How Often Do I Really Need to Change My HVAC Filter?

By | July 18, 2018

Replacing the filter in your air conditioning and/or heating system is one of the best and easiest things you can do to keep it working effectively and efficiently. The filter keeps particles (some visible and some not) from getting into the fan and motor. A dirty filter will reduce airflow which causes the system to run less efficiently and can lead to equipment damage, both of which cost you money.

Filter life and performance

If you get your unit serviced twice a year, you may think you’re all set on filter maintenance but don’t assume twice a year is often enough to change your filter. Many factors can affect the longevity of your system’s filter.

Does someone in your home have asthma or allergies? Do you have young children? Both of these situations call for superior air quality so you may want to consider changing your filter as often as every month. Likewise, pets and their resulting dander may necessitate a more frequent replacement.

The rate at which you use your HVAC and the size of your home also determine when it’s time to change your filter. A large home and heavy use during the hottest or coldest months call for filter evaluation and possible replacement more often.

In addition to regular replacement, make sure that the filter slot on your indoor unit is in place and sealed well.  Filter slot covers are simple plastic covers that attach with magnets to cover and seal the opening where the filter is. Sealing this opening keeps out dust and particles, which are often heavier in the unconditioned basements and other spaces where heating and air conditioning systems are located.

How to tell if it’s time for a change

There’s no strict guideline but unless it’s a seldom used vacation or second home, follow the directions on the filter packaging at a minimum. Depending on the filter type, that may require a change every month! If you’re not sure of the status of your filter or feel like something is off in your airflow or quality, take it out and give it a look.

If your filter shows only a subtle layer of dirt under which the filter’s material is still visible, your filter is in working order. If you hold the air filter up to the light and can’t see light through it, it’s too dusty and needs to be changed.

If in doubt, it’s always best to err on the side of replacing your filter. Regular filter changes maximize airflow efficiency and increase indoor air quality, keeping your energy costs down and your breathing easy.

Filter type and ordering

Pleated filters have more surface area to capture dust particles than flat filters, but they are are more expensive than flat filters and can restrict air flow if your system wasn’t designed explicitly for them.  Ask your technician to check that your system is set properly for the filter you want to use regularly.

Even the most well intentioned homeowner can forget about changing the filter between service calls. Your HVAC service company may have an auto ordering program, or try a company like that automatically sends filters to you at the frequency you select.

And as always, reducing energy use is good for your bills, good for the planet and good for your filter. Check out these tips from ENERGY STAR® on how to heat and cool your home efficiently so you can extend that filter life and save money.