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What Size AC Do I Need? A Southern California Tech Explains

By Your Comfort Advisor 4/13/21 3:33 PM Time to read:

Our answer? It completely depends.

There are multiple factors to consider when sizing an AC system for your home. Square footage can assist in providing loose estimates for AC sizing. 

Square footage is just one factor that impacts AC sizing. Other factors such as insulation levels, number of doors/windows, etc. all determine the size AC you’ll need. That said, the only way to determine what AC size you need is to have a professional perform an in-home “load calculation”.

In this article, we’ll explain what a load estimate is and how it helps accurately determine AC sizing. First, though, let’s take a closer look at how air conditioners are sized.


Live in the Redlands/Inland Empire area and need accurate AC sizing for your AC replacement project? Just contact Burgeson’s and one of our Comfort Advisors will schedule an appointment for your free in home estimate. 

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How are air conditioners sized?

Air conditioners are sized according to the amount of  heat they can remove from your home in an hour—this is measured in BTUs (British Thermal Unit—a measurement of heat). 

Most Southern California homes need AC systems that provide BTU outputs ranging from 18,000 to 60,000.

Fun fact: One BTU roughly equals the same amount of heat that's produced by burning through one match.

If you’ve been shopping around for AC systems and have visited manufacturer sites, you may have seen the term “tonnage” instead of “BTU output.” Don’t get confused—AC tonnage is simply another way to tell you the unit’s BTU output.

For example, one AC “ton” is equal to 12,000 BTUs. 

Another fun fact: 12,000 BTUs is the amount of heat required to completely melt one ton of ice (hence the use of “tons” when it comes to AC sizing).

Here’s a tonnage-to-BTUs chart to help you keep track of AC sizing:

Tonnage of AC BTU Output of AC Unit
1 Ton 12,000 BTU's
2 Tons 24,000 BTU's
3 Tons 36,000 BTU's
3.5 Tons 42,000 BTU's
4 Tons 48,000 BTU's
5 Tons 60,000 BTU's

For accurate AC sizing, you will need a “load calculation”

A load calculation is a professional calculation that measures how much heat a home gains per hour.

Once this is measured, a professional can pinpoint the exact BTU output that is needed to keep the home cool and comfortable, even on those particularly hot California summer days. 

When done properly, a cooling load calculation takes into account over 10 different factors, including:

  • Your geographical location (California homes shouldn’t use the same sizing guidelines as Minnesota homes, for example)
  • The orientation of your home (is it facing Westward, Eastward, etc.)
  • How many windows your home has (and what kind of windows)
  • How many doors your home has
  • Whether your home has carpet or wood flooring
  • How many people live in the home
  • Your home’s insulation levels
  • Where your ductwork is located
  • And much more…

So why is it so important to get your home’s cooling load professionally calculated?Well, this calculation ensures that you won’t end up with an air conditioner that’s oversized or undersized.

Is it that bad to have an oversized or undersized AC?

Yes. The short answer is that an oversized or undersized AC causes high energy bills, less comfort and a shortened AC lifespan.

We often hear homeowners ask for an oversized AC for increased comfort but getting an AC that’s too big for the home can actually cause the opposite. An oversized AC will “short-cycle”, meaning it will turn on and off rapidly. This can cause  hot and cold spots throughout the home. Short-cycling can also result in higher energy bills and frequent repairs.

An undersized AC will run non-stop and likely won’t be able to reach your desired temperature on hot days. This can cause  your energy bills to spike and result in frequent repairs.

Need an accurate AC size? Contact the pros at Burgeson’s

Burgeson’s has over 72 years of experience sizing and installing ACs for homeowners in Redlands and the Inland Empire. 

We pride ourselves on providing accurate AC sizing by first performing thorough load calculations. We never rely on rules-of-thumb such as only looking at square footage—and that means you get an accurately-sized and expertly-installed air conditioning system that saves you money in the long run.

If you’re ready to move forward on your AC installation projects, just contact us and we’ll send over a professional to perform a free, in-home load calculation and AC estimate.

Request a FREE Estimate