They gathered together on a sunny July evening, between the churchyard’s trees and leaning tombstones, to give thanks for the heat pump. Facing the newly installed system, in its large green metal box, they sang hymns and said prayers. “To thank God, really, for being able to work His wonders in mysterious ways,” says Karen Crowhurst, who is part of a committee that helps to run St. Mary’s Church in Lawford, Essex, in the United Kingdom.
The previous month, a flatbed truck carrying a hefty new heat pump system had eased itself onto the church grounds. By late July, the device was fully installed, and soon followed an outdoor thanksgiving service.
Parts of St. Mary’s date back to the 13th century. In more recent times, the building was heated by a wood chip boiler that had become expensive to run and sometimes clogged up. So now, after more than 800 years, St. Mary’s has gone electric. “We’re all very happy,” says Crowhurst. “We want to get through winter knowing that we’re going to have a nice warm church.”
Dozens of churches in Britain—commonly heated by oil or gas boilers—are currently in the process of installing electric-powered heat pumps as part of eco-minded retrofit projects. Many churchgoers view the schemes as acts of Christian stewardship.
“It’s about caring for other people,” says Kat Jones, from a committee that plans ecofriendly initiatives at the parish church in Milton of Campsie, a village north of Glasgow in Scotland. Many of those currently suffering the worst effects of climate change live in countries that are not responsible for the vast majority of emissions, she explains. Milton of Campsie’s new-build church has triple glazing and an air source heat pump.
And yet, it can be difficult to install heat pumps in older places of worship, which tend to be large, uninsulated buildings.
This, then, is the story of why some churches have opted to take a leap of faith toward this technology—and why it matters to them.
“I’m not one of these people that will glue myself to the road,” says Reverend Barry Knott, rector of the Lympne and Saltwood Benefice and area dean of Elham, Kent, referring to recent climate protests in the UK. “But I’m a great believer that resources are not infinite and therefore we have to manage them responsibly.”
For years, the Church of England (C of E) faced criticism over its oil and gas-related investments, until it divested from fossil fuels in 2023. Currently, the Church says it plans to reach net zero by 2030. That involves decarbonizing church heating systems.
According to C of E data shared with The Reengineer, in a 2024 survey of 12,337 churches (68 percent of the total number of C of E churches in the UK), 94 had air source heat pumps while 27 had ground source heat pumps. While many churches are opting for infrared heating devices, around 40 churches are currently in the process of acquiring some form of heat pump instead.
One of Knott’s churches, St. Stephen’s in Lympne, was a trailblazer. It is well known in heat pump circles as one of the oldest churches in the country—and possibly the world—to be warmed by a heat pump. Parts of the building date back to the 11th century. That’s young in the context of Lympne itself, though. “It’s a village where both the Saxons and the Romans came through, the Vikings came through,” says Knott.
And, back in 2008, a ground source heat pump company came through, too. Workers buried long lengths of pipe in the churchyard, to soak up some of the naturally present warmth in the ground.
Heat pumps harvest heat from the environment—the energy available in the air, even on a cold day, or in water or ground sources. Inside the heat pump, that warmth causes a refrigerant to evaporate. Compressing the refrigerant heats it further, and ultimately the heat gets blown into a room, or passed to a water-filled loop that connects to radiators or—in St. Stephen’s case—an underfloor heating system.
The crucial thing is that for every kilowatt hour of electricity this process consumes, heat pumps can produce multiple kilowatt hours of heat. The second number is represented by a figure called the coefficient of performance (COP). A COP higher than 3 is generally considered good. North of 5 is stunning.
Some churches are running heat pumps with COPs as high as 4. Though the number can vary across the year—weather conditions affect the devices’ performance, for example. It’s also important to remember that heat pumps tend to deliver water to radiators or emitting pipes slung below pews at lower temperatures than the fossil fuel or wood-burning boilers they replace.
“When it works, it is outstanding,” says Knott. But some of the St. Stephen’s pumps are in a damp basement, meaning they have occasionally rusted and seized up over time. “We’ve replaced one only in the last 12 months.”
