Every central heating and cooling system has an air filter, but finding it isn’t always straightforward. In most HVAC setups, the filter is located in one of three places: behind a return air grille, inside the air handler, or in a separate filter rack near the air handler. Your air handler is always indoors — typically in a basement, attic, or utility closet.
Keeping your air filter clean is one of the simplest ways to lower energy bills and maintain good indoor air quality (IAQ). A clogged filter forces your system to work harder, increasing wear and tear and leading to higher utility costs. Regularly checking and replacing your filter — usually every one to three months — can extend the life of your HVAC system and improve the air you breathe.
Where To Find Your HVAC Unit and Air Filter
Step 1: Locate Your Air Handler
Your air handler (the indoor part of your HVAC system) is a large metal box. Depending on your home’s layout, you’ll find it in one of these locations:
- Attached garage
- Basement (most common)
- Attic
- Utility room or closet
- Crawl space
Step 2: Find Your Air Filter
Air filters are typically located in one of these places:
- Inside or near the air handler
- Horizontal units (side return duct): Filter slots are on the intake side of the blower.
- Vertical units: Filters are placed in the base or duct track on the return side, either above or below the unit, depending on airflow direction (up-flow or counter-flow).
- Behind return air grilles
- Homes with multiple returns may have a filter behind each grille.
- Some systems have filters hidden behind ceiling or wall grilles.
Buy filters in bulk and when they go on sale to save money and stock up before each major demand season. Ensure the marked airflow direction aligns with the system airflow when installing. Add a task of “change filter” to your seasonal home maintenance routines.
Neglecting your central air filters causes problems. As they fill with particles, they restrict airflow, straining components and reducing efficiency. With less airflow, the system works harder to cool or heat sufficiently. Energy bills may rise. Dirty filters also allow more allergens and contaminants into the ductwork and air.
Replacing a dirty, clogged filter with a clean one reduces workload and maintains indoor air quality. Select a filter the manufacturer recommends to avoid restricting airflow too much. If dirty filters have been left in place for prolonged periods, there’s a good chance your indoor air could benefit from professional duct cleaning services.
HVAC Filter Types
Your HVAC system relies on air filters to trap dust, allergens, and pollutants, improving indoor air quality and system performance. Choosing the right filter depends on your home’s needs and your HVAC system’s capabilities.
Here are the most common types of HVAC filters:
Inexpensive fiberglass or polyester filters offer minimal filtration and only capture particles bigger than 10 microns.
Made of cotton, polyester, or blends, folded pleats trap more particles while maintaining airflow by expanding surface area.
Media filters with a static charge coating capture smaller particles, down to 3-5 microns, offering good value.
True HEPA filters remove 99.97% of particles down to 0.3 microns like dust mites but restrict airflow the most.
Carbon treated to absorb odors and gases like VOCs works well with a particle filter.
Detect when to replace and can auto-adjust fan speeds when dirty filters restrict airflow.
During your next HVAC tune-up, ask your technician about the best air filter for your home’s needs. While higher-rated filters improve air quality, they can also reduce airflow, which may strain your system. Always check with your HVAC manufacturer to ensure your system can handle upgraded filtration.
Proper installation is just as important — filters should fit snugly with no gaps to prevent unfiltered air from bypassing the system. Before buying replacements, double-check the size to ensure a perfect fit.
HVAC Filter Sizes
Air filters for homes and apartments come in various sizes, but the most common are:
- 12 x 12 in
- 16 x 16 in
- 16 x 20 in
- 16 x 25 in
- 20 x 20 in
- 20 x 25 in
How To Find the Right Size:
- Thickness varies from 1 to 5 inches, and some air handlers accept multiple thicknesses. For example, some systems can accommodate both 1-inch and 4-inch filters by adjusting a spacer.
- Measure your current filter’s length and width to determine the correct size.
Understanding MERV Ratings
Filters are rated by MERV (Minimum Efficiency Reporting Value), which measures effectiveness at capturing airborne particles between 0.3 and 10 microns.
