The On-Off Debate:
(Adapted from Rocky Mountain Institute's Home Energy Brief No. 7)

Should you turn off you computer or keep it running?

Arguments that thermal cycling harms the internal components of computers don't seem to be well founded. Modern computers are designed to handle 40,000 on-off cycles before failure, and you're not likely to approach that number during the average computer's five- to seven-year life span. In fact, IBM and Hewlett Packard encourage their own employees to turn off idle computers, and some studies indicate it would require on-off cycling every five minutes to harm a hard drive.

Meanwhile, turning off your computer when not in use not only saves electricity, but also reduces pollution created by the power plant that supplies electricity for the computer. In an office setting, it also decreases the air-conditioning load, which saves more energy and pollution.

In light of all this, the recommended benchmark is this:

Turn off your monitor whenever it will be idle for 15 minutes or more, and turn off the computer when it will be idle for 2 hours or more.

Energy Star Computers:

Many computers are now "Energy Star" rated, a designation created by the U.S. Environmental Protection Agency. In order to be Energy Star compliant, a computer must have a built in sleep function to automatically conserve energy. (Sleep mode is not to be confused with screen-saving programs, most of which don't save any energy.) In order to be effective, though, you must ENABLE these functions on your computer.

If Energy Star products capture two-thirds of the computer market by the year 2000, as EPA hopes, their use could save up to $1 billion worth of electricity annually and reduce carbon dioxide emissions from power plants by 20 million tons - an output equivalent to 5 million cars.

Laptops:

Because laptops are designed to run off battery power, they use far less energy than desktop monitors. Most desktop computers use 80-160 watts of electricity - about the same as one or two standard light bulbs. In contrast, laptop models typically use a maximum of 15 watts. If you are deciding between these two different designs, please consider that laptops are the clear winners in energy efficiency.

Enabling your Computer's Sleep function:
Enabling your computer's sleep function will save energy and money. If your computer is not in use for a period of time, the internal "engine" will automatically go to sleep, thus saving power. To wake it up, all you do is hit any key, and in about one second, it is rearing to go again.

Enabling sleep function on IBM:

1 Click "Start" at the bottom of the screen
2 Go to "Settings" and click on "Control Panel"
3 Open "Display" and click on "Screen Saver"
4 Check "Low Power Standby" and "Shut off Monitor" boxes
5 Select time
6 Go back to "Control Panel" and select "Power"
7 Check "allow windows to manage power" box
8 Click on "disk drive" tab
9 Select time

Enabling sleep function on Macintosh:

1 Go to Apple Icon
2 Go to "Control Panel"
3 Open "Energy Saver"
4 Click on "Show Details" (at bottom of box)
5 Select times for system, display and hard disk