Purchasing a new central air conditioning system can get to be pretty costly, so making sure that you choose the right one for your home is essential in order to avoid spending more money than necessary.
Determining what size system you need is dependent on a variety of factors involving the airflow throughout your home. This includes many factors such as:
- The region you live in
- The number of windows there are
- The type and amount of insulation
- The type and amount of lighting within your home
- How your ducting is set up
- The type of ducting that is being used
- The number of people in your home
- And more!
A/C units are measured in “tons”. However, this does not refer to the unit’s weight. The tonnage of your system actually refers to the unit’s ability to cool. Air conditioners are available in half-ton increments. One “ton” has the ability to cool 12,000 BTUs (British Thermal Units) every hour.
A BTU is a unit of measurement that refers to the amount of energy required to heat or cool a pound of water by one degree Fahrenheit. This means that each hour, a one-ton system will cool 12,000 pounds of water by one degree, or anywhere from 300 to 800 square feet depending on the influence of the above factors.
Does This Mean a Larger System Is Better?
In simple terms—no. A system that is not the right size for your home will end up costing you more money in the long run. Here’s why:
- A system that is too large for your home will end up working more – It will cool quickly to the set temperature and then shut itself off. It is much easier for heat to enter your home this way since the air is not being circulated throughout the entire system. The temperature will rise again quickly, causing the system to kick back on and go through the same constant cycle over and over again.
- A system that is too small for your home will end up working nonstop – Your air conditioning system will never be able to quite catch up to the cooling requirements of your home. Air conditioners are meant to work gradually over time, so attempting to meet the set temperature, your system will run constantly without ever being able to maintain a comfortable environment.
In both scenarios, your air conditioning unit is working harder than a right-sized system would. This translates to more energy being used, which will be reflected in your monthly energy bills.
How Do I Know What Size Air Conditioner Is Best?
There are a few different ways to evaluate which size air conditioning system you need. The following are some tools that can help:
Equation by Square Footage
There is a formula which allows you to plug in the square footage of your home that yields the size that is recommended for your home. Here is what the formula looks like: ((Sq. Ft. x 25)/12,000) – 0.5.
So, for example, if your home is 2,000 square feet, this is how you would calculate the size system you need:
- 2,000 multiplied by 25 = 50,000
- 50,000 divided by 12,000 ≅ 4.167
- 4.167 minus 0.5 = 3.667
Because air conditioning systems are only available by the half-ton, do you round up or down? It is always recommended to round up when necessary so there is no doubt that your system will be able to handle the workload, even in extreme temperatures. Therefore, a 4-ton system seems to be the appropriate size for a 2,000 square foot home.
Air Conditioning Calculator
There are a few websites that will help you determine the right size system for your home as well. Depending on the site you use, these calculators take into account other factors regarding the airflow within your home, such as the number of windows, amount and type of insulation, and more. Here is an example.
This method of determining what size unit you will need for your home is the most accurate. Manual-J software uses a calculation based on either the home as a whole, or to be more precise, each room is evaluated individually.
- Whole-House Calculation: This type of Manual-J accounts for the entirety of your house—all of the factors that play into the overall airflow of your home are evaluated in a general sense.
- Room-by-Room Calculation: This is a more precise evaluation because of the fact that not every room in your home is the same—some have more windows than others, some receive more sunlight than others, and so on. This allows you to set up the system, including insulation and ductwork, to fit each room specifically.
This software is available for purchase, but can be complicated to use if you’ve never performed this type of evaluation. Unless you are a professional or have used the software before, it is highly recommended to call for a technician to come out and perform the Manual-J calculation for you. Some utility companies will provide this calculation for free.
Another important aspect to consider when purchasing a new central air conditioning system is who is going to be installing the unit for you. Pro HVAC Service partners with a nationwide network of HVAC contractors that are ready to compete for your service.
Get a Free Estimate on a New Air Conditioning System in Minutes!
A new central air system is a purchase that will stick with you for many years, so ensuring that you have the right size for your home is crucial in avoiding unnecessary long-term costs in the years to come.
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