An air source heat pump works like a fridge in reverse. It pulls heat from the outside air - even in cold weather - compresses it, and delivers it to the building through radiators, fan convectors, or underfloor pipes. Because it moves heat rather than generating it, a well-installed system delivers two to three units of warmth for every unit of electricity it uses. That makes it significantly cheaper to run than direct electric heating.
The challenge for churches is the way heat pumps deliver warmth. They work best at low, steady temperatures over long periods. A church that is used for one hour on Sunday morning and left cold the rest of the week is the worst possible use case. The heat pump would need to run for many hours to bring a cold stone building up to a comfortable temperature, and much of that energy would be absorbed into the walls and floor rather than warming the congregation. Churches with more frequent use - daily services, a community cafe, office space - get far better value.
The external unit is another consideration. It needs to sit somewhere visible and accessible, and in a listed churchyard that means a faculty application. The unit produces a low hum, so placement near neighbours matters too. Inside, the existing radiators may need replacing with larger ones to work effectively at the lower flow temperatures a heat pump produces.
Grants can take the edge off the upfront cost. The Boiler Upgrade Scheme currently offers £7,500 toward an air source heat pump, and some dioceses have additional net-zero funding streams. If your church has regular use throughout the week and you are serious about decarbonisation, a heat pump is worth investigating. For a building used only on Sundays, the slow response time makes it a harder sell.