Portable AC BTU Guide
What Size Air Conditioner Does My Room Need?

WA1010E Image2Even though we're in a culture where "super-sizing" is all the rage, this is definitely not the approach you want to take when choosing a portable AC. Though it may appear that bigger is better, choosing an air conditioner that is too powerful for your room will actually waste energy.

On the other hand, choosing a unit that is too small for the area is also a waste because no matter how efficient and highly-rated the mobile AC is, it will be completely ineffective.

For this reason, it's critical to know what size AC your room needs before you buy.

What should I know before purchasing a portable AC?

AC-12000E Image10There are many factors to consider when purchasing a portable room air conditioner. Do you need it to be multi-functional (since many units now double as a heater, fan, and/or dehumidifier)? Do you want it to have multiple modes? Are there any special design elements you'd like, such as LED display, remote control access, or maybe even a timer?

As you can see, portable air conditioners feature many choices. But the one choice that consumers tend to ignore is the unit's listed BTU level. Since many consumers get intimidated by abbreviations they don't readily know, they make the mistake of ignoring important specifications that need to be taken into consideration before purchasing a mobile AC.

Let's solve that problem right now. BTU stands for British Thermal Unit, which is nothing more than a unit of energy. A BTU tells us what an ACs power and cooling capacity is. The higher the BTU, the stronger the AC.

Mobile air conditioners usually have between 5,000 to 16,000 BTUs, with some having as many as 30,000 BTUs!

What happens if I choose the wrong size AC?

When we talk about the "size" of a portable air conditioner, we don't mean its physical dimensions but rather the BTU capacity. So while you should make sure your unit will actually fit in the room you want to use it in, it's critical to make sure it has the right BTU capacity to effectively cool the room.

AC-14100E Image1The right size depends on the size of the room.

  • A unit that is too small will have to run continuously, and never manage to cool the whole room effectively. It will probably break down sooner because it has to work so hard trying to do its job, not to mention the inefficient use of energy.
  • A unit that is too big will cause the air conditioner to cycle on and off too quickly to properly condition the air. When running properly, air conditioners remove moisture from the air which is a large factor in creating comfortable indoor environments. But a too-large portable AC will leave the air cold and clammy feeling.

How do I figure out which portable AC I need?

Measuring square footage:
The first step to finding out what AC is right for you is to figure out the square footage of the room(s) you need to cool. You can calculate the square footage by multiplying the length of the room by the width of the room. As an example, let's pretend your room is 18 feet by 25 feet:

Length x Width = 18' x 25' = 450 square feet

Matching square footage with the recommended BTUs:
Once you know the square footage, refer to the chart below and find the recommended BTUs for your square footage.


Room Size Recommended BTUs
150 sq. ft. up to 5,400 BTUs
200 sq. ft. 6,000 BTUs
340 sq. ft. 8,000 BTUs
400 sq. ft. 9,000 BTUs
450 sq. ft.10,000 BTUs
550 sq. ft. 12,000 BTUs
750 sq. ft. 14,500 BTUs
850 sq. ft. 16,000 BTUs
1,000 sq. ft.18,000 BTUs
1,400 sq. ft.24,000 BTUs
1,520 sq. ft.28,500 BTUs
1,600 sq. ft.32,000 BTUs

If you don't have a chart on hand when making your purchase, you can always get an estimate for your recommended BTUs by multiplying the square footage by 35.

Ideally, having a chart on hand is best. Just print out this page and keep it as a handy reference when you shop for a portable air conditioner. CV-2P10SX Image11

Factors to consider:
Since this chart is designed for an average room under average conditions, you should be aware of special conditions or needs of your room.

  • Add 10% to the BTU requirement if your room is in a sunny area, on the second story or in an elevated setting.
  • Reduce the BTU by 10% for shaded areas/rooms.
  • Add 600 BTUs if your room will host more than 2 people.
  • Add 4,000 BTUs if you will be using the portable AC to cool your kitchen.

Once you have taken these simple steps to figure out your cooling needs, you're sure to make a much smarter investment in your comfort. If you still need help choosing your portable AC, call our cooling experts who will guide you through the process.

View our selection of portable ACs.

Portable Air Conditioner Buying Guide
Portable Air Conditioners and Energy Efficiency
The Green Guide to Portable AC