The first is to turn off the monitor after a period of inactivity. Choose a time in minutes that will turn off the display. You can easily bring the monitor back to life by keyboard input or moving the mouse. Screen savers were originally used to prevent burn in on CRTs but quickly grew in popularity as a way to personalize the computer experience. LCD displays use a different technology and are not afflicted with burn in of static images. LCDs can display a ghostly image called image persistence, but it usually takes care of itself. To save power, turn off the monitor. Screen savers can be cool and entertaining, but they don’t give you power savings.
The second is to set the Sleep and Hibernation in the Power Options. Sleep allows you to quickly get back to full power and resume working because it pauses your activity rather than stopping it. Hibernation saves more power because it saves your work to the hard drive and then turns off the computer. It is easy to wake up your computer from Sleep or Hibernation mode and is faster because you don’t have to reboot.
For Windows, go to Control Panel and choose Power Options.
For Macs, go to Systems Preferences and choose Energy Saver.
For Unix and Linux, it is different on each OS, but you know what to do.