MAY 23, 2018

The Phoenix area is not somewhere you want to live without air conditioning. Record highs seem to be a daily occurrence, and even average temperatures are hotter than most people might expect. Having the right AC unit, though, isn’t always easy. You don’t just need to look at name brands – you need to look at the size of the unit as well. Many ask, “what size should my air conditioner be?” but few take the time to figure out what that might really mean for them. If you want to get the right air conditioner, you’re going to need to know a little about how size impacts output.


Sizing is just one of the many issues that you’ll deal with when finding a new air conditioning unit, but it is perhaps among the most simple. There are some basic rules of thumb you can follow when looking for a new one, most of which do hold up no matter where you live. Be wary, though, because Phoenix brings its own set of rules for finding a good AC unit. However, if you can incorporate basic knowledge with a little local know-how, you’ll be able to find what you need.


When you are looking at an air conditioner, you should always make sure to pay attention to the Goldilocks Rules. It is very important that your air conditioning unit is neither too big for your home nor too small, but rather that it is able to be as efficient as possible for its size. There are some very real downsides to violating this rule, so always make sure it is part of your buying process.

If your air conditioner is too small, you will find yourself not only living in a house that doesn’t quite manage to cool all the way off, but also one that has an incredibly high electricity bill. Conversely, if the unit is too big you won’t have much of a problem cooling your house, but your air conditioner will constantly run, your cooling periods will be unsteady, and you will still have to deal with a high bill. It’s important to make sure that your air conditioning unit hits the sweet spot between too big and too small.


There is, of course, a mathematical formula to help you figure out the size of your air conditioning unit. This formula is not quite as precise as some might have you believe, though, and a number of variables can throw it off. With that said, you should be able to use this formula to get a rough idea of which size unit you should start looking at.

Your goal in using this equation is to figure out how many BTU (British Thermal Units) your air conditioner is able to put out. Doing so can be done with some complex math, or it can be simplified by looking at what air conditioners of specific sizes are usually able to do. This second equation is simple enough that it can be done without a calculator.

All you need to know here is your home’s square footage. Once you have that, you’ll multiply the square footage by thirty, and then divide that number by twelve thousand. This will leave you with the necessary tonnage for your air conditioner. If the number is five or greater, you’ll need to consider buying more than one air conditioning unit to cool your home.


Phoenix brings with it a host of problems for cooling off your home. The extreme heat is more than most air conditioners can deal with, so you’ll need to make sure you get both a dependable unit as well as a unit that’s able to put out a bit more cool air than average. While the equation above is actually meant to deal with issues that are specific to Phoenix, you may need to go up a size larger than you’d typically look at just to make sure you’ll be able to survive the summer heat.

If you’re pulling in too much energy to cool down your house, there’s a very good chance that you might be dealing with an air conditioner that’s just not suited for the job in Phoenix. Take some time to talk to experts in the area and get their opinion on the various brands and how they function in extreme heat – you might find that the numbers most people use to determine what unit to buy just don’t work in Arizona.

If you have specific heating or cooling needs, always make sure that you weigh those against common knowledge. You might find that you can get away with less than others if you really enjoy the heat, but be warned – using a smaller unit can have a huge impact not only on how cool your house is, but also on how much you’ll end up paying when your electricity bill comes in.


It’s also a very good idea to stop for a moment and determine your own air conditioning needs before you settle on any air conditioning unit. It’s very possible, for example, that you might be better served by getting two smaller units (one for upstairs and one for downstairs) than a single larger unit. You may also want to look into energy-saving or green-friendly units that might not conform to the usual size charts. As always, it’s a good idea to speak to someone who has experience in servicing local AC units to make sure you are getting the right unit for your needs.

While there are simple formulas you can use to figure out which AC unit you need for your home, it’s always a good idea to talk to a professional before you make a purchase. By talking to someone who actually knows the field as well as the area, there’s a good chance he or she will point you to an air conditioning system that will be better suited for the hottest days of the year. If you are looking for a new air conditioning unit or if you are just concerned about what you already own, don’t wait – contact Donley Service Center today.