Changing your AC's air filter is crucial during poor air quality—here's how to do it right

If your home has central AC, changing its air filter is a cheap, simple maintenance project that has a huge impact on your comfort, health, and your system's efficiency. Yet, many homeowners don’t even realize they have an air filter, let alone that it needs to be changed. What happens then? A bunch of stuff, actually, and none of it is good.

What is an air filter?

All central air systems have a filter that air passes through before circulating throughout the home. The filter protects your cooling equipment from dust and debris, which helps keep it running at maximum efficiency. Filters also capture airborne pollutants such as pollen and dander from the conditioned air before it reaches living spaces in the home.

When you don’t change your air filter, your central air unit has to work harder, reducing efficiency and putting added strain on its components. That means spending more on energy bills and repairs. Not changing the filter also means the air in your home isn't as clean as it could be.

How often do air filters need to be changed?

That answer depends on a few factors, including the type of filter you use, how often you run the AC, and how dirty your indoor air is. For the average home, our experts recommend replacing the filter every few months. If the central AC is running full-tilt all summer and indoor air quality is poor, say from pet dander in the home, you might need to change the filter once a month during peak cooling season. Otherwise, a single filter change when you first turn on the central AC for the season may be enough to get you through summer.

How do you change an air filter?

Every home and AC system is unique, but the process typically follows these steps:

1. Locate the filter placement. Central AC filters usually sit behind the main intake vent; there’s often a dedicated slot for the filter built into the air handler. Before removing the old filter, look for an arrow on its cardboard frame indicating the airflow direction. Make a note of the filter's direction and size, which should also be clearly printed on the frame.
2. Get a replacement. Air filters are sold at home centers, hardware stores, and online. They typically cost around $20 per filter, though you’ll pay more for filters with a high capture rate (meaning they’ll snag more pollutants as air passes through them).
3. Install the new filter. Double-check the direction the filter should be installed, then slide it into place. Keep a record of the date so that you’ll know when it’s time to change the filter again.

You might want to consider upgrading your air filter. Most forced-air systems have a flimsy 1-inch cardboard filter that’s good, but not great, at cleaning the air. A 4-inch pleated filter has much more surface area, so it captures many more particulates. Just know that to make this upgrade, you’ll need to bring in a professional to modify the rack the filter sits in.