How Often Should You Change Your Air Filter?
In the hustle of daily life, it’s easy to forget about the humble air filter quietly working inside your air conditioner or ducted HVAC system. But if you’ve ever noticed your allergies flaring up indoors or your cooling system struggling to keep up, your filter might be trying to tell you something.
So, how many days was that again? 30? 60? Or 100? The general consensus with “how often change air filters” is that you should be replacing them in your home every 3 months, or 90 days. But what happens if you let that time lapse a little bit? Before we talk about WHEN you should change your air filter, let’s begin with the WHY.
This guide is designed specifically for homeowners who want to keep their HVAC system running smoothly while improving indoor air quality and avoiding costly repairs. From key warning signs to the right replacement schedule and expert tips to avoid common filter mistakes, we’ve got you covered.
What Does an HVAC Air Filter Actually Do?
Your HVAC air filter acts as the frontline defense against airborne particles things like:
- Dust and dirt,
- Pollen and plant spores.
- Pet dander.
- Smoke particles.
- Mould spores.
- Bacteria and other microbes.
It’s not just about air quality either. A clogged or dirty filter can restrict airflow, forcing your system to work harder. That translates into higher energy bills and faster wear-and-tear on your unit.
So, How Often Should You Change Your Air Filter?
The short answer is: it depends on your home, your habits, your pets, the air quality in your area and whether you’re using your air conditioning daily or only when summer scorches the suburbs.
Let’s get to the core of the matter. Here are the general guidelines:
| Type of Home | Recommended Filter Change Frequency |
|---|---|
| Standard Aussie Home (no pets) | Every 3 months |
| With pets | Every 2 months |
| Allergy sufferers | Every 6–8 weeks |
| Smokers in the house | Monthly |
| Urban/high-pollution areas | Every 1–2 months |
| Holiday home | Every 6–12 months (when in use) |
Keep Your Air Clean
However, these are just starting points. If your unit’s been running constantly during a Melbourne heatwave or Sydney bushfire season, that 3-month guideline may shrink to 1 month.
So next time you think about how often change air filter, don’t rely on the calendar alone. Your system and your air will give you clues.
What Happens If You Don’t Change It?
Air filters might not look like much, but they’re your HVAC system’s first line of defence. They trap dust, pet hair, pollen, smoke, and even mould spores before these particles get circulated through your home. Many people ignore their filters for months (or even years).
But here’s what you’re risking by putting it off:
1. Shorter System Lifespan
Your HVAC system can overheat, break down early, or even blow a motor due to restricted airflow. Replacing a $20 filter is a lot cheaper than replacing a $5,000 system.
2. Poor Indoor Air Quality
Dirty filters let pollutants circulate indoors. For allergy sufferers, this can make your home feel worse than the outdoors.
3. Higher Running Costs
Your system works harder when airflow is blocked, increasing your electricity usage—especially during extreme Aussie summers.
4. Mould Growth
A clogged filter can trap moisture, allowing mould to grow inside your system—and that’s a health hazard.
5. Costly Repairs
Ignoring filter changes often leads to mechanical issues. You could end up needing coil cleaning, ductwork repairs or worse.
Avoid Costly AC Damage
The Warning Signs Your Air Filter Needs Changing
1. Your Aircon’s Struggling to Keep Up
If your HVAC system suddenly feels underpowered, a clogged air filter may be restricting airflow. The harder it works, the more energy it burns and the faster it wears out.
2. Dust Is Building Up Fast
Finding dust on surfaces even after cleaning? That’s a classic sign your filter’s no longer catching airborne particles.
3. You’re Sneezing Indoors
Worsening allergies or asthma symptoms while you’re at home often point to indoor air pollution usually from a blocked filter failing to trap allergens.
4. Higher Power Bills
Sudden spikes in energy bills can happen when your system works overtime to push air through a dirty filter.
5. Musty or Stale Smells
Old filters can harbour bacteria, mould spores, or trapped particles that cause unpleasant odours when your system turns on.
6. Pet Fur Around Vents
If you have a hairy pet, and his hair is making its way to your vents, your filter may be full (or too low-grade for your home’s needs).
7. The Filter Looks Grey or Black
If your filter looks discoloured, dusty, or covered in grime, it’s past due for a change.
So next time you wonder how often change air filter, check for these real-world clues, your home might be telling you it’s time.
Choosing the Right Air Filter for Your Homes
Not all filters are created equal and what works in the UK or US might not be best for Australian conditions.
