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What Size Central Air Conditioner Do I Need? A Phoenix Tech Answers

June 29, 2018

Many Phoenix homeowners who are looking for a new AC ask us, “What size AC should I get?”

Here’s the thing: It’s impossible for us to tell you what size AC you need in a blog article because AC size depends on many factors (which we’ll go into later).

In fact, the only accurate way to know what size AC you need is to have a professional visit your home and perform a cooling load calculation. A cooling calculation is an assessment that takes into account several factors to determine what size AC you need.

Unfortunately, some sources will tell you to simply match your AC size to the square footage of your home, and they’ll share generic charts like the one below:

  • 1,000–1,200 sq/ft = 21,000 BTUs
  • 1,200–1,400 sq/ft = 23,000 BTUs
  • 1,400–1,500 sq/ft = 24,000 BTUs
  • 1,500–2,000 sq/ft = 30,000 BTUs
  • 2,000–2,500 sq/ft = 34,000 BTUs
  • 2,500–3,000+ sq/ft = 42,000–60,000 BTUs

However, square footage is only ONE factor that determines AC size—not the only factor.

In this article, we’ll cover the following info:

  • How AC size is measured
  • Why you need the correct AC size in the first place
  • Why you need a professional to help you choose the right size AC

Want to know what size AC you need?

How AC size is measured

Earlier we shared a chart that compared square footage with “BTUs.” Air conditioners are sized according to BTUs (British Thermal Units), which is a measurement of how much heat an AC can remove from your home in an hour.

Most homes need ACs that range from 18,000 to 60,000 BTUs.

Sometimes you’ll see air conditioner size measured in tons instead of BTUs. Tonnage is just another way of expressing an air conditioner’s BTU output.

Below is a chart to help you compare tonnage with 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 you know how AC size is measured, let’s look at why you need the right size AC...

Why you need the correct AC size

“Does AC size really matter?”

We get that question often from Phoenix homeowners across the valley, from Apache Junction to Avondale and everything in between.

And yes, size does really matter. Here’s why...

  • If your AC is undersized, your AC will run non-stop trying to cool your home. As a result, you’ll have a higher energy bills and your home will never reach your desired temperature.
  • If your AC is oversized, you’ll run into an issue called short cycling. Short cycling is when your AC turns on, cools your home really fast (since it’s so big) then shuts off quickly.

You might think that sounds like a good thing, but it actually leads to problems like:

  • Higher energy bills: The more your AC stops and starts, the more energy it consumes. Similar to a car getting better gas mileage when it runs longer, your AC uses less energy if it’s allowed to run for longer times.
  • Uneven cooling in your home: Since the AC shuts off so abruptly, the fan doesn’t have enough time to properly circulate cold air throughout your home, leaving you with hot and cold spots.
  • Reduced lifespan: The constant on and off caused by short cycling wears down motors and other components in your AC system, which will ultimately reduce its lifespan.

Now that you know AC size does matter, let’s look at why you need a pro to help you find the right size air conditioner for your home...

Why you need a professional to help you choose the right size AC

Like we mentioned in the beginning, the only accurate way to determine what size AC you need is to have a professional perform a cooling load calculation.

A cooling load calculation will tell you the BTU output you need for your new air conditioner. It takes into account factors like…

  • The square footage of your home
  • Your home’s geographical location
  • The insulation levels of your home
  • Height of ceilings
  • Number of doors and windows
  • Type of roof
  • Orientation of your home (i.e., north-facing, east-facing, etc.)
  • And much more

Beware of contractors who use a square footage “rule-of-thumb” approach

As you can see, determining what size air conditioner you need depends on much more than square footage alone.

So if a contractor says something like “you just need 12,000 BTUs for every square foot of your home,” that should be a red flag—DO NOT hire them. Otherwise, you’ll likely end up with an AC system that’s either too big or too small for your home.

Ready for a professional to help you size your AC?

We’ll send over one of our friendly techs to perform a cooling load calculation to help you find the right size AC for your home.

We offer…

  • Polite, professional customer service
  • Upfront pricing
  • 100% satisfaction guaranteed on all of our AC services.

Related reading:

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