How Much Does It Cost to Run a Humidifier?

How much a humidifier costs depends almost entirely on how it turns water into vapor. An ultrasonic humidifier vibrates a small plate to throw off a fine mist and draws about 20 to 40 W. An evaporative model blows air through a wet wick and draws 10 to 60 W, mostly for the fan. A warm mist or steam humidifier boils the water and draws 200 to 400 W. The Levoit models we list show the spread: the Superior Studio evaporative is rated 12 W and the OasisMist 450S warm and cool mist 280 W.

The default here is 40 W for 10 hours, 0.4 kWh, about 7 cents a day at the national average rate, which fits an ultrasonic or evaporative unit in a bedroom. A 280 W warm mist unit running the same 10 hours uses 2.8 kWh, about 48 cents a day or $14.53 a month, seven times as much. Warm mist models are often chosen because boiling kills bacteria in the tank and the mist feels pleasant in winter, but the electricity cost is the trade-off.

A built-in humidistat helps more than the wattage. Without one the humidifier runs until the tank is dry. With one it shuts off at the target, usually 40 to 50 percent, which also keeps windows from sweating and mold from growing. Above 50 percent in winter, condensation on cold windows and walls becomes a problem.

Water quality changes the picture too. Ultrasonic units throw minerals from hard tap water into the air as a fine white dust, so many owners use distilled water. Evaporative units leave the minerals in the wick, which needs replacing. Both are costs worth counting alongside the few dollars of electricity.

Moist air does feel a little warmer at the same temperature, which can let you hold the thermostat a degree lower in a dry winter house. For the whole house at once, a furnace-mounted humidifier is often the better choice; a bypass model uses no motor of its own.