Variables

• The amount of energy a desktop computer uses depends on the type of computer, brand, the monitor and activities performed. Most computer brands will typically label the amount of energy the desktop will consume, but this is based only a theoretical evaluation and not on how much energy the desktop will actually consume when it is being used. Generally, a desktop computer will consume a lot of energy when it is in constant use but will use little energy when it is in sleep/standby mode.
  
  

Typical Energy Use

• A desktop will use up to 60 to 250 watts of energy when being used. When the computer is on screen saver, it uses the same amount. But when it is on sleep/standby mode, it only uses 1 to 6 watts of energy. Monitors will also burn energy. Typically, a 17-inch CRT will use 80 watts, while a 17-inch LCD will use far less at 35 watts. Different brands vary in energy use. For instance, an Apple 17-inch CRT monitor that has a mostly dark screen and few icons on the desktop will use 54 watts. A screen saver on this brand will use the same amount of energy when the computer is in use, but when it is in sleeping mode with a dark screen only 0 to 10 watts of energy is being used. PCs generally use more energy than Macs. Faster and/or older processors and heavy Internet use will also consume enormous amounts of energy.
  
  

Activities

• On an Apple iMac G5 with a built-in 20-inch LCD screen, copying files will burn 110 watts, watching a DVD 110 watts and opening a lot of pictures 120 watts. Meanwhile, the computer will use 3.5 watts of energy when it is asleep and only 97 watts when it is doing nothing. Generally, desktop computers, when not in use, consume far less energy than other household appliances.