Why Heat Pumps Will Raise Your Energy Bills
By Paul Homewood
Following on my post on Northern Powerhomes, it is time to nail the lie that heat pumps are cheaper to run than gas boilers.
A typical detached house with gas central heating would use about 11,000 KWh for heat, and a further 4000 KWh for hot water, according to the Greenmatch website. This is consistent with what I use.
Based on the prices I pay, below, my gas bill should be £370pa. plus £68pa for standing charge. (Currently we have a gas hob, so would still need a gas supply)
According to the Committee on Climate Change’s Sixth Carbon Budget, the average efficiency of air source heat pumps is 300%. (Ground source are slightly more efficient, but are much more costly to install):
An efficiency rating of 300% means that you get 3 KWh of heat for every 1 KWh of electricity input. (See here). The CCC assume by the way that houses are well insulated, as the efficiency rating will be much less otherwise).
Gas boilers are assumed to run at 87% efficiency, so 11,000 KWh of gas produces 9570 KWh of heat. At 300% efficiency, we would therefore need 3190 KWh of electricity.
As electricity costs me 14.49p per KWh, the annual cost would be £462, compared to my gas bill of £271 (excl hot water).
That still leaves the thorny question of hot water. Heat pumps cannot normally raise water temperatures to the level of 60C required to kill legionnaires bacteria. The easiest solution is to install a separate electric water heater, but this would obviously cost more to run than gas.
Alternatively, there are ways to top up the heat provided by a heat pump, known as “hybrid heat pumps”, which would add to the cost of installation. If the hybrid is powered by electricity, we again hit extra running costs. The CCC’s preferred option is to use hydrogen once gas is phased out, but this too is considerably more expensive than natural gas.
Either way, we can expect to see our energy bills rising by at least £300 pa, if heat pumps are installed.
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NOT A LOT OF PEOPLE KNOW THAT 
Another reminder of the fantasy world inhabited by the CCC. The figure they use for the seasonal COP of an air-source heat pump is unrealistic. The COP depends on the difference between the condensing and evaporating temperatures at which the device is operating. It has nothing to do with the level of insulation of the dwelling. Their figure of 3.0 is based on an unrealistic water flow temperature of 40C. Try setting the flow temperature of your gas-fired boiler to 40C – it will be always operating deep into the condensing regime and at an efficiency closer to 95%. Your house will also be rather cold.
Heres what Mitsubishi say about their ‘advanced’ heta pump output
The maximum power is only required when going from cold to normal room operating temperature , once you are stabilised you may only need 1/3 to 1/5 of the maximum power. Thats output power too , so actual usage is the roughly 30% ratio of that.
” … maximum power is only required when going from cold to normal room operating temperature …”
And for recovering temperature after say doors to colder spaces opened.
Those statements apply no matter what the heat source is.
However, ‘undersized’ heat pumps/systems have to run for far longer than say a rapid-recovery gas boiler, in order to raise the comfort temperature in a room. During that extended warm-up period, heat is being lost continuously.
You can ‘heat’ a bucket of water with a candle, but it could take forever.
The efficiency will depend on the ambient temperature, below 4C they go off rather quickly, they also tend to freeze up as the exhaust air is now below freezing, often resistance heating is used on the OUTSIDE unit to prevent this, waste of heat. My daughter in the US had one for cooling and heating (summer or winter) the internal units were air, cold or hot, but they had resistive heating as well, the winter bills were astronomic almost totally rather inefficient resistive heating, you might as well have a 3 bar electric fire in each room. My gas boiler is 31KW combi, it costs me about £2.50 per day at the moment (Not above 2C all day) to heat house and hot water. On my own but with covid in all day every day. Poor insulation, big house as well. Newcastle council installed some air ones last year for free, I will try and follow up how they are performing now, they were on the local news with the owners very positive, lets see if they are still happy.
