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). A block of flats is capped at 0.6 m³ and one unit on the building.
computed
The Town and Country Planning (General Permitted Development) (England) Order 2015 (SI 2015/596), Schedule 2, Part 14, Class G, as amended by The Town and Country Planning (General
Instrument checked 25 Sep 2026. Version 1.0.0.
| Point | Clause | Quote | Source | Version | Checked | In plain words | Input |
|---|---|---|---|---|---|---|---|
| ENG-01 | Class G, permitted development | The installation, alteration or replacement of a microgeneration air source heat pump—(a) on a dwellinghouse or a block of flats; or (b) within the curtilage of a dwellinghouse or a block of flats, including on a building within that curtilage. | www.legislation.gov.uk/uksi/2015/596/schedule/2/ | 1.0.0 | 25 Sep 2026 | This proposal is not covered by this permitted-development class; a planning application may be needed. | Is the building a house, or a building that is wholly flats? |
| ENG-02 | G.1 | Development is not permitted by Class G unless the air source heat pump complies with the MCS Planning Standards. | www.legislation.gov.uk/uksi/2015/596/schedule/2/ | 1.0.0 | 25 Sep 2026 | Compliance with the MCS 020a noise limit is required for this to be permitted development — see the noise check. | What is the noise result at 1 m outside the neighbour's nearest habitable-room window? |
| ENG-03 | G.2(a), as substituted by SI 2025/560 art. 5(3)(a) | the development would result in the presence of (i) more than one air source heat pump on, or within the curtilage of—(aa) a dwellinghouse which is not a detached dwellinghouse; (bb) a block of flats; (ii) more than two air source heat pumps on, or within the curtilage of, a detached dwellinghouse | www.legislation.gov.uk/uksi/2015/596/schedule/2/ | 1.0.0 | 25 Sep 2026 | Too many air source heat pumps already on this building/curtilage for Class G (limit: 1, or 2 on a detached house). | How many outdoor units will the building have once this one is installed?; Is the house detached?; Is the building a house, or a building that is wholly flats? |
| ENG-03-WIND | G.2(b) and G.2(c) | (b) in the case of the installation of an air source heat pump, a wind turbine is installed on the same building or within the curtilage of the dwellinghouse or block of flats; (c) … a stand-alone wind turbine is installed within the curtilage of the dwellinghouse or block of flats | www.legislation.gov.uk/uksi/2015/596/schedule/2/ | 1.0.0 | 25 Sep 2026 | A wind turbine already on this building or curtilage blocks Class G for an air source heat pump. | Is there a wind turbine on the same building or in the garden?; Is there a stand-alone wind turbine in the garden? |
| ENG-05 | G.2(d), as substituted by SI 2025/560 art. 5(3)(b) | the volume of the air source heat pump's outdoor compressor unit (including any housing) would—(i) … a dwellinghouse, exceed 1.5 cubic metres; (ii) … a block of flats, exceed 0.6 cubic metres | www.legislation.gov.uk/uksi/2015/596/schedule/2/ | 1.0.0 | 25 Sep 2026 | The outdoor unit's volume exceeds the Class G limit for your building type (1.5 m³ house / 0.6 m³ block of flats). | What is the outdoor unit volume in cubic metres, including the housing?; Is the building a house, or a building that is wholly flats? |
| ENG-06 | G.2(f) | the air source heat pump would be installed on a pitched roof | www.legislation.gov.uk/uksi/2015/596/schedule/2/ | 1.0.0 | 25 Sep 2026 | Class G does not cover pitched-roof mounting. | Is the unit mounted on a roof? |
| ENG-07 | G.2(g) | the air source heat pump would be installed on a flat roof where it would be within 1 metre of the external edge of that roof | www.legislation.gov.uk/uksi/2015/596/schedule/2/ | 1.0.0 | 25 Sep 2026 | A flat-roof unit within 1 m of the roof edge is not covered by Class G. | Is the unit mounted on a roof?; On a flat roof, how far is the unit from the external edge, in metres? |
| ENG-08 | G.2(h) | the air source heat pump would be installed on a site designated as a scheduled monument | www.legislation.gov.uk/uksi/2015/596/schedule/2/ | 1.0.0 | 25 Sep 2026 | Scheduled monuments are excluded from Class G. | Is the building a scheduled monument? |
| ENG-09 | G.2(i) | the air source heat pump would be installed on a building or on land within the curtilage of the dwellinghouse or the block of flats if the dwellinghouse or the block of flats is a listed building | www.legislation.gov.uk/uksi/2015/596/schedule/2/ | 1.0.0 | 25 Sep 2026 | This cannot be checked reliably against the index — please check your address directly on the Historic England National Heritage List. | Is the building listed? A postcode search cannot clear this. |
