Air conditioning without an outdoor unit: your options

Yes, you can have air conditioning without an external unit. There are two genuine ways to cool a home with no outdoor condenser: a monobloc (a single, all-in-one unit mounted on an internal wall and fed by two small holes drilled through to the outside), or a portable unit that vents warm air through a window or wall hose. What you cannot do is run a conventional split system without an outdoor unit, because a split has to reject the heat it collects somewhere, and that job belongs to the outdoor condenser.

That makes the no-condenser route the answer for a lot of homes: flats and apartments, listed buildings, conservation areas, leasehold properties where the freeholder will not allow a box on the wall, and any home with no suitable outside space. It is a real, workable option. It just comes with trade-offs in efficiency, output and noise that are worth understanding before you buy, and that is what this guide sets out plainly.

Monobloc vs portable vs split: the quick comparison

Best for: a monobloc suits a single room where you want a permanent, tidy fixture but cannot fit a condenser. A portable suits renters, temporary cooling and anyone who cannot drill the wall. A split is the efficient long-term choice whenever you can site the outdoor unit.

Why a normal split system needs an outdoor unit

Air conditioning does not create cold. It moves heat from inside your home to outside it. The indoor unit absorbs heat from the room into a refrigerant, and that heat then has to be dumped somewhere. On a split system, the outdoor unit is the condenser, and its whole purpose is to release that collected heat into the outside air. Take the outdoor unit away and the heat has nowhere to go.

That is why every split and multi-split has an outdoor box, and why you cannot simply run one indoor head on its own. If you want cooling with no outdoor unit, you need a different design that gets rid of the heat another way. For more on the underlying mechanics, see our explainer on how air conditioning works.

Air conditioning without an external unit: your real options

Monobloc, the single-unit wall-mounted air conditioner

A monobloc puts everything (compressor, condenser and evaporator) in one box that mounts on the inside face of an external wall. Instead of an outdoor condenser, it uses two holes core-drilled through the wall behind or beside the unit: one draws in outside air, the other pushes the warm air out. Neat external grilles cover the holes, so from the street there is no unit to see, just two vents.

The mainstream example is the Olimpia Splendid Unico range, with the Powrmatic Vision, Panasonic RAC Solo, Lux Air KFR-28MB and Qlima units also on sale in the UK. The holes are not tiny: the Olimpia Splendid Unico manual calls for a core bit of at least 162mm to drill each of the two openings, so this is a proper alteration to the wall rather than a pinhole. Most models are reverse-cycle, meaning they heat as well as cool.

Best for: a single room up to around 25m² in a flat, listed building or conservation-area home, where you want a fixed, tidy unit and cannot have a condenser outside.

Portable units

A portable is a monobloc on castors. It sits on the floor and vents its warm air through a flexible hose that you run out of a window (using a window kit) or a wall vent. Nothing is fixed, nothing is drilled, and you can wheel it between rooms.

The catch is efficiency and noise. Most portables use a single hose, which means that as they blow warm air out, they pull warm replacement air into the room from elsewhere in the house, so real-world cooling is weaker than the headline output suggests. They are also the noisiest option, because the whole machine including the compressor sits in the room with you. For renting, temporary cooling, or homes where you cannot drill the wall, they are still the honest answer. Browse the options in our portable air conditioners category, and if a trailing hose is your worry, read our guide to the portable air conditioner without a hose.

Water-cooled internal systems (the niche route)

A small number of specialists offer systems that reject heat into mains water rather than outside air, which lets the whole system stay internal and, in some cases, feed several rooms from one internal condenser. It is a clever answer for a high-spec flat with a water and drainage route, but it is a premium product, with installed prices starting around £4,600 for a single room. For most homes it is overkill; a monobloc or portable does the job for far less.

How efficient (and how noisy) are they?

This is where honesty matters. A monobloc is less efficient than a split. A typical wall monobloc runs at an energy efficiency ratio (EER) of around 3, with the best models reaching energy Class A+, while a modern split reaches a seasonal efficiency (SEER) of roughly 7 to 8.7. In plain terms, for the same amount of cooling a monobloc uses noticeably more electricity than a split would. It still cools the room; it just costs more to run per hour of use.

Outputs are modest too. Wall monoblocs top out at about 3.5kW of cooling, enough for one room, whereas splits scale well past 10kW and can serve several rooms. So a monobloc is a one-room solution, not a whole-home one.

