Planning Permission for Air Source Heat Pumps

In planning law, the external heat exchanger/compressor unit of an air source heat pump is classed as a ‘temporary structure’ and in some circumstances, planning permission may be required before a new system is installed. This information explains the rules and when you may need to talk to the Local Planning Authority.

Generally, the siting of temporary structures within the boundary (curtilage) of a property (which includes the garden and other grounds around the main structure) is deemed “permitted development” and no specific permissions are required. However, in circumstances where the general permitted development rights have been removed through a planning condition, an Article 4 Direction or through other restrictions such as area designations, an application for planning permission is required.

So how do you know if planning permission is required?

Cornwall Council has an interactive map which shows many of the areas where permitted development rights have been removed (CCmap). (For an explanation about using the map’s layers click on the ‘I’ information symbol by the title.)

The map doesn’t show the specific planning conditions attached to individual properties which may also have removed permitted development rights: This is especially common where buildings have previously been extended or altered, or form part of a housing estate.

We are able to offer some general guidance and undertake a desktop study using Cornwall Council’s interactive map, but where there is any uncertainty as to whether or not planning permission is required, the interactive planning portal may offer further guidance (Interactive House – Planning Portal).

Specifically, Class G of The Town and Country Planning (General Permitted Development) (England) Order 2015 allows you to install, alter or replace an air source heat pump (ASHP) on a residential property BUT this is subject to limits and conditions as follows:

The ASHP must comply with the MCS Planning Standards (MCS is the Microgeneration Certification Scheme)

The ASHP can be installed on a dwellinghouse or block of flats provided that, if it is to be sited on the front wall, it is on the ground floor storey and not above.

It may be installed either on the building itself or within its curtilage.

Only one ASHP may be installed on any building or its curtilage unless the building is a detached dwellinghouse and a single ASHP would be insufficient to meet the building’s heat demand, in which case, a maximum of two ASHPs are allowed (this is a recent legislation development, applicable from 29 May 2025).

You may not install an ASHP if a wind turbine is installed on the same building or within its curtilage.

The volume of the ASHP’s outdoor compressor (including its housing) is limited to 0.6 cubic metres for flats, and 1.5 cubic meters for dwellinghouses.

The ASHP must not be sited on a pitched roof, but it can be sited on a flat roof, but not within 1 metre of the external edge of a flat roof.

For Listed Buildings and scheduled monuments, planning permission is required whether it is proposed the ASHP be sited on the building or its curtilage. Pre-application advice from your local conservation officer at Cornwall Council should be sought at the work proposal stage, and more information can be found here: Pre-application advice – Cornwall Council. Historic England also provide information and guides, which can be found here: Installing Heat Pumps in Historic Buildings | Historic England.

If the property is within a conservation area or World Heritage Site, as of 29 May 2025, the ASHP should not be installed on a wall or roof which fronts a highway, nor should it be sited nearer to a highway than any part of the house/flat.

The air source heat pump must be:

• Not solely used for the purpose of cooling.
• Removed as soon as reasonably possible when it is no longer needed.
• Sited, so far as is viable, to minimise its effect on the external appearance of the building and its effect on the amenity of the area.

When siting a heat pump, consideration must be given to the potential for noise impact on neighbouring properties and the operation of the heat pump must also:

Comply with permissible night period sound levels of 42dB(A); being 37 dB(A) for the ASHP, plus a nominal background sound level of 40 dB(A) (Review of Air Source Heat Pump Noise Emissions, Permitted Development Guidance and Regulations).

Until 29 May 2025, an ASHP could not be sited within one metre of a boundary, and whilst this requirement no longer exists, the installation must still comply with the noise regulations noted above.

If any of the conditions mentioned above cannot be met, then planning permission will be required.

Please note, obtaining planning permission (and Listed Building Consent) can be a lengthy process, so it is wise to consider the age and condition of your existing boiler and to obtain the required planning permission (which is valid for three years) before your current heating system stops working.

In all instances, the installation will need to comply with Building Regulations, and thus we recommend an MCS accredited installer undertake the work to ensure compliance.