I write from a garden office looking back at my Victorian mid-terrace house. At this time of year, that means I’m often cold—in fact I am currently looking through glass cross-hatched by ice crystals. I’m often struck by the fact that my home would have been warmer for the Victorians than it is some 140 years later. Every house in the row is topped by a chimney stack that today (mostly, and thankfully, for our lungs) emits no black smoke. But every main room and bedroom has a fireplace which would, for wealthier Victorians at least, have been fired up on a day like this, keeping the place blissfully snug. Our paltry hot water central heating systems do little in comparison. A Victorian time traveller would be astonished.
But a time traveller from 140 years in the future, from the year 2160, would be equally baffled by the white fumes belching out from every house—the flues from our gas boilers, heating the water that goes around our puny pipes. The gas boiler, commonplace since the UK capitalised on North Sea oil in the 1970s and 1980s, is now being phased out, and the puffs of white vapour will soon date this era as clearly as whale oil or coal gas did the past. But remarkably, what will replace it in our homes remains uncertain.
Most readers would be forgiven for thinking that the answer is clearcut. According to the independent Climate Change Committee, for the UK to meet its net zero target, half of all homes will need to be heated by a heat pump by 2040, and 80 per cent by 2050, compared to just 2 per cent today.
The Warm Homes Plan, which was published this week, gives further support for heat pumps through £2.7bn in grants for the Boiler Upgrade Scheme, and doubles the number heat pumps permitted on each property (from one to two).
Heat pumps are much more efficient than even a new A-rated gas boiler. The former are typically at least 300 per cent efficient, meaning that for every unit of energy used, you get three times as much heat back. The latter are 93 per cent efficient. This is because heat pumps use electricity to move existing heat from the outside air, or from the ground to inside your home, rather than to generate it. According to Jan Rosenow, professor of energy and climate policy at Oxford University, “Replacing an existing gas boiler in the UK with a heat pump would cut emissions by 77 to 86 per cent, including the embodied emissions from manufacturing the heat pump."
But there is another contender, already number one in other countries, that may yet play a significant role in the UK too. District heating, also known as a heat network, similarly combines hot water pipes and a heat source, but instead of serving just one house it heats an entire neighbourhood. The pipes run underground, much as existing gas or water networks do, and connect to individual buildings.
Such systems can deliver the same heat for “about 60 per cent of the total electricity demand than if everybody had their own heat pump,” Channa Karunaratne, district energy market sector lead at engineering firm AECOM, tells me. Even better, they can work with “waste heat” from industrial sources, like water treatment works or data centres. AECOM research finds that London’s data centres alone release enough waste heat for half a million homes. A network able to use this recovered heat would be 600 to 800 per cent efficient, says Karunaratne. Amazingly, such waste sources can easily reach temperatures of 80C, he says.
The benefits of district heating have long been known in climate circles—but it’s always been something that other countries did. In Copenhagen, Denmark, 99 per cent of heating is provided this way, compared to just 3 per cent of UK heat, largely in confined sites such as hospitals. But in the last couple of years, interest has been growing.
A resurgence of district heating in the UK began in 2016, led by what was then the Department of Energy and Climate Change, explains Karunaratne. “It was decided that heat networks were the “lowest regret”, which is to say the least worst, way of decarbonising heat… so they started feasibility studies across the nation.” The 2023 Energy Act then introduced heat as a separate utility, in addition to gas, water and electricity. Then in 2024, the Department for Energy Security and Net Zero (DESNZ) set a goal for heat networks to provide 20 per cent of total heat demand by 2050, and announced pilots with 28 English cities and towns.
“This incentivised the market to invest”, says Karunaratne. “Whereas before we were talking about small city centre schemes, we’re now talking borough-wide schemes—from £20m to £30m projects to £300m, £400m.” Large projects currently going through bidding and procurement include Greater Manchester, Leeds, Liverpool, the City of London, South Westminster, Plymouth and Stockport. The Warm Homes Plan announces a further uptick: £1.1bn of the £15bn plan will be set aside for heat networks, becoming “one of the fastest growing markets for heat networks in Europe”. It estimates that London and Manchester could be set to provide “over 50 per cent of heat demand” by district heating.
This has not gone down well in all quarters. The Telegraph briefly woke from its afternoon nap to splutter a “warning for Ed Miliband in Eastern Europe’s Soviet-era heating systems”, citing an ex-Soviet district heating system in Ukraine that briefly failed in (checks notes) 2006: “…if Eastern Europe’s experience is anything to go by, the plans risk coming back to haunt the Energy Secretary.” It’s not anything to go by. It’s like citing a bridge collapse 20 years ago as a warning not to build any new bridges.
However, the UK is already missing its heat pump target, even before considering heat networks. Only 98,000 heat pumps were installed in 2024; an uptick on 2023, but not on course to hit the targets set by the previous government to install 600,000 heat pumps a year by 2028—since downgraded by Labour’s warm Homes Plan to 450,000 a year by 2030. In November, an industry group warned that the “UK could miss heat pump targets by a decade”.
The spanner in the works is the combined cost and upheaval—a domestic heat pump is not a like-for-like replacement for a gas boiler, but typically requires totally new pipes, radiators, and an insulated hot water cylinder. The government’s own statistics show the average installation cost of a standard air source heat pump under its upgrade scheme is £12,500, leaving a typical householder to pay around £5,000 for installation even after receiving £7,500 in government support. If my boiler broke down, my local plumber could switch in a new one in a few hours, for a few hundred quid.
District heating, then, is a tantalising third option. Is it preferable to rip out the central heating and boilers of every home—or have utility pipes, as with gas pipes, that you just can tap into; and instead of thousands of heat pumps running, one big one? There would be some disruption, sure—but it would be akin to that already caused by utility companies when they install new internet cables or water pipes. (Lancaster University for example is installing an 8MW heatpump—roughly a thousand times more powerful than a domestic model—to cover its entire campus. Meanwhile MVV Energie in December unveiled a giant heat pump in Germany with a capacity of 82.5MW—enough to supply around 40,000 homes). The UK government estimates that such systems “could save billions for Great Britain in the long run.”
Speaking to me from his early 19th-century house on the outskirts of Brighton, however, Karunaratne admits that his own home, “is never going to connect to a heat network, because it's too out of the way. So a heat pump, for me, is the right thing to do. But if I was living in the centre of town in a high-rise development, I would totally expect, in time, to be connected to a heat network”. Proposals for a heat network in London already include a requirement for developers to connect to a heat network if there is one available. But this shouldn’t be considered only an urban solution. A village in Cambridgeshire, Swaffham Prior, installed a heat network for its 300 homes in 2022, providing 1.7MW of communal heat.
It’s exciting to think that a low carbon future (or the low carbon now, if you’ve got the money) will be heated by a combination of individual heat pumps, where the buildings are spread out, and district heating where buildings are tightly packed together—ideally linked to a data centre, or a factory. On a Reddit thread called “Solarpunk”—where users are united by their interests in “science fiction, social movements, engineering [and] style”—a user asked, “which is more solarpunk?”, district heating or heat pumps? Another, Tuneage4, replied, “Right now, absolutely heat pumps. They can be DIY, rapid rollout… But long term, I LOVE a district heating plan.” Maybe we all need to be more solarpunk.
