That's an overstatement. Also, people routinely rebel against the introduction of change, but soon become accustomed to it. For quite over a year, heat pumps have made up over 50% of new installs [1]. I don't think it's useful to focus too much on short-term pains here.
And now, the leader of the opposition is attending heat pump PR events, after vehemently opposing the governments plans to promote heat pumps, claiming they were uneconomical.
Are heat pumps economical heating sources in Germany? Power there seems very expensive and natgas cheap. No wonder if there's pushback if you have to do expensive renovation and you don't even end up with lower operational expenses.
Heatpumps can be powered by natgas as well. Heat pumps are just a compressor and a heating element for a defrost cycle. Gas powered compressors are relatively common, e.g. in camping trailer refrigerators.
Also, even with Germany's relatively expensive electricity, heat pumps are economical after 15-20 years, which is good enough.
While that's technically correct (the best kind of correct!), I doubt a lot of natgas heatpumps are being installed in homes at the moment.
I suppose the real economics are going to be better, as you probably need to make gas more expensive by carbon trade or something in order to decarbonise. And electrical power should be very cheap.
It really depends on a lot of factors. For example if you have solar, how well insulated your house is, etc.
I am currently renovating a house in Germany and had a quote for a heat pump system and a quote for a central gas heating system. The heat pump system was quoted at 66.000€, it would however be reduced by 24.750€ to 41.250€ as the government is currently giving a subsidy for these systems. The Gas system was quoted at around 18.000€.
Both of the quotes included removing the old Oil Heating system and disposing of it. The Gas System included the price of connecting to the cities gas supply.
I went with the Gas System, as not only the install would be cheaper, the running cost would also be substantially cheaper. Some electricity providers have a seperate tariff for heat pumps that is marginally cheaper. However even then my calculation was that a Heat Pump would only have a comparable running cost if I also invested in a large Solar install on the Roof.
And yet, like all the issues the conservatives rally against, once the law actually came into force, everyone stopped caring about it and now heatpumps are standard.
Yep, they should be, and now they are anything but. In Austria at least getting AC installed in any urban environment is de facto impossible. There is no law against it, but you need various approvals from multiple parties that you will simply not get. Moreover, Austrians are very against AC in general for various reasons.
I am trying to get AC installed and these are some of the responses I got:
> Air the room properly, wrap a damp towel around yourself and get on with it. With energy prices like these, that's just
throwing money out the window, not to mention the environmental impact.
> I don't think it's bad yet. It's important to keep busy when it's hot, not to moan "it's so hot" and do nothing. Get used to the fact that it's getting hotter every year. Wear more clothes in the cold season. Get used to warmer clothes. Try to do more for the environment. Drive less, throw rubbish in the bin instead - don't get lazy, vote for parties that tackle the climate crisis and don't deny it.
> I just sit around in my underwear and sweat, I prefer it.
In fact it's even more of a problem for new buildings. For old buildings you can complain that the building is unsafe to live in without AC, but new buildings are required to be livable (<26C) without air conditioning, so it's very easy to get a blanket rejection for this very reason alone.
Of course even though new buildings should be livable without AC, this is not true in practice. I live in a new building and right now I have 33C indoors inside my apartment. But some bureaucrat signed that it's 26C certified so who am I to complain!
Wow, ridiculous. In Croatia almost every condo built in the last 20 years has AC already pre-installed (or at least conduits and installation location prepared).
When people talk about head pumps, they usually mean a different type of product than a cooling only AC though, so I'm not quite sure how it's relevant?
(Yes, there are two-way heat pumps, but those are surprisngly rare get and install across europe).
It's basically impossible to buy "cooling only" AC in the EU, everything is also a heat pump now (and it makes total sense, making AC heat instead of cool is just a matter of adding several cheap components to reverse evaporator/condenser roles).
Actually I am trying to get to install a two-way heat pump. As I said, AC is very rare here, but two-way heats pumps are definitely in the collective mind of the few people who care about ACs and heat pumps in Austria. All the AC companies offer them, it's just that you can rarely get a permit to install them.
It's similar in Germany. I understand that historically AC was absolutely not needed and that there were only a couple of weeks where it was uncomfortably hot.
But now it can be multiple months where everyone's productivity clearly drops because it's too hot at the office. And suggesting to improve the conditions by installing an AC or heat pump will invariably result in getting looks like you are a crazy person.
I'm not sure why a majority of people insist in gaslighting that it's not a big deal. If people are actively sweating while sitting at the office they are for sure not at 100% mental effort. Besides, if it really is only a limited time per year when it's needed, you can just not use it the rest of the time, right?
> Answer: Air conditioning. Air conditioning was a most important invention for us, perhaps one of the signal inventions of history. It changed the nature of civilization by making development possible in the tropics. Without air conditioning you can work only in the cool early-morning hours or at dusk. The first thing I did upon becoming prime minister was to install air conditioners in buildings where the civil service worked. This was key to public efficiency.
Everywhere is getting hotter; Europe is seeing heatwaves that exceed temperatures seen even in the tropics. In summer Europe gets 15-16 hours of sunlight, and the fairly high humidity doesn't help. The tropics—especially those countries almost bang-smack on the Equator with Af Köppen–Geiger climate classification—are mostly uniformly warm and wet, with extremely hot (> 37 °C) air temperatures quite rare because of the uniform day-night cycle. And even then the very high humidity means the daytime heat is carried into the night, and the urban heat island effect necessitates air-conditioning indoors in highly built-up cities like the aforementioned Singapore, Kuala Lumpur, and many parts of Indonesia.
Strange. I think it should be illegal to build any public or commercial space without thorough air conditioning. Because of air quality, dust, allergy and stuff, and now after Covid, also a concern of viral particles, a proper ventilation system is definitely a necessity - and it costs too little to make a newly installed, good ventilation system into also an air conditioning system, to pass on that possibility.
Can you say more about this? Heat pumps don't by design ventilate or exchange with outside air. That would be the role of an ERV or HRV or just an exchanger.
That's when we are speaking of an individual system installed in a flat. When we are speaking of a building as a whole, almost all of the cost of installing either a heat pump or just a ventilation system is modifying a building to install air ducts. Which is sometimes a highly invasive, destructive procedure equalling to a near total refurbishment of a building (so this is typically combined: heat insulation + ventilation ducts + general refurbishment, as doing any of the 3 separately won't be much cheaper than doing all 3, anyway). Then you have a single large pipe where a large mass of air enters and and another one where it exits the building. Then it's comparatively not at all hard or expensive to add a massive heat pump so the inlet pipe passes through it (and a heat exchanger between outlet pipe and inlet before, so-called regenerative heating, which will achieve some of the same result, but for free).
