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Review Of Heat Pump Running Costs

October 21, 2021

By Paul Homewood


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With the pressure on for the public to replace gas boilers with heat pumps, there has been a ramping up of puff pieces in the media. One in the Telegraph, for instance, suggested they were the best thing since sliced bread, with one chap saying they are cheaper to run and capable of keeping the house nice and warm.

Time then to review the costs, given the rise in energy costs this year.

To recap, this is how a heat pump works:




According to sites like Greenmatch, who are heavily promoting them, air source heat pumps (ASHP) will typically cost between £8000 and £18000 for a 2 to 3 bedroom house.  This excludes the cost of replacing radiators, extra insulation etc.

Because heat pumps use refrigerants to transfer heat, they can supply more heat energy than the input electricity. The measure of efficiency is known as COP:





We commonly hear the claim that ASHPs typically work to a COP of 3.0, but this is variable, dependent on the outside temperature. When it is mild, COPs of 4.0 can often be achieved; however you probably won’t even have the system switched on when it is so warm.

On the other hand, when it is freezing outside, the pump has to work much harder, and COP can easily drop well below 3.0.

Hence the need for the Seasonal Performance Factor (SPF), which measures the total useful heat that has been generated annually from the heat pump and then divided by the annual electricity consumption.

A survey by the Energy Saving Trust found an SPF average of 2.45, based on 44 homes spread geographically around Britain.

No extra insulation was fitted, other than a bit of pipe lagging and so on. The study was carried out in 2013, so more recent installations may be slightly more efficient. However, the installations  monitored in 2013 were deliberately engineered for best practice, including, for example, visits by manufacturers to check and advise on best practice.

It therefore seems unlikely that new installations now will be significantly more efficient.



GreenMatch, another site promoting heat pumps reckons that SPF would be 2.8, but this assumed a “well insulated house plus new radiators”.

So it seems reasonable to work on a figure of 2.6, without extra insulation.

So we can now start to work out running costs.

  • According to OFGEM, the latest price cap is set at 19.1p/KWh for electricity, and 3.8p /KWh for gas.
  • A typical house would use 15,000 kwh of gas a year, split 11,000 for heating and 4,000 for hot water.
  • Assuming an energy efficiency of 85%, a gas boiler would produce 9350 KWh of usable heat [11000 x 85%], at a gas cost of £418 pa [11000 x 3.8p].
  • In comparison, to produce the same 9350 KWh, a heat pump would use 3596 KWh of electricity, at a cost of £687.

Hot water poses an extra problem for the heat pump scenario, as a typical ASHP can only heat water to about 50C, well below the threshold of 60C, below which Legionella thrives.

There are various solutions, such as a separate immersion tank, or a top up system to superheat the ASHP water flow. But these and other alternatives will both cost money to install, and cost more to run than a gas boiler, as they would need electricity.

Even if all of the Environmental Levies were switched from electricity to gas, heat pumps would still be about £90 a year dearer to run.

  1. October 21, 2021 2:23 pm

    Decidely fits into the ‘No Brainer’ category.
    Unless your name is Kwazi Johnson

  2. 2hmp permalink
    October 21, 2021 2:44 pm

    And diabolically noisy even 50 feet from the house, in our case.

    • HotScot permalink
      October 21, 2021 4:27 pm

      Chafford 100 is the modern equivalent of a massive council estate in Essex, but all privately owned, mostly semi-detached.

      The clamour from even the quietest of these things operating at each house would be a health hazard in the colder months. Then there’s all the wood burners that would need to be installed.

      Talk about regressive, it would be like going back in time to when the council housing at the Clydeside shipyards were burning coal, and within earshot of the heavy industry.

  3. Ilma630 permalink
    October 21, 2021 2:57 pm

    This is hilarious. From an article in the Telegraph (, “XXXXX’s fan was installed on the outer wall of his kitchen. He says he can only hear it while standing in the garden. ‘It works hardest in winter, when you’re generally not using the garden anyway.”‘. As if you judge a heat pump for sitting the garden!!

    I also note the ‘savings’ example:
    £10,000-£2500 (gas boiler cost) = £7500.
    £350 (avg) saved per year.
    That’s >21 years before any saving, within which time it will no doubt have to be replaced, so not a saving at all!

