Changes to the permitted development rules for air source heat pumps in England took effect on 29 May 2025, made by The Town and Country Planning (General Permitted Development) (England) (Amendment) Order 2025 (S.I. 2025/560)1. The order substituted the quantity limits in paragraph G.2(a) of Class G, Part 14, Schedule 2 of the General Permitted Development Order, and made further amendments to paragraphs G.1, G.2(d), G.2(e) and G.3(a)1.
The restated limits in paragraph G.2(a) are one air source heat pump on, or within the curtilage of, a dwellinghouse which is not a detached dwellinghouse, and one on, or within the curtilage of, a block of flats; and no more than two air source heat pumps on, or within the curtilage of, a detached dwellinghouse1. The same paragraph continues to rule out permitted development where a wind turbine is installed on the same building or within the curtilage, or where a stand-alone wind turbine is installed within the curtilage1.
Paragraph G.2(d) was also substituted, setting volume limits for the outdoor compressor unit including any housing: 1.5 cubic metres for a dwellinghouse, and 0.6 cubic metres for a block of flats1. Paragraph G.2(e) was omitted, as was paragraph G.3(a)1. A new condition at G.3(aa) provides that the air source heat pump is not solely used for the purpose of cooling1. The remaining conditions are unchanged: the pump must, so far as practicable, be sited to minimise its effect on the external appearance of the building and on the amenity of the area, and must be removed as soon as reasonably practicable when no longer needed1.
Paragraph G.1 previously required compliance with the MCS Planning Standards; the words imposing that requirement were omitted on 29 May 20251. The legislation page records the omission but does not set out a replacement requirement in that paragraph1.
Other exclusions in Class G are unchanged by this order. Development is not permitted if the pump would be installed on a pitched roof, or on a flat roof within 1 metre of the external edge, or on a site designated as a scheduled monument, or on a building or land within the curtilage where the dwellinghouse or block of flats is a listed building1. In a conservation area or World Heritage Site, installation on a wall or roof fronting a highway, or nearer to a highway bounding the curtilage than the nearest part of the building, is excluded; elsewhere, installation on a wall fronting a highway above ground floor storey level is excluded1.
| Situation | Air source heat pumps permitted under Class G |
|---|---|
| Dwellinghouse which is not detached | One |
| Block of flats | One |
| Detached dwellinghouse | Two |
Why it matters for households
Permitted development rights allow certain heat pump installations to proceed without a planning application, so the number and size limits in Class G determine how far a household can go before planning permission is needed. The restated limits mean a semi-detached or terraced house, or a flat, sits at one unit, while a detached house can have two1. The volume caps of 1.5 cubic metres for a dwellinghouse and 0.6 cubic metres for a block of flats set the size of outdoor compressor unit that stays within the route1.
For a home's energy independence, the practical effect is that the number of units a property can host without planning permission is fixed by dwelling type, which matters where a larger or multi-unit installation is being considered. The conditions on siting and on removal when no longer needed continue to apply1. Where a property is in a conservation area, a World Heritage Site, or is listed, or where a scheduled monument is involved, the exclusions above remove the permitted development route for the positions described1. Local Article 4 directions can withdraw permitted development in a defined area, and the permitted development rights framework is where these limits sit. Guidance on the planning position in England is set out in Heat Pump Planning Permission in England, and the wider context is covered under heat pumps and household energy independence.
What happens next
The amendments came into force on 29 May 20251. No further dated steps are set out in the legislation page.
Sources1 cited
- [](https://www.legislation.gov.uk/uksi/2015/596/schedule/2/part/14/crossheading/class-g-installation-or-alteration-etc-of-air-source-heat-pumps-on-domestic-premises/data.xht), legislation.gov.uk