Exhaust fans are among the cheapest appliances to run — a few dollars a year — so running yours long enough to clear moisture costs almost nothing and saves far more by preventing mould.
Tiny CostA few dollars a year
Run It LongerCheaper than mould
Worth ItPrevents costly damage
Are Exhaust Fans Cheap to Run?
Yes — exhaust fans are among the cheapest appliances in the home to run. A typical bathroom fan draws only a small amount of electricity, similar to a light globe, so the cost of running it is minimal even with generous use. This matters because people sometimes switch the fan off early to ‘save power’ — but the saving is negligible and the cost of the resulting mould is not. Running cost should never be the reason to under-ventilate.
What It Actually Costs
In practical terms, running a bathroom exhaust fan normally — including for a good while after each shower — costs only a few dollars a year. Larger or more powerful fans cost a little more, but it’s still very modest. Compared with virtually everything else that uses electricity in a home, an exhaust fan’s running cost is trivial. The numbers make the decision easy: run it properly.
Why Running It Longer Pays
The most important takeaway is that running the fan longer — long enough to actually clear the moisture — costs almost nothing and prevents a lot. Mould from under-ventilation leads to cleaning, repainting, surface repairs and sometimes remediation, all far more expensive than years of fan running. So the few extra minutes (or a run-on timer) to dry the room is money very well spent. See our timer & sensor guide.
Efficient Ventilation
If you want to be efficient about it, a humidity sensor runs the fan only when moisture is actually present and stops it once the air is dry — ventilating exactly as needed, neither too little (mould) nor needlessly long. A correctly sized fan also clears the moisture faster, so it doesn’t need to run as long. But even without these, the base running cost is so low that efficiency is a minor consideration next to simply ventilating properly.
Getting the Most From It
To get the best value: run the fan during and after showers/cooking long enough to clear the moisture (a run-on timer or humidity sensor makes this effortless), make sure the fan is correctly sized and vents outside so it works efficiently, and keep it clean so it moves air freely. Done this way, an exhaust fan is a tiny running cost that protects your home from far costlier moisture damage. Call 0431 918 137 for fan advice or service.
Frequently Asked Questions
How much does it cost to run a bathroom exhaust fan?
Very little — a typical bathroom exhaust fan uses only a small amount of electricity (similar to a light globe), so running it costs in the order of a few dollars a year with normal use, even running it well after each shower. It’s one of the cheapest appliances in the home to operate. This is why the cost of running it should never be a reason to switch it off early — the saving is negligible and the mould risk is real.
Is it expensive to leave the exhaust fan running after a shower?
No — running the fan for an extra 10–30 minutes after a shower (which is exactly what clears the lingering moisture) adds a trivial amount to your electricity bill, because exhaust fans draw so little power. The cost is far outweighed by the benefit of a dry, mould-free bathroom. A run-on timer makes this automatic. Worrying about the running cost of an exhaust fan is, in practice, not worth it. See our
timer guide.
Does running an exhaust fan use a lot of electricity?
No — exhaust fans are low-power appliances, typically drawing roughly as much as a light bulb, so even regular, generous use barely registers on a power bill. Larger or more powerful fans use a little more, but it’s still very modest. The energy cost is essentially negligible compared with the benefit of removing moisture and preventing mould and damp damage.
Is it cheaper to prevent mould with a fan than to fix it?
Far cheaper. Running an exhaust fan costs a few dollars a year, while dealing with mould — cleaning, repainting, repairing damaged surfaces, or remediation — costs vastly more, not to mention the health and comfort impact. So using the fan properly is one of the best-value habits in the home: a tiny running cost that prevents an expensive problem. The economics overwhelmingly favour running the fan.
Do timer or humidity-sensor fans cost more to run?
Negligibly — they still draw the same small amount of power while running; they just ensure the fan runs for the right duration. In fact, by running the fan exactly long enough (and a humidity sensor only when needed), they can be efficient, avoiding both under-running (mould) and pointless over-running. The tiny extra runtime to properly clear moisture is well worth it. See our
timer & sensor guide.
Exhaust Fan Install, Repair or Clean? Talk to FreshDuct
Install, replacement, repairs & cleaning across Melbourne — 7 days a week. Call or request a quote.
