An air source heat pump installation by Architecture for London.
While gas central heating systems are enclosed within the building, an air source heat pump (ASHP) – the most common type of heat pump in the UK – needs an external unit mounted on the building or in the garden. As a result, a common question homeowners ask is whether they require planning permission.
New legislation brought in on 29 May 2025 now makes it easier to install a heat pump without planning permission. Before the rule change, it was more difficult to meet permitted development (PD) guidance – nationwide planning legislation that allows certain types of development to be carried out without planning permission –particularly in built-up areas, due to restrictions on where you could locate the unit and noise levels.
Further, air-to-air (A2A) heat pumps – a type of ASHP that can heat and cool the air, previously classified as air conditioning and growing in popularity – are now included in the latest permitted development legislation.
However, certain rules still apply, so if you’re considering one of these heat pumps, read our 3-step guide to understand what might be feasible for your home without going through the full planning process.
For more information on the different types of heat pumps, see our articles below.
READ:
Retrofitting Heat Pumps Into Houses: A Comprehensive Guide to the Pros & Cons
First, check if your property has PD rights. Class G of the General Permitted Development Order (GPDO) covers the installation of ASHPs and applies to most homes, including houses and flats.
PD rights apply to most homes, however, if you live on Article 2(3) land – such as a Conservation Area, National Park, Area of Outstanding Natural Beauty (AONB), the Broads, or a World Heritage Site – additional planning controls, known as Article 4 Directions, may apply. You will need to check with your local authority to see if there are any restrictions on your property.
There are specific PD rights governing ASHPs in Conservation Areas and World Heritage Sites – more on these below. However, there are no particular rules for AONBs, National Parks, or the Broads.
PD rights do not apply to listed buildings. If your property is listed, you will need to apply for Listed Building Consent to install an ASHP.
If PD rights apply, the next step is to engage a Microgeneration Certification Scheme (MCS) regulated installer. They will conduct a survey of your property, design the heat pump system to suit your building’s requirements – because heat pump installations are not one-size-fits-all and must be tailored specifically to each property – and assess the noise impact on neighbouring properties.
Meeting MCS Planning Standards is also a pre-condition to qualify for the Boiler Upgrade Scheme (BUS). Note that while Air-to-Air (A2A) heat pumps now fall under permitted development, they still do not qualify for the BUS. Air-to-Water (A2W) heat pumps are the only type of air source heat pump (ASHP) currently eligible for government grants.
With regard to noise, previously, heat pumps had to be at least 1 metre away from boundaries, with a noise limit of 42 dB(A), which helped reduce noise impact by distance. Now, the boundary rule doesn’t apply, but the noise limit is reduced to 37 dB(A) to offset the closer proximity doesn’t cause disturbance to neighbours.
The 37 dB(A) noise level is measured 1 metre from the centre of a neighbour’s window serving a habitable room (except bathroom and kitchen windows). This is known as the ‘assessment point’. The location of the ASHP in relation to neighbouring windows, or assessment points, depends on several factors:
In an ideal scenario you want to install a quiet unit, against a single wall and out of view from neighbouring windows to reduce the impact on the surroundings. Fitting standard unit close to multiple hard, reflective surfaces – say in a light well – adjacent to a neighbouring property may prove problematic.
MCS Planning Standards state that the noise level of an air source heat pump cannot exceed 37dB when measured 1 metre away from a neighbouring habitable window, known as the assessment point.
To install an air source heat pump (ASHP) without planning permission in England, you must comply with the conditions set out under Class G of the Town and Country Planning (General Permitted Development) Order.
Class G Requirements for England
Conservation Areas and World Heritage Sites (England)
If your property is in a Conservation Area or World Heritage Site (and there are no Article 4 Directions restricting installation):
Other Parts of the UK
Scotland and Northern Ireland:
Wales:
Permitted development rules for air source heat pumps (view of house from the rear).
Ground source heat pumps (GSHPs) are classed as permitted development. However, planning permission may be needed for excavation works on sites of special scientific interest (SSSI) or in archaeologically sensitive areas. In Northern Ireland, PD rules specify that no part of a GSHP can be within 3 metres of a boundary, and the external unit must not exceed 4 metres in height.
Water source heat pumps (WSHPs) also qualify under PD rights, but a licence from the Environment Agency may be required before installation.
While the changes to legislation and in particular the relaxation of the boundary setback rule can make it easier to install an ASHP without planning permission, complying with the revised noise requirements can still be difficult in certain situations in built-up areas.
For example, a terrace house with a small back yard where the arrangement of the existing rear walls create multiple reflective surfaces and the proximity to neighbouring windows make it difficult to position the outdoor unit out of view (which necessitates stricter measures) will pose challenges.
If these instances, engaging an experienced MCS-certified installer early on to carefully considering the available options is crucial.
When a certified installer manages your ASHP installation, they will ensure that the system complies with MCS and PD rules – including size, location, and noise limits.
However, for extra reassurance, you can seek confirmation from your local authority by applying for a Lawful Development Certificate (LDC) separately.
If your LDC application is deemed ‘lawful’, you can proceed with confidence knowing that your plans comply with guidelines. If it is deemed ‘unlawful’, the local authority will detail where your proposals are non-compliant, and you can then modify the proposed installation design.
The information provided in this article is intended for general guidance and educational purposes only. At Designs in Detail, we advise you appoint a skilled residential architect to provide specific expert advice for your project.
About the author
Aron Coates is an architect with over two decades of experience, encompassing projects ranging from the restoration of historic buildings to the design of contemporary homes.
