You are in Phoenix. We also have a Tucson site.

You are in Phoenix. We also have a Tucson site.

You are in Phoenix. We also have a Tucson site.

How to Pick the Right Size AC Unit For Your Home

"This city should not exist --- it is a monument to man's arrogance." 

The character Peggy Hill said this when commenting about Phoenix, Arizona's heat. It's an apt description. Temperatures in Phoenix can reach highs of 107°F and over during the summer months. 

There is still, of course, plenty of things that Phoenix residents can enjoy. They can visit gardens and shop at markets before collapsing like ripped inflatables in their air-conditioned homes. Of course, to get the best cool-down, they'd need a correctly sized AC unit. 

If you’re asking, "What size AC unit do I need?” Read on, this article will show you how to find the answer for yourself. 

What Size AC Unit Do I Need?

AC unit size matters. Your appliance's size relative to the square footage of your home needs to be like Baby Bear's porridge: just right. If you don't get it right, all kinds of crazy stuff can happen to your AC unit's functioning. 

Too Big

If your air conditioning unit is too big, it won't run a full cycle. It will need to constantly turn on and off like strobe lights at a rave. This isn't supposed to happen since your AC unit is an AC unit and not a strobe light. 

The good news is that your unit can succeed at drying and cooling off your home when it does this. The bad news is that your AC unit will also dry up your wallet. 

Too Small  

An AC unit that's too small is like a chihuahua. It'll make noise constantly but cause a lot less damage to its enemy (for an AC unit, this is the heat). This happens because both the AC unit and the chihuahua just don't have enough power. 

The AC unit is going to keep trying, though. And as it does, your finances will become about as effective as a chihuahua. 

Just Right 

A perfectly sized AC won't act like either a strobe light or a chihuahua; it will work as an AC unit should. It will only run when necessary and still dry and cool your home effectively. 

On top of that, it won't unnecessarily stress out your finances and subsequently stress you out. So how can you choose the right size air conditioner? 

Choosing the Right AC: Labels

There are two methods you can use to get the right size air conditioner. If you already have a functional AC unit and need to replace it, you can use the first method.

Look at the Label  

Unless someone ripped it off (thanks, Little Bobby), your AC unit should have a label. By looking at this label, you can figure out what your next air conditioning system needs.

If you want, you can just copy the labels down and get an AC unit that is close to them. However, you may want to use the calculations below to learn if your AC unit ratings are correct. 

Of course, those labels may initially look like some fictional sci-fi alien language. Look at the sections below to learn what each label means. 

British Thermal Units Per Hour 

When an HVAC expert talks about the "size" of an AC unit, they're not talking about meters, feet, seashells, or whatever units of measurement you use where you live. They're referring to the unit's cooling capacity. This is a measurement of a cooling system's ability to remove heat. 

HVAC experts measure cooling capacity in British Thermal Units Per Hour (BTU). One BTU is equal to the amount of energy needed to cool a pound of water by 1°F, or 1055 Jules. Yes, that's about as confusing as the seashells, but luckily you don't need to worry too much about understanding BTU that well. 

SEER Ratio

SEER stands for Seasonal Energy Efficiency Ratio. This is a measurement of how much energy and money you need to run a unit for a cooling season. A "cooling season" is the space of time when you'd need to run your AC (aka the time you'd be quoting Peggy Hill if you're in Phoenix).  

The less energy it needs, the higher the SEER rating your unit has. If you want a highly energy-efficient air conditioning unit, you need an Energy Star certified unit. To meet the Energy Star standards, a unit needs to have a certain minimum SEER. 

Choosing the Right AC: Calculations 

If Little Bobby or someone else ripped off your label, you can easily calculate the cooling capacity that your air conditioner system needs. This will involve that oh-so-understandable BTU measurement. 

Here are the steps: 

  1. Calculate a space's square footage

  1. Multiply Step 1's answer by 25 BTU

This will give you the basic BTU that the AC unit in that space will need. For example, a 1,500 square foot space will need a BTU capacity of 37,500. A 2,000 square foot space will need a BTU capacity of 50,000.


Keep in mind, though, that all homes are different, and these differences can affect the BTU your home needs. For example, a well-insulated room can be sufficiently cooled by an air conditioning system with a lower BTU. A room that gets a lot of sun exposure will probably need a unit with a higher BTU. 

You don't have to get it perfectly, getting it in the ballpark should be enough. 

Hire Our Air Conditioning Services 

As an Arizona homeowner, you need an air conditioning unit. With our help, hopefully, you know more about how to get the right size AC unit. In addition to size, it's equally important to find a quality unit and take good care of it.

Do you need help installing your new perfectly sized AC unit or just routine maintenance on the current unit? That’s where Parker & Sons step into the picture. We've been serving homeowners in the area for years and are excited to assist with all your air conditioning needs! We aim to ensure you enjoy the cool comfort of your home. Reach out today, and let's ensure your AC unit meets its full potential.

Schedule an appointment with Parker & Sons today! 

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