How Often Should You Change Your HVAC Air Filter?
Most homeowners should change their HVAC air filter every 30 to 90 days. The right schedule depends on the type of filter you use, whether you have pets, if anyone in your home has allergies, and how often your system runs. During Michigan's cooling season, when your AC runs daily, checking it monthly is the safest bet.
That 90-day rule you've probably heard is a reasonable baseline, but it doesn't account for what's actually happening in your home. A household with two dogs and a family member with seasonal allergies will clog a filter much faster than a single person in a small condo. The good news is that checking your filter takes less than a minute, and staying on schedule is one of the easiest ways to protect your system and your air quality.
Filter Change Schedule by Type
Not all filters are built the same. Thicker filters have more surface area to trap particles, which means they last longer before they need replacing. Here's a general guide:
| Filter Type | Thickness | Typical Replacement Interval |
|---|---|---|
| Fiberglass (flat panel) | 1 inch | Every 30 days |
| Pleated (standard) | 1 inch | Every 60 to 90 days |
| Pleated (high-efficiency) | 1 inch | Every 60 to 90 days |
| Deep pleated (media filter) | 4 to 5 inches | Every 6 to 12 months (some dusty homes can be 90 days) |
What Makes You Need to Change It More Often
Pets
If you have a dog or cat, plan on checking your filter every 30 days and replacing it every 60 days at most. Pet hair and dander build up fast, especially during shedding season (spring and fall in Michigan). Homes with multiple pets or heavy-shedding breeds should expect to replace the filter monthly.
Allergies or Respiratory Conditions
If anyone in your household deals with seasonal allergies, asthma, or other respiratory issues, more frequent filter changes make a noticeable difference. A filter that's even partially clogged can no longer trap pollen, dust mites, and other fine particles effectively, which means those allergens end up circulating through your home instead.
This is especially relevant in Michigan, where allergy season runs from late March through the first hard freeze. Tree pollen peaks in April and May, grass pollen takes over in early summer, and ragweed dominates from late August into fall. During those peak months, a monthly filter change is worth the few dollars it costs.
Heavy System Use
Your filter gets dirty faster when your system runs more. In the middle of a Michigan summer, when your AC may run 16 to 20 hours a day, a filter that would normally last 90 days can be spent in 30 to 45. The same applies in winter when your furnace is running constantly. If your system is working hard, your filter is working hard too.
Home Size and Foot Traffic
Larger homes circulate higher volumes of air, which means the filter captures more particles in the same amount of time. Homes with more people, more activity, and more doors opening and closing throughout the day will also see filters dirty up faster. If you have kids running in and out all summer, that filter is taking on extra dust and pollen every time the door swings open.
Nearby Construction or Renovation
If there's construction happening in your neighborhood or inside your home, the amount of dust and debris in the air increases dramatically. During any renovation project, check your filter every two weeks and replace it as needed. A single drywall sanding session can load a filter faster than a month of normal use.
Warning Signs Your Filter Needs Changing Now
Even if you're on a schedule, it helps to know the signs that your filter is already overdue:
Visible dirt buildup. Pull the filter out and hold it up to the light. If you can't see light passing through the mesh, it's time to replace it.
Reduced airflow from your vents. If some rooms feel stuffy or the air coming from your registers feels weaker than usual, a clogged filter is the first thing to check.
Higher energy bills. A dirty filter forces your system to work harder to push air through, which uses more energy. Replacing a clogged filter can reduce your energy consumption significantly.
More dust on surfaces. If you're noticing dust settling on furniture and shelves faster than normal, your filter may be too full to trap new particles. They're bypassing the filter and circulating through your home instead.
Increased allergy symptoms indoors. More sneezing, congestion, or itchy eyes while you're inside can point to a filter that's no longer doing its job.
What Happens When You Don't Change Your Filter
Skipping filter changes might seem like a small thing, but the consequences add up. A clogged filter restricts the airflow your system needs to heat and cool your home. When airflow drops, several problems can follow.
