Humidifier Running Cost Calculator
See what it costs to run a humidifier: turn its wattage, daily hours and your electricity rate into a cost per day, month and season.
How it works
kWh/day = watts ÷ 1000 × hours · Cost/day = kWh × rate · Period cost = cost/day × days
A humidifier’s electricity cost comes down to its wattage, how long it runs and your utility rate. Convert watts to kilowatts by dividing by 1,000, multiply by the hours it runs to get kilowatt-hours per day, then multiply by your per-kWh price. The gap between technologies is large: ultrasonic and evaporative cool-mist units sip 20–50 W, while warm-mist models boil water and can draw 200–400 W — an order of magnitude more.
Worked example
A 40 W cool-mist humidifier left on 10 hours a day uses 40 ÷ 1000 × 10 = 0.4 kWh daily. At $0.15 per kWh that is 0.4 × 0.15 = $0.06 a day, about $1.80 over a 30-day month. A 300 W warm-mist unit on the same schedule would cost roughly $13.50 a month instead.
Frequently asked questions
Do cool-mist or warm-mist humidifiers cost more to run?
Warm-mist units cost far more because they use a heating element to boil water, typically 200–400 W versus 20–50 W for cool-mist. Over a heating season that difference can be ten-fold on the electricity bill.
Does this include the cost of water?
No — it covers electricity only. Tap water is inexpensive, but if you use distilled water to avoid white mineral dust, add that to your running cost separately.
How can I cut a humidifier’s running cost?
Use a hygrometer or built-in humidistat to run only until you hit 40–50% relative humidity, choose an energy-efficient cool-mist model, and size it to the room so it isn’t running flat-out around the clock.
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This calculator is for educational purposes. Double-check important results before acting on them.