Dr. Lars Schernikau: Energy Economist, Commodity Trader, Author (recent book “The Unpopular Truth… about Electricity and the Future of Energy”)
Details inc the full Blog are available at www.unpopular-truth.com
Heat pumps are having a moment. Governments promote them, utilities love them, and they are, now more often than ever, described as an obvious replacement for fossil fuels (oil, coal, gas), fueled heating. The basic idea sounds great…a heat pump works like a reverse refrigerator. Instead of “pushing heat out, it pulls heat in”. That heat can come from the air outside your house or from the ground below it.
The International Energy Agency (IEA) sums up the enthusiasm nicely. “Heat pumps, powered by low‐emissions electricity, are the central technology in the global transition to secure and sustainable heating. Heat pumps currently available on the market are three‐to‐five times more energy efficient than natural gas boilers. That statement contains three big claims:
(1) heat pumps are three to five times more efficient,
(2) they run on “low-emission” electricity, and
(3) they are secure and sustainable
All three deserve a closer look, so here we go…
1. Why heat pumps really are efficient… at the device level
There is a solid reason, rooted in physics, behind why heat pumps are attractive. Transferring heat from one place to another takes much less energy than generating heat from scratch by burning fuel. Under favorable conditions, a heat pump might use one unit of electricity to move three units of heat. This is where the famous “three to five times more efficiency” number comes from.
But here is the catch! That number is not efficiency in the everyday sense. It’s called the Coefficient of Performance (COP), and COP is not the same thing as system efficiency. To start with, a heat pump relies on electricity, while a gas or oil boiler mostly relies on chemical energy and needs very little electricity to operate. You can keep a boiler running with a small backup battery… but you cannot do that with a heat pump… the three to one number forgets the (in)efficiency of the electricity required from the grid… and you and I know how complex that grid is.
2.Electricity doesn’t just “arrive” for free
The “three to five times more efficiency” claim, quietly assumes that electricity arrives at your home with no losses. But in reality, electricity available 24/7/365 has to be generated, transmitted, balanced, and backed up.
On average, roughly 2.5 to 3 units of primary energy are needed to deliver one unit of electricity to your socket when thermal power plants are involved, as they mostly are.
That means using electricity “100% efficiently” at home starts, at the system level, at only 30 to 40% efficiency. Wind and solar changes the accounting by introducing their own challenges, among them being the need for overbuild, short duration storage, long duration storage, thermal backup and larger and more complex network integration and transmission infrastructure. Once these are considered, wind and solar dominant systems do not outperform coal, gas, or nuclear in net energy efficiency but actually underperform. Think about energy density, intermittency, and the short operational lifetime.
3.Heat pumps struggle when you need them most
Another unpopular truth that raises the temperature… or does it?…
The colder it gets, the more the performance of heat pumps decline.
When winter hits and heating demand peaks, the heat pump performance COP drops. This is especially true for air-source heat pumps as ground-source systems tend to perform a bit better, even though they are more expensive, slow to install, and often impractical in densely populated cities.
This creates a nasty feedback loop… because just as heat pumps need more electricity during cold spells, solar output tends to be low, wind can be unreliable, and grids are already under pressure on top of the dropping COP. In winters coal and gas plants are usually ramped up to secure the electricity supply. So even if your annual electricity mix looks “green,” the marginal power that keeps your heat pump running during a cold snap is more often than not fossil-based… do you see the feedback loop?
4.Peak power is the real bottleneck
Electrifying heating doesn’t just increase electricity consumption, it increases peak power demand in winters when power system are already strained. Grids must be built for the coldest, darkest, calmest winter evenings, not for yearly averages. The IEA projects that peak electricity demand grows far faster than total electricity demand due to heat pumps, electric vehicles, data canters, and AI. When demand spikes, coal, oil, gas and nuclear fill the gap. That is why the idea of heat pumps running on wind and solar often collapses under real winter conditions.
5. Security and sustainability depend on where you live
If you are in rural Scandinavia with abundant hydropower and a very secure grid, heat pumps could make more sense, but in large cities with fragile grids, the picture changes completely. In urban areas, air-source “monoblock” heat pumps are popular because they are cost-effective and easy to install. However, they are noisier, lose efficiency in winter, and are vulnerable during power outages. When the power goes out during freezing weather, circulation stops, water freezes, pipes burst, and systems can be a complete write-off. After some recent winter blackouts (Berlin end December 2025), many heat pumps didn’t come back online even after electricity was restored.
