When it comes time to replace or install a new air conditioner, it is essential that the unit you choose is appropriately sized for your home. If the AC is either undersized or oversized, it can make it nearly impossible to properly keep your home cooled. It can also greatly increase your energy costs and lead to more wear and tear on the unit and a shortened lifespan. Professional HVAC technicians take a variety of different factors into account when sizing an AC unit, and here is a quick overview of how it is done.
Calculating Square Footage
The first step is to calculate the total square footage of the area that you will be cooling. This means measuring every room that has supply vents and is connected to your central HVAC system. To calculate square footage, simply measure the length and width of each room and then multiply these numbers together. Finally, add up all of the rooms together to determine the total square footage of the home.
BTUs of Cooling Needed Per Square Foot
The general rule of thumb is that you need 20 BTUs (British thermal units) of cooling output for each square foot of space. This means that for a 1,500-square-foot home, you would need an air conditioner that produced a minimum of 30,000 BTUs.
However, it is important to note that this rule is based on a home with standard 8-foot ceilings. If your home has high ceilings in some or all rooms, you will also need to take this into account since the high ceilings increase the total volume of air that needs to be cooled. If your home has 10-foot ceilings, you’ll generally need something closer to 35 BTUs per square foot instead of the standard 20. Still, this is a fairly rough estimate, which is why it is always best to enlist the help of a professional HVAC technician to ensure your new unit is properly sized.
BTUs and AC Tonnage
Once you know approximately how many BTUs you need, you can use this to determine AC tonnage. Central air conditioners are measured in tons, and they range anywhere from 1.5 up to 5 tons. One ton is equal to 12,000 BTUs. This means for that 1,500-square-foot home, you would need at least a 2.5-ton AC unit (30,000 / 12,000 = 2.5).
However, let’s say that your house is 1,650 square feet. Based on this calculation, you would need a minimum of 2.75 tons. The problem is that AC units are only available in half-ton increments, which would leave you with a choice between a 2.5- or 3-ton unit. In this situation, you are always best to go with the unit that is slightly larger instead of opting for one that is slightly undersized.
Other Factors to Take Into Account
When calculating AC sizes, a professional HVAC technician will look at much more than just the overall size of your home as there are numerous other factors that can affect how many BTUs you need. For instance, 20 BTUs per square foot is definitely fine for New York and other northern states, but it is probably not sufficient for people living in a much hotter climate. The same is also true for people who live in extremely humid climates.
How much sun or shade the building receives is also an important consideration. If the building is mostly shaded throughout the day, you can generally reduce the total BTUs by around 10%. The opposite is also true if the building receives lots of direct sunlight during the day. In this case, you would need to add an additional 10%.
The number of people living in the building is another factor. Typically, you should add around 400 additional BTUs per person. Other important factors include the number, size and location of windows in the home as well as how well insulated the building is.
Hudson Valley Cooling and Heating Specialists
If you’re in the market for a new air conditioner, the expert HVAC technicians at WK Mechanical, Inc. can perform a full evaluation of your home to ensure you get exactly the size of AC you need. We carry a range of energy-efficient cooling and heating equipment from top brands like Lennox, and we also repair and service equipment from any manufacturer. We provide honest, up-front pricing on all services, and we also offer financing for new equipment purchases on approved credit. Our company is located in Middletown, and we have been providing outstanding HVAC services to residential and commercial customers throughout the Hudson Valley area since 1945. To learn more about your AC replacement or installation options, give us a call today.
