10 Reasons Why You Should Avoid Portable Air Conditioners

Thinking of buying a portable air conditioner, but you don’t know if it’s a good idea? If so, you’re in the right place.

Soon you will discover the many untold information probably only known to the tradies or industry insiders. Something even the sales guy will never know (or choose not to know). You won’t regret learning these secrets! That’s for sure. Only then make an informed wise decision…

The truth is more evidence is weighing in on the gloomy side of portable air conditioners. A quick check on the test results found they were not as good as marketed. The once fast-selling and trendy portable ACs are now laden with piercing questions. This must be unreal you think?

Yes, they make cool air out of hot air. But credit to the Refrigeration Cycle inventor for making the theory works. In an era that worships energy efficiency more than ever, we doubt if these ACs are still worth talking about in the near future.

Specifically, we’re pointing at the single-hose portable air conditioners.

Here’re the 10 reasons why you should put single-hose portable air conditioners on your ban list. Okay, at least until you have exhausted all other cooling options.

#1. Creates Negative Pressure in Room

“What Comes Out, Must Go In”

It tells a lot just by looking at the single-house exhaust outlet. From the law, we know for a room to remain neutral in pressure, the air leaving must be equal to the air entering without restriction. But where’s the air intake? None.

Generally, these ACs use the cool air (it produced) in the room to cool the hot condenser part. And then get vented out through the hose via a fan. Here’s what happens next…

To replenish the lost air, the system will need some make-up air. But without a dedicated inlet, where could it possibly come from? The answer is everywhere – envelope leakages, soil vent pipe, basement, toilet, and etc. This creates negative pressure! And this is the last thing you want if you want to maintain good indoor air quality.

Some argue it as a form of ventilation air. Not true. If air leaks in naturally we call it natural ventilation. To some extent, it’s okay as long as you’re not over-ventilating your space. But if the air leak is caused by a fan we call it forced infiltration. Which is really bad.

As it invites a host of problems such as:

  • Increasing the cooling load
  • Bringing in pollutants and moisture
  • Causing condensation and off-gassing issues
  • Leading to structural failure and mold growth

#2. A Great Way to Waste Energy

The single-hose portable AC is taxing your energy bill every time you turn it on. But not in terms of how much cooling is generated but how much is being wasted.

For many years the portable ACs have not been regulated as much as the window unit due to the absence of proper energy standards. In 2016 the DOE published a notice to correct the test procedures for portable air conditioners. Effective only in 2019.

The change doesn’t solve the fundamental flaw of single-hose ACs. It only recalculates the cooling capacity based on the new testing procedures.

The main problem stays. They suck in what is precious. Use it to cool down the hot parts and throw it out. They are tasked to cool down the room but falsely pull in hot and humid air instead. The more it cools, the hotter it becomes.

Suddenly the AC has to work harder to remove the heat and moist. No wonder all single-hose ACs will need higher cooling capacity to achieve the same amount of cooling.

#3. No Quiet Portable Air Conditioners

Air conditioners are very mechanical. They are cranky. If you dissect inside all you see is pressure, heat, torsion, friction, vibration, compression, rotating fan, and oil. Messy stuff.

Then you bring them into your room and complain about the noise it makes. Does it make any sense? The noisiest part of any air conditioner is the compressor. While other cooling devices make sure they stay outside or up the roof, portable ACs did the opposite.

air conditioner outdoor units

You’re lucky if your portable AC is less than 60 dB when the compressor kicks in. Some smart guys have tried to destroy noise by stuffing more sound-absorbing materials and sealing off everything. But failed miserably. Don’t say they have not tried.

Sound is a form of energy. Can energy be destroyed? According to the Law of Conservation of Energy, NO. The good news is that noise is nothing but unwanted sound.

You have two choices. The first is to remove the source from your room. The second is to replace “unwanted” with “wanted” to turn noise into a melody. Stop complaining.

#4. No Portable Air Conditioners without Hose

There are no portable air conditioners without hose. They all need a hose to vent out heat. A room is cool and remains cool if there is no extra heat being added. If heat is continuously being added, it must be continuously removed to remain cool.

We have nothing against the vent hose if it doesn’t give us problems. A few issues are listed below:

  • Stop the AC from moving around
  • Need a venting kit to be installed with the window open
  • Has static and wind pressure to overcome thus consuming more fan energy
  • Can’t be extended in fear of causing overheating to fan or compressor
  • Off-gassing VOCs from plastic degrade when exposes to heat
  • Re-transfer heat back to space

#5. Unlock Window for Venting Kit: Secure or Not?

