Determining the right size AC unit for your home begins with questions. What direction do your windows face? Do you have high ceilings? How much of your home is exposed to direct sunlight all day? Everything that makes your space special also affects your AC’s required tonnage.
What Is Tonnage?
British Thermal Units (BTUs) are the standard unit of measurement used to grade an AC unit’s cooling ability. More BTUs equal more cooling power.
A ton is equivalent to 12,000 BTU, so an AC unit’s tonnage refers to its power, not its weight.
In theory, it takes roughly 20 BTUs to cool one square foot of space. However, this rule of thumb doesn’t account for each home’s variables, and an accurate assessment requires a tailored calculation.
Figuring Out Your Home’s AC Requirements
Square footage is only the beginning. It’s always a good idea to ask for an expert’s evaluation, but the following considerations all impact your home’s AC performance and required tonnage.
What AC Unit Did You Use Previously?
Are you replacing your AC with the same type of system? If so, judge the previous unit’s performance. If it didn’t keep your home cool during the hottest part of the year, you have a baseline tonnage the next unit needs to clear.
However, even if your last AC unit kept your home cool, careful analysis may bring long-term savings. Oversized units drain energy, and you might find a smaller unit that does the job with lower utility costs.
Where Do You Live?
Your region’s climate is key. An AC unit can handle hundreds more square feet in Augusta, Maine than in Clearwater, Florida. An experienced One Hour technician can help you with area-specific estimates to avoid frustration from generalized, online guesstimates.
How Old Is Your Home?
A home built five years ago will probably retain cold air better than a historic home built 100 years ago. Even a couple of decades make a difference. Home design elements like insulation continuously improve, and the parts of your house hiding behind the walls impact your air conditioning’s efficiency.
What Is Your Home’s Layout?
A sprawling house with an interesting design may require a more powerful AC unit than a simple, box-shaped home, even if the two buildings have the same square footage. The broader a house’s roof, the more direct sunlight it absorbs. The same goes for exterior walls.
A home with a wide footprint and a packaged air conditioning system also requires longer ducts for cold air to reach every room. Air may warm up during that journey, especially if the ductwork is near the roof or in an open crawlspace.
Does Your Home Have Unique Features?
Many of the house features you love impact your AC’s performance. Windows are a great example. The more you have, the more natural light you enjoy, but your climate control system may have to work harder, especially if you have old or south-facing windows. The same is true for high ceilings.
Other features, like shade from nearby buildings and trees, can have the opposite effect and reduce the load on your AC.
Request a Manual J Calculation
For the most accurate assessment possible, schedule a Manual J calculation. This formal evaluation comes from the ACCA (Air Conditioning Contractors of America), and the organization regularly updates the official Manual J guidelines to reflect changes in home design and legislation.
Your utility provider may provide free energy and Manual J calculations, or you can discuss your options with a One Hour technician. You don’t have to make a guess. We’ll help you find the perfect cooling solution for your oasis.