If you’re a homeowner considering purchasing a new air conditioning system, you’ll have plenty of options. However, no matter what brand or model of central air conditioner you choose, there’s one thing that matters above all else. It’s that you choose a system that’s the correct size for your home. Failure to do so can have some serious consequences. For example, if you select a system that’s too small, it won’t be capable of cooling your home. And if you choose one that’s too big, its efficiency will suffer, costing you unnecessary operating costs. To avoid that, it’s a good idea to understand the factors that go into deciding on what size air conditioner your home needs. Here’s everything you need to know to make this essential decision.
British Thermal Units and Cooling Capacity
If you’ve ever purchased a window air conditioner, you’re probably familiar with the term BTU or British Thermal Unit. Put simply, BTUs tell you how much heat you can expect a given air conditioner to remove from a room within one hour. So, the larger the BTU rating on a given air conditioner, the more powerful it is.
To use BTUs as a way to choose the right size air conditioner, however, you’d also need to know how many BTUs it takes to cool one square foot of your home. Generally speaking, it takes 20 BTUs to cool one square foot of indoor space. Therefore, if you’re looking at a 5,000 BTU air conditioner, you can expect it to cool about 250 square feet of space in your home.
But when you’re talking about central air conditioning systems, you won’t be looking at BTUs. Instead, you’ll notice that those systems get measured in tons. The reason for that is simple. It’s that air conditioners big enough to cool an entire home would have impossibly large BTU ratings. So, the tons measurement serves as a shorthand to simplify things.
A one-ton AC system will provide the equivalent of 12,000 BTUs of cooling capacity. Using the math from earlier, you can tell that a one-ton AC can cool approximately 600 square feet. So, if your home has a total of 2,000 square feet you need to cool, you’d need an AC with a 40,000 BTU capacity. That would mean you’d require a 3.33-ton central air conditioning system. You should know, though, that central AC system sizes increase in half-ton intervals, so what you’d really be looking for is a 3.5-ton system.
The thing is, though, that not all indoor space is the same. Every home has its own specific cooling needs that you’ll need to consider before making a purchase decision. So, you’ll still have to do a bit more work before you can accurately determine what size AC system your home requires.
Factors That Affect AC Sizing
Although the equation above should give you a rough idea of what size AC system your 2,000-square-foot home needs, you shouldn’t rush right out to buy a system based on this information. Raw square footage is only a single part of the equation. That’s because what’s in the space inside your home matters, too.
For example, the space inside your home’s kitchen contains a variety of heat-producing appliances. You’ll have to account for these additional heat sources if you want your air conditioner to handle the extra heat load. In most cases, you’ll need an additional 4,000 BTUs for each kitchen in your home. And that’s just the beginning. There are a variety of other things that might call for some extra cooling power, including:
- High ceilings
- Western-facing windows
- Having multiple people occupying your home simultaneously
- Inadequate insulation in your home’s walls and attic
- An absence of window coverings
On the other hand, some things might allow you to get away with a smaller air conditioner. For example, if your home enjoys ample shade from nearby trees, you won’t need as much cooling power as you may think. Or, if your home’s exceptionally energy efficient, it might keep enough heat out during the summer to warrant a smaller AC unit.
How HVAC Contractors Determine Proper AC Sizing
As you can tell, the average homeowner has much to consider besides their house’s interior space when sizing an AC to keep their house comfortable during high summer temperatures. The variables in the decision make it a difficult chore, even for professional HVAC technicians. However, the pros have something that most homeowners don’t—a working understanding of the Manual-J load calculation.
It’s a system devised by the Air Conditioning Contractors of America (ACCA) that helps HVAC contractors to account for all of the heat load variables that affect a home. The Manual-J load calculation assigns BTU values for common household features and accounts for the total size of the house and its insulation performance.
As an example, a simple Manual-J calculation might include the following:
- Total square footage times the ceiling height
- Number of people in the home times 100 BTUs
- Number of windows in the home times 1,000 BTUs
- Number of exterior doors times 1,000 BTUs
Adding the values above would provide a baseline calculation for the home’s heat load. Then, the HVAC contractor would add additional BTUs to account for kitchens, insulation performance, and other heat variables within the home. The result would be a much more precise estimate of how much cooling capacity the home requires.
If you plug in the details of your 2,000-square-foot home into the calculation above, there’s a good chance you’ll end up with a smaller number than you got from the 20 BTUs per square foot recommendation from earlier in this article. That’s because the Manual-J calculation isn’t designed to be a simple one-size-fits-all standard. It’s designed to give HVAC contractors a way to get the decision right, according to the specifics of your home. There are fewer assumptions involved, and the results reflect that.
Trust the HVAC Experts
At this point, it should be fairly obvious that choosing the right size air conditioning system for your home isn’t always straightforward. The good news is that you can contact the experts at Sano Heating & Air Conditioning for help. When you call on us, one of our experienced HVAC technicians will evaluate your home to help you choose the perfect air conditioning system for your needs. We can eliminate all of the stress involved in your purchase decision, so you can focus on what’s important—making your home comfortable for you and your family.
We have been serving the residents of Anaheim, CA and the surrounding areas since 2018. We repair, maintain and install heating and cooling systems. In addition, we provide indoor air quality, ductwork, and new construction services.
To avoid ending up with the wrong size air conditioner for your home, contact Sano Heating & Air Conditioning today, and we’ll make sure you get precisely the cooling system your home needs.