A portable air conditioning unit can be a lifesaver if you live or work in an area that doesn’t have access to a larger, centralized cooling unit. It has the added benefit of being able to be brought along when you move into another building, meaning that you can have peace of mind knowing that as long as you have access to a source of electricity, you’ll have air conditioning.

The fact is, however, that not all AC units work equally well for a given area. The question you’ll need to ask before you purchase one is, “What size portable air conditioner do I need?” To help you answer that question, we’ll offer some information about portable air conditioners so that we can hopefully help you size your AC unit correctly.

Air Conditioning: How It Works

Air conditioning units come in all shapes and sizes, but the basic principles behind their operation are always more or less the same. Air conditioning is powered by electricity and must be connected to a building’s primary power source to operate effectively.

First, the user enters their preferred temperature on a thermostat, which then automatically switches the unit on or off as necessary. Inside the unit, there are coils containing a pressurized coolant, the expansion of which causes the coolant’s temperature to drop significantly. This causes the coils themselves to become very cold. In turn, any air that passes across the coils is then “conditioned” or cooled.

The AC unit must then circulate the air throughout the area it is designed to cool. Different AC devices do this differently, often with a built-in fan, but in every case, the air must have a clear path by which it can make its way through the space that’s being cooled.

How to Make It Portable

While all air conditioners operate using the principles we’ve mentioned above, they differ in other key ways, particularly in the size of each air conditioning unit. Larger buildings, such as skyscrapers, may have incredibly large HVAC systems to provide their cooling. If you’re looking to cool an apartment, single office, or small house, you can often do so with a portable AC unit.

Rather than being installed in an out-of-the-way location somewhere on the property, a portable air conditioning unit is small enough to be used inside of the room it’s cooling. Often, the unit is on wheels so that it can easily be rolled from one room to the next, as necessary.


Because, unlike other types of AC units, a portable air conditioner has its main machinery indoors, there must be a way for waste heat to be allowed to escape to the outside of the building safely. This is accomplished through the use of a flexible hose that is connected to an open window. A seal is created so that the conditioned air does not leak back out.

The unit also requires a power source. For a portable air conditioner, it’s usually enough to simply plug it into an available outlet. However, the energy requirement is still quite high, so to avoid a surge, it is recommended that you avoid plugging multiple appliances in the outlet that is used for your portable AC unit.

How to Choose the Right-Sized Machine for Your Space

Just as there are many different types of air conditioners, there are also many different types of portable air conditioners, each rated to be most effective in a different-sized area.

It’s important that you ask the question, “What size portable air conditioner do I need?” because if you choose the wrong size, it will end up being less efficient. If it’s too large for the given area, it will draw more energy than it needs to, causing your energy bill to go up. If it’s too small, it will have to work much harder than it would otherwise to achieve your desired temperature. As a result, your energy bill will, once again, go up.

Whether it’s for heating or cooling, the heat energy that a piece of HVAC technology can transfer is measured in British Thermal Units, or BTUs, for short. One BTU is the amount of energy required to increase the temperature of one pound of water by one degree Fahrenheit. Generally, it takes about 20 BTUs per square foot for a room, so multiply the square footage of your space by 20 to get the BTU rating your portable AC unit needs.


For example, a 300-square-foot room will probably need an air conditioner rated for around 6,000 BTUs. Remember that it should be as close to this rating as possible. Any more, and you’ll end up using energy that’s not needed. Any less and your machine will be forced to use extra power to perform its job.

Benefits of Portable Air Conditioning

There are several advantages to choosing a portable air conditioner over some other cooling methods. The fact that it’s portable is, predictably, one of the most important. As we’ve mentioned, this makes it easier to transport. It also allows you to provide air conditioning to a space that would not otherwise have it. Many buildings are either too old or too small to have the elaborate system of ductwork a larger air conditioning system requires.

Portable air conditioners can also be a good deal more energy efficient than other cooling methods because they can focus on a single space in a building. For example, if you spend most of the day in one room, you wouldn’t want to waste energy cooling the entire building. Instead, you could purchase a portable AC unit that is rated for a room of that size so that you can keep that room comfortable without paying more for cooling than you need to.

If you decide that a portable air conditioner is appropriate for your needs, your next step will be to contact an HVAC professional from a reputable company like Entek HVAC. They will then be able to further advise you on the best portable air conditioner for your particular needs.