Air source heat pumps

Updated: 28 May 2025

Permitted development

You can install a single air source heat pump (ASHP) without planning permission if it meets all the following restrictions.

  1. The proposed ASHP is located within a dwelling house, block of flats or their curtilage. You will need to submit a planning application for non-domestic units.
  2. Detached dwellings are restricted to 2 ASHPs, all other dwellings or flats are restricted to one only.
  3. The dwelling house or block of flats is not listed or a scheduled monument.
  4. The noise of the ASHP, calculated using the Microgeneration Certification Scheme (MCS) methodology, must not exceed 37dB(A) at the nearest habitable room of a neighbouring property. Your installer will be able to tell you more.
  5. The dimensions of the unit do not exceed 1.5 cubic metres for detached, semi-detached or terraced dwellings.  Flats are limited to 0.6 cubic metres.
  6. The unit is not installed on a pitched roof or within 1 metre of the edge of a flat roof.
  7. The ASHP can be heating only, or a combined heating and cooling unit. Cannot be cooling only.
  8. The dwelling house or block of flats does not have a wind turbine installed, either on the building or within its curtilage.
  9. The unit is not installed on any part of a wall that is above the level of the ground floor storey where the wall fronts a highway.
  10. The ASHP is situated where it will have the least impact on the appearance of the building and local area. This generally means installing the unit to the rear of the property.  If that is not possible, we would expect the unit to be screened from view or to blend in with the property.
  11. The ASHP is removed as soon as reasonably practicable when no longer needed.

Dwellings or blocks of flats in a conservation area

In addition to the points above, if the dwelling house or block of flats is in a conservation area, the unit must not be:

  • installed on a wall or a roof that faces a highway OR
  • closer to the highway than any part of the dwelling house or block of flats that is nearest to that highway

For clarity, we recommend a Certificate of Lawfulness application. This will formally assess your proposal against the above points. A copy of the application form can be downloaded from our Planning application forms page. The MCS noise calculation must be included with the application.

When planning permission is needed

You must submit a planning application when:

  • you wish to install more than 2 ASHPs on a detached house, or more than one on any other type of dwelling
  • if any of the above statements are untrue

You must submit a noise assessment report with your application if your proposed ASHP exceeds 37dB(A) at the nearest assessment point. This is determined by the MCS calculation.

The report should refer to the Institute of Acoustics’ briefing notes on reducing noise. These provide practical recommendations on bringing noise down to an acceptable level.

The location of the unit is also an important consideration. The visual impact on the appearance of the building or locality must be minimised. The provision of appropriate screening should be considered.

If a planning application is needed, the application should include the following:

  • a site plan showing the precise location of the unit – 1:500 or 1:200
  • elevations showing the unit’s positioning – 1:100 or 1:50
  • the unit’s technical specification
  • noise assessment report, if needed

More information

For more information, view: