Every air conditioner works by exchanging heat across an aluminium coil. Cold refrigerant flows through the coil, room air blows across it, and the heat transfer is what cools your room. When the coil is coated in biofilm — the dust-and-bacteria slime that grows on wet metal — the heat transfer drops dramatically.
The compressor doesn't know that. It keeps running at full power trying to reach the set temperature. That's how a dirty system can cut cooling output by 20–30% while your power bill goes up.
The real cost
For an average Fraser Coast home running an AC 5 hours a day through summer, a badly clogged system can add $150–$300 to a quarterly bill compared to a clean one. A professional clean typically pays for itself within a single billing cycle.
Signs your bill is being pushed up
Longer run times, the unit rarely turning off, warm air out of the vents on high fan, and the outdoor unit sounding louder than usual are all classic symptoms of a coil that needs washing.
