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The big cost is the upfront cost of insulation and removal the existing heating systems. Speaking about the UK (article is mostly about he US which will have t

The big cost is the upfront cost of insulation and removal the existing heating systems. Speaking about the UK (article is mostly about he US which will have their own problems), we have very poor quality housing stock with effectively zero insulation. You hold your hand to the exterior walls of your typical 2-3 bedroom terrace house (the most common type of home in the UK) in the winter and its just ice cold. For these homes the exterior wall are just solid brick and plaster with no air gaps. Many homes still don't have double glazing and their windows bleed even more heat. These homes go cold quickly when you turn off a gas boiler, and a heat pump just cannot keep up with the heat loss. In addition large numbers of households in the UK have migrated to "combiboilers" heating systems that dispensed with hot water tanks for on demand hot water from their gas boiler. In the process many of these properties have converted the space previously designated for hot water storage to loft extensions or other home upgrades. UK homes are pretty small, and going to a heat pump system means going back to hot water storage, which most UK homes have no space for without costly changes to the home layout/structure potentially including sacrificing parts of precious loft conversions. Frankly we might be better off just knocking down and rebuilding some of our housing stock at higher densities such is the cost of retrofitting and our housing shortages, but there is no political appetite in the UK for any radical solutions like that.

AniseAbyss 3y ago
In my country builders didn't seriously start to consider "insulation" until the 1990s. Gas was cheap so nobody cared. Just turn up that dial! Modern houses and apartments are marvels of engineering though.
pastage 3y ago
What is so special about insulation for heatpumps? You need that insulation anyways. EDIT: ok so the best interpretation I have is that it has just been so cheap with gas that people have not bothered insulating their houses.
- sandworm101 3y ago
  Heat pumps have a solid max heat output that cannot scale as easily as gas heating. So without insulation they can quickly hit a limit. The upper limit for gas system is limited by how much gas can flow through a pipe, which is a huge amount of energy. The upper limit for a heat pump aystem is set by the compressor capacity, which is in turn set by the electrical circuit, and relative temperatures.
- a_humean 3y ago
  Yes, gas has been so cheap, until recently, that nobody has invested into insulation, and our housing stock is so poor quality and small in average size that insulation has lots of detractions in terms of property appearance and internal area. The UK government back in 2010 actually had major plans for nation wide insulation, but famously the prime minster at the time, David Cameron, ordered the cutting of "the green crap" (widely reported to be his words) to help resolve some short term political problems with the budget in the early 2010s.
- sokoloff 3y ago
  A building’s heat loss (the rate of energy needing to be re-added to maintain thermal equilibrium) increases with decreasing outside temperatures and decreases with better insulation. A heat pump’s max output in heating mode decreases when the outside temperatures are low enough (whereas a gas boiler has a roughly constant max output and it’s quite inexpensive to size a wall-hung combi for 150K BTU/hr [44 kW] if needed). Buildings that are fine on the coldest design day with a gas boiler may need more output than a heat pump can provide on that day. Adding insulation can reduce this gap, which is why you’ll often find a heat pump project needs insulation, while a boiler replacement like-for-like would merely benefit from additional insulation.
- mmaurizi 3y ago
  The piece you're missing, beyond just "gas is cheap", is that increasing the heating capacity of a heat pump costs lots of money when installing it, whereas increasing the capacity of a gas boiler isn't much more expensive during installation, but costs loads more when running it. So technically it would be possible to install a heat pump with the same capacity as the existing gas boiler, but it would costs a ton more and it would all be upfront.
