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How To Figure Out What Size Air Conditioner You Need

Jun 28, 2016

Air Conditioning


Air conditioners come in many different sizes — so how are you supposed to know which one is going to be best for you? Air conditioner should be sized to the area of your home you’re trying to cool, and they should cool that space with efficiency. So how do you do that? There are a couple of different ways, some that you can do yourself, and some that require an expert!

The DIY Approach

You can get a pretty good idea of what size air conditioner you’ll need by using this simple formula: length X width X 25 BTU. Just measure the length and width of the room or area you’re looking to cool. Multiply these numbers together, and then multiply the total by 25 BTU. The resulting number will tell you the minimum amount of BTU’s you need to look for in an air conditioner!

Manual-J Approach

If an HVAC technician comes to your house, they will probably perform a Manual-J calculation. This calculation is a detailed analysis of your home’s central air conditioning and heating needs. There are two types of Manual-J calculations, a whole house load calculation, and a room-by-room load calculation. The type of calculation done by a technician usually depends on if you will be replacing your ducting when your AC unit is installed. A room-by-room calculation is best if both the central air conditioner and the ducting are being replaced. A whole house calculation is best used if your ducting has been deemed sufficient.

Why Size Matters

If your air conditioning unit is too small, it will have to run almost continuously to try and cool your home. A system that is undersized for the home will be inefficient, wasteful and not to mention expensive!

An air conditioner unit that is too large may cool your home quickly, but it will shut off before the full cooling cycle runs. AC units don’t only cool the air in your home; they also remove moisture from the air. If your unit is turning on and off in quick bursts, moisture cannot be extracted from the air correctly. What’s more is that while the air may feel cool, the structure is not. This allows heat to creep back in quickly. An air conditioner that is too large for the space it will run in a constant on-off cycle that will drive up your electric bill.

An appropriately sized central air conditioner will run through the required amount of cycles to keep your house comfortable, but will not run so much that its efficiency is compromised.

Things That Affect What Size Of Air Conditioner You Need:

There are some factors (other than the size of your house) that can impact the size of air conditioner that is right for you. Some of these include:

  • The amount of sun-exposed exterior walls
  • The number, condition, and orientation of the windows in your home
  • The amount of sunshine your home receives
  • The age of your home
  • Among many others!

Romaniuk Can Help!

If you are in the market for a central air conditioner, Romaniuk Heating & Air Conditioning can help! Our team has years of installation experience and will make sure that you get the perfect sized AC unit for your space. Contact us to learn more!