On noise, a monobloc sits between the two extremes. Because the compressor is in the room, it runs at roughly 26 to 34 dB(A) depending on the model and fan speed. That is quieter than a portable, which often exceeds 50 dB(A), but louder than a split's indoor head, which can be as quiet as 19 to 21 dB(A). If near-silence matters, for a bedroom for example, factor that in.

What air conditioning without an outdoor unit costs

As a guide to 2026 UK prices:

• Wall monobloc, unit only: roughly £900 to £2,900. Budget models such as the Olimpia Splendid Unico Easy S2 HP start around £900; mid-range Unico EVO and Powrmatic units sit around £1,500 to £1,850; higher-output Unico PRO, Panasonic RAC Solo and Powrmatic Vision models run from about £2,000 to £2,900.

• Wall monobloc, supplied and fitted: budget roughly £1,500 to £3,000 all-in once you add core-drilling, grilles, condensate drainage and the electrical connection, more for an awkward wall or a dedicated circuit.

• Water-cooled internal system, installed: premium, from around £4,600 for one room.

• Portable unit: typically a few hundred pounds, with no installation cost.

Prices correct as of July 2026 and vary by model, home and installer. Always compare current quotes before budgeting.

Running costs follow the same pattern. At the Ofgem price cap of 26.11p/kWh (1 July to 30 September 2026), a 2.5kW monobloc drawing about 0.8kW of power over an 8-hour day uses about 6.4kWh, which works out at roughly £1.67 a day (0.8kW multiplied by 8 hours multiplied by 26.11p). A more efficient split doing the same job would use less. The cap changes every quarter, with the next change due around 26 August 2026, and from 1 October 2026 VAT on domestic electricity is cut from 5% to 0%, so treat that figure as a snapshot.

To weigh a monobloc against a fitted split properly, our guide to choosing an air conditioning system walks through the decision.

Installing one: DIY or fitted?

Here is a real advantage of the no-condenser route. Because monoblocs and portables arrive sealed and pre-charged at the factory, nobody has to open the refrigerant circuit to fit them, so you do not need an F-Gas registered engineer. That is what makes a split a professional-only job and a monobloc potentially a DIY one. Some retailers sell wall monoblocs specifically as DIY self-install kits that run off a standard 13-amp socket.

Two cautions, though. First, core-drilling two 162mm holes through a solid or cavity external wall is a serious bit of DIY, and getting the fall and sealing right on the grilles matters for weatherproofing and performance. Second, the electrics: a smaller unit may run happily off an existing socket, but any new dedicated circuit is notifiable work under Part P of the Building Regulations and should be done or signed off by a registered electrician. "No F-Gas engineer" does not mean "no rules".

Many people would rather have it done properly in an afternoon. You can compare local installers for a fitted monobloc, an honest opinion on whether your wall suits one, and a tidy job.

Many of these units use R290 (propane), a low-carbon but highly flammable refrigerant. The charge is small and factory-sealed, so it is safe in normal use, but it is a good reason to follow the siting and clearance instructions and never to modify the unit.

Flats, listed buildings and planning permission

Losing the outdoor unit removes the single biggest planning trigger, because there is no external box to worry about for size, siting or the neighbour-noise limit. But "no outdoor unit" does not automatically mean "no permission needed", and some sellers gloss over this.

• Flats and leasehold: drilling through an external wall alters the structure and the exterior of the building, so you will usually need your freeholder's or landlord's permission even with no condenser. Check your lease before you buy. Our guide to air conditioning for flats covers this in full.

• Listed buildings: any external alteration, including two grilles, typically needs listed building consent.

• Conservation areas: external changes can be restricted, so check with your local planning authority first.

• Cooling-only vs reverse-cycle: for a fitted system it is still worth knowing that in England a reverse-cycle unit (one that heats and cools) can qualify as permitted development under rules in force since 29 May 2025, while a cooling-only unit is not covered and generally needs full planning. With no outdoor unit the condenser rules fall away, but the distinction matters if you are also weighing a split.

For the detail, read our full guide to planning permission for air conditioning, and always confirm with your local planning authority before drilling.

A quick word on grants: the £2,500 air-to-air heat pump grant needs an MCS-certified installer and a reverse-cycle unit replacing an existing fossil-fuel or electric heating system, so a self-installed monobloc will not qualify, and portables are excluded from the 0% VAT on fixed heat pumps. Never assume "free air con"; check GOV.UK and Ofgem for current rules. Correct as of August 2026.