- nsteel 3y ago
  When operating efficiently, an ASHP's max flow temp is far lower than a gas boiler. Reducing heat loss is the solution.
- wizardwes 3y ago
  Another detail I think others might have missed, heat pumps need to defrost sometimes, during which time you effectively can't provide heat. In other words, you need to trust the house to be a good enough thermal battery so that you aren't having to continually heat it
DrScientist 3y ago
> Frankly we might be better off just knocking down and rebuilding some of our housing stock at higher densities such is the cost of retrofitting and our housing shortages, but there is no political appetite in the UK for any radical solutions like that Indeed. However a first step would be to put in decent building regs so that sub par new houses aren't being built! Still waiting for the new regs that were originally started in the planning back in 2006 or so.
- a_humean 3y ago
  The fact that new builds are still installing gas boilers and without ventilation systems in 2024 is insanity. A family member just bought a brand new flat that has a gas boiler in it with zero space for a hot water tank and no ventilation. A brand new flat that will need retrofitting within the next 10 years. I cannot find the source atm, but I recall that the government advice to builders is against installing ventilation systems to discourage retrofitting them in future for air conidtioning, which is makes it even harder to retrofit for heat pumps. Insanity!
  - pjc50 3y ago
    > government advice to builders is against installing ventilation systems to discourage retrofitting them in future for air conidtioning WTF? We're going to need air conditioning! We definitely need heat recovery ventilation if we're going to have proper insulation. Not to mention that it's starting to look like "minisplit" reverse aircon might be one of the more economical forms of heatpump.
    - rcxdude 3y ago
      Yeah, the gov is doing its best to discourage aircon. For example the subsidy on heat pumps can only be claimed if the heat pump can't act as aircon, which is just the problem the US has but in reverse.
    - a_humean 3y ago
      Their thinking is basically if we have mass aircon then our residential energy consumption will skyrocket. New purpose built offices and retail pretty much always have aircon though because they have obvious productivity benefits. However they also don't encourage passive cooling or low cost active solutions either such have making sure building have pass throughs for airflow, shading of windows, or fan systems. Government seems to be forgetting that current projections have us with Madrid style weather in the next 30 years and we will all be waving our fists.
michaelt 3y ago
> Speaking about the UK [...] we have very poor quality housing stock with effectively zero insulation. To expand upon this, consider an urban street like this: https://maps.app.goo.gl/A4HSZ2TFiJ2PyiAZ8 https://maps.app.goo.gl/A4HSZ2TFiJ2PyiAZ8 Beautiful houses with period features, in a great location. Big, traditional sash windows that let in loads of light. An L-shaped layout giving lots of natural light in all rooms. High ceilings. Market price about £2 million https://www.rightmove.co.uk/properties/139018139#/?channel=RES_BUY https://www.rightmove.co.uk/properties/139018139#/?channel=R... (admittedly being in London pushes prices up a lot - but the point is, these are desirable properties) The walls are all solid brick, no cavity and no insulation. The L shaped layout means a lot of external wall area, and the big windows don't help either. High ceilings make it even harder to heat. Many of these properties are prone to damp problems if they don't get enough fresh air circulating. You can't add external insulation without covering up the period features. Obviously you can insulate the loft and install double glazing - most of them will already have done so. It turns out nobody wants a £2000/year heating bill - but also, nobody wants to knock down and rebuild a £2M house over a £2000/year heating bill.
- a_humean 3y ago
