Though there is a small surge in energy when a computer starts up, this small amount of energy is still less than the energy used when a computer is running for long periods of time.
For energy savings and convenience, consider the following guidelines:
Turn off the monitor if you aren’t going to use your PC for more than 20 minutes.
Turn off both the CPU and monitor if you’re not going to use your PC for more than 2 hours.
Make sure your monitors, printers, and other accessories are on a power strip/surge protector. When this equipment is not in use for extended periods, turn off the switch on the power strip to prevent them from drawing power even when shut off. If you don’t use a power strip, unplug extra equipment when it’s not in use. Most PCs reach the end of their “useful” life due to advances in technology long before the effects of being switched on and off multiple times have a negative impact on their service life. The less time a PC is on, the longer it will “last.” PCs also produce heat, so turning them off reduces building cooling loads.
Sleep Mode and Power Management Features. Many computers available today come with a sleep mode or power management feature. ENERGY STAR? estimates that using these features will save you up to $30 each year on your electricity bills. Make sure you have the power-down feature set up on your PC through your operating system software. This has to be done by you; the power management features usually are not already enabled when a computer is purchased. Learn how to activate the power management features on your computer.
ENERGY STAR monitors consume 2 watts or less in sleep mode. Follow the instructions for your particular model to ensure power management features are enabled so your monitor will automatically go into sleep mode after a period of inactivity. You can save even more by manually turning off your monitor when you’re not using it; ENERGY STAR qualified monitors consume 1 watt or less when off.
Note that screen savers are not energy savers. Using a screen saver may in fact use more energy than not using one, and the power-down feature may not work if you have a screen saver activated. In fact, modern LCD color monitors do not need screen savers at all.