Because of high electricity tariffs, St. Stephen’s is now planning to install solar panels to try to reduce running costs. Being such an old church, and Grade I listed—the highest classification of protection given to buildings of historical interest in the UK—this isn’t easy. Knott explains that he plans to place the panels in a valley-like section of the roof, and on top of the church’s tower, to avoid changing the overall appearance of the building.
St. Stephen’s has had a heat pump for nearly two decades. But not too far away, to the west of London in Egham, Surrey, is a church that switched on its heat pump system for the first time just two weeks ago. It provides space heating in the church—and is even connected to the baptism pool.
St John’s is a 200-year-old building of brick and stone. Installing pipework through the churchyard for the heat pumps, which are in a fenced enclosure nearby, was a painstaking process. “Everything was dug by hand,” says Patrick Wheeler, owner and director of VitoEnergy, which installed the system. The team found plenty of bone pieces—more than 400—though no complete skeletons, and ended up rerouting the trench in order to minimize disturbance.
“We had archaeologists supervising,” explains Chris Gray, a volunteer on green initiatives at the church. “You just rebury bones. It’s a churchyard, that’s what they’re there for.”
The new heat pumps use R290, or propane, as a refrigerant, which is an increasingly common choice. It allows the system to distribute slightly higher flow temperatures to the underfloor heating loop in the church without compromising much on efficiency. At present, those flow temperatures sit around 50 degrees Celsius (122 degrees Fahrenheit), heating the interior of the building to at least 18C. It’s too early to judge how well it’s performing, but a COP of roughly 3.6 should be feasible, says Wheeler.
And, he argues the project is instructive: “If we can do it with a 200-year-old stone church, then you can do any building in the UK.”
Gray reports that the response from the congregation has been positive. “I’m polling people. Is it comfortable? What do you think?” he says. That you can go green without compromising on comfort was, apparently, a surprise to some.
For very remote churches, a major hurdle to installing a heat pump could be the building’s power supply, says Graham Hendra, a heat pump expert who works for Haier HVAC Solutions. A medium-sized church might want to install an 80-kilowatt system, or so. But should a beefier electricity connection be required for that, then the cost could become prohibitive.
Occupancy is another consideration. If a church is only ever open for a few hours per week, for example for weekend services, then keeping a heat pump system running all the time may not make sense. However, many churches are used throughout the week—for community groups, sports clubs, and other events.
So long as power supplies and occupancy aren’t a concern, Hendra is bullish: “There is no reason why we can’t put a heat pump in every single church in the UK, including Westminster Abbey.”
In many churches, often strapped for cash, the switch to a heat pump may be borne from necessity. Staff at St. Peter Mancroft Church in Norwich, which already had solar panels, opted to make the jump to a heat pump system when one of their old gas boilers failed.
“The church decided this was a good time to try and commit to it,” says Nicholas Jackson, from architectural design firm Nicholas Vanburgh Ltd. Jackson is also a fabric officer for the church. Last year, two table-like, upward-facing air source heat pumps were installed in a small yard next to the 15th-century building. These connect to an Edwardian cast iron radiator system, and the heat pumps are currently running at a COP of 4.
The church also opted for a battery storage system. Jackson says he’s still unsure of exactly how the heat pumps will cope during a really cold spell—one gas boiler remains as a backup.
“We were very blessed to be one of the early adopters on some of this stuff,” says Reverend Edward Carter, the vicar. He adds that within the church is an “Earth Chapel,” intended to focus Christian minds on the importance of the environment. “We’re trying to say something to the City of Norwich here, and maybe to the wider world,” says Carter.
Churches are far from the only community-centric buildings in the UK currently reengineering how they do things. Village halls, covered markets, and public transport hubs are also, in some cases, putting in solar panels, LED lighting, and electric-powered heating systems.
For certain believers, though, the spiritual component of decarbonization is key. There’s something deeper at work here, and perhaps enthusiasm like this could accelerate society’s broader transition towards cleaner technologies. Knott’s opinion is that Christians should be motivated, by scripture itself, to look after the planet.
“We’re not jumping on the bandwagon,” he says. “This has been a message for 2,000 years.”