Now imagine there is an armed conflict or cyber-attack? Do you feel safer with a heat pump or with a standard gas- or oil-based boiler?
So let’s be honest…from an energy security standpoint, heat pumps seem flaky. From a sustainability standpoint, powered by energy systems that require massive overbuilding, short lifetimes, and heavy material use it is questionable at best and deserves some skepticism and allot of discussion.
Summary – So where do heat pumps actually fit?
Heat pumps are neither a universal solution nor a dead end. They work best, out in the country, where grids are reliable, electricity is reliable, or where winter temperatures are moderate. But in a city setting, district heating combined with large ground- or water-source heat pumps and thermal storage is likely more appropriate than widespread deployment of individual units.
One last reality check we should consider is that… adoption closely follows subsidies. When subsidies drop, sales drop. That doesn’t make heat pumps bad, but it does suggest they are not the obvious, no-brainer solution they are often made out to be.
Heat pumps are efficient machines, sure, but whether they actually contribute to an efficient, secure, and sustainable energy system depends on too many elements around them. One thing is for sure, heat pumps cannot make oil and gas boilers go extinct… and anyone telling you otherwise is disingenuous.
Read the full analysis here:
https://unpopular-truth.com/2026/02/14/heat-pumps-for-all/
“Grids must be built for the coldest, darkest, calmest winter evenings, not for yearly averages.”
Exactly. Here in rural NY, we “get it” and prepare accordingly for high-risk storms and cold snaps. But Albany keeps pushing the wind + solar + batteries + heat pumps agenda. It is nuts.
RECARBONIZE NY! We are sitting on huge deposits of untapped natural gas in the Marcellus and Utica formations.
That is all for now.
It really is insane for NY to be on top of all that shale gas and not use it. There’s plenty enough to pipe it to New England where we really need it.
For people with short attention spans…including politicians
Especially politicians!!!
Heat pumps are great in certain situations. I have a pool heater that i use outside of summer (in the tropics). Because it’s generally fairly sunny, my shed where the pump is situated gets hot, like up to 30C even in winter. That allows a lot to be transferred to the pool with minimal cost.
In addition, if I had solar panels, I could use the electricity to run the heat pump. That would be a win-win.
Unfortunately, most situations just don’t have these favourable conditions. The benefits are normally much less. For example, I use gas in the most expensive way possible, using 15kg cylinders for my gas cooker. It still costs me about 1/10 of the cost of an electric cooker. That’s something serious to consider.
It is very unlikely that your solar panels would have output when you need to run the heat pump.
Of course the heat pump does work best on a warm sunny day. I really need heat in cold dark weather.
If it is being promoted by the government you can bet you’ll end up the worse off for it. It’s nothing new.
Back around 2000 or so we were told in no uncertain terms that diesel was the way to go because it produces less CO2 compared to benzene. So, many people took that advice in good faith.
2017 – In 2001, the then Chancellor Gordon Brown introduced a new system of car tax aimed at protecting the environment. In actual reality it fostered a popular move towards highly polluting diesel cars – Auntie
Only back in 2001 they were not deemed to be ‘highly polluting’ at all – thanks, Auntie. Another whitewash.
And now?
Diesel drivers in London charged up to £250 more per year to park near their home
On-street parking permits are more expensive for diesel vehicles in 18 of the capital’s 32 boroughshttps://www.standard.co.uk/news/london/diesel-london-parking-surcharge-council-darren-rodwell-hackney-merton-b1155859.html
Even though all the major auto companies are going back to petrol and diesel for profit’s sake, the local authorities here are aiming for 15 minute gulags and parking isn’t on the agenda.
Residents of the new Horlicks Quarter housing development in Slough have complained they have nowhere to park – causing problems for them and their neighbours.
https://www.sloughobserver.co.uk/news/24626061.horlicks-quarter-residents-say-left-nowhere-park/
That includes EVs and charging….
Just so.
