Some of you are in for warm weather next week, and some of you have portable A/C

[SteamyTea]

Most portable air conditioners suck – but there's an easy fix

Efficiency ratings on portable air conditioners don’t give consumers the full picture, and one type of aircon unit is so inefficient that it should be banned, says Michael Le Page

By Michael Le Page

19 June 2026

Single-hose air conditioners suck hot air in from outside

Ton Hazewinkel/Getty Images

 

Thinking of getting a portable air conditioner as sweltering heatwaves become more common? You will want to know that many, if not most, portable air conditioners have a serious design flaw – and that there is no label required to inform buyers of this.

I had no idea about it when I bought a portable air conditioner. What’s most shocking is that there is an easy fix – and I think the law needs to be changed so that no portable air conditioners can be sold without it.

 

First, let’s deal with the idea, especially common in the UK, that it is somehow wrong to buy an air conditioner. If you don’t need it where you are, great. But lots of us live in homes that get too hot during heatwaves, even when you do all the right things, like shutting blinds and windows during the day. And being too hot is bad for our health – sometimes, it is even deadly. It also makes it hard to work or do schoolwork. If it is OK to use energy to heat homes, I think it is also OK to use energy to stay cool – what’s the difference?

The fact is that, as the world heats up, more and more of us will resort to air conditioning to stay cool. Reducing the energy used by all these extra air conditioners is really important to minimise extra carbon emissions that result in even more warming – and even more need for air conditioners.

To understand the design flaw, you need to know how air conditioners work. The most efficient ones have a split system. There’s an outside unit, where a refrigerant is compressed to make it liquid, heating it up. It is then cooled by a heat exchanger over which outside air is blown.

 

The refrigerant then goes through a narrow pipe to the inside unit, where it is turned into a gas, cooling it down. That goes through another heat exchanger over which the room air is blown, cooling that air by transferring its heat to the refrigerant.

So the room air stays in the room, and only the heat is taken out. There is also less noise with split systems, because the compressor is outside. But they are almost all expensive, built-in systems – very few portable split systems are available, in part because, for upstairs rooms, there is usually nowhere to put the outside unit.

Instead of an outside unit, some portable air conditioners bring air from outside into the room. There is a wide air intake hose that sucks in outside air, and the heated air is blown out of a similar hose.

Dual-hose air conditioners, as they are known, are less efficient than split systems. The outlet hose transfers some heat to the room – you can reduce this by wrapping a blanket around it – and if the hose ends are too close, heated air can get sucked into the intake. But as with split systems, room air stays in the room.

With single-hose portable air conditioners, however, there’s no air intake hose. Instead, room air is used to cool the hot refrigerant and then blown out of the single hose, which means hot outside air is continuously sucked into the room.

If there’s a window open, hot air will come in through that. With the windows closed, the hot air will come via other parts of your home, warming them along the way. Either way, the air conditioner is constantly having to cool hot outside air, and so it has to use much more energy. It’s like adding mud to laundry detergent.

What’s more, the efficiency of single-hose air conditioners falls rapidly as it gets hotter outside. They will fail to keep a room cool much sooner than a similarly powered dual-hose one.

 

This is a huge design flaw, but in Europe, none of the labels tells you this. The specifications for an air conditioner state its cooling capacity in British thermal units, but this is simply a measure of heat transfer within a machine. It doesn’t take into account the fact that more heat has to be transferred if hot air is continuously sucked into a room.

The same is true of the seasonal energy efficiency ratio, or SEER, numbers you might find. These are just the cooling capacity divided by the electricity consumed. By these measures, dual-hose air conditioners appear no better than single-hose ones that are easier to set up.

“Consumers find dealing with the two ducts difficult and often don’t have the space to vent two ducts out of the room,” says Chris Michael at the cooling company Meaco. So it isn’t surprising that people choose single-hose units and that dual-hose ones are very hard to find in the UK.

The US is doing better on the labelling front. It has introduced two measures that take into account hot air sucked into a room and heat coming off the air outlet hose. There’s the seasonally adjusted cooling capacity, or SACC, which is much lower than the unadjusted capacity number, typically by a third or more.

