Types of Air Conditioning for UK Homes

Air conditioning is still unusual in British homes, but it is spreading fast. An estimated 3% of UK homes currently have air conditioning¹, and in the Winter 2025 official attitudes tracker, 5% of households said they used it². What that growth means in practice is that more households are facing the same question: which of the several quite different kinds of air conditioning actually fits a UK home? The answer starts with how the technology works: heat from the warm air within the area to be cooled is removed and cycled back through the indoor unit as cooled, and possibly cleaned, air³.

The answer matters because the types differ enormously. A portable unit is a plug-in appliance you can buy and wheel into a room the same day. A fixed split system is a permanent installation with an outdoor unit, refrigerant pipework and a legal requirement for a certified engineer. Between and around those sit multi-split systems, ducted systems, ceiling cassettes, floor consoles and through-wall monoblocs, each with its own fitting requirements, costs and rules. This page sets out the range, explains how the machines actually move heat, and covers the planning rules, efficiency standards, running costs and servicing obligations that come with each.

The seven types at a glance

Domestic air conditioning in the UK falls into seven broad categories, and the differences between them are mostly about where the noisy, heat-dumping half of the machine sits and how the cooled air reaches the room.

• Portable air conditioners: a single wheeled box that lives in the room, exhausting hot air through a hose to an open window or wall vent.
• Single split systems: one outdoor unit on the wall or ground, connected by refrigerant pipework to one indoor unit, most often wall mounted.
• Multi-split systems: one outdoor unit serving several indoor units in different rooms.
• Ducted systems: indoor units hidden in a ceiling or cupboard space, delivering cool air through ducts to grilles in several rooms.
• Ceiling cassettes: a flat indoor unit set into a suspended ceiling, blowing air in four directions.
• Floor console units: indoor units standing against a wall at floor level, in the manner of a radiator.
• Through-wall monoblocs: a single unit fitted through an exterior wall, with no outdoor unit and no refrigerant pipework.

The context for all of these is a housing stock built around heating, not cooling. UK homes have several types of heating system: boilers, low carbon heating and electric heating⁸, and boilers remain the most common heating type in UK homes⁹. Air conditioning, by contrast, has historically been a rarity, and the building regulations' notional dwelling specification for a new home assumes no air conditioning provision at all¹⁰. That is changing as summers warm: air temperatures fluctuate between -5°C to 25°C for at least 95% of the year for most UK homes¹¹, and the upper end of that band is where cooling starts to matter. Householders who have lived with an air-to-air heat pump report the cooling as a genuine benefit, since air-to-air heat pumps "offer the added benefit of supplying air conditioning, keeping your home cool during the summer"¹².

For energy independence, the type you choose determines how much of the system you own and control. A portable unit is simply an appliance: no installer, no fitter, no dependence on anything but a socket. A fixed system is a permanent improvement to the house, but one that depends on a certified engineer for installation and servicing, and, in most cases, on the electricity grid for every hour of cooling. Our pillar page on home cooling covers the wider picture, and there are dedicated pages on split air conditioning, multi-split systems, ducted and cassette systems, portable units and through-wall monoblocs.

A fridge lacking its insulated cabinet

Every type of air conditioning on this page works the same way at heart: it is a heat pump, moving warmth from one place to another rather than creating cold. The rules for heat pump systems under the domestic renewable heat schemes state the core requirement plainly: such a system "must use a compressor driven by electricity"¹³. That compressor circulates refrigerant through a closed loop of pipework. Inside the room, the refrigerant evaporates at low pressure and absorbs heat from the air passing over the coil, the same process that makes the back of a fridge cold. Outside, the refrigerant is compressed, releases the heat it collected, and the cycle repeats.

The industry body CIBSE describes the reverse of this process in exactly these terms: a heat pump "when operated in reverse, removes heat in the same way as an air conditioner"¹⁴. That sentence is worth pausing on, because it captures the essential point: an air conditioner and a heat pump are the same machine. The only question is which direction the heat is being moved. An air-to-air system "can also offer cooling"⁷, and most fixed air conditioning sold for UK homes today does exactly that, in both directions.

What this means for the householder is that air conditioning is not like an electric heater, which converts every unit of electricity into a unit of heat and stops there. A heat-moving machine can transfer several units of heat for each unit of electricity it consumes, because the electricity is doing the work of pumping, not the work of heating or cooling directly. That is why the efficiency minimums later on this page are expressed as ratios above 4, and why a fixed split system costs far less to run than the raw wattage of its compressor might suggest. The dependence to note is the refrigerant itself: the circuit is sealed and, by law, must be handled by a certified engineer, so a householder cannot top up, modify or repair it themselves.

Portable air conditioners: the compressor in the room with you

A portable air conditioner is the only type on this list that needs no installation at all. Everything, compressor, condenser, fan and controls, sits in one wheeled cabinet in the room, with a flexible hose carrying the waste heat to an open window, a wall vent or a dedicated hole. That makes it the one option a renter can use, and there is a page on using a portable unit in a rental property.

The price of that convenience is power and noise. Typical portable air conditioners draw 1,000 to 1,500 watts⁴, and the range across the market runs wider still: typically 900 to 2000W, with the higher the BTUs meaning the higher the power¹⁵. On the electrical side, a portable air conditioner can draw up to 9.3 amps¹⁵, which is why the safety advice on appliance ratings is to check what a machine draws before plugging it into an extension lead or a socket shared with other high-draw appliances. A unit at the top of the range can pull up to 2000 W¹⁵, close to the limit of a standard UK socket circuit.

Two practical limits follow from the design. First, because the heat-dumping half of the machine is in the room, some of the noise and some of the heat always stay with you; the fan and compressor are a metre or two from your chair rather than outside the wall. Second, the hose arrangement is inherently leaky: the air being blown out has to be replaced by air drawn in from elsewhere, often through the very window gap the hose occupies. Whether a portable needs venting outside, and how single-hose and dual-hose designs differ, are covered on does a portable air conditioner need venting and single hose vs dual hose portable air conditioners. Drainage is a common question too: most modern units are self-evaporating in cooling mode and need a drain hose only when the tank fills or in dehumidifier mode, as explained on does a portable air conditioner need a drain hose.

Split and multi-split systems: several units of cooling per unit of electricity

A split system takes the noisy half of the machine out of the room. One outdoor unit, mounted on a wall bracket or a ground slab, holds the compressor and condenser; one or more indoor units, usually high on a wall, hold the quiet fan and the evaporating coil. A single-split system has a power rating of 0.8 to 2.5 kW⁵, which covers a single medium-sized room. A multi-split or ducted system has a power rating of 1 to 5 kW⁵, with one outdoor unit feeding indoor units in several rooms; how many indoor units one outdoor unit can serve is covered on multi-split systems.

The efficiency claim in this heading is not marketing: it is the building regulations' own floor. For air conditioning working in cooling mode, the minimum seasonal energy efficiency ratio is 4.0 for existing dwellings and 4.6 for new dwellings⁶. In other words, the law will not accept a fixed system that delivers less than about four units of cooling for each unit of electricity consumed, and a new-build system must do better still. The Welsh consultation version of the same approved document states the identical figures: "For existing dwellings, a minimum of 4.0" and "For new dwellings, a minimum of 4.6"¹⁶.

That is the practical difference between a portable and a fixed system. A portable converts its 1,000 to 1,500 watts of electricity into somewhat less than that in cooling, after hose losses and the heat the machine itself dumps into the room. A split system delivers four to five times its electrical input in cooling, because it is moving heat rather than generating it. The trade-offs are permanence and cost: a split needs an exterior wall, a certified installer, a condensate drain and a hole through the masonry, all covered on air conditioning installation. The indoor unit styles vary too: wall mounted is the commonest, but floor console units sit at skirting level like a radiator, and ceiling cassettes sit flush in a suspended ceiling, options compared on ducted vs multi-split air conditioning.

Reversible air conditioning: the same machine, run backwards

Most fixed air conditioning sold in the UK is reversible, and this is where the types converge with heat pumps. As CIBSE puts it, a heat pump "when operated in reverse, removes heat in the same way as an air conditioner"¹⁴: the same circuit, the same compressor, the same refrigerant, with the flow direction reversed so that the outdoor coil becomes the absorber and the indoor coil the releaser. An air-to-air system "can also offer cooling"⁷, and householders who have one value it in both seasons, since air-to-air heat pumps "offer the added benefit of supplying air conditioning, keeping your home cool during the summer"¹².

