The Impact Of Heat Pumps On Electricity Demand
By Paul Homewood
Following on from the post about heat pumps, I thought I would have a look at their impact on electricity demand.
My analysis reckoned on a typical household consumption of 3857 KWh with a heat pump. If we assume that they will only be used for heating for six months every year, that equates to 643 KWh a month, or 21 KWh a day.
At the coldest times of year, that average will increase substantially, so we could well be looking at 30 KWh a day then, since the heat pump will have to work much harder.
Although heat pumps are designed to provide low level heat continuously, I suspect that many will turn them off at night because it is too warm to sleep. We usually have our bedroom windows open all winter at night!
If we assume then that the heat pumps are in use for 14 hours a day, that gives average hourly electricity demand of 2.1 KWh. This assumes that the heat pump runs at a constant power rating. In practice, the system would have to work harder in the early evening as temperatures drop.
There are about 24 million homes with gas and oil boilers, so a peak demand of 2.1 KW amounts to 50 GW for the country as a whole. To that we can add demand from offices, shops etc, which currently use gas and oil.
Along with demand from EVs, the UK would need well over 100 GW of capacity to meet peak demand.
This is all twenty years or more away. But if the government’s target of 600,000 heat pumps a year is met, even within the next ten years, we will be needing at least 13 GW of extra grid capacity, at a time when dispatchable power generation is being shut down.
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NOT A LOT OF PEOPLE KNOW THAT 
With your figure of 30KWh per day , that is 3 times what the average house uses .
There is no way that the local grid can cope with that extra loading , and substations and local wiring would all need upgrading .
And in the Wintertime now , the generation in not enough for demand on cold days , so even doubling generation capacity would probably not be enough , leading to a far higher amount of blackouts than we get now . And then they could not just claim the odd blackout due to whatever excuse they use now .
I should have said an [ extra } 30 KWh demand per day .
Which is why a Government Climate committee in 2016 said it would need a 400% increase in generation for electric home heating , and was therefore impossible .
But it is strange how that is all forgotten now in the insane rush for Net Zero .
selective forgetfulness, perhaps? … and y’know what that means / says about them!
Oh I’m sure they just found somebody else to say something different. We used to call it “opinion shopping” when we wanted a lawyers to tell us we could do something but it was frowned upon. Governments do it all the time.
Correct, actually a little higher than 3x
Sadly, I have concluded that we actually need some blackouts (and regrettably a few unfortunate people dying) before our idiotic politicians will be forced to take notice and after their current ruinous energy policies.
I doubt if that would have an impact. Governments do not care if millions die from crazy medical policies, and the media will compliantly cover up anything embarrassing…
If anything Paul you have significantly underestimated the figures. In particularly cold weather (below freezing all day) a typical home can use over 100kWh of gas per day. Even allowing for 90% conversion efficiency that is still likely to equate to over 90kWh of derived heat. Under such cold conditions and with defrost cycles required the COP is more likely near to 2, not 3. The average high humidity in the UK is very important in this respect as detailed here
Click to access p15-18_klein.pdf
The heat pump electrical demand is probably 50% greater than your assessment.
HPs also have a defrost cycle in cold weather to stop the fan/fins etc icing up, more load and it takes heat back from your home it put there to do it, also, as HPs are outside 24/7, they will suffer weathering, leading to premature failure of components and additional load
Yep they definitely look pug ugly outside, prone to weather effects and of course they cannot be screened off nor weather protected as this would knacker their performance.
Isn’t the dampness of the British Isles the reason why heat pumps are not a good choice here?
Yep it really does not help at all. The oft quoted COP of 3 is actually gross before deductions of energy used in operating. This is why they rate them at an outside air temperature of 7°C which is just above the likely icing up level. Defrost cycles alone at between zero and 7° can knock that COP down to 2 in high humidity and that’s before the reducing efficiency from lower temperature.
Ray: I also thought Paul’s figures were on the conservative side. I have a typical house (old but fairly well insulated) and the highest gas usage was over 12,000 HWh for a quarter (4Q 2010) – about 133 KWh per day.
Much of that extra capacity will not be required for the summer months, making electrical unit costs even higher. The cost for the building and running all that extra capacity which when it’s output averaged over a year will be low and therefore more expensive per unit generated.
