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

single-hose portable – Many portable air conditioners are built to pull in hot outside air while they cool, making them far less efficient during heatwaves. The fix is surprisingly simple: add a second hose and an attachment to convert single-hose units to dual-hose performance. In

The May heatwave in the UK didn’t just make the house feel uncomfortable. It made the limits of a portable air conditioner feel personal.

I tried a crude conversion—adding another hose—and the whole house felt much cooler. It was the first time I truly understood what I’d bought.

Portable air conditioners have become a lifeline as sweltering heatwaves become more common. Yet many. if not most. portable units share a design flaw that can quietly drain their efficiency: single-hose models don’t just cool the room. They continuously suck in hot outside air and then vent heated air back out—so the machine is constantly working against the same heat that’s already pressing down on your home.

To understand why that matters, you have to start with how the better systems are built. The most efficient air conditioners use split systems. Refrigerant is compressed in an outdoor unit. where it heats up. and is then cooled by a heat exchanger over which outside air is blown. The refrigerant runs through a narrow pipe to an indoor unit, where it’s turned into a gas, cooling it. Room air is blown over another heat exchanger, transferring heat from the room to the refrigerant. In split systems, room air stays in the room; only heat is taken out. They’re also typically quieter because the compressor is outside.

Portable units don’t usually get to use that arrangement. For upstairs rooms in particular, there’s often nowhere practical to place the outdoor unit. So some portable air conditioners instead pull air from outdoors into the room and then blow heated air out through a second hose—dual-hose units. Dual-hose models are less efficient than split systems, and the outlet hose can transfer some heat back into the room. If the hose ends are too close, heated air can also be sucked into the intake. But even then, room air stays inside.

Single-hose portable air conditioners take a different approach. With them. room air is used to cool the hot refrigerant and then blown out through the single hose—meaning hot outside air is continuously sucked into the room. If a window is open, hot air comes in that way. With windows closed, it can come through other parts of the home, warming them as it travels. In either case. the air conditioner keeps having to cool hot outside air. which is why it uses much more energy. The comparison offered is blunt: it’s like adding mud to laundry detergent.

The penalty doesn’t stop there. The efficiency of single-hose air conditioners falls rapidly as it gets hotter outside. They fail to keep a room cool much sooner than a similarly powered dual-hose unit.

The most frustrating part is that this flaw often isn’t obvious at the point of purchase. In Europe. none of the labels is designed to tell buyers how much additional heat the unit has to handle when hot outside air is being pulled into the room. Cooling capacity is stated in British thermal units—BTUs—but the figure is a measure of heat transfer within the machine. It doesn’t capture the extra work created by continuously sucking in hot air. The same problem shows up in seasonal energy efficiency ratio. or SEER. numbers: they’re calculated as cooling capacity divided by the electricity consumed. By these measures, dual-hose air conditioners can appear no better than single-hose models 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. The reality of that space problem helps explain why single-hose units are common—and why dual-hose models can be very hard to find in the UK.

The US. by contrast. has introduced labelling measures intended to account for hot air sucked into a room and heat coming off the air outlet hose. One is seasonally adjusted cooling capacity. or SACC. which is typically much lower than an unadjusted capacity number—by a third or more. Another is the combined energy efficiency ratio, or CEER, where dual-hose performance starts to show more clearly.

Even with those improvements, the measurements still may not reflect the conditions people actually face. Both SACC and CEER assume the outdoor temperature is 28°C (82.4°F) for 80 per cent of the time the air conditioner is running. and 35°C (95°F) for 20 per cent. The argument here is practical: what matters most is how an air conditioner performs when the thermometer hits 40°C (104°F). not when it’s lower.

Then comes the part that feels almost insulting in its simplicity. In many cases, most single-hose portable air conditioners are essentially dual-hose units shipped with only one hose. The fix can be another hose and an attachment. At least one manufacturer. GE. sells a conversion kit for some of its single-hose models. advertising it as increasing cooling power by three times.

DIY conversions are also widespread, ranging from tape-and-cardboard setups to 3D-printed parts. In accounts read by the author, conversions make a big difference—matching what happened when a crude conversion was tried during the May heatwave, when the whole house became noticeably cooler.

The story isn’t just about personal comfort. It’s about what happens when ratings tell shoppers one thing and summer delivers another. In the author’s view. the labelling of portable air conditioners needs to be changed in the UK and the European Union so it reflects real-world performance during the hottest heatwaves. It’s also described as bizarre and misleading that single-hose air conditioners can carry “A” ratings for efficiency.

And if updating labels doesn’t go far enough. the proposal is more direct: a complete ban on the sale of single-hose air conditioners. The ideal would be that all portable units are sold as dual-hose. with the option to use them as single-hose only when people cannot set up dual hoses. Put another way, no single-hose air conditioner should be sold without a conversion kit. Michael at Meaco is said to be considering introducing such a machine in 2027.

Trying to identify who regulates this in the UK led to a dead end. The Department for Energy Security and Net Zero did not respond to a request for comment. The Energy Saving Trust also did not get back. Still. the takeaway is clear: there’s an easy climate win available if the rules finally catch up with how these machines actually behave.

One sentence can capture the tension driving this whole argument: the technology exists to stop portable units from sucking hot air into the room—but the market often isn’t forced to disclose it.

portable air conditioner single-hose dual-hose heatwaves energy efficiency SEER SACC CEER climate change refrigeration