  Exactly, that housing is super desirable by UK standards - probably amoung the most desirable housing in the UK. Pretty much all of those houses will have loft conversions (you can see the loft windows in the roof) made possible in part by removing their hot water tanks. The reality is that it is actually a bit shit. and would cost tens of thousands to retrofit. The compromises that the owners would have to make in terms of either apperance or internal area make heat pumps very unattractive.
  - soco 3y ago
    When you're sitting on a property valued at a couple millions, I would have thought investing tens of thousands in it would be fair game. Not pleasant, but acceptable...
    - a_humean 3y ago
throw0101d 3y ago
> You hold your hand to the exterior walls of your typical 2-3 bedroom terrace house (the most common type of home in the UK) in the winter and its just ice cold. The opposite is now becoming more true: with heat waves that seem to occur more often, you want to keep the heat out and the cold in in the summer.
- deleted 3y ago
  [deleted]
- BobaFloutist 3y ago
  I mean it doesn't matter that much, excluding sunshine insulation is insulation.
- masklinn 3y ago
  Thankfully insulation tends to work both ways, it keeps warmth in and out. One of my neighbours redid all the insulation of their house and lowered the high point of the south-facing living room by 10-15C (and made the house much easier to heat in the winter, they can now get by on just the fireplace). An other good option if you have the space (and money), especially with a south-facing living room, is to add a "sacrificial" sunroom (/ enclosed patio): at the cost of a bit of light, you get extra living space in spring and autumn, and the sunroom will insulate the living room in winter and summer (for the latter especially if it has an opaque roof e.g. tiling).
- a_humean 3y ago
  Yep, now our wall act as raidators in the summers - our homes do not cool down during heat waves because they are radaiting heat collected during the day.
dkjaudyeqooe 3y ago
I run a building with 5 apartments with central water based wood fire heating, ie a furnace and radiators in various rooms. It's brick construction with no insulation. It's absolutely stupidly constructed. The central heating is still there and used sometimes, but I installed mini-split reverse cycle air conditioners in each apartment and they work great, you just have to size them (power wise) correctly. They were 550-700 euros each installed. It's much much cheaper to pay for electricity than the equivalent amount of wood, even after the cost of the units. There are various additional benefits like being able to use the aircons when it's briefly cold, or you just want to warm up the space a bit. You also get cooling for no additional charge of course. Mini split systems are not always the best solution, but they are another useful option to be weighed against larger central heat pump systems. All depends on the situation, but heat pumps are the present and future, nothing else makes sense.
nsteel 3y ago
The bulk of the cost in the UK seems to be the actual unit. I don't understand why, other than boiler manufacturers trying to maintain the status quo (oversized boilers that can be badly installed by one of the many gas-safe "engineers" already out there). The split of cavity to solid walls is pretty even in the UK. There are gov grants available for insulation, both for walls and loft. It is true that many houses have moved to a combi-boiler and lost their hot water cylinder but cylinders are smaller than they used to be and personally I would guess the number of converted lofts in these cases is relatively small. https://www.checkatrade.com/blog/cost-guides/air-source-heat-pump-cost/ https://www.checkatrade.com/blog/cost-guides/air-source-heat... https://www.gov.uk/apply-great-british-insulation-scheme https://www.gov.uk/apply-great-british-insulation-scheme The main problem with an ASHP for your typical 2-3 bedroom terrace house is there is very limited outside space to put the thing.
usefulcat 3y ago
> UK homes are pretty small, and going to a heat pump system means going back to hot water storage Why not a tankless water heater? They are quite compact, and can be powered by gas or electricity. Are they just not really a thing in the UK?
- Symbiote 3y ago
  An electric heater is up to 100% efficient, the idea is to go beyond that with a heat pump — 200%, 300% or more.