That's why i think that buiding-scale ventilation systems without heat pumps make no economic sense. They mean leaving a very low hanging fruit, hanging.
> That's why i think that buiding-scale ventilation systems without heat pumps make no economic sense. They mean leaving a very low hanging fruit, hanging.
That makes some sense. But your call for criminalisation is silly.
Your argument that it makes sense to install aircon might be a good one. But I don't understand why that justifies in any way criminalising buildings without aircon?
I mean, equally cooking tasty food is not actually that much harder nor more expensive than cooking yucky food. But similarly, that's not a reasonable excuse for outlawing any cuisine (or execution of a cuisine) we disagree with.
Its a long studied management theory that most companies in the lead in trying to protect its current profitable product ie cash cow hesitate in innovating as it would destroy their current products market share. This results in competitors coming from behind and out innovating them and stealing market share. This is what is happening to Europe and it's manufacturing industries
I mean a ton of heat pumps are being installed. New houses tend to have heat pumps. The problem is with old houses who already have a heating system installed, it is crazy to overhaul to a heat pump as the cost is not even close to being sensible.
This. The cost of installing and upgrading a big old drafty Victorian house to a COP 4+ efficiency where the running costs actually beat oil/gas would have a break even point way past the end of my lifetime.
Nope, it's very simple. Just don't try to heat up water to heat the house. Use an aircon. In fact, their efficiency is even better. 4+ is already standard, 5+ is good and there are even models that go beyond 6.
Only problem can be if you have a lot of tiny rooms - in that case it's expensive to install everything.
Those figures are for the unit itself. It takes a lot less energy to heat air than it does to heat water, but water retains heat for much longer.
What matters is the SCOP for the system as a whole.
In a traditional Victorian house with a fireplace in every room, radiant heat will provide far greater efficiency than a forced air system, in which all of that warm air will literally go straight up the chimney.
> What matters is the SCOP for the system as a whole.
That's exactly what my numbers are.
They are the efficiencies for moving the heat-energy from the outside air into the inside air, assuming constant 20 degrees celcius indoor temperature and a specifically weighted outdoor temperature (there are multiple types of SCOPs, depending on the climate-zone and I was refering to the moderate one as it is present in most of middle Europe).
Whether you transfer the heat from the outside air (or some other medium) into the indoor air or into the indoor water does not matter - except that for the latter, you will need to consider that the water has to still transfer the heat to the indoor air, so you need to know how hot the water will have to be to calculate the SCOP correctly for your house.
> In a traditional Victorian house with a fireplace in every room, radiant heat will provide far greater efficiency than a forced air system, in which all of that warm air will literally go straight up the chimney.
What kind of "efficiency" are you even talking about? Can you please provide a definition and some example calculation? Otherwise it's meaningless to discuss.
exactly, our neighbour has a oil heating system which is a size of a room in her cellar. simply uninstalling and removing it is beyond anything she, a pensioner, can pay. unless the government picks up the replacement costs, she will keep burning oil.
Basically no one ever has recommended throwing out a well-working existing heating system. But heating systems, including radiators, tanks and furnaces, have limited life spans. Usually 20-30 years. At some point it is not economical to repair them, spare parts may not even be available anymore or laws have changed that require particularly old and dirty furnaces to be removed.
In those cases, heat pumps are usually the more economical choice, depending on government incentives and other considerations. For example, it is quite certain that current EU-legislation concerning the inclusion of domestic fossil fuel usage in the CO2-certificate trading scheme will result result in price increases of 20-40% for natural gas and heating oil by 2035 or so.
This includes older houses. Modern heat pumps are quite capable of heating even less insulated houses economically.
My mother won't install a heat pump because she claims she doesn't want to be dependent on electricity. She likes the idea that if it goes down, she can still heat her home.
It is irrational because her gas burner needs electricity to run anyway, and if electricity shuts down, she lights a wood fire, which she could have as an alternative to the heat pump.
Humans have religion-like behavior in every aspect of their life, not just God-related things.
If you haven't heard about the French pushback against the linky, a smart electricity meter, google it. You will have a good overview of what can go wrong if we force the issue on people.
As a nerd, I get you think it was the main problem.
But most people didn't care about that.
The main contenders were:
- Linky calculates my electricity bill badly. It was in fact more accurate, but sometimes it meant a raise in bill.
- Linky emits dangerous radiation or magnetism. That was, of course, a total hoax.
- Linky didn't allow me to cheat on my bill anymore (lots of people around me were hacking their meter to pay less).
- Linky is forced on us by Big Electricity. So it's bad.
The privacy thing is legit, but all those people had full facebook accounts, most of them had full sync on their smartphone, use chrome without an adblock, and so on.
Only geeks like us really care about the privacy aspect.
On the other hand, it's a greener solution:
- Less people in cars to check meters.
- Live load balancing on the power grid.
- Clear consumption stats so that you can optimize your own bill.
So the linky, which eventually got into most homes, is deployed with success.
But it took so many years because of the pushback.
Eventually, if the pushback would have been just about the privacy, we could have focused on fixing that and would have had a cheaper, faster deployment, with privacy.
We had the worst: expensive, long deployment, and the privacy invasion is still in place.
Heat pumps prices here keep going UP, not down. The very same machine cost more after few years. There is no chance to keep up such conversion at these rates.
I'm one of the few who have built a new home, all electric main car included, and yes even friends and parents told me it's a mistake, it will cost much more heating and cooling or it's even impossible to heat and so on. There is much resistance but the real point are prices. Similarly to BEVs.
In other places prices drop, that's why sales goes up, here they do the opposite and that's why sales goes down.
In cold climates many people still use gas heating because its cheaper, making electricity cheaper would be the only realistic way to increase heat-pump usage in winter.
We don't use gas much for heating in northern Europe. At least not in Scandinavia, Iceland and Finland (Maybe Denmark is a small exception). Norway is also Europe's biggest gas exporter.
I don't think gas heating is noticeably cheaper than heat pumps, but smaller upfront costs.
There's a saying that I've been hearing since being a kid, that heat pump sucks because it's just instantaneous heat but as soon as you turn it off, the heat disappears in an instant.