“The nine most terrifying words in the English language are: I’m from the government, and I’m here to help.”
— US President Ronald Reagan, 1986
I’ve always wondered, when counting words in a sentence, should contractions count as one word or two?
Mr. W: As you know, if the higher number can be made to appear alarming, CliSci counts it as three words.
It’s one word for normal people.
But for those who speak “double speak” (such as most politicians), it’s four words.
I have always believed that “government planning” is an oxymoron.
Then, you have been right.
I live in Vermont
I have three 24000 Btu/h heat pumps with 6 outlets, $24000, already for 5 years.
The energy cost savings for heating never exceeded $200/y
They last about 15 years, so at 6%/y, amortizing my loan payment is $2200 per year.
Where are my savings?
I am not counting any service calls and parts.
A standard propane fired furnace would cost about $7000, lasts about 25 years
I never turn on my heat pumps when the outdoor temp is below 10 – 15 F, because the heat pump would be inefficient and guzzling electricity.
I have an extra meter to prove it
The fancy graph in the article is absolutely wrong in the real world; it is a fairy tale.
BTW, in summer, they act as inefficient air conditioners for a few days of the summer.
The reverse effectiveness of needing heat in the winter when heat pumps are least efficient is clear. At the other end of the spectrum…the air conditioning load on a hot sunny afternoon is a positive synergy with photovoltaic generated electricity for whatever part of the utility electric load is typically consumed by AC….and would be a good fit except uses a lot of real estate….wind generation, however, is random, so doesn’t fit any predictable demand curve, and also takes up a large amount of real estate.
If you have a home heat pump, make sure that its anti-legionella cycle is working.
I have a heat pump (comment to follow). My unit is not connected to water. I do have an electrically heated water tank with plumbing going to kitchen and bathrooms.
The problem is that the power curve for you solar panels are not a good match for your AC requirements. Max power from you panels will be from around 10am to 2pm. While the AC load will peak around 4pm and will often continue long after the sun has completely set.
…much better than wind power was my point….and gives a good idea of how much PV you can add to a grid without huge storage battery costs.
A few things could be done to make a better match between solar and A/C requirements. One is to have solar panels face the west so peak output occurs in the afternoon which also means some power available later in the day. Another is to increase thermal mass in the house so A/C could be shut down in the evening. Batteries.
In regions with significant A/C loads, south facing solar panels don’t make much sense.
California really screwed up big time in not pushing for EV charging stations where cars are parked mid-day.
And I heartily agree with DMackenzie’s comment on how PV can be added.
Facing the panels west is going to reduce their total output. Just sayin’.
You may have a point, but the capacity factor will suffer even more.
Solar panels have no output a lot of the time.
I have two heat pumps at my house, one for the first and one for the second floor. I live in Tennessee where it makes sense to have them in my climate zone. Natural gas heating is not common in our part of Tennessee as gas lines would have to be blasted through bedrock to reach many homes. I don’t know if fuel oil is common. Propane is an option but a pain as you have to keep ordering it. With the heat pumps, I love the electric bills in spring and autumn. Summer isn’t too bad, but winter, woo boy!
Ed Miliband has two kitchens…
Ed Miliband responds to ‘two kitchens’ media furore https://www.bbc.co.uk/news/uk-politics-31875297
We used to live in a house with a propane tank and let me tell you it was no issue. First of all with propane heat, stove and water heater they would fill it in March and come back in September to top it off before winter started. During the coldest months of winter they had to come out every 3 weeks. We were on a contract so they would watch the weather and keep us topped off knowing our historic use versus temperature. All I did was check my propane levels once a week to verify we were good but I never had to call the propane company for a fill.
Today I have a heat pump, it’s OK but wish I had gas heat instead. I very much prefer gas heat and not afraid to toss in a window unit for AC. On the plus side if I have a window AC unit the lizard of a wife doesn’t complain about how cold the entire house is when I turn on the AC. I call her a lizard because she only starts to feel warm in the 80’s and prefers it to be in the 90’s. Sure signs she’s a cold blooded lizard person.
Interesting there’s no mention of falling back to resistive heating coils when the outdoor temperature is too cold for the heat pump – which demands much more electricity to operate. I much prefer the warm heat from my gas furnace to the cool breeze from a struggling heat pump + resistive system when it’s bitterly cold outside.
