What the trial found
The Electrification of Heat Demonstration Project, funded by the government and run by Energy Systems Catapult, installed heat pumps in 742 homes chosen to cover the range of British housing: terraces and detached houses, flats and bungalows, homes of every age. Its 2021 finding was direct: there is no property type or architectural era that is unsuitable for a heat pump (December 2021).
The later analysis of performance data (December 2024) adds detail. 22% of the installations were in homes built before 1945, and the project found no significant difference in air source heat pump performance by house type or age. Most households were satisfied: 85% said they were likely to recommend a heat pump after one heating season. The same report is honest about the gap between design and reality: in 91.9% of homes the measured efficiency was below the designed figure. That is a design and commissioning problem, not a house-type one, and it is the reason to insist on a proper survey.
So the better question is not “is my house suitable?” but “what would it take in my house?” The answer falls into three practical limits and one set of grant rules.
No room for an outdoor unit
An air source heat pump needs an outdoor unit with free air around it, and a route for the pipes into the house. Most houses have somewhere: a side return, a rear wall, a corner of the garden. The hard cases are homes with no outside space of their own, such as many upper-floor flats and some mid-terraces that open straight onto the pavement at the front and a shared yard at the back.
Even then there are options. A unit can go on a flat roof or a balcony if the building allows it, and in a block of flats the freeholder’s permission usually decides the matter. Where there is truly no outside position, a ground source system with a shared loop, or simply a different heating choice, may be the honest answer. The heat pumps for flats and terraces guide works through the positions.
Planning and noise
In England an air source heat pump on a house is normally permitted development under Class G, within limits: an outdoor unit of up to 1.5 cubic metres on a house (0.6 cubic metres on a flat), 1 unit (2 on a detached house), not on a pitched roof, not within 1 metre of the edge of a flat roof, and compliant with the MCS planning standard, which includes a noise calculation at the nearest neighbour. In a conservation area or World Heritage Site the unit cannot go on a wall or roof that faces a highway.
When the position fails one of those tests, it does not make the house unsuitable; it means a planning application. The trial gives a sense of scale: in 5% of its properties the unit could not meet the permitted development noise criteria. Listed buildings need listed building consent for external works. Heat pump planning permission covers each case, and heat pump noise explains the sound calculation.
Radiators, pipes and cylinders
A heat pump runs at a lower water temperature than a boiler, so it needs enough radiator surface to heat each room at that temperature. Older homes and small radiators mean more radiators to change; that is a cost line in the quote, not a reason to rule the house out. Narrow microbore pipework may need replacing on some runs. Most systems also need a hot water cylinder, so a house that has removed its airing cupboard has to find space for one.
Insulation helps: a home that holds its heat needs a smaller, cheaper system and costs less to run. But it is no longer a condition of the grant. The insulation condition was removed on 8 May 2024, and the requirement for a valid EPC was removed from 28 April 2026. The insulation guide explains when it is worth doing first.
Homes the grant does not cover
A home can be perfectly suitable for a heat pump and still fall outside the Boiler Upgrade Scheme. GOV.UK lists the exclusions:
- Social housing, including shared ownership, cannot receive the grant.
- Most new builds still being built by a developer are excluded. A finished new build you moved into with a fossil fuel boiler may qualify, and self-builds can qualify for a heat pump.
- Homes already funded for a heat pump or biomass boiler by government, and homes replacing an existing low-carbon system.
- Hybrid systems. A heat pump working alongside a gas or oil boiler is not funded.
- Homes outside England and Wales. The scheme does not run in Scotland or Northern Ireland; GOV.UK says Northern Ireland’s Boiler Replacement Scheme is closed.
Tenants cannot apply, because the grant goes with ownership, but a landlord can use it for a rented home. The full rules, including the £9,000 band for off-gas oil and LPG homes, are on Boiler Upgrade Scheme eligibility, and the checker there gives an indicative answer in six questions.
How to check your own home
- Find a position. Walk round the outside and note two or three places a unit about the size of a large suitcase could go, with free air around it and a route for pipes.
- Check the planning flags. Is the house listed, or in a conservation area? Is the position on a wall facing the road? If yes to any, expect a planning conversation.
- Count the radiators and find the cylinder space. Note any rooms that are hard to heat now.
- Check the grant. Do you own it, is it in England or Wales, and what heats it now?
- Get a survey. Only a room-by-room heat-loss calculation by an MCS-certified installer settles the design. Get more than one, and compare them using the quotes checklist.