Humidifier running costs vary by a factor of ten depending on type. An ultrasonic humidifier running 12 hours a day costs roughly the same as a phone charger left plugged in; a warm mist vaporiser running the same hours costs closer to a small space heater. This guide breaks down real electricity costs by humidifier type using 2026 Australian electricity rates.

Humidifier Type Power Draw Daily Cost (12 hrs, $0.30/kWh) Monthly Cost
Ultrasonic (cool mist) 20-40 W $0.09-$0.17 $2.60-$5.25
Evaporative 17-50 W $0.06-$0.18 $1.85-$5.40
Air washer (e.g. Venta) 8-12 W $0.03-$0.04 $0.87-$1.30
Warm mist (steam) 200-400 W $0.72-$1.44 $21.60-$43.20

Why Warm Mist Humidifiers Cost 5-10x More to Run

Warm mist vaporisers boil water to produce sterile steam, and boiling requires roughly 2,260 kilojoules of energy per kilogram of water converted to vapour—the latent heat of vaporisation. This physical requirement is unavoidable regardless of manufacturer or model. Ultrasonic and evaporative humidifiers convert electrical energy directly into mechanical vibration or airflow, sidestepping the far larger energy cost of a full liquid-to-gas phase change via heating. If running cost is a priority, ultrasonic or evaporative models are the clear choice; warm mist units are best reserved for occasional use or households prioritising sterile output over cost.

State-by-State Electricity Rate Impact

The $0.30/kWh figure used above is a reasonable national average for 2026, but actual rates vary by state and retailer. South Australia typically has the highest residential electricity rates in the country (often $0.35-$0.45/kWh), meaning a warm mist humidifier there can cost $25-$55 AUD per month. Tasmania and Queensland tend to have somewhat lower rates. Check your own electricity bill for your actual per-kWh rate and scale the figures in the table proportionally.

Lowest-Cost Option: Air Washers

Air washer humidifiers (a hybrid humidifying/purifying technology used by brands like Venta) draw as little as 8 watts, making them the cheapest humidifier type to run continuously—under $1 AUD per month at 12 hours daily use. They also avoid white dust and filter replacement costs, though upfront purchase price is typically higher than basic ultrasonic units.

Total Cost of Ownership: Beyond Electricity

Running cost is only part of the picture. Evaporative humidifiers require wick filter replacement every 30-90 days ($10-25 AUD per filter), adding $40-100 AUD annually. Ultrasonic humidifiers using tap water may need demineralisation cartridges every 30-40 fills ($15-30 AUD each) or ongoing distilled water purchases ($10-20 AUD monthly). Warm mist units have no filters but may need periodic descaling of the heating element. When comparing total annual cost, factor in electricity, consumables, and average unit lifespan (3-5 years for most models) rather than electricity alone.

For most Australian households prioritising both low running cost and low noise, an ultrasonic cool mist humidifier remains the best all-round choice—see our full beginner's guide for a complete type comparison before you buy.