Estimate how much a furnace fan adds to your electric bill from wattage, daily run time, fan count, and electricity price.
Table of contents
How to use our Furnace Fan Electricity Cost Calculator
- Enter Furnace fan power in watts. If the motor label gives amps and volts, multiply amps by volts to estimate watts.
- Enter Fan run time as the average hours per day the blower runs. Use 24 for an always-on fan setting.
- Enter Your electricity price in $ per kWh from your bill, then enter Number of furnace fans.
- Optional: enter Compare with another price to see the monthly cost difference without changing your main price.
- Check the output by asking if the Electricity used per day makes sense: watts divided by 1000, multiplied by fans and hours per day.
Definitions
Furnace fan power: The electrical power used by the blower while it is running, entered in watts.
Watt: A unit of electric power. Higher watts means the fan uses energy faster.
kWh: Kilowatt-hour, the electricity unit commonly used for billing. One kWh is 1 kilowatt used for 1 hour [1].
Your electricity price: The cost for each kWh of electricity, usually shown on an electric bill in $ per kWh.
Compare with another price: An optional second $ per kWh value used only for the comparison cost and monthly difference.
Cost per running hour at your price: The estimated cost for one hour of fan operation for all furnace fans entered.
Common mistakes and quick fixes
Mistake: Typing a motor size like 1/2 HP into Furnace fan power.
Fix: Enter Furnace fan power in watts, or convert from the label using amps times volts if watts are not listed.
Mistake: Using thermostat-on time instead of actual Fan run time.
Fix: Estimate how many hours the blower itself runs each day, and enter 24 only for an always-on fan mode.
Mistake: Entering a monthly bill total into Your electricity price.
Fix: Use the price per kWh from your bill, such as 0.16, not the total dollars owed.
Mistake: Leaving Number of furnace fans at 1 when adding more than one blower.
Fix: Enter the actual whole number of furnace fans you want included in the estimate.
Mistake: Reading Monthly cost change vs compare price as an added charge even when it is negative.
Fix: A negative Monthly cost change vs compare price means Your electricity price is cheaper than Compare with another price for the same fan use.
Limitations & Key Assumptions / Boundary Conditions
- The calculator assumes Furnace fan power is the average running wattage while the blower is on. Startup surges and variable-speed changes are not modeled.
- Monthly results use an average month of 365 days divided by 12, so a specific calendar month may be a little higher or lower.
- Fan run time is treated as the same every day. Heating season, cooling season, thermostat settings, and always-on fan mode can change the real average.
- Your electricity price should include the charges you want counted. If your bill has tiered rates, time-of-use rates, fixed fees, or taxes, this simple $ per kWh estimate may not match the bill exactly.
- Compare with another price changes only the price per kWh. It does not change fan use, weather, equipment efficiency, or bill fees.
- The estimate is for electricity used by the fan motor only. It does not include gas, oil, heat pump compressor electricity, or other HVAC equipment.
Methodology
How the calculator works
The calculator first converts Furnace fan power from watts to kilowatts because electricity use on bills is commonly measured in kilowatt-hours, or kWh [1]. It then multiplies by Number of furnace fans and Fan run time to find daily energy use. Costs are energy use multiplied by Your electricity price.
power_kw = fan_power_w / 1000
daily_kwh = power_kw * fan_count * hours_per_day
monthly_kwh = daily_kwh * 365 / 12
yearly_kwh = daily_kwh * 365
cost = kwh * electricity_rate
monthly_cost_change_vs_compare_price = monthly_cost_at_your_price - monthly_cost_at_compare_price
Mini example
If Furnace fan power is 500 watts, Fan run time is 8 hours per day, Number of furnace fans is 1, and Your electricity price is $0.16 per kWh, then power is 0.5 kW. Daily use is 0.5 * 1 * 8 = 4 kWh. Monthly use is 4 * 365 / 12 = 121.67 kWh. Monthly cost at your price is 121.67 * 0.16 = $19.47. If Compare with another price is $0.12 per kWh, monthly cost at compare price is $14.60, and Monthly cost change vs compare price is $4.87.
Rounding and signs
Money results are rounded to cents for display. Energy results are rounded to practical decimal places. Monthly cost change vs compare price keeps its sign: a positive value means Your electricity price costs more than the compare price, and a negative value means it costs less.