How Many Filters Does A Furnace Have? Need To Know

As a homeowner, it’s important to know the parts of your HVAC system and keep them maintained. One key component is the air filter in your furnace – but how many are there? 

How Many Filters Does A Furnace Have

Image: Different sizes of furnace filters

Normally one filter fits into the intake vent or an air handler. It depends on the unit’s make and size for the right size and type of filter. Certain homes may have more than one air filter, especially when they have more than one AC unit or a large duct system. Usually, one furnace filter needs changing every few months.

Did you know that not changing your furnace air filters often enough can reduce airflow and cause debris buildup on other HVAC components like fan motors? This can lead to costly repairs and reduced system efficiency in the long run. So, brush up on your furnace filters knowledge.

Furnace Filters: What You Need to Know

To help you understand furnace filters better, let me share some valuable insights with you. This section will discuss four essential subsections which include 

By following this guide, you will have all the information you need to select the right filter for your system, improve airflow, and keep your home free from dust and debris.

Different Types of Furnace Filters

Furnace Filters are important for clean, healthy air. Here are 4 types.

Types of Furnace FiltersDescriptionProsCons
1. Fiberglass FilterDisposable, spun fiberglass.Low cost, easy to find.Poor at trapping small particles, needs replacing often.
2. Pleated FilterPolyester/cotton folded into pleats. Better than fiberglass, cheaper than HEPA.Good filtering lasts longer than fiberglass.Blocks airflow, may damage the furnace’s fan motor if dense.
3. Electrostatic FilterTraps airborne contaminants with electrostatically charged fibers.High filtration efficiency, can be washed and reused.Expensive, electricity needed, doesn’t trap big allergens, needs regular cleaning.
4. HEPA Filter/High-Efficiency Particulate Air FilterTrap tiny microns of dust and pollutants.Excellent filtration, catches tiny particles, including allergens.High cost, may have maintenance difficulties, can damage the fan motor.

Choose one with a high MERV rating. Replace filters every 3 months for optimal air quality and to keep the HVAC system working well. Finding the right size is hard, but it’s essential.

What Size Furnace Filter Do I Need?

Knowing the right size furnace filter for your home is essential for the efficiency of your furnace and the quality of the air. Here is a list of the most common sizes and their benefits:

16x20x1Suitable for single-room furnaces
20x25x1A popular size for residential furnaces
14x25x1Fits wall-mounted or ceiling-mounted filters
20x30x1Great for larger homes with bigger heating systems

Remember to measure your filter slot before buying a new one. Also, a higher MERV (Minimum Efficiency Reporting Value) rating means better filtration, though it might reduce air flow and affect furnace performance.

How Often Should I Replace My Furnace Filter?

It’s key to switch out your furnace filter every 1-3 months. This depends on usage, filter type, and if you have pets, allergies, or smoke at home. Replacing the filter will extend the lifespan of your furnace, as well as lower energy costs.

Ignoring the filter could lead to very expensive repairs. Make sure you know when a new one is needed by setting reminders or marking on a calendar. For added convenience, stock up on several furnace filters at once. 

The Importance of Choosing the Right Furnace Filter

Choosing the right furnace filter is essential! Without proper filtration, your indoor air quality could be compromised. Six key reasons why choosing the right filter is so important:

  • Prevents pollutants from entering your home
  • Increases energy efficiency & saves money
  • Protects HVAC system from damage
  • Reduces dust & maintenance costs
  • Improves air quality
  • Can prolong furnace lifespan

Understand the MERV rating system to find the best filter for your specific needs. Consider electrostatic charge & other features. Specialized benefits like odor reduction & antimicrobial protection are available too. Don’t underestimate the importance of selecting the right filter – it affects your health & wallet. Make sure you’re using a quality filter that meets your lifestyle needs. Contact an expert if unsure. 

How Many Filters Does a Furnace Have?

To ensure your HVAC system functions efficiently, it’s important to know how many filters your furnace has, and where they are located. In order to keep the air flowing throughout your home without any issues, you need to understand the different types of filters in the system. These include the air intake vent filter, the air handler filter, the filter slot/filter compartment, and the return vents/return ducts. Each of these components has specific needs when it comes to filter size, depth, and airflow, so it’s important to locate them and choose the right filter for the job.

The Air Intake Vent Filter

An air intake vent filter, also known as a furnace filter, is essential for your HVAC system. It keeps dust and debris out of your heating system and stops them from entering your home. Here’s what you need to know:

  • The filters come in different sizes and ratings.
  • They should be replaced regularly, especially when they get clogged.
  • A dirty or clogged filter will reduce the efficiency of your heating system.
  • Most filters need to be replaced every three months.
  • Pet owners may need to change their filters more often due to pet hair.
  • If you have allergies, get a higher-quality filter to trap smaller particles like pollen, bacteria, and viruses.

Image: An air intake vent filter

Remember, the air intake vent filter affects the air quality in your home. So, regular change is important. Keep spares on hand, so you don’t need to urgently find them when it’s time to replace them.