Extra wind capacity also requires extra dispatchable capacity, it really is an unworkable situation.
Having to build a dual generation system is the ultimate stupidity of Net Zero unless you can tolerate power cuts.
You can’t shift everything to electricity then have power cuts.
” Extra wind capacity also requires extra dispatchable capacity, it really is an unworkable situation.”
It’s bizarre that – in 2023 – burning coal and wood in the home probably makes more sense than heat pumps powered by windmills.
Having extra windmills doesn’t require extra dispatchable capacity – just keeping what we already have and not blowing up good coal power stations. However, more reliable generation IS required if we increase electricity demand.
Yep, Micky R, it is all about going back in time as opposed to advancing.
Extra wind capacity also brings in the problem of grid stability .
https://external-content.duckduckgo.com/iu/?u=https%3A%2F%2Fi1.wp.com%2Fwatt-logic.com%2Fwp-content%2Fuploads%2F2021%2F02%2Fsynchronous-condenser-siemens.jpg%3Ffit%3D1684%252C937%26ssl%3D1&f=1&nofb=1&ipt=3938f009347a600589b658709ce2f038f53026674f9950b1ca19e84dd36fe41f&ipo=images
Along with the problem of lagging power factor from millions of electric motors on heat pumps .
Not sure if the picture will come up , but it will take many £millions of synchronous condensers to keep the grid going with extra wind and all of the heat pumps
https://www.tdworld.com/renewables/article/21163285/siemens-energy-inc-irelands-first-synchronous-condenser-system-to-stabilize-irish-grid
Not sure if the link came up , so trying this one for the work needed to try to keep the grid stable
Ray, ‘The average high humidity in the UK is very important in this respect’ – you are so correct. I’m thinking too of the “scam” of ‘Kiln dried wood only’ to be sold … her in N Scotland & probably SW Scotland too, All that stuff will DRAW moisture again in storage. Air dried ? Takes too long and will not get to target level either – and what is the energy supply for Kiln drying?
But Energy to heat the home? 10L Kero per day https://short-question.com/how-many-kw-are-in-a-litre-of-kerosene/ and as per your excellent link, “These usually work with a reversal of the normal process, temporarily delivering heat for defrosting from the heating circuit. The energy required for this process is taken into account when determining the COP and results in a reduced rating” So COP is not COP as I have been taught ? think not though. So in OUR Old book, COP is COP, and therefore efficiency of these heatpumps IS a lot worse than 3, and some plonkers go on about 4, even !! Thermodynamics .
“…dried wood…”
Stays dry. Wood dried down to 15% water content will revert but slowly – perhaps to 20% in six months – even in the open in very moist conditions, provided that it is covered on the top but not the sides.
After fifty years of cutting and using wood (most of the heat went up the chimney!) I am now in a flat without an open wood fire. I must find a substitute for the healthful glow of such fires. Our evolutionary history as fire-using mammals demands this for everyone!
with a bigger saigh, ” I must find a substitute for the healthful glow of such fires” Yes butthe enclosed stoves can do them some justice without the heat fleein’ up the lum, although Poor Santa has to proceed with diligence, or the Bairnies lose out. I’m no’ gonnae argue with you about the dry wood point – never had kiln dried and the pile never lasted so long. but w could never light any fire like they do on TV , whether camping or otherwise ! So lang mae yer lum reek, Slàinte Mhath.
One of the problems when discussing natural versus artificial is that the natural sometimes comes freighted with ancient beliefs.
The man who persuaded the RAF to build the Mosquito with wood held together by glue from milk*, was actually a Professor of Materials and not in the least bit impressed with “old-fashioned craftsmanship.” In his interesting little book called “The Science of Strong Materials or Why You Do Not fall Through the Floor” he relates how he went to pick up bamboo for a project and found it lying horizontally in special racks, taking up unnecessary space. When he enquired why, he was informed by the wood merchant that when stacked vertically all the virtue drains out of wood!
*”Casein glues.” They are are wonderful but, being made of a protein, they eventually putrefy and everything falls apart. Of course the life expectancy of any aircraft during WW2 was so short that this did not matter.
Saighdear,
“efficiency of 3 or 4”, I’ve made the point here before.
No device has an efficiency of 100% or 1, that is a physical law, but somehow CoP and effciency are being considered as the same. They are not.
