Class G of Part 14 of Schedule 2 to the Town and Country Planning (General Permitted Development) (England) Order 2015 grants planning permission for installing, altering or replacing a microgeneration air source heat pump on a dwellinghouse or block of flats, or within its curtilage, subject to limits and conditions. An amending order took effect on 29 May 2025, removing the former boundary-distance limit and changing the limits on numbers and size.

What Class G permits

Class G allows the installation, alteration or replacement of a microgeneration air source heat pump on a dwellinghouse or a block of flats, or within the curtilage of either, including on a building within that curtilage. The Planning Portal says the right has applied since 1 December 2011 and that a block of flats must consist wholly of flats, so a building that also has commercial premises does not qualify. The rules here are for England. The Planning Portal notes that the policy in Wales may differ, so Welsh householders should check with their local planning authority.

The certification requirement

Paragraph G.1 says development is not permitted unless the air source heat pump complies with the MCS Planning Standards. Since 29 May 2025 the words allowing "equivalent standards" have been omitted from that paragraph. The Planning Portal describes the standard as MCS 020a. The amending order also said that a developer could carry on with development that was permitted under the old rules but no longer was, until the end of 28 May 2026, so that transitional window has now closed. The wider role of certification is explained in the guide to MCS certification.

Number and size limits

Under paragraph G.2, development is not permitted if it would result in more than one air source heat pump on or within the curtilage of a dwellinghouse that is not detached, or of a block of flats, or in more than two on a detached dwellinghouse. The volume of the outdoor compressor unit, including any housing, must not exceed 1.5 cubic metres for a dwellinghouse or 0.6 cubic metres for a block of flats. Development is also not permitted if a wind turbine is installed on the same building or within the curtilage, whether attached or stand-alone. Any additional heat pump or turbine at the same property needs a planning application.

Roofs and protected buildings

A heat pump cannot be installed on a pitched roof under Class G. On a flat roof it must not be within 1 metre of the external edge of the roof. The right does not apply on a site designated as a scheduled monument, or on a building or land within the curtilage of a listed building. Householders in those situations need to apply for planning permission, and the specific consent rules that come with listed buildings are separate.

Highways, conservation areas and the ground floor

In a conservation area or World Heritage Site, development is not permitted if the heat pump would be installed on a wall or roof that fronts a highway, or nearer to any highway bounding the curtilage than the part of the building nearest that highway. Elsewhere, it is not permitted on a wall that fronts a highway if it would be on any part of that wall above the level of the ground floor storey.

What changed in 2025

The amending order, S.I. 2025/560, changed Class G in several ways from 29 May 2025. Paragraph G.2(e) was omitted, which removed the boundary-distance restriction that the government’s announcement described as the one-metre rule. The limits on numbers were replaced, and paragraph G.2(d) was substituted to set the volume limits of 1.5 and 0.6 cubic metres. The government said in November 2024 that it planned to remove the one-metre rule so that households could install a heat pump without a planning application in England, citing evidence that planning was discouraging some customers.

Conditions and other limits

Paragraph G.3 attaches conditions. The heat pump must not be used solely for cooling, must so far as practicable be sited to minimise its effect on the external appearance of the building and the amenity of the area, and must be removed as soon as reasonably practicable when no longer needed. The Planning Portal also warns that permitted development rights may be removed by a planning condition, an Article 4 direction or another restriction, and that householders may wish to discuss the position with their local planning authority. Funding for heat pumps is covered in the guide to the Boiler Upgrade Scheme, and hybrid systems are considered in the guide to hybrid heat pump and boiler systems.

FAQs

Do I need planning permission for a heat pump in England?

Not if the installation meets all the limits and conditions in Class G, including the MCS Planning Standards, the number and size limits and the location restrictions.

Is the one-metre boundary rule still in force?

No. Paragraph G.2(e) was omitted with effect from 29 May 2025.

Does this apply in Wales?

No. The Order covered here applies to England, and the Planning Portal says Welsh policy may differ.

The bottom line

Class G permits most domestic air source heat pump installations in England without a planning application if the unit meets the MCS Planning Standards, the number and volume limits, the roof rules and the restrictions for listed buildings, conservation areas and highway-facing walls. The 1 metre boundary rule was removed on 29 May 2025, and local restrictions such as Article 4 directions can still apply. This is general information, not regulated advice on any specific installation.

Sources

This guide draws on the following primary sources, current as of 24 September 2026:

• legislation.gov.uk, “The Town and Country Planning (General Permitted Development) (England) Order 2015, Schedule 2, Part 14, Class G”
• legislation.gov.uk, “The Town and Country Planning (General Permitted Development) (England) (Amendment) Order 2025”
• Planning Portal, “Planning Permission: Air source heat pump”
• GOV.UK, “Help to save households money and deliver cleaner heat to homes” (21 November 2024)

Related guides

Best Boiler Deals is an independent guide. We may earn a fee from some links; this never affects what we write. This article is general information, not regulated advice on any specific installation — always confirm the details with a Gas Safe registered engineer.