What Size Central Air Conditioner Should I Buy?

When you’re looking online for new central air conditioning, it’s easy to get overwhelmed. There are so many options! You’ve probably heard that the size of your air conditioner is very important (and that bigger is not necessarily better), but what exactly does that mean?

Whether you’re buying or renting an air conditioner, sizing is a huge part of the install process. To sort out the confusion, here’s a guide to right-sizing your new central air conditioner replacement.

Right-Size Your Central Air Conditioner

AC size is expressed in terms of BTU (British Thermal Units). The higher the BTU number, the greater the cooling capacity.

Rule of thumb: You’ll need approximately 20 BTU of cooling per square foot of space. For example, a 1,500-square-foot home will require roughly 30,000 BTU.

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But don’t try to figure out AC size yourself; there are too many factors to consider. Instead, ask a reliable, experienced HVAC technician to calculate the BTU you need, using a recognized standard such as CAN/CSA-F280-M90 or the Air Conditioning Contractors of America Manual J.

The Problems of Incorrectly Sized Central Air Conditioning

Are you planning to replace an air conditioner that was initially incorrectly sized? Today’s AC technology is much more efficient and advanced than just a few years ago, so get a professional analysis of your home’s current cooling needs.

A cooling system that is too large is just as bad as one that is too small. It can impact how long ACs last. Neither will produce the level of home comfort you and your family want… and you’ll experience other problems as well.

1. Your House Won’t Get Cool Enough

Undersized central air conditioning is obviously problematic. It just won’t have enough power to cool your home thoroughly, even if the AC runs all the time.

Oversized central air is equally troublesome. Surprised? Don’t be. A too-large AC will cycle on and off quickly while not adequately cooling the house. What’s more, it won’t run long enough to dehumidify properly. And humid, sticky indoor air will make you feel even hotter.

2. Your AC Will Need More Frequent Repair

With undersized air conditioning, the system will constantly run as it desperately tries to pump out enough cool air for your whole house. This causes excessive wear and tear. When an oversized AC is forced to short cycle, the stop-start action is also hard on your cooling system.

What’s the result? More frequent repairs and two headaches for you:

  • high repair bills that keep piling up


  • downtime without functional cooling in your home

Ultimately, you’ll be faced with the question: is it time to replace or repair my air conditioner?

3. Operating Costs Will Go Way Up

Incorrectly sized air conditioning will not only cost you a fortune in HVAC repair bills. It will also be much less energy efficient than it should. So your monthly utility bills will rise sky-high, accordingly. Sadly, there is no real fix for this problem besides replacing your air conditioner with one that’s the right size for your house.

4. Your Air Conditioner Won’t Last As Long

An air conditioner that is correctly sized and carefully maintained should give you at least 10-15 years of faithful service. But air conditioning that is either too small or too large simply won’t be able to handle the extra demand.

As a result, its working life will come to a premature end, and you’ll have to start shopping for a replacement air conditioner a lot sooner than you thought. This unexpected expense can be pretty hard on your budget.

Find the Right Sized Air Conditioning

Do it right this time. Avoid purchasing or installing a new central air conditioner without expert advice. Rather, consult a Dr HVAC professional, who will consider the following factors:

1. Size & Layout of Your Home

The square footage of your home and number of stories is the first item in our central air conditioner size assessment. Depending on your layout, you might find it most convenient to install multi-zoned air conditioning, which will enable you to fine-tune your temperature control.

2. Placement of Windows & Landscaping

Window placement, size, and number all play a significant role in your home cooling needs. To illustrate: A building with many large south-facing windows will naturally become hotter in the summertime. On the other hand, the share created by landscaping in the form of trees and shrubs around the house will help keep the interior cool.

3. Ductwork & Insulation

Next, we will look at the condition of the ductwork and insulation installed in your house. If both of these are adequate, you’ve already got a head start on energy efficiency.

4. Climate

Last but definitely not least, we’ll take into account our delightful (?!?) GTA climate. Central air conditioning that can cope with our sky-high humidity is essential. Bear in mind that all through our freezing winters, the thought of balmy summer weather is what keeps us going… so let’s make sure you enjoy it!

Enjoy Summer in Comfort With Dr HVAC

Turn your home into an oasis of deliciously cool comfort this summer. Talk to the friendly experts at Dr HVAC. We’ll accurately evaluate your home cooling needs and help you choose the best air conditioning in terms of size, model, and price point.



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