Based on my experience, it's true. As for the other people. it must be true too, because the norm in my southern country is to have installed proper radiators all around the house. Family, friends, formal visits, I wouldn't be able to name even once in my life that I've been at someone's main place during winter without its proper radiator installation. And when it is turned off, the whole building is warm, not only the air in the living areas, so the place stays warm for a long time.
So heat pumps exist but just as a "not very good" alternative, relegated for things like small secondary homes at the beach (where it doesn't get too cold anyway).
EDIT- I was thinking about the aircon that on winter can be switched to output warm air. But reading replies I'm now learning that heatpump doesn't necessarily always mean air, but radiators could also be used!
I don’t think that’s true for modern isolated (passive) houses built in EU standard. And heat pumps don’t need to be air based, a lot of them transfer heat with water radiators inside the floor.
Around here those are the only ones not subsidised because they are less efficient and usually only a single room solution.
If you have a heat pump driven water boiler for your hot water supply you even get the bonus of allowing it to cool the room in the summer (if properly installed with a switchable duct for winter usage).
You can have floor heating with heat pumps, too. Just heat up the water to a lower temperature (~40C) for longer. It's still way more efficient than burning gas.
It doesn't make sense, though. You need the same amount of energy to heat up a room, regardless of how you produce the aforementioned heat. If the energy immediately dissipates, it means the building has very poor insulation.
In order to heat up a radiator you need very hot water (>60C), that takes a while to heat up and then sits in the radiator slowly cooling off. Simply keep the air pump on for longer at 20C and you'll get the same temperature for _way_ less energy consumption. With a radiator you simply consume more energy upfront, you don't save money (on the contrary, you spend way more if the electricity doesn't come from fossil fuels because burning things is not efficient by any metric).
The answer is simple: just don't turn the heat pump off. Problem solved.
Now, the misconception is that people are thinking in terms of "if it's on, it costs a lot of energy, if you turn it off, you save that enegry". But for heatpumps, that's not true. Running them 2 hours with 50% eletrical power costs less energy than running them 1 hour with 100% eletrical power.
The efficiency of heatpumps is non-linear, whereas it is linear for radiators which is unfamiliar to people.
That's very interesting! And of course, it'd be very unintuitive for most people. Maybe more education is needed to help people understand how to optimize their energy bill with heat pumps.
I've never heard that hearing. I've been living in multiple houses heated primarily with a heat pump in the winter during average temperature of minus 10 Celsius, ranging from 0 to -30.
My current garage has radiators installed but I've never used them as the heat pump is just fine.
I guess they must build the houses or heat pumps differently where you live!
Why is this a contradiction. Modern heat pumps at least in Germany are using the normal water based radiators. It is true that they are more efficient if used with floor or wall integrated radiators. But they are already more efficient looking at the current energy mix (and the current load) here by just exchanging your gas or oil based central heating with a heat pump.
It shouldn't work like that. The heat doesn't "know" if it came from a radiator or a heat pump. That should not matter for how fast the same heat dissipates.
With air-air heat pumps you get warm air and the air has to warm up the walls, furniture, ground and so on. Warmer air rises so in order to warm up the ground (or your feet) it has to displace/heat all of the cold air first. If you vent before the room itself has been warmed up, you have to start over.
Floor heating on the other hand heats up the floor and anything standing on it first. The heat still rises but by the time the hot air has displaced/heated all of the cold air, everything else will already be warmed up and give off heat if the air is vented.
Of course the correct answer is that heat pumps don't need to be turned off because it's actually more energy efficient to run them at lower settings for longer. And with proper insulation heat loss from air currents is less of a problem so this is more of a consideration for heating up a room from scratch (e.g. after turning down the heat pump during a vacation).
This doesn't make any sense at all. Standard heat pump installations include a buffer tank (usually at least a couple 100 liters but possibly much more depending on the details of the installation). The heat pump does not heat the house directly, but the buffer tank. The buffer tank in turn sends warm water to the radiators and warm water faucets, etc.
This is the same principle as in traditional gas and oil boilers. The only difference is that in newer, well insulated buildings, radiators need much lower temperatures so they may feel colder to the touch (i.e. you don't burn yourself on a radiator anymore).
But modern heat pumps also can provide relatively high temperatures in case of installation in older buildings with legacy radiators (70°C are not really an issue anymore).
"So heat pumps exist but just as a "not very good" alternative, relegated for things like small secondary homes at the beach (where it doesn't get too cold anyway)."
In Germany, famously not a very warm country, heat pumps are used in well over 50% of all building projects requiring a permit (this includes renovations). Heat pumps are the definite standard, not an "alternative".
- air-air heat pumps which function like "inverted" AC, which is what you were thinking of - another quirk being that in some models the air vents have optional electric heating which provides more instant more intense heat at the cost of massive energy use
- air-water heat pumps which use air to heat up water similarly to a conventional boiler - a noteworthy difference is that they usually target 40°C instead of 60°C but like other heat pumps they're very energy efficient and are typically used with floor heating
- brine-water heat pumps which use brine running through underground pipes to heat up water similar to air-water heat pumps - these are arguably more efficient but more expensive to install due to the excavation necessary to lay the heat exchange pipes
The latter can further be categorized based on the layout of the underground pipes (YMMV on the exact nomenclature as English is not my native language):
- area collectors use a horizontal grid requiring a large area of land and limiting its use for things like trees or swimming pools (or anything that needs to go deeper)
- trench collectors use a vertical grid, essentially turning the area collector on its side - these of course require much deeper excavation but have a much narrower footprint but depending on where you live you may need to get additional permits
- basket collectors use a three-dimensional grid, usually split across a number of "cages" or "baskets" combining the footprint advantage of a trench collector with the depth advantage of an area collector
In Germany air-air heat pumps are the default with many prefab construction companies due to the ease of installation. When we built our house with a conventional construction company we went with a water-air heat pump because that's what the plumbing company was most experienced with. A brine-water heat pump would have been a good option due to the soil consistency and ground water level but sadly national regulations enforced a minimum depth much lower than what would have been otherwise possible and this made the option cost prohibitive for us.
The main advantage of air-air heat pumps is that they can be better used for cooling (because at the end of the day it's literally just AC) whereas other heat pumps are usually capped by the dew point to avoid condensation.
Talking about air conditioner-style heat pumps here,
> as soon as you turn it off
You're not supposed to turn it off - then the room will get cold again. Spending the energy to heat up the whole house and radiator mass is very energy-inefficient. Just leaving the air heat pump on the whole time, letting the thermostat regulate and just heating the air inside the home is more efficient, even though it's "running for longer".