The heating side is more capable than many people expect. Cold-climate models exist: as Which? explains, "you can get a heat pump that's designed to work down to minus 25 degrees"¹⁷. Against the UK's actual climate, where air temperatures fluctuate between -5°C to 25°C for at least 95% of the year for most UK homes¹¹, that is a wide margin. A reversible unit can therefore be a household's heating system as well as its cooling system, which is why the planning rules in the next section hinge on whether a system provides heating.

For independence, a reversible air conditioner is one of the few appliances that reduces a household's dependence on gas rather than adding to its electricity use. Many homes in Great Britain are gas-heated¹⁸, and a reversible unit that heats efficiently in winter displaces gas burned in a boiler with electricity moved as heat. The dependence that remains is the grid and the electricity supplier, unless the household generates its own power, a combination explored on running air conditioning on solar panels. The comparison with plug-in electric heaters is stark: there are four types of electric heater, fans, convectors, oil or oil-free radiators and halogen heaters¹⁹, and every one of them turns electricity into heat at a ratio of one to one, where a reversible air conditioner delivers several times that.

What it costs to run: 26 to 39p hourly for a typical portable

What air conditioning costs to run depends chiefly on its power draw and how many hours a day it works. The figures that follow are for portable units, the most commonly bought type, and they give a realistic picture of a hot spell.

A typical portable air conditioner of 1,000 to 1,500 watts "can cost around 26 to 39p per hour, roughly 14 to 20 times more than a fan"⁴. Uswitch's guide, calculated on the July 2026 Ofgem price cap of 26.11p per kWh, puts the same class of machine at £0.20 to £0.39 per hour⁵. The two figures differ slightly because they were calculated at different times and price caps, but they agree on the order of magnitude: tens of pence an hour, not pounds.

For a full week of heavy use, Uswitch's analysis priced a 1 kW portable unit at £13.37 a week on the cheapest fixed tariff and £16.70 a week on predicted July rates, both on the basis of average use of 9.1 hours a day for seven days²⁰. Those weekly figures are the honest picture of a heatwave: a portable unit run hard through hot weather costs real money, though far less than the equivalent hours of an electric heater would, and the per-hour comparison with fans is covered on air conditioning vs fans.

A fixed split system's running costs are lower per unit of cooling because of the efficiency minimums described above, but they depend on room size, insulation and how many hours the system runs, which is why the table above gives no single figure for them. Sizing matters too: an undersized unit runs constantly without reaching temperature, and an oversized one cycles wastefully, a trade-off explained on air conditioning sizing. Full cost breakdowns, including purchase and installation, are on air conditioning cost and air conditioning running costs.

Efficiency ratings: SEER 4.0 in existing homes, 4.6 in new builds

The efficiency of air conditioning in the UK is not left to the market. The building regulations' approved document sets minimum seasonal energy efficiency ratios for cooling mode: "For existing dwellings, a minimum of 4.0" and "For new dwellings, a minimum of 4.6"⁶. The Welsh consultation version carries the same two figures¹⁶. In plain terms, a fixed system in an existing home must deliver at least four units of cooling for every unit of electricity it draws over a season, and a system in a new-build home must deliver at least 4.6.

Those ratios are the reason the running costs in the previous section are as low as they are. A machine with a seasonal efficiency ratio of 4.0 uses a quarter of the electricity that a one-to-one electric appliance of the same cooling output would need. The rating on the label, and the difference between SEER, SCOP and the A-to-A+++ energy labels, is explained on air conditioning efficiency ratings.

Two cautions apply. First, these minimums apply to fixed systems; a portable unit is a plug-in appliance and is rated under the ordinary appliance labelling scheme, which is why the electrical safety guidance discusses portable air conditioners in terms of their watts and amps, up to 2000 W and up to 9.3 A, rather than any seasonal ratio¹⁵. Second, the ratio is measured under standard conditions: real-world performance depends on the quality of the installation, the length of the pipework run and how well the room is sealed, which is one reason the installation page matters as much as the specification table. For comparison, every type of plug-in electric heater, fans, convectors, oil or oil-free radiators and halogen heaters¹⁹, is capped by physics at an efficiency of one unit out per unit in, so anything rated above 4 is in a different category altogether.

Planning permission: cooling-only units need an application

This is the rule that catches most people out. Adding air conditioning to your home may be considered permitted development, meaning no planning application is needed, provided all the limits and conditions set in the legislation are met²¹. But the rights only apply if the system provides a heating function, including if it can provide both heating and cooling²¹. A cooling-only system falls outside the permitted development rights and requires a planning application²². In practice this pushes most households towards reversible systems, which is one reason the heating capability described earlier matters legally as well as financially.

