To calculate the cost of your electricity, whether for a particular appliance or other device, you need to know the rate of consumption and the price of the electricity. The former you can find either printed on the unit or in the manual. In addition to the rate of power usage, the duration of usage is part of the calculation. For the cost or the electric power, check your bill. The bill will show the price per power unit, the kilowatt-hour. That unit equals a consumption rate of 1,000 watts, in operation for one hour.
Review your manual, or check the unit you are measuring, to see the rate of consumption of power. This will be shown in watts. An appliance such as a dryer or water heater should have this noted prominently, usually on the back of the unit, or on the Department of Energy label, if this hasn't been removed. Check the unit's manual if you have difficulty finding this.
Determine how long the unit will operate in a month, in hours. You can also use other time units such as year or day, whichever is most pertinent to your calculation.
Multiply the wattage by hours of use. For instance, if the wattage is 455 and the use time is 23 hours, the total is 10,465 watt-hours.
Divide this figure by 1,000. This shows kilowatt-hours. Here, the result is 10.465 kilowatt-hours.
Multiply this amount by the electric price. This will be on your electric bill. The price is per kilowatt-hour. In this example, if the kilowatt-hour price is 17.7 cents, the cost of your electricity is 185 cents, or $1.85.
Repeat this procedure as required, should you wish to assess an aggregate cost of electrical usage for a group of appliances or units.
Bill Brown has been a freelance writer for more than 14 years. Focusing on trade journals covering construction and home topics, his work appears in online and print publications. Brown holds a Master of Arts in liberal arts from St. John's University and is currently based in Houston.