/ 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.