/ Sustainability

Should we all change our home heating to save the planet?

Would you consider changing your heating system to help reduce carbon emissions? Should more help be available to do so? Our guest discusses the issues.

This is a guest post by Madeleine Gabriel/Nesta. All views expressed are her/its own and not necessarily shared by Which?.

A very loud clunking, and then an eerie silence. That was the sound of my old gas boiler breaking down two years ago. It had been on the blink for a while and after a few repairs, it finally conked out. It was February, and I was in no mood for cold showers, so I got straight online and ordered a new condensing boiler, which was fitted within a week. Relief!

In the frenzy to get my heating back on, it never once occurred to me that there might be alternatives to gas boilers – or even that it might just have been worth doing a bit of research before the old one gave up the ghost.

Like the vast majority of boiler-buyers, mine was an emergency purchase. But it’s one that has some big implications. 

That’s because in the UK, a whopping 15% of carbon emissions come from heating our homes – after transport, it’s the biggest source of emissions. But unlike flying or driving, most people aren’t aware that heating is a contributor to climate change.

Sustainable solutions

The good news is that low-carbon heating technologies do exist. Heat pumps are the most widespread of options currently on the market. These clever devices act like a refrigerator in reverse, taking heat from the air or the ground and turning it into usable heat in your home. They use some electricity to run, but are highly energy efficient when installed correctly. 

In some countries, such as Finland and Switzerland, heat pumps are already fairly common, but in the UK only around 25,000 are installed each year. The Climate Change Committee, which advises the government on how to meet the UK’s legally binding target to reach net zero emissions by 2050, thinks that this number will need to rise to over one million per year by 2030.

And that’s where the challenge gets pretty daunting. Nearly 85% of the UK’s homes – that’s about 24.5 million houses – have gas central heating. To reduce carbon emissions to net zero, almost all would need new heating systems at some point in the next 30 years. Gas boilers have a lifetime of around 15 years.

So for people like me who only think about changing their system when it breaks down, there will only be one or two opportunities in that period to install a more environmentally friendly system. And at the moment, heat pumps are much more expensive than gas boilers, although government schemes like the Renewable Heat Incentive have attempted to make the purchase more attractive for consumers.

Radical transformations

Can it really be done? And if so, how? That’s a question that the government and industry are grappling with at the moment. But it’s worth remembering that the UK’s houses have seen some pretty radical transformations before. 

Homes built before 1919 often lacked bathrooms and indoor toilets, and in the second half of the twentieth century there was a big push to improve housing quality.

In 1967, 25% of all UK houses still lacked at least one basic amenity (a bath or shower, an indoor WC, a wash hand basin, hot and cold water at three points). But by 1991, the proportion was down to just 1%, and there are virtually no houses today that don’t meet this standard. 

The charity I work for, Nesta, is setting out on a new programme of work to look at ways to reduce carbon emissions from the UK’s homes, so we’d love to know what you think.

Would you consider changing your heating system to help reduce carbon emissions? What do you think the government, industry and others should do to help? And what concerns would you have?

Tell us in the comments below.

This was a guest post by Madeleine Gabriel/Nesta. All views expressed were her/its own and not necessarily shared by Which?.


At the risk of sounding horribly patronising, it’s been heartwarming to find such an intelligent, well-informed, well-mannered and well-reasoned discussion here. Which? should be grateful for all the free input.

I have read most of the comments, which has taken up the bulk of an afternoon during which I should have been doing other things, but a sustainable future for domestic heating is a subject close to my heart, and one about which I have read quite a lot of nonsense in the press. I think there is an angle that has been almost absent from this discussion so far, although there has been mention of air management with heat recovery.

I am not an architect, but I was once married to one and have had many inspiring discussions with such. In my view, domestic new-build standards in the UK are woefully inadequate. We mostly know and accept that we should be using Scandi levels of insulation and we’re largely not doing so because it’s all about cost. However, there has been little mention of passive solar.

I’ve lived in a detached granite house in West Cornwall for the past two decades. My space heating comes – came – from a combination of electricity and bulk LPG, both of which have continually increased in cost. I am many miles away from any current or future gas grid. As a result of my membership of and inspiration by the Centre for Alternative Technology in Wales since the mid 1990s, over the time I’ve lived here I’ve incorporated solar HW, solar PV, improved insulation and DIY passive heat recovery: ‘eco-bling’, as one wag termed it.

The house had a 1980s integral south-facing (normally a no-no) timber conservatory that linked two parts of the ground floor. In the time I’ve lived here I’ve spent into five figures maintaining this structure, which in retrospect was a mistake. However, a couple of years ago I finally bit the bullet and had it rebuilt from the ground up to modern standards.

The result – for example, halving the amount of wood I burn each winter – has convinced me that wherever possible all new domestic housing design should incorporate fully insulated solar areas with bulk passive heat storage and active mechanical air handling with heat recovery. The advantages of this are manifold (no pun intended): minimal extra cost, free heat, more or less zero maintenance and a complete absence of technology that is likely to be beyond the understanding of your neighborhood plumber, let alone the householder: just fans, tubes and building mass. As a wise man once wrote, ‘systems fail, and complex systems fail in complex ways’, or something like that: simple is best, and it definitely does not have to be in Cornwall to work.