Here’s a quick guide:
Flat Panel Filters (Disposable)
- Affordable, basic protection.
- Change every 1–2 months.
- Not ideal for allergy sufferers.
Pleated Filters
- Capture more particles.
- Better for homes with pets or allergies.
- Change every 2–3 months.
HEPA Filters
- Capture 99.97% of airborne particles.
- Great for asthma, babies, or medical conditions.
- Change every 2–4 months.
Washable Filters
- Eco-friendly and reusable.
- Must be cleaned monthly.
- Suits light-use homes or holiday homes.
If you’re buying a new filter, here’s what to keep in mind:
1. Size
Check your current filter or HVAC manual to get the right size. Too big or too small won’t cut it.
2. MERV Rating
In Australia, most residential filters use the MERV (Minimum Efficiency Reporting Value) scale.
- MERV 6–8: Good for general dust and lint.
- MERV 9–12: Better filtration for pet dander, pollen, and smoke.
- MERV 13+: Hospital-grade — may reduce airflow in standard home systems.
3. Reusable vs Disposable
Some Aussie homes use washable filters. These are eco-friendly but must be cleaned regularly. Disposable filters are easier but should be changed more often.
How to Change an Air Filter (Step-by-Step DIY)
Changing your air filter isn’t rocket science. In fact, it’s one of the simplest ways to keep your heating and cooling system running smoothly. Here’s how to do it yourself:
What You’ll Need
- A replacement air filter (right size and type).
- Screwdriver (if your cover is secured).
- A torch (if your system is in a dark cupboard or roof cavity).
Step-by-Step Instructions
1. Turn Off Your System
Always shut off the power to your system before opening it. This prevents dust from blowing into your home or your face.
Find the Filter Compartment
Depending on your setup, the air filter may be located:
- Behind a return air grille (usually on the ceiling or wall).
- Inside the indoor unit of a split system.
- In the ducted system’s indoor fan coil unit.
2. Remove the Old Filter
Slide the dirty filter out carefully so you don’t shake dust into the air. If it’s washable, take it outside to clean.
3. Check the Fit and Direction
Look for arrows on the new filter, these show airflow direction. Insert it the same way as the old one.
4. Secure the Cover
If your filter cover screws in, reattach it securely. If it clips, make sure it’s snug and flush.
5. Switch Your System Back On
Done! Your system will now run more efficiently and your indoor air will be cleaner within minutes.
Remember, if you’ve chosen a reusable filter, follow the manufacturer’s instructions for washing and drying before reinserting it.
Some Expert HVAC Tips for Long-Term Performance
Want to extend your system’s lifespan and keep air quality top-notch? Here are some pro tips from Aussie HVAC experts:
1. Mark Filter Changes on Your Calendar
Set a phone reminder every 30–90 days based on your filter type and household needs.
2. Check the Filter Monthly in High-Use Seasons
During scorching summers or cold winters, your system runs more often. Even quality filters may clog faster.
3. Get a Yearly HVAC Service
Even with clean filters, your system needs a professional tune-up at least once a year. This catches early issues and ensures it’s running safely.
4. Upgrade if You Have Pets, Allergies or Smoke
Standard filters might not cut it if you have multiple pets, live near bushfire-prone areas, or deal with allergies. Step up to pleated or HEPA-grade filters.
5. Seal Leaky Ducts
If your ducts are leaking air, your system has to work harder, filter included. Get a technician to inspect and seal any leaks.
Final Thoughts
So, how often change air filter in a home?
Think of it this way: if you wouldn’t drink water through a dirty straw, don’t breathe through a filthy filter. So, here the simple answer is: every 1–3 months, depending on your filter type, lifestyle, and environment.
Changing your air filter regularly isn’t just about protecting your HVAC, it’s about protecting your lungs, your comfort, and your wallet.
FAQs: What People Ask About Ducted Aircon Sizing
Every 1–2 months. Pet hair and dander clog filters quickly, especially in ducted or split systems.
Yes. Ducted systems rely heavily on clean filters to maintain airflow and energy efficiency. Aim for every 2–3 months, more in summer.
Expect higher power bills, poorer air quality, and potential system damage. Long-term neglect can lead to expensive repairs or full replacements.
Check the side of your current filter or your system’s manual. Sizes are usually printed in millimetres (e.g. 300mm x 400mm x 25mm).
Absolutely. Blocked filters recirculate dust, allergens, and bacteria—aggravating asthma, allergies, and respiratory conditions.