How do Portable AC Units Work? (and FAQs)

Learn how portable air conditioners work their magic in our latest guide. We also answer the most common questions about these often misunderstood devices.


A portable air conditioner is a great way of cooling one room or a single space in your home.

They’re particularly useful if your central air system needs a little extra help to keep up with your household’s demands.

Although many people have one of these units, not many people know how portable AC works.

So, if you’re asking the question “how do portable AC units work?” we’ll answer it for you here!

What Does A Portable Air Conditioner Need to Work?

While all models are different and therefore have different requirements, most are quite easy to set up.

The key point of any AC unit is to take away the hot air during the cooling process. That means that the unit must find a way of moving the warm air to a different location.

Usually, this requires venting through a window to the exterior of the property, although some models have an exhaust through a wall or drop ceiling.

portable ac and cooling fans

Once the exhaust has been set up, you simply plug the portable AC unit into a power outlet, switch it on and then it will begin cooling the space straight away.

The majority of portable AC units are able to be used on a standard 115V or 120V power circuit. That means that no special wiring or outlets are required.

If the unit uses more than 14,000 BTUs though, it may need to be run on its own unique circuit, so it’s important to look at the owner manual to ensure that your choice of model is suitable for use on your own specific outlet type.

As all air conditioners use a lot of energy when they are operational, you’ll need to keep any other devices with a high energy requirement on a different circuit. This will prevent the overloading of a single circuit in your home.

Recommended: We’ve also prepared this guide on how to install a portable air conditioner for you.

Using Portable AC Units In Several Rooms

Another commonly asked question is how well do portable AC units work when it comes to cooling multiple spaces in the home at once.

Again, all units are different but depending on which one you choose, it may be capable of cooling multiple rooms.

Similar to standard window air conditioners, a portable unit is capable of cooling its immediate surrounding area.

However, the cool air will be unable to travel down a long hall or a doorway which isn’t connected directly to the space in which it is located. You may be able to cool two spaces that have a large opening between them, however, that cooling may be uneven.

The good news is that if you are only cooling a small space, a large unit won’t be necessary. A small and compact model should do the job perfectly well, and you might even be able to use a completely different kind of air conditioning unit.

Recommended: Check out our recommended quiet portable air conditioning units on the market right now.

Dual Or Single Hose Units?

A portable air conditioning unit cools down your room by using a hose which is vented through to the exterior of the property. A portable unit will have either a single exhaust hose to allow hot air to escape or two hoses.

When a unit has a single hose, it will take air from the space in which it is placed then return the majority of that air once it has been cooled.

However, since some air (albeit a small amount) will always be removed from the space, some negative pressure will be the result.

Portable air conditioner with wall vent

If a unit comes with two hoses, one of them will bring in air from outside the home while the other exhausts it back to the exterior.

Dual hoses don’t create a negative pressure, unlike a single hose model, but this type of design does reduce the efficiency of the unit.

It isn’t a good idea to try to lengthen your air conditioner’s hose. It has been designed to be a specific length in order to allow the appliance to operate efficiently.

If you extend the hose, your unit may overheat and the manufacturer’s warranty may be voided.

How Do I Vent An AC Unit?

Most portable AC units can be vented to a sliding glass window with a window kit. This type of kit can also be used on traditional windows.

When it comes to sliding glass doors, it is more complex to vent an exhaust hose in this way. This is because a window kit is usually too short to fit the door’s entire height.

Recommended: Ever wondered how to clean AC coils yourself?

How Often Do You Have To Drain A Portable Air Conditioner?

One main task that any portable air conditioning unit must do is remove moisture from the air. That moisture needs to go somewhere and that will depend on the type of appliance you have.

Self-evaporative models are advanced designs that automatically evaporate moisture from the exhaust hose together with the warm air. With this type of unit, you’ll rarely need to empty the water tank and the amount of ongoing maintenance is minimal.

Models that have a condensate pump and gravity drain use a drain hose attached to the appliance to remove water. The hose allows the moisture to drain out into a floor drain or bucket.

There are also some models that require the water to be removed manually. Sometimes, this could be as frequently as every eight hours.

Frequently Asked Questions


Here, we’ll answer some of the most commonly asked questions that you may have about portable AC units and how they work.

1. How Can A Portable Unit Be Moved To Different Rooms?

Unlike window units which are very heavy to lift and move, a portable AC unit will usually be fitted with a handle or wheels or both.

This allows for easy movement into different spaces and rooms without needing to lift any heavy appliances.

2. What Size Of Unit do I Require?

Portable AC units measure the power consumption that they use in BTUs. A higher number of BTUs means more powerful cooling and the more space it’s capable of cooling.

These figures below are a basic guide to possible requirements for the size of your space:

7500 BTUs – 150 square feet
9000 BTUs – 200 square feet
10,000 BTUs – 300 square feet
12,000 BTUs – 400 square feet
13,000 BTUs – 450 square feet
14,000 BTUs – 500 square feet

Remember too that fewer BTUs will be needed if you’re living in a cooler area or if you’ll only be using your unit during the evening.

If you’re living somewhere very hot or are going to use the unit during the middle of the day, a higher number of BTUs may be needed.

3. Can I Use My Portable Unit With A Crank Window?

If you have a crank or casement window, you won’t be able to find any portable AC units that come with a suitable window kit to fit your window type.

While some customers make their own solution by using Plexiglas and covering their whole window before cutting a hole into it for the exhaust hose, this may not be something you want to do.

Instead, you may wish to consider investing in a floor or free-standing air conditioning unit to cool your space effectively without needing to fit it in your window.

4. Will I Need To Take The Screen Off My Window When I Use A Window Kit?

If you have a screen on your window but want to use a window kit to connect your air conditioner to the window, you’ll probably need to know if it has to be removed to use the window kit.

The good news is that most people are able to leave their screen in place in their window since the portable AC unit’s exhaust hose rarely extends out of the window.

You should, however, check-in your unit’s product description before you buy to ensure that yours will not need the screen to be removed.

5. Running A Portable AC Unit In Your Home

As you no doubt already know, a portable AC unit can be a godsend in your home in the hot summer months, but it’s still important to understand the way in which they function.

That is why we have addressed the all-too-common question “how does a portable AC work?” in this article.

Now that you know how portable AC works, you’ll be better informed about what you’ll need and how your unit will need to be set up in your home to ensure that it functions correctly and efficiently.

We’ve asked all of the most commonly asked questions about portable AC units here, and explained how the system operates.

Therefore, you shouldn’t have any difficulties when it comes to running your air conditioning and ensuring optimal cooling in your home even on the hottest days of the year.

Recommended Next: Choosing the right air conditioner for your home can be difficult, but with this Shinco portable AC review, you’ll learn all you need to know.

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