.8 but that is rated at 25C because it is a swimming pool pump. The 5.8/1.64=3.5 ratio in CoP reflects directly into the unit cost of operating these pumps. The subsidy on high temperature pumps does not outweigh the extra electricity costs; you actually lose money by buying one of these things, as compared to running a high(5.5+) CoP A2A.

    5: They write the truth about A2W, as far as I am concerned; A2A is different.

    6: ‘I can’t understand why anyone would (or would need to) run 5kw non stop per day every day .. ‘
    May I explain? :-
    6.1: The first answer to this is that this is what the installer supplied; an installation where the pump runs continuously at normal winter temperatures.

    6.2: The second answer is that a high temperature retrofit A2W heat pump replaces a fossil-fired boiler. Once the fossil-fired boiler is removed and placed on the van, the consumer cannot reverse course, even if he/she realised. When temperatures drop in the autumn and the pump starts running continuously at about 5C most people still do not realise. It is the first winter quarter bill that signals alarm. The lady in Aberdeenshire posted in February after two months of high power consumption; was it the bill that triggered the post? Normally, people also complain that the pump does not heat the house properly.

    People run these pumps because it can be really cold in winter, the installer does not have a clue how to fix it and the good, old boiler left months ago on the van.. The roof does not matter that much to the temperature in the house if the heating is off.

    6.3: ‘Which sadly makes these anecdotes a bit worthless unless all the parameters are described IMHO.’
    Please rest assured that the engineering reports submitted to due legal process do describe all the parameters in minute detail.

    7: Returning to oil can be a sensible option when you have had the searing experience of being sold one of these defective pump installations. There are numerous cases reported where heat pump installations have been removed from social housing because the tenants cannot afford the bills.

    8: IMHO the government, DECC, the EST and the cowboys are killing the reputation of this industry. There are good, honest, effective installers out there. The problem is finding them and MCS is no guarantee.

  10. Steve Connolly’s avatar

    Your comments are very valid. There is a huge lack of understanding about the refrigeration principles which underpin heat pumps.

    As a rule of thumb it can be said when it comes to heat pumps that “the higher the temperature-lift, the worse the efficiency” For example a heat pump that operates in a 12 DegC ambient and which provides 35 DegC water to an underfloor system will be pretty good from an efficiency angle. Whereas a heat pump operating in 2 DegC ambient and producing 50 DegC water for a radiator system will be pretty lousy from an efficiency standpoint.

    What buyers need to be especially aware of however is that most installers don’t actually take account of this basic fact in their designs. Instead they install systems that produce water at 50 DegC all the time (in order to meet the higher temperatures needed for bath water) and then they install mixing valves to blend the water back down to 35 DegC for the UFH circuit.

    One other thing that the entire industry has got WRONG is the choice of refrigerants in these machines. Buyers should be aware that 99.9% of heat pumps are supplied with R134, R407 and R410 refrigerants. These gases are in fact in the process of being phased out, and so it should be understood that heat pumps fitted with these gasses are already on the road towards being obsolete.

    The domestic heat pump industry is getting itself an even worse reputation than the one that the double glazing industry used to have.

  11. Nik Sargent’s avatar

    Hi Paul, to reply to that:

    1: yes, of course, consumers respond in a personal way. So, do ones sums, not just on the cost now, but the whole life costs of whatever system you are considering, factoring in possible future fuel costs. I’m factoring in the addition of solar generated electricity to my own personal circumstance. No one size fits all.

    2: This argument is tactical (“of the moment”). How come scotland claims to generate it’s energy with almost 50% renewables? Are they lying?
    The energy landscape is most clearly not static, nor can it be. If we consider how energy is going to be produced in 10 years, 20 years, 30 years, it will have changed. If I stick an oil tank in my back garden, it won’t.

