Microsoft

Use Windows XP's power management features to lower energy bills

You could be wasting thousands of dollars every year simply by not using Windows XP's OnNow Standby mode. Here's information on how to calculate your savings and how to set up the OnNow on all your PCs.


Many IT professionals make the mistake of only using Windows XP’s power management features for laptop users who need to conserve battery power while on the road. However, using these power management features with an OnNow-capable desktop system will allow you to conserve electricity in the office, which in turn can save your company a bundle in power costs.

Here’s how you can configure these OnNow-capable desktop systems to take full advantage of Windows XP’s power management features. We’ll also examine some of the features that the OnNow technology brings to the table.

More information
You can learn more about Windows XP’s support of OnNow and ACPI in a Microsoft white paper titled "Windows Power Management: Instant PC availability and energy savings."

OnNow background
The term “OnNow” describes a condition in which a computer appears to be turned off, but is actually in a low power state where it can, nonetheless, immediately respond to requests from both users and devices.

If you’ve been in the computer industry for a while, you know that Microsoft has been talking about OnNow since the 1996 WinHEC (Windows Hardware Engineering Conference) convention where Microsoft described a technology that would allow you to turn on a computer and begin using it immediately, just like you would other household appliances, such as a television or stereo system. Since that time, we’ve seen four versions of the Windows operating system come and go, each with varying degrees of success (or failure, depending on how you look at it) with regard to achieving the OnNow power management promise. Finally, with the convergence of hardware that adheres to a single power management standard and a finely tuned operating system that has the ability to take complete control over power management features, Windows XP actually delivers the OnNow power management promise.

Now, it’s important to keep in mind that in order for you to reap the benefits of the OnNow power management features with Windows XP, the computer and its peripheral devices must be fully compliant with the Advanced Configuration and Power Interface (ACPI) specification (see below). Hardware that adheres to the ACPI specification allows Windows XP to maintain control over, and thus regulate, the power supplied to all components.

ACPI compliance
To see if your computer is fully compliant with the Advanced Configuration and Power Interface (ACPI) specification, right-click on the My Computer icon on the Start menu and select Properties. When you see the System Properties dialog box, select the Hardware tab and then click the Device Manager button. When Device Manager opens, double-click on the Computer icon in the tree. When you do, you’ll see the name of the Hardware Abstraction Layer that Windows XP installed on your computer. If your system is ACPI compliant, you’ll see an item titled Advanced Configuration and Power Interface (ACPI) PC.

Where does the money savings come in?
Most IT professionals are always on the lookout for ways to save money in their department, in part because doing so makes them look good in the eyes of their superiors. However, if they discover ways the IT department can save the entire company money, then, they look even better. So how can taking advantage of Windows XP’s power management features save your company money?

To begin with, let’s suppose that the standard practice in your office is to leave all the computers up and running 24 hours a day so that regular maintenance operations, such as a scheduled backup or disk cleanup, can be performed during off hours. With this in mind, let’s break down the average day into two time periods—the eight-hour business day, in which the computers in the office are in use, and the 16 hours when the office is closed.

As such, you have 16 hours in which the computers are consuming power but are not really being used. So, it’s easy to understand that if the computers in the office were running in a low power state during those 16 hours, the amount of power being used would be reduced and the amount of money being paid to the power company would be less. But just how much money are we talking about here?

To determine the savings, you first need to know how much power your computers are actually using. To track down this answer, you can visit the Uninterruptible Power Supply (UPS) Selector Sizing Application page on APC’s Web site. This Web-based application is designed to help you find a UPS that can provide enough power to support your system during a power outage. The result of the calculation is the total power measured in watts that your computer requires.

Once you know your computer's total wattage, you can then apply the standard formula that your electric company uses to calculate how much electricity an appliance uses in kilowatt-hours and then multiply that result by the current electric rate. This formula is: ((W x H) / 1000) x C where W is the wattage, H is the number of hours the device is in use, and C is the cost per kilowatt-hour.

Using one of the Pentium III systems in my office as a test, I discovered that with all of the devices inside the system, including the monitor, the wattage for this system is 340 watts. Assuming that the cost per kilowatt-hour is 6.93 cents, I then plugged these values into the formula: ((340 x 16) / 1000) x .0693 = 0.376992.

