Calculating kilowatt hours

• 1). Find out how many watts a device uses per hour. Look on the label or in the instruction manual, or use Mr. Electricity's interactive chart at michaelbluejay.com (see Resources for link). A 60W light bulb obviously uses 60 watts per hour. An average laptop uses about 45 watts per hour.
  
  
• 2). Multiply the wattage by .001 to get the kilowattage (kW). A 60W light bulb uses 0.06kW per hour, for example.
  
  
• 3). Multiply the kW by the number of hours of usage to get the kW hours (kWh). A 0.06kW light bulb uses 1.44kWh in 24 hours.