Yes.
People tend to not use their reverse cycle air-conditioners for heating any more once they receive the next electricity bill.
(speaking from personal experience 😫 )
Yes.
People tend to not use their reverse cycle air-conditioners for heating any more once they receive the next electricity bill.
(speaking from personal experience 😫 )
twice 🙂
We live in Tucson, AZ, and have had heat pumps for 45y. Our local temperatures vary from highs of ~110F in summer to lows of the high 20s for a few days in the winter. The heat pumps start to struggle to maintain 78F when the temp gets into the 20s and barely keeps up if we get into the ‘teens. Electric bills are high at our peak and lowest temps, the cost of new heat pumps has tripled over the past 15y — from ~$5K to ~15K, and the units (if lucky) now last about 10y. Fortunately, Tucson Electric Power service has been highly reliable for the past 45y, but heat pumps, like most machines, fail most often when they are highly stressed — like the hottest and coldest days of the year.
See my above comment.
I do not over-stress my heat pumps.
The outdoor units have roofs over them to keep snow away.
I do not use them below 15 F.
I use my regular 85% efficient propane-fired furnace; German design.
This winter, we have lots of days with below 0 F temps
Also, we have had lots of snow; about 2 ft coverage on our meadows.
A few days ago, we cleared about one foot off our driveway with a snowblower, that starts immediately with 92 octane, no-ethanol gas, bought in gallon cans at Home Depot.
The resistive heat is also used when your Heat Pump is doing a defrost cycle, in addition to very low temperatures. Winter heat costs a lot more than summer cooling.
Mandating a one size fits all solution to any perceived problem is the Marxist way. Shoot – ready -aim is their implementation method. If individuals don’t fit the solution it’s their problem, not the government’s.
Here in the UK Government backed schemes have a proud history of more or less complete failure. In the late 90s early 2000s there was the cavity wall installation scandal followed in the 2010s by the internal cladding scandal. Both schemes led to many thousands of botched installations leading to people left with almost unlivable in houses requiring thousands of pounds worth of remediation.
Ignoring the precedents mad Ed presses ahead with his heat pump schemes even though there is already widespread indication of multiple failed installations and again people’s homes (and lives) being ruined
Burning NG in a modern furnace or water heater loses about 15% of the energy up the flue.
Converting NG to electricity loses about 65% up the chimney and out the cooling system before it even leaves the plant site.
Dumb!
Natural gas at $6/E6Btu burned in a modern condensing furnace (air) or water heater with 85% efficiency has a net delivered cost of $7/E6Btu.
Electricity at $0.15/kWh and 100% efficiency powering a furnace (air) or water heater has a net delivered cost of about $40/E6Btu.
A heat pump using $0.15/kWh and a COP of 3.5 has a net delivered energy cost of about $12/E6Btu. The colder the weather the lower the COP and higher the net cost.
If some salesman suggests replacing NG w heat pump & does not know this he is uninformed.
If he suggests replacing NG w heat pump & does know this, he is a crook.
Excellent analysis of NG vs heat pimps.
The heat pimps are the ones trying to sell you the heat pumps 🙂
Energy efficiency is not necessarily cost efficiency. Electricity in the UK is about 3 times more expensive than gas, so the purported savings from energy efficiency are lost in tte price of the energy required.
One thing not mentioned in tte analysis, is air-moisture content. The heat exchanger on HPs ice up quickly in high moisture content air as air temperature drops. This reduces their efficiency and requires they stop, reverse, ie take heat from the indoor heating system to de-ice.
Great Britain is a damp island particularly in the Winter months. The Nordic Countries may be colder but the air tends to be dry.
Heat pumps reduce by about 5 times the energy consumption, should it be electric or else: that is the best solution every invented for heating or cooling houses. Electric energy being obtained from oil or else is a secondary issue with respect to reduction of amount spent.
In Georgian, Victorian, Edwardian houses they don’t work. There are an awful lot of them, your solution?
Yep 13.2m terraced houses in the UK most of which unsuitable for heat pumps largely through lack of space for the total installation, larger radiators etc.