| ENG-10 | G.2(j) | in the case of land within a conservation area or which is a World Heritage Site the air source heat pump—(i) would be installed on a wall or a roof which fronts a highway; or (ii) would be installed so that it is nearer to any highway which bounds the curtilage … nearest to that highway | www.legislation.gov.uk/uksi/2015/596/schedule/2/ | 1.0.0 | 25 Sep 2026 | Conservation area/World Heritage Site: this wall-to-highway condition needs checking against your specific address. | Is this exact address inside a conservation area?; Is this exact address in a World Heritage Site?; Does the wall the unit would sit on face a highway?; Does the roof face a highway?; Would the unit sit nearer the highway than the building does? |
| ENG-11 | G.2(k) | in the case of land, other than land within a conservation area or which is a World Heritage Site, the air source heat pump would be installed on a wall of a dwellinghouse or block of flats if—(i) that wall fronts a highway; and (ii) … above the level of the ground floor storey | www.legislation.gov.uk/uksi/2015/596/schedule/2/ | 1.0.0 | 25 Sep 2026 | A highway-facing wall above ground-floor level is not covered by Class G outside a conservation area. | Does the wall the unit would sit on face a highway?; Is the unit above the ground floor? |
| ENG-12 | G.3(aa), inserted by SI 2025/560 art. 5(4)(b) | the air source heat pump is not solely used for the purpose of cooling | www.legislation.gov.uk/uksi/2015/596/schedule/2/ | 1.0.0 | 25 Sep 2026 | Class G covers reversible air source heat pumps, not appliances used solely for cooling; this proposal is not covered by this permitted-development class — a planning application may be needed. | Will the pump be used only for cooling, or for heating as well? |
| ENG-13 | interpretation, ‘MCS Planning Standards’, as substituted by SI 2025/560 | “MCS Planning Standards” means the standards specified in the Microgeneration Certification Scheme for air source heat pumps (being MCS 020 a) - Air Source Heat Pump Sound Calculation (For Permitted Development Installations)) | www.legislation.gov.uk/uksi/2015/596/schedule/2/ | 1.0.0 | 25 Sep 2026 | This row defines a term the other rows use. | No extra input — this row is a definition or a dataset note. |
| ENG-14 | interpretation, ‘block of flats’ | “block of flats” means a building which consists wholly of flats | www.legislation.gov.uk/uksi/2015/596/schedule/2/ | 1.0.0 | 25 Sep 2026 | Enter: Is the building a house, or a building that is wholly flats?. | Is the building a house, or a building that is wholly flats? |
| ENG-A4 | article 4(1), 'Directions restricting permitted development' | may make a direction under this paragraph that the permission granted by article 3 does not apply to—(a) all or any development of the Part, Class or paragraph in question in an area specified in the direction; or (b) any particular development, falling within that Part, Class or paragraph, which is specified in the direction | www.legislation.gov.uk/uksi/2015/596/article/4 | 1.0.0 | 25 Sep 2026 | An Article 4 direction applies here — the exact wording of the specific direction needs checking (it may or may not cover air source heat pumps). | Is there an Article 4 direction on this address?; Does that direction name this permitted-development class? |
| ENG-DATASET | n/a — planning.data.gov.uk coverage gap | No statutory sentence is stored for this row. It records a gap in the geographic file, and a missing row is not a clearance. | www.gov.uk/guidance/find-planning-data | 1.0.0 | 25 Sep 2026 | Enter: Is this authority covered by the planning dataset that was consulted?. | Is this authority covered by the planning dataset that was consulted? |
| mcs020a_1_1 | §1.2 | the permitted development noise limit of 37 dB LAeq,5mins (at the assessment positions ignoring the effect of the façade) | mcscertified.com/wp-content/uploads/2025/07/MCS- | 1.0.0 | 25 Sep 2026 | The noise limit in this method is 37.0 dB(A). | Sound power of the outdoor unit, distance to the neighbour’s window, and directivity Q. |
Next pages
The Town and Country Planning (General Permitted Development) (England) Order 2015 (SI 2015/596), Schedule 2, Part 14, Class G, as amended by The Town and Country Planning (General Permitted Development) (England) (Amendment) Order 2025 (SI · 25 Sep 2026 · n=17 · Each row is a point in docs/decision-contract.yaml. The engine that scores them is scripts/contract_engine.py. · updated 25 Sep 2026 · version 1.0.0 · CSV of the values on this page
Source detail
https://www.legislation.gov.uk/uksi/2015/596/schedule/2/part/14