What Size HVAC Do I Need? Part 3: How to Find an Exact Number

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This is the final part of a three-part series on finding the right size HVAC system for your needs. Check out part one here and part two here.

Are you in the process of purchasing a new HVAC system? Then you need to know what size is best for you! How can you find out? We’re here to help. In part one of this series, we talked about six factors to consider when choosing the right size HVAC for your home. In part two, we compared large and small systems to show you the benefits and pitfalls of both. Today, we’ll talk about how you can get the exact number for the size HVAC system you need.

How to Get an Exact Number: The Right Way

The only true way to get a perfect number in tons for your HVAC system is to contact a professional. An honest HVAC installer will take into consideration all of the factors needed to properly estimate your system and find one that works for you. There are load experts who can calculate this for you and will allow you to shop around before contacting an HVAC installer/contractor.

The Wrong Way

As you may already have heard, in this industry, there are a lot of sham contractors out for your money. One common scam is to install a larger system than is necessary. Larger systems cycle more often, causing a frequent need for repairs. On top of this, larger systems are also more expensive to install.

I recommend asking your installer (before any payments are processed) what they use to determine the load and, in turn, the size of the unit. If they have the following formula, you know you’re working with the wrong guy!

Do not use the following formula as it is extremely incorrect. If your installer uses this formula, they will install a much larger system than you need:

(Home sq. footage x 25) / 12,000

If you look at the formula, you’ll notice there is absolutely no consideration for your usage, climate or insulation. The only factor this is based on is your square footage. The number (in tons) this formula will give you is likely about 1 ton over what you actually need. For example, in this formula, a 2000 sq. ft. home would need a 4-ton unit, which is unnecessarily large in most cases. A properly-sized unit may be in the upper 2’s through mid 3’s based on your insulation, climate and usage of heat-generating electronics.

Where Can I Find a Number Online?

There are websites that can provide you with an exact number if you know what your home uses, such as:

But keep in mind, to get the most accurate reading, you’ll need someone to come out to your home and crunch numbers to help you find the best system for you. And remember, don’t fall for the “you can never have too much” saying they may try!

Thank you for reading our series! We hope we helped you understand more about how to find the best sizing for your home’s heating and air conditioning needs. Stay cool, everyone!

About the author

This three-part series is written by guest blogger, Ryan Gavin, an associate of Comfort Pro, an HVAC installation company in Reading, PA. Ryan writes on varying topics from how to stay the most comfortable in your home, to technical requirements for HVAC systems.

About us

“The CRT Tipster” is an HVAC tips and news blog owned by Controlled Release Technologies, Inc. We are a chemical manufacturing company based in Shelby, N.C., and have been creating independently-certified, green products for HVAC maintenance since 1986. Read more atcleanac.com. Got a question? Contact us toll free at 1-800-766-9057.

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