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How to vent a portable air conditioner

Updated: 21 October 2026

You have a hose portable, and the worry is the window. A 12,000 BTU monobloc makes heat as well as cold air, and that heat has to leave the room. This is how to vent it on a UK sash, a slider or an outward-opening casement, then what to do with the water. It is not a ranking. Prices stay on the [12000 BTU air conditioner comparison](/hub/cooling/12000-btu-air-conditioner). The limits below come from Appliances Direct, Sealey, Honeywell Air Comfort UK and EcoAir, plus these listings. Your manual wins if it disagrees. Peter F. updated this on 20 October 2026. A qualifying purchase can earn a commission at no extra cost to you.

You have a hose portable, and the worry is the window. A 12,000 BTU monobloc makes heat as well as cold air, and that heat has to leave the room.

Our top picks

XIUNYIE XIUNYIE 12000 BTU portable

Best overall

XIUNYIE XIUNYIE 12000 BTU portable
2.9/10about £456.24
View offer
Midea Midea PortaSplit 12000 BTU

Rank 2

Midea Midea PortaSplit 12000 BTU
8.4/10about £1,099.99
View offer
Air Pro Air Pro AP-E4 12000 BTU

Best value

Air Pro Air Pro AP-E4 12000 BTU
8.0/10about £499.99
View offer
On this page
  1. 1.Why the hose is not optional
  2. 2.Sash, slider and casement
  3. 3.Hose length and bends
  4. 4.Water in the hose and on the floor

Why the hose is not optional

A single-hose portable blows waste heat outdoors. If the hose dumps that air back into the lounge, the compressor heats the space it is trying to cool. No outdoor unit does not cancel the hose. The QINLIGAO bullets say there is no outdoor unit and also tell you to fit a 1.5 m hose. The Air Pro includes a window kit with a stated maximum opening of 125.5 cm. The Midea PortaSplit is a different machine. Reviews describe a separate outdoor section, not this sash-plate hose. Use the portable versus split page rather than stretching a monobloc kit to fit it.

Sash, slider and casement

A slide-bar kit is the usual piece for a sash or a sliding door. Appliances Direct describes fitting that bar in about 15 minutes on the windows it covers. Measure the opening before you trust kit included. The Air Pro's stated maximum width is 125.5 cm. A wider sash can leave a gap the supplied plate never covers. An outward-opening casement often will not take a slide bar. Sealey's SACWK1 instructions describe a hook-and-loop cloth seal for hinged windows, with the tape on the frame, not the glass. If the carton only contains a sash plate, that cloth kit is a separate purchase.
XIUNYIE XIUNYIE 12000 BTU portable

Testsieger

XIUNYIE XIUNYIE 12000 BTU portable
2.9/10about £456.24
View offer

Hose length and bends

Shorter and straighter is the working rule. Appliances Direct puts the hose at about 30–150 cm and asks you not to bend it more than about 30 degrees. EcoAir states 1.5 m as the maximum because a longer duct raises compressor back pressure. Honeywell says extra length can cut cooling and often voids the warranty. If your manual prints a different maximum, follow the manual. Move the unit closer to the window. One Air Pro review says the supplied hose was too short, which is a layout problem, not a reason to join two ducts. A crushed hose adds roar near a bed, which the bedroom page covers.

Water in the hose and on the floor

In cooling mode many portables evaporate condensate and send it out with the exhaust air. The XIUNYIE bullets describe auto-evaporation plus an optional continuous drain. That drain is the planned path when a humid night overwhelms evaporation. Dehumidify mode is different: a tank or a hose is normal, because the job is to pull water out. Check the mode before you assume the machine is broken. A puddle from the case or from a split seal is not that normal drain. Air Pro reviews describe water from the case and from seals, and one buyer had a rear pipe come off. Unplug the unit before you deal with water around a live machine. If water has reached the plug or the controls, leave it off. An R290 circuit must not be pierced to chase a leak.

Common questions

Do you have to vent a 12,000 BTU portable?
Yes, if it is a refrigerant monobloc. The heat from the condenser has to leave the room through the hose. A listing that says no outdoor unit can still require a 1.5 m exhaust hose, which is the QINLIGAO wording. An evaporative cooler with a water tank and no hose is a different product. The Midea PortaSplit uses a separate outdoor section, not this window-plate hose.
Will a sash kit fit a casement window?
Often it will not. A slide bar suits a sash or a slider that can close onto the bar. An outward-opening casement usually needs a cloth seal with a zip, of the kind Sealey describes, with the tape on the frame rather than the glass. If the box only contains a sash plate, measure the leaf first. A gap you can see around the hose is wasted cooling.
Can you add hose if 1.5 m does not reach?
On the guides from Honeywell and EcoAir, no. Extra length raises the load on the fan and the compressor, can reduce cooling and can void the warranty. Appliances Direct's range is about 30–150 cm with a shallow bend. Move the portable closer to the window. A short Air Pro hose is a reason to move the unit, not to join a second duct.
When is a puddle a fault?
Water from the casing, from a failed seal or from a pipe that has come off is a fault. Air Pro reviews describe that pattern, as distinct from emptying a tank. Switch the unit off and unplug it before you mop. If water has reached live parts, leave it isolated. Do not open the refrigerant circuit, particularly on an R290 machine.
Does the Midea PortaSplit use this same hose?
No. It is a portable split. The reviews describe an outdoor section, a connecting line and stacking the two parts. A sash plate and a 1.5 m monobloc hose are the wrong diagram. Site the outdoor section as the manual describes, and do not open the factory-sealed circuit. Do not cover the air inlets, and do not tape the glass.

Related pages

12000 BTU air conditioner buying guide

12000 BTU air conditioner

Quiet 12000 BTU air conditioner for bedroom nights

Best 12000 BTU air conditioner: who each pick suits

Portable vs split air conditioner: which one to buy

Sources

Public UK sources from the research digest. amazon.co.uk prices, stars and review counts are the listing lines for these six products, captured on 19 October 2026. This is not a laboratory test.

  1. GOV.UK: bans on F-gas in new products and equipment (retrieved 20 October 2026)
  2. GOV.UK: qualifications required to work on equipment containing F gas (retrieved 20 October 2026)
  3. GOV.UK: selling F gas or equipment (retrieved 20 October 2026)
  4. legislation.gov.uk: England GPDO Class G (retrieved 20 October 2026)
  5. Planning Portal: planning permission to add air conditioning (retrieved 20 October 2026)
  6. Midea UK: PortaSplit air conditioner (retrieved 20 October 2026)
  7. Trusted Reviews: single versus dual hose air conditioners (retrieved 20 October 2026)
  8. AirConCompare: how to choose an air conditioner in the UK (retrieved 20 October 2026)