Planning permission

Many web-sites suggest that mini-split heat pump and air-conditioning units fall under permitted development and that planning permission is not required. For most domestic installations that is often the case.

It is worth noting that permitted development conditions vary for England, Wales, Scotland and Northern Ireland.

Detailed information

England

The relevant legislation is Part 14 G of The Town and Country Planning (General Permitted Development) (England) (Amendment) Order 2025 . This is an amendment to Part 14 G of The Town and Country Planning (General Permitted Development) (England) Order 2015  (use the /previous/next paragraph buttons).

The latter document is useful because it is more ‘readable’, and includes the May 2025 amendments.

Key points include:

• It must comply with MCS planning standards - see Noise and neighbours.
• Up to two air source heat pumps for detached dwelling houses (increased from one in the previous rules). One unit is still the limit within the curtilage of a block of flats or non-detached property.
• The requirement that a heat pump must be more than 1m from the property boundary has been removed.
• Must be more than 1m from the edge of a flat roof. Not on a pitched roof.
• The heat pump must not be greater than 1.5m³ for dwelling houses (an increase from 0.6m³). The 0.6m³ limit remains for a block of flats.
• Not fronting a highway if installed above ground storey.
• Not on, or on the land of, a listed building.
• Not in an AONB, National Park, Conservation Area or World Heritage Site.

The requirement that an air source heat pump must be used solely for heating purposes has been changed to permit air-to-air heat pumps that can also provide a cooling function. This is significant because it removes the previous ambiguity surrounding mini-splits that can provide both heating and cooling. Whilst most Local Authority planning and building control departments were understanding about this, it’s always worth checking with them that they are happy with all aspects of any installation being undertaken as Permitted Development.

Wales
The guidance on the Welsh Government website  differs slightly from England. You should check with the Local Planning Authority.

Scotland
The guidance on permitted development is on the Scottish Government website . It is defined as for heating purposes only. There are some updates to this, including a planning circular see class 6H) 

Northern Ireland
The relevant legislation is Part 2, Class G of The Planning (General Permitted Development) Order (Northern Ireland) 2015 . This was amended in 2023 by The Planning (General Permitted Development) (Amendment) Order (Northern Ireland) 2023 

Building regulations

Note that building regulations are separate from planning permission. They are concerned with the standards of the work rather than the permission to do it

There is some ambiguity around building regulations, mainly related of the definitions of heat pump and air conditioner (since most air conditioners can act as an air-to-air heat pump). For most air-to-air mini-split systems there isn’t a requirement to obtain Building Regulation Approval before installation.

There is much more information in the following links (for England):

Government Statutory Approved Documents - Part L 

Government Statutory Approved Documents - Part F 

Note that Part O (Overheating)  only applies to new residential buildings, not extensions or conservatories added to existing residential buildings.

Part P (Electrical safety)  is discussed further in the electricity supply page.

< Previous Next >