    Solar is going to be the massive disruptive force once the next few iterations of the capture technology bear fruit – some recent advances in the lab not only include stepwise efficiency gains and production cost reductions, but last week moving droplets across a PV style surface was shown to generate charge. Yes, it will take time, but abundant, clean, free energy is there to be had..

    if the stats are to be believed, fossil fuel subsidies ($500Bn globally) far outweigh those for renewables – http://en.wikipedia.org/wiki/Energy_subsidies – so at face value at least, the subsidy argument seems entirely bogus.

    4: there is a common theme here that retrofit seems like a lousy option. As a message that’s easy for consumers to understand. But the issue I have is that the general approach seems to be tar everything with the same brush. The message that it’s *all* lousy doesn’t seem helpful.

    What’s also being forgotten is use cases. My parents (West Highlands) run on coal and electric. Their annual bills are eye watering. The absolute best they can ever achieve in terms of “efficiency” is a COP of 1 (12Kw boiler). If he had a heat pump that delivered COP of a mere 1.64 he would jump for joy.

    The actual barrier to doing this is the cost of whole-system redesign/replacement (e.g. new radiators).. again, we are back to the issue of retrofit, not the fact that improved performance can’t be delivered.

    6: I think my point was missed. Why do you need to pump that much energy in total into the building? (by whatever means/source?) It is a staggering amount – what type of building is it? One can quote any arbitrary example to support either a negative or positive viewpoint, but unless the context is clear, no-one can make an informed judgement on it.

    8: I respect your opinion, and sums up the whole of this argument quite nicely: actually. these systems can work really well, but the industry is completely immature with them.
    How is it going to get mature?

    Here’s the thing – it has been useful to discover this page and read the views. My system has not been designed and installed yet. What I recognise is that I need to have all the rights bits, all the right design and have it all done properly, and I need my finger in every one of those pies.

    The challenge I have is that the “it’s all a disaster, avoid, avoid” message doesn’t help those of us brave (stupid?) enough to take this on with the determination to make it work, though certainly it raises my caution levels.

    I may come to eat my words in future if it turns out to be a disaster, but actually i haven’t been put off. A specific discussion about what’s good and bad, what works and doesn’t would be more helpful than generalisations IMHO. :)

  12. carl m’s avatar

    The ” bigger picture ”

    You will never get people in the UK to look past the end of their noses with this issue.

    They aren’t interested unless there is something in it for them i.e, a big fast buck right now, not in a few years or even a few months, right this minute.

    Cost, cost, cost is all people ever think about

    If the choice is between a new heating system or a new 4×4 then you know what the obvious choice is.

    And the real sad fact is that this technology could work at a very reasonable cost to the end user if only there wasn’t so many people in it for a fast buck as well, people such as so called experts will little or no experience, greedy manufacturers fleecing the UK consumer with extortionate prices for their products and then there are all the government agencies and different qwangos involved all poking their fat greasy snouts in the trough wanting a slice of the cake and at the same time creating a red tape and over regulation nightmare.

    As usual the bullshitters and petty crooks have messed it all up in the pursuit of £££££££££££

    I used to run my own renewables company but gave up the hassle and went back to traditional heating services.

    Best of luck mate



  13. carl m’s avatar

    I don’t have a particular problem with ASHP’s , I was just telling the truth about the whole situation in the UK with the renewables industry.

    As with anything new in the UK, it has been hijacked by the usual conmen, greedy manufacturers even greedier politicians.

    There are very few installers with the necessary expertise to ensure that people get what they need at a reasonable cost.

    ASHP’s are unsuitable for retrofit installation into most of the crappy housing stock in this country unless of course you think that standard brick built poorly insulated homes with typical standard wet radiator heating systems are suitable for connection to an air to water heat pump without some major alterations to the existing heating system and insulating that home to the standard required to ensure that the pump works in a cost effective manner.

    ASHP are only really any good when installed on underfloor heating in a new build low carbon home.

    Oh and save some cash for a ten year extended warranty.

    That’s all I was trying to say really, because that’s the reality.