Note
The 6.93 cents cost per kilowatt-hour value was taken from a Department of Energy: Energy Information Administration report and represents the national average for electricity cost in the U.S. for the year 2001. I used this average to present a realistic calculation in the examples. Depending on what part of the country you live in, your current cost per kilowatt-hour will vary.

Thus, running this computer at full power for the 16 hours that I’m not in the office costs about 38 cents a day, which comes to a total of $1.90 during the business week. Now, if I leave the computer running at full power all weekend, it would cost me an additional $1.50, which would bring the total cost to run my computer when it’s not being used to $3.40 for the week. That’s about $177 a year

The same computer running in standby mode consumes approximately 15 percent of the wattage that it consumes when running at full power. Therefore, it will only cost $0.51 a week to run my computer when it’s not being used. That’s only about $27 a year.

So, by employing standby mode, I can save about $150 a year on electricity costs. While this might not seem like a lot of money, just multiply the values in my examples by the total number of computers in your office. Chances are that you’ll be looking at considerable savings.

Note
The Energy Star Power Management Program specifications defined by the EPA in 1994 require that Energy Star labeled computers drop down to 15 percent of the maximum power usage when in standby mode. Energy Star labeled monitors are required to drop down to 15 watts or less after 15 to 30 minutes of inactivity and down to 8 watts after 70 minutes of inactivity. Because I wasn’t separating computers and monitors in my wattage calculation, I applied the 15 percent calculation to the entire system.

Configuring a system to use standby
While Windows XP offers two power-saving states, standby and hibernation, standby is probably better suited to a desktop computer environment. This is due to the fact that in standby the system simply goes into a low power state instead of saving the contents of RAM to the hard disk and shutting down.

Standby works by gradually putting your system into a low-power state in three stages. The first stage cuts power to the monitor and hard drives, the second level cuts power to the CPU and cache, and the third level drops down to provide only enough power to support the contents of RAM. You typically revive the computer from standby with a mouse click or a keystroke.

Configuring the system to use standby is easy. To begin, access the Control Panel and double-click the Power Options icon. If you’re using the Category view, you’ll find it on the Performance And Maintenance page.

When you see the Power Options Properties dialog box, select the Home/Office Desk option from the Power Schemes drop-down list. Now, in the Settings panel, select appropriate time intervals to gradually turn off the monitor and hard disks, and to put the system into standby during times of inactivity.

For example, you might configure the system to turn off the monitor after 30 minutes, turn off the hard disks after 45 minutes, and put the system in standby after 1 hour, as shown in Figure A.



Once you set the time intervals, click OK. If you want to give the power scheme a custom name, click the Save As button and type in a new name, then click OK. If you click the Save As button, leave the default name in the text box, and click OK, you’ll get an error message.

Configuring and using manual standby
The settings that you configure on the Power Schemes tab allow you to schedule your system to automatically go into standby mode after a period of inactivity. This is a nice backup feature to have on hand when a user leaves a system inactive for long periods of time.

However, I recommend a more aggressive approach to using standby mode: manually putting the system in standby mode when a user is going to be away for an extended period of time. To configure this manual standby operation, click the Advanced tab in the Power Options Properties dialog box. In the Power Buttons panel, you’ll find two drop-down lists that allow you to configure manual standby, as shown in Figure B.



If your computer or keyboard is equipped with a Sleep button, select Standby from the When I Press The Sleep Button On My Computer drop-down list. If neither your computer nor keyboard is equipped with a Sleep button, select Standby from the When I Press The Power Button On My Computer drop-down list.

Now, whenever users leave their offices for the evening or for the weekend, they can instantly put their systems into standby by pressing either the Sleep or Power button.

Minimize security concerns
Finally, if you’re concerned about the security of a workstation being compromised when it’s in standby mode, select the Prompt For Password When Computer Resumes From Standby check box in the Options panel. This step will help prevent any unauthorized employee from gaining access to an unattended workstation that runs in standby mode for long periods of time.

 

About

Greg Shultz is a freelance Technical Writer. Previously, he has worked as Documentation Specialist in the software industry, a Technical Support Specialist in educational industry, and a Technical Journalist in the computer publishing industry.

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