Even more important is the combined energy efficiency ratio, or CEER. It’s here that you start to see how much more efficient dual-hose air conditioners are.

But in my view, these numbers still don’t give buyers the full picture. Both the SACC and CEER measurements assume the outdoor temperature is 28°C (82.4°F) for 80 per cent of the time an air conditioner is running, and 35°C (95°F) for 20 per cent. I don’t need air conditioning at 28°C – it’s how an air conditioner performs when the thermometer hits 40°C (104°F) that’s most important to me.

 

Now here’s the most ridiculous thing. Most single-hose air conditioners are essentially dual-hose units that come with only one hose. All you need to fix this flaw is another hose and an attachment. At least one manufacturer, GE, sells a conversion kit for some of its single-hose models – and advertises it as increasing cooling power by three times. Three times!

Lots of people make DIY conversions, ranging from tape-and-cardboard affairs to 3D-printed parts, and every account I have read says it makes a big difference. That was my experience when I tried a crude conversion during the May heatwave in the UK, with the whole house feeling much cooler.

So, in my view, at the very least, the labelling of portable air conditioners needs to be changed in the UK and the European Union to reflect their real-world performance during the hottest heatwaves. It is bizarre and misleading that single-hose air conditioners can have “A” ratings for efficiency.

Better still would be a complete ban on the sale of single-hose air conditioners. All portable units should be sold as dual-hose, with the option to use them as single-hose when people really cannot have a dual-hose setup. Put another way, no single-hose air conditioner should be sold without a conversion kit. Michael says Meaco is considering introducing such a machine in 2027.

I tried to find out who in the UK is responsible for regulating portable air conditioners, and hit a blank. The Department for Energy Security and Net Zero did not respond to a request for comment. Nor did the Energy Saving Trust get back to me. But hopefully the right person might end up reading this. There’s an easy climate win to be achieved here.

[ProDave]

I have a portable AC unit bought many years ago when I lived down south and it got too hot a lot more often.

 

I hate it.  Not because it is inefficient, it does work, and it does cool the room.  BUT it is so damned noisy.  I don't want a noisy poorly designed rattly compressor running in the bedroom when I am trying to sleep.  We had the same issue on our last 2 visits to the USA.  Hotel rooms with an AC unit in each room.  You have the choice of not sleeping because you are too hot, or not sleeping because the AC unit is on and it is so damned noisy.

 

Why would anyone WANT an AC unit that puts the noisy compressor in the room that they are trying to cool?

[Adrian Walker]

A better way to cool your home if you have UFH is to cool the slab by a couple of degrees. 

[Nickfromwales]

8 hours ago, ProDave said:

I have a portable AC unit bought many years ago when I lived down south and it got too hot a lot more often.

 

I hate it.  Not because it is inefficient, it does work, and it does cool the room.  BUT it is so damned noisy.  I don't want a noisy poorly designed rattly compressor running in the bedroom when I am trying to sleep.  We had the same issue on our last 2 visits to the USA.  Hotel rooms with an AC unit in each room.  You have the choice of not sleeping because you are too hot, or not sleeping because the AC unit is on and it is so damned noisy.

 

Why would anyone WANT an AC unit that puts the noisy compressor in the room that they are trying to cool?

I think, psychologically, that you accept audibility / nuisance of anything that is cooling you down, as I’d rather have the noise than the heat every damn day.

 

I put a 12000BTU unit in my lads attic room and it’s defo not ‘quiet’, but he sleeps through it without losing a wink. If too hot, none of us sleep well, so without a budget for fixed, wonderfully quiet, fixed AC present, this is a very acceptable compromise for the masses. 

[saveasteading]

Any thoughts on the Mediterranean method? It seems simple and very diy-able with the inner and outer units, and only the small pipes and a cable to drill through a wall.

The outputs aren't huge so it's one per room probably.... that is what seems to be the norm domestically and in hotels.

I wonder if the different climate types make any difference to spec because they seem to be available here but at twice the price.

Not that I'd buy an unknown brand like this.

 

 

[JohnMo]

44 minutes ago, saveasteading said:

Any thoughts on the Mediterranean method? It seems simple and very diy-able with the inner and outer units, and only the small pipes and a cable to drill through a wall.

