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Computer Energy Conservation

A typical desktop PC with a 20” flat panel LCD monitor requires about 100 watts – 80 for the computer and 20 for the monitor. Left on 24/7 for one year, the system will consume 874 kWh of electricity. That’s enough to release 750 lbs. of carbon dioxide into the atmosphere – the equivalent of driving 820 miles in an average car.

To reduce power usage by as much as 75%, put your computer into a power saving mode when you won’t be using it for an extended period of time and enable power management features during shorter periods of inactivity.

As you can see from the chart below, the energy needed to power all computers on campus can really add up, but the total energy savings to the University can be significant if everyone will do their part to help cut energy usage.

Power Optimization for Campus Computers
Yearly Average 1580580 kWh
Optimized 388501 kWh

An Optimized computer is defined as being in use for 5 hours per day, on for 3 hours, and in standby for 16 hours.

  • Yearly Average is based on none of the campus computers being fully optimized.
  • Optimized is based on all campus computers operating in an optimized manner.

Turn these off

The following equipment should be turned off (or, if possible, put in Standby Mode) at the end of the day and over weekends.

monitor
Monitors

printer
Printers

scanner
Scanners

speaker
Powered Speakers

Please note that many devices, monitors in particular, continue to draw 9-16 watts of power even when turned off. To eliminate this draw, use a power strip that has the ability to switch off certain outlets and not others (or, alternatively, use two separate power strips) so that you can turn off any of the above without turning off devices that need to remain powered, such as your computer’s CPU.

Computers

As a general rule, put your computer into Sleep Mode when you are not planning to use it. Although many computers back up data and update software and the operating system at night, most will attempt to update their security software upon startup. For example, the antivirus software licensed by the campus will attempt to update itself upon computer startup (on Windows) regardless of when it has been told to look for updates.

Screen savers and power-saving modes

Screen savers do not reduce the use of power by your computer; once your screen saver kicks in, your monitor will draw its full power load. All users, whether on desktops or laptops, should configure their computers to use the power-saving or energy star modes that shut down power to the monitor, hard drive, and computer itself after periods of inactivity. Putting your computer in sleep mode allows it to use substantially less power, allows it to respond to some types of network activity, and allows you to not power off the computer.

Won’t turning my computer on and off every day damage it or decrease its usable lifetime?

No harm will come from shutting your computer down when it is not needed. Manufacturers report that turning a computer on and off will have no detrimental effects over the useful lifetime of the equipment.

We recommend that you use sleep mode if at all possible to reduce power usage but not turn off your computer. This keeps the computer available to quickly wake up to continue work and reduces power consumption the same as if the computer is powered off.

Doesn’t my screen saver save energy?

A screen saver does nothing to reduce the energy consumption of your computer. (Modern monitors don’t even benefit from the screen saver’s original purpose – preventing image burn-in.) Enabling power management is the only means of consuming less energy when your computer is turned on but is not being actively used.

Does my computer consume less energy when I’m not using it?

The difference in energy consumption between an idling computer and one that is being actively used is negligible. Properly configured power management settings are necessary to lower energy use in inactive computers.

When my computer goes to sleep, will I lose my network connection?

You will probably lose your connection. Power savings can be configured to keep your computer on the network but reduce power use by using sleep and other low power settings.

Will my computer still receive its updates if it is in sleep mode when they try to run?

Although many computers back up data and update software and the operating system at night, most will attempt to update their security software upon wake up. For example, the antivirus software licensed by the campus will attempt to update itself upon computer wake up (on Windows) regardless of when it has been told to look for updates.

Can I use Remote Desktop software from home if my computer is in power-saving mode?

Remote Desktop will work if your monitor is turned off but not if your computer is off or in standby mode. There are power saving modes that can be used to lower power usage but still allow remote access to the system.

My office uses a group printer. Should I turn that off at night, too?

This should be a group decision based on considerations such as how often someone from the group may need to print at night, how long the printer takes to become ready to print, and how close the printer is to group members’ offices.

EPEAT

Where possible, our recommended standard models for computer, laptop or monitor purchase will be EPEAT-registered, with preference for products that have achieved Silver registration or higher. EPEAT-registered products offer reductions in environmental impact across their lifecycles—from fewer toxins in manufacturing to efficient operation and easier recycling.

Laptops

Although the initial purchase costs of laptops may be higher, they draw significantly smaller amounts of power in operation than desktop systems. These savings can be as high as 80-90% and should be factored into any purchasing decisions.

Printers

Networked printers can also serve entire workgroups and may also result in energy savings over individual printers.

Energy Star

Please note that the energy star tags found on computers are not a reliable guide to energy efficiency. They refer to the computer’s support for power-saving modes and do not reflect the actual power usage of the system.

Enabling Power Management

Windows

Power management settings can be accessed by clicking Start > Control Panel > Display > Screen Saver > Power.

This should bring up a Power Options Properties dialog box that allows you to set the time to elapse until separate components enter a power saving state.

Mac

Power management settings can be accessed by clicking Apple Menu > System Preferences > Energy Saver.

This will bring up a dialog box for setting sleep times for the entire system, the monitor, and the hard disk.

For detailed instructions, including screen shots showing each step in the configuration process, consult the Energy Star site.

Sleep, Standby, or Hibernate?

Standby puts your computer into energy-saving mode, where it uses very little power.

Hibernate saves your workspace then turns the computer off.

Sleep means different things on different computers.

GREENER ELECTRONICS

Where possible, our recommended standard models for computer, laptop or monitor purchase will be EPEAT-registered, with preference for products that have achieved Silver registration or higher. EPEAT-registered products offer reductions in environmental impact across their lifecycles—from fewer toxins in manufacturing to efficient operation and easier recycling.