From what I’ve read it is almost, if not actually, impossible to get a heat pump to boil water. That means free electricity by heat pump is impossible.
Iain, I saw this article and immediately thought of you…and your blood boiling! I agree with you, the brazen levels of complete deceit are now way out of control.
https://www.theguardian.com/technology/ng-interactive/2023/dec/23/heat-pumps-science-visualised
Some numbers to demonstrate the point about heating requirements. The amount of heat energy required to warm a home is dependent on the amount of heat it loses. For heat loss calculations various internal and external parameters/assumptions are made i.e. outside air temp of minus 1° and inside temps of 21°C for living rooms and bathrooms, kitchen at 18°C , HSL and bedrooms at 16°C. Air changes of 3 per hour for kitchen, 2 for living/dining rooms and bath rooms, and 1.5 for the rest.
The thermal transmittance of the buildings materials (known as U Value and expressed as watts per square metre per degree K) are known and act as multipliers of the inside to outside temperature differential.
To give just one example: an external unfilled cavity wall to a living room of 5m x 2.4m, with a U value of 1.9W/m2/K at -1°C outside and 21°C inside, the total heat loss will be = 5 x 2.4 x 22 x 1.9 thus approx. 500W heat loss.
However, if the temp outside is -5°C, the calculation (5×2.4x26x1.9) equates to approx. 600W heat loss. The loss has increased by 20% for just a 4°C temperature drop.
A typical 120m2 3 bed semi in the UK will have a heat loss of 10kW at -1°C rising to 12kWh at -5°C. (Even small gas combi boilers are typically 24kW heat output so no problem for them to meet requirement. )
Now add to that demand increase the fact that the performance of the heat pump will be falling away, it will be running much longer and requiring more defrost cycles and you begin to see the serious nature of the problem. Firstly it may not be able to adequately heat your home so require auxiliary heating, the heat pump operating costs will dramatically increase or more probably both.
Sorry typo alert: should read ” rising to 12kW at -5°C.”
So you come home from a few days away and house is COLD ( eg end of summer when you left …. jist tae keep the Dafties happy! ) and you want instant warm up, or maybe it’s the lambing boxie, INSTANT Heat, anyone? Nope – Heatpump heat … Hmm, I can go chop some wood, the Lambie? Soup!
Poor lambie, I couldnae do that, Have a Heart Mann! Dig out the IR Lamp or ELectric Fan heater. SO instead of Soup it’ll be Toast and some warm milk ( Coco for me! )
saighdear, have you ever thought of getting your poetry published? I am sure it would sell well ‘cos it always makes me smile and brightens my day!
On top of this heating load there will be a lot of electric water heating going on too. The average household are not inclined or even capable of regulating their energy demand on an hourly basis. This will quickly lead to a chaotic power grid.
Resist smart meters they are yet another instrument of control from Big brother. Not beyond belief that they can remotely limit or even cut off electricity if you are not “playing nicely”.
Andrew Montford points out that the oft quoted fact of cold Norway having many houses with heat pumps ignores both their cheaper electricity and the fact most houses also have supplementary heating like wood burners etc.
“The Norwegian
Statistical Board has reported that 1.2 million Norwegian homes
burn wood.6 There are 2.5 million homes in the country, of which
2 million are houses rather than flats.7 These figures strongly sug-
gest that most Norwegians who have a heat pump also have a
stove as a secondary source of heat for cold weather.
This is borne out by data for the UK. The recent Nesta survey
of heat pump users found that 70% of homes that had a heat
pump also had a secondary source of warmth, typically a wood-
burning stove.8”
Click to access Montford-Heat-Pumps.pdf
Which is all well and good but Ithink the same peole pushing heat pumps would be aghast if the majority of urban householders started burning wood every day in a cold winter.
As Andrew Montford points out the oft quoted fact about heat pumps working in Norway ignores the fact most houses also have a woodburner or similar.
The same people pushing heat pumps would be up in arms if most urban households started burning wood in winter.
“The Norwegian
Statistical Board has reported that 1.2 million Norwegian homes
burn wood.6 There are 2.5 million homes in the country, of which
2 million are houses rather than flats.7 These figures strongly sug-
gest that most Norwegians who have a heat pump also have a
stove as a secondary source of heat for cold weather.