Another issue with heat pump rollout, at least in the UK is a severe lack of qualified heating engineers with a basic understanding of thermodynamic principles.
Thus you get plumbers with experience installing gas boilers, resulting in poorly specified and installed systems that provide nowhere near the efficiency that they should reach.
This then leads people to say “heat pumps don’t work” or “heat pumps are expensive to run”, which only feeds into the whole anti net-zero rhetoric.
It would only need to be 4.7 to beat a gas/oil system that is 100% efficient.
In reality, a very good gas based system that is well specified and installed might reach 80% as a whole. Most UK gas/oil heating systems are significantly lower.
According to the Heat Geek (in the UK) their minimum is 3.5 and their current average is 4.4. I saw a video[0] they did with Urban Plumbers and they visited a new build (well insulated) where the SCOP was 2.2. The main reason it was so low was the heat pump was over specced (by almost 4 times!) and the pump was cycling constantly.
I should also note that Heat Geek said, controversially, that one of their biggest indicators of a bad job is companies with more experience as such companies usually had a good reputation along with bad habits. Since customers don't know how these systems work or are expected to perform there is no good feedback mechanism apart from customer not complaining which is less likely as customers don't know what to expect in the way of bills being reduced in a properly working system.
> The main reason it was so low was the heat pump was over specced (by almost 4 times!) and the pump was cycling constantly.
You can find over-specing in the US/CA as well because of rules of thumb, or installers just looking at what the old system was and replacing it 1:1 with the same new system—never mind that more insulation or better windows have been perhaps put in.
For new builds, a lot of jurisdictions are mandating standardized calculations be done for estimated energy needs, equipment selection, etc:
If you're going to do a retrofit/replacement, it may be worth finding an HVAC company that will do that process for your non-new dwelling. The fact that a company could offer it may mean they're a step above Random Bob's HVAC.
Performance numbers from well designed systems aren't relevant to the fears of people who've heard the horror stories.
And there are horror stories from there being too many poorly qualified green installers doing a half-job. Some systems wildly underperform. My octogenarian neighbour had no central heating for two weeks while a replacement pump motor could be sourced and somebody could be found to fit it. You wouldn't have that with gas.
Heat pumps are catching up —I want them to win, we need them to— but this stuff has to get better. Installing one should be certified, performance should be mandated to protect consumers and grant money.
> Installing one should be certified, performance should be mandated to protect consumers and grant money.
How is a certificate and a mandate that
oliwarner suggested going to provide heat? Burning a certificate takes at most a few seconds.
To spell it out for you, the mechanism is pretty much the same as elsewhere:
Companies can offer customers some warranties that their system will work as advertised (ie provide heat with a minimum of fuel). Lots of companies in the private sector offer such warranties on a variety of products. The warranty by itself does not keep you warm, but it typically provides for some restitution in case of failure. (In an extreme case, you can imagine that people would be happy to be paid a million dollars in return for putting up without heat for two weeks. In practice, the warranty will probably settle on something less extreme. For example, some modest monetary compensation plus help with sourcing propane heaters as you suggest. Your imagination is the limit here.)
Because the small companies that do this kind of heat pump installation go bankrupt and disappear all the time, you can administer the warranty via a third party insurance company.
And here's where the certificates come in: just like some car insurance companies give you discounts in return for eg a clean driving record, you would imagine that your heat pump installation company would also be able to purchase much cheaper insurance to benefit their customers if they can provide evidence that they know what they are doing.
In practice the main benefit of the whole scheme would come from insurance companies keeping an eye on the installation companies. The payouts are mostly there to provide discipline and align incentives; but in a well running system the payouts shouldn't be necessary very often.
I had a plumber tell me that if I left the filling loop open then the pressure in the radiators would just keep rising and rising forever until they burst. He didn't agree that it would stop at equilibrium with mains pressure.
> This then leads people to say “heat pumps don’t work” or “heat pumps are expensive to run”
When I was doing some extensive renovations of a house about 7 years ago now (in the UK), we called a company whose main business was to install heat pumps (along with underfloor heating, etc). The person asked me a bunch of questions, and based on the age of the house and the insulation and such, she said, "I appreciate what you're trying to do, but I'm really worried that a heat pump won't be able to heat your house sufficiently on cold days; I'd really recommend that you take the money you'd spend on a heat pump and spend it on better insulation for the house instead."
Given that's their main business, and that she was knowingly turning me away as a customer, I tend to give some credence to her assessment. At least it can't be due to a lack of understanding or bias.
Now that our house is better insulated, I might try again next time our boiler is up for replacement, particularly if I can arrange to get the heat pump to cool the floors in the summertime as well as heat them in the wintertime.
WRT cooling with water based system there are a few of issues:
1. A system that also provides cooling isn’t allowed under the heat pump government grant.
2. You might actually need planning permission for this
3. Especially in a humid environment like the uk, you can end up with condensation and damp issues, which you really don’t want in an underfloor slab install
If you also want cooling, better to go an air-air based system (aka air conditioning)
The situation with respect to condensation: look at historical data for the dew point during the summer season. That as low as you can get. For example, I'm in The Netherlands and our system is set to 18 degrees Celsius.
The amount of cooling this way is limited. Though the nice thing is that it tends to keep the house cool. There is no cold airflow.
With respect to government grants. Sometimes you can buy units that can only heat to get the grant. But a simple change enables cooling after the unit is installed.
You can also just look up what the dew point is on any particular day, and adjust your temperature.
In general, if you want to save money, you should set your aircon to the highest temperature you can tolerate. We typically operate at 26-28C at home here in Singapore, and our dew point is typically between 24-26C.
The modest reduction in air temperature from 30-33C outside feels amplified, because the aircon also reduces humidity. We also rely heavily on ceiling fans.
If their working fluid is water, you are right. But most aircons work like fridges, and their pipes don't transport 'cold' by literally having a cold fluid, but by having an ambient temperature fluid that they turn into a gas inside your interior aircon unit (and then later turn back from a gas into a liquid on the outside unit).
The actual pipes are always at pretty much ambient temperatures.
> 3. Especially in a humid environment like the uk, you can end up with condensation and damp issues, which you really don’t want in an underfloor slab install
You only end up with condensation issues, if you cool below the dew point.
