Reducing your computer's power consumption can be a surprisingly easy way to save money, do a little something for the planet, and extend your equipment's life.

There are three ways to manage the power consumption of your computer:

1. Shut it down when it's not in use. (See below for guidelines.)
2. Manually put it in low-power mode. (See below for guidelines.)
3. Use your system's power-management features. (We'll cover this in a blog post next week.)

1. Shut Down Your Computer when It's Not in Use

The U.S. Department of Energy's When to Turn Off Personal Computers advises, "For energy savings and convenience, consider turning off the monitor if you aren't going to use your PC for more than 20 minutes; [and] both the CPU and monitor if you're not going to use your PC for more than two hours."

If you are one of those lucky organizations that has an IT department that regularly backs up its computers, check in with them about policies around shutting down your computer at night. (Some IT departments may want you to leave your computer fully powered at night for backup or admin purposes.) At the very least, be sure to turn off your monitor, speakers, and other peripherals to reduce your energy usage.

Still not convinced? EnergyStar has compiled a table of estimated energy savings for powering down your computer. As you can see, whether or not you're not using EnergyStar products, the energy savings are enormous. (Note that your computer consumes power even when it is in off mode. In fact, according to a 2007 New York Times article, "The Department of Energy estimates that in the average home, 40 percent of all electricity used to power home electronics is consumed while the products are turned off.")

Computer	EnergyStar Qualified Unit	Conventional Unit
Average power for	Watts	Watts
Active mode	109.0	115.0
Idle mode	60.0	84.0
Sleep mode	4.0	6.0
Off mode	2.0	3.0
Difference: Active mode vs. off mode	107	113
Difference: Idle mode vs. off mode	58	81

Tip: If you are having trouble understanding watts, think about the light bulbs in your house. Before we had CFLs, many of us used bulbs that were 60, 75, or 100 watts. Think how brightly a 100 watt bulb glowed in your home. An Energy Star–compliant computer in active mode consumes 9 percent more energy than that.

Assuming that you shut down your computer for 16 hours a day (versus keeping it active 24-7), you could save $0.16 and 2.63 pounds of carbon dioxide per day, or 960 pounds per year. A car emits about 2,666 pounds of carbon dioxide per year, meaning that the energy you will save over the course of the computer’s life (3 years = 2,880 lbs) will equal a bit more than taking a car off the road for a year.

2. Set Your Computer to Stand by/Sleep or Hibernate

Another way to reduce your computer's energy consumption is to set it to Stand by (for Macs, "sleep" mode), or to Hibernate mode. As EnergyStar's chart illustrates, setting your computer to sleep/stand by mode consumes significantly less power than even leaving it idle.

The distinction between hibernate and stand by modes can be murky. Blog LifeHacker helps distinguish between the two:

Stand By:
Your machine recovers quickly as your data is stored in RAM. The slower part is waking up the peripherals. Although your machine is in "standby" the power has been cut to items such as your hard drive and monitor. You're running your machine in a very low power mode, but it is still on. This mode can be useful if you're on a notebook and need to conserve your battery while you step away.

Hibernate:
The big difference is that your PC has shut down and is not pulling power. Another difference is that your data is saved to your hard disk and not RAM. This makes it a safer, but slower option for shut down and resume.

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