There’s no denying the fact that the size of your commercial HVAC unit directly affects its overall performance, efficiency, and life span. When sized correctly, you can ensure you’re getting the best performance out of your system, and it will last for quite a long time. Getting that perfect size all starts with understanding the basic principles of HVAC systems. Be aware, however, that you don’t have to do this yourself. Our technicians will handle this task for you.

The Quick and Dirty

It’s important to note that figuring out the actual unit size that you’re going to need for your commercial building is going to be dependent on a number of factors. However, there is a quick and dirty method that can be utilized to get you in the ballpark, so you understand approximately what size unit you’re going to need.

In general, you’ll want a one-ton unit to handle around 5,000 square feet of space. So, if you’ve added up all the rooms in your commercial building and they equal about 50,000 square feet, then you’ll need a 10-ton HVAC unit. Most commercial HVAC units will be anywhere between 2 and 30 tons.

Depending on the system manufacturer, you may not find a ton rating readily available. Rather, their measurement may be in BTUs. BTU stands for British Thermal Unit. One ton is equal to 12,000 BTUs. If we follow the same scenario as above, you’ll need an HVAC unit with a rating of 120,000 BTUs.

The Professional Calculations

Most HVAC technicians will utilize a formula created by an accredited national organization, such as the Air Conditioning Contractors of America (ACCA). The ACCA published a construction guide, Manual N, that is utilized regularly by HVAC technicians to determine proper HVAC system sizing based on commercial loads. According to Manual N, there are four main factors that determine the ideal HVAC unit size.


The first factor is the type of application. Examples would be retail space, restaurants, grocery stores, and offices. The bigger a space is, the longer it’s going to take to alter its temperature. Dealing with a sectioned-off office space is going to require less energy than an open grocery store building format.

Type of Building

Another big influencer in proper commercial HVAC system sizing is the type of building that you’re working with. Is it a single-story, multi-story, warehouse, or something else?

Square Footage

It’s going to take a bigger system to cool down a 50,000-square-foot building as compared to a 10,000-square-foot building. For buildings that are sectioned off, such as offices, it can be helpful to collect the square footage of each room independently. Then, add all the totals together to get the total square footage of the entire building.

Equipment Type

Lastly, the type of heating or cooling equipment utilized is going to play a role in proper sizing. Will the heating system be fueled by gas or electricity? Will the building be cooled by air or water?

Oversized HVAC Unit

An oversized HVAC unit can create multiple problems. Not only did you likely pay more upfront for the unit, but it’s going to be much less efficient than an appropriately sized unit. You’re probably going to experience more frequent repair calls as your system is working much harder than it needs to be.

Problems like high humidity, poor indoor air quality, unwanted mold growth, and allergy flare-ups are quite common with oversized HVAC units. Since these systems are too big for your space, they don’t run for very long as they’ll reach your desired temperature setting very quickly. This leads to constant starting and stopping of your HVAC system without allowing it to run through a full cycle.

Undersized HVAC Unit

An undersized HVAC unit can also be a real problem. You’ll find that your HVAC system is constantly running to try and keep up with your heating or cooling needs. This excessive running will lead to premature wear and tear on your equipment and likely reduce its life span significantly. Even worse, your building occupants aren’t going to be comfortable.

Call the Pros for Assistance Today

Cool Experts AC offers top-quality commercial and residential HVAC installation services for Plano, TX and the surrounding areas. We can also help with all of your heating, cooling, indoor air quality, duct cleaning, dryer vent cleaning, whole home air purification, and attic insulation needs. Contact us today to get the professional assistance that you need.

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