This is borne out by data for the UK. The recent Nesta survey
of heat pump users found that 70% of homes that had a heat
pump also had a secondary source of warmth, typically a wood-
burning stove.8 This indicates that most heat pump users do not
trust them to deliver sufficient heat during a cold snap.”
Click to access Montford-Heat-Pumps.pdf
Other than along the western coastline, is Norway less humid than the UK?
Well I don’t know – but we are at a different latitude AND what exactly do you mean by along the western coastline ? Take a wide or narrow felt pen and draw the coastline …. from afar it may all look the same – BUT we do not have all those BARE ROCKS and long fjords. Often in strong winds, we have the salt content drying out on the WINDOWS -40 to 50 Miles from the west coast. and we’re likely warmer too – greater RH. IMHO – just saying.
In the absence of an option to heat with gas and oil, presumably the millions of homes for which a heat pump is both a practical and financial impossibility will have to use traditional electric heating. It would also be expected that the underwhelming and insufficient heat provided by many heat pump installations would result in their being supplemented with electric heaters.
I’ve read that half of households are unsuitable for heat pumps. Logically, then, if oil and gas is to be replaced with ordinary electric heaters in these homes, it would probably be the case that the necessary power for heating at peak times would be greatly in excess of your 100GW long term estimate – probably more than double.
Undoubtedly!
Paul
This is an interesting topic. Have you ever come across a graphic that shows power consumption against outside temperatures and humidity and required indoor temperature? That would then enable us to work out real world costs in our own circumstances.
Here on the south coast we often have around 100% humidity especially during winter months, so bearing in mind the comments here that would presumably impact on running costs but could also potentially cause the sort of problems mentioned by John Bowman, below.
Another point about Norway is that It’s electrical generation is hydro electric so no CO2 emissions.. Hence a high proportion of electric vehicles.
Very few other countries have such a situation.
Norway has lots of EVs because they are generously subsidised (and ICE cars penalised) by the government – all paid for by selling nat gas to the ret of the world. They are the ultimate green hypocrites!!
“…hypocrites..”
I never did like them Vikings. Now I know why!
But also because Norway is very large and very underpopulated and very snowy in winter. People don’t drive the sort of typical distances we do in the UK.
As a former owner of an air/water heat pump system, I can confirm energy consumption is determined by the difference between the indoor and outdoor temperatures and also humidity.
The machine works hardest at night and greatest use of electricity is during the hours (approx) midnight to 6am.
Depending on temperature and humidity, the heat exchanger will ice up reducing heat extraction from the air – machine works harder – to a point where it will stop and go in reverse (taking heat from the central heating system) to de-ice. How frequently it does this depends on temp/humidity.
(I wasn’t warned about this and early one morning I realised the fans had stopped, so I went out to check to find water flooding out the bottom of the cabinet as the heat exchanger de-iced.)
When (if) there is a significant number of heat pumps operating, then night time off-peak will become peak time – particularly with all (?) those BEVs charging at night to take advantage of reduced rates.
Net Zero is a series of dots, nobody is capable of joining up.
“I wasn’t warned about this and early one morning…” Exactly clever sales people (backed up by bogus government sanctioned data) are conning the public and getting away with it. A near neighbour has given up trying to sue his ASHP supplier for mis representation as everything they claimed had government data to back up their (false) claims. He has now had it ripped out and swapped over to an LPG fired combi boiler!
“nobody is capable of joining up”
Prof Dieter Helm, Oxford Uni puts it this way
“a dense mass of overlapping aspirations, strategies and targets over more than 10,000 pages of reports, consultations and white papers. It is now beyond any minister or civil servant to name them all, let alone understand how they interact with each other, and the resulting complexity is the prime route to enabling lobbying by vested interests and the consequent capture of each of the technology-specific interventions. The Treasury and the CCC estimates for the cost of net zero assume all the policies are efficiently implemented, an assumption for which there is no supporting evidence”
https://dieterhelm.co.uk/publications/net-zero-electricity-the-uk-2035-target/
Current UK per kWh costs are 7p for gas and 27p for electricity (both inclusive of VAT). So installing a heat pump will cost you 4 times as much to heat your home to a lower level than currently. No wonder everyone is scrambling to install heat pumps 🙂
Plenty of people are capable of joining the dots, but not our idiotic and scientifically illiterate politicians – who seem to make themselves wilfully unaware of the problems with heat pumps, EVs and their huge impact on electricity requirements. They just blindly follow the green religion without engaging their brains at all.