I’d be interested in what others here think.

I think if I lived in a granite house in Cornwall, a MVHR system would be my first priority to disperse all that radon gas.

Seriously, I am considering installing MVHR instead of all those stupid trickle ventilators that punch holes in my triple-glazed window frames. I’ve considered solar PV many times, but my first priority is to reduce my electricity consumption as much as possible, on or off grid.

I didn’t mention radon to avoid confusing the issue, but it’s well under control.

I looked at retrofit MVHR a long time ago, but at the time the idea of drilling 6″ ducts through 3′ granite did not appeal to me or anyone else (the house is a 1980s structure that entirely encloses a 19C cottage, hence the 3′ thick granite ‘internal’ walls). My simpler solution was to fit a good quality, variable speed fan between the conservatory and the living room, controlled by a differential thermostat. This worked well: the only challenge was persuading the electrician to wire up two mechanical thermostats in series, which he could not get his head around 🙂 (Lovely man, a Cockney in Cornwall, even though I have to explain almost everything to him, such as why it was a good idea to fit wireless thermostats to storage heaters.)

I forgot to mention PIV (positive input ventilation), as supported by Nuaire, Ventaxia and others. It’s a vital part of the mix. See for example https://www.nuaire.co.uk/knowledge/healthy-living-environment.

As an addenda to this thread, today it is a sunny mid-March day. The outside temperature is 12C, but the temperature of the granite internal wall in the conservatory, as measured with an infra-red thermometer, is 26C in the shade. The doors between the living room and the conservatory are open, and the living room is at 24C. This heat is percolating throughout the whole house, with no fossil fuel involved. The conservatory wall will still be warm this evening.

You seem to have it well under control Steve. It makes sense to make as much use of natural warmth as you can, even if you have cheap mains gas.

…which I don’t.

You did say. I was thinking about people like me. As soon as the conservatory is warm I open the door into the house. I use a wireless thermometer to keep an eye on the temperature.

Hello Steve,
If it’s not too late can you please explain what you mean by “fully insulated solar areas with bulk passive heat storage and active mechanical air handling with heat recovery.” Our south facing lounge can get to 24 degrees C in February at 12 noon with good sun while the north facing kitchen stays at 17 degrees C. Are you recommending that we install a fan to blow air from the lounge to the kitchen via a suitable tube?

Patrick Taylor says:
16 March 2021

Regarding the microwave heating. I have seen a different article which alluded to current military clients for the system. Secret of course.

I have no doubt that microwaves tuned specifically for water heating are possible. I would be impressed that they could be scaled up for a radiator heating system but it must be possible – though honestly why not go for radiant heaters and save the £3500 cost of the system. An butch instant water heater can deal with the demands for washing etc.

I make no mention of heatpumps as the target market is flats etc where a heat pump would be unlikely on an individual basis.

Gas is being phased out so all arguments of gas is cheaper are true but time limited.

Patrick, all microwave ovens work by using a microwave frequency that heats water molecules.

I believe this phenomenon was discovered during the development of microwave radar in WW2.

That’s right, microwave ovens work at 2.45 GHz which is the resonant frequency of water molecules and that causes the moisture in food to heat up as the water molecules vibrate and rub together and cause friction.

I read somewhere (in the 1970s) that it is possible to make an inside-out baked Alaska using a microwave. Normally, the ice cream is covered in meringue and baked in a hot oven. The insulating properties of meringue mean that the ice cream doesn’t melt in the time it takes to set and brown the meringue.

I assume the technique is to hollow out a tub of ice cream with a scoop, pack it with meringue mix and fashion a lid out of the ice cream, or just turn it up-side-down onto a microwave-safe serving dish.

Now microwave until the meringue is cooked inside for x minutes. (No idea how long x is. A probe thermometer would help. Maybe 5 minutes / 80+ degrees C?)

The physics behind this is that good quality ice cream contains fat, sugar and water in the form of ice. The meringue is mostly air, water and sugar, so cooks faster than the ice cream melts. If I was going to try this, I would probably use meringue cuite or Italian meringue to begin with, and just use the microwave to heat it up.

Sorry. I don’t want my microwave covered in exploding ice-cream and sticky meringue, so I’m not going to try it. But I expect someone here is desperate to amuse the children, or even adults with Covid cabin fever. Any takers?

One of the snags with this is that meringues don’t cook that well in a microwave and wouldn’t brown either. My experience is, that anything with sugar and fat in it, cooks really fast in a microwave and that would probably get at the ice-cream faster than the meringue it was hiding. You actually need a hot oven to get at the meringue quickly before the heat penetrates inside. You could, of course cook the meringue slowly for a number of hours and then add a dollop of ice-cream on top while it was still hot from the oven. I love Meringue and cream, but they don’t love me, so I’ll stick to scones (or “scons”) depending where you come from.

Unless we take action on climate change we really will have baked Alaska.

Patrick Taylor says:
20 March 2021

Talking of Alaska there is an article on heat pumps working fine in Alaska down to -40 . All a matter of design.

Indeed it is. A simple heat pump cannot achieve the necessary temperature difference so I assume that tandem heat pumps are used – two compressors effectively working in series.

