There’s quite a bit that goes into choosing a new air conditioning unit. Picking out the right efficiency is important, as is choosing a brand known for quality and longevity. Another important choice you will need to make involves choosing the right size unit to properly cool your home. Here, you will learn more about tonnage, what it means, and how to decide how much you need.

Tonnage and BTUs – What Does it All Mean?

The term tonnage is a unit of measurement used to describe the cooling capacity of a central air conditioner unit, whether for a home or an industrial building. To put it into perspective, tonnage refers to the amount of heat it would take to melt 2,000 pounds (a ton) of ice over the course of 24 hours. Though it may seem a bit broad, it actually does a great job of defining cooling capacity.

For each ton, the air conditioner can cool 12,000 BTUs an hour. A BTU, then, is the amount of energy that’s needed to heat or cool a pound of water by a single degree Fahrenheit, which means that a one-ton air conditioner will cool 12,000 pounds of water by a single degree every hour, or a two-ton air conditioner can cool 24,000 pounds of water by a single degree each hour.

Common Sizes for Central Air Conditioners

Many homeowners mistakenly believe that bigger is better when it comes to central air conditioners, but this is not the case. In fact, despite the wide range of home sizes across the United States, most of these homes have air conditioners between 1.5 and 5 tons in size, with half-ton increments in between. Units that are more than 5 tons are typically considered commercial, and it’s recommended that you install multiple units rather than a single unit that is larger than five tons for the best possible performance.

It’s important that you really take the time to figure out the best size for your needs. An AC that is too big will cycle on and off quickly, which negates the unit’s energy efficiency and drives up your cooling bills, even though it will keep your home cool. One that is too small will run constantly, and this also drives up your cooling bills. The goal, then, is to choose a unit that is just the right size so you get the best balance between efficiency and comfort.

Calculating the Right Size

The only way to obtain the correct equipment sizing for any house or building is to run an ASHRAE (American Society of Heating Refrigeration and Air Conditioning Engineers) Manual-J Heat Load Calculation.  Many contractors have software to help with this calculation but it is also based on Bin Weather data by region because the same size house in Phoenix needs a larger AC unit than the same size house in Chicago.

It’s important to choose the right tonnage for your air conditioner for two main reasons. First, an improperly sized air conditioner could have a significant impact on your overall comfort, which can be frustrating. Second, failing to choose the right size essentially negates the energy-efficient design, leading to increased energy bills despite a brand-new air conditioner unit.