The permitted development rights for air source heat pumps, which include air-to-air systems, carry further conditions. Development is not permitted unless the system complies with the MCS Planning Standards or equivalent standards²³. The outdoor unit must not exceed stated volumes: 1.5 cubic metres including any housing for a dwellinghouse, and 0.6 cubic metres for a block of flats²⁴. Development is not permitted if a wind turbine is installed on the same building or within the curtilage²⁵, nor if the dwellinghouse or block of flats is a listed building, or the unit would be installed on land within the curtilage of one²⁵.

Protected areas and local restrictions bite too. If your home is in a protected area such as a Conservation Area then permission will be required, and if you live in a listed building then listed building consent is required²². Even where the national rights exist, they can be withdrawn locally: permitted development rights may be removed through a planning condition, an Article 4 Direction or other restriction, as Cornwall Council's guidance for its own area sets out²⁶. The rules also differ between nations: the legislation cited here is England's, and Northern Ireland has its own schedule, which covers the installation, alteration or replacement of a ground or water source heat pump within the curtilage of a building other than a dwellinghouse or block of flats²⁷. Scotland and Wales have their own frameworks, covered on the Scotland, Wales and Northern Ireland pages, with England's on air conditioning planning permission in England.

Separately from planning, building regulations apply. The installation of air conditioning must comply with building regulations²², and putting in a fixed air-conditioning system is listed among the alterations for which building regulations approval is needed²⁸. A portable unit, having no fixed installation, involves neither.

Installation, servicing and lifespan

A fixed air conditioning system is not a DIY job, for one legal reason above all: the refrigerant circuit. Handling refrigerant requires an F-Gas certified engineer, a requirement explained on F-Gas rules for home air conditioning, and the MCS Planning Standards condition on permitted development reinforces the case for a certified installer²³. There are pre-charged and easy-fit systems marketed for self-installation, but the legal and practical position is on DIY air conditioning installation.

Once installed, a fixed system needs the same annual attention a boiler does. The Health and Safety Executive "strongly advises that all gas appliances, flues and pipework should be installed, regularly maintained and serviced" at least annually by a Gas Safe registered engineer²⁹, and the same annual rhythm is the sensible benchmark for air conditioning, whose filters and coils also collect dust. Household-level checks, like bleeding radiators at least once a year³⁰, are the heating-side equivalent of the filter cleaning an air conditioning owner should do every few weeks in season, covered on air conditioning maintenance.

Larger systems carry statutory inspection duties. The regulations apply to air-conditioning systems "with an effective rated output of more than 12kW"³¹, well above the domestic range, but the inspection interval they set is instructive: ranging "from three years for poorly maintained and inefficient systems up to five years for those systems that are well" maintained³². Maintenance is not optional padding; it is the difference between a system inspected every five years and one pulled up every three.

On lifespan, the evidence is encouraging. On average, an air source heat pump lasts up to 20 years⁷, and a well installed split system is the same class of equipment. Twenty years of cooling and, for reversible units, heating, is the horizon against which the purchase and installation cost should be judged.

Warranty: what to check before you buy

There is no UK-wide standard warranty for domestic air conditioning: terms are set by each maker and often extended or restricted by the installer and by registration requirements, so the warranty is a point of comparison between specific products rather than a fixed feature of any type. The figures quoted in marketing, including extended terms tied to loyalty or registration schemes, are the maker's own statements and should be read as such, alongside the date the offer was published.

What a householder can rely on structurally is certification. The MCS Planning Standards condition attached to permitted development²³ means a certified installation is not merely a quality mark but part of the legal basis on which the outdoor unit sits on your wall without a planning application. MCS also operates a consumer protection scheme for heat pump installations⁷, which is the closest thing the sector has to an independent backstop when an installation goes wrong.

Three checks are worth making before signing anything. First, whether the warranty requires an annual service by a qualified engineer, on the annual rhythm the HSE advises for gas appliances²⁹, since a skipped service is the commonest condition that voids cover. Second, whether the warranty covers both parts and labour, and for how long each. Third, whether the installer's own guarantee sits behind the maker's, and what happens to both if either firm ceases trading. A warranty is only as durable as the company behind it, and a five-year promise from a firm that disappears in year two is worth nothing, whatever the headline term said.