Planning permission is not automatically required for every air source heat pump in England, but permitted development is not a blanket exemption either.
The short answer
Many domestic air source heat pumps in England can be installed under permitted development when every applicable limit and condition is met. The property, location, number and size of outdoor units, roof or wall position, visual effect and MCS 020a sound calculation can all change the answer. Protected properties and locally restricted sites need particular care.
What matters most
- England's May 2025 changes removed the former one-metre boundary restriction for qualifying installations.
- The outdoor-unit volume limit for a house is now 1.5 cubic metres; a block of flats remains at 0.6 cubic metres.
- Since 29 May 2026, the permitted-development sound assessment must comply with MCS 020a.
- Listed buildings, scheduled monuments, conservation areas and local restrictions require closer checks.
What changed for heat pumps in England?
The rules became more flexible in May 2025. The government changed permitted development rights so that an appropriate air source heat pump can be positioned within one metre of a property boundary. It also increased the maximum outdoor-unit volume from 0.6 cubic metres to 1.5 cubic metres for a house, while the 0.6-cubic-metre limit remains for a block of flats.
Detached houses can now have up to two air source heat pumps under permitted development, subject to the other conditions. Attached houses and blocks of flats are generally limited to the first installation. The rules also allow a qualifying system that provides heating and cooling; a unit used solely for cooling does not qualify under this heat-pump permitted development right.
These changes make more installations possible without a full planning application, but they do not remove the need for careful siting and a compliant sound assessment. This article covers the national planning regime in England; requirements elsewhere in the UK differ.
Sound and siting still shape the answer
From 29 May 2026, MCS 020a is the permitted certification scheme for the sound calculation used by this permitted development right. The assessment considers the proposed outdoor unit, its sound data, position and relationship to neighbouring properties.
Sound should be considered while locations are still being compared. Choosing equipment first and trying to make an unsuitable position work afterwards is the wrong order. Airflow, service access, pipe routes, condensate, visibility, neighbouring windows and gardens belong in the same design conversation.
The unit must, as far as practical, be positioned to minimise its effect on the building's external appearance and the amenity of the area. A position that appears convenient on a photograph may not remain suitable after these checks.
The main permitted development limits
For a house, the outdoor compressor unit and its housing must not exceed 1.5 cubic metres. For a block of flats, the limit is 0.6 cubic metres. Up to two heat pumps may qualify at a detached house. At an attached house or block of flats, only the first installation is normally covered.
An existing wind turbine at the building or within its grounds can prevent this permitted development right from applying. A heat pump on a pitched roof is not permitted development under these rules. On a flat roof, every part of the unit must be at least one metre from the roof's external edge.
Restrictions also apply to some highway-facing walls and positions, with additional conditions in conservation areas and World Heritage Sites. Every applicable condition has to be met; passing one measurement does not settle the full planning position.
- SizeConfirm the complete outdoor unit and housing against the limit for the property type.
- NumberCheck existing heat pumps and whether the home is detached, attached or a block of flats.
- PositionReview roof, highway-facing, protected-area and neighbour relationships.
- SoundUse the proposed equipment and exact position for the MCS 020a calculation.
Does the unit still need to be one metre from the boundary?
Not under the current national permitted development condition for England. The former rule preventing an outdoor unit from being within one metre of the property boundary was removed in May 2025.
That does not mean every boundary position is acceptable. The MCS 020a sound assessment and wider siting conditions still apply. Clearance required by the manufacturer, unobstructed airflow, maintenance access and the effect on neighbours must also be considered.
The practical question is not simply whether the unit is more than a metre away. It is whether this equipment can work safely, quietly and serviceably in this exact position while the proposal meets every planning condition.
Protected properties and local restrictions
The permitted development right does not apply within the grounds of a listed building or within a scheduled monument site. A conservation area does not automatically rule out every heat pump, but it introduces positioning restrictions and may require closer local review.
Permitted development rights can also be removed through an Article 4 direction, a condition on an earlier planning permission or another local restriction. Leasehold, freeholder or estate permissions are separate from planning and may still be required.
Listed-building consent and planning permission are separate questions. Owners of protected or unusual properties should speak to the local planning authority before work begins rather than assuming a national checklist provides the complete answer.
A sensible heat-pump planning sequence
Start by establishing the home's likely heat requirement and the type of system being considered. Identify realistic outdoor positions with usable airflow, service access and pipe routes, then check the property's planning status and any local restrictions.
Compare equipment that suits the design rather than forcing a preselected unit into the available space. Complete the relevant sound and permitted-development checks, and confirm whether the route is permitted development, a lawful development certificate, planning permission or another consent before installation.
A lawful development certificate can sometimes provide formal confirmation that proposed work is lawful even when a full planning application is not required. The local planning authority can explain the appropriate route and any fee.
Vireo's online heat-pump journey can organise early property information and flag obvious siting questions. It remains an indicative first step: final capacity, equipment, location, permissions, scope and price require survey-led technical review.
Plan the location before treating permission as settled.
England's revised rules give more households a possible permitted-development route, especially where outdoor space is tight. The strongest project still begins with design: understand the home, identify credible locations, check sound and planning constraints, then confirm the exact route before committing to equipment.
Vireo starts with an indicative assessment and moves towards survey-led technical checks. That keeps planning, sound, heat requirement, equipment and installation scope connected instead of treating permission as a last-minute box to tick.
Before you move forward.
Can a heat pump go next to a neighbour's boundary?
The old one-metre boundary restriction was removed in England in May 2025, but a proposed boundary position must still pass the applicable MCS 020a sound calculation and all other siting, planning, airflow and access checks.
Can I put an air source heat pump on a roof?
Not on a pitched roof under this permitted development right. A unit on a flat roof must be at least one metre from the roof's external edge and meet the remaining conditions.
Do the same rules apply across the UK?
No. This article covers England. Check the relevant national guidance and local planning authority for a property in Wales, Scotland or Northern Ireland.
Does permitted development mean no paperwork is needed?
Not necessarily. The proposal still needs evidence that the conditions are met. Some owners may seek a lawful development certificate, and separate building, leasehold, freeholder or electrical requirements can apply.
Official guidance
Useful primary sources for the rules and technical context mentioned in this article.