Tandem compressors are used in -70 and -80°C freezers used in biological laboratories, again because a single compressor cannot do much better than a domestic freezer. These low temperature freezers been in the news because the Pfizer Covid vaccine must be stored at low temperature.

One thing that salesmen often don’t mention about condensing boilers is that that they can only run in their nice energy efficient condensing mode when they’re used with modern radiators which are designed to run at the lower temperature which a condensing boilers runs at and still adequately heat the home. But if such a boiler is used with older radiators made to delta T 55 or above then the boiler will have to be turned up and then it won’t condense and will burn like an older less efficient boiler.

Is there such a thing as an induction boiler? Induction seems to be ultra efficient at heating things on a stove top, why not use them for heating hot water elsewhere?

Ordinary (resistive) heating – for example with an electric kettle or immersion heater – is effectively 100% efficient. That will not be beaten and the claims for induction heating have a lot to do with marketing.

Hi Vynor, I think the short answer is no.

Stove top induction heating allows compatible saucepans to serve as electrical heating elements without any need to first plug the saucepans into the mains. This allows those saucepans to remain mobile.

I’d prefer to describe induction heating a very efficient but not ultra efficient because there there will be some energy wastage external to the saucepan, e.g. in the induction coils and their power supply.

If you want to heat a stationary hot water cylinder, there is no real need to keep it mobile, so it is more efficient to use a permanently connected heating element. If that element is at the centre of the cylinder, it will be most efficient at putting heat into the water. An ordinary electric kettle works the same way.

If you have both an induction hob and an electric kettle, you could compare their relative efficiency for boiling a given mass of water.

Many thanks for that. I think my hob is quicker than the kettle, but not by that much. Most elements that I know of (and that’s not many!) have a coil inside a metal shield which heats up and passes the heat through the shield and into the water. As you say, induction uses the pan base to do this for it. My question was really about the way the heating takes place, very much along the lines of the microwave comments above which discuss that method of heating water. I could see an induction system with an indirect hot water coil going through a cylinder or a metal plate between the induction magnet and the cylinder, that works as a pan base might. However I now understand that there is no benefit in doing this, so my theory is not proven in practice. Thanks again.

Your hob could well be faster than a kettle, Vynor. I noticed that some zones on induction hobs are rated at 3.7kW where as kettles are typically 3kW or less.

Why is everyone in such a hurry in the kitchen? Is it because of all these television programmes featuring cooks who seem to have to demonstrate their chopping and slicing speed? I can understand that a certain degree of despatch is required in a restaurant in case the customer gets fed up with waiting and leaves, but at home I don’t see that saving the odd few seconds is critical.

Some food preparation gadgets are good for doing certain things easier and with less effort or more accurately [if that’s important] but, in general, speed is not an issue. Putting just the right amount of water in the kettle is the simplest way to save some time.

The problem with immersion heaters is that they corrode, leak internally (RCD trips) or burn out. As the only source of hot water in my house, I need to change mine every five years or so. A stainless steel tank heated by an induction coil should last the life of the tank. But probably not worth the expense, even if I could find one.

Another snake oil solution to water heating is patented “Ohmic Array Technology”. In other words a bunch of electrodes that pass a current through the water to be heated. The resistance of the water itself causes it to heat up. Nice idea, except that the conductivity of water changes for a whole bunch of reasons, so it needs some sort of electronic control to adjust the current flowing. Plus maybe the risk of explosive oxygen/hydrogen gases forming?

I sometimes feel that a lot of these inventions are put out primarily to sucker in naive investors looking for the latest start up company. Just because an idea is new or novel, it doesn’t always make it better. But I guess I’d still be running a Newcomen engine rather than the new-fangled Watt’s patented separate condenser engine in my horseless carriage, if we all felt like me.

There are sheathed immersion heaters as one solution to the corrosion problem. I was shocked to see a YouTube video of a portable electric water heater for heating a cup of water.

Many years ago an immersion heater exploded – in the sense that it had progressively deformed in all dimensions – and stopped working. It took the technician at least half an hour to remove it from inside the tank without leaving any pieces behind. The twisted remains were badly corroded and caked in limescale.

One of my old showers also exploded and tripped the main fuse in the box. This happened because the element -7Kw was exposed to water when one of the components in the shower box began to leak. The result was startling and noisy. It led me to update my house with trip switches and a new box.. Now my showers are all worked from the boiler so there is no worry on that score, though my new, new box has been updated yet again to cope with the extra plug sockets round the house and the induction cooker.
There is a new gadget coming to market that consists of an induction “spot” on the work counter. One places a mug of water on it and then with the aid of a metal wand, placed in the cup, heats the water, milk or whatever within the cup. It’s called a “Heatle” I think. I don’t see much advantage of this over a kettle, and I think it will be quite expensive to install. There also seems to be a limit to the base thickness of the mug that can be used. Not for me, but I wish the inventers luck.

