What Size AC Do I Need For My Portland Home?

Whether you’re replacing your current AC or installing a new one, it’s vital to choose the right AC size for your Portland home.

An HVAC technician can determine the optimal size for your AC. They will perform an assessment, called a load calculation, which will take into consideration multiple factors—not just your home’s square footage.

Now that you know what a load calculation is, you probably have questions like:

  • What happens if I get the wrong size AC?
  • What exactly is a load calculation?
  • How do you measure an AC’s size?

Below, we’ll answer all three questions so you have the knowledge to buy the right AC for your home.


Rather just have an HVAC technician determine the right AC size for your home? Contact Four Seasons to learn more about our AC installation services.


What happens if I get the wrong size AC?

The right AC size for your home is important because, otherwise, you might have AC issues in the future. For example:

  • If your AC is too big … it will rapidly cool your home then turn off. This constant on-and-off, called “short-cycling,” will cause high energy bills, irregular cooling throughout your home and a shorter lifespan for your AC.
  • If your AC is too small … it will run all the time to make up for not being able to effectively cool your home. Continual usage can cause the same issues as an oversized AC.

Now that you know why the right AC size is important, let’s look at what goes into a load calculation.

What exactly is a load calculation?

Your AC actually cools your home by sucking in warm air, removing heat from the air and blowing the cooled air back into your home.

A load calculation looks at how much heat needs to be removed from your home per hour to keep it cool. It takes into account factors like:

  • Climate of where you live
  • Quality and location of the ductwork
  • Quality and type of insulation
  • Height of the ceilings
  • Type of flooring (carpet vs wood)
  • Size and layout of your home
  • Number of, the orientation and age of windows
  • Number of people living in your home
  • Number of doors in your home
  • Appliances in your home
  • Type of roofing
  • Square footage of your home

The above factors seem minor until you look at them in detail.

For example, the number of people living in your home doesn’t seem like a big deal. But the more people living in your home, the more body heat produced that an AC will have to remove.

Fortunately, high-quality HVAC technicians will consider the above factors when performing a load calculation. However, if a technician promises they can size your AC only with your home’s square footage, we suggest going with a different contractor to avoid getting the wrong AC size.

Next, let’s look at how AC sizes are measured.

How do you measure an AC’s size?

Once an HVAC technician has performed a load calculation, they will tell you what size AC you need to buy in British Thermal Units (BTUs).

A BTU measures the amount of heat an AC can remove from your home in an hour. A technician will typically recommend a size between 12,000 and 60,000 BTUs.

For reference, 1 BTU equals the heat 1 lit match can produce. Therefore, a 13,000 BTU AC can remove the heat of 13,000 lit matches from your home in an hour.

Ready to get the right AC size for your home? Contact Four Seasons

We have been providing accurate and smooth AC installations for Portland homeowners for over 40 years and we’d be happy to help you too. Our installations only need one day of your time and we will always perform a load calculation.

In addition, we offer financing options and specials for cost-conscious homeowners to help make the installation as budget-friendly as possible for you.

Schedule service today!