The main function of air conditioning systems is to control air temperature, but these systems work to improve indoor air quality too. While your AC is keeping you cool, it’s also removing dust and other airborne particles from the air in your home. It does this by passing air through a filter. To keep your HVAC system in good working order, maintenance is required. And that includes changing the air conditioner filter on a regular basis. Not sure how to change your AC filter? We’ve put together this guide to help you through the process.
How to Change Your AC Filter
Your air conditioner filter should be changed or cleaned at least every three months. You may need to change the AC filter more often if:
- You have pets
- Anyone in your home has allergies
- Dust levels are high for any reason
The filter may also need to be changed more often in summer.

1. Locate the Filter
Changing your air conditioner filter is a relatively simple job, but discovering where the filter is located can be a little tricky. There are several different places in an AC system where a filter might be installed, so you may have to check multiple locations before you find it.
- Return air duct: Return air ducts are the ducts that pull air from the house back into the AC duct network. Note that if you have a large or multistory home, you might have several return air ducts, which means there may be multiple filters too.
- Near the furnace blower: If your home AC and central heating use the same duct network, then the air filter might be located in or near the furnace blower system.
When to get help: If you have trouble finding your AC filter, call your HVAC service technician for advice. They can help you locate the filter, as well as offer advice on how to change it.
2. Choose the Right Replacement Filter
Choosing the replacement filter for your AC system is generally straightforward. The filter size is usually printed right on the filter itself, so it’s easy to pick out the right-sized replacement. If your current HVAC air filter doesn’t have this information or it’s hard to read for any reason, it may be tricky to figure out what you need.
When to get help: If you’re unable to determine what size filter you need, call your HVAC service technician for help. They can help you figure out what kind of replacement to purchase.
In addition, you should seek advice if you want to replace your existing filter with a high-efficiency filter. This includes HEPA filters or filters with a higher MERV rating. This is important because high-efficiency filters aren’t as easy to install as regular filters. If they’re not installed correctly, they can put strain on the AC system, making it less efficient and increasing the risk that parts become worn or break down.
Another reason it’s important to get professional help with special filter installation is that high-efficiency filters alter how air flows through the system. This may mean your AC system needs adjustments after installing a HEPA or other high-efficiency air filter. This is best done by a professional HVAC technician to ensure your system works safely and efficiently after installation.
3. Replace the HVAC Air Filter
Once you have the right replacement filter in hand, you’re ready to get the job done. In most cases, replacing your AC filter is an easy job, and you’ll be done in just a few minutes:
- Turn off the power. Turn the AC system off, then switch off power at the unit and the circuit breaker. It’s much easier and safer to replace a filter when the system is turned off. Aside from the potential hazard of live voltage, turning off the power also ensures dust and grime from the filter don’t get accidentally taken up into the system.
- Take out the old filter. It should slide right out of its slot. You may need to remove a few screws or fasteners and then slide the filter out.
- Check the filter. If it’s so severely clogged with dust and dirt that you can’t see any light coming through it, that’s a good indication that it’s overdue for attention. If this is the case, make sure to change it sooner next time.
- (Optional) Clean the filter. If you’re working with a reusable filter, the next step is to clean it. Check your user manual for instructions on how to clean the filter. If this isn’t possible, then it’s usually okay to clean the filter with a stiff brush or by vacuuming dust away. Some filters can also just be washed, rinsed, and left to air dry.
- Replace the filter. The final step is to either replace your reusable filter or insert a new disposable one. The filter should have an arrow on it that depicts the direction air needs to flow through the filter. This is generally away from the return air duct and towards the air handler unit. Once you’ve inserted the filter into its slot, the arrow should point towards the air handler.
When to get help: Provided you’re replacing the existing filter with a new one of the same kind, changing the filter is something homeowners can safely do themselves. But if at any stage you don’t feel confident about what you’re doing, you can always call your HVAC technician for help.
It’s best to call in a professional if you’re replacing your existing filter with a HEPA filter or other high-efficiency filter.
If you are elderly, disabled, or for any other reason unable to access the unit to replace the filter, a CW service professional can replace your filters when he comes out for his bi-annual maintenance visit. Just give him the filters, and he will be happy to install them for you!
Regular Filter Checks and Changes Are Crucial to AC Maintenance
Your HVAC system works hard to keep your home comfortable. To keep it in good shape, it’s important to perform regular maintenance tasks like changing the AC filter. A clogged filter makes the system less efficient and less effective, but by spending a few minutes taking care of this simple maintenance task every few months, you help keep your HVAC in good working order.