Tony Hanks says:
4 August 2021

Very interesting chain of comments above. have just signed up to Which as a bit of a “techy gadget type” with an interest in energy efficiency, and comfort !!!!!!
We have a solar panel array facing due South and generating above average predicted outputs – generating circa £2200 p.a. in cash into the bank on a monthly basis (we got in on the highest Feed in Tariff back in 2011) and still 15 years to go !!!!! Income pays for all gas electric and water bills to utility companies, and in the summer we run 2 air source heat pumps on warm bright days to keep working areas and main bedroom nice and cool at 18 C.
I am now looking to move to the next step and consider an electric combi boiler, allegedly an easy fit and removes the need flue vents and drainage tubes, that will easily continue to provide hot water and central heating to the existing radiator system. Does anyone have experience of electric combi boilers, as it would appear that in the next few years it will be the solution for many homes as gas boilers are phased out by legislation changes.
Also looking to install energy battery storage (10kW – 20kW capacity KSTAR system) in the near future to make better use of all generated energy and take advantage of the Octopus off-peak tariff of 5p/kW.
As with boilers, the pressure is also mounting on a change to electric cars, so the more power you can generate or buy cheaply and store, the better the return on investment whilst becoming even more green.
Finally, to supplement winter darkness and lower solar generation, there are some new vertical shaft roof mount wind turbines about to be released for domestic applications (AirTurb).
As the electricity distribution cable network and power station supply and demand gradually increases as we become more electric biased in an effort to reduce emissions and carbon there will be a need for upgrade in capacity, so becoming locally self sufficient helps everybody.
Welcome any comments and experiences on electric combi boilers, domestic battery storage, Octopus and domestic wind turbines.

Have you considered fitting a heat store? You are able to customise the tank (and avoid pumping hot water) by fitting a number (!) of immersion heaters as necessary. If you are into wood burning boiler stoves, you could also input heat from the stove, but make sure they are wood only for your 5%vat on the installation. You could input heat from Heat Pumps and solar too. What fun you could have!! Lots of info on line. Also requires investigation as to cost effectiveness on the various options. BTW, have never heard of electric combi boilers – seems an unnecessary complication?

You’re fortunate, Tony. We installed a £10k 3.5kw solar system with storage three years ago on a southeast aspect with no shading. The system was meant to provide a return of £600 pa but delivers barely £200.

My experience of electric combis is that you typically need the supply/master fuse upgraded, and they are costly to operate – unless you were an early adopter of solar.

Stanley Watkinson says:
23 August 2021

Don’t install Biomass we have now had this for 7 years and RHI payments are now coming to an end
Engineers are hard to find and well they now it. We had a breakdown in mid November phoned the ususal company Can’t come until January. There are no other engineers in Norfolk I had to get a firm from Lincs and boy don’t they charge. Callout, mileage twice there and back min 1 hour for engineer no parts carried have to order from S Ireland in EU When parts arrive same process milage time etc horrendous.
Unless you have a reliable engineer nearby don’t install.
Haulage contractors don’t like delivering and often the bags of pellets are split or pallets overturned on lorry.
Sorry we will go back to oil no gas in area and heat pumps not suitable for our house.

Encouraging people to install heat pumps in the UK is not the solution. Our properties were not built to accommodate such systems. To be efficient, the building needs to have been insulated to a far greater standard, more than is feasible in most UK homes. For example, as a minimum, a typical nine-inch solid brick wall would need 50mm of insulation applied inside and out to meet modern-day insulation standards. These systems only increase ambient temperatures by a few degrees, so you’ll need to supplement your heating with electric or other forms of additional heating when it is really cold. The cost is too prohibitive, and let’s face it Government isn’t going to pay!

There are now hydrogen ready combination boilers on the market that do not require homeowners to complete refurbishment. They simply change their boiler retaining their radiators or ducting, and, hopefully, install at least double glassing and insulate lofts, etc. Changing our gas supply to hydrogen is a far better solution.

Lets not try to scare people, but get them to look at realistic option, please!

Lallyrs says: “These systems only increase ambient temperatures by a few degrees, so you’ll need to supplement your heating with electric or other forms of additional heating when it is really cold.”

That’s a non seuqitur, rather like saying when it is really dark you need a 230V bulb rather than a 12V bulb. The amount of thermal energy a heating system can produce does not depend on the temperature alone.

Granted that, unlike a boiler, a single heat pump can only raise the temperature by about 35C, making a wet system unsuitable for use with existing radiators. But unless it is unusally cold for the UK (perhaps only a few days per year) a heat pump will be able to keep a home heated to a comfortable 20C. If that wasn’t the case a deep freezer (basically a heat pump in reverse), would struggle to hold -18C in a 20C kitchen.

And yes, you need good insulation for a heat pump to be viable and affordable.

As to insulation of a solid brick wall, I would not consider insulation both inside and out, nor is it necessary to do so. Firstly that would double the installation costs and increase the cost of the materials to no thermal benefit. Secondly, unless the exterior walls are in a particularly poor state, it would spoil the appearance of the property, plus you would need planning permission.

If you have a large Victorian property – without decorative plaster cornice – then a system such as Gyproc Thermaline PIR could be used on the interior face of external walls. A 93mm board will reduce the U value from 2.0 to about 0.25 – an 8x reduction in heat loss. It is also a good remedial treatment for damp.

Of course, this will reduce the size of the rooms, making it less suitable for a small terraced property. Thinner boards are available for smaller rooms, e.g. bathrooms where space might be at a premium. Even a 38mm Thermaline will reduce heat losses by more than 50%. The main obstacle is the cost and disruption, but if major renovation is taking place, it is well worth considering.