Geoff, it will certainly be interesting to hear about the experiences of the council installed units. Our local Facebook often has adverts promoting heat pumps/hybrids and there is not much positive feedback about heat pumps in general. There was one person the other day praising his ASHP claiming it keeps the house at 19 deg C and IF any extra heating is needed they have secondary electric heaters. To me that says they are useless.
Even more interesting if you can find out the cost of the unit, if they had bought it for themselves, and the cost and extent of the insulation.
Pullovers and pneumonia for the poor living in swathes of Britain’s poorly insulated housing stock.
At last ! – back to the good old days of …
candle lit suppers (no electric), frost on the inside of windows & walking to the shops that are full of … empty shelves; can we have ration cards as well ?
Geoff: “… they had resistive heating as well, the winter bills were astronomic almost totally rather inefficient resistive heating”
I have had heat pumps in my homes and agree that those electric heat-strips are essential when the outside air is very cold. That jacks up the monthly bill. I have no way to compare with gas however. We use gas for cooking and it is better than electric simply because when the gas is off, the heat is off and when the gas is on the heat is on…no waiting for a burner to warm up.
A bit OT, but I stumbled across this rubbish from the Met Office. Apologies if it has already been posted on this site.
Not sure whether the conditions he was forecasting would occur despite all the expensive green energy ‘initiatives’ that are going to impoverish us all.
My detached, 3-bed, 1750 sq ft house has an average annual gas charge of 15,423 kWh @ £638 for heating and hot water (with a 10 year-old boiler). Electric is 3772 kWh @ £716.
I guess that two of us being retired and, this year, cooped up, the usage is higher.
Still trying to figure that out with the info above…
Ours is very similar, Harry, though we also have a gas hob
The 15000 kwh is estimated to be 11000 for heat and 4000 kwh for hot water
Looks like shall have to tell BG I want to switch. 🙂
I’m with Avro
4000kWh for hot water ?
My place for 2 people – but not in Britain- with 2 heat pumps uses around 4500kWh per year for ALL the electricity useage.
Hot water, cooking, lights , dishwashers,appliances etc The 2nd smaller heatpump is being used now in summer upstairs overnight, as its a humid climate but say 25C max average in summer The larger unit downstairs is is set at at 20 to 21C for winter evenings plus some mornings.
Thats a lot of hot water , or average of 12 KWh per day. I have a system of having the hotwater electric cylinder on for around 1 hr only – a bit more in winter and bit less in sumer and as its a 3Kw rated element thats 3kWh per day….no I dont run out of hot water but dishwasher and washing machine heat their own , only as needed.
I honestly don’t know! That is the figures advised.
Of course, if 4000 KWh is too high, then the figure for heat must be higher, making the cost comparisons even worse
That’s a lot for what you are actually using,,,what is your cost for each unit in £/kWh and standing charge, I’m with AVRO fixed price till August this year, i’ve been with them for 18 months. standing charge is 15p/day each for G & E. G= 2.235p/kWh E= 12.2p/kWh. Their estimate for this year is G 17,590 kWh cost £470 ; E 2729 kWh cost £407. the year costs have 5% VAT the tariffs do not. Im paying £71 per month. Gas is heating hot water and hob.
Geoff, my standing charge £7.63 for gas, £7.08 for electricity for last month (31 days).
Gas is 3.92 p per kwh (SC=24.6 p per day)
Elec is 16.09 p per kWh (SC=22.8 p per day)
British Gas.
I wonder what your price will be like after August…
What’s your heating?
I’m Avro too, Geoff
I’m with AVRO too. Very similar figures.
AVRO…think I’m getting the message… 🙂
I don’t know when your energy contract’s due for renewal, Paul, but mine’s due very soon and the very best I can do is to limit the increase in bills to just over 20%. some quotes would have me paying 30% more.
If that isn’t bad enough:
https://uk.finance.yahoo.com/news/coronavirus-energy-household-bills-price-rise-ofgem-115901588.html
Interesting analysis , therefore gas unit prices only have increase by 70% or so to make heat pumps appear cost effective , don’t tell the GREENS, or is this already baked into energy policy.
