For first-time air conditioner buyers, the process can be a bit overwhelming. If you’re in the market for a new AC unit, you’ve likely heard about different AC sizes and might have seen “BTU” a couple of times. But what does it all mean when it comes to choosing your AC?
What does AC size mean?
The size of your AC unit actually refers to its cooling capacity rather than its physical dimensions. This is measured in British Thermal Units (BTUs) based on the cooling needs of your home. Having a well-sized AC means your system will operate at maximum efficiency, lowering your operating costs and making your home as comfortable as possible.
Manual J Calculations
To calculate the size of your home’s ideal AC unit, we use a Manual J calculation. Some HVAC professionals can do this calculation as well as professional energy auditors. Manual J calculations consider many factors to ensure accuracy, including:
- House size in square feet
- Number of residents
- Type and number of windows
- Heat-generating appliances
- Sun exposure
As a rule of thumb to get you started on your AC unit search, you can calculate the BTU requirement of your new AC unit using only square footage by multiplying the square footage by 20 BTUs. There are also dozens of free BTU calculators available online. However, calculating AC size is a job best left to professionals to avoid the risk of improperly sizing your new system.
Bigger Isn’t Always Better
Bigger usually means better, but it’s important to understand that this isn’t true for air conditioners. It’s tempting to get a bigger AC using the logic that it will cool even better, but oversized AC units actually struggle with cooling spaces that are too small. This will lead to frequent cycling that wears down your AC much faster than it should, which will likely lead to early replacement.
The same goes for those who wish to save money by getting a smaller AC. It won’t be able to adequately cool the space, making the unit work harder for longer to meet your cooling needs. You’ll never be satisfied with its performance, and it can also lead to faster wear and tear on the unit.