Why Portable Air Conditioners Need to Be Vented?

Portable air conditioners are convenient to use until you find out that they need to be vented with a hose. If you don’t vent it, it’s not going to cool your room. But, why portable air conditioners need to be vented?

Portable air conditioners need to be vented because they provide cooling by extracting the heat within the room and discharging it in a form of hot air outside through a hose. An unvented portable air conditioner is not extracting heat out of the room and therefore, does not provide cooling.

Venting a portable air conditioner is essential to have cooled. Understanding the working principle behind portable air conditioners can explain why once and for all.

How Portable Air Conditioners Work?

Portable air conditioners work just like other types of air conditioners including central air conditioners, mini splits and window air conditioners. They use the refrigeration cycle process for cooling.

Front and Back of a Portable Air Conditioner

In order for a portable air conditioner to cool the room, heat within the room must be extracted and transferred to somewhere else, usually outside the house.

Portable air conditioners do not actually “give” cooling but rather they extract heat and therefore, the room becomes cooler.

Inside of a Portable Air Conditioner

If we go deeper, a portable air conditioner starts from step 1 which is the return air. Indoor heat (heat within the room) is being drawn into the cooling coil of the portable air conditioner. After that, the heat is absorbed by the cooling coil and thus, the supply air is cold.

Over to step 2, the heat is then transferred from the cooling coil to the condenser coil by the refrigerant which is an essential element of the refrigeration cycle.

Once the heat reaches the condenser coil, a fan draws the air within the room and forces it through the condenser coil where the air becomes hot and then, continues to push the hot air out of the room and the cycle repeats.

After a few rounds of heat extraction, the room gradually cools down.

Since the indoor air is being drawn and pushed out of the room, portable air conditioners are known to cause negative room pressure. Once that happens, hot air from the outside will naturally flow back to the room.

That’s why there is a DOE/SACC-rated cooling capacity for portable air conditioners. It represents the actual cooling power of portable air conditioners after considering the hot air infiltration.

What Happen If Portable Air Conditioners are Not Vented?

By now you should have guessed what happens if a portable air conditioner is not vented. The answer is there will be no cooling effect at all.

Air conditioners fundamentally work by transferring heat from indoors to outdoor to achieve cooling. If a portable air conditioner is not discharging hot air to the outside, it essentially acts as a space heater, providing net heating to the room instead of cooling.

How Portable Air Conditioners Work Without a Window?

If your room doesn’t have a window, you need to find alternative ways to vent your portable air conditioner. There is no other way around it. You can either throw the hot air to the next room, the storage room, the kitchen or whichever room you think does not need cooling at that moment.

However, if the room is enclosed, it’ll eventually get too hot and your portable air conditioner will stop working.

Well, how about using a ventless portable air conditioner if your room doesn’t have a window? The answer is ventless portable air conditioners don’t work the same as vented portable air conditioners. In fact, ventless portable air conditioners shouldn’t be called air conditioners. Instead, they are more accurately known as evaporative coolers or swamp coolers or air coolers.

See the following posts to understand more about “ventless portable air conditioners”:

There are all sorts of creative ways to vent a portable air conditioner if your room doesn’t have a window which you can find on Google. However, I don’t think anybody had suggested venting a portable air conditioner into the toilet and utilizing the toilet exhaust system to carry away the hot air.

Such a method can work but the toilet exhaust CFM must match with the CFM of the portable air conditioner. Usually, the toilet exhaust fan generates about 150 CFM. At low fan speed, many portable air conditioners also blow at around 150 CFM. Something to work on.


Portable air conditioners need to be vented so that hot air can be extracted and discharged out of the room to achieve cooling. Not venting a portable air conditioner will lead to no cooling but heating instead. So, it is a good idea to always vent your portable air conditioner.

This article was originally published on aircondlounge.com. Actions will be taken for unauthorised republication of this article.

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Yu Chang Zhen

Yu worked as a professional in the HVAC industry for more than 7 years. He is an engineer who has a passion for blogging. Ever since he created this website, Yu has helped hundreds of homeowners and engineers on HVAC related matters.

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