As you say, let’s not try to scare people, but do give them more options than do nothing until you can waste just as much hydrogen energy as you do on gas or oil.

I don’t expect hydrogen as a domestic heating fuel, either on its own or blended with natural gas, will be ready to supply all our heating needs for many years yet. Apart from changing the supply system to suit the different form of gas there is the question of hydrogen production capacity which will require massive capital investment.

I understand that the government is going to set up a trial village by 2025 where all the existing gas boilers and cookers will be replaced and the supply infrastructure reconfigured altered to provide the capacity and safety required. If that experiment shows sufficient promise then the government will set up a large-scale trial across a whole town by 2030.

A changeover of supply from natural gas to hydrogen cannot be done in small stages without duplicating the supply infrastructure; whole areas would have to be converted and switched over in one operation and that is logistically quite difficult. Hydrogen manufacture is an extremely energy-intensive process, and using the gas as a fuel will only make sense if it can be made using renewable electricity for electrolysis. On the plus side, hydrogen can be stored, so making it with surplus green energy when it is abundant can compensate for the periods when renewable energy sources are either overwhelmed by other demands or are absent as wind and solar power have been sometimes lately.

Huge additional wind turbine capacity is being installed off the UK shores over the next decade so attaining renewable energy self-sufficiency is not so far-fetched as was once thought, but its variable availability won’t change so having a beneficial use for the periodic surpluses should be worth while. Even if the energy production cost profile for hydrogen is high because of the storage requirement it will keep the overall average energy production cost reasonable, but finding an economic and efficient use for it will be challenging because it is not readily interchangeable with other sources.

I mentioned before that modern boilers can cope with a certain percentage (from memory between 10 and 15%) of hydrogen without modification. I met someone who told me about ongoing trials on different makes and models of domestic boilers. I don’t know how much renewable energy we will manage to produce but progress has been made since we first discussed this on Conversation. I don’t know how we will cope with the planned phase out of gas etc. and maybe we will not meet the deadline.

As we are heading for a ban on domestic gas heating and cooking we need to greatly increase generation capacity of the only alternative, electricity. We need even more to power electric vehicles when fossil-fuelled transport begins to be phased out.

I read that the energy efficiency in the conversion of water into hydrogen by electrolysis can be around 80%. So it looks sensible to make use of this fuel where possible to save a huge and costly replacement of our heating and cooking appliances. Most of us have wet central heating; many have gas cookers. Rather than scrap all these it seems to make sense to run them on hydrogen, even if it means a new or modified boiler and cooker.

Why continue with battery-powered cars, consuming scarce resources, heavy power packs, limited range when they could carry a tank of hydrogen to produce the electricity needed.

Whatever solutions we choose are going to need a very substantial increase in electrical generation. Wind and solar cannot do that alone, as well as being too unreliable. We need tidal and nuclear but, with the engineering and construction required, we need to start now. The cost is almost irrelevant if we are to have a sustainable future. Better to have spent the £130 billion being consumed by Cross Rail and HS2 on a far, far more worthwhile cause.

As well as the future electrical demand for the conversion of heating from oil and gas and for road transport, the further electrification of the railways in order to fully decarbonise them will add substantial demand. Hydrogen might be a practical way of decarbonising remote and rural railways where electrification would be prohibitively expensive for the traffic conveyed.

I had thought electrolysis to produce hydrogen would only be economically viable [and therefore efficient] if renewably generated electricity were used, the output being labelled ‘green hydrogen’. Nuclear power would be satisfactory but we barely have enough capacity for existing baseload purposes.

I think London’s Crossrail east-west connecting railway, mostly underground and costing £18.7 billion, will prove beneficial over time in relieving congestion on other transport modes being much faster between the limited number of stations. It is also opening up economic development opportunities in the east and west of the conurbation. It is built on a much more generous scale than previous lines and will add significant extra capacity.

The question arises, though, whether it would not have been better to spend the same amount on depopulating the capital by effective dispersal of commerce and industry, lowering the population density in many deprived areas, curtailing commuting all across the home counties and beyond, and creating more open space and a better overall amenity. It would thus not have been necessary to build a new railway and the carbon input would have been mainly into the improvement of living conditions rather than facilitating the concentration of wealth in one corner of the country.

Exactly John. Rather than aiding the longer distance commuting. We have to sort out our priorities and, as far as I can see, the one top of the list is to provide enough electricity for our needs. That requires a large amount of capital investment, people and time. As capital and people are in limited supply they need to be directed to where they will be most beneficial. Moving people at speed across country is less important than securing our future energy needs.

A disadvantage of heat pumps is that they are unable to raise the temperature very much, so replacing a conventional gas boiler would require larger radiators or underfloor heating.

The conventional freezer, in most homes, is a very familiar heat pump. It will achieve the recommended temperature of -18°C but to achieve lower temperatures it is necessary to use tandem compressors. That allows temperatures of -70°c or -80°C to be achieved and low temperature freezers are needed in laboratories and to store some of the coronavirus vaccines.

Perhaps tandem compressors (which use two refrigerants) could provide a practical solution for heat pumps in the home by allowing radiators to run at a more normal temperature.

I would be interested in input for anyone with relevant expertise.

