How Often Should You Really Change Your Air Filter?

As an HVAC system operates, the air flows through an air filter which traps dust, dirt, hair, pollen, dander, and other small particulates. If the air filter is not regularly replaced, it can become clogged, leading to air quality issues and lower system efficiency.

Typically, an HVAC air filter should be changed about once every three months, but the frequency can vary depending on several key factors. Learn how often you should change your air filter.

Type of Air Filter

The specific type of air filter that is used in the HVAC system can impact the frequency with which the filter needs to be replaced.

• Flat filters are relatively inexpensive, but they also need to be replaced about once a month. Additionally, this type of filter tends to be less effective at blocking particulates than other filter options.
• Fiberglass filters have a similar price as flat filters and need to be replaced about once a month. These filters block large particles well, but fine particulates pass through into the home.
• Pleated filters are thicker and more effective than both flat and fiberglass filters, though they are also more expensive. Homeowners will only need to change these filters about once every four months.
• HEPA filters are the most effective option for the home. They can trap as much as 99.97 percent of contaminants and only need to be changes once a year, though they are also more expensive than other filter options.
• Washable filters do not need to be replaced regularly. Instead, you just need to remove, clean, and reinstall the existing filter about once a month.

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Home Size

Generally, smaller homes can get away with leaving the air filter in for longer than larger homes because there is a lot more air moving through the home and through the air filter in a larger space.

Air Quality

When homeowners or occupants smoke indoors or leave the windows and doors open for long periods of time, the air quality inside the house can drop. In this case, the air filter will fill up at a faster rate, quickly becoming clogged if it isn’t replaced. For those that suspect the home has poor indoor air quality, it’s a good idea to inspect the air filter at least once a month.

Pets

While not all pets impact the air quality inside the home, there are many that shed hair and fur as the move around the house. The excess hair and fur can then be pulled into the HVAC system, where it is trapped by the air filter. If the home has pets that shed, then the air filter should be replaced more frequently, depending on the number of pets and the amount of hair. Consider changing the filter about once every two months instead of every three months.

Season

Seasonal weather changes can affect the air quality inside the home. During the spring and fall months, the windows and doors are left open more frequently and the debris in the air, such as pollen and dust, can increase.

However, since the HVAC system isn’t running as much as it does in the winter or summer, the air filter doesn’t trap the particles. This means that while the air filter may not need to be changed as often in the spring or fall seasons, the air quality indoors is often worse than it is during the summer and winter seasons.

Occupancy

A full family household will naturally cause more dirt and debris to be carried into the home, so the air filter will need to be replaced more frequently, whereas a vacant vacation home won’t need the air filter changed as often. Similarly, if the home has small kids or elderly individuals, it may be better to replace the air filter more frequently to maintain high indoor air quality.

Signs You Need to Change Your Air Filter

Other than a regular maintenance schedule, you should also watch out for signs that the filter needs to be replaced. If the HVAC system seems to kick on more often or run for longer periods, then it may mean the air filter should be changed.

Similarly, unpleasant odors emanating from the furnace or HVAC system, as well as a large amount of dust present indoors can indicate that the old air filter should be replaced. When in doubt, you should visually inspect the air filter. Replace the filter if it’s visibly dirty or dusty.

Best Time of Year to Change Your Air Filter

HVAC air filters need to be changed about once every three months. This is a simple maintenance task that most DIYers can handle without a problem, so it can be done at any time of the year. However, if you don’t feel confident with this task, it’s often more cost-effective to have a pro replace the filter during the winter months, when there is a lower demand for HVAC services.