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How to vent a portable air conditioner

Updated: 21 October 2026

The unit is in the room, the hose is still in the box, and the bedroom is not getting colder. That usually means the heat is coming straight back in through the gap around the hose. This is how to vent a portable air conditioner on a UK sash, sliding, or casement window, using the kits and the review complaints in our [mobile air conditioning units comparison](/hub/cooling/mobile-air-conditioning-units). Peter F. did not fit these units in a lab. A qualifying purchase can earn a commission at no extra cost to you. You cannot judge the compressor until the seal exists. If the only workable exit is a hole in the wall, this stops being a portable.

The unit is in the room, the hose is still in the box, and the bedroom is not getting colder. That usually means the heat is coming straight back in through the gap around the hose.

Our top picks

DUXMM DUXMM 9000 BTU portable

Best overall

DUXMM DUXMM 9000 BTU portable
2.4/10about £435.98
View offer
iCAN iCAN 9000 BTU 5-in-1

Rank 2

iCAN iCAN 9000 BTU 5-in-1
7.0/10about £399.99
View offer
Air Pro Air Pro AP-E3 7000 BTU

Best value

Air Pro Air Pro AP-E3 7000 BTU
6.7/10about £324.99
View offer
On this page
  1. 1.Why the hose is not optional
  2. 2.Match the kit to the window
  3. 3.Fit it so the unit can work
  4. 4.When to stop and change the plan

Why the hose is not optional

A one-hose portable cools by dumping heat outside. If the hose hangs in an open sash with a gap all round, the unit pulls that heat, and outdoor air, back in. Ideal Home’s kit guide says that without a sealed exit you are recirculating the exhaust. GOV.UK’s hot-weather advice is to keep windows closed while air conditioning is running, which only works if the hose exit itself is sealed. You cannot judge the compressor until that seal exists. A bedroom still at 24°C, which one Air Pro 7,000 BTU reviewer reported after an hour, might be a capacity limit, a leaky kit, or both. Capacity and price sit on the portable air conditioner buying guide. The DUXMM bullets say the hose must go outdoors.

Match the kit to the window

A rigid panel suits a sash and a vertical slider. A zipped fabric seal suits a casement and a tilt-and-turn window. Measure the opening, not the glass. Air Pro bullets say the box includes kits for sliding and hinged windows. Reviews on the 7,000 BTU model say the supplied kit fails on casement windows and on opening doors, and some buyers received only one kit. If yours is a side-hinged UK casement, plan on a fabric seal even if the listing says hinged. The iCAN bullets quote 17–53 inches. The attributes say a maximum of 53 cm. Fifty-three inches is about 135 cm, so measure in centimetres before you force a panel. The DUXMM line has a hose and no window panel. The tedheve included line is a power cord, which is not a venting kit.
DUXMM DUXMM 9000 BTU portable

Testsieger

DUXMM DUXMM 9000 BTU portable
2.4/10about £435.98
View offer

Fit it so the unit can work

Keep the hose short and straight. Ideal Home suggests about 50–60 cm between the cabinet and the window, so the unit stands near that opening. Do not lengthen the hose with a reducer or squash the diameter. An electriQ manual, used as a typical UK instruction rather than a manual for these ASINs, says not to reduce the hose diameter. Close the door. A single-hose unit pulls replacement air through gaps, so an open door feeds it from the landing. If the unit arrived on its side, stand it upright first. The DUXMM bullets say 24 hours, so the compressor oil can settle. Then use a UK 13 A socket, BS 1363, on the lead that came with the unit. Give the sealed room an hour before you decide whether the limit is the seal, the BTU, or the glass.

When to stop and change the plan

Do not vent into a corridor, a loft hatch, or another bedroom. Do not drill a wall, a listed window, or a rented frame to make the kit fit. That is the moment this stops being a portable. A new socket is an electrician’s job, not an extension reel. iCAN reviews say the instructions forbid an extension lead and mention fire hazards, and wattage is not printed, so you cannot check a reel against a missing number. If the lead will not reach, use the window-side socket or have one fitted. If a fabric seal still will not close the opening, a hose portable is the wrong machine. A porta-split or a fixed split then moves the compressor outside, which the portable versus split page sets out.

Common questions

Can I run it with the hose hanging in an open window?
You can switch it on, and the room is unlikely to settle. The gap around an unsealed hose lets the exhaust and the outdoor air back in, so the compressor is reheating the space it is trying to cool. Use a panel or a fabric seal that closes the opening, and shut the other windows while it runs.
Which kit suits a sash, and which suits a casement?
A rigid panel is the usual kit for a sash or a vertical slider. A zipped fabric seal is the usual kit for a casement or a tilt-and-turn window. Measure the opening, not the glass. Air Pro reviews say the included kit often fails on hinged windows even when the bullets mention them, so a casement may need a seal you buy separately.
What if the Air Pro kit does not fit hinged windows?
Treat that as a kit problem, not as proof the compressor is faulty. Reviewers of the 7,000 BTU model describe casement windows and opening doors as a poor fit, and some received only one kit. A fabric seal cut to the opening is the household fix. Forcing a sash panel into a hinged frame leaves a slot down the side.
How long should the hose be?
Short and straight. Ideal Home’s figure is about 50–60 cm between the unit and the window, which means the cabinet stands close to that opening. Reviewers of the Air Pros and the iCAN call the supplied hose short. Do not add a narrower extension. A longer coiled hose keeps heat in the room.
The iCAN listing says both 53 cm and 17–53 inches. Which do I measure?
Measure your sliding opening in centimetres, then compare it with both printed limits. The bullets say 17–53 inches for horizontal and vertical sliders. The attributes say a maximum of 53 cm wide and 53 cm high. Those are different sizes. If your opening is outside the tighter line, do not assume the tool-free claim still applies.
What if there is no socket near the window?
The lead has to reach a 13 A socket without an extension if the instructions forbid one, which a review says the iCAN manual does. Do not run a reel across the floor for a compressor load you have not checked. Ask an electrician about a new socket, and ask the landlord first if the flat is rented. A damaged cable is a stop, not a tape repair.

Related pages

Portable air conditioner for a bedroom

Mobile air conditioning units

Best portable air conditioner UK in this comparison

Portable air conditioner buying guide for UK rooms

Portable air conditioner vs split system in the UK

Sources

Public UK sources used for this page on 20 October 2026. Prices, stars and review counts are the amazon.co.uk figures in this comparison. Stated room sizes and decibel lines were not treated as a lab test.

  1. GOV.UK: bans on F-gas in new products and equipment (retrieved 20 October 2026)
  2. legislation.gov.uk: Regulation 626/2011 Annex II (retrieved 20 October 2026)
  3. GOV.UK: Beat the heat, staying safe in hot weather (retrieved 20 October 2026)
  4. NHS: Heatwave, how to cope in hot weather (retrieved 20 October 2026)
  5. Which?: how to buy an air conditioner (retrieved 20 October 2026)
  6. Ideal Home: portable air conditioner window kits explained (retrieved 20 October 2026)
  7. electriQ: portable air conditioner manual (retrieved 20 October 2026)
  8. amazon.co.uk: Mobile Air Conditioners bestsellers, 19 October 2026 (retrieved 20 October 2026)