Extracting heat from a poor source, is both expensive and reliant on complex machinery. There isn’t much extra to be garnered from the earth or the atmosphere and so, with the technology and refrigerants available, the results are tepid. Adding to the complexity by doubling the refrigerant and compressors just adds to the cost of extracting that heat, the chemical production of refrigerants and the additional power used to drive all this extra compression. This certainly isn’t free heat granted to us by nature. Capital costs of installing all this gear and increasing the heating area that each home needs to add to what is already there, means that, short of renovating every house at a huge cost to the householder, the new heating systems are useless. It would also be impractical to build local heat pump power plants and pipe the heat to everyone. It is bad enough installing fibre broadband, imagine the upheaval that would cause. I don’t see heat pumps as the way forward except in new buildings where they can be designed in. I’m not enthusiastic about electric boilers either. These just don’t have the thermal input of the current gas units and rely on heat storage rather than instant on demand water and warmth. I would accept these, and the increased cost of running them, to save the planet.

I don’t think there is likely to be a single solution, Vynor. Heat pumps are already in use to heat homes in the UK, and are most attractive where no mains gas is available. I’m interested in how two stage heat pumps could be used to raise the temperature of the circulating water in a radiator system to a higher temperature. As I said, two stage heat pumps are already in use in low temperature freezers, such as the ones we had at work. I recall seeing them in the news when the problem of storage of the Pfizer vaccine was in the news. Two stage heat pumps should be a reliable way of raising the temperature of water or air to a more useful temperature for heating.

Compressors in series to achieve a higher/lower output temperature will never be as thermally efficient as a single stage heat pump. It is necessary, of course, if your objective is to reach a design temperature of -70°C, almost irrespective of efficiency, as there are few other technologies available to do this.

The work of extracting the thermal energy from the air/ground/water source is all performed by the first stage compressor. The amount of energy available to the system (as measured in Joules) is now fixed. The second compressor can “upgrade” the energy from the first stage to a higher temperature, but cannot add calorific value, other than from the electrical energy used to drive the second compressor.

It is somewhat analogous to living off grid. What would you do if a generator could only deliver 110 VAC and your appliances were all 220 VAC? You could install a transformer or rotary converter, with the consequential power losses. There is no way to gain energy at this stage. The efficiency of the system is reduced. Or you could change your appliances to use 110 VAC. The efficiency of the system is maintained.

The problem is not with heat pump technology – it is how to adapt it to work with coal/oil/gas-fired Victorian heating systems. We no longer use petrol to run steam engines, we use the more efficient internal-combustion engine.

Daikin and other heat pump manufacturers recognise there is a problem with getting people to abandon their steam-age heating systems, and produce less efficient options that work with high temperature systems. Altherma comes in high temperature (HT – COP 3.5) and low temperature (LT – COP 4.5) forms.

Presumably they have done the maths and decided to stick with single compressors. The required HT system increase in temperature is achieved with resistive heating to boost the output water temperature up to 50-55°C. This is of course required for washing, but not space heating. Although the lower temperature is optimal for efficiency, the system automatically increases the temperature to 60°C at intervals to kill any bacteria, e.g. Legionnaires’ disease.

Personally, I can’t see why there is a problem – other than installation costs – with abandoning the existing radiator system and installing air handling units in each room. They are available as low or high level units and provide zoned temperature control. They can also be switched to cool in summer – which you cannot do with radiators. There is also the British aversion to blown-air heating systems commonly used in North America, not that they are paragons of energy saving.

“You can’t solve today’s problems with yesterday’s solutions” – Albert Einstein

The lack of a better alternative is indeed why freezers with two compressors to achieve temperatures of -70°C are used extensively in labs for biological research. Prior to their arrival we used solid carbon dioxide or liquid nitrogen for low temperature storage, the latter achieving much lower temperatures.

I was going on to make the point about the need to heat water to 60°C periodically to protect us from Legionnaires’ disease, but since you have mentioned it I agree with your points.

I do not know why blown air heating is not popular in homes in this country, though it is widely used in non-domestic HVAC applications. A friend of my parents had conventional radiators installed because she found the blown air heating noisy.

To date, heating systems based on heat pumps have been most attractive to those without mains gas, and there seems little doubt that they will become much more popular in preparation for the phase out of fossil fuels. My guess is that two stage heat pumps will have a place, even if they are the exception rather than the rule.

I do agree that we need to look to the future and that means helping more people understand what technology can achieve, the advantages and possible disadvantages. I look forward to Which? providing a supplement to the magazine that helps us understand current and future options for providing heating and hot water without gas. Rising gas prices, if sustained, will be an important factor.

From what I read the coefficient of performance of ground source heat pumps drops significantly as the output temperature is increased.

I wonder what future there is for geothermal from deep boreholes? I believe parts of the UK are suitable (Southampton has some heating from this source) but it has not been developed elsewhere due to cost. However, that balance is changing.

With ground source heat pumps, which have a steady state input temperature of 12°C as long as the coil is big enough, the CoP falls as the output temperature rises.