AniseAbyss 3y ago

In my country builders didn't seriously start to consider "insulation" until the 1990s. Gas was cheap so nobody cared. Just turn up that dial! Modern houses and apartments are marvels of engineering though.

pastage 3y ago

What is so special about insulation for heatpumps? You need that insulation anyways. EDIT: ok so the best interpretation I have is that it has just been so cheap with gas that people have not bothered insulating their houses.

sandworm101 3y ago
Heat pumps have a solid max heat output that cannot scale as easily as gas heating. So without insulation they can quickly hit a limit. The upper limit for gas system is limited by how much gas can flow through a pipe, which is a huge amount of energy. The upper limit for a heat pump aystem is set by the compressor capacity, which is in turn set by the electrical circuit, and relative temperatures.
a_humean 3y ago
Yes, gas has been so cheap, until recently, that nobody has invested into insulation, and our housing stock is so poor quality and small in average size that insulation has lots of detractions in terms of property appearance and internal area. The UK government back in 2010 actually had major plans for nation wide insulation, but famously the prime minster at the time, David Cameron, ordered the cutting of "the green crap" (widely reported to be his words) to help resolve some short term political problems with the budget in the early 2010s.
sokoloff 3y ago
A building’s heat loss (the rate of energy needing to be re-added to maintain thermal equilibrium) increases with decreasing outside temperatures and decreases with better insulation. A heat pump’s max output in heating mode decreases when the outside temperatures are low enough (whereas a gas boiler has a roughly constant max output and it’s quite inexpensive to size a wall-hung combi for 150K BTU/hr [44 kW] if needed). Buildings that are fine on the coldest design day with a gas boiler may need more output than a heat pump can provide on that day. Adding insulation can reduce this gap, which is why you’ll often find a heat pump project needs insulation, while a boiler replacement like-for-like would merely benefit from additional insulation.
mmaurizi 3y ago
The piece you're missing, beyond just "gas is cheap", is that increasing the heating capacity of a heat pump costs lots of money when installing it, whereas increasing the capacity of a gas boiler isn't much more expensive during installation, but costs loads more when running it. So technically it would be possible to install a heat pump with the same capacity as the existing gas boiler, but it would costs a ton more and it would all be upfront.
nsteel 3y ago
When operating efficiently, an ASHP's max flow temp is far lower than a gas boiler. Reducing heat loss is the solution.
wizardwes 3y ago
Another detail I think others might have missed, heat pumps need to defrost sometimes, during which time you effectively can't provide heat. In other words, you need to trust the house to be a good enough thermal battery so that you aren't having to continually heat it

DrScientist 3y ago

> Frankly we might be better off just knocking down and rebuilding some of our housing stock at higher densities such is the cost of retrofitting and our housing shortages, but there is no political appetite in the UK for any radical solutions like that Indeed. However a first step would be to put in decent building regs so that sub par new houses aren't being built! Still waiting for the new regs that were originally started in the planning back in 2006 or so.

a_humean 3y ago
The fact that new builds are still installing gas boilers and without ventilation systems in 2024 is insanity. A family member just bought a brand new flat that has a gas boiler in it with zero space for a hot water tank and no ventilation. A brand new flat that will need retrofitting within the next 10 years. I cannot find the source atm, but I recall that the government advice to builders is against installing ventilation systems to discourage retrofitting them in future for air conidtioning, which is makes it even harder to retrofit for heat pumps. Insanity!
- pjc50 3y ago
  > government advice to builders is against installing ventilation systems to discourage retrofitting them in future for air conidtioning WTF? We're going to need air conditioning! We definitely need heat recovery ventilation if we're going to have proper insulation. Not to mention that it's starting to look like "minisplit" reverse aircon might be one of the more economical forms of heatpump.
  - rcxdude 3y ago
    Yeah, the gov is doing its best to discourage aircon. For example the subsidy on heat pumps can only be claimed if the heat pump can't act as aircon, which is just the problem the US has but in reverse.
  - a_humean 3y ago
    Their thinking is basically if we have mass aircon then our residential energy consumption will skyrocket. New purpose built offices and retail pretty much always have aircon though because they have obvious productivity benefits. However they also don't encourage passive cooling or low cost active solutions either such have making sure building have pass throughs for airflow, shading of windows, or fan systems. Government seems to be forgetting that current projections have us with Madrid style weather in the next 30 years and we will all be waving our fists.

michaelt 3y ago

> Speaking about the UK [...] we have very poor quality housing stock with effectively zero insulation. To expand upon this, consider an urban street like this: https://maps.app.goo.gl/A4HSZ2TFiJ2PyiAZ8 https://maps.app.goo.gl/A4HSZ2TFiJ2PyiAZ8 Beautiful houses with period features, in a great location. Big, traditional sash windows that let in loads of light. An L-shaped layout giving lots of natural light in all rooms. High ceilings. Market price about £2 million https://www.rightmove.co.uk/properties/139018139#/?channel=RES_BUY https://www.rightmove.co.uk/properties/139018139#/?channel=R... (admittedly being in London pushes prices up a lot - but the point is, these are desirable properties) The walls are all solid brick, no cavity and no insulation. The L shaped layout means a lot of external wall area, and the big windows don't help either. High ceilings make it even harder to heat. Many of these properties are prone to damp problems if they don't get enough fresh air circulating. You can't add external insulation without covering up the period features. Obviously you can insulate the loft and install double glazing - most of them will already have done so. It turns out nobody wants a £2000/year heating bill - but also, nobody wants to knock down and rebuild a £2M house over a £2000/year heating bill.