Here in very humid Singapore our dew point is typically at about 24-26C. If you set your aircon to no less than 26C here, you never have any problems with condensation.
(Any old weather reporting website or app will tell the dew point. Apparently right now as I am writing this comments, it's 12C in London.)
My friend's father owns an AC/heat pump/PV installation business and by his account it's even worse, as the most common issue seems to be that piping is poorly laid out and/or insulated, making a huge chunk of the heat escape into the ground.
How was that not an issue with coal/gas boilers? I don't know. Perhaps people just cranked up the gas and lived with the resulting bills.
People talk about needing larger radiators for heat pumps. You also needed similar sized radiators for condensing gas boilers to work at the claimed efficiency.
People were just burning 20% more gas for no good reason.
That would be my thinking as well, as it's analogous to how people use internal combustion cars - everyone seems to just accept the fact that in city driving fuel-to-wheels efficiency just drops below 20%.
It is worse for heat pumps. For condensing boilers the return water temperature needs to be low enough, but the system can easily be set to 60 degrees.
For heat pumps, 40 degrees is about the max for efficient operation. So radiators need to be quite a bit bigger compared to what you need for a condensing boiler.
> The correct temperature setting for heating on a combi boiler is 'as low as possible', but as a guide most older homes can run their heating systems at 60°C and newer homes at 50-55°C. They start to reach their very highest efficiency potential at 45°C flow temperature or lower, but this can be too low for older properties.
> Ultimately how low you can turn your flow temperature down will depend on the size of your radiators, how well insulated your home is and your thermostat temperature.
....
> A vast skills and knowledge gap (that dates back to 2005 when condensing gas boilers become mandatory) means 99% of installers do not understand how condensing gas boilers work and therefore cannot set them up to run as they were designed to. Installers have been let down and so have UK households. We have simply not benefited as much as we should have from this leap forward in boiler efficiency.
Then you are talking about something else. If the return temperature is below 40 degrees then the condensing mode kicks in. This can typically be achieved if the system is set to 60 degrees. Most radiators for this type of system work well with a temperature drop of 20 degrees. Obviously the flow should be adjusted accordingly.
If you go lower, efficiency may increase by tiny amounts, but in most practical setups the system is likely to become unstable and you will lose more than you gain. This is especially true if the system is also used to provide hot tap water. For hot tap water, in particular for a shower, the system needs to be able to heat a lot of water quickly.
Can this really be solved without proper insulation? I’m from a cold place with excellent insulation, and everywhere else I’ve been in the world, it subjectively feels like the heat is disappearing half an hour after turning off the heat source. This includes places that gets near freezing cold in winter. Like trying to empty a leaking boat with a bucket.
Windows are the worst. I'm constantly telling my mom to lock the windows in winter. They are meant to be locked. If not you can feel the heat escaping it's so cold next to the window. One was even up a few mm!
Mom grew up on a farm in the 1950s in a big farm house that thing leaked air. It was so cold they used to put a heated brick in their beds to warm it before bedtime.
If it was wood fired, it was likely designed to leak air. I was somewhat surprised to learn that the steam heating all over NYC was designed to be used with the windows open.
Air source heat pumps are at least 300% to 400% more efficient than just electrical resistance heat. Ground-source heat pumps are even more efficient.
All you do is use a bit of electricity to power a pump and some fluid to move heat around no need to burn things. Even better if the power comes from solar, wind, hydro, nuclear.
I'm not an expert, by dry air has a very low heat capacity. So you get a house with cold walls, floor and roof. And the dry warm air is rather ineffective in transferring heat to the walls, floors, etc.
In contrast, if you have underfloor heating, you have a relatively large surface filled with warm water that heats up the floor. And then you have an even bigger surface that transfers heat to the rest of the house.
In the end the house is more easy to heat because it doesn't depend on an airflow to reach all parts the house.
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[ 2.8 ms ] story [ 159 ms ] thread[1] https://www.bdew.de/service/daten-und-grafiken/entwicklung-b...
However, the damage is done.
Also, even with Germany's relatively expensive electricity, heat pumps are economical after 15-20 years, which is good enough.
I suppose the real economics are going to be better, as you probably need to make gas more expensive by carbon trade or something in order to decarbonise. And electrical power should be very cheap.
I am currently renovating a house in Germany and had a quote for a heat pump system and a quote for a central gas heating system. The heat pump system was quoted at 66.000€, it would however be reduced by 24.750€ to 41.250€ as the government is currently giving a subsidy for these systems. The Gas system was quoted at around 18.000€.
Both of the quotes included removing the old Oil Heating system and disposing of it. The Gas System included the price of connecting to the cities gas supply.
I went with the Gas System, as not only the install would be cheaper, the running cost would also be substantially cheaper. Some electricity providers have a seperate tariff for heat pumps that is marginally cheaper. However even then my calculation was that a Heat Pump would only have a comparable running cost if I also invested in a large Solar install on the Roof.
I am trying to get AC installed and these are some of the responses I got:
> Air the room properly, wrap a damp towel around yourself and get on with it. With energy prices like these, that's just throwing money out the window, not to mention the environmental impact.
> I don't think it's bad yet. It's important to keep busy when it's hot, not to moan "it's so hot" and do nothing. Get used to the fact that it's getting hotter every year. Wear more clothes in the cold season. Get used to warmer clothes. Try to do more for the environment. Drive less, throw rubbish in the bin instead - don't get lazy, vote for parties that tackle the climate crisis and don't deny it.
> I just sit around in my underwear and sweat, I prefer it.
I can't even...
Of course even though new buildings should be livable without AC, this is not true in practice. I live in a new building and right now I have 33C indoors inside my apartment. But some bureaucrat signed that it's 26C certified so who am I to complain!
(Yes, there are two-way heat pumps, but those are surprisngly rare get and install across europe).
(The majority of installations are for heating only with separate A/C units if they exist at all.)
But now it can be multiple months where everyone's productivity clearly drops because it's too hot at the office. And suggesting to improve the conditions by installing an AC or heat pump will invariably result in getting looks like you are a crazy person.
I'm not sure why a majority of people insist in gaslighting that it's not a big deal. If people are actively sweating while sitting at the office they are for sure not at 100% mental effort. Besides, if it really is only a limited time per year when it's needed, you can just not use it the rest of the time, right?
Lee Kuan Yew, first prime minister of Singapore, said this about air-conditioning[1][2]:
> Question: Anything else besides multicultural tolerance that enabled Singapore's success?