The outputs aren't huge so it's one per room probably.... that is what seems to be the norm domestically and in hotels.

I wonder if the different climate types make any difference to spec because they seem to be available here but at twice the price.

Not that I'd buy an unknown brand like this.

 

 

One thing stands out and it the price, if compare to an ASHP it has nearly all the same components, it will have an air to refrigerant condenser/evaporator, fan, compressor, a casing, a controller, only the thing is the refrigerant to water heat exchanger and pump are missing. But its 10x cheaper - and everyone says an ASHP has to be expensive because it's complex, this sort of proves the point it doesn't. It may not have have a defrost cycle built in but if it does heating and cooling it will have all the hardware, which is a 4 way valve.

[saveasteading]

11 hours ago, JohnMo said:

 if it does heating and cooling

They are made for cooling.

The ones I've looked at do heating but not very efficiently: better than an electric heater still..  but maybe not much use if it's minus 10 outside.

[JohnMo]

37 minutes ago, saveasteading said:

They are made for cooling.

The ones I've looked at do heating but not very efficiently: better than an electric heater still..  but maybe not much use if it's minus 10 outside.

Why not spend a bit more and get one that does cooling and heating well. If the performance isn't quoted as good, maybe the indoor unit isn't that good either, noisy and drafty.

[saveasteading]

2 hours ago, JohnMo said:

the indoor unit 

The ones I have seen have a fan and louvre. This blows room air over the cold plate.  Presumably they have published noise figures but I think most people accept, even welcome, the confirmation that cooling is happening.

 

2 hours ago, JohnMo said:

Why not spend a bit more 

Because we spend as appropriate to budget and needs.

It's easy to spend more.

[SimonD]

3 hours ago, saveasteading said:

They are made for cooling.

The ones I've looked at do heating but not very efficiently: better than an electric heater still..  but maybe not much use if it's minus 10 outside.

Of course, heat pumps for heating versus heat pumps for cooling actually require fundamentally different designs, which is partly why one designed primarily for heating won't be as good at cooling as one designed primarily for cooling and vice versa. This is because they have very different operating conditions, different demands on the compressors and also different condenser and evaporator design requirements, not to mention variations in the vapour compression cycle conditions.

[Ferdinand]

I'm still running one of the portable ones with a claimed COP of 2.5 to 3.

I'm sure that I have some of the issues mentioned by @SteamyTea but I do not have my engineering head on today.

It is more than covered by the solar and will only be used a little to keep the house at around 23C, so I'm not worrying. But when my gas boiler goes pop, or I am so inclined, it will be a carefully designed A2A installation that replaces it.

Here's the thread from 2022:

 

 

[SteamyTea]

1 hour ago, Ferdinand said:

more than covered by the solar and will only be used a little to keep the house at around 23C

Not really the way to look at it.

If something is running inefficiently, more waste thermal energy is produced. This manifests itself in more wear, noise and less performance.

 

[NSS]

There's nothing inefficient about running cooling mode on our ashp in this weather. Goes on at 8am and off at 6pm, during which time it is entirely powered by our PV panels. If it starts to struggle to maintain our 22c indoor over the next few days, I'll also run it during the 7p/kW Intelligent Go period overnight.

[Oz07]

5 hours ago, SimonD said:

Of course, heat pumps for heating versus heat pumps for cooling actually require fundamentally different designs, which is partly why one designed primarily for heating won't be as good at cooling as one designed primarily for cooling and vice versa. This is because they have very different operating conditions, different demands on the compressors and also different condenser and evaporator design requirements, not to mention variations in the vapour compression cycle conditions.

Does this apply for A2A or do they switch between heat and cooling fine?

[JohnMo]

7 minutes ago, Oz07 said:

Does this apply for A2A or do they switch between heat and cooling fine?

Not sure it actually applies to ASHP either. Now had two and both performed the same on heat and cooling. My ASHP is currently chugging away cooling the floor at a CoP (EER) of 7.5, so doing well for a heat pump designed for heating.

 

A2A will switch between either as long as it is not a cheap as chips cooling only one and includes defrost functionality.