a_humean 3y ago
Exactly, that housing is super desirable by UK standards - probably amoung the most desirable housing in the UK. Pretty much all of those houses will have loft conversions (you can see the loft windows in the roof) made possible in part by removing their hot water tanks. The reality is that it is actually a bit shit. and would cost tens of thousands to retrofit. The compromises that the owners would have to make in terms of either apperance or internal area make heat pumps very unattractive.
- soco 3y ago
  When you're sitting on a property valued at a couple millions, I would have thought investing tens of thousands in it would be fair game. Not pleasant, but acceptable...
  - a_humean 3y ago

throw0101d 3y ago

> You hold your hand to the exterior walls of your typical 2-3 bedroom terrace house (the most common type of home in the UK) in the winter and its just ice cold. The opposite is now becoming more true: with heat waves that seem to occur more often, you want to keep the heat out and the cold in in the summer.

deleted 3y ago
[deleted]
BobaFloutist 3y ago
I mean it doesn't matter that much, excluding sunshine insulation is insulation.
masklinn 3y ago
Thankfully insulation tends to work both ways, it keeps warmth in and out. One of my neighbours redid all the insulation of their house and lowered the high point of the south-facing living room by 10-15C (and made the house much easier to heat in the winter, they can now get by on just the fireplace). An other good option if you have the space (and money), especially with a south-facing living room, is to add a "sacrificial" sunroom (/ enclosed patio): at the cost of a bit of light, you get extra living space in spring and autumn, and the sunroom will insulate the living room in winter and summer (for the latter especially if it has an opaque roof e.g. tiling).
a_humean 3y ago
Yep, now our wall act as raidators in the summers - our homes do not cool down during heat waves because they are radaiting heat collected during the day.

dkjaudyeqooe 3y ago

I run a building with 5 apartments with central water based wood fire heating, ie a furnace and radiators in various rooms. It's brick construction with no insulation. It's absolutely stupidly constructed. The central heating is still there and used sometimes, but I installed mini-split reverse cycle air conditioners in each apartment and they work great, you just have to size them (power wise) correctly. They were 550-700 euros each installed. It's much much cheaper to pay for electricity than the equivalent amount of wood, even after the cost of the units. There are various additional benefits like being able to use the aircons when it's briefly cold, or you just want to warm up the space a bit. You also get cooling for no additional charge of course. Mini split systems are not always the best solution, but they are another useful option to be weighed against larger central heat pump systems. All depends on the situation, but heat pumps are the present and future, nothing else makes sense.

nsteel 3y ago

The bulk of the cost in the UK seems to be the actual unit. I don't understand why, other than boiler manufacturers trying to maintain the status quo (oversized boilers that can be badly installed by one of the many gas-safe "engineers" already out there). The split of cavity to solid walls is pretty even in the UK. There are gov grants available for insulation, both for walls and loft. It is true that many houses have moved to a combi-boiler and lost their hot water cylinder but cylinders are smaller than they used to be and personally I would guess the number of converted lofts in these cases is relatively small. https://www.checkatrade.com/blog/cost-guides/air-source-heat-pump-cost/ https://www.checkatrade.com/blog/cost-guides/air-source-heat... https://www.gov.uk/apply-great-british-insulation-scheme https://www.gov.uk/apply-great-british-insulation-scheme The main problem with an ASHP for your typical 2-3 bedroom terrace house is there is very limited outside space to put the thing.

usefulcat 3y ago

> UK homes are pretty small, and going to a heat pump system means going back to hot water storage Why not a tankless water heater? They are quite compact, and can be powered by gas or electricity. Are they just not really a thing in the UK?

Symbiote 3y ago
An electric heater is up to 100% efficient, the idea is to go beyond that with a heat pump — 200%, 300% or more.