    Anyone that disagrees must be talking about another planet

  14. Nik Sargent’s avatar

    “ASHP are only really any good when installed on underfloor heating in a new build low carbon home.”

    Thanks Carl – that’s actually all I needed to know, cos that’s exactly my use case :)

    Similarly we concluded that for my parents, as a retrofit to a 1970′s prefab build in the Highlands, it would not make sense whatsoever…

  15. Brian W’s avatar

    In reply to Paul D
    The system was installed in 2012, commissioned in October 2012. The warranty is 5 years.
    Finding a local service agent is proving impossible.

  16. Martin H’s avatar

    Martin H,
    Glad you are not sitting in the clouds. I hope that when collecting the evidence that it has not has been at your own personal expense? My Mitsubishi (in the loft) cost about +- £1 per day and believe me I was delighted with that, the storage heating was ruining me financially, and they were running on “Cheap Rate”?

    Shocking to hear about the A2W £540 per 30 day month / £2500 for a winter! Definitely not affordable heating eh? Your personal £127 for winter heating — wow! I would need to climb into the loft to see what that unit used I checked it nearer the beginning of the month , and it was at £187 since mid August but it was off for a few days due to a 0deg C temperature in the loft.

    Why is the government pushing the A2W rubbish? We can only hope you do manage to get to the bottom of it. Good luck at the DECC, do you think it will make the National Newspapers? When I worked in Africa they would say you are peeing against the wind when they expected the Status Quo to continue? I hope this is not the case with you!.
    I am sure you will put the Minister right about hardship hardship cases and heat pumps. There was an article on the news about people in Caithness, too proud to go to food banks and sitting in unheated houses. A good A2A situated properly, installed £1500 perhaps, this is probably less than the Grant for A2W installation by “Accredited” installers. Something is wrong somewhere?

    Anyway it’s time to get off your cloud and get back to some real work answering the bloggers on Carbon Commentary.
    Keep well Paul D

  17. Robert Duncan’s avatar

    Thanks Martin – sounds encouraging. Hope to see you later in the year and good luck to all those on here wrestling with all this.


  18. Paul D’s avatar

    Steve Connolly on Tuesday 22 April 2014 at 8.07am

    1: Firstly, I would like to thank you for your comments re the phase-out of R410 and the likely change to transcritical pumps with R477(CO2). This explains a lot about the government’s behaviour re heat pumps. Their primary tactic is to hide the A2A pumps that produce heat at lower cost than A2W and they are none too willing to talk about why. This begs the question as to whether or not an R477 A2A can be approved for domestic use. Some stuff I have read says that R477 is well suited to car air-conditioners, for example (what about the crash resistance?).

    This piece of information re R477 should IMMEDIATELY change any prospective purchaser’s view of buying a heat pump that might be expected to last 25 years. It is likely to be obsolete well before that.

    2: To take your numbers (12/35) and (2/50) and put them through Carnot’s Law gives theoretical maximum efficiencies of :-
    1: CoP(12/35)=(273+35)/(35-12)=308/23=13.39
    2: CoP(2/50)=(273+50)/(50-2)=323/48=6.73
    13.39/6.73=1.99 Call it a ratio of 2
    On theoretical grounds, Case 1: is twice as efficient as Case 2: and produces heat at half the cost.

    There are clearly a lot of people out there who do not want to know about that and I include Parliament, DECC and the EST. They prefer to double everyone’s heating bills instead.

    3: ‘Instead they install systems that produce water at 50 DegC all the time (in order to meet the higher temperatures needed for bath water) and then they install mixing valves to blend the water back down to 35 DegC for the UFH circuit.’

    I would regard any such system as unfit for purpose within the meaning of the relevant legislation. If the pump was installed by an MCS registered installer, the correct response from the pump owner should be to start up the RECC (www.recc.org.uk) dispute resolution procedure and get the thing sorted or get their money back. That is a total and utter disgrace.

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