“Heat pumps reduce by about 5 times the energy consumption,”
No, only in ideal laboratory conditions;
You’ve been reading too much sales hype & then confusing COP with efficiency.
The average real world figs for an air source heat pump are ~ 2.8
In cold, humid conditions, that can drop to less than one; due to defrosting. [e.g. 5kWh in, 3kWh out]
An air source heat pump is one of the worst solutions ever invented for heating in cold, humid conditions. Ground source or water to water are a better bet, but expensive.
Even in laboratory conditions, 5 times is a pipe dream. 3 is much more realistic. In the real world, you would never reach that.
When I was working on developing industrial heat pumps in the 1980s, we achieved 6.1 using a cascade system in the lab, but the same system only got to around 4 in the real world.
Looks like somebody did not bother to read the article.
I remember reading someone’s experience with heat pumps on a Yahoo comment thread. They were quite happy with the performance and was shooting down all the criticism. Their final entry was how content they were with an indoor temperature of 55 – 57 degrees.
I’m not sure Kool-aid drinkers like this are in touch with reality.
They definitely don’t have a Cold Ultrica/allergy like half my family, which kicks in when ambient air drops much below 70.
One person’s utopia is another person’s nightmare.
With an indoor temperature in the 55F range, gas heaters wouldn’t run much either. In places like Florida, both gas and heat pumps would run only a few hours a year.
55f is what the poster/commenter was happy with as the top end performance of their Heat Pump, rather than being able to get more out of their system.
I didn’t make this clear.
Setting a system to 55f as the warmest isn’t a choice a lot of people make.
At least ones who can afford a warmer setting.
What?? 55F… that’s around 13C… that is NOT warm……..
That is a cool winter day around here.
“Their final entry was how content they were with an indoor temperature of 55 – 57 degrees.”
You didn’t mention whether that “55-57” was Fahrenheit or Celsius.
If *F, they must wear a lot of sweaters!
If *C, they must be nudist who take a lot of cold showers! 😎
The plastic hinged push for the switch on our tumble dryer broke so while waiting for a replacement I did some research. Dryers come in 3 flavours: vented, with warm moist air pushed through a hose outside; condenser dryers that collect the water in a reservoir (or you can plumbing in a drain), and heat pump models that vpckaim to be much more energy efficient, but take longer.
Knowing how CoP varies with ambient temperature in heating applications I wondered about the real world performance of these machines when the laundry kit is sited in a garage or low temperature utility room. I eventually found a site that advised that drying times could be 60% longer in rooms below 19C/66F.
So not only does the already lengthy drying time extend, but so does the energy consumption, saving little against the condenser dryer alternative. Of course you could flatter the dryer’s performance by warming the room, but that probably consumes more energy that running the condenser model.
I think that there ought to be more public research available on the tradeoffs between cost and energy consumption and ambient temperature. You should provably only really consider heat pump models if you live in a warm climate or if it will be sited in a warm kitchen.
I had “ductless minisplits” installed as the most practical solution for adding central h/ac to a little cabin I was making into a permanent residence. They seem to be heat pumps, and although here in my part of Texas they have been rather effective, during the real cold spells like we recently had, their performance drops way. way off. Years ago, I took to using a little electric (oil filled radiator) space heater just to take some of the strain off of the minisplits, and now that the system is about 12 years old or so, it is showing signs of wear. I tend to keep summer thermostat set to 78 (F), and winter to 65(F), and if we do lose power, live in insulated coveralls. Have also learned to shut the water off at the meter, and drain the pipes to prevent after the freeze problems. As others have commented, they do serve a purpose, but are not and end all answer.
I live in SoMD, moderate Winters and hot Summers, and have a heat pump with propane backup. Indeed, my cooking, water heating, clothes drying and backup heat are ALL propane. So, for the past 1/4 century I have a propane house augmented with a heat pump for warming during moderately cold periods and cooling during warm periods.
I have never emptied a 500 gallon tank of propane in a year’s use. I’ve never kept detailed records, but can estimate that my annual use is 300-400 gallons of propane. I checked the tank last week, just after our coldest snap in many years and it still reads at 60%, (.6 X 400 = 240 gallons) of the last 80% top off fill. They never fill to 500, but to 400 gallons for hot weather expansion.