A portable air conditioner helps cool you down and lets you sleep well. But it can also open up your house to unwanted guests if you don’t secure the window with the vent installed. Who knows what will crawl in?

burglar try break in

But how to lock when your window is open and venting kit installed?

Yes, it is still possible with a special kind of security lock. It allows you to tighten and lock your window despite the venting kit. But the thing is no one can give you the guarantee. Your guest might have the last laugh!

#6. Plastic Hose Offgassing Toxic Fume

Plastic not only softens but also thermally degrades when exposes to heat. And because most plastics contain volatile organic compounds (VOC), it makes off-gassing extremely harmful. These are toxic carbon-containing chemicals that are highly unstable even at room temperature.

Air coming out of AC condenser is hot and high flow. It will quickly breakdown chemical bonds and accelerate off-gassing of volatiles in the plastic.

Worse almost all plastic hoses are not insulated. As heat is ejected it re-emitted back to the room. Now not only you have more VOCs in your air but an extra cooling tax to pay.

There’s a solution to this. Replace it with an insulated industrial type flexible duct.

#7. Portable But Not Very Portable

A major selling point of portable air conditioners is that they can roll around without the need for installation. All you need to do is plug-in and enjoy the chill. But unfortunately, that’s far from the truth.

Portable air conditioners are fairly heavy and not small in size. And because they need to expel heat to the outside through a hose, there is a limitation in where it can actually operate – within a few feet of a window or wall opening.

After the hose and venting kit are installed, it basically sits and stuck there forever. You may ask why portable dehumidifiers can move freely but not portable ACs. It’s because they have no hose to be taken care of. All waste heat is reclaimed to raise the supply air temperature to achieve low relative humidity.

As if heavyweight and fussy window kit setup are not enough. The floor surfaces of your room will have the final say if your portable AC is really portable.

#8. Drain Out Condensate Is A Pain

When the evaporator temp drops below the air dew point, water starts to condense out of air. And the amount depends on the air humidity at that time.

You’ll see a dry bucket when humidity is low. And a filled bucket when humidity is high. Because it varies people tend to forget when to drain out the water. Sitting water can lead to huge problems. The most common ones are mold growth and Legionella disease.

But most portable ACs have an outlet for continuous draining with or without a pump. Connect to a tube and it will flow automatically. Wait a minute! Where should the tube go?

To a floor trap or a sump. If they’re too far or too high you have a problem. Running a long tube across the room is not only ugly but disturbing. It bends and clogs up easily too.

#9. Poor Air Flow Pattern

The movement of supply and return air creates an airflow pattern. It determines air mixing efficiency and the room air temperature you enjoy. Simply, room air temp is actually mixed temp of supply air and room air.

Portable air conditioners are not designed to have long air throw. Two reasons. The first is related to the noise. AGAIN. Big fans are loud and the air jet it must produce to create long throw can regenerate noise.

The second is the supply and return air location. For cooling, they’re just too close to each other. As cold air sinks, a weak throw will certainly cause short cycling. It occurs when cold air takes a short turn and back to the intake without mixing with room air.

Now you have an idea why portable ACs can generally cool only a localized space.

#10. Low Filter Grade

Portable air conditioners shouldn’t be called air conditioners because they’re not. They’re made to do one thing – to cool and perhaps dehumidify. But if an air conditioner is to carry that name tag it should do more than just cooling…

Since fans are already being used to circulate air, why not use a better grade filter like HEPA to improve indoor air quality? It turns out noise is the bitter pill. AGAIN…

Fine filters are not easy to operate without strong fans. And strong fans are generally louder than small fans. So the genius way in solving this issue is to use low-grade filter and fan. Everyone is happy except the allergies and asthma sufferers.

We also know cold temperature raises relative humidity and high relative humidity triggers mold growth. AC that is not properly maintained and cleaned can expose you to allergies and asthma.

But the question is where is the much needed last line of defense – carbon filter, HEPA, etc… Click to see how dirty an AC can get over time.

Yes, you can see one or two pieces of pre-filters there. But they’re there to protect the coils. Unfortunately, not you…


We’re happy you have come this far. While the single-hose portable air conditioners are laden with cons, they are not without any good. At least it cools. But you are better off with other cooling equipment.

Some claim portable air conditioners are similar to portable dehumidifiers. Yes and No. Yes because they use the same basic concept. No because these dehumidifiers have no heat to eject out.

And treating temperature is not the same as treating humidity. Hot air rises and cold air sinks. But humidity doesn’t quite react in the same way.

Same theory. Two different applications.

If you really need some cooling to wind your sweaty back, think of portable air conditioners as the last resort. Possibly a dual-hose portable air conditioner will do the trick for you.

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