In the case of air source heat pumps, the outside temperature can be above or below freezing. As the outside air gets cooler, the CoP falls in an effort to maintain a constant internal temperature. At around -10°C, mine would become unviable as a source of heating, as not only does the CoP tend towards 1.0, but the condenser (evaporator in heat mode) coils spend a lot of time melting off the ice that forms, rather than keeping me warm. But as we are look for solutions to global warming, not cooling, I don’t anticipate a problem until the next ice age.

As to radiant heat, I have a couple of Daikin Nexura units which have been recessed into the wall cavities, so they are no more intrusive than standard radiators. They also have a radiant panel that heats up to over 40°C, to satisfy the reptilian members of my family, who are less concerned with efficiency. Everything in life is a compromise.

As to geothermal heating, why not? With their expertise in geology, deep-drilling and fracking, who better placed that the fossil fuel industry? Oh wait! I see a problem with that idea … . But if we weren’t so diverted and distracted by nonsensical hoax conspiracy theories and campaigners with dubious agendas, we might get an answer to why this isn’t happening.

Back in March 2021, Patrick Taylor wrote: “Gas is being phased out so all arguments of gas is cheaper are true but time limited.”

As of October 2021, we can simplify that statement to: “Gas is being phased out.”

Perhaps nuclear fusion will provide the clean energy source of the future. It seems unlikely that it will come soon enough to meet the deadlines for moving away from fossil fuels.

Conversion of existing housing stock to future technology will be in the thousands of pounds for each house. Every room will have to be changed and the heat source altered. How many millions of houses do we have? Each one with a different conversion challenge? How many builders and converters have we got? How long do we anticipate this will take? Who is going to pay for it all? With what? Replacing the heating source involves one room and one unit, leaving the rest of the house untouched. Even this is a major disruption and the shortage of kit and labour would drag this process out for a decade or two even if we started now -which we aren’t going to do. Someone has to produce a strategic, realistic plan to get from where we are to our gas free future. I haven’t seen anyone yet. Perhaps the government are working on it. Let’s ask Which? to send a letter to Boris to find out.

The major problem is with the mindset of owner-occupiers. Why would I spend thousands to upgrade my heating systems? I would rather have a new bathroom or kitchen and an exotic holiday. I suspect if everyone engaged on refitting kitchen and bathrooms, and servicing aircraft were redeployed, we could begin to make a start. They already have the necessary skills.

We always see this from industries impacted by environmental change. Remember all the fuss made by motor manufacturers about catalyctic converters?

The introduction of catalytic converters had to be preceded by the introduction of unleaded petrol because lead quickly destroys catalytic converters. Nowadays the concerns about catalytic converters are the expensive rare materials and the fact that some are easily stolen, but both unleaded petrol and catalytic converters were a worthwhile step forward.

I don’t see any point in an electric boiler except to make use of an existing wet radiator system. Why not just install electric panel radiators? Have I missed something?

Only the high cost of electricians to install the additional wiring. Otherwise, none.

A few years ago I attended a lecture at Oxford University re the future of nuclear power for domestic use, the main theme being the safe disposal of nuclear waste. At the time there was no definitive or satisfactory solution, although several proposals were discussed at length. I came away with the feeling, unless a solution could soon be found, it would delay any advancement in the use of nuclear energy to heat our homes.

Things have progressed since then and the following website provides some insight into plans to deal with the problem of Nuclear Waste Disposal. (GDF).

http://www.gov.uk – Geological Disposal – A Permanent Solution For The UK’s Higher Activity Radioactive Waste

Presently it is being stored above ground in areas scattered around the UK, but clearly, as our reliance upon nuclear energy becomes more urgent, underground storage seems to be the only safe place in which to dispose of it.

Let’s briefly examine the conversion process. Currently, each house has piping that sends hot water from a central source to the taps. Most, not all, have pipes that send hot water to radiators and under floor pipes. Those that have electric storage heaters still have hot water pipes for washing , showers and bathing. Off grid there is oil, Calor-gas. and solid fuel of one sort or another. That’s where we are at present. This means that we have to have a source of energy to heat water for domestic use and that has to be sufficient to prevent Legionnaires (marching in from France.) This limits the type of technology we can employ since hot air can only be used for room heating and a boiler is required for the rest.
We would probably have to remove radiators and leave the piping in place unless we want to demolish the house and rebuild it. These could be replaced by electric heaters which are expensive but have a tried and tested format in all electric homes. We could revert to a tank and an immersion heater for our water. Lo, we are back in the post war house and converted, probably at a cost of ten thousand pounds. No one is going to dig up the garden for a heat pump and few are going to put up with the noisy air unit needed to convert air to heat. These don’t have boilers attached so some kind of electric source is needed for the hot water and to supplement the air units.
Is there a third conversion out there using modern technology and easily fitted? If there is, perhaps someone can explain what that is and how it is installed without wrecking the property in the process.

As you say, we already have a solution to that, which is electric heating. The purpose of a heat pump is only to reduce the amount of electrical energy required and/or how much it costs to run. But if electricity is cheap, abundant and non-polluting then heat pumps are not required.

Nuclear fusion, if it ever happens, will avoid the need for heat pumps and other technical fixes. In the mean time, we have to find more sources of non-polluting power and/or make more efficient use of it. Wind and solar are a start. More hydroelectric too, either for storage or as a primary source. But if there hadn’t been so much resistance to nuclear fission power stations – presumably by people who were happy to continue burning fossil fuels – we wouldn’t be in this mess right now.