    • HotScot permalink
      October 21, 2021 4:37 pm

      I wonder if they bothered to include the cost of new radiators (obviously not at that price) and to insulate the whole house, complete with mechanical ventilation (which also adds to the noise) redecoration, new carpets (assuming a decent underfloor ventilation system is installed) and possibly new kitchen/bathroom as, if the insulation is on the inside, they will all have to be ripped out. And whilst most modern homes have double glazing, numerous older ones don’t, so there goes another £10k.

      • Harry Passfield permalink
        October 21, 2021 6:56 pm

        HS: I’ve got 10 rads in my house and because of some mods to the layout I’ve just replaced three of them. That’s a little over £1k I won’t see again. But I shall have to do so all over again if I install an ASHP. So I lose again.

    • Phoenix44 permalink
      October 21, 2021 6:07 pm

      And who needs to have their gas boiler replaced? What’s proposed is we throw away perfectly good equipment in these examples.

      • Harry Passfield permalink
        October 21, 2021 7:04 pm

        If ‘they’ kill off my gas supply I shall be looking to run my boiler on bottled gas. I refuse to be DICTATED to. Especially by the likes of BJ and his wife. (Caroline Lucas is bad enough. Then, there’s Attenblox; Charlie and his son; anyone from the BBC environment dept (who have no qualification in CC); and Deben.)

  4. Jack Broughton permalink
    October 21, 2021 3:18 pm

    An unintended consequence of increasing the use of heat pumps is a large increase in the use of CFC type chemicals with the concomitant leakage during manufacture and when these fail or are replaced. It has been suggested that this leakage will dwarf any climate change forecasts.

    This technical issue , like the issue of massive increases of hydrogen, which threaten the ozone layer seriously don’t seem to have been picked-up yet by the over-hyped UK press whose only focus is CO2.

  5. HoxtonBoy permalink
    October 21, 2021 3:24 pm

    If you don’t use gas then the obvious solution is to leverage the existing infrastructure and use an electric boiler. This would use at least twice as much electricity as a heat pump but would give quick heat and hot water. When you consider the difference in installation cost – e.g about £15,000 it would take about 10 years for the heat pump to pay off. Not worth the disruption for anyone over 65..

  6. Jack Broughton permalink
    October 21, 2021 3:25 pm

    There was a good article in the Torygraph today recommending a referendum on net-zero and pointing out the similarity of the disconnect with that over Brexit, in that people will not vote to be poorer as with Switzerland. This is especially clear when there will be no effect on the world’s CO2 level of this massive waste of money or other benefit to the poorer people in the UK.

    If the eco-nut-nuts have their way we are on-course for war with China and India as a new wave of “holy wars” to save the planet.

    • Harry Passfield permalink
      October 21, 2021 3:44 pm

      Funny that. Just the other day I wrote to the DT to say the country needed a ref on ASHPs. They didn’t print my letter…..

    • Phil O'Sophical permalink
      October 21, 2021 6:21 pm

      It will never happen. After Brexit they will never trust the people again. And however tightly controlled, and whatever parameters we were allowed to vote upon, there would have to be debate and the inconvenient fact that there is no dangerous warming would inevitably get out.

      Lembit Opik, a real surprise package after his earlier career, keeps making the latter point and challenging GB News to set up such a debate. I am not holding my breath.

  7. Malcolm Bell permalink
    October 21, 2021 3:27 pm

    It is fascinating reading various explanations of how heat pumps work. Few if any mention the energy loss as entropy (the energy used to drive the pumps etc) and what is being done is harvesting energy at low temperature from a very large source and converting it to high(er) temperature in a smaller sink (your house). The exact opposite of refrigeration.

    Every one also assumes the main machine will be outside where its noise and bulk will only be a nuisance to the neighbours. In fact it should be indoors where the heat of the working pump (the main entropy) can be captured and also used.

    We are being taken as the credulous being led by the incredible!

  8. Stuart Brown permalink
    October 21, 2021 3:35 pm

    But. Isn’t our Great Leader proposing to move the green levy from electricity to gas? It’s about 25% of the price of electricity now, so that’s £172 that could move wholly or in part to the other side of the equation, making the heat pump cheaper to run.

