A hot mess – the difficulties of decarbonising home heating
7 min read
Adam Bell, head of policy at Stonehaven, walks us through the perils and pitfalls in trying to decarbonise the heating of our homes
Early pioneers of heat pump deployment in the United Kingdom had a problem. The British public, who for 12,000 years have been used to coming home and burning things, found the hands-off approach to heating their homes that a heat pump involves difficult to master. Unlike gas boilers which can heat up a house very quickly, heat pumps add a small amount of heat into a house over an extended period of time and then keep topping up that heat to keep the people who live there warm. They are therefore best run on a timer so that they can ensure they have enough time to warm up a home to the desired temperature.
Heat pump installers were receiving repeated complaints that their devices weren’t working, and investigated what was going on. Frequently people who’d had a heat pump installed were ignoring the timer, and just switching it on when they needed it, and then getting upset when it didn’t make them warm. Scratching their heads for a solution, heat pump manufacturers removed the ability to manually switch the heat pump on and off and instead made the timer the only route for running the heat pump.
But the complaints did not cease. At one property the manufacturers visited, the customer had taken to going out into their garden and physically disconnecting and reconnecting the heat pump whenever they wanted the heat to come on. The manufacturers despaired of persuading the British public to give up their need to control their heating devices, until they came up with an ingenious solution. The Heat Boost button. This was a big red button installed on the inside of the property that, when pressed, switched a red light on and made a fan start whirring for at least 20 minutes. It didn’t actually do anything to the heating system, but it created the impression that the consumer was in control.
Consumers in properties with heat boost buttons reported considerably higher satisfaction with their heat pump, even though none of the physics of the system had actually changed. The feeling of being in control was significantly more important than the reality of their warm house, which had not changed.
Contemporary heat boost buttons do actually kick in an additional resistive heating circuit as the minor upgrade this offered to the heating experience was even more gratefully received by consumers, but this anecdote illustrates the perils of trying to engender a technological shift from Whitehall. We need to decarbonise our domestic heating supply, which for the overwhelming majority of us will be sourced from natural gas, which when burned produces carbon dioxide. Whitehall’s responsibility, through the new Department for Energy Security and Net Zero (DESNZ, pronounced “Disney”) is to figure out how to do this while having little to no direct connection with the consumer on the ground.
There are two primary routes for doing this, through electrifying heat or through decarbonising gas.
Because we’re decarbonising our electricity supply considerably faster than we’re decarbonising heat, then using electricity to provide heat means we decarbonise it too. Heat pumps, which use one unit of electricity to extract between two and a half to four units of heat from the environment and pump it into homes, are the technology of choice for this route. While older models did oblige householders to install bigger radiators and additional insulation, newer versions can output heat at about the same temperature as a condensing gas boiler, albeit at an efficiency penalty to a well-insulated home with a low temperature heat pump.
In an extremely 1960s move, the nationalised gas utility sought to assuage concerns by sending specially trained women into peoples’ homes
Shifting gas demand to electrical demand does come with some drawbacks. Heat demand heavily swings between seasons, meaning that in a wholly electric system there will be big chunks of our generation mix that primarily only run in the winter. At the micro level, low voltage electricity networks that carry power into our homes aren’t designed for the kind of additional load a heat pump represents, and will need to be reinforced.
There are various routes to decarbonise our gas supply. Natural gas equivalents can be synthesised from biomass but – short of giving up almost all of our pastoral land for feedstocks – biomethane and longer-chain biohydrocarbons cannot be produced in sufficient quantities to replace natural gas. Low-carbon hydrogen can be produced through either the electrolysis of water or through stripping the carbon from natural gas and pumping that carbon into stores under the North Sea. However hydrogen has different combustion characteristics to natural gas, and the majority of our existing appliances will not be able to safely burn it.
This means that a hydrogen roll-out will require engineers to visit every house in the country that uses natural gas and update their appliances. This sounds like a colossal undertaking but we have in fact done exactly this before: in the 1960s and 1970s the UK changed its erstwhile Town Gas (a mix of hydrogen, carbon monoxide and methane) network into a national natural gas network. This employed an army of over a 100,000 gas fitters who converted entire towns at a time. In an extremely 1960s move, the nationalised gas utility sought to assuage concerns by sending specially trained women into peoples’ homes to teach other women how cooking with natural gas was even better. This was how Mary Berry started her career, creating a direct link between the discovery of oil and gas in the North Sea and Iain Watters being booted from The Great British Bake Off.
The government is currently testing hydrogen conversion through a number of trials throughout the UK, but it’s safe to say that these trials have not been universally welcomed by the inhabitants of the places where the trials are to be conducted. There are significant local concerns around safety and cost. While hydrogen eliminates the risk of carbon monoxide poisoning by dint of not containing carbon, it is still a combustible gas being pumped into your home. Of course, so is natural gas, but hydrogen differs just enough (eg its nigglingly small molecule size means extremely small quantities of it can escape through metallic pipes) to cause people concern.
Heat pumps are more expensive upfront, are hard for consumers to understand and will require a great expansion of our electricity network and generation capacity. Hydrogen for heat will require natural gas as a feedstock to produce in sufficient quantities well into the future, has its own consumer acceptability challenges and will require a national conversion programme delivered by a range of private companies rather than a single nationalised entity.
It is perhaps unsurprising that when there is no clear winner the debate between these two solutions is extraordinarily fractious.
One option not adequately explored in existing policy is combining the two. The Netherlands, which is the only country in Europe to have a more extensive gas network than us, has recently mandated that all new heating appliances installed from 2026 must be at least hybrids; that is, a small heat pump plus a boiler. The heat pump handles 60-70 per cent of the heat needed, while the boiler handles the coldest days for which you would otherwise need a very large heat pump with a commensurately large electricity connection. These devices are currently excluded from the government’s Boiler Upgrade Scheme.
This aside, the debate between the two heat decarbonisation pathways will come to a head this year. The government’s Energy Bill contains provisions for a new heat policy that will require boiler suppliers to sell at least a percentage of their output as heat pumps each year, much like the electrical vehicle policy. This is a sensible approach by Whitehall, recognising that the people who talk directly to consumers are the ones best placed to figure out how to persuade them to buy something. But, because it will likely push up the cost of gas boilers as a proxy, it will be controversial. If it does not pass, and given that the government has no plan to roll out hydrogen, then our heat decarbonisation targets will be in trouble. After all, a target without a policy is like a heat boost button without a heat pump: it’ll make you feel good, but it won’t do anything
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