How Often Should I Change My A/C Filter?
Home air filters are one of those things most of us only think about when there’s a noticeable degradation in our home’s air quality. Maybe it’s the poor quality of air that comes with pollen season or a nearby wildfire that reminds us: it’s time to check our filters. When we do, it’s usually not a pretty sight. Black or dusty filters can result from neglecting our heating and air conditioning systems until something is wrong. In some cases, it’s the high energy bills that get our attention, bringing the worst surprise of all — unexpected expenses at a time when energy costs are already on the rise.
So, you may be asking, how often should I change my AC filter? Fact is, replacing your filter at regularly scheduled intervals is recommended. Doing so can not only improve indoor air quality, but also helps keep your HVAC unit working smoothly in between filter changes.
Maintaining a regular MERV (short for Minimum Efficiency Reporting Value) filter changing schedule is especially critical to keep your HVAC system running properly and to avoid issues such as pressure drops/restricted air flow. How often you need to change your AC filter can vary depending on the type of filter you are using. In some cases, low quality fiberglass air filters will need to be replaced every month, while higher quality pleated air filters, can be replaced every three months depending on usage and other factors. We’ll discuss why in the sections below.
More resources for the following questions:
MERV vs. HEPA: What’s the difference?
How Often Should MERV 13 Filters Be Changed?
One of the most common questions we get at Carrier is, “how often should MERV 13 filters be changed?” First, let’s start with a definition of MERV 13 filters. Based on the standard created by the American Society of Heating, Refrigerating and Air-Conditioning Engineers (ASHRAE), the MERV rating system helps consumers select an air filter that suits their needs.
Working on a scale of 1-16, lower-numbered filters help trap large particles, while those on the upper end also filter out small, invisible particles. For instance, a MERV 1 filter may work well for removing large fibers from the air, but not do much for smaller particles. For that, we recommend a higher number filter. Note: higher MERV ratings are not always the better choice, as higher efficiency filtration can overwork HVAC systems, so a balancing act is needed for optimal effectiveness. When in doubt, consult with your HVAC unit’s owner’s manual or a local Carrier representative to determine which MERV rating is right for your home.
Sitting toward the upper end of residential air conditioner filters, a MERV 13 filter traps up to 90 percent of particles sized 3.0 to 10.0 microns and up to 50 percent of those from 0.3 to 1.0 microns.1 That means a MERV 13 filter will capture many particles including pollen, dust mite debris, mold spores, large dust particles, odor, bacteria, most smoke, and most pet dander that flow through the filter.
So, when should you replace your air filters? Changing MERV 13 filters every 30 days to 90 days is ideal, depending on use and other factors. While some larger 4” pleated filters can technically last up to six months between changings, the truth is that it depends on a variety of factors. If your home is in an area with high humidity, experiences wildfire activity, has smokers, pets or people with chronic allergies and asthma. In any case, the simplest approach is to regularly inspect your air filters for any signs of wear, including dark deposits, pet hair and visible signs of other household irritants.
How Often Should MERV 10 Filters Be Changed?
A MERV 10 filter is slightly less effective than a MERV 13 filter, trapping impurities between 1.0 and 10.0 microns in size (an effective trap rate of a rate of up to 80 percent for those particles between 3.0 and 10.0 microns and up to 50 percent for particles sized 1.0 to 3.0 microns; these filters are not sufficiently effective for the smallest particles sized 0.3 to 1.0 microns).1
Although not quite as effective as MERV 13 furnace filters, MERV 10 filters are still an excellent choice for those looking to trap pollen, dust mite debris, mold spores, large dust particles, bacteria, most smoke, and most pet dander that flow through the filter. It’s also a good option for those with less powerful air conditioning systems, as a MERV 10 filter will impede airflow less, imposing less strain to the heating and cooling system while still trapping certain impurities in the air.
As with MERV 13 filters, it is often recommended changing MERV 10 filters every 30 days to 90 days.
How Often Should You Change MERV 8 Filters?
Finally, we answer the question, “how often should you change MERV 8 filters?” One of the most commonly purchased filter types is the MERV 8 filter. These pleated filters work to trap up to 70% percent of particles sized 3.0 to 10 microns and up to 20% of particles sized 1.0 to 3.0 microns (again, these filters are not sufficiently effective for the smallest particles sized 0.3 to 1.0 microns).1 MERV 8 filters capture pollen, dust mite debris, mold spores, large dust particles, and most pet dander that flow through the filter. If your HVAC system is on the older side or is not very powerful, this is an excellent choice because it allows the furnace or air conditioning unit to function with higher capacity while still trapping many of the irritants that flow through the filter.
Similar to the previous MERV filters, it is often recommended to replace MERV 8 filters every 90 days.