What Are Air Conditioning BTU’s?

AC System in Charlotte, North Carolina

If you’ve started to think about getting yourself a new air conditioner, it’s likely that you’ve noticed that the term “BTU” comes up very frequently. It’s practically impossible to find a unit that isn’t described in terms of BTUs. What exactly are BTUs, and why are they so important?

British Thermal Units

BTUs are British thermal units. The term was originated in Britain, which shouldn’t be a huge surprise given the name, and it’s a unit that measures heat. Heat is a form of energy; depending on the situation, heat can either be added or removed from a space. BTUs are used to describe a variety of appliances and other components in the industry. When we talk about a kitchen stove, for example, BTUs are used to show how hot it can get. In reference to air conditioners, BTUs are used to describe how much heat they can remove. To be more specific, it’s how much heat that it can remove in an hour.

The use of BTUs helps us to standardize the cooling power of air conditioners. Without a term like this, it would be difficult to assess how effective a particular AC could be and hard to determine which AC would be best for a specific house.

One BTU is the amount of heat it takes to raise the temperature of one pound of water by one degree. It’s a very small amount of heat. When we use BTUs in reference to air conditioners that can cool rooms or even entire homes, the number of BTUs is usually in the tens of thousands.

There is a rule of thumb that’s often used in the HVAC industry, and it’s that one square foot of space can be cooled by a unit with 20 BTUs. It’s a completely linear relationship, so 100 square feet can be cooled by 2,000 BTUs, and 1,000 square feet can be cooled by 20,000 BTUs. Using this ratio and the square footage of the space that you’d like to cool, you can get an estimate of how many BTUs would be necessary.

What Do Tons Have to Do With BTUs?

Hopefully, everything has made sense up until this point. You still might have a question, though, if you’ve been shopping for an air conditioner for your home. Many people wonder why the term “tons” is used to describe air conditioners.

When you shop for whole-home air conditioners, you see the term “BTU” being used, but more often than not, you see that there are two-ton air conditioners, 2.5-ton ACs, three-ton ACs, and so on. You might be able to find a five-ton AC in the market, but you really won’t find anything larger than that size that’s been designed for a residential home.

When we say “ton,” we don’t mean 2,000 pounds, which is its common definition. Instead, we’re making a reference back to the time when ice was used to cool certain buildings. In some areas, people used to haul in huge blocks of ice to keep things cool. As the ice absorbed heat from the air and brought the temperature down, it would melt. Scientists of the time figured out that it took about 288,000 BTUs to melt a ton of ice in a day. (At this point, we do mean 2,000 pounds of ice.) Doing the math, we see that it takes about 12,000 BTUs per hour to melt a ton of ice.

While we don’t use ice anymore to cool our homes, we still use the math that they came up with. A one-ton air conditioner has about 12,000 BTUs. A two-ton AC has about 24,000 BTUs, and so on.

The rule of thumb that was mentioned previously still applies. A home with 2,100 square feet of living space would require an air conditioner with 42,000 BTUs. Since one ton in AC terminology equals 12,000 BTUs, this home would need a 3.5-ton unit. Some homes, especially those that have different floors or different wings, have been split into different zones. In this case, one would have to figure out how many square feet are in each zone before deciding on a unit for that particular zone.

Important Factors

Presenting the information in the way that we did makes it simple to figure out how many BTUs are necessary to cool a home. The reality, though, is that it’s not always that simple. There are many factors that can influence how cool a home can be and how well it can keep the cool air inside.

Those factors include:

  • Layout
  • Number of people in home
  • Height of ceilings
  • Insulation, windows, and shade

Also, the number of appliances can play a role. For instance, if you’re looking for a unit that will cool your kitchen, you should increase the number of BTUs by a slight amount because of all the heat that can be generated by the fridge, stove, and other appliances.

When you have a professional come out to take a look at your home, every factor can be carefully assessed. It can be a smart move to have a trained technician give you a hand with your air conditioner selection. After all, there are several different brands and types of units, and it can be hard to figure out which one would be best.

The Ideal Size

People often talk about the size of an air conditioner. They’re not literally referring to its height and weight, but instead, they’re referring to how many BTUs it has. It’s critical to get something that works for your place.

If you get something too small, your unit might not get your home to your desired temperature. Plus, it will be continually working hard, and this can lead to components breaking down prematurely.

The opposite scenario would be if you get a unit that has too many BTUs. This seems like it would be a good idea, but if you get an AC that’s much too big, it’s not ideal. It will quickly cool your home, after which it would turn off. When your air goes above your set temperature, it will turn on again and then turn off soon after that. This process is called short-cycling, and it can lead to excess wear and tear on the air conditioner’s components.

Your Source of Assistance

At Integrity Heating & Cooling, we’re proud to serve our local community. We can take care of your air conditioner installation if you’re located in the Charlotte area. Our business has been around for 35 years, and we’ve earned a reputation for being professional and dependable. We have a 100% satisfaction guarantee, so customers can feel free to bring any of their concerns to our attention. We hold ourselves to high standards and aim to keep everyone happy with the quality of our work. We offer AC and heating repair, installation, and maintenance, and we have experience with generators as well. In addition, we offer financing on approved credit. Call us today to set up an appointment or if you have any questions.