A conservation area does not automatically ban a split air conditioner, and it does not automatically make one permitted development. In England, Class G still has a path for an air source heat pump, with tighter siting: it must not go on a wall or roof that fronts a highway, and it must not sit nearer to a highway bounding the property than the building. Every other limit still applies, including not using the unit solely for cooling. Listed buildings are a separate bar. Article 4 directions can remove rights. Survey the rear or side first, and expect flats to need permission more often.
A discreet rear wall, not the street elevation
The Planning Portal summary is the household version of the rules. Conservation area and World Heritage Site land is treated more tightly than an ordinary street, but the rights are not simply switched off. A discreet rear wall can still be the right conversation. A street elevation usually is not. Legislation.gov.uk is where Class G sets the highway limits: not on a wall or roof fronting a highway in a conservation area, and not nearer to a bounding highway than the building.
The 2025 condition that the unit is not used solely for cooling sits on top of those siting limits. A cooling-only product does not meet it. A reversible unit still has to meet volume, noise standard, roof and highway rules. Do not treat a heat-pump logo as consent. Energy Saving Trust describes air-to-air heat pumps. That description is not planning permission.
White trunking on brick that planners notice
Planners and conservation officers notice more than the condenser. White trunking across brick, a condensate pipe down a front elevation, and two monobloc grilles on a street wall all change the appearance. Rear alleys can be sensitive too if they are part of the character of the place.
Ask the local authority if you are unsure, and ask whether an Article 4 direction covers external plant.
Listed curtilage is a different bar
Being in a conservation area is not the same designation as being listed. Treat the listed status of this building as its own question before you price a rear wall.
Flats in conservation areas often fail the volume cap, the first-installation limit, or the highway test, and they always have a lease. Often you will need both planning permission and the freeholder. Do not promise yourself a rear-wall exception until someone has looked at this building. The survey should mark the outdoor position on the elevation, show whether that wall fronts a highway, and note trunking and drain routes. GOV.UK F-gas design can wait until the position is credible. Ordering a designer indoor first does not help a refused wall.
Frequently asked questions
Do I always need planning permission in a conservation area?
Not always. Class G can still cover a suitably sited air source heat pump that meets every condition, including not being used solely for cooling. Street walls, listed curtilage, Article 4 directions and many flats fall outside that. Check this building.
Will a monobloc avoid conservation controls?
It avoids a condenser box. The cores and grilles are still an alteration. On a street-facing or listed wall they can need consent just as much as a bracket would.
Does F-gas certification replace conservation consent?
No. F-gas is about who may handle refrigerant. Planning and listed building consent are separate.
Is a neighbour's outdoor unit proof mine is lawful?
No. Theirs may be older, enforced against later, or on a different elevation. Ask the local authority if you are unsure, including whether an Article 4 direction covers external plant.
Does a reversible unit skip listed building consent?
No. Class G does not grant permitted development within the curtilage of a listed building. Listed building consent is its own application. Heating as well as cooling does not slip past that.
Core buying guides
Start with these high-intent guides, then dig into the rest of the library.
Related guides
Sources and further reading
How this guide was prepared
This guide was written by the Local AC Installers Editorial Team. We compare official guidance, legislation and established consumer information, separate general information from project-specific advice, and show publication dates and sources. We do not accept installer accreditation claims at face value.