An alternative to Vynor’s outline of the conversion process is to adopt a strategic global solution whereby we close down the UK and transfer its population, in stages, to a Mediterranean location. Some countries are under-occupied and might welcome a supply of new labour.

Meanwhile the UK landmass could be used primarily for agricultural purposes with a small resident population and as an open prison and isolation facility. In the summer months it could act as a holiday resort, a museum and heritage centre, and a sports centre. Or we could sell or lease the UK to a Nordic nation for expansion in warmer conditions than at home.

This would avoid the huge carbon footprint of repurposing our homes and other buildings with new apparatus just to provide heat and the waste of embedded carbon involved in discarding the replaced material.

The migration to Spain was well underway, until Brextiers put a stop to that. So, basically your proposal amounts to reversing Brexit and extending the boarders of Scotland to the English Channel. Nicola will be pleased! But expecting other countries to welcome New Labour is just too far-fetched to be credible.

If we are serious about these proposals, then England, free of all NIMBYism, could also be populated with onshore wind turbines. I think you are on [to] something John! Maybe if Donald Trump was still in power, he could make us an offer.

One significant change in domestic heating was the ban on sale of coal and wet wood: https://www.gov.uk/government/news/government-takes-action-to-cut-pollution-from-household-burning

In urban areas, where air pollution is generally highest, multi-fuel stoves have become popular to provide a focal heat source in addition to central heating. Thanks to the ready availability of smokeless fuels these stoves can continue to be used.

I am an asthmatic and strongly affected by sulphur dioxide produced by burning coal. Although only one of my neighbours burned coal and usually only at the weekend, it has helped me that they stopped shortly after the government took action.

Electricity generation used to rely heavily on coal. Desulphurisation of exhaust gases from power stations greatly reduced pollution and the last coal fired power stations are due to close in 2024, though the remaining ones are often idle.

We can make progress.

Plan A, then, would be to make a dramatic increase in our generating capacity, electrify our houses and dismantle the gas production and pipe line system. It could be phased district by district. The government would employ a body of workers in each area to carry out the work and this would be paid for by an increase in taxation. The conversions would be mandatory and the loss of gas would make them necessary. This would be state intervention at a level unheard of and more akin to what our Russian neighbours have to put up with. Allow free enterprise to do the job and someone has to pay them. Consumers might decide not to cooperate until the threat to their gas supply became a reality. They then might not be forthcoming with the payment for the cost of the work. Instead of doing a street at a time the work would be all over the place.
Plan B would be for each householder to convert as they felt like it, employing tradesmen to do the job. Snags include the length of time for this to work, the shortage of labour for the work and the patchy nature of the plan even with the blackmail of a gas cut off date, which, inevitably, would be impossible to keep to.
The current Plan C is to set a target and talk about it in the hope that the population will do the right thing and convert their houses.
Something as big as this needs a national directive and a national programme or we shall miss our target and be in a worse mess than we are now. This isn’t like the smoking ban, no one is going to feel morally bound to act until they have to. Most will claim poverty if they are told to convert on their own.

As far as I know, no gas boilers will be installed in new homes from 2025 and it will be interesting to learn how builders will respond.

It’s only in the past few years electric bicycles have become very popular, and now we have e-scooters even though it is illegal to ride one on public roads unless it is part of one of the rental scheme. Few predicted this change, which has largely been possible thanks to advances in battery technology.

Planning can go awry. Grants used to be available for BEV and PHEV but the latter were withdrawn. One reason was that some business users took advantage of the grant but the drivers never charged them, so that people like yourself who behaved more responsibly lost out on a grant. Grants are still available towards the cost of charging points and no-one is likely to pay a contribution without intending to use the charger.

The government will learn a lot from what happens with new build homes that cannot have mains gas heating, which will also help the public.

”Plan A, then, would be to make a dramatic increase in our generating capacity, electrify our houses and dismantle the gas production and pipe line system.”.

Not necessarily. Use much of the abundant green electricity we must generate (certainly necessary for our comfortable future) to produce hydrogen. Hopefully the existing distribution system can be used or adapted to get it to houses and industry. Modified boilers and their systems and cookers can be used without huge disruption.

I sometimes wonder if the loss of hydrogen from the planet due to leakage will become an issue in centuries to come, or is there such an abundance of water we just don’t care?

Once released, hydrogen drifts off into outer space, never to be seen again. Will the extra oxygen find something else to partner up with, or will it lead to things becoming more flammable? I suppose it is one way to tackle the rising ocean levels and a lack of ventilators for Covid-19, but why can’t we just find sustainable solutions to our energy needs?

Agreed, Malcolm, but it doesn’t seem to be carrying much traction at present. It’s certainly an interesting alternative and the least disruptive to our domestic infrastructure. If it were introduced, someone needs to invent a way of adapting existing boilers so that they are not all thrown onto the scrap heap. I also wonder whether there has been enough research into the volitivity of Hydrogen and what happens to it inside a gas pipe line under pressure. How likely is it to explode in transit or in use? I would love to see Hydrogen cars being an alternative to battery ones, and mass production of Hydrogen for domestic use would help get Hydrogen to the garages if enough quantity could be produced for both uses.