The planning rules, nation by nation
England, Wales and Scotland each have their own permitted-development rules for outdoor heat pumps; Scotland's class covers heating and hot water only, so a unit used for cooling needs an application there (checked 25 Sep 2026).
- Do the English rules allow an outdoor heat pump without a planning application?
On a house, Class G allows the outdoor unit when it is within 1.5 m³, there is only one (two on a detached house), and it is not used only for cooling (Class G, checked 25 Sep 2026). - Does Scotland’s Class 6H allow cooling?
Class 6H covers an air source heat pump used only for domestic heating or hot water, and the cited noise limit is 42.0 dB(A) (checked 25 Sep 2026). - Do the Welsh rules allow an outdoor heat pump without a planning application?
In Wales the outdoor unit must stay within 1.5 m³ on a house and 1 m³ on a block of flats (Class G, checked 25 Sep 2026).