Correction to the above I should have written {standing charges and unit rates} rather than {unit prices} to avoid confusion.
We have a hybrid, air source heat pump. Between 5th February 2020 and 31st January 2021, I used 18,214 kwh. Gas hob for cooking using bottled gas. The cost per kwh with my current electricity company is 13.111p inc VAT with standing charge of 20p per day. So electricity cost for about a year was £2462. And that is with solar panels. It is a fairly large bungalow with 5 bedrooms, built in 2011, 360 sq m.
Agh! that’s £200 a month, grief that’s very expensive or your house is very hot and you keep the windows open!.
Wow if they are 300% efficient then you had 54,642 kWh of heat. I smell a rat here,,,,,,,,,,maybe they are less than 300% efficient somewhat nearer to 100% me thinks.
P.S I looked at the Newcastle scheme no recent news…will keep an eye out.
They clearly have the unit running day and night 365 days a year- some do as its ‘too much trouble’ to use time or adjust down when out.
Of course other appliances like dishwashers, washing machines, even TVs can be large users of power these days
Geof,
heat pumps have interested me for some time and the idea that you get a lot more out than you put in has never rung true to me. I am familiar with and have worked around refrigeration plant during my maintenance jobs for a long time.
The first point is that the fuel to produce the electricity loses about half of it’s energy in making and transmitting the power to the consumer, i.e roughly 50% less effective than direct heating with a gas boiler.
The principle of a refrigeration device is that it’s refrigerant boils (Which boils at a very low temperature well below the freezing point of water) just before the evaporator by opening a valve to release the high pressure obtained from the compressor. This boiling produces a very low temperature at the evaporator. From my physics of decades ago, change of state requires in the order of about 900 times that which is required to raise a unit weight of liquid one unit temperature. That, I think is the theory.
We then come to all the mechanical and tempertaure transmission losses. Reed valve compressors used in refrigerant plant are not very efficient .(Which is why internal combustion engines control the intake and exhaust valves to improve volumetric effciency.) Then there is the effciency of the two heat exchangers, the condenser which is warm and the evaporator which is cold. Air heat exchangers in particular get dirty very quickly and reduce the plant’s effectiveness and hence efficiency.
Another factor is that the temperature difference affects the rate of heat transfer. In cooling mode there is a much greater temperature difference at the cooling coil (Evaporator) than the condensing coil.
When reversed the temperature difference at the now heating coil (condenser) is much less and to me this means the COP of the same plant i is higher when cooling than heating, in other words they are better at cooling than heating.
I really would love to seem some real figures from a controlled test that actually measures the heat output compared to a gas boiler,?
My feeling would be that the figures quoted are far higher than the actual performance?
I am puzzled by the concept that something can be 300% efficient, or even 100%.
Paul, you seem to have forgotten the effect on Heat Pump running costs of those wonderful gadgets the govt & electricity suppliers are so keen to get everyone to adopt: “Smart Meters”
Space heating electricity demand can’t easily or cheaply be time-shifted, and by strange coincidence heating is most needed when it’s cold, dark, solar generates nowt and electricity prices are highest.
The net result is that those very Smart Meters will, via Time-of-Use tariffs, make electricity ‘cheap’ when no one wants it, and very, very expensive at the times Heat Pumps most demand it.
Annual heat pump running costs will not simply be a factor of electricity quantity x average electricity price, but will be weighted vs the quantities required at the various higher prices.
Reminder: Nat gas tariff prices are ‘Economy 24/365’, and in reality 1/4 (per useful kWh) the current electricity average price.
If you want the house warm when you get up, you’ll have get up before you go to bed!!
