Do you need planning permission for air conditioning?
For most houses in England, still no, but the detail changed meaningfully in spring 2026, and it’s worth being precise rather than relying on general permitted development guidance written before then. This page covers the current position; three follow-up guides below go into the parts that trip people up most.
The current permitted development rules
A domestic air conditioning installation on a house in England is normally permitted development, meaning no planning application, as long as it stays inside these limits:
- The outdoor unit is no bigger than 1.5 cubic metres
- A detached house can have up to two units under permitted development; any other house type (semi-detached, terraced) is limited to one
- The unit isn’t mounted on a pitched roof
- Noise has been assessed using the MCS 020a calculation, the only route accepted since 28 May 2026
The old “1 metre from the boundary” rule that a lot of guidance (including our own earlier version of this page) used to quote was removed on 29 May 2025. It no longer applies, and any advice still citing it is out of date.
The change that actually matters most: cooling-only vs heat-and-cool
The biggest shift in May 2026 wasn’t a measurement, it was a distinction: heat-and-cool (reversible) units are permitted development, cooling-only units are not. If your installation is cooling-only, you need a planning application regardless of size or position. This is genuinely the detail most likely to catch people out right now, and it’s the whole subject of our cooling-only vs heat pump planning guide.
Noise: the MCS 020a calculation
Since 28 May 2026, MCS 020a is the only accepted way to demonstrate an installation won’t need permission on noise grounds. It’s a calculation, not a guess, and the unit’s exact position is usually what decides whether it passes. We cover what the calculation actually checks in our MCS 020a noise rules guide.
Where permitted development doesn’t apply at all
Three situations sit outside permitted development entirely, whatever size or type of unit you’re installing: listed buildings, Article 4 areas (common in conservation areas), and flats, which have their own tighter size limit and never get the same rights as houses. We’ve written these up properly in our guide to air conditioning in conservation areas, listed buildings and flats.
England only
Everything on this page and its follow-ups applies to England specifically. Wales has its own, different permitted development rules for air source heat pumps. Scotland is currently consulting on changes and hasn’t adopted the same framework. If you’re outside England, treat this as background reading, not a rulebook for your installation.
Our approach
We specify heat-and-cool systems as standard, run the MCS 020a noise check as part of every quote, and ask about property type and location upfront, so a permitted development installation stays that way. None of this holds up your quote or changes the price: it only affects paperwork before installation day.