With a third UK heatwave hitting this week, portable air conditioning units are in high demand after June's record 37.3°C temperatures caused sell-outs at Lidl and Aldi. While discount supermarket units remain unavailable, several models are still in stock online with fast delivery or in-store collection options.
How portable air conditioners work
Portable air conditioners remove heat from a room, but come in two types: single hose and dual hose. Katie Lillywhite, air treatment expert at AO.com, explains: "Single hose air conditioners have one hose to vent hot air from the appliance. This works by drawing air from your room, cooling it through its system then venting this out. They lack a bit of power to cool particularly hot rooms. Dual hose air conditioners have a lot more power – one hose to pull in outdoor air and the other to vent this back out."
Installation tips for portable ACs
Proper installation is crucial. Jamie Hillard of Heatable.co.uk advises: "The exhaust hose must be sealed properly at the window to prevent warm air from coming back in. The exhaust hose needs the shortest, straightest route possible to the outside. Long, kinked, or poorly positioned hoses reduce performance because the hot exhaust air can radiate heat back into the room. The window opening also needs to be sealed properly. A proper window sealing kit or rigid panel makes a noticeable difference." Most units include a kit, or you can buy window sealing kits online from heatershop for £19.98 or on Amazon.
Choosing the right BTU for your room
Selecting the correct BTU (British Thermal Unit) rating is essential. Jamie warns: "A really common mistake is buying an undersized unit. If the unit is too small, it will run almost continuously, using more electricity but still struggling to bring the room temperature down." Glow Green provides a helpful chart: 100–150 sq. ft. / 9–14 sq. m. requires 8,000 BTU; 150–250 sq. ft. / 14–23 sq. m. needs 9,000 BTU; 250–300 sq. ft. / 23–28 sq. m. requires 10,000 BTU; 300–350 sq. ft. / 28–33 sq. m. needs 12,000 BTU; 350–400 sq. ft. / 33–37 sq. m. requires 14,000 BTU; 400–450 sq. ft. / 37–42 sq. m. needs 18,000 BTU; and 450–650 sq. ft. / 42–60 sq. m. requires 25,000 BTU.
Running costs and energy efficiency
Running costs vary based on room size, insulation, glazing, solar gain, tariff, and usage. Jamie notes: "The biggest mistake is setting the target temperature too low. Trying to cool a room to 18°C during a hot spell will use far more electricity than maintaining it at around 22–24°C. For portable AC units, many models are in the 1–1.5kW electrical input range when running." On average, that equates to £0.06 per 10 minutes, 36p per hour, or £8.64 per day if run continuously. To reduce costs, Jamie recommends closing blinds on south- and west-facing windows, keeping windows shut during the hottest part of the day, and cooling rooms before they become overheated.
Portable air conditioner models in stock
Bush 9K Air Conditioner – £375. 9,000 BTU output suitable for rooms up to 18m². Features four modes (auto, cooling, fan, dry), 24-hour timer, sleep mode, LED display, remote control, and castor wheels.
Bush 6.5L Vortex Blade Air Cooler – £85. 2-in-1 air cooler and humidifier with 6.5-litre water tank, three fan speeds, three operating modes, automatic oscillation, and reusable ice packs. Suitable for rooms up to 25m².
Bush 4L 2-in-1 Air Cooler and Humidifier – £110. Evaporative cooling with 4-litre water tank, three fan speeds, three cooling modes, 60-degree oscillation, two ice packs, remote control, and seven-hour timer.
Meaco Cool MC 8000CHBTU Air Conditioner – £380. 8,000 BTU with heating, cooling, dehumidifying, and fan modes. Suitable for 16–26m² rooms. Features A-rated energy efficiency, app connectivity, remote control, 24-hour timer, castors, and window kits.
Meaco 14000BTU Air Conditioner – £500. 14,000 BTU for larger rooms (25–35m²). Four modes (Cool, Dry, Fan, Sleep), three fan speeds, 24-hour timer, humidity reduction, window kit, exhaust hose, castors, and A-rated energy efficiency.
Environmental impact and safety
While portable ACs can be energy-intensive, eco modes and high SEER ratings help. Andrew Sissons, sustainable future director at Nesta, says people shouldn't feel guilty for using them as a "last resort." Nicole Miranda, sustainable cooling researcher at the University of Oxford, notes they can be vital for vulnerable people. Earth.org advises setting the thermostat to 26°C instead of 24°C to consume 30% less energy, and regular filter cleaning. The WHO has linked Europe's heatwave to 1,300 deaths, with over-65s, under-5s, and those with pre-existing conditions most at risk.
Are portable air conditioners worth it?
Despite upfront costs of a few hundred pounds and up to £8 per day running costs, portable ACs are far cheaper than wall-mounted units, which cost around £750 plus £1,150 installation. Steve Charnock, Audience Writer for Metro, bought a 9,000BTU Ariston unit from B&Q for £225 and says it "pretty much saved my life" during last week's heatwave, though he jokes about potential bankruptcy from running costs.
Cheap cooling alternatives
If aircon isn't an option, freeze a bottle filled with water and a tablespoon of salt (salt lowers freezing point), then place it in front of a fan. Close curtains and blinds, especially blackout varieties, and keep windows shut during the hottest part of the day to keep rooms cooler.
