Through-wall air conditioning in the UK usually means a sleeve unit or a compact chassis through an external wall, not a full split with a remote outdoor condenser. It can look cheaper on day one and cost more in noise and efficiency over a heatwave season. 2026 planning illustrations for a simple through-wall job often sit below a surveyed split, until builders work, electrics and making good arrive. Choose it only when a true outdoor unit is impossible, not as the default bargain.
Through-wall versus true split
A true split puts the noisy heat rejection outside and the quiet indoor on the wall. Through-wall packs more of the machine into the room envelope. Sleeves need a correctly sized core hole, lintel awareness in masonry, and weather sealing. Some products are little more than a loud window unit in a permanent hole.
F-gas still applies if the product contains fluorinated refrigerant and the circuit is opened. DIY through-wall kits are not automatically exempt from competent install.
- Sleeve and structural opening drive joinery and masonry cost.
- Noise sits closer to occupants than a remote condenser.
- Efficiency often trails a modern R32 split heat pump.
- Outdoor-free sites (some flats) are the honest use case.
2026 cost illustrations
Treat these as illustrations, not a tariff. A straightforward through-wall replacement into an existing sleeve can sit in the low hundreds to around a thousand pounds including a basic unit and labour in simple cases. New core drilling, specialist lintels, awkward access and decorating push into higher hundreds or low thousands. A comparable quiet split with outdoor brackets often lands higher on equipment and labour but wins on comfort.
London parking, landlord approvals and asbestos sleeves change the number more than the brochure.
When not to choose through-wall
If you can site a legal outdoor condenser, a split is usually the better long-term comfort product. Through-wall is a compromise for listed street fronts, some apartments, or plant rooms where external plant is banned.
Do not core a party wall or a structural opening without advice. Do not assume a US through-wall chassis fits UK cavity widths.
How to get a usable quote
Wall construction, existing hole size if any, room use, noise sensitivity and whether a remote outdoor is actually possible. Photos inside and out.
Use the quote form. Ask for a split alternative on the same survey so you see the true cost of silence.
Frequently asked questions
Is through-wall cheaper than a split?
Sometimes on day-one install if a sleeve already exists. Lifetime comfort and running cost often favour a proper split when outdoors are allowed.
Do I need planning permission for through-wall?
A hole in your own wall is mostly a building and lease issue. Flats and listed buildings still need consent conversations. External condensers trigger the familiar air-source heat pump planning questions.
Are through-wall units F-gas relevant?
If they contain F-gas and work involves the refrigerant circuit, certified competence applies. Ask what the product contains and who is allowed to install it.
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.