> Answer: Air conditioning. Air conditioning was a most important invention for us, perhaps one of the signal inventions of history. It changed the nature of civilization by making development possible in the tropics. Without air conditioning you can work only in the cool early-morning hours or at dusk. The first thing I did upon becoming prime minister was to install air conditioners in buildings where the civil service worked. This was key to public efficiency.
Everywhere is getting hotter; Europe is seeing heatwaves that exceed temperatures seen even in the tropics. In summer Europe gets 15-16 hours of sunlight, and the fairly high humidity doesn't help. The tropics—especially those countries almost bang-smack on the Equator with Af Köppen–Geiger climate classification—are mostly uniformly warm and wet, with extremely hot (> 37 °C) air temperatures quite rare because of the uniform day-night cycle. And even then the very high humidity means the daytime heat is carried into the night, and the urban heat island effect necessitates air-conditioning indoors in highly built-up cities like the aforementioned Singapore, Kuala Lumpur, and many parts of Indonesia.
[1]: https://doi.org/10.1111/j.1540-5842.2009.01120.x
[2]: https://www.vox.com/2015/3/23/8278085/singapore-lee-kuan-yew...
That's why i think that buiding-scale ventilation systems without heat pumps make no economic sense. They mean leaving a very low hanging fruit, hanging.
That makes some sense. But your call for criminalisation is silly.
I mean, equally cooking tasty food is not actually that much harder nor more expensive than cooking yucky food. But similarly, that's not a reasonable excuse for outlawing any cuisine (or execution of a cuisine) we disagree with.
I live in a 2-floor building covered under trees (built in 1936) and even when it’s above 30 degrees it is pleasant in our house.
We pay a lot for the trees to be properly managed, but it’s for sure less than cooling the house with A/C would be.
What happens if you just wheel in a portable AC unit and duct it out a back window?
I still use one but it's very far from ideal.
[0] so loud that neighbours might complain, I had neighbours complain about my computer fans running 24/7.
[1] https://www.youtube.com/watch?v=_-mBeYC2KGc
You could import one.
> Generally nothing
I'm surprised, then, that the EU AC bans we're discussing don't lead to mass noncompliance and civil disobedience.
Only problem can be if you have a lot of tiny rooms - in that case it's expensive to install everything.
What matters is the SCOP for the system as a whole.
In a traditional Victorian house with a fireplace in every room, radiant heat will provide far greater efficiency than a forced air system, in which all of that warm air will literally go straight up the chimney.
No.
> What matters is the SCOP for the system as a whole.
That's exactly what my numbers are.
They are the efficiencies for moving the heat-energy from the outside air into the inside air, assuming constant 20 degrees celcius indoor temperature and a specifically weighted outdoor temperature (there are multiple types of SCOPs, depending on the climate-zone and I was refering to the moderate one as it is present in most of middle Europe).
Whether you transfer the heat from the outside air (or some other medium) into the indoor air or into the indoor water does not matter - except that for the latter, you will need to consider that the water has to still transfer the heat to the indoor air, so you need to know how hot the water will have to be to calculate the SCOP correctly for your house.
> In a traditional Victorian house with a fireplace in every room, radiant heat will provide far greater efficiency than a forced air system, in which all of that warm air will literally go straight up the chimney.
What kind of "efficiency" are you even talking about? Can you please provide a definition and some example calculation? Otherwise it's meaningless to discuss.
In those cases, heat pumps are usually the more economical choice, depending on government incentives and other considerations. For example, it is quite certain that current EU-legislation concerning the inclusion of domestic fossil fuel usage in the CO2-certificate trading scheme will result result in price increases of 20-40% for natural gas and heating oil by 2035 or so.
This includes older houses. Modern heat pumps are quite capable of heating even less insulated houses economically.
My mother won't install a heat pump because she claims she doesn't want to be dependent on electricity. She likes the idea that if it goes down, she can still heat her home.
It is irrational because her gas burner needs electricity to run anyway, and if electricity shuts down, she lights a wood fire, which she could have as an alternative to the heat pump.
Humans have religion-like behavior in every aspect of their life, not just God-related things.
If you haven't heard about the French pushback against the linky, a smart electricity meter, google it. You will have a good overview of what can go wrong if we force the issue on people.
She doesn't care about making sense.
She cares about her stance on electricity heating.
I’m putting in underfloor heating powered with an air source heat pump, but leaving the boiler and radiators in place for midwinter and power cuts.
Most people don't do that.
"I heard that..."
"I believe that..."
Is mostly the source of their decision making.
Forcing heat pump on people will make them react like you are stealing from them.
Because you are: you are stealing their ability to choose.
But they choose badly.
But most people didn't care about that.
The main contenders were:
- Linky calculates my electricity bill badly. It was in fact more accurate, but sometimes it meant a raise in bill.
- Linky emits dangerous radiation or magnetism. That was, of course, a total hoax.
- Linky didn't allow me to cheat on my bill anymore (lots of people around me were hacking their meter to pay less).
- Linky is forced on us by Big Electricity. So it's bad.
The privacy thing is legit, but all those people had full facebook accounts, most of them had full sync on their smartphone, use chrome without an adblock, and so on.
Only geeks like us really care about the privacy aspect.
On the other hand, it's a greener solution:
- Less people in cars to check meters.
- Live load balancing on the power grid.
- Clear consumption stats so that you can optimize your own bill.
So the linky, which eventually got into most homes, is deployed with success.
But it took so many years because of the pushback.
Eventually, if the pushback would have been just about the privacy, we could have focused on fixing that and would have had a cheaper, faster deployment, with privacy.
We had the worst: expensive, long deployment, and the privacy invasion is still in place.
I'm one of the few who have built a new home, all electric main car included, and yes even friends and parents told me it's a mistake, it will cost much more heating and cooling or it's even impossible to heat and so on. There is much resistance but the real point are prices. Similarly to BEVs.
In other places prices drop, that's why sales goes up, here they do the opposite and that's why sales goes down.
In cold climates many people still use gas heating because its cheaper, making electricity cheaper would be the only realistic way to increase heat-pump usage in winter.
Based on my experience, it's true. As for the other people. it must be true too, because the norm in my southern country is to have installed proper radiators all around the house. Family, friends, formal visits, I wouldn't be able to name even once in my life that I've been at someone's main place during winter without its proper radiator installation. And when it is turned off, the whole building is warm, not only the air in the living areas, so the place stays warm for a long time.