I currently live in a new 4 bed house, with 3 adults. I am off the gas grid so electricity is my only realistic option. My air source heat pump is costing a similar amount to my previous similar sized modern house which had gas and electric. We can agree that heat pumps are efficient so the real issue has to be the grossly over inflated, ROC and CFD weighted electricity price.
yes. Thats the real issue not strange ideas about heat pumps efficiency and usage. I dont think they should replace gas ‘just for the sake of it’ but its a funny world
What will happen to us very rural folk who are not on the gas grid and use oil for heating? We are also on the end of a 11kV (I think it is 11kV but it may be 3.3kV) power line which I doubt has much spare capacity. Fortunately everybody has log-burners to provide extra heat and many of us have our own generators.
Phillip:
When the world goes mad the sane are persecuted.
You need to have a “Green” option, and since every bureaucrat ‘knows’ wood doesn’t emit ‘carbon’ then burning wood for heat would let you claim to be Net Neutral (whatever that means).
Unfortunately I don’t think you would be able to claim a subsidy unless you live in Northern Ireland. Fortunately being ‘very rural’ the chances of any pen pusher calling in cold weather when you are burning wood are minimal.
Gosh, I never realised mains gas was so cheap. Unfortunately we are rural (no mains gas) so changed to an ASHP back in 2009 because I thought oil prices would continue to rise stratospherically (got that wrong didn’t I!). We use about 13,000 kWh of leccy for heating + cooking/lighting. So that costs us about £1,900/yr. We have RHI at the moment of about £600/yr so a net cost of £1,300/yr. Our house is reasonably well insulated but we still use a wood burner for additional heat on winter evenings. I pity those people living in old and poorly insulated properties who are made to change by councils/housing associations etc to ASHP and who will be paying vast sums to try and keep warm. Used in the right housing type and operated in the right way the ASHP is (I think) an OK means of heating but it certainly is no panacea.
I have a heat pump. Heating my all electric house is probably slightly more expensive than heating with natural gas, even in just the downstairs fire place. My problem is natural gas was not installed and the line is across the street. Paying to dig up the street to run a 0.75″ NG line offsets any savings for a long time.
There is a classic fallacy in the cost argument for heat pumps that hides behind the term “average”. The well known problem being that the colder it gets, the less efficient a heat pump operates at. When you are getting a coefficient of performance (CoP) of 3 to 1 from an ASHP it is usually a mild period and you do not require much heating. When you do require more heating it is obviously because it is colder and the CoP has significantly dropped making it dramatically more expensive..
To make a simple analogy if a new graduate takes up a job at £30,000 per annum, allowing for thresholds on Student loan repayment, NICs, Income Tax and say 6% pension contributions, the total deductions would by about £7500. You could argue that total deductions are at 25% of gross income but of course every additional £ above that £30,000 will initially incur 45% deductions and ultimately much higher as other thresholds are breached.
This false use of averages also relates to any transfer from fossil fuel use to electric use such as from petrol cars to Battery EVs. The marginal additional generation required to meet the extra electricity supply will currently always come from additional fossil fuelled, dispatchable generation. Accounting for the BEVs emissions as the Grid’s “average” emissions is clearly false accounting.
Good analogy, Ray. Unfortunately, there are few mathematicians in the house and seemingly few scientists. But there are plenty of lawyers.
Harry, a little tip if you are considering switching your energy supplier. All suppliers are continuously varying their term offers on a monthly or even more frequent basis. For a company like Avro the best time of year to switch to them is just at the end of the central heating season when your gas use will drop to very low indeed and your electricity will be slightly lower than the annualised average. They will take the first payment even before your switch to them goes through. As your monthly payments will be based on annual use costs you will immediately start building up a significant credit on your account. Therefore they have your money in advance of their paying their bills and effectively negligible credit risk. You become the very type of business they want to attract and will offer you the best terms. If you switch in say September you will likely go quickly into debit and be more of a cost (and therefore risk) to them so the tariff offer will not be so good.
My current Avro rates (switched last May) are actually quite a bit lower than Paul’ has quoted to the extent that at a fraction over 2p per kWh my gas is actually a sixth of the electricity rates.