Your evaporator coil can freeze. Without enough warm air passing over it, the coil gets too cold and ice forms on the surface. Once that happens, your AC stops cooling entirely. (If that sounds familiar, we covered this in detail in our post on why your AC might be running but not cooling.)
Your blower motor works harder. The motor has to push air through a wall of dust and debris, which increases wear and can shorten its lifespan. Blower motor repairs are not cheap.
Your energy bills climb. The system uses more electricity to deliver the same amount of heating or cooling. That efficiency loss from a dirty filter adds up over months of heavy use.
Your indoor air quality suffers. Once a filter is saturated, it can't trap new contaminants. Dust, pollen, mold spores, and pet dander circulate freely through your ductwork and into every room. If air quality is a concern in your home, our indoor air quality services can help you find a solution that goes beyond the filter.
How to Check Your Filter
If you've never checked your filter before, here's what to do:
Turn off your HVAC system.
Locate the filter. It's usually behind a return air grille (the large vent in a hallway, utility room, or near your furnace) or in a slot on the air handler itself.
Slide the filter out and hold it up to the light.
If the mesh is visibly gray or caked with debris and no light passes through, replace it.
When installing a new filter, check the arrow on the frame. It should point toward the furnace or air handler, in the direction of airflow.
Write the date on the filter frame with a marker so you know when you last changed it.
If you're not sure where your filter is, what size to buy, or what MERV rating is right for your system, our technicians can show you during a routine maintenance visit.
A Quick Note on MERV Ratings
MERV stands for Minimum Efficiency Reporting Value, and it tells you how well a filter traps small particles on a scale from 1 to 16 for residential use. Higher is not always better. A filter with a MERV rating that's too high for your system can restrict airflow just like a dirty filter would.
For most homes, a MERV 8 to 11 filter strikes the right balance between filtration and airflow. If you have allergy concerns, a MERV 11 or 13 may be worth considering, but check with your HVAC technician first to make sure your system can handle the increased resistance. Using the wrong filter can create the same problems you're trying to prevent.
Don't Want to Think About It? We've Got You Covered.
Keeping up with filter changes is simple, but life gets busy. If you'd rather not add one more thing to your to-do list, Lakeside'sMembership Club takes it off your plate. Members get annual tune-ups for both heating and cooling that include a full filter check, coil cleaning, electrical inspection, and system performance test. You also get priority scheduling and discounts on repairs if something does come up.
It's the easiest way to make sure your system stays healthy year-round without having to remember when you last swapped the filter.
Frequently Asked Questions
How often should I change my HVAC filter if I have pets?
If you have one pet, check the filter monthly and replace it every 60 days. With multiple pets or heavy-shedding breeds, plan on monthly replacement. Pet hair and dander accumulate quickly and can clog a standard filter well before the 90-day mark.
Can a dirty air filter cause my AC to stop cooling?
Yes. A clogged filter restricts airflow to the evaporator coil, which can cause the coil to freeze over. Once that happens, your system blows room-temperature air instead of cold air. Replacing the filter is the first thing to check when your AC isn't cooling properly.
What happens if I use a filter with too high a MERV rating?
A filter with a MERV rating higher than your system is designed to handle can restrict airflow and force your equipment to work harder. This can lead to reduced efficiency, higher energy bills, and even frozen evaporator coils. For most residential systems, MERV 8 to 11 is the recommended range.
Is it worth upgrading to a thicker media filter?
In many cases, yes. A 4 to 5 inch media filter has significantly more surface area than a standard 1-inch filter, which means it lasts longer and provides better filtration with less airflow resistance. However, your system needs to be set up to accommodate the thicker housing. Ask your HVAC technician whether a media filter is compatible with your equipment.
How do I know what size filter to buy?
The easiest way is to check the size printed on the frame of your current filter. It will list the dimensions (for example, 16x25x1). If there's no label, measure the length, width, and depth of the filter slot. Using the wrong size leaves gaps that allow unfiltered air to bypass the filter entirely.