    Want to bet that overall energy costs will come down? No, me neither. I suspect one ‘levelling up’ might be just adding taxes to gas until we give in. Though, if a couple of articles in the Telegraph have got it right, hydrogen ready boilers won’t be banned, might only cost £250 more than a current model, and could continue to burn pure methane in the 66% of houses hydrogen will never reach. Fingers crossed.

    • Ben Vorlich permalink
      October 21, 2021 4:33 pm

      Levies always put prices up, as with imported goods a levy only means that local producers just match the cost of the imported version with levy applied.

      Levies on gas won’t lead to cheaper electricity they’ll just put the price of energy up.

  9. David permalink
    October 21, 2021 3:46 pm

    Bearing in mind the high capital cost of heat pumps and presumably the CO2 produced in their manufacture and the very high usage of mined minerals such as copper, surely it would be far better to install resistive electric heating with a far lower capital cost even with storage heaters. This could be gradually introduced over several decades, meanwhile the government could be financing enough nuclear power plants to supply the needs. The electricity so produced would be cheaper once the capital cost was covered and maybe these could one day be nuclear fusion plants instead. (Always assuming we really need to reduce our CO2 output!)

  10. October 21, 2021 4:17 pm

    An important item that has been conveniently overlooked is HP by the experts is maintenance and replacement in 10 to 15 years, costs. Look at other domestic appliances – after 5 years repair costs exceed buy new costs due to cost of parts, if you can get them, and Labour. A couple of years ago my stove would not work and needed a new circuit board the cost of the board and labour amounted to 80% of cost of a new stove.

  11. Joe Public permalink
    October 21, 2021 4:24 pm

    Hours-run also affects running costs.

    As I stated in your “The Heat Pump Con” post:

    “Heat pump advocates always seem to forget (or are ignorant of) the fact that undersized HPs bolted onto a system designed for a swift-response boiler must run for many hours longer per day (sometimes 24/7 in winter) to try to maintain comfort conditions, and so cost more to run (than natural gas). As Roger states, undersized HPs are incapable of responding rapidly.
    All the time a heat source is providing heat, the heated building is naturally losing some of that heat.
    Boiler systems are usually sized & designed to enable the boiler to be switched off overnight (say 23:30 – 06:00 depending upon occupants activities), AND, switched off during the day if all occupants are out (working!) (say 08:30 – 16:00). This saves huge amounts of energy and money for boiler users.”

    • October 21, 2021 4:52 pm

      What about servicing and maintenance costs for boiler vs hpump

      • Joe Public permalink
        October 22, 2021 10:11 am

        They will generally be similar.

      • October 22, 2021 12:14 pm

        Daikin charge £138 for an annual maintenance service on my Altherma heat pump. Parts and additional labour are chargeable but they do have inclusive packages.

  12. October 21, 2021 5:02 pm

    “Keeps house nice and warm”. Lets not forget that there hasn’t been a very cold winter in the UK since 2010.

    • Gerry, England permalink
      October 22, 2021 10:41 am

      I presume that having swallowed the global warming scam wholesale they are not expecting anymore cold winters and in fact they will be so warm the heating won’t be needed. However, the world is heading in the opposite direction as one of the problems China has is that the northern winter heating season that usually starts mid November has been under way for a couple of weeks already due to the cold. The northern hemisphere snowpack is also well above average as we head into winter.

  13. David Hunt permalink
    October 21, 2021 5:12 pm

    Nobody mentions that if you have a combi gas boiler then you will need to find space for a hot water storage tank or electric instantaneous water heater(s) when you replace it with a heat pump. That might be difficult in small flats which have little storage space.

    • October 21, 2021 5:35 pm

      My daughter took hers out to make the bedroom bigger when they moved!

  14. Philip Wood permalink
    October 21, 2021 5:16 pm

    A referendum regarding net zero ? Not a chance. The people wont vote the “correct” way as in the Brexit ref.

    • Phoenix44 permalink
      October 21, 2021 6:15 pm

      As discussed before, the environmental levies have to be paid even if we all switched from gas to heat pumps. Any “reduction” in the difference in running costs if you switch them to gas is therefore not just wholly artificially but also entirely temporary – when we’ve all switched to electricity the price will go up massively. By then it will get too late to switch back so this is really a giant con by government.

