A kilowatt is the unit of energy that the bulk of an electricity bill is measured upon. The cost of a kilowatt is determined by the wattage of various lightbulbs, appliances, and other items in a household or business.
Cost of a Kilowatt
The U.S. Energy Information Administration stated in July 2010 that the average cost of a residential kilowatt in the United States is 12.1¢/kWh, ranging from 8.9¢ in Washington to 28.3¢ in Hawaii .
Calculating Kilowatt Hours
You have reached one kilowatt-hour when you have used 1,000 watts for 1 hour. For instance, a large window-unit air conditioner with a wattage of 1,500 that is used for one hour calculates into 1.5 kWh. You can manually calculate the number of kilowatt-hours of an appliance or other object by taking the wattage of the device, multiplying it by the number of hours used, and then dividing that sum by 1000. If you don’t feel like doing the math, Michael Blue Jay (also known as Mr. Electricity) offers a convenient calculator  for computing kilowatt-hours.
Taking a look at your own electric bill can help calculate the actual kWh rate you are charged. Keep in mind that your bill may display multiple kWh rates (such as one for “delivery” and one for “electricity use”). To reach a total kWh rate, add all of the rates together.