Another heatwave is coming — here's our guide to buying a portable air condition

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We’re still recovering from last week’s UK heatwave, which saw record June temperatures of 37.3°C and health warnings across the country.

Now, we’re about to do it all again. Another heatwave is due to come, with highs of 32°C predicted across several days next week.

If you missed out on buying a portable aircon unit last time around, now is the time to get organised (and save yourself from joining the queues outsied the likes of Lidl and Aldi).

Metro is here to help you figure out this new world of exhaust hoses and BTU calculators, with our easy guide to buying a portable aircon unit and if they are actually worth having.

Air conditioners remove the heat from your room, leaving the indoor air cooler. But, there are two types of portable air conditioners. A ‘single hose’ and a ‘dual-hose’.

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Katie Lillywhite, air treatment expert at AO.com tells Metro: ‘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 conditions have a lot more power – one hose to pull in outdoor air and the other to vent this back out.’

Portable aircon units look a bit bonkers, as you need to put the exhaust hose outside via a vent or in most cases, a window.

Jamie Hillard, of Heatable.co.uk, tells Metro his tips for installation.

‘Installation is key and 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 come with a kit, or you can by window sealing kits for portable air conditioners online, with heatershop selling them for only £19.98. You can also find them on Amazon.

But one Metro reader has resorted to ‘sealing’ the gap with a giant bit of taped plastic sheeting, noting that the fitting kits are ‘quite fiddly’. She says the result is imperfect, but the room still gets significantly cooler.

Figuring out what you need for your house depends on various factors such as the room size and height, the size and condition of the windows, the insulation for the house, the direction the room faces and even the type of room. For example, a conservatory or loft will need more strength than a bedroom of similar size.

‘A really common mistake is buying an undersized unit and if the unit is too small, it will run almost continuously, using more electricity but still struggling to bring the room temperature down,’ says Jamie.

To find the best option, you need to use a BTU calculator, which stands for ‘British Thermal Unit’ and this measures how much energy something has.

Glow Green have a helpful chart for figuring out what BTU you need.

‘Running costs depend on the size of the space, insulation, glazing, solar gain, tariff, and how aggressively the system is used,’ Jamie says.

‘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.

Doing the maths on that, using an electricity calculator, it is on average £0.06 per 10 minutes, which per hour is 36p or £8.64 per day, though it is unlikely you would run it 24 hours.

‘Homeowners can reduce running costs by 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,’ Jamie recommends.

The AEG Comfort 6000 Air Conditioner is a smart portable model designed to keep small to medium-sized rooms cool and comfortable during hot weather. With 9,000 BTU of cooling power, it can effectively cool spaces up to around 21m², while also offering fan and dehumidifying modes for added versatility. It features Wi-Fi connectivity, allowing you to control it remotely via your smartphone, alongside an LED display, auto fan function and an integrated CleanAir filter designed to help remove allergens from the air. Its portable design with wheels means it can be moved easily from room to room as needed.

The Logik LAC07C25 Portable Air Conditioner & Dehumidifier is a compact two-in-one unit designed to cool and refresh rooms during hot weather. It features a 323m³/h airflow rate, helping to cool spaces quickly, while the built-in dehumidifier function helps tackle excess moisture and stuffiness. Other handy features include a 24-hour timer, remote control, digital display and auto-defrost technology, plus wheels and a carry handle so it can be moved easily from room to room.

The De’Longhi Pinguino AP98 GentleJet is a premium 3-in-1 portable air conditioner, fan and dehumidifier designed for larger rooms. With 11,500 BTU of cooling power, it uses the brand's GentleJet airflow technology to distribute cool air more evenly and avoid harsh draughts, while Eco RealFeel technology automatically balances temperature and humidity for greater comfort. It also features a quiet night mode, three fan speeds, a 24-hour timer, remote control, and an energy-efficient A+ rating, making it a powerful option for keeping your home cool during heatwaves.

The Meaco MeacoCool MC12000CHR Pro Smart is a versatile 3-in-1 air conditioner, heater and dehumidifier designed to keep your home comfortable all year round. With 12,000 BTU of cooling power, it can heat, cool and remove excess moisture from the air, while smart app connectivity lets you control it from your phone or via Alexa, Google Home and Siri. It also features a quiet Sleep Mode, three fan speeds, a 24-hour timer and energy-efficient heat pump technology, making it a practical choice for bedrooms, living rooms and home offices.

The Bush 9K Air Conditioner is a portable unit designed to keep smaller rooms cool and comfortable during warm weather. It offers four modes – auto, cooling, fan and dry (dehumidifier) – so you can adjust it to suit the conditions, while the 9,000 BTU output is suitable for rooms up to around 18m². It also features a 24-hour timer, sleep mode, LED display and remote control, plus castor wheels to make it easy to move from room to room.

While portable air conditioning units can be done on the cheap, they aren’t always eco-friendly. Like most tech, there are eco mode options and energy ratings. Plus, if you have solar panels, you can power your units that way. But even if you cannot, Andrew Sissons, the sustainable future director at the charity Nesta, says people shouldn’t feel guilty for using them, acknowlidng they are a ‘last resort’ for many people.

Additionally, Nicole Miranda, a sustainable cooling researcher and carbon reduction manager for the University of Oxford, notes that they can be vital in keeping vulnerable people safe in dangerous weather.

Though Earth.org do report that air conditioners are worsening global warming, they advise setting them to 26°C instead 24°C, which consumes around 30% less energy. They reccomend regular cleaning and replacing of the filter too so it does not use more energy, and opting for models with a high Seasonal Energy Efficiency Ratio (SEER).

Though the upfront cost will be a few hundred pounds, and you could be spending approximately up to £8 a day, hot weather can cause dehydration, overheating and heatstroke.

According to the head of the World Health Organization (WHO), the heatwave in Europe has already been linked to 1,300 deaths.

People over 65, babies and children under 5, and those with pre-existing health conditions are espiecally vulnerable.

Steve Charnock, Audience Writer for Metro, who recently bought a 9,000BTU Ariston unit from B&Q for £225, says he had his on ‘constantly’ all of last week, and claims it ‘pretty much saved my life’.

Though, he notes ‘I’ll find out next month if it’s also pretty much bankrupted me’ refencing the daily running costs.

But in comparison, according to Checkatrade, an average, a 12000 BTU wall-mounted unit costs around £750, plus £1,150 for installation and air conditioning engineers typically charge around £280 – £720 per day.

So a portable air conditioning unit is far cheaper and keeps you cool, sane and most importantly safe.

Put a bottle filled with ice and a tablespoon of salt into your freezer, and the salt will help the freezing point of the water go even lower, creating colder ice.

Once you’ve done that, put the bottles in front of the fan.

As the ice melts, the breeze from the fan will pick up the cool air coming from the ice’s surface, recreating a cool breeze, similar to an air conditioning unit.

Plus, a room will stay cooler if curtains and blinds are closed; even better if they’re the blackout variety.

An open window will also let hot air into the house, which, if you have a fan on the go, completely defeats the point.