NOW is the time to buy a portable air conditioner: here's what you need to know

It's not often we get to say it in this country (T3 is based in the UK) but it is getting seriously hot. In fact across much of the northern hemisphere, you can feel the temperature rising. We can see from our readership data that lots of you are rushing to buy fans but in the last 2 years there's been a new development: British people are buying air conditioning. I actually bought a portable air con seven years ago and sure, for the first few years it didn't get much use – and it still has no purpose in the winter months. In summer, however, I would no longer live without it.

I'm a big fan of fans. I used just about every Dyson fan that's ever been made and a bunch of Meaco ones too – I didn't buy them, I've just accumulated them via doing this job. Fans are great for what people traditionally think of as good British weather, which is to say 'quite warm'. Temperatures in the low 20s: ideal for watching cricket, sipping Pimm's or visiting Margate, but still keeping your upper lip stiff. 

In recent years, however, we are consistently seeing the heat rising into the high 20s and even low 30s – that even happened in Northern Ireland last week, which is like Hell, er, freezing over. That's around 90ºF if you're old-fashioned or American. And that is hot with a capital H. 

At those temperatures, a fan just does not cut it. They just move the hot air around. Nothing else really works like a portable air conditioner. We have a guide to keeping your house cool in summer and while it is full of ingenious tips, I have a better one: buy a portable air conditioner. Trust me, it's better than pulling the blinds or wearing socks you've kept in the freezer to bed. 

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Buying portable air conditioning: what you need to know

Particularly if you live in a flat – especially in a reasonably modern building – air con is more of an essential than a necessity. That's why buildings in many parts of the world come with air con built in. However, in the UK – and even many of the warmer parts of Europe – they do not. We put air con in our offices but not our homes. Retro-fitting a proper air con system can be extremely expensive and complicated.

The answer to this is a portable air conditioner (or two), but there are a few things you need to know.

Perhaps the most important things to know are the drawbacks of these machines. Portable air con units cost at least £300 if you want anything effective. They are generally ugly, they can be noisy, they're usually made of white or off-white plastic, quite large – around 80H x 40 x 40cm is fairly standard – and you won't use them for 9-10 months of the year. Depending on what your home is like and where, you might only use it for a few days of some years. 

But let me tell you, on those days you do need it, you will feel incredibly smug and pleased with your purchase. My one lives in the bedroom and cools it on even the hottest days. In theory I could – and probably should – move it to the spare room so it doesn't spoil the aesthetics of my room, but I just leave it in situ even during winter. 

The thing you really need to know about an air conditioner is whether it will actually cool your space. My one lives in the bedroom, which is about 15m sq, because it really struggles to cool anywhere bigger. It's a seven-year-old machine and I don't think it was exactly state of the art when I got it. 

The good news here is that air con units all come with a BTU rating and the estimated maximum room size they can handle. That's just as well because calculating the exact BTU you need is ridiculously complicated. Meaco recently sent  us a very advanced guide, and it includes a formula that takes into consideration the size of room, where and how big the windows are, the number of people in the room, the number and energy rating of electrical devices and lights in the room… you get the picture. 

• If you want to get busy with your calculator: try the full Meaco air con BTU calculator guide

The simplified version of that is to measure your room and then look at the recommended maximum room size for whatever portable air conditioners are available BUT if you live in a modern flat that's insulated to stay warm in winter, if the room has any significant amount of glass – especially if it lacks black-out blinds and/or if it gets a lot of sunlight during the day, buy a machine with an even higher BTU rating. In particular, if you have a kitchen and lounge in one room, as has been popular in new builds and conversions for the last few decades, you will probably need a more powerful machine. So if the measurements of the room are 30m sq, get air con built for a 40m sq space.

You also need to be aware of are how noisy the air conditioner is. When working full out even the quietest are likely to be around 60dB, which is roughly equivalent to normal conversational level. So while that's not going to drown out the TV, it's not negligible either, and probably a louder noise than most people want to sleep with. While our friends at Quiet Mark helped us compile our guide to quiet fans, they don't certify any portable air conditioners as quiet. 

The key in that case, is to cool your bedroom in the evening so it's down to around 20ºC by bed time. So long as night time temperatures aren't off the scale, you should then be able to sleep. What I do is run the air con in the bedroom for much of the day when I'm working from home, so there is always one properly cool room I can escape to when my office gets too much.

Air conditioner placement

One thing that you really need to be aware of is that you can't just put air con in a room in the same way as a fan. That's air con doesn't just move hot air around like a fan does; it puts out cold air, while doing its best to remove the hot air via a duct.

No word of a lie: I once went to a product launch in a bijou shop that didn't normally hold so many people. So for the event they had brought in portable air conditioning units, but they had no ducting. So if you stood in front of the air con, you got a lovely chilly breeze. And if you stood behind it, you were blasted with hot, fetid air. The net effect on the room temperature was, of course, zero. 

So, to get a more useful effect, you need to be able to vent the hot air out of your house. That means setup will need to be by a window or external door. Best practice is to drill a hole in the wall or get a window adaptor kit but to be perfectly obvious I just open a window a little bit and shove the ducting out of it. That can't be the most efficient way of doing it but it works fine for me. You just need to check that the hot air you're venting out is not immediately coming back in.

One final thing: most portable air conditioners can also be used as dehumidifiers and heaters. In all cases, you're better off with a proper dehumidifier or heater, but those features can come in handy from time to time.

The portable air conditioners I use

As I mentioned, I've been using the same machine for seven years. And it's still going strong. Well, it's still going. All the buttons on it have worn out and I lost the remote, so starting it up is a bit of a lottery. It also makes weird gurgling noises and it's quite noisy even when it's not doing that. So I don't recommend it as such but it is still available – or at least it's still on various websites, although largely sold out: this Electrolux one. This is typical of home, portable air con, being quite boring looking and not amazingly designed, but it does the job.

AEG recently sent me a second portable air conditioner and it is a lot nicer. The Chillflex Pro Portable RAC A is good for rooms up to about 20m sq. Compared to my old one it's quiet, has touchpad buttons that feel like they'll last, a decent remote and a nice long, well designed length of ducting. And I do like a nice duct. As usual with AEG, the fit and finish is a bit more premium than the norm overall. I can't vouch for whether it'll still be going strong in seven year, however.

• You can buy the AEG Chillflex Pro Portable at Appliances Direct for £499

Using air conditioning is a bit of a guilty pleasure – they use a lot of electricity and are hard to recycle at the end of their life. So in fact, they contribute to global climate change – and global warming means that more and more of us will be buying them. Ho hum. However in hot weather like we're experiencing now, a portable air conditioner still feels more like a necessity than a luxury.