The idea that extra generation required is only marginal is just fantasy.
In 2016 a government committee decide that it would be impossible for all housing to go electric heating as that would require an extra 400% of generation capacity .
And that is without the push for electric vehicles , which would also need a lot more .
And then there is the factor of local distribution .The average house uses about 10 KWh per day .So most sub main systems are built with with an average capability of 5 KW supply to each house , because they do not have all of their electric appliances turned on at the same time .
So any wide scale take up of electric heating & EVs would need a massive increase in generation capacity & mostly a complete replacement of all Substations & local sub main distribution systems .
Interesting article. However, there is no mention on the safety of a heat pump compared to a gas fired heating unit: the latter in fact can start a fire: fortunately such cases appear to be relatively small in the UK: https://www.morganclark.co.uk/about-us/blog/uk-house-fire-statistics/). Additionally, gas fired units can also result in CO poisoning.
There is no mention either of oil fired units which may cost to use over four times more than a gas unit, being more costly to maintain as well. I used to have a heat pump with oil fired backup heater; then I replaced the oil fired back up with electric back up resulting in savings of 10 to 20%….
50’s 3 bed semi. 1 occupant.
Gas heating. cooking, hot water, 7979 KWh DD £20.30 per month.
Electricity 929KWh DD £20 per month.
Was appointed Energy Manager in the 80s for a small company in addition to my day job and so tend to be frugal.
Correction, Typo, gas 7070 KWh.
I would be prepared to pay up to £1200 for an installed heat pump if the running cost was £10 per month for 7000 KWh !
Paul: your figure of £300 per year is nonsense. You have not factored tin he cost (intererst) on the money needed to make these changes.
Yes, I stressed that these are just the extra running costs (not savings!!), on top of all of the extra capital costs
Seriously off topic but seriously worrying:-
https://www.telegraph.co.uk/news/2021/02/03/france-found-guilty-failing-honour-climate-commitments-landmark/
No, it’s all good. Sooner or later the elastic will snap. This kind of thing brings that moment closer.
I hope.
Irrespective of the cost/climate benefits, or otherwise, of imposing heat pumps on the nation, has the UK government actually considered where the majority of the revenue from spending billions on heat pumps will actually go? A quick perusal of the top ten suppliers of heat pumps in the UK reveals that, irrespective of UK flagged front companies, the manufacturing base lies almost exclusively off shore. China, Korea and Japan dominate with Sweden, Germany and, even Ireland, holding up the rear. And, as with wind farms and solar panels, actual wholly owned British companies will be picking up the crumbs whilst the big fat crusts of the income generated will be chomped overseas. And, again, as with most other supposedly ‘green’ projects, the Co2 generated in the manufacturing process will also be off shored to salve our carbon sins but won’t make an iota’s difference to the climate.
We use an air to water heat pump to run underfloor heating and hot water. Our total power use is about 7500KWh/annum in a 273sqM new build home. Not a heating system you can retrofit! It works very well. We are in S Island NZ so climate a little warmer in summer than UK. Very happy with the system in a country which often manages home heating with a couple of extra woolies!
I doubt whether you have access to on line natural gas at 2.5p per kwh.
Heat pumps certainly are more economical than electrical resistance heating, though whther it justifies spending £15000 to install is another matter
Here in the UK, most homes are on the gas grid, so heat pumps will work out far more expensive
Yes, we have no reticulated gas in most of NZ! LPG comes in 45kg bottles which we use for cooking and a gas fire. Our installation costs in a new build were $18000 – about 9K sterling – less than the 15K you quote. Of course, NZ uses a lot of heat pumps and the infrastructure to support their purchase, installation and use – and most are used to generate warm air inside homes.
£9k is probably right for a new build.
But in old houses, the radiators will need changing and extra insulation fitting.
Hi Paul,
The Heat Pump folk claim, “An efficiency rating of 300% means that you get 3 KWh of heat for every 1 KWh of electricity input.”
