How Often Should I Change My Filters?

Most HVAC pros suggest replacing air filters every 3 months; it’s the most basic form of AC maintenance. Can you afford to wait longer than 90 days? This depends on a few factors, such as the type of filter, system usage, and your household. There are many reasons to consider changing your filters more frequently. We’ll examine reasons not to wait as long and how to know a filter has gone bad.

When to Change an HVAC Filter

Air filters don’t last forever. You don’t want to wait too many months past your filter’s life expectancy, or else repair issues and high energy bills can become problematic. Whether you replace your filter every month or 90 days depends on the following:

• Type of Filter: The type of filter is the most important factor in how often you change it. Fiberglass air filters generally don’t last more than 30 days. While more expensive, a pleated air filter can last as long as 90 days, depending on how much you use your HVAC system. Check with the air filter manufacturer for product replacement recommendations. 
• Size of Your Home: The larger your home, the more air circulates through your HVAC system, which means an air filter can get dirtier faster. In a smaller home, less air circulates, so the filter may last longer. However, smaller air filters may get dirtier just as fast as larger ones; depending on the filter, the replacement schedule may be the same.
• How Often You Use Your HVAC System: Running your heating or cooling system constantly will increase your AC maintenance needs. You may need a new filter every few weeks. But if you run the system sporadically or just part of the day, one filter can last for months. Some can last anywhere from a whole season to a full year.
• Number of People: Households with more people tend to generate more dust and dirt, which can shorten a filter’s lifespan. This is especially true if you have young children at home. In these environments, even thicker pleated filters should be replaced more often. If you have a small family, live alone, or are in your home part-time, fewer filter changes are necessary. 
• Pets: Pets that shed hair, release dander, and track in dirt and pollen can contribute to indoor air pollution, which ends up in air filters. You’ll need to change the filter at least every two months. Do so during the transition from winter to spring and summer to fall when cats and dogs shed the most.
• Allergies: If you have allergies, install a new air filter before the old one becomes clogged. It can help reduce bouts of coughing, sneezing, or runny nose. If you or anyone in your household has asthma or other respiratory conditions, consider changing the filter every 20 to 45 days to protect sensitive lungs.
• Outdoor Air Quality: Poor outdoor air quality can affect an HVAC filter. Smoke, dust, and debris can get into your home and clog it, which is common in big cities. Wildfire smoke can also shorten the time needed between filter replacements. Check the filter more often on smoky days or when outdoor air quality is poor.
• Season: How frequently you use your HVAC system depends on the season. Spring and fall tend to be milder, so the system is used less. The air filter won’t clog as fast unless you keep doors and windows open or run the fan constantly. However, filters trap more dirt and contaminants during the heating and cooling seasons (AC maintenance between times of peak demand ensures you have a clean filter for the season).

How to Know a Filter Needs Changing

Visually inspecting the filter is the only way to know if it’s good or needs to be replaced. We recommend checking it monthly (more often if you get a new pet or the outdoor air quality is poor). This way, you can replace a clogged filter in time and figure out how quickly it gets dirty. When inspecting a filter, hold it in front of a light source. The light should pass through; if not, replace the filter with a clean one.

Remember, there’s no strict guideline for how much dirt is acceptable. A filter with a thin layer of dirt may be fine if you can still see its material. If its surface is completely obscured by debris, replace the filter. A musty odor also means you need a new filter.

Other than seeing a dirty filter, other signs it may need changing include:

• Dust and debris on vents
• Dust on fan blades, cabinets, and other surfaces
• Your AC/heater sounds strained when starting
• The HVAC system runs for longer periods
• An indicator light reveals it’s time to change the filter

What If I Don’t Change the Filter?

The longer you wait, the more dust, dirt, and allergens will collect on the filter. Your HVAC system will work less effectively, reducing comfort, energy efficiency, and indoor air quality. A buildup of mold, fungal, and bacterial particles can damage the system or cause health issues in your household. 

Also, a thick coating of dirt can impede airflow, which increases wear and tear on your heating or cooling system. Dust can jam fan motors, valves, and other moving parts. The excess strain can lead to frequent repairs.  Over time, strained components can fail, causing others to break down, until you’re dealing with a major issue like compressor failure.

Does My HVAC System Need to Be Repaired? 

Over time, if you don’t change the filter as recommended or schedule routine AC maintenance, your HVAC system can be damaged. Replacing the filter won’t fix the problem at this point. Call an experienced contractor if you notice signs such as:

• Reduced Temperature Control: If your AC is blowing warm air or the furnace is not heating your home, there may be a problem with a thermostat, compressor, or other component. 
• Restricted Airflow: This can be caused by a clogged filter or ductwork blockage, but other mechanical issues can affect airflow too. 
• Loud Noises: If your HVAC system is louder than usual, it may have a mechanical issue caused by strain resulting from a dirty filter or a lack of maintenance.
• Frequent Cycling: Waiting too long to replace the filter can lead to AC problems that cause it to turn on and off too frequently. This means the system is working harder than it should.
• Higher Energy Bills: A dirty filter can cause your AC or heater to run less efficiently, causing your energy bills to spike. High bills can also mean your HVAC system needs to be repaired.

Contact Trio Heating & Air

We are a leading air conditioning service company in the The Greater San Francisco Bay Area area. Whether you need a new filter, a tune-up, or an AC repair, our licensed and trained technicians are committed to customer satisfaction and a job well done. Our team is prompt and ready to ensure your home stays comfortable. They can fix any issue with your HVAC system and provide annual AC maintenance to prevent breakdowns and improve efficiency. To request routine service or repairs, call (415) 223-1647 today.