What size of air conditioner does your home need?

Does your home need a new air conditioner? If you’ve done any research online, you’ve probably already been bombarded with acronyms like “BTU” and “SEER.” There are different sizes of the same air conditioner. How do you know which is right for your home? How do you calculate what size of air conditioner you need?

Just as with furnaces, the size of your air conditioner matters. In this article, we’ll walk you through air conditioner sizing, why your home needs the right size of system, and how size and efficiency are related.

How do I calculate what size AC unit I need?

It’s a common question we get from many homeowners: “How do I calculate what size of air conditioner I need?” First, let’s take a step back and discuss what “size” means. We’re not referring to the physical size of the air conditioner, but how much cooling output it can produce. An air conditioner’s ability to cool air is measured in British Thermal Units, or BTUs. The higher the BTUs, the more air the system can cool every hour.

In its simplest form, air conditioner size comes down to the square footage of your home: the larger your home, the larger the system needed to cool it. But, just buying an air conditioner based off square footage alone can lead to significant problems. While square footage is the primary determinant of your air conditioner’s size, it’s far from the only one. The exact size of air conditioner you’ll need also depends on factors such as the number of rooms, the number of stories, the number of windows, and the amount of attic insulation your home has.

As you can see, the answer can get relatively complex, and is often individualized to your specific home. It’s why most HVAC companies offer free in-home estimates on new systems: it’s far more precise to send an installation expert out to the home to take these measurements than to make educated guesses based on basic details about the home.

A Wagner technician installs a new air conditioner here in Albuquerque, New Mexico

How do I know if my AC unit is big enough?

After your HVAC installation expert takes measurements, they’ll provide you with a recommendation for a new system. Your new air conditioner will be the right size for your home.

But, there are sometimes cases where homeowners end up with an air conditioner that’s too small for their home. This most often occurs when homeowners shop independently for a new system, or work with an inexperienced HVAC company or contractor. This problem can also arise if the homeowner adds windows, doors, or new rooms to their home post-installation.

An air conditioner that’s too small for the home just won’t have enough power to keep up with your home’s cooling demands. It’ll run constantly, just trying to maintain the status quo in your home. You’ll feel the heat in the summer as the system struggles to cool your house down. And you’ll definitely see the impact on your upcoming utility bills.

As we’ll discuss below, going bigger isn’t always better, either. The answer to “what size air conditioner do I need?” is more about finding the right fit than leaning one way or the other.

Is it better to get a bigger air conditioner?

Most people think this, but this is actually not the case. When it comes to air conditioners (and furnaces), more isn’t always a good thing. Contrary to popular belief, a larger air conditioner will not cool your home more effectively or efficiently. In fact, the opposite can end up being the case.

When your thermostat detects rising temperatures inside your home, the air conditioner kicks on. It then runs at a preset speed, gradually cooling the air in your home and maintaining that desired temperature. Eventually, the air conditioner will switch off when the temperature in your home is stable.

If your air conditioner is too large for your home, you could run into a problem called “short-cycling.” When a system short-cycles, it’s running through the process described above in quick succession. The system, being too large, cools your home far too quickly and shuts itself off. There’s no “cruise control” speed that the system can run at without wildly overshooting the target. As a result, the system is constantly starting and stopping. This wastes energy, stresses the system, and puts your home’s comfort on a rollercoaster between hot and cold.

Don’t overshoot the average AC unit size recommended for your home. It’s better to have an air conditioner that’s just right for your property than one that’s larger.

What SEER rating do I need?

There are plenty of acronyms in the HVAC world, so it’s easy for homeowners to get BTUs—used to measure the AC’s output—and SEER mixed up. SEER, or “Seasonal Energy-Efficiency Ratio,” is a measurement of efficiency. The higher the SEER rating, the more energy-efficient the air conditioner is. Air conditioners that feature variable-speed systems and efficiency-based designs are often able to run far more efficiently than a standard unit. SEER allows you to compare systems on this front.

There’s nothing inherently more or less efficient about smaller or larger AC systems. Think about it this way: your air conditioner’s size is fixed, since it’s based on what your home needs. But, SEER is something you can control and decide on: higher SEER systems often will cost more upfront to install, but can pay for themselves in energy savings over the course of several years.

What else do I need to know?

The right installation matters. It’s easy for an inexperienced or unlicensed contractor to cause a decade’s worth of headaches for a homeowner in a single afternoon. If the air conditioner is not installed correctly, you’re probably going to run into both performance and efficiency issues. When buying a new air conditioner—or, really, any HVAC system—be sure to work with an established and trusted HVAC company that has a proven track record of successful installation projects.

Wagner is that company here in Albuquerque and Santa Fe. Our team has been helping local homeowners stay comfortable since 1928. Our technicians are experienced installation experts. During our free in-home estimate, we’ll take precise measurements of your home and match you to the perfect new air conditioner or heat pump. We’ll also advise you on which systems will save you the most money through their energy-saving features.

Ready to upgrade to a new air conditioner? Let’s find the right one for your home. Click the button below to contact our team and set up your free in-home estimate.