Smart Calculator Pro

Smart Calculator Pro

HomeFinanceHealthMathConstructionEveryday LifeGuidesCompare
Free toolsReviewable pages

Electricity Cost Calculator

Find out how much it costs to run any electrical appliance or device. Enter the wattage, how many hours you use it per day, and your electricity rate to see the daily, monthly, and yearly cost of running it.

The power rating of the appliance in watts. Check the label on the device or its manual.

How many hours per day the appliance is running.

Your electricity rate in dollars per kilowatt-hour. Check your utility bill for this rate.

How many of this device or appliance you are running.

This calculator converts an appliance's wattage into kilowatt-hours of energy consumption, then multiplies by your electricity rate to show you the cost per day, per month, and per year. You can also calculate for multiple devices at once.

How It Works

Electricity Cost Formula

Daily Cost = (Watts x Hours x Quantity) / 1000 x Cost per kWh

Daily cost equals the wattage times hours of use times the number of devices, divided by 1,000 to convert to kilowatt-hours, then multiplied by your cost per kWh.

Convert watts to kilowatts: kW = watts / 1,000

Daily kWh = kW x hours per day x quantity

Daily cost = daily kWh x cost per kWh

Monthly cost = daily cost x 30 days

Yearly cost = daily cost x 365 days

Important Notes:

  • •This calculator assumes constant power draw at the rated wattage
  • •Actual consumption may vary if the device cycles on and off (e.g., refrigerators, HVAC)
  • •The U.S. average residential electricity rate is approximately $0.12-$0.16 per kWh as of 2025
  • •Monthly calculations assume 30 days; yearly calculations assume 365 days

Worked Example

Running a 100-watt light bulb for 8 hours per day at $0.12 per kWh.

Inputs:

  • watts:100
  • hours Per Day:8
  • cost Per Kwh:0.12
  • quantity:1

Result:

The bulb uses 0.80 kWh per day, costing $0.10 per day, $2.88 per month, and $35.04 per year.

Who Is This Calculator For?

  • homeowners tracking energy costs
  • renters budgeting for utilities
  • anyone comparing appliance efficiency

Frequently Asked Questions

Check the label on the back or bottom of the appliance, which usually lists the wattage. You can also check the product manual or the manufacturer's website. If only amps and volts are listed, multiply them together to get watts (watts = amps x volts). A plug-in electricity usage monitor can also measure actual wattage.
A kilowatt-hour is a unit of energy equal to using 1,000 watts for one hour. It is the standard unit used by utility companies to measure and bill electricity consumption. For example, a 100-watt bulb running for 10 hours uses 1 kWh of electricity.
A typical 1,500-watt space heater running for 8 hours per day at $0.12 per kWh costs about $1.44 per day, $43.20 per month, and $525.60 per year. This makes space heaters one of the most expensive household appliances to operate continuously.
The biggest electricity consumers in a typical home are air conditioning and heating systems, water heaters, clothes dryers, electric ovens and stoves, and refrigerators. Among smaller appliances, space heaters, gaming PCs, and older plasma TVs tend to draw the most power.
Switch to LED bulbs, unplug devices when not in use (to avoid phantom power draw), use a programmable thermostat, run major appliances during off-peak hours if your utility offers time-of-use rates, upgrade to Energy Star-rated appliances, and seal air leaks in your home to reduce heating and cooling costs.
Yes. Many devices draw small amounts of power even when turned off, known as phantom power, standby power, or vampire draw. Chargers, TVs, game consoles, and computers are common culprits. Phantom power can account for 5-10% of a household's total electricity use. Using power strips that you can switch off helps eliminate this waste.

Related Tools

Last updated: April 20, 2026