So heat pumps exist but just as a "not very good" alternative, relegated for things like small secondary homes at the beach (where it doesn't get too cold anyway).
EDIT- I was thinking about the aircon that on winter can be switched to output warm air. But reading replies I'm now learning that heatpump doesn't necessarily always mean air, but radiators could also be used!
If you have a heat pump driven water boiler for your hot water supply you even get the bonus of allowing it to cool the room in the summer (if properly installed with a switchable duct for winter usage).
In order to heat up a radiator you need very hot water (>60C), that takes a while to heat up and then sits in the radiator slowly cooling off. Simply keep the air pump on for longer at 20C and you'll get the same temperature for _way_ less energy consumption. With a radiator you simply consume more energy upfront, you don't save money (on the contrary, you spend way more if the electricity doesn't come from fossil fuels because burning things is not efficient by any metric).
Now, the misconception is that people are thinking in terms of "if it's on, it costs a lot of energy, if you turn it off, you save that enegry". But for heatpumps, that's not true. Running them 2 hours with 50% eletrical power costs less energy than running them 1 hour with 100% eletrical power.
The efficiency of heatpumps is non-linear, whereas it is linear for radiators which is unfamiliar to people.
My current garage has radiators installed but I've never used them as the heat pump is just fine.
I guess they must build the houses or heat pumps differently where you live!
Ofc you can hook the pump to a water circuit with traditional radiators…
With air-air heat pumps you get warm air and the air has to warm up the walls, furniture, ground and so on. Warmer air rises so in order to warm up the ground (or your feet) it has to displace/heat all of the cold air first. If you vent before the room itself has been warmed up, you have to start over.
Floor heating on the other hand heats up the floor and anything standing on it first. The heat still rises but by the time the hot air has displaced/heated all of the cold air, everything else will already be warmed up and give off heat if the air is vented.
Of course the correct answer is that heat pumps don't need to be turned off because it's actually more energy efficient to run them at lower settings for longer. And with proper insulation heat loss from air currents is less of a problem so this is more of a consideration for heating up a room from scratch (e.g. after turning down the heat pump during a vacation).
This is the same principle as in traditional gas and oil boilers. The only difference is that in newer, well insulated buildings, radiators need much lower temperatures so they may feel colder to the touch (i.e. you don't burn yourself on a radiator anymore).
But modern heat pumps also can provide relatively high temperatures in case of installation in older buildings with legacy radiators (70°C are not really an issue anymore).
"So heat pumps exist but just as a "not very good" alternative, relegated for things like small secondary homes at the beach (where it doesn't get too cold anyway)."
In Germany, famously not a very warm country, heat pumps are used in well over 50% of all building projects requiring a permit (this includes renovations). Heat pumps are the definite standard, not an "alternative".
- air-air heat pumps which function like "inverted" AC, which is what you were thinking of - another quirk being that in some models the air vents have optional electric heating which provides more instant more intense heat at the cost of massive energy use
- air-water heat pumps which use air to heat up water similarly to a conventional boiler - a noteworthy difference is that they usually target 40°C instead of 60°C but like other heat pumps they're very energy efficient and are typically used with floor heating
- brine-water heat pumps which use brine running through underground pipes to heat up water similar to air-water heat pumps - these are arguably more efficient but more expensive to install due to the excavation necessary to lay the heat exchange pipes
The latter can further be categorized based on the layout of the underground pipes (YMMV on the exact nomenclature as English is not my native language):
- area collectors use a horizontal grid requiring a large area of land and limiting its use for things like trees or swimming pools (or anything that needs to go deeper)
- trench collectors use a vertical grid, essentially turning the area collector on its side - these of course require much deeper excavation but have a much narrower footprint but depending on where you live you may need to get additional permits
- basket collectors use a three-dimensional grid, usually split across a number of "cages" or "baskets" combining the footprint advantage of a trench collector with the depth advantage of an area collector
In Germany air-air heat pumps are the default with many prefab construction companies due to the ease of installation. When we built our house with a conventional construction company we went with a water-air heat pump because that's what the plumbing company was most experienced with. A brine-water heat pump would have been a good option due to the soil consistency and ground water level but sadly national regulations enforced a minimum depth much lower than what would have been otherwise possible and this made the option cost prohibitive for us.
The main advantage of air-air heat pumps is that they can be better used for cooling (because at the end of the day it's literally just AC) whereas other heat pumps are usually capped by the dew point to avoid condensation.
> as soon as you turn it off
You're not supposed to turn it off - then the room will get cold again. Spending the energy to heat up the whole house and radiator mass is very energy-inefficient. Just leaving the air heat pump on the whole time, letting the thermostat regulate and just heating the air inside the home is more efficient, even though it's "running for longer".
Thus you get plumbers with experience installing gas boilers, resulting in poorly specified and installed systems that provide nowhere near the efficiency that they should reach.
This then leads people to say “heat pumps don’t work” or “heat pumps are expensive to run”, which only feeds into the whole anti net-zero rhetoric.
> without a basic understanding of thermodynamic principles.
that when you have them come quote say “heat pumps don’t work” or “heat pumps are expensive to run”
Tell me, what is the average SCOP of heat pumps in the UK and what is the ratio between the price of electricity and gas?
https://www.lowcarbonhub.org/p/spark-gap/
The UK is worst in Europe and has been as high as 4.7x recently, more than the average Heat Pump can overcome.
In reality, a very good gas based system that is well specified and installed might reach 80% as a whole. Most UK gas/oil heating systems are significantly lower.
[0] https://www.youtube.com/watch?v=r70Pt6roE0o
You can find over-specing in the US/CA as well because of rules of thumb, or installers just looking at what the old system was and replacing it 1:1 with the same new system—never mind that more insulation or better windows have been perhaps put in.
For new builds, a lot of jurisdictions are mandating standardized calculations be done for estimated energy needs, equipment selection, etc:
* https://mrcool.com/blog/understanding-calculations-for-manua...
If you're going to do a retrofit/replacement, it may be worth finding an HVAC company that will do that process for your non-new dwelling. The fact that a company could offer it may mean they're a step above Random Bob's HVAC.
And there are horror stories from there being too many poorly qualified green installers doing a half-job. Some systems wildly underperform. My octogenarian neighbour had no central heating for two weeks while a replacement pump motor could be sourced and somebody could be found to fit it. You wouldn't have that with gas.
