Heating & Cooling

Can You Run a Heat Pump Without an Air Filter?

Replace Filter

We’ve all been there. You removed your air filter from your heat pump and set out to the store to buy a new one only to find out it wasn’t in stock. Now what? 

You may be wondering can you run your heat pump with no air filter? You can run your heat pump with no air filter for a short period of time; maybe 1 or 2 days. Otherwise, you should always have an air filter installed and replaced every 30 to 90 days depending on the air filter type. The air filter collects dust and other contaminants from the air to keep your heat pump system running properly and is important to good indoor air quality.

Let’s look at how air filters work and why they are so important to the overall longevity of your heat pump system and your home’s indoor air quality.

What happens if your heat pump runs with no air filter

Dirty Evaporator Coil

Dirty Coil

With no air filter present, the air intake draws dirt, dust, pet dander, and other contaminants into the evaporator coil. This debris collects on the coil restricting airflow and contaminating the entire system. This can lead to a multitude of problems including sudden failure of the compressor or blower motor.

Problems with ductwork

If you run your system with no air filter dirt, debris, and other contaminants like mold spores travel throughout the ductwork. As moisture builds up in the ductwork mold spores can spread and began to circulate throughout the home releasing micro toxins into the air supply.

Condensate drain blockage

With no air filter present, dust dirt and debris get sucked into the intake and collects on the evaporator coil. Is condensation forms on the evaporator coil this dust and debris gets trapped in water droplets and travels through the condensate discharge pipe. This can collect and clog the drainpipe preventing it from draining properly.

How do air filters work?

Air filters are a necessary component to keep your heat pump system running smoothly. If you do not use an air filter or failed to change your air filter on a routine basis your heat pump system will experience problems. Air filters are present to serve two primary functions in your heat pump. These are: 

  1. They keep the evaporator coil and blower motor of the heat pump system clean and running smoothly. 
  2. They remove contaminants from the air keeping your indoor air quality to a high standard.

How air filters keep your heat pump clean

Your air filter helps to prevent dirt, dust and other debris from collecting onto the evaporator coil inside the air handler. When the evaporator coil becomes dirty other parts of the heat pump system have to work harder.

This puts stress on things like your blower motor and compressor. If the airflow is restricted bad enough the system can overheat and shut down. If you run the system long enough this way you can do long-term permanent damage which could cause premature replacement

How your air filter also protects your health

Air filters also protect your health by ensuring that the home has good indoor air quality. They were very in degrees of quality in air filters. Some air filters only filter out large particles of dust while other air filters can filter out dirt, pet dander and several varieties of mold spores.

People who are prone to respiratory infections, sinus problems, and other respiratory-related illnesses should be very mindful of the Air filter in their home.

If you have no air filter in your home or if the air filter is very dirty this dust and contaminants get re-circulated throughout your home on a daily basis. This creates very poor air quality in the home which can affect your health.

Do heat pumps have air filters

Yes, your heat pump does have an air filter. Some heat pump systems have multiple air filters. 

Air filters are typically located in the following areas:

  1. The return air duct. The return air duct is a square or rectangular louvered door that is typically located on a wall or ceiling in the center part of the house.
  2. Multi-zone systems. Multi-zone systems typically have two or three return air ducts as part of one heat pump system. These zones are typically controlled by their own thermostat and have their own return air duct near the thermostat. 
  3. Air handler cabinet. Some systems have air filters at the bottom of the air handler cabinet where air enters into the evaporator coil. This is commonly found in manufactured homes, apartments or in condos. 

Is it better to use a dirty air filter or no air filter at all?

If you have to choose between using a dirty air filter or no air filter at all, I would choose to use the dirty air filter with some cleaning. If you need to replace a dirty air filter and cannot purchase one at this time, you can try to clean the filter to get a few days of use until the store gets some back in stock or you can order some from an online supplier. 

You can sometimes clean a dirty air filter by using a vacuum to remove large loose debris from the air filter surface. Do not attempt to wash a disposable air filter. Keep in mind this will not completely clean your air filter and should not stand in place of installing a replacement air filter. 

If you find it hard to constantly find replacement air filters at your local store you may want to consider investing in a washable air filter or try buying your filters in bulk.

Can a dirty air filter cause my heat pump to stop working?

If the air filter in the house is too dirty it will restrict airflow into the heat pump which in turn will restrict airflow out to the supply vents. This puts a tremendous amount of strain on the heat pump system and can lead to overheating, and even premature failure.

Depending on the type of air filter you have, you should replace your air filter every 30 to 90 days. One of the things I’ve done is to set a reminder in my phone that goes off every 90 days notifying me it’s time to change my air filter. I have two reminders set; one is set a week prior notifying me to purchase new air filters and the second reminder for the actual replacement.

If you have a filter size that is somewhat odd and difficult to locate in stores, consider buying your filters in bulk online.

How to Replace Your Heat Pumps Air Filter

Air Filter Lg

Changing your air filter is an easy DIY job. Let’s go over the steps on how you can replace your air filter in your home.

How to change your air filter inside a return register

Step 1: Make sure your thermostat is set to off before you begin to replace your air filter.

Step 2: Unlatch the air return grill to open the return air duct. Depending on how your system is set up this door may lift up or down if positioned on a wall. Returns located on the ceiling will always open downward.

Step 3: Remove the dirty air filter. The air filter will be resting inside the return. Using a damp cloth wipe off any excess dust From the return grill

Step 4: Set the new air filter in place. Be sure that the airflow arrow is pointing in towards the return air duct.

Step 5: Close the grill door and latch it in place.

Step 6: Turn your heat pump system back on at the thermostat.

How to replace an air filter inside the air handler cabinet


If you do not have an air return vent, you’ll need to replace your air filter located at the air handler cabinet. These directions are typical for most manufacturers, however, you should consult your manufacturer’s user manual for specific details.

Step 1: Turn off the power to the air handler at the breaker or the service disconnect. 

Step 2: Most models have a filter door located on the side of the air handler or at the bottom of the air handler depending on how yours is configured. In most newer model systems, you should not need to remove the entire cover panel to change the filter. However, this may be required in older systems. Again you should check with your manufacturer’s user manual. If you do not have a user manual you can likely find one online. Simply do a Google search with the phrase “‘manufacturer’s name’ and ‘model number’ user manual” to obtain one. 

Step 3: Slide out the old air filter. The air filter inside the air handler may be disposable or permanent. If the filter is disposable the size will be printed on the side of the filter. Permanent filters will be labeled as such with directions on how to clean the air filter.

Step 4: Install the new air filter. Slide the replacement filter in place. Ensure that the airflow arrows are pointing in towards the air handler.

Step 5: Reinstall the filter door or cover panels. Be sure the door is secured in place.

Step 6: Turn the power back on to the air handler at the breaker or service disconnect.

I hope this info has helped you to better understand the importance of air filters and keeping them changed on a routine basis. This is an easy maintenance item that can help your heat pump last for many years to come.


Hubert Miles | Licensed Home Inspector, CMI, CPI

Hubert Miles is a licensed home inspector (RBI# 2556) with more than two decades of experience in inspection and construction. Since 2008, he has been serving South Carolina through his company, Patriot Home Inspections LLC. As a Certified Master Inspector, Hubert is dedicated to providing his expertise in home inspections, repairs, maintenance, and DIY projects.