How Do I Know What Size Air Conditioner I Need?

JUNE 12, 2019

When buying a new air conditioning system, it must be an appropriate size to handle your cooling needs. But how do you determine the right size of AC unit you need to efficiently cool your home?

How Air Conditioner Sizes are Measured

First, let’s look at how air conditioner sizes are determined. An AC unit’s cooling capacity is measured in tons based on how many British Thermal Units (BTU) it can remove within an hour. For example, a one-ton unit can remove 12,000 BTU, a two-ton unit can remove 24,000 BTU and so on. Home air conditioners generally start at 1.5 tons and go up in half-ton increments. It is unlikely that your home would need a unit larger than five tons. There are some general guidelines you can use based on the square footage of your home to get a ballpark estimate of the unit size you may need.  For example, you can roughly estimate one-ton per 750-1000 square feet, so a 2,000 square foot home may require a 2.0 – 2.5-ton unit.  Remember though that many factors such as number and size of windows, exposure of those windows to the south and west, as well as how the home was insulated, will influence the unit size.

Things to Consider for Your Air Conditioner

Although the size estimates based on square footage are helpful to give you an idea of what to expect, several other factors go into properly sizing your air conditioning unit. To ensure that your home has a quality system installed, an Energy Management Consultant should complete a professional evaluation.

The consultant conducts an assessment of your home and focuses on various aspects, such as size and age of the home, ceiling height, number of windows, how much shade the house gets and the amount of insulation. The consultant will also consider the capacity and functionality of the existing HVAC system and the climate of your area. Once the assessment is complete, the consultant will give you an estimate to consider for several unit types. They will also help you understand how each unit can cool your home and will then help you make a decision based on your cooling needs and budget.

What you can do as the homeowner is make a list of issues you currently have with your air conditioning unit and discuss what you find with the consultant. Here are a few questions to ask yourself:

  • Is your current unit not cooling properly?
  • Have you found that your system needs repairs quite often?
  • Does the unit turn off even if the desired temperature setting is not reached yet?

Identified problems can help the consultant better determine a unit choice for your home and if a protection plan is a good choice for you.

Importance of a Proper Size Air Conditioner

Installing the correct size air conditioning unit for your home makes a significant impact on your comfort and energy bills. You might think that bigger is always better, but that is not the case. If you purchase an air conditioner that is too large, it will cool your space too rapidly. This will cause it to continuously shut off and turn back on, which leads to lower efficiency and higher costs and sometimes more air conditioner repairs.

On the other hand, if you choose a unit that is too small for your home, it will run constantly to cool the space, and in some cases may never achieve the desired temperature. This increases your costs and may leave you too warm in the summer.

Installing an air conditioning unit in your home is a big undertaking and choosing the wrong size unit can greatly impact your energy costs. That’s why we recommend leaving the process to the professionals in the HVAC industry.

Read our buyer's guide to air conditioners to learn more about the AC buying process.