The Comprehensive Guide to Commercial AC Unit Sizes

If you need to replace the commercial air conditioner in your workspace, you’re likely wondering how to determine which one is right for your needs.

Fortunately, you only need to make some basic calculations to get started. This quick guide will explain everything you need to know to calculate what size HVAC you need for your business.

The Importance of Size for Commercial Building HVAC Systems

Why does the size of your commercial AC unit matter? First, know that the size of a unit isn’t actually related to its physical footprint. When we talk about AC “size,” we’re talking about its cooling capacity — how much cooling it can provide by absorbing heat from the air.

AC size is measured in tons, which specifically refers to the number of British thermal units (Btu) the system produces in a given period of time. When it comes to cooling, 1 Btu is equal to the amount of energy it takes to cool a pound of water by 1 degree Fahrenheit.

Ultimately, the rule of thumb for commercial HVAC sizing is to find a unit that’s just right. It shouldn’t be too big or too small — something right in the middle is usually the best option for your building. Here’s why:

  • Too large: A unit that is too large will short-cycle, which is when it cools your space so quickly that the thermostat shuts it down before the cycle ends. This issue significantly strains the AC’s sensitive internal parts, reducing the unit’s lifespan and causing your energy bills to spike.
  • Too small: Because an undersized unit lacks the capacity to meet your cooling needs, it will run almost constantly. This problem creates an uncomfortable temperature, raises your energy costs, and wears out the unit faster.
  • Just right: Your AC cools your space over the course of a complete cooling cycle and is able to shut off for a period of time before beginning the next cycle. It will sufficiently manage humidity and improve air quality, preventing mold from growing and affecting occupants’ health.

It’s also important to ensure you have the most efficient setup possible, which goes beyond choosing an energy-efficient AC unit.

How Do You Size a Commercial Air Conditioner?

How Do You Size a Commercial Air Conditioner?

Although you will need to do some math to get an estimate of how big your commercial air conditioner should be, it’s a fairly easy formula to follow.

Here’s the basic process you can use to calculate air conditioner size for a building with 8-foot ceilings:

  1. Divide the square footage of your space by 500.
  2. Multiply that result by 12,000 to convert your result to Btu.
  3. Add 380 Btu for each person who will regularly work in that space.
  4. Add 1,200 Btu for every kitchen in the building.
  5. Add 1,000 Btu for every window in the space.
  6. Divide that result by 12,000 to convert it to tons.

Note that you’ll need to make some adjustments to your calculations if your building has higher ceilings. Reach out to a licensed professional if you need help finding what you need.

Other Factors Impacting Commercial Air Conditioner Size

Of course, the size of your space alone isn’t the only factor that impacts how much cooling you need per square foot. Other important considerations include:

  • Building type: The number of stories and the specific dimensions of your building can impact how much cooling power you need.
  • Business type: Are you trying to cool an office space? A restaurant? A gym? The type of business you’re trying to cool will have a major impact on your cooling needs.
  • Air conditioner type: Don’t assume your new unit will need to be the same size as your old one. Depending on the specific HVAC technology you use and its efficiency, you may need a smaller unit than you expect.
  • Building materials: Newer buildings are often made with energy-efficient materials that passively reduce heating and cooling needs, which may allow you to use a smaller unit.
  • Windows: Larger windows often let more heat in, raising your cooling needs. The type and level of insulation you have on your windows will also impact the size of AC you need.
  • Building orientation: If your building is positioned in a way that lets in a lot of sunlight, your cooling needs will be higher. Note that your AC requirements may vary between rooms depending on where they are in relation to the sun.
  • Ductwork: If your building has poorly installed or damaged air ducts, more conditioned air can escape than you may realize. Before you choose a new unit, have a professional inspect your ductwork to make sure everything is as it should be.
  • Your location: If you’re based in an area with a cooler climate, your AC won’t need to work as hard to keep the place comfortable — similarly, businesses in warmer climates will have higher AC needs.
  • Other assets: The lights, electronics, and other heat-generating items you have in your space will typically increase your overall cooling needs.

All of these factors come together in the thermal load, which is the total amount of heat you’ll need to move to create a comfortable environment.

Understanding the Relationship Between Thermal Load and HVAC Size

The thermal load is the amount of heat energy your air conditioner must remove from the air inside your facility to keep the temperature constant. There are two types of HVAC loads you have to consider:

  • Internal load: The internal load is the heat generated by anything inside your building, including people, electronic devices, equipment, plants, and lighting.
  • External load: The external load comes from heat entering the building via sunlight, hot air, weatherization, and other factors.

The amount of air conditioning for commercial spaces is directly proportional to the total thermal load, which is the sum of both the internal and external load. An HVAC professional can help you measure your thermal load, which is a good way to determine the proper size of your AC.

Rent Commercial HVAC Units From Thompson Power Systems

Rent Commercial HVAC Units From Thompson Power Systems

At Thompson Power Systems, we rent out high-quality commercial heating and cooling equipment to help businesses across all industries keep their spaces cool in the summer heat. Whatever your organization’s cooling needs, we’ve got the right unit for you.

Unsure of your AC tonnage per square foot? Our expert team will help you figure out how many tons of AC you need to keep your space cool and comfortable without exceeding your power requirements. This way, you won’t have to do any guessing.

Find your nearest Thompson Power Systems location or contact us online to get started.

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