    • Mack permalink
      October 21, 2021 6:18 pm

      Not a problem Phil, they’ll just take a leaf out of the Democrat Party playbook and bring in Dominion voting machines. After Brexit, any future referendum will only be allowed if the result can be preordained!

  15. October 21, 2021 9:50 pm

    Back in the late 1970’s during the oil supply energy crisis it became a short term fashion to fit heating units that nowadays call themselves Micro CHP.

    The units had a gas engine and generated electricity, hot water was produced by the engine for heating and domestic use. The small generator ran in parallel with the grid, so when you needed lots of watts the grid supplied.

    These things actually worked okay as an energy efficiency idea but the idea was killed off by the politics and economics as Margaret Thatcher decided cheap energy was the way to go and shut down the coal fields and privatised everything in sight.

    SID sold everything off and electricity prices fell, it was pointless trying to be energy efficient as electricity and gas were comparatively relatively cheap.

    Now we have a net zero plan with energy prices soaring and nobody seems to know quite what to do. The gullible are handing out millions of pounds to the “snake oil” salesmen, a totally unsuitable technical solution now occupies centre stage.

    The thing that I don’t understand is if the IPCC AR6 temperature reconstruction graph is correct then we don’t and we wont need heating at all, as it will be too hot.

    In consequence of this overheating planet our gas use and carbon footprint will plummet and we don’t need to do anything to save the planet.

    There you are problem solved, where’s my Nobel prize?

    • Graeme No.3 permalink
      October 21, 2021 10:21 pm

      I haven’t followed this for some years but there are/were solid state units that did this. Generation of electricity 20% efficiency, heating 60% efficiency, mostly using natural gas.
      Supposedly sold/used in northern Europe.
      A company relocated from Australia because there was no market for their product here.

    • October 22, 2021 5:28 pm

      Margaret Thatcher closed fewer mines than any other post war government

      • Chaswarnertoo permalink
        October 23, 2021 7:49 pm

        Yep. And Liebore closed more in one term than the Tories did in total.

  16. TREVOR COLLINS permalink
    October 21, 2021 11:17 pm

    Paul greetings from New Zealand. I am what you might call an old retired person in his late eighties! Please tell me what does NET ZERO really mean? thank you from Trevor.

    • Peter Barrett permalink
      October 22, 2021 12:38 am

      Mass poverty and unnecessary death.

    • cookers52 permalink
      October 22, 2021 12:39 am

      Net zero means that Greta, Greenpeace, Friends of the Earth, extinction rebellion etc are actually controlling the government of UK.

  17. John Winward permalink
    October 22, 2021 2:24 am

    Living in the tropics, we need aircxonditioners in every room – heat pumpsd running in reverse, essentially. They need to be serviced every six months to a year, to clean out the gunk, and need to be replaced roungly every 10-15 years.

  18. M E permalink
    October 22, 2021 7:45 am

    For comparison here is Consumer New Zealand on heat pumps

    New buildings here generally have heat pumps installed because of the fancies of local government who think they are Green. solutions….The Government is terribly keen on getting rid of “Carbon” .

    Mitsubishi heat pumps are probably made in China and like most things are imports from across the World

    My newly built flat has one installed but ,as the Consumer report mentions, it causes draughts no matter where you are in the room and does not heat more than one room.

    • cookers52 permalink
      October 22, 2021 10:29 am

      You don’t need heating any more, as the IPCC AR6 hockey stick temperature graph and the climate emergency says you are far too hot.

  19. October 23, 2021 9:59 am

    The lie once more ‘low carbon’ this is simply untrue (I know that is the government’s aim but it doesn’t mean it will happen sometime) and using electricty as the basis neglects losses in generation, as I have mentioned before.

    I would like to see a scientific test to assess the actual heat output for the input. I do believe that the COP figure is optimistic for heating.
    When a refrigerator is operating the heat from the condenser is low, which is why heat pumps need to run for long periods, possibly continually in cold weather.

    In cooling mode due to the physical property of energy required to change a liquid into a gas (About 1000 times more units of energy than is required to raise the temperature of the liquid by one degree) The evaporator does this and gets cold as the high pressure liquid refrigerant is allowed to expand and boils extracting lots of heat. The reverse does not happen, at the condenser which is the heating part of a heat pump, condensing the hot gas to a liquid does not give off a comparable amount of heat as is the case with the evaporator.
    In other words I believe that refrigeration plant is far more efficient as a cooler than a heater.

