November 12, 2019

Updated: April 15th, 2024

Finding the right air conditioner size is very important because each home is different, and the size of your central air conditioner will depend on various factors apart from the size of your house.

These factors include your roof type, the height of the ceiling, number of windows, type of insulation, heat transfer of the walls etc. Usually, the size recommended in the manufacturer’s guidelines do not consider these factors and hence may be incorrect.

AC Installation in Foothill Ranch, CA

AC Installation: What Size Central AC Do I Need?

Air conditioner sizes do not mean your unit’s physical size. The size of an AC unit is expressed in tons which evaluate how much heat it can remove in an hour. For example, a typical AC unit is one ton and it cools 12000 BTU/hour. Here, BTU is a measure of heat. If you look at how many BTUs are needed to cool a bedroom or home office with the area around 100-300 square feet, it will come around 5000-6000 BTUs.

Why Size Matters?

Size matters because a correctly sized air conditioner will run a proper full cycle and ensure that your home remains cooler longer. If the air conditioner is too small, then it will have to run non-stop for keeping your home adequately cool during the summer. This will increase your electric bills drastically. If the air conditioner is too big, then it cools the area too quickly, causing it to run for very short cycles. In such cases, the unit is unable to remove the humidity from the air properly, which can create mold and fungus problems. Also, excessive on-off cycling will wear out your air conditioner faster in such cases.

Air conditioner

How To Measure What Size Air Conditioner You Need?

To calculate the size of the air conditioner you need for a room, first, multiply the length of the room with its width. Then multiply it with 25 BTU to get the ample cooling for the room under different weather conditions. For example, if the room is 15 feet long and 12 feet wide, it comes to 180 square feet. Now multiply 180 by 25 BTU per square foot you get 4500 BTU which is the minimum cooling capacity of the air conditioner you should buy.

Central Air Conditioner Unit Size Calculator

When determining the appropriate size of an air conditioner for your home, especially for a central AC system, utilizing online AC size calculators can be immensely beneficial. These calculators typically require input such as the size of the room in square feet and the climate conditions in which you reside. By specifying whether you live in a hot or cold climate, the calculator can accurately determine the tonnage and British Thermal Units (BTUs) required to adequately cool your space. This precision in sizing ensures optimal performance and energy efficiency, preventing unnecessary strain on the system and potential issues such as uneven cooling or excessive energy consumption.

Also read:

What to Expect from a New HVAC Unit Installation Cost

How to Choose the Right HVAC Contractor for Your Residential Complex

Trust White Mechanical, Inc. For Your Next AC Installation

Founded in 2002, White Mechanical, Inc. in Laguna Hills, CA, is one of the most trusted and licensed (HVAC) service providers, proudly serving Orange County and the surrounding communities. Our management team has more than 28 years of experience in various aspects of HVAC technology. All our HVAC technicians are professionally skilled and certified to deliver outstanding residential HVAC services as well as commercial HVAC services to our clients. We offer professional HVAC services including air conditioner installation, maintenance services, air conditioning repair, and more at very reasonable prices.


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