The Air Handler Filter

Maintaining the air handler filter is a must! Here’s why:

  • It traps allergens, dust, and debris to keep the air inside your home clean.
  • Cleaning or replacing it can reduce energy bills and help your furnace last longer.
  • Maintenance frequency depends on usage, air quality, and type of filter.

It’s worth noting that some furnaces may have extra filters like pre-filters or post-filters. Keeping these clean can create a healthy indoor environment.

Did you know that dirty filters can reduce furnace efficiency by up to 15%? (Source: Energy Star)

The Filter Slot/Filter Compartment

A furnace filter slot is a compartment where you install an air filter to protect your heating and cooling system. The type and size of your furnace decide the number of filters you need. The following table shows the number of filters required based on your furnace type:

Furnace TypeNumber of Filters
Variable Speed1-2

In addition, your home’s location, size, number of occupants and allergies/respiratory problems also affect the number of filters. Get advice from an HVAC expert to choose the right filter.

The Return Vents/Return Ducts

  • Return vents and ducts are important for a furnace’s filtering system. They are usually in rooms away from the furnace and draw in air that has circulated in the house. This air then goes to the furnace where it is filtered.
  • Unobstructed vents and ducts are essential for efficient furnace operation and better performance. If they are blocked by furniture or other items, this can cause problems and reduce the furnace’s efficiency.

The number of filters in a furnace may vary – it depends on size and type, as well as airflow needs and filtration requirements.

Replacing Furnace Filters

To replace your furnace filter, follow these simple steps. 

  • Start with the intake vent filter; remove the old filter and replace it with the correct size. 
  • Next, move on to the air handler filter. Replace it with the appropriate size and type. 
  • Then, replace the return vent or return duct filters and finally, change the filter slot or filter compartment filter. 

Follow these steps and ensure that your furnace has clean air filters to keep your home’s HVAC system functioning optimally.

How to Replace the Air Intake Vent Filter

Curious about replacing your furnace’s air intake vent filter? It’s a vital job for improving air quality inside your home. Here’s how to do it in three simple steps:

  1. Locate the Filter: Check your furnace manual or look near the bottom of your furnace.
  2. Remove the Old: Open the cover and take out the old filter. Note any direction markings.
  3. Install the New: Put the new filter in its slot with the right direction markings. Close the cover properly.

For optimal performance and life, change your air intake vent filter every three months. If you have pets or family members with allergies, do it monthly. Maintaining a clean filter prevents dust, debris, and contaminants from entering your home. Don’t forget this important task – keep your family safe by changing your furnace filters frequently!

How to Replace the Air Handler Filter

Air handler filters are vital for good air quality. Here’s a guide on how to change them:

  1. Cut off power to the unit.
  2. Find the filter – usually near or inside the blower compartment.
  3. Open the compartment to access it.
  4. Take out the old filter, noting how it was placed.
  5. Insert a new, clean one and make sure it’s properly seated.
  6. Replace any covers and turn the power back on.

Replace the filter every few months for optimum performance. For better air quality, choose high-quality filters. Cleaning return vents/ducts is like giving your lungs a spa day – essential for long-term health.

How to Replace the Return Vents/Return Duct Filters

Want a proper furnace system? Change the return vents’ and duct filters’ regularly! Here’s how:

  1. Turn off power. Gently remove the old filter. Locate the filter compartment.
  2. Clean all surfaces near return vent grilles or ductwork. Vacuum or use a damp rag.
  3. Measure replacement filter size. Most common: 16×20, 20×25, 16×25.
  4. Insert new filter. Ensure snug fit and correct direction.
  5. Put back cover panels, clips, and screws. Turn on the furnace.

Check once a month. Depends on filter quality, pet/human shedding, etc.

How to Replace the Filter Slot/Filter Compartment Filter

Replacing furnace filters is an essential task for a functional HVAC system. Even though you don’t need to be an expert, it’s important to follow a few steps:

  1. Turn off your thermostat and make sure no air is coming through the vents.
  2. Find the filter access cover near the air handler unit.
  3. Slide off or unscrew the cover of the filter access panel.
  4. Gently pull out the old air filter from its slot.
  5. Follow the instructions on the new filter as specified by the manufacturer, taking note of the airflow direction indicated on each side.

When choosing filters, pick high-quality, compatible ones that fit your budget. Replace them every 3 months minimum, depending on the air quality in your house and other factors.


Maintaining a furnace air filter is key for efficient and healthy airflow in your house. Look for filters in return vents, filter slots, or air handlers of the HVAC system. The number of filters depends on the type and size of the unit. It’s essential to replace your furnace filter every 1-3 months. Depending on things like pets, allergies, and dust levels. Failing to do so could cause reduced airflow, higher energy bills, or costly repairs. There are multiple types of filters available for different parts of your HVAC system. Some homes may need many air filters for their central air system. When buying a replacement filter, check the dimensions. Filters come in various sizes and depths that may differ from standard dimensions. Investing in proper furnace care now will save you time, money, and stop you from missing out on healthy living spaces. Make sure to prioritize your family’s health by keeping clean air with a working filter!