Wow,,, I think Mr Einstein may have something to say about that!
Regards,
Brook Acklom Castlemaine VIC Australia
Brook Acklom,
It is implied that you can get UP 3 kwh of heat for every kwh of electricity used to run the heat pump. As far as I know, Dr. Einstein would say yes indeed….
A bit of OCD recording of the heat pump experience :
https://trystanlea.org.uk/heatpump2020
I don’t have access to gas and in Wales all new houses are to be built without a gas supply. Mark Drakeford is extolling the virtues of heat pumps. I checked out ground source:
https://www.homebuilding.co.uk/ground-source-heat-pumps-need-know/
“You will need a fairly large garden — allow 500m² for a 10kW heat pump in clay soil, and twice that for sandy soil. A vertical array, often called a borehole system, will have boreholes drilled into the ground and connected across their tops, in a closed loop. The number and depth of boreholes will be dictated by the size of the heat pump and the geology.
For instance, an 8kW heat pump is likely to need at least three boreholes 70m to 100m deep (or two slightly deeper boreholes).”
The cost of installing a typical ground source heat pump system in a three to four bedroom house will be over £10,000, according to the The Energy Saving Trust.
And it still needs 1KW of electricity for every 4 KW of heat and a massive tank in the house requiring a separate room. In contrast a gas boiler will use about 180 watts maximum and sits on a wall. The poor are paying for the indulgences of those who can afford to take advantage of the RHI: As of 1 April 2019, the RHI rate for domestic ground source heat pumps is 20.87p/kWh.
“In the scenario above, we need 11,000 + 4,000kWh of heat, less the 3,334kWh of electricity used, so RHI applies to: 11,666kWh at 20.87p/kWh = £2,435 per year for seven years.”
PIONEER ARE OFFERING TO INSTALL A £10.000 AIR HEAT PUMP FOR FREE ,UNDER A GOVERNMENT SCHEME WHAT IS THE CATCH
It’s paid for by govt subsidies
It’s nice (after all these years of reading this website) to be able to comment on something which is my working life. I am a heating engineer (and consultant). Fourteen years ago, I converted my gas-heated home to electric – at daytime rate – underfloor heating. I did all the maths and, although it worked out more than gas, that’s not the whole story. I have no flue, no fumes, no servicing, no maintenance, no breakdowns, and no insurance to pay. I have individual room time & temperature control (which we use to great effect). My home is a 3-bed detached bungalow with 10 rooms. We use 16,500 kWhs which costs us £1,500 a year – for all heating requirements. Hot water costs us around £300, and cooking & lighting £200.
I would NEVER go back to gas central heating with radiators!
I did look at heat pumps a while back, but the investment and maintenance & breakdown costs rule it out completely. Rather than looking at heat pumps, I would urge anyone to do the maths for going electric, instead. You MUST add on the cost of servicing and repairs, which can be very costly as engineers are (and will be) charging a premium.
For comparable reasons above, the cost of using solar panels to ‘pay for’ costs are equally without merit. The investment made is never returned. I recently got into a conversation with someone on YouTube who said that he had a BA in mathematics at Oxford, and that I was wrong. I asked him to show me his data…he refused.
Just do your own maths – including EVERYTHING: capital expenditure, loss of interest on capital, servicing, maintenance, and depreciation (a gas boiler will depreciate by around £200 a year! – that means £200 added to your costs)…and like me I’m sure you’ll find it’s simpler and cheaper to simply plug in a heater!
Good day cockneygit,
You present actual data from your own experience. However, I do have some observations:
– how much more have you paid since you switched to all electric, from gas?
– have you looked at the new high efficiency heat pumps recently? I would think that they may have an overall cop of 2, or higher (halving, or better, the electricity consumption).
– I am not sure what do you mean by underfloor electric heat: does it have a metal grid on top (and flush with the flooring) to allow for natural air convection into the room? In that case, such units may represent an inherent burn hazard for any one stepping bare footed, or even worse falling, on them.