So comparing prices, my electric bill is ~$224 monthly while my propane averages ~ 600/ YR ($50/ month). The largest single item of the electric bill is used to run the heat pump. No, I do not know what that percentage is. But I can guess it to conservatively be in the 15-20% range, $36 to $48/month.
Just as an aside, in the 1/4 century plus, I’ve replaced the heat pump twice and the furnace three times. The overall propane use has not changed with an almost imperceptible price change, while electrical costs have gone up by ~300%.
To Dr. Schernikau:
Thank you for an excellent, well-written article that summarizes the complex issues—moreover, the actual facts—surrounding the complex issue of heat pump “efficiency” and how such must be understood in the context of integration of heat pumps in an actual electrical grid.
I greatly appreciate that you point out that a heat pump’s Coefficient of Performance is not the same as its overall energy efficiency . . . not commonly recognized by many, I think.
Caveat emptor!
Funny. In my wakeful hours last night I was planning to write an essay on heat pumps for WUWT.
Let me just say that heat pumps make a good metaphore for the entire sustainable energy movement in this sense: people tend to look just at the individual components, the heat pump being one, without recognizing that components make up a large system. How the system works in total determines what the consumer and ratepayers have to pay for.
A couple of things not mentioned here:
1) Specs for available units do list COP of 1.75 and 2.1 around -10C and continues its decline from there on down. It falls below 1.0 when the source temperature (I.e. outside air or ground) reaches -28C or so because that is the typical refrigerant temperature in the evaporator. At that point there is no source temperature difference to cause spontaneous flow of heat from the source into the refrigerant. Lower temperatures, of course, would actually cause heat to flow the wrong way. Lowest working fuild temperature is a system consideration.
2) Ground sourced heat pumps provide a higher COP than air sourced units because the ground has stored heat from warm seasons in it. However the heat pump withdraws heat from the ground which lowers its temperature, so as winter drags on the COP will decline. the dependence on heat transport by conduction is part of the system; so is the year around climate.
3) Air sourced units condense water vapor on their evaporator coils, and have to reverse cycle on a schedule to shed ice to maintain what COP they have.
4)There is no practical way to install ground source heat pumps in built-up urban areas with lots of multi-family dwellings. Cities are relegated to using air sourced systems.
5) Wait until a person sees the cost of installing a cold climate heat pump (CCHP). Five ton capacity units (about 17KW) are good for say 2,000 square feet of living space, and i’ve seen costs of up to $24,000 for such because retrofitting finished homes can be complicated.
6) I’ve used air-sourced units in diverse climates, but find them not very comfortable because air leaving a duct is above room temperature but not quite warm enough to overcome the chill from moving air. You see, human comfort considerations are part of the system one has to consider.
7) Even in my modern neighborhood there is inadequate transformer capacity for more than a few homes per block switching to heat pumps.
8) Making everything run on electrical energy violates the “diversity is our strength mantra”. Diversity of fuels and sources is a good thing.
Don’t forget “Planning Engineer’s” articles on the penetration problem with respect to electric utilities. One example was heat pumps and the nasty side effect when resistance heating kicked on really cold mornings.
“Making everything run on electrical energy violates the “diversity is our strength mantra”. Diversity of fuels and sources is a good thing.”
It isn’t just diversity that’s good, but also distributed supply, especially when it supports independence from grid connections and other centralized supply. My propane tank can keep my furnace and generator running when the grid is down. The air source heat pump is a decent A/C, but I can certainly manage without it in a power outage.
Ground source heat pumps (GSHP) do not have lower efficiency in the cold.
A vertical borehole for a heat pump (up to 200m deep).
I don’t think ground source is typical. Probably costs more than air source.
Considerably more !!
Yes, ground source have a more constant and higher temperature source, but drilling of this sort isn’t going to occur in urban or suburban places. And there is no getting away from the fact that in cold climates with little need for A/C in summer, you are constantly mining heat from the subsurface and depending on conduction to replace it.
The expense of a 200m borehole will likely exceed the rest of the entire system.
And drilling, what is basically a well, that deep then running lines to and from that depth could be a problem. If it’s a closed loop system, then the closed loop would likely need chemicals added to prevent corrosion. If a leak still develops, then those chemicals are released into the aquafer. And even if a leak doesn’t happen, the well head itself could introduce surface containments into the aquafer.
