Help Guides

What Size Central AC Unit Do I Need? A Pittsburgh Tech Answers

| Posted in:  Help Guides/Cooling

Contrary to popular belief, the size of central AC system you need is not just determined by the square footage of your home. 

The size of central AC you need is actually determined by something called a load calculation. A load calculation is an evaluation performed by a professional and essentially determines how much heat needs to be removed from your home (per hour) to keep the space cool.  

We know that’s not all of the information you need, and we know you have questions, like:

  • What does “load calculation” actually mean?
  • How are AC systems sized? 
  • Why does AC size matter?

Below, we’ll answer these 3 questions so that you’re prepared to purchase the right-size central AC system when the time comes. 

Rather skip the reading and have a professional determine what size central AC unit you need for your home? We can help! Our team of highly-trained pros can come to your home and provide you with a free estimate on a central AC system. Learn more about our AC installation process or...

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What does load calculation mean?

Your AC system actually cools your home by removing heat. 

A load calculation simply determines how much heat needs to be removed from your home to keep it cool.

There are a variety of factors that influence how much heat needs to be removed from your home. Some of these factors include:

  • Where you live (your climate)
  • Number of people living in your home
  • The orientation of your home 
  • Number of windows 
  • Quality and type of insulation
  • Number of doors
  • Type of flooring
  • Whether ductwork is located inside or outside
  • And other factors 

A quality technician will take the time to perform a load calculation and let you know what size AC you need in British Thermal Units (BTUs). We’ll dive into the details of how AC systems are sized (BTU output), below.  

How are AC systems sized?

AC systems are measured by British Thermal Units (BTUs). An AC unit's BTU output is an expression of how much heat it can remove from your home in an hour.

For reference, a BTU is equal to the amount of energy produced by lighting one match. Most residential AC systems fall between 18,000 and 60,000 BTUs.

Now, the size of an AC system is also measured by tons, which is a different way of expressing a system's BTU output. When it comes to AC systems, one ton is equal to 12,000 BTUs.

So if you’re shopping for ACs and they have tonnage listed instead of BTU output, you can easily determine what the BTU output is.

Here’s a quick guide to help convert tonnage to BTU output:

  • 1 ton = 12,000 BTUs
  • 1.5 tons = 18,000 BTUs
  • 2 tons = 24,000 BTUs
  • 2.5 tons = 30,000 BTUs
  • 3 tons = 36,000 BTUs
  • 3.5 tons = 42,000 BTUs
  • 4 tons = 48,000 BTUs
  • 4.5 tons = 54,000 BTUs
  • 5 tons = 60,000 BTUs

Now that we’ve discussed how ACs are sized (and how to determine what size you need for home), let’s discuss why all of this matters anyways. 

Why does AC size matter?

When it comes to ACs, bigger isn’t always better. Like we’ve discussed above, there are many factors that go into what size AC is right for your home, and installing an AC system that is smaller or larger than this can cost you problems and money down the road. 

If your AC system is undersized… it will work continuously to cool your home but will struggle. This can increase the cost of your monthly energy bills as well as shorten the lifespan of your system.  

If your AC system is oversized… it will turn on for a short period of time, cool your space and then shut off. This is called short cycling and can cause a variety of issues like:

  • Increased energy bills
  • Shortened AC lifespan
  • Hot and cool spots around your home
  • Expensive repairs or replacements 

When you’re investing in something as expensive as a central AC system, it’s important to hire a technician that will take the time to find the right size AC for your home. That way, you don't run into any of the issues we listed above.

Ready to install a central AC system? Hire Pittsburgh’s best!

If you’re ready to install a central AC system or want more information, reach out to us! We’d be happy to help you determine what the best option is for your home.

Schedule a free estimate!
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