What Size AC Unit do I need?

Before you get a home AC installation, it’s important to consider the air conditioner’s size. Otherwise, you could end up spending more money on AC repairs and replacement parts than you need to. 

When purchasing a new AC, you don’t want to get an oversized or undersized unit. An overly large unit will short cycle because it cools too rapidly. Meanwhile, an undersized unit will end up staying on too long. Both situations can lead to extra wear and tear. 

To ensure your family’s comfort, take time to calculate the BTUs and tons of air conditioning that you need when you get an air conditioner replacement. To learn more about performing this calculation, read on.

How Do I Know What AC Size I Need? 

If you are uncertain about which air conditioner replacement to get, you can always ask one of our HVAC professionals for help. In general, the air conditioner size is calculated by first figuring out the number of BTUs you need. Then, you must divide this figure to get the tons of air conditioning capacity. 

How to Calculate Tons of Air Conditioning 

To calculate the tons of air conditioning your home needs, start by getting out a tape measure and calculator. Then, work your way through the following steps.

1. Measure the Square Footage 

First, you need to measure the square footage of your home. You should only include the areas that will be air-conditioned. 

Start by measuring the length and width of each room. Multiply the length by the width to get the area. Then, add the area of each room together to get the total square footage of your home.

If you don’t want to calculate the home’s square footage by hand, you may be able to find it on your closing papers or in the home’s architectural drawings. Often, counties list the square footage of residences on property tax forms and websites. If you are planning on air conditioning your entire home, you can easily copy the square footage used by your county. 

2. Calculate the BTUs 

Next, you need to calculate the British Thermal Units (BTUs). This is the measurement for the amount of heat needed to increase the temperature of one pound of water by a degree. Typically, you’ll find that each type of air conditioner has a different range of BTUs. While window units may only have a capacity of 5,000 to 10,000 BTUs, central air conditioners are often rated for 20,000 to 50,000 BTUs.

There is an in-depth calculation you can do to get an exact estimate of the BTUs you need. However, there is a simple calculation that provides an easy, close approximation of the BTUs you’ll require.

Multiply the Square Footage by 20

To figure out the BTUs you need right away, just multiply the square footage you want to cool by 20. While this figure doesn’t reflect every factor involved, it will be fairly close to the BTUs you’ll need.

Think About Other Factors 

There are other factors that impact the number of BTUs your space needs. Cooling preferences, the number of occupants, and your home’s insulation can impact the BTUs you require. Additionally, ENERGY STAR recommends making the following adjustments. 

• Increase the AC’s capacity by 10% for extremely sunny spaces.
• Decrease the AC’s capacity by 10% for heavily shaded areas.
• For areas normally occupied by more than two people, raise the capacity by 600 BTUs per extra person.

3. Divide the BTUs by 12,000 

While knowing the BTUs is helpful, you’ll normally hear people discuss an air conditioner’s cooling capacity in tons. The AC tonnage is the amount of heat your air conditioner can remove per hour. If you have a larger space, you’ll need more tonnage. 

The basic way to calculate the tonnage you need is by first figuring out the BTUs. Then, divide this figure by 12. The resulting figure is the tonnage you will require. 

Tonnage is normally a figure between 0.5 and 5. Here are a few examples of the tonnage needed for different home sizes. 

600-square-foot home: 1 ton of cooling capacity

900-square-foot home: 1.5 tons of cooling capacity

1,200-square-foot home: 2 tons of cooling capacity

1,500-square-foot home: 2.5 tons of cooling capacity

1,800-square-foot home: 3 tons of cooling capacity

2,100-square-foot home: 3.5 tons of cooling capacity

2,400-square-foot home: 4 tons of cooling capacity

After calculating the tons, you can adjust the final estimate to accommodate your home’s insulation and ventilation. Two-story homes are also known for holding heat in the upper level, so you may need to get a higher tonnage. 

Why Is Air Conditioner Size Important? 

Calculating the air conditioner size is incredibly important. If the air conditioner is the wrong size, it may cause added wear and tear. In the long run, you’ll end up spending more on air conditioner repair costs and AC maintenance. Plus, finding the appropriate air conditioner size ensures better efficiency, longevity, and comfort.  

Efficiency: When the air conditioner is the correct size, it can reach the desired temperature without having to use as much electricity. As a result, you can spend less on energy costs. 

Longevity: Oversized and undersized ACs aren’t functioning at the right capacity, which leads to extra wear. As a result, these units don’t last nearly as long as they are supposed to.

Comfort: If an air conditioner is the wrong size, it may struggle to keep your space at an even, consistent temperature. Getting the right air conditioner size ensures your family’s comfort. 

Find Out the Right AC Size for Your Home

Figuring out the right size for your home AC installation doesn’t have to be difficult. You can always talk to one of our HVAC professionals about the type of AC you need. To learn more about your air conditioner replacement options, reach out to Alpha Heating & Air’s HVAC professionals today.