Many reversible systems can be permitted development, but the rules are national and conditional. Here are the current England changes, plus the checks every UK property still needs.
Orientation checker
Answer the property and system questions to identify whether England’s domestic Class G route may be relevant or whether formal advice is the safer next step.
Instant result · no email requiredThis cannot grant planning permission or interpret an individual lease, Article 4 direction or planning condition. It is an orientation tool based on the national rules described below.
| Your situation | Planning permission? |
|---|---|
| House in England — reversible system, every Class G condition met | Usually no application — permitted development |
| Cooling-only unit in England | Not covered by Class G |
| Block wholly made up of flats in England | May qualify, but separate freeholder consent still applies |
| Listed building or scheduled monument | Do not rely on Class G; obtain specialist advice |
| Conservation Area or World Heritage Site | Extra highway-facing siting limits apply |
| Wales, Scotland or Northern Ireland | Use that nation’s current planning rules |
| Commercial premises | Domestic Class G is not the answer; check per project |
This is orientation, not a formal planning determination. Article 4 directions, planning conditions, leases and title restrictions can remove or constrain rights that would otherwise exist. Confirm with the relevant local planning authority and property owner before work.
England’s Class G permitted-development right was widened. The old rule excluding units within one metre of the property boundary was removed. The maximum outdoor-compressor volume for a house increased from 0.6m³ to 1.5m³. A detached house can have its first two air-source heat pumps under the right; a non-detached house or block of flats is limited to the first installation.
Cooling is now allowed, but not cooling alone. The system must be an air-source heat pump capable of heating, and the installation must comply with MCS 020a. From 28 May 2026, Planning Portal says MCS 020a is the only permitted certification scheme for this route.
Other limits remain. A house unit may not exceed 1.5m³; a unit serving a block of flats may not exceed 0.6m³. Installations on pitched roofs are excluded. Every part of a flat-roof installation must be at least one metre from the roof edge. An existing wind turbine affects eligibility. Protected sites and highway-facing positions have additional restrictions.
Read the complete Planning Portal air-source heat-pump conditions. Passing the size or noise test alone does not create permission; every applicable limit and condition must be met.
Flats and leaseholds. England’s right can apply to a block consisting wholly of flats, but the unit-count and 0.6m³ limits apply. Planning status does not override the lease: a freeholder or management company may control walls, balconies, roofs, noise and penetrations. Read the heating-specific heat pump for flats guide before committing to a design.
Listed buildings and scheduled monuments. Class G does not apply within their curtilage. Listed-building consent may also be needed, and unauthorised work can be a criminal offence. Obtain conservation and planning advice before choosing a product or drilling route.
Conservation Areas and World Heritage Sites. An air-source heat pump cannot use the right on a wall or roof fronting a highway, or where it would sit closer to a bounding highway than any part of the building. Other local restrictions can still apply.
Wales, Scotland and Northern Ireland. Planning is devolved. Do not copy the England thresholds into another nation. Use the relevant national planning portal or authority and ask the installer to identify the rule set in the quote.
Planning is partly a placement problem, and placement is what a site survey resolves. The installer should supply the exact model dimensions, heating capability, location and MCS 020a noise calculation. Your quote should then say whether the design relies on permitted development and who confirms any planning application, lawful-development certificate, freeholder consent or listed-building consent.
A system with no condenser box can reduce visual impact, but a fixed monoblock normally still creates façade grilles. Compare those constraints in the air conditioning without an outdoor unit guide rather than assuming “all indoors” means no permission.
It depends on the nation, property and design. In England, many reversible air-to-air heat pumps are permitted development when every Class G condition is met. Cooling-only systems do not qualify through that route. Listed buildings, protected sites, some highway-facing positions and properties with removed permitted-development rights need extra checks. Wales, Scotland and Northern Ireland have separate rules.
The installation must comply with MCS 020a, must not be used solely for cooling, and must meet unit-count, size, roof, protected-site and highway-facing limits. The old one-metre boundary exclusion was removed in May 2025. House units may be up to 1.5m³; the limit for a block of flats is 0.6m³. Check the complete current list, not one condition in isolation.
Not automatically in England: Class G can apply to a block consisting wholly of flats when every condition is met, including the 0.6m³ outdoor-unit limit and only the first air-source heat pump installation. Leasehold or freeholder consent is separate and may still prevent external work. A flat within mixed-use premises or a different UK nation needs its own planning check.
In England, Class G permitted development does not apply within the curtilage of a listed building or a scheduled monument. Conservation Areas and World Heritage Sites have extra restrictions on highway-facing walls and roofs. Listed-building consent may also be required. Do not assume a rear position is automatically acceptable; ask the local planning authority.
A competent installer should identify obvious constraints and provide the model, dimensions, position and MCS 020a noise calculation needed for the decision. The property owner remains responsible for having the required permission and private consent. Ask in writing who will obtain any lawful-development certificate, planning application, listed-building consent or freeholder approval.
Where permission or consent was required, the local authority can investigate and may require alteration or removal. Unresolved planning or lease breaches can also complicate a sale. Retrospective approval is not guaranteed, and unauthorised work to a listed building can be a criminal offence. Confirm the route before equipment is fixed or walls are drilled.
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