If you’re going for ground source, best to run lines horizontally below the frost line.
Subsurface heat conduction in static solid material (rock, sand, clay) is so poor that this idea won’t work at all without a sufficiently large rate of flowing (underground) water. My installation has a high flow rate, and I don’t notice any degradation of efficiency throughout the winter. If the local geology doesn’t cooperate, you need to supplement it with your own flowing water, and add that to your running expenses.
Of course, if your neighbours are all trying to extract heat from the same flowing water, someone downstream is likely to have a problem.
It wasn’t cheap to drill the wells, that’s for sure.
They do after the extraction of heat has lowered the ground temp around the installation.
In Prague, Czechia a family home was designed to work with a ground source heat pump – the ground source was located 1 meter below foundations. After several years, repeated freezing and thawing of the ground source threatened to destabilize the house. They had to abandon the ground source.
We put footings well below the frost depth for a reason.
I live where summers can be hot and winters quite cold. [110°F expected in summer; -15°F in winter; extremes might be worse]
Where I live there are two options for thermal energy: propane in a big tank, or electricity (inexpensive in central Washington State). The nearest gas line is 6 miles away. Houses are designed within these constraints. Houses will have a secondary source of heat. Open fireplaces were the historic way, but now wood stoves with catalytic burners are common. Mine uses wood, self-harvested from an on-site wood lot. A neighbor uses wood pellets. The “heat” pump operates as a whole-house cooling system in summer. Many (most) situations are not appropriate, unlike my location and house.
The typical green response in the UK when heat pumps are being dismissed is that they are being installed in Norway and are shown to be cheaper. Well Norway has no history of natural gas heating, they historically in urban areas use electric resistive heating with a COP of 1. So in Norway it does make sense to go for a heat pump with a COP of 3 in mild weather and a COP of 1 when its really cold as you are replacing electricity with electricity. In the UK you are typically replacing gas with electricity with gas being 1/4 price per Kwh of electricity. It just does not add up.
As of early 2026, UK energy prices under the Ofgem price cap are approximately 6.3p per kWh for gas and 26.3p–27.7p per kWh for electricity. Gas is generally about four times cheaper per kWh than electricity, making gas central heating significantly cheaper to run,
Interesting. We live in South Africa and I have put a solar geyser in series with a heat pump geyser. So far, despite of many interruptions because of the bad weather and/or electrical power, we have not had cold water, ever. Touch wood. We have had guaranteed warm water at the lowest cost possible, is what I think. Perhaps a good tip for some of you.
Yep. My heat pump struggles below 20F. And the cold triggers peak demand on electricity.
This comes from personal experience. Down to about 55F the COP can approach 3 for a new hi efficiency heat pump, and goes below 2 at 32F. At the same time system pressures drop at lower temperatures so the amount of heat that can be extracted from the air decreases. Throw in defrost cycles and cold air in leakage and you find that there is no gain from running the heat pump. When the auxiliary heat comes on the COP is 1.0 minus losses in the air handling system. By the way, eliminating cold air in leakage is extremely critical as a little bit of cold air can destroy what little heating the heat pump is achieving as the air passes through the heat exchanger and air handler, and they have to move a lot of air just to get heat out at maximum efficiency.
One of my units is a dual fuel system where natural gas, not electricity, is the backup heat source. I keep the crossover point at the temperature where the COP from the heat pump data sheet is the ratio of electric heat BTUs to NG BTUs taking into account all the efficiencies and inefficiencies on both sides.
From the point of view of the utilities the power demanded by electric auxiliary heat pumps rises sharply as the temperature drops. Steeper than would be the case that would be estimated by using delta T alone. In other words the practical value of a heat pump drops off right when you need it the most. And if it stays cold for weeks ……
My heat pump was great for cooling and dehumidification. I didn’t like it for heating because the thermostat was in the evaporator unit and required the fan to run continuously. During the heating cycle it was okay, but in between cycles the palpable breeze created made you feel colder relative to the room temperature.
On the winter days when the high stays below 20, my heat pump run continously and struggles to keep the indoor temp at 60.