Which Is The Best AC For A Normal Room Size?

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Which Is The Best AC For A Normal Room Size?

For the sake of this blog, I’m going to refrain from any bad “does size really matter” jokes when it comes to the AC unit in your Steger, IL or Crown Point, IN home. Instead, just a simple and straight-forward article from Merts Heating & Air Conditioning about why the right choice is very important to keep your home cool and comfortable during an Illinois or Northwest Indiana summer.


While there are many variables to consider, an air conditioner needs 20 BTU per square foot to effectively cool the living space in your home. Portable or room AC units range from 5,000 to 12,500 BTU. Central air conditioners are from 12,000 to 60,000 BTUs.


Just like the little girl in the fairy tale, you should be looking for an AC unit that is just the right size. An HVAC system size that’s too small means your home may never cool properly. Buying one that’s too large can lead to short cycling. That’s what it’s called when an AC unit is turning on and off constantly. It’s a serious problem that increases cooling cost and shortens equipment lifespan.


Determining the proper size portable or window air conditioner to cool an individual room with is fairly easy. Simply determine the square footage and multiply by 20. Small bedrooms are often less than 300 square feet, while larger master bedrooms can be 400 square feet. Things get much more complicated when talking about central AC units to cool an entire house. There are many variables when it comes to determining HVAC system size including:

  • Square footage
  • Number of windows
  • Quality of windows and doors
  • Type of floor plan
  • One story vs multi-level home
  • Quality of insulation
  • Exposure to direct sunlight

Determining what we call in the business the cooling load requires a complicated formula. This should always be done by a trained Merts technician.


Once you know what size you need, then you can determine what model is best for you. Efficiency is important because it means lower monthly bills, but it will cost more money upfront. Merts Heating & Air Conditioning always likes to tell our customers to buy the most efficient AC unit their budget allows. Be sure to like and follow us on Facebook and Twitter for more great HVAC information for your Illinois or Northwest Indiana home.