When making any significant changes to a property, it is important to know whether or not planning permission is required. Here, we explain why most Grant heat pump installations do not need planning permission and while this blog is primarily aimed for installers and specifiers, the content will also be of interest to homeowners.
Permitted development rights for heat pumps
In the majority of cases, planning permission does not need to be obtained for installing an air source heat pump. This is because the installation of an air source heat pump is considered permitted development if certain conditions are met. In Section G of the Town and Country Planning (General Permitted Development) (Amendment) (England) Order 2025, there are a set of criteria that must be fulfilled and while the list may appear long, many properties will meet these conditions.
New permitted development rights
On 29th May 2025, new permitted development rights were introduced in England as part of the Government’s Warm Homes Plan. The changes mean that less restrictions are in place for low carbon heat pump installations as a result of broadening the scope of permitted developments rights. The key changes include:
- 1m boundary restriction removed – effective from 29th May 2025, a heat pump can be installed within 1m of the boundary of the curtilage of a detached dwellinghouse under permitted development
- Heat pump cubic size increased – effective from 29th May 2025, larger heat pump units up to 1.5 cubic meters can be installed on or within the curtilage of a dwellinghouse without planning permission
- Noise limits set by MCS Planning Standards MCS 020 a) – heat pump installations completed under permitted development must comply with the noise limits outlined in the MCS Planning Standards MCS 020 a) (Air Source Heat Pump Sound Calculation (for Permitted Development Installations)).
Heat pump location, siting and listed properties
With air source heat pumps being external units, it goes without saying that much thought and care should be taken when deciding where to position the unit. Not only should the heat pump be sited so as to maximise its performance but other factors need to be considered, some of which may determine whether or not an installation falls within permitted development.
While the changes introduced in May 2025 have made installing heat pumps easier by reducing restrictions, there are instances whereby planning permission will be needed and these include:
- If a heat pump is being installed at a listed building or on a site designated as a scheduled monument
- If more than one heat pump is being installed on or within the curtilage of a dwelling which is not detached or is a block of flats
- If more than two heat pumps are installed on or within the curtilage of a detached dwelling
- If a heat pump is being installed on a flat roof within 1m of the external edge of the roof or on a pitched roof.
There are other conditions, including those which specifically relate to properties within conservation areas or World Heritage Sites, so there are certain circumstances whereby planning permission will be required. As mentioned above, it is also worth noting that if more than one air source heat pump is being installed on anything other than a detached house, or a heat pump and a wind turbine are being installed on the same building, planning permission is needed.
However, for a typical home looking to reduce its carbon footprint, the above conditions will not be relevant so permitted development remains open as long as the heat pump and the installation itself comply to key conditions.
Heat pump size
One of the conditions that must be met to comply with permitted development relates to the size of a heat pump’s outdoor compressor unit. The volume of the outdoor unit must not exceed 1.5 cubic metres for heat pump installations on or within the curtilage of a dwellinghouse and must not exceed 0.6 cubic meters for heat pump installations on or within the curtilage of a block of flats – if it is larger, planning permission will need to be obtained.
For some heat pump makes and models, their volume exceeds these limits so they are not eligible for permitted development. The good news is that all of Grant’s air source heat pumps meet the 1.5 cubic meter requirement for dwellinghouses – our R290 heat pumps (4kW, 6.5kW and 9kW models) and all our R32 heat pumps are less than 0.6 cubic metres so this particular requirement for permitted development is automatically satisfied. The Aerona 290 12kW and 15.5kW heat pumps are 0.634 cubic meters in size.
MCS Standards
The heat pump installation must also comply with MCS Planning Standards - Microgeneration Installation Standard MCS 020 a) - a copy of which can be downloaded here. Part of this installation standard relates to sound levels, specifically the sound level calculated at an assessment position adjacent to the nearest doors or windows of the neighbouring building. If a sound level of 37dB(A) or less is calculated, the installation will meet this condition for permitted development. The method for making this sound assessment is detailed in the MCS 020 a) Standard and forms part of MCS installation practices.
Do Grant heat pumps need planning permission?
No, in most cases, you will not need to get planning permission to install a Grant Aerona heat pump. This is because the installation of a Grant air source heat pump falls within permitted development subject to specific site conditions being met. Thanks to their compact size and design, the Aerona³ heat pump and Aerona 290 heat pump give installers, specifiers and their customers one less thing to worry about when working to meet the permitted development requirements. To review all the requirements needed to work within the realms of permitted development, it is always recommended to check with the Local Authority Planning Department.
Please note: Changes are also expected for Wales and Scotland but currently differ from England. Check with your local authority before beginning any installation work.
[This blog was originally published on 21st June 2021 and updated on 29th May 2025.]