You may also see FPR or MPR ratings instead of MERV:
| Rating System | Value Range | Rating Description |
| MERV | 1–16 | Minimum Efficiency Reporting Value |
| FPR | 1–10 | Filter Performance Rating |
| MPR | 1–2,000 | Micro-Particle Performance Rating |
HVAC Filter Pricing
The cost of HVAC filters varies based on size, material, and filtration level. Here’s what you can expect to pay for standard sizes:
- Basic Fiberglass: $6–$25 (low-cost, minimal filtration)
- Pleated: $10–$40 (better filtration, traps pollen and dust)
- Electrostatic: $15–$50 (captures smaller particles, reusable options available)
- True HEPA: $50–$120+ (high-efficiency, removes fine particles but may restrict airflow)
- Activated Carbon: $30–$65 (absorbs odors and chemicals)
These factors affect price:
- Size and thickness: Larger and thicker filters are more expensive.
- Filter quality and MERV rating: Higher-rated filters cost more but improve air quality.
- Brand: Well-known brands often charge a premium.
Are Washable Filters Worth It?
Some companies offer permanent electrostatic filters that last for years. While they reduce waste and long-term costs, they can restrict airflow more than disposable filters. If you choose a washable filter, clean it regularly to maintain performance and let it dry completely before reinstalling to prevent mold growth.
The Cost of Not Replacing Your Filter
Replacing air filters monthly (or as recommended) is a small expense compared to the benefits:
- Better HVAC performance: Dirty filters force your system to work harder.
- Longer system lifespan: Reduces wear and tear on critical components.
- Improved air quality: Captures dust, allergens, and pollutants.
Write the installation date on each new filter for an easy reminder.
You can often save buying in bulk when on sale or via auto-delivery subscriptions if timed right to avoid gaps between expired filters. Proper timing optimizes efficiency and air quality.
Is Changing Your HVAC Filter Really Important?
Yes, and it’s one of the easiest ways to keep your heating and cooling system running smoothly. A clean filter allows proper airflow, reduces strain on the system, and keeps energy costs in check. When the filter is clogged, your HVAC unit has to work harder, leading to higher bills and potential breakdowns.
Beyond efficiency, regularly changing your filter improves indoor air quality by trapping dust, allergens, and pollutants. It also helps prevent costly issues like clogged ductwork or system failure. Following a replacement schedule based on your home’s climate and usage ensures your system runs efficiently year-round.
While it may seem like a small task, swapping out your filter makes a big difference. Making it part of your seasonal maintenance routine protects your HVAC system, lowers energy use, and keeps your home comfortable.
FAQs About Changing HVAC Filters
For moderate use, replace your HVAC filter every one to three months. During times of lower use, like spring and fall, you can stretch that to every two to three months. However, in peak seasons — summer and winter — your system works harder, so it’s best to swap out the filter every month to maintain efficiency.
Always check the manufacturer’s recommendations for your specific filter type, as some high-efficiency filters may last longer. Keeping up with regular changes ensures better airflow, lower energy costs, and a healthier home environment.
When a filter gets too dirty, airflow is restricted, forcing your HVAC system to work harder to maintain the temperature. This extra strain leads to higher energy bills, increased wear and tear, and a greater risk of system failure. A clogged filter also allows more dust, allergens, and pollutants to circulate, lowering indoor air quality.
Regular replacement keeps your system running efficiently, extends its lifespan, and helps maintain cleaner, healthier air in your home.
Washable electrostatic filters can be vacuumed and rinsed, but they must be completely dry before reinstalling to prevent mold and mildew. Disposable filters, on the other hand, should never be cleaned and reused — once they’re clogged, they lose effectiveness and restrict airflow.
Always follow the manufacturer’s guidelines and replace filters as recommended to keep your system running efficiently.
You can find HVAC filters at hardware stores, home improvement centers, warehouse clubs, HVAC supply shops, and online retailers. Make sure to check the filter’s size and MERV rating to ensure it’s compatible with your system before purchasing.
The easiest way to find the right size is to check your HVAC owner’s manual for the recommended dimensions and MERV rating. If that’s not available, measure the length, width, and thickness of your current filter in inches. You can also take a photo of the old filter’s label to ensure you get the correct replacement when shopping.