Way back in about 1978 I was working in a test facility which had a lot of equipment producing a lot of heat. There was also a lot of airconditioning to ensure the temperature didn’t get unacceptably hot (for both machines and people).
The main cause of the AirCon to go offline or to be less efficient was the units icing up.
I’ve often wondered home domestic heat pumps avoid the problem, it seems they don’t.
‘At the coldest times of year, that average will increase substantially, so we could well be looking at 30 KWh a day then, since the heat pump will have to work much harder.’
“The machine works hardest at night and greatest use of electricity is during the hours (approx) midnight to 6am.”
So heat pumps have variable output and can work ‘harder?’
Gamecock thought they were on or off, running til thermostat setting was achieved. Maybe his age is showing, and new systems have variable output.
An installer I spoke to here in Cumbria said he was fitting hybrid (electric / gas backup ) systems here due to the icing up in cold weather and lack of output. The high humidity here is a problem too.
You have windows open in Winter! My Mrs would chuck me outside before that happened!
Hmmm….sounds like a market for a dual duvet. Tog 4.5 for you and Tog 25 for your Mrs.
Seriously though, you can get electronic thermostatic radiator valves that you can programme with different temperatures at different times. I can’t sleep in a hot room so have it set low for evening but then a boost of warmth first thing in the morning. You don’t need a Hive or Nest system with these.
“ target of 600,000 heat pumps a year …”
That is about 1/3 of the yearly sales of autos in the UK. I will therefore
guess manufacturers could produce this if demand is there.
However, unlike buying a car and driving it home, the Heat Pump
purchase is just the first step in having a functioning unit.
Of the many, here is one: The outside sort have to sit on something.
My dealer offered a 5 cm thick slab of something — I think it was
rigid foam sprayed with a concoction that looked like concrete.
I had two issues: I worried about vibrations and freeze/thaw causing
shifting. I also had male dogs — they insist on raising a leg an peeing
on anything that allows them to do so. Usually, the urine is slightly
acidic.
One can find photos on the web of everything getting the treatment
except Heat Pumps.
Still, I built forms and put mine on a concrete base that anchored
the stand below the frost line and above the dog-pee line.
Hah, I laugh at your so called figures Meester Eenglish and only heating for 6 months a year and sleeping with your windows open in winter. Try that up in Aberdeen. MERRY XMAS.
Not just in Scotland. Here in Cheshire we have heating on most of the year, except for the rare couple of days’ heat wave and never sleep with windows open.
If we are to go truly electric we require heat pumps, electric ovens with electric hobs, electric heating for hot water, electric lighting, electric for current domestic equipment such as dishwashers and washing machines and increasingly power tools such as electric lawnmowers.
Add in Electric vehicles and the figure I have seen is a requirement of three times the current production, around 150GW plus storage of course.
In the 2016 analysis by the Government climate committee , [ which is now difficult to find ], on about page 65 it concludes that it would need an EXTRA 200 GWh of generation to cope with future demands , which is why they said that Electric home heating was impossible .
All this talk, even on here, Good points & nonsense, Heatpumps are the new name for Heat exchangers. Gramps had a big one years ago: In the dairy, too COOL the milk and later again after pasteurising it for bottling for the local market. The milk could be so cold on the tubes that you could scrape off icecream, unsweetened, and the HEAT used for the wash water at the time. – before we “thought ” of heat pumps. Then came the EU + more red tape. Some old names Gascoigne, Fullwood & DELAVAL eg https://www.delaval.com/en-gb/discover-our-farm-solutions/milk-cooling/ and to broaden the mind https://www.youtube.com/watch?v=I6QFjdW32qE Enjoy.
And this is why the government had to give in on offshore wind CfDs. Ministers might not know the exact figures but they know they needd an awful lot of new generation and that they have only one place to get it from. Investors are quite capable of doing these sums and understand what they mean. But the higher electricity prices go, the fewer people will buy an EV or a heat pump. Net Zero only works if prices are low and falling, not high and rising and there’s a limit to what costs can be imposed on gas and ICE users.
