Estimate how much a humidifier adds to your electric bill using watts, run time, electric rate, and seasonal use.
Table of contents
How to use our Humidifier Running Cost Calculator
- Choose a Humidifier type to fill a starter wattage, or choose Custom wattage if you know your own label number.
- Enter Power use, Hours used per day, Electricity rate, and Days used per month from your unit label and electric bill.
- Open Advanced options if the humidifier cycles on and off, needs Extra fan or blower power, or is used for only part of the year.
- Click Calculate and read Cost for this bill month first, then compare Cost per day used and Electricity used this bill month.
- Sanity-check the result by asking if the Power use looks like watts, not amps or volts, and if Runs at full power matches how often the unit actually runs.
Definitions
Power use: The electric power the humidifier draws while running, measured in watts (W).
Kilowatt-hour (kWh): A unit of energy on electric bills. It equals power in kilowatts multiplied by time in hours [1].
Electricity rate: The price you pay for each kWh. Use the full $ per kWh rate from your bill when possible.
Runs at full power: The percent of scheduled time the humidifier is actually drawing its entered power. A humidity control can make this less than 100%.
Extra fan or blower power: Added watts from another fan or furnace blower that runs mainly because the humidifier is running.
Cost for this bill month: The estimated added electricity cost for the entered Days used per month.
Common mistakes and quick fixes
Mistake: Entering volts or amps in Power use instead of watts.
Fix: Use the watt number from the label, manual, or a power meter for Power use.
Mistake: Typing 18 in Electricity rate when your bill says 18 cents per kWh.
Fix: Enter 0.18 for Electricity rate because the calculator uses $ per kWh.
Mistake: Using 24 for Hours used per day when a humidity control only lets the unit run part of that time.
Fix: Keep Hours used per day as the scheduled time, then lower Runs at full power to model cycling.
Mistake: Leaving Days used per month at 30 when you only use the humidifier during dry weeks.
Fix: Set Days used per month to the number of days you expect it to run in that bill period.
Mistake: Ignoring Extra fan or blower power for a whole-house setup that runs a blower because of the humidifier.
Fix: Add that extra wattage in Extra fan or blower power, or leave it at 0 for most portable units.
Mistake: Reading Cost for the months you use it as a full-year total when Months used per year is less than 12.
Fix: Set Months used per year to 12 only if the humidifier runs all year.
Limitations & Key Assumptions / Boundary Conditions
- The estimate assumes the entered Power use and Extra fan or blower power are steady whenever the unit is counted as running.
- Runs at full power is an average. Real cycling can change with humidity setting, room dryness, temperature, door openings, and water level.
- Preset wattages are only starting points. The wattage on your own label, manual, or power meter is better.
- The calculator includes electricity cost only. It does not include water, filters, pads, cleaning supplies, repairs, or equipment cost.
- Electricity rate can vary by time of day, tier, fees, taxes, or seasonal pricing. A single $ per kWh value is an average.
- Season cost uses Days used per month multiplied by Months used per year, so it assumes a similar use pattern in each selected month.
- Whole-house systems can interact with furnace controls. Extra fan or blower power should include only the added blower use caused by humidifier operation.
Methodology
How the calculator works
The calculator first adjusts the entered watts for optional added fan power and for the percent of scheduled time the setup runs at full power. It then converts watts to kilowatts by dividing by 1000, because 1 kilowatt equals 1000 watts [1]. Energy use is found by multiplying kilowatts by hours.
effective_power_w = (power_w + extra_fan_power_w) * duty_cycle_percent / 100
daily_kwh = effective_power_w / 1000 * hours_per_day
daily_cost = daily_kwh * electricity_rate
monthly_kwh = daily_kwh * days_per_month
monthly_cost = daily_cost * days_per_month
season_cost = daily_cost * days_per_month * months_per_year
hourly_cost = effective_power_w / 1000 * electricity_rate
Worked example
For the default ultrasonic example, Power use is 25 W, Hours used per day is 8, Electricity rate is $0.18 per kWh, Days used per month is 30, Runs at full power is 100%, Extra fan or blower power is 0 W, and Months used per year is 5. Effective power is 25 W. Daily energy is 25 / 1000 * 8 = 0.2 kWh. Daily cost is 0.2 * 0.18 = $0.036. Cost for this bill month is $0.036 * 30 = $1.08. Cost for the months you use it is $1.08 * 5 = $5.40.
Calculation notes
Cost for this bill month is shown first because it is the easiest number to compare with one electric bill. Cost for the months you use it is a seasonal estimate, not a forced 12-month annual cost. Cost per scheduled hour is an average clock-hour cost after Runs at full power is applied, so it can be lower than the cost during the exact moments the unit is drawing full power.