Keeping cool, one room at a time, with a portable air conditioner

What Size Portable Air Conditioner Does My Room Need?

by Shireen Shah

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Even though we're in a culture of "super-sizing," this is definitely not the approach you want to take when choosing a portable air conditioner. 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 portable A/C is, it will be completely ineffective. For this reason, knowing what size portable air conditioner your room needs is absolutely critical.

What you should know before purchasing a portable air conditioner?

There are many factors to consider when purchasing a portable room air conditioner? Do you need it to be multi-functional (since many units now pair 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 portable A/C.

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

Portable air conditioners usually have a BTU of about 5,000 to as 30,000 BTUs! And just as you try to keep other appliances in your home in proportion to your needs, so should you do the same with your cooling unit. Now that you know a mobile A/C with a 30,000 BTU is a highly powerful unit, you know such a unit is better suited for a much larger room, say a large living room, rather than a very small bedroom.

What happens if I choose the wrong size portable air conditioner?

Choosing the wrong size is not even so much about physical size, but about the BTU capacity of a portable A/C unit. Now that you're a whiz on BTUs, lets take a look at what happens when the wrong A/C is chosen.

The A/C size you'll need depends on the size of the room you intend to cool. Choosing the wrong unit not only makes your air conditioner inefficient in cooling, it will also be inefficient in running. For example, if an air conditioner has a higher BTU rating than the room you intend for it to cool, the unit will cycle off too quickly and be unable to properly remove the humidity from the air.

On the other hand, if the portable air conditioner has a lower BTU rating than the required room size, the unit will not adequately cool the room.

How do I figure out which portable air conditioner I need?

Measure square footage. The first step to finding out what A/C is right for you is by figuring out the square footage of the room(s) you need the most cooling for. Once you have that in mind, measure the square footage of that room. 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

Match square footage with the recommended BTUs. Refer to the chart below and find the recommended BTUs for your square footage. To continue with our example, let's pretend that your room is 450 square feet.

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 think you'll 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.

Since this chart is designed for an average room under average conditions, it's advisable to consider if there are any special conditions or needs your room has.

  • Add 10% BTU if your room is 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 two people.
  • Add 4,000 BTUs if you will be using the portable A/C 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 invest in your comfort.

Courtesy of, a premier online retailer of residential and commercial cooling products, as well as other home appliances such as electric fans, ice makers, humidifiers, dehumidifiers, and heaters. Visit their online library here, which covers product buying guides, expert articles, health articles, money saving articles, as well as green articles.

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