In England, an air source heat pump is permitted development under Class G of the 2015 Order, and what takes a unit outside Class G is a defined list: too many units, too big a box, the wrong roof, a listed building, or a position facing the street. A ground source system sits in Class C instead. In England it is the Environment Agency's permitting regime that applies to it.
The short answer by heat pump type
Air source heat pumps carry a list of limits and conditions. Ground source and water source heat pumps sit in Class C and Class D in England, and in Classes 6D and 6E in Scotland. They are two separate planning questions, and the answer to one does not carry over.
In England, the rights sit in Part 14 of the Town and Country Planning (General Permitted Development) (England) Order 2015. Class G of that Part covers air source heat pumps, and sets out the limits and conditions below. Class C of the same Part permits the installation, alteration or replacement of a microgeneration ground source heat pump within the curtilage of a dwellinghouse or a block of flats, and Class D does the same for a water source heat pump. The Planning Portal puts the practical effect plainly: installing a ground source or water source heat pump on domestic premises is usually considered to be permitted development, not needing an application for planning permission.
Scotland splits them the same way. Paragraph 6.4 of planning circular 1/2024 covers Class 6D for ground source and Class 6E for water source, allowing the pump and any associated equipment and pipework within the curtilage of a dwellinghouse or a building containing a flat, and states: "There are no additional restrictions on those PDR." Class 6H, the air source class, is where Scotland's conditions live.
What takes an English air source heat pump out of permitted development
Read this list as a checklist against the position your installer has pencilled in. Paragraph G.1 comes before any of the measurements: development is not permitted unless the air source heat pump complies with the MCS Planning Standards. Since 29 May 2025 that phrase points at one specific document, MCS 020 a), and the words "or equivalent standards" were removed from the paragraph on the same date. The sound calculation inside it is the real test, and we work through it in the heat pump noise rules.
- Unit count. For detached houses, the first two air source heat pumps are permitted development. A house that is not detached, and a block of flats, get one.
- Box size. The outdoor compressor unit including its housing must not exceed 1.5 cubic metres on a house, or 0.6 cubic metres on a block of flats.
- Pitched roofs. Installations on pitched roofs are not permitted development at all.
- Flat roofs. On a flat roof the unit must be at least one metre from the external edge of that roof.
- Listed buildings. Permitted development rights do not apply for installations within the curtilage of a listed building.
- Scheduled monuments. Installation on a scheduled monument is excluded.
- Conservation areas and World Heritage Sites. The unit must not be installed on a wall or roof which fronts a highway.
- Everywhere else. It cannot go on a wall fronting a highway above the level of the ground floor storey.
- Cooling only. A condition inserted on 29 May 2025 requires that the air source heat pump is not solely used for the purpose of cooling.
One rule that used to be on that list has gone. In the 2015 text as originally made, sub-paragraph G.2(e) said development was not permitted if any part of the air source heat pump would be installed within 1 metre of the boundary of the curtilage of the dwellinghouse or block of flats. That sub-paragraph was omitted on 29 May 2025 by article 5 of the 2025 amendment order, and no boundary distance appears in the current list of limits.
Two further conditions in G.3 are easy to forget because they are written as duties rather than measurements. The unit must be sited, so far as practicable, to minimise its effect on the external appearance of the building and on the amenity of the area, and it must be removed as soon as reasonably practicable once it is no longer needed.
Ground source is the simpler planning case and the harder permit case
In England, a closed loop ground source system installed on or after 2 October 2023 is treated as a new system by the Environment Agency, which is a consent separate from planning. The guidance is direct about the cut-off: if your ground source heating and cooling system was installed before 2 October 2023, it is an "existing" system, and if it is installed on or after that date, it is a "new" system.
A new system has to do one of four things: meet all the criteria in the exemption conditions for systems in low environmental risk settings, meet all the conditions in the regulatory position statement, get a standard rules permit, or get a bespoke permit.
