Why Your Air Conditioner Struggles During South West Heatwaves

Every year, it happens at almost the exact same time.

The first real South West heatwave rolls through sometime after Christmas. Temperatures climb into the high 30s, the house holds heat well into the evening, and suddenly air conditioners across Bunbury, Busselton, Australind and Margaret River are pushed harder than they’ve been all year.

That’s usually when people realise their system isn’t coping the way it used to.

Maybe it’s blowing air but not actually cooling the room. Maybe it runs constantly without reaching temperature. Or maybe it works fine in the morning, then struggles once the afternoon heat settles in.

The reality is, South West heatwaves expose problems that often go unnoticed during milder weather.

South West Summers Put Systems Under Real Pressure

Unlike Perth’s dry overnight cool change, parts of the South West can hold heat later into the evening, especially during still January nights.

Homes near the coast around Busselton and Dunsborough also deal with humidity and salt air, while inland areas like Collie or Harvey often experience long stretches of dry heat that force systems to run continuously.

When temperatures sit above 35 degrees for days in a row, even a good air conditioner needs to be properly sized, maintained, and functioning efficiently to keep up.

Dirty Filters Restrict Airflow

One of the most common reasons systems struggle during summer is surprisingly simple: dirty filters.

Over time, dust, pet hair, pollen and general buildup restrict airflow and make your system work significantly harder to push cool air through the home.

This becomes especially noticeable during:

• heatwaves

• busy holiday periods

• large family gatherings

• long periods of continuous use

A system that seemed “fine” during spring can suddenly feel weak once temperatures spike around late January or during those long weekends near Australia Day.

Your System Might Be Undersized

A lot of older South West homes were fitted with smaller systems years ago when:

• energy prices were different

• homes were smaller

• insulation standards varied

• open-plan living wasn’t as common

Now many homes have:

• larger living areas

• added extensions

• higher ceilings

• more glass

• extra occupants

• more heat-generating appliances

If your system constantly runs without properly cooling the space, there’s a good chance it simply isn’t sized correctly for the home anymore.

We see this regularly in older Bunbury homes that have been renovated into larger modern living spaces without updating the air conditioning to match.

Heatwaves Expose Refrigerant & Mechanical Issues

Sometimes the problem isn’t obvious until the system is under heavy load.

Low refrigerant levels, failing components, blocked coils, or worn electrical parts may still allow the system to operate during mild weather. But once a South West heatwave arrives and the unit runs for 10 hours straight, those issues become much harder to hide.

Common signs include:

• warm air coming through vents

• weak airflow

• unusual noises

• systems constantly turning on and off

• rooms cooling unevenly

• rising power bills

Coastal Conditions Affect Performance Too

Living near the coast is incredible, but salt air can be hard on air conditioning systems over time.

Homes in areas like Dalyellup, Busselton, Dunsborough and Margaret River often experience:

• faster corrosion

• outdoor unit wear

• reduced efficiency

• blocked coils from coastal debris

Without regular servicing, these small issues gradually impact performance — especially during summer when systems are already working at maximum capacity.

The Worst Time to Discover a Problem

Unfortunately, most people only notice issues when they need their system most.

Usually:

• the week school holidays start

• Christmas Day

• the AFL finals period heat

• long weekends

• or the first proper 40-degree run of summer

That’s also when HVAC companies across the South West become busiest.

Preventative servicing before summer is one of the easiest ways to avoid emergency breakdowns during peak season.

How to Keep Your System Performing Properly

A few simple things make a huge difference:

• clean filters regularly

• service the system annually

• keep outdoor units clear

• don’t ignore weak airflow

• upgrade older inefficient systems

• check thermostat settings before summer arrives

Modern systems are significantly more energy-efficient and better suited to the way South West homes operate today.

Local Experience Makes a Difference

Not every heating and cooling system behaves the same way in the South West.

A coastal home in Yallingup faces very different conditions to a family home in Eaton or a commercial space in Bunbury CBD. That’s why local knowledge matters when diagnosing performance issues and recommending solutions.

At Pergo Air, we help homeowners and businesses across the South West keep their systems running reliably through summer, winter, and everything in between — with professional servicing, repairs, cleaning, and installation tailored to local conditions.