    I suspect that if you use a cubic meter of gas in a modern gas domestic boiler you would get more heat than if that same cubic metre of gas is burnt in a power station to run a heat pump?

    • Stuart Brown permalink
      October 23, 2021 5:24 pm

      You may be right to be sceptical about the COP figure but, if we take Paul’s numbers, your gas power station has to be less than 33% efficient for a gas boiler to put more energy into your house per cubic metre of gas burnt. That might be about right for the efficiency of a coal or nuclear plant but gas power stations do better than that.

      Do we care though? I’d rather keep my gas boiler because it’s cheaper to buy and run, is quiet, compact and probably more reliable , but I fear we are going to be nudged harder and harder until we have no choice.

  20. john gross permalink
    October 24, 2021 9:47 am

    David, sorry to be late to the party, but I am very puzzled by one point in the article.
    As I understand it, the efficiency is the simply the ratio of heat energy out over electrical energy in. What does the state of insulation of the house have to do with this figure?

    • October 24, 2021 2:02 pm

      You’re dead right, John, that is what the efficiency is.

      However without insulation the house cools down more quickly, so you need more energy input to maintain heat at the required level. But this does not alter the COP, as the pump is also putting out more heat.

  21. john gross permalink
    October 24, 2021 9:49 am

    One more thought. Would it be possible to use the cooled air output to make a fridge or freezer more efficient?

  22. pdp1140 permalink
    October 27, 2021 6:40 pm

    As well as replacing radiators, don’t the pipes feeding them also need replacing, specially if they are microbore? That’s a whole new level of disruption and cost. Isn’t copper at a record high price at the moment?

  23. John Gross permalink
    October 27, 2021 7:41 pm

    Don’t worry about copper, they can be made of iron. Just think how elegant these cast iron radiators would be in every room, with steel pipes the thickness of scaffolding poles.

  24. David Woodcock permalink
    October 28, 2021 11:55 am

    I am no advocate to the ACC theory which the government is brainlessly using to make out we are in a “climate emergency”. We are NOT in an emergency and there is no way that Mankind can turn up or down global temperatures to order like a thermostat by altering one trace compound by a few parts per million. Trust me, I am a fellow of the RMS and have studied the science for more than 40 years. Its a complete pseudo science.
    However, the air source heat pump calculations provided above are worng. It is currently much cheeper to heat your home with an Air Source Heat Pump (ASHP) than it is by using a gas boiler.
    The calculations above are wrong because the COP calculations are from eight years ago and the technology has moved on to inverter systems which sip energy and from the refrigerant gas R410A to the new R32 refrigerant gas. This now means that COP rates can be above as 700%. Now if we take into account the worst case scenario where the outside air is close to freezing and above 90% saturated then the figure falls to about 300% at worst.
    Now if one works on the basis that 1Kw of electricity today on average is three times more expensive than 1Kw of gas, even with this additional cost of energy there are still extremely generous savings to be made. I designed my own ASHP installations and conservatively speaking I can save 40% on heating bills with air to air ASHP systems.
    If you employ Air to air ASHP equipment you can save 50% on the installation costs and rip out all your radiators. You also save more energy because you dont need a 2Hp or 3Hp water pump running to pump water around your home. Further, these systems reverse and you can cool your home with the air conditioning function.
    If one combines this equipment with solar as I have done, one can have free heating and free cooling on all sunny days of the year as the right Solar system will provide enough energy to drive the ASHP.
    Its a complete no-brainer….If you have a 4Kw solar system and employ ASHP’s (air to air) NOT air to water as the government recomends then with a COP of say 500% you will gain 5 x 4Kw in heating (20Kw) as the ASHP’s manufacture heat from the environment at a rate of 5 times.
    I say “currently much cheaper” to heat using an ASHP because the gas vs electricity prices of 3 to 1 dictate that it is. In the future if electricity prices increase out of line then the savings will be less. However, the technology is currently progressing much faster with savings than energy prices are rising.
    I wholly recommend ASHP’s over a Gas boilers on the basis of savings, no carbon monoxide poisoning risk, no explosion risk and no fire risk.

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