Heat pumps are catching up —I want them to win, we need them to— but this stuff has to get better. Installing one should be certified, performance should be mandated to protect consumers and grant money.
That seems entirely like a lucrative insurance product that the market could offer. (Just like extended warranties for your electronics.)
I wonder if any actuary is working on it.
Pay for rental of propane heaters during a cold snap when they're all gone?
Insurance is not the answer here.
How is a certificate and a mandate that oliwarner suggested going to provide heat? Burning a certificate takes at most a few seconds.
To spell it out for you, the mechanism is pretty much the same as elsewhere:
Companies can offer customers some warranties that their system will work as advertised (ie provide heat with a minimum of fuel). Lots of companies in the private sector offer such warranties on a variety of products. The warranty by itself does not keep you warm, but it typically provides for some restitution in case of failure. (In an extreme case, you can imagine that people would be happy to be paid a million dollars in return for putting up without heat for two weeks. In practice, the warranty will probably settle on something less extreme. For example, some modest monetary compensation plus help with sourcing propane heaters as you suggest. Your imagination is the limit here.)
Because the small companies that do this kind of heat pump installation go bankrupt and disappear all the time, you can administer the warranty via a third party insurance company.
And here's where the certificates come in: just like some car insurance companies give you discounts in return for eg a clean driving record, you would imagine that your heat pump installation company would also be able to purchase much cheaper insurance to benefit their customers if they can provide evidence that they know what they are doing.
In practice the main benefit of the whole scheme would come from insurance companies keeping an eye on the installation companies. The payouts are mostly there to provide discipline and align incentives; but in a well running system the payouts shouldn't be necessary very often.
You can't just brush aside the way that actually works that easily.
When I was doing some extensive renovations of a house about 7 years ago now (in the UK), we called a company whose main business was to install heat pumps (along with underfloor heating, etc). The person asked me a bunch of questions, and based on the age of the house and the insulation and such, she said, "I appreciate what you're trying to do, but I'm really worried that a heat pump won't be able to heat your house sufficiently on cold days; I'd really recommend that you take the money you'd spend on a heat pump and spend it on better insulation for the house instead."
Given that's their main business, and that she was knowingly turning me away as a customer, I tend to give some credence to her assessment. At least it can't be due to a lack of understanding or bias.
Now that our house is better insulated, I might try again next time our boiler is up for replacement, particularly if I can arrange to get the heat pump to cool the floors in the summertime as well as heat them in the wintertime.
1. A system that also provides cooling isn’t allowed under the heat pump government grant.
2. You might actually need planning permission for this
3. Especially in a humid environment like the uk, you can end up with condensation and damp issues, which you really don’t want in an underfloor slab install
If you also want cooling, better to go an air-air based system (aka air conditioning)
The amount of cooling this way is limited. Though the nice thing is that it tends to keep the house cool. There is no cold airflow.
With respect to government grants. Sometimes you can buy units that can only heat to get the grant. But a simple change enables cooling after the unit is installed.
Might provide some benefits on really hot days, but it’s still uncomfortably warm for working in.
There is no reason to set all units to the same value in the entire country.
In general, if you want to save money, you should set your aircon to the highest temperature you can tolerate. We typically operate at 26-28C at home here in Singapore, and our dew point is typically between 24-26C.
The modest reduction in air temperature from 30-33C outside feels amplified, because the aircon also reduces humidity. We also rely heavily on ceiling fans.
That said, I'm guessing 22 (or 18 or whatever) is the lowest temperature you can have on the pipes; that wouldn't translate to 22 in the house.
If their working fluid is water, you are right. But most aircons work like fridges, and their pipes don't transport 'cold' by literally having a cold fluid, but by having an ambient temperature fluid that they turn into a gas inside your interior aircon unit (and then later turn back from a gas into a liquid on the outside unit).
The actual pipes are always at pretty much ambient temperatures.
You only end up with condensation issues, if you cool below the dew point.
Here in very humid Singapore our dew point is typically at about 24-26C. If you set your aircon to no less than 26C here, you never have any problems with condensation.
(Any old weather reporting website or app will tell the dew point. Apparently right now as I am writing this comments, it's 12C in London.)
How was that not an issue with coal/gas boilers? I don't know. Perhaps people just cranked up the gas and lived with the resulting bills.
People talk about needing larger radiators for heat pumps. You also needed similar sized radiators for condensing gas boilers to work at the claimed efficiency.
People were just burning 20% more gas for no good reason.
For heat pumps, 40 degrees is about the max for efficient operation. So radiators need to be quite a bit bigger compared to what you need for a condensing boiler.
So if a new system got installed and sized for running at 60, then it's losing 10-20 percent efficiency.
https://www.theheatinghub.co.uk/articles/turn-down-the-boile...
> The correct temperature setting for heating on a combi boiler is 'as low as possible', but as a guide most older homes can run their heating systems at 60°C and newer homes at 50-55°C. They start to reach their very highest efficiency potential at 45°C flow temperature or lower, but this can be too low for older properties.
> Ultimately how low you can turn your flow temperature down will depend on the size of your radiators, how well insulated your home is and your thermostat temperature.
....
> A vast skills and knowledge gap (that dates back to 2005 when condensing gas boilers become mandatory) means 99% of installers do not understand how condensing gas boilers work and therefore cannot set them up to run as they were designed to. Installers have been let down and so have UK households. We have simply not benefited as much as we should have from this leap forward in boiler efficiency.
If you go lower, efficiency may increase by tiny amounts, but in most practical setups the system is likely to become unstable and you will lose more than you gain. This is especially true if the system is also used to provide hot tap water. For hot tap water, in particular for a shower, the system needs to be able to heat a lot of water quickly.
> NB turning down your heating flow temperature is separate to setting your hot water temperature, but we cover that too - see section 11
Mom grew up on a farm in the 1950s in a big farm house that thing leaked air. It was so cold they used to put a heated brick in their beds to warm it before bedtime.
Air source heat pumps are at least 300% to 400% more efficient than just electrical resistance heat. Ground-source heat pumps are even more efficient.
All you do is use a bit of electricity to power a pump and some fluid to move heat around no need to burn things. Even better if the power comes from solar, wind, hydro, nuclear.
In contrast, if you have underfloor heating, you have a relatively large surface filled with warm water that heats up the floor. And then you have an even bigger surface that transfers heat to the rest of the house.
In the end the house is more easy to heat because it doesn't depend on an airflow to reach all parts the house.