Find the Correct Portable Air Conditioner for Your Room Size

When buying a portable air conditioner for your home, it’s important to take several factors into account, from aesthetics and noise level to features like auto-evaporation and continuous drainage. The most important consideration, however, is undoubtedly the unit’s BTU (British Thermal Unit) rating.

What’s the relationship between BTUs and room size?

Simply put, models with higher BTU ratings can generally cool bigger spaces. However, keep in mind that the actual number of BTUs required for your room will vary based on additional factors besides square footage, including:

  • Number of windows
  • Level of insulation
  • Presence of heat-producing appliances
  • Ceiling height
  • Number of people occupying the space

Why is the BTU rating so important?

Buying a portable air conditioner that’s ill-suited for your space can harm both the PAC and your energy bill. If the unit has a BTU rating that’s too high, the unit will cool the room very quickly but repeatedly cycle off and on to maintain the desired temperature, raising your energy bill. This will also prevent the unit from adequately removing humidity from the air, leading to an unpleasantly muggy room.

Alternatively, using a unit that has a BTU rating that’s too low for the space will force the unit to exert extra energy trying to cool down the room. Again, you’re left with a higher energy bill—this time, in a room that’s still too hot for comfort.

How can I figure out the correct PAC for my room size?

The above graphic provides estimates of appropriate BTU ratings according to room square footage:

250-350 sq. ft.   8,000 BTU (ASHRAE)
350-450 sq. ft.  10,000 BTU (ASHRAE)
400-550 sq. ft. 12,000 BTU (ASHRAE)
550-700 sq. ft. 14,000 BTU (ASHRAE)


These numbers are a valuable rule of thumb when shopping for PACs, but you should always remember to take into account the previously mentioned variables to make sure you purchase a portable air conditioner that is best suited to your space. That way, you can cool down, save on energy costs, and help extend the lifespan of your unit at the same time.

Any questions?

 My Home Climate is your source for home comfort products and air cooling solutions. If you have any feedback or questions you’d like us to address, please get in touch with us at, where you can suggest topics for our next Air Comfort Answers blog. We’d love to hear from you!

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