With so much talk about reducing electricity consumption, it is well worth thinking about your computer. If swapping just one incandescent lightblub for a more efficient CFL per household would eliminate the need for hundreds of power plants across the world, just think how much is saved by swapping a energy-hogging desktop computer for a laptop?
A desktop computer uses about 120 - 150 watts whenever it is on.
A laptop used about 30 watts, but only when it is working. Laptops are designed to use as little power as possible. When a laptop isn't "thinking", it requires less energy.
Computers have to continually process something, so when not busy with a useful task, they simply idle, continually looping through code that does nothing more than give the computer something to do.
This is done to extend for how long the battery can power the computer. The result is a computer that uses far less energy when plugged in.
You can easily save 80 to 100 watts by choosing an average laptop over an average desktop.