The regulatory position statement is RPS 307, and its conditions read like a description of an ordinary house: a maximum output no greater than 45 kilowatts, a system only for use by residential premises such as a house or buildings designed for people to live in, installed after 2 October 2023, and a sealed closed loop system that has no discharge, other than heat, to the environment. Where your activity meets the description and follows the conditions and does not cause pollution or harm to human health, the Environment Agency will not normally take enforcement action against you. The statement is explicit that it does not remove the need for an environmental permit or exemption, so it is a position rather than a consent.
Wales takes a different view of the same hardware. Natural Resources Wales states that closed loop ground source heat pumps do not require any permissions from it, on the basis that under normal operation they do not introduce pollutants into the aquifer. If you are quoting for a borehole, the regime that applies depends on which side of the border the hole is drilled.
Check the siting before you commit to a unit
The planning answer changes with where the box goes, so it is worth settling with an MCS-certified installer who has stood in the garden. Tell us about your home once and we will pass your details to installers covering your postcode.
Where the four nations actually part company
A position that is fine in England can fail in Scotland or Northern Ireland, and the differences that bite are the unit count, whether a boundary distance applies, and what a conservation area does to the rights. The per-nation detail on the noise standards themselves sits in our heat pump noise guide.
Wales now reads close to England. Gov.wales states that permitted development rights for air source heat pumps were updated on 1 June 2026, and the limits it lists are England's: up to two units if your home is detached and one if it is not, an outdoor compressor unit not exceeding 1.5 cubic metres, nothing on a pitched roof, and at least one metre in from the external edge of a flat roof. A cooling-only unit does not qualify, and an air source heat pump cannot go on a listed building under these rights. In a conservation area it cannot go on a wall or roof facing a highway, or sit closer to a bounding highway than the nearest part of the house; outside one, it cannot go on a street-facing wall above ground floor level. Wales used to run a blunter rule. A Welsh Government written statement of 11 January 2024 described the rights then in force as requiring a minimum 3-metre distance from the neighbour's boundary, to reduce noise pollution potential. That distance does not appear anywhere in the limits gov.wales lists today.
Scotland is tighter on number and on conservation areas. Class 6H permits one air source heat pump on the same building, allows no protrusion of more than 1 metre from the outer surface of an external wall, roof plane, roof ridge or chimney, and caps any resulting structure within the curtilage at 3 metres in height. In a conservation area the unit is only permitted at ground floor level on the rear elevation, which rules out a side return. Nothing is permitted in a World Heritage Site or within the curtilage of a listed building, and the equipment must comply with MCS Planning Standards for air source heat pumps or equivalent standards.
Northern Ireland is the one nation that still has a boundary rule. Class G of Part 2 of the Schedule to the Planning (General Permitted Development) Order (Northern Ireland) 2015 allows one air source heat pump within the curtilage of a dwellinghouse, and no part of it may be within 1 metre of the boundary of the curtilage of another dwellinghouse. It cannot sit forward of a wall facing a road that forms the principal or a side elevation of the original dwellinghouse, cannot exceed 3 metres in height, cannot go on a roof at all, and cannot go within the curtilage of a listed building unless listed building consent has previously been granted. In a World Heritage Site or conservation area, no part may face onto and be visible from a road. Northern Ireland also treats ground and water source heat pumps under its own Class F, which restricts any part within 3 metres of the curtilage boundary that would exceed 4 metres in height, and excludes sites of special scientific interest and sites of archaeological interest.
What it costs and takes if you do need permission
A householder application in England costs £548 and the council has eight weeks to decide it. The gov.uk planning fee schedule from 1 April 2026 sets the fee for the enlargement, improvement or other alteration of existing dwellinghouses at £548 where the application relates to a single dwellinghouse. The government’s planning guidance gives the statutory time limit as 8 weeks for all types of development other than major development and a handful of specialist categories. If the authority needs longer it should ask you to agree an extension of time, and that agreement must be in writing and set out the timescale within which a decision is expected.
That eight weeks only covers the council's decision. Add the time your installer needs to draw the position and complete the sound calculation, and a refusal puts you back at the siting question with the heating season closer. Settling the position at survey stage costs a conversation; getting it wrong costs a season.
