With a Meter

• 1). Unplug the device you want to measure the power usage for. For example, you might want to know how much electricity your computer uses per month. If so, unplug your computer from the wall.
  
  
• 2). Plug in the watt-hour meter where the device was plugged in before. These devices have both a male and female plug, much like an extension cord.
  
  
• 3). Plug your device into the watt-hour meter. Any electricity used by the device will be recorded on the digital screen of the watt-hour meter. The result will show on the screen as kilowatt-hours used.
  
  

Without a Meter

• 1). Find the number of watts your device uses. For example, a light bulb might use 60 watts.
  
  
• 2). Convert Step 1 to kilowatts by dividing by 1,000.
  60 / 1,000 = 0.06
  
  
• 3). Multiply Step 2 by however many hours the device is on. For example, if your light bulb is on for four hours, you have used: 0.06 * 4 = 0.24 kilowatt-hours.