Fixed air conditioning vs portable air conditioners

The short answer

If you will use cooling for more than a few days a year, in a bedroom or home office, a fixed split system is the better choice. If you rent, use the room only occasionally, or can't put an outdoor unit on the building, a portable is the practical option.

The two differ in where the noisy, hot part of the machine sits. A split system puts the compressor and condenser in an outdoor unit, so only a quiet fan unit is in the room. A portable puts everything in one box on your floor and pushes the waste heat out through a hose in a partly open window.

Why the window hose matters

The hose is behind most complaints about portable units. To vent it, you need a gap in the window. Warm outside air leaks back into the room through that gap, and many single-hose portables also pull room air out through the hose, which draws more warm air in through doors and gaps. The unit spends part of its effort cooling air it has let in.

Window kits help, but they rarely seal fully, especially on sash windows common in older Leeds terraces. A dual-hose portable, which draws outside air in through one hose and sends it back out through the other, handles this better.

The types on offer

Portables come in a few forms. A single-hose unit is the cheapest and most common. It draws air from the room to cool its condenser and blows that air out of the hose, which pulls warm air into the room from elsewhere. A dual-hose unit takes outside air in through one hose and returns it through the other, so it doesn't depressurise the room in the same way. Evaporative coolers, sometimes sold as air coolers, aren't air conditioners at all. They blow air over water and add humidity, which does little in a muggy Leeds summer.

There are also through-wall units with no outdoor unit, where the whole machine sits on the inside of an outside wall and vents through two holes. They avoid an outdoor unit but are louder in the room than a split, and they still need holes drilled through the wall.

Fixed systems are usually a single split, with one indoor and one outdoor unit, or a multi-split, where one outdoor unit serves two or more rooms. The indoor unit is most often a high-wall unit, but floor-standing units and ceiling cassettes are options too. Our single split vs multi-split guide explains the choice.

When you compare, compare like with like. Look at the cooling output in kW, the rated power input, the sound level on the setting you will use and whether the unit heats. Data sheets for both portables and splits give these figures.

What each costs to buy and fit

Checkatrade's May 2026 cost guide puts a portable air conditioner at about £350, and a fitted single split at about £750 for equipment plus £1,150 for labour and £400 to £700 for electrical work.

Worked example: the up-front gap. The fitted split comes to 750 + 1,150 + 400 = £2,300 at the lower electrical figure, or £2,600 at the higher. Take the £2,300 figure: 2,300 - 350 = £1,950 more than the portable, or about 6.6 times the price (2,300 / 350 = 6.57).

VAT works in the fixed system's favour for homes. HMRC's VAT Notice 708/6 zero-rates the installation of an air-to-air heat pump in a home until 31 March 2027. A portable bought in a shop carries the standard 20% VAT, since there is no installation. Our partner installers apply the 0% rate to domestic installs.

What each costs to run

Running cost depends on the power each unit draws. Check the rated power input on the data sheet of both models.

At Ofgem's October 2026 price cap, electricity averages 26.32p per kWh by Direct Debit. Say a split averages 0.6kW in a bedroom overnight, and a portable cooling the same room draws an assumed 1.0kW because of the window gap. Over a 6-hour night, the split uses 3.6kWh, which costs 94.8p. The portable uses 6kWh, which costs £1.58. Over 30 nights that is £28.44 against £47.40, a difference of £18.96 a year. These power figures are assumptions for illustration, so do the sum with the real data sheets.

On those numbers, the portable's saving at the till would take decades to be overtaken by running costs, so don't choose a split purely to save on bills. Choose it for comfort, noise and heating.

Noise in the room

Noise is where the difference is easiest to notice. With a portable, the compressor is in the room with you, and its sound changes as it cycles on and off. With a split system, the compressor is outside, and the indoor unit is a fan. Manufacturers publish sound pressure levels for both types, so compare the figures on the data sheets, measured on the same setting, before you buy.

Decibels are a log scale, so a sound 10 dB higher is ten times the sound energy and is heard as roughly twice as loud. A small difference on paper can be a clear difference at 2am. With a split, also think about your neighbours. The outdoor unit has to meet the 37 dB(A) limit at their nearest habitable room window to qualify for permitted development, and the installer should show you the calculation.

For a bedroom, check the indoor unit's quietest setting. Our guide to bedroom air conditioning and our guide to air conditioning noise go into the numbers in more detail.

Heating in winter

Nearly every split system fitted in UK homes is an air-to-air heat pump that heats as well as cools. At October 2026 rates, a unit with a SCOP of 4.0 makes heat for 26.32 / 4 = 6.6p per kWh. Many portables don't heat at all. Those that do often use a simple electric element, which makes heat at the full 26.32p per kWh. If you want a unit to warm a home office from October to April, a split is the clear choice.

Planning, flats and tenancies

A portable needs no permission. You plug it in and put the hose out of the window.

A split's outdoor unit is fixed to the building. On houses in England it can usually be fitted under permitted development, as long as it is 1.5 cubic metres or smaller and meets the 37 dB(A) noise limit at the nearest neighbour's habitable room window. Leeds has 80 conservation areas, where the unit can't go on a wall facing a road under those rules. Flats aren't covered by permitted development for houses, and they need the freeholder's consent. Tenants need the landlord's written agreement.

That is why portables are common in the flats around Leeds city centre, Holbeck and the student areas of Headingley and Hyde Park. If you rent there, or the building won't allow an outdoor unit, a portable may be your only realistic option.

When a portable makes sense

These are the situations where a portable is the better buy.

• You rent and can't alter the building.
• You need cooling for a spare room a few days a year.
• You live in a flat where no outdoor unit position is possible or allowed.
• You want a short-term fix while you plan a fitted system.

When to go fixed

If you would use a portable for more than a few weeks each summer, struggle to sleep in a hot room, or work from home in a room that overheats, a split system is the better experience. It holds the set temperature, keeps the compressor noise outside, needs no window open, and heats the room in winter.

Leeds has a lot of homes where that matters. The council counts about 19,500 pre-1919 back-to-back houses in the city, many with attic bedrooms that trap heat and have no through draught. A portable in that room fights a warm roof all evening with a window open. A split unit sized for the room does the job with the window shut.

Fitting a split needs an installer certified for F-gas work, since the refrigerant is a fluorinated gas covered by the F-gas rules. Our partner installers are MCS certified.

Sources

• Checkatrade, Air conditioner installation cost
• Ofgem, Energy price cap unit rates
• HMRC, VAT Notice 708/6
• GOV.UK, F gas in refrigeration and air conditioning
• Energy Saving Trust, Air to air heat pumps
• GPDO 2015, Schedule 2 Part 14 (permitted development for heat pumps)
• Leeds City Council, Conservation areas
• Leeds City Council, Leeds Housing Strategy