Section 7 of the Planning (Listed Buildings and Conservation Areas) Act 1990 provides that no person shall execute works for the alteration or extension of a listed building in any manner which would affect its character as a building of special architectural or historic interest unless the works are authorised under section 8. In Northern Ireland the permitted development right for a heat pump in the curtilage of a listed building only exists where that consent has already been granted. Permitted development rights can also be taken away. The Planning Portal notes they may be removed through a planning condition, an Article 4 Direction or other restriction. Ask your council's planning team about your own address.
Four questions worth asking before you sign
- Which class are we relying on, and have you written the position down against each of its limits?
- Has anything on this address removed permitted development rights, by planning condition or Article 4 Direction?
- For a ground source quote, which environmental permitting route are we using, and will the system stay under 45 kilowatts?
- If the siting fails a limit, what is the alternative position, and does it change the pipe runs or the flow temperature?
The last question is the one with money in it. Moving a unit to clear a limit lengthens pipe runs and can push the design the wrong way, which lands straight on the sizing and emitter work covered in our guides to heat pump sizing and radiators and heat pumps. Price the result with our UK heat pump cost guide before you commit to a position.
Frequently asked questions
Not if the install stays inside the limits for your nation. In England, paragraph G.1 states that development is not permitted by Class G unless the air source heat pump complies with the MCS Planning Standards, and the Class G limits allow no more than two units on a detached house and one otherwise, an outdoor compressor unit not exceeding 1.5 cubic metres, nothing on a pitched roof, and at least one metre in from the edge of a flat roof. Work falling outside Class G is not permitted development, so it needs an application.
No boundary distance appears in England’s current list of limits. In the 2015 text as originally made, sub-paragraph G.2(e) said development was not permitted if any part of the air source heat pump would be installed within 1 metre of the boundary of the curtilage, and that sub-paragraph was omitted on 29 May 2025 by article 5 of the 2025 amendment order. Northern Ireland still applies a 1 metre rule, measured to the boundary of the curtilage of another dwellinghouse. Wales dropped its three metre rule when it updated its rights on 1 June 2026.
Class C of Part 14 permits a microgeneration ground source heat pump within the curtilage of a dwellinghouse or a block of flats in England, and the Planning Portal describes a domestic ground or water source heat pump as usually considered to be permitted development, not needing an application for planning permission. In Scotland, paragraph 6.4 of circular 1/2024 covers Classes 6D and 6E and states there are no additional restrictions on those rights. In England the system instead falls under the Environment Agency's permitting regime.
In England, a closed loop system installed on or after 2 October 2023 counts as a new system and must either meet the exemption conditions, meet the conditions of RPS 307, hold a standard rules permit, or hold a bespoke permit. RPS 307 covers a sealed closed loop system with a maximum output no greater than 45 kilowatts serving residential premises only, and where its conditions are met the Environment Agency will not normally take enforcement action. Natural Resources Wales states closed loop systems need no permission from it.
Not under permitted development. In England, rights do not apply for installations within the curtilage of a listed building, and the same exclusion appears in Wales and in Scotland's Class 6H. Northern Ireland words it differently: Class G is not permitted within the curtilage of a listed building unless listed building consent has previously been granted. Section 7 of the Planning (Listed Buildings and Conservation Areas) Act 1990 separately provides that works for the alteration or extension of a listed building which would affect its character as a building of special architectural or historic interest must be authorised under section 8.
£548 in England for a householder application. The gov.uk fee schedule from 1 April 2026 sets the fee for the enlargement, improvement or other alteration of existing dwellinghouses at £548 where the application relates to a single dwellinghouse. The government's planning guidance gives the statutory time limit as 8 weeks for all types of development other than major development and a handful of specialist categories. Any agreed extension of time must be in writing.
Yes, and it is worth checking before the survey. The Planning Portal notes that permitted development rights may be removed through a planning condition, an Article 4 Direction or other restriction. Ask your local planning authority about your specific address.
No. Paragraph G.1 makes compliance with the MCS Planning Standards a requirement, so failing the sound calculation removes the rights, but meeting it only clears that one gate. The other Class G limits on unit count, volume, roofs, listed buildings, conservation areas and street-facing walls all still have to be met. The calculation itself is set out in our heat pump noise guide.