Seven Power-Saving Tips for Your Computer
1. Dial down your screen brightness. The brighter your screen, the more power it uses.
2. Turn off your system completely at the end of the day, instead of putting it in sleep mode.
3. If you (still) have a CRT, consider upgrading to an LCD. An LCD uses about 1/3 of the power (and causes less eyestrain to boot).
4. Forgot the screen saver. Most monitors no longer are in danger of having images burned into them, and screen savers actually use up monitor power.
5. If you'll be away from your computer or other devices for a long period of time (say, while on vacation), consider unplugging them completely.
6. Look for the Energy Star certification when purchasing new computer systems or electronic devices.
7. Enable any power-saving features on your computers, monitors, and peripherals such as printers.
Source : pcmag.com