As soaring temperatures make keeping homes comfortable a challenge, many are turning to portable air conditioners. While these units can be noisy and costly, their ability to significantly lower room temperatures often justifies the investment. These devices function by expelling warm air from a room through an exhaust hose, typically vented out a window, and circulating cooled air back into the space. However, a science expert has highlighted a common design flaw that hinders their efficiency and proposed a straightforward modification to enhance their performance.
Understanding Portable Air Conditioner Design Flaws
Michael Le Page, a senior reporter at New Scientist, detailed these issues in a video explanation. He pointed out that many portable air conditioners, particularly single-hose models, suffer from inherent inefficiencies, especially during heatwaves.
The Single-Hose Problem
Le Page explained that single-hose units draw air from the room itself to cool the condenser coils before expelling the hot air outside. This creates a negative pressure within the room, causing warmer, more humid outside air to be drawn in through any gaps or cracks in windows and doors. This influx of warm, moist air forces the air conditioner to work harder, consuming more energy and reducing its overall cooling effectiveness.
“If your house gets really hot during heatwaves, you might be thinking of getting a portable air conditioner,” Le Page stated. “But there are two problems with this type of design. So, if this is sitting on the floor with a single hose blasting hot air out of the window, the air conditioner is pulling in hot and humid air that it has to keep cooling all the time, and that wastes a lot of energy.”
He likened this process to adding dirt to laundry detergent, emphasizing that the hotter and more humid the outside conditions, the less efficient the unit becomes. “It’s like mixing mud into laundry detergent. The hotter and more humid it gets outside, the more inefficient the machine becomes.”
Heat Radiation from the Exhaust Hose
A second significant inefficiency stems from the exhaust hose itself. This hose carries hot air from the unit to the outside, and it inevitably heats up during operation. If this hot hose is located inside the room, it radiates heat back into the living space, counteracting the cooling effect of the air conditioner.
“Second issue is this hose,” Le Page observed. “You’ll feel it gets really hot when the air conditioner is running. So, if that’s inside your house, some of that heat is going straight back into the air in your room.” He noted that this design flaw means these machines “literally suck” in terms of energy efficiency, and current UK and European energy labelling standards do not adequately reflect this.
The Dual-Hose Solution and DIY Hack
Le Page advocated for dual-hose portable air conditioners as a superior alternative. These units feature an additional hose dedicated to drawing in outside air to cool the condenser. This outside air is then expelled, along with the heat, meaning the unit doesn’t draw conditioned air from the room.
“The next best option is something called a dual-hose portable air conditioner,” he explained. “That’s got an extra hose that sucks in the outside air before it takes the heat and gets blasted outside again.” Some manufacturers offer conversion kits to upgrade single-hose models to dual-hose systems, with one manufacturer claiming a threefold increase in cooling power with their kit.
Implementing the DIY Efficiency Hack
For those without a conversion kit, Le Page demonstrated a practical DIY hack. He showed how he sealed off the intake area at the back of his single-hose unit with cardboard. This modification ensures that the air drawn into the unit for cooling the condenser comes from outside the room, rather than from the room itself.
“If there is no conversion kit available, you can do a DIY job as I’ve done here,” he said, illustrating the cardboard seal. “Because the hose is outside, it’s not warming up my room at all.” He also recommended covering any internal exhaust hose with a towel or blanket to minimize heat radiation.
According to Le Page, this simple hack significantly boosted his unit’s performance. “This hack has dramatically increased the performance of this machine,” he reported. “Before, when it got really hot during heatwaves, it was struggling to keep a single room cool. Now it’s effectively cooling the entire house. It’s a huge difference.”
Recommendations for Energy Efficiency and Future Standards
Le Page urged the UK Government to revise energy labelling regulations for portable air conditioners. He believes clearer labelling is needed to inform consumers about how these units operate and to encourage the adoption of more efficient dual-hose designs over single-hose models.
He also pointed to split-unit air conditioners—which feature separate indoor and outdoor components—as a more energy-efficient option. While these typically involve a higher initial cost, their lower energy consumption can lead to long-term savings.
“They do cost more, but they use less energy, and might save you money in the long run,” he concluded, highlighting the trade-off between upfront investment and ongoing operational costs for superior energy efficiency.