And the story of battery public transport failures continues with the buses in Minnesota failing to work in the cold weather. Range was half what was expected and the company that made the buses Proterra went bankrupt in August. Another vanity project made possible by taxpayers cash.
Meanwhile, the strategic stores of gas in Europe are still 87% full, with January forecast to be warm. The price of gas has fallen on the Dutch exchanges from 48 EUR/Mwh, a month ago, to 34 EUR/Mwh. It is all good. Cue for our politicians to “spend the good news” and mess everything up again.
This analysis would be better it if used real figures. Instead of trying to estimate what a heat pump might use, why not get some real data that people report ?
Also, the other side says that the COP is getting better all the time. They say 2016 was the stone age for heat pumps, with a COP of about 2.5. The latest models are said to get average COP of 4.5.
Having said that, it is clear that electricity demand can only increase due to gas being replaced. It is not at all clear how demand can be met during extended low-wind periods in winter.
The Greenmatch and Energy Trust factsheets are fully upto date, and reflect latest technology.
Forget about COPs of 4.5 – there is no evidence whatsoever that these can be achieved – it is just manufacturer spin.
They can be achieved when the ambient temperature is 25-30C, though usually you want to operate them in reverse at those temperatures, . But not 25-30F!
It doesn’t add up…
Surely that plot applies to air conditioning not heating ?
Why would you heat a building that is already at 32 degrees ?
Of course the plot applies to aircon, which is what I noted you would be more likely to be requiring at temperatures of 25-30C and higher. The point of showing it is to demonstrate that aircon is less efficient at higher outdoor temperatures, and that although your heat pump might be more efficient when used to provide warm water at such temperatures, you lose efficiency when switching to aircon – and that aircon loses efficiency if you aim for a lower indoor temperature.
I do wonder whether claims about heat pump COP averages don’t simply take an arithmetic average including at high ambient temperatures where you wouldn’t actually use them. All part of the propaganda.
“Surely that plot applies to air conditioning not heating ?
Why would you heat a building that is already at 32 degrees ?”
Who programmed you?
From your point of view, it is not relevant who programmed me.
You still have to address the points raised.
Otherwise everyone can simply dismiss the other side as a bot and refuse to answer the arguments. It’s the end of debate.
Since you are obviously a mass debater, you need to respond to the arguments with reasoned debate. Otherwise you might as well close down sites like this.
Over all conclusion, Heat Pumps, Battery Cars, Net Zero are NOT GOING TO WORK.
As our Government will not U-turn on this one, we just have to wait for the power to run out and inevitably deaths, although bad weather will be cited as the cause and we need more wind farms to prevent it happening again.
In a new build house, it would presumably make sense to have a large mass of concrete being heated at a low rate all year around to provide the base heat supply that can be topped up when needed. Ofcourse the majority of UK housing stock is old and draughty and unsuited for heat pumps.
But But…think of the carbon footprint of all that concrete !!!
The impact will be less than you think… OFGEM implemented a reduction in the size of that infamous unit, the Home, from 2,900kWh of electricity and 12,000kWh of gas to 2,700kWh and 11,500kWh respectively, effective 1st October. So your utility bills will fall even if they don’t really change, and your house will be just as warm – won’t it? Never mind – all windmills have become instantaneously more productive!
A not so funny tale of solar PV:
https://www.msn.com/en-gb/news/uknews/solar-panel-firm-with-greta-thunberg-ad-sued-over-1-5m-house-fire/ar-AA1lWQ2W
A very similar fire happened to friends just when they had installed a new PV system. It took them many years of legal wrangling to get insurance payout. Costs included alternative housing as well as the demolition and rebuilding of their former home.
Last Sunday night Our local substation cable burnt out ..Why ?
There’s quite a few low powered Christmas lights on
but I wonder if it was a prime time for Electric Car charging.
that’s a heavy load ..than might have well caused an old cable to conk out
Robin Hawkes has an interesting visualisation of EV charging in his annual review. Scroll down to find it (and several other interesting developments he has been working on)
https://robinhawkes.com/blog/2023-retrospective/
Seem little doubt to me that UK, just like here in Australia, is heading down a one way street to disaster with it’s renewables energy policies and net zero target etc.