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Power Management

Special thanks to Paul Cyr for help with this section

Overview

Both Mac OS X and Windows XP offer a variety of features to reduce power consumption and save energy. Power consumption is important because it can prolong the life of your hardware, as well as reduce electricity costs. For laptop owners, power consumption helps to prolong battery life.

Both operating systems support putting the computer to sleep and waking on network activity. They also support uninterruptible power supplies (UPS) and can display estimated capacity. In the event of a power loss, the UPS kicks in to supply the computer with power for enough time to shut down. Some can even supply the computer with a few hours of power.

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Mac OS X

Mac OS X's Energy Saver pane of System Preferences contains two tabs: Sleep and Options.

The "Sleep" tab allows you to place the computer, display, and hard disk into a low power mode to conserve energy. Drag the sliders to configure when the computer/display enter sleep mode. Cleverly, OS X will notify you if your display is set to sleep sooner than when your screensaver would activate (which would negate the point of having a screensaver).

The "Options" tab contains more advanced power settings for your computer, such as waking from sleep for network administration; restarting after a power failure; or adjusting CPU performance.

Clicking the "Schedule" button in the lower right-hand corner of the preference pane lets you schedule automatic start up and shut down times for your computer.

Turn your computer off and on automatically

If your computer has more than one power source (power adapter, battery, or UPS), you will see a "Settings for" menu that will allow you to customize your energy settings (sleep, CPU performance, etc.) for each source. This lets you specify, for example, different energy settings for when your laptop is plugged into its power adapter versus when it is running off its battery.

Customize your energy settings for each power source

If your computer has a data connection to a UPS, the Settings For menu will display a "UPS" item. Choosing this option allows you to configure power options specifically for your UPS device.

At the bottom of the window is a checkbox labeled "Show UPS status in the menu bar". If this is checked, a small icon will appear on the right end of the menu bar at the top of the screen indicating the amount of charge remaining in the UPS (this menu item will combine with the battery menu item if both are set to display).

This laptop's battery has 96% of its charge remaining, while the UPS is at 100%

Laptops get an additional menu option in the Energy Saver panel: Optimize Energy Settings. These are energy profiles you can quickly switch between depending on the circumstance:

Optimize Energy Settings menu

Windows XP

Energy settings for XP are found in the Control Panel under "Power Options."

Under the "Power Schemes" tab, the user can select, create, modify, or delete power schemes. The following default schemes are available:

• Home/Office
• Portable/Laptop
• Presentation
• Always On
• Minimal Power Management
• Max Battery

Strangely, "Portable/Laptop" is available on all computers — including desktops.

You can create and save multiple power schemes.

Create multiple power schemes for different situations

Users can set when to turn off the monitor, hard disks, or standby/hibernate the system. These options are pre-defined, however; the user cannot set custom amounts of time for these events.

If you have a laptop, you can set separate times for battery and AC power for turning off the monitor, hard disks, system standby, and hibernation.

The Advanced tab gives the user options on whether to show the power icon in the taskbar (useful to show battery life), prompt for a password when the computer resumes from standby (although it only does so if fast user switching is disabled — otherwise, it displays the Welcome screen), and what to do when power buttons on the computer or keyboard are pressed (Shutdown, Standby, Restart, Hibernate, Do Nothing).

Configure advanced power options for your XP machine

The "Hibernate" tab allows the user to enable XP's zero-power mode, called "hibernation." Hibernating will save the state of everything currently open, and then shut down the computer. When returning from hibernation, XP will return to the state it was in previously, with all open windows and programs available as they were. Hibernate functions essentially the same way as sleep or standby; the difference is that it fully shuts the computer down instead of just putting it into a low-power state. Since the computer is literally turned off in this state, you can unplug it, move it to another location, and turn it back on without having to boot up again.

The UPS (Uninterruptible Power Supply) tab allows you to monitor your UPS status and configure its settings. XP can be set up to communicate and execute commands with the UPS.

Click "Configure" (if you have a serial connection to the UPS) to set up these options. You can configure XP to notify the user, execute an application, or shut down the computer when the UPS switches to battery power or the internal battery is getting low. You can even set up a convenient optional delay, so if the UPS kicks in for only a few seconds and then returns to AC power, your configured actions will not run.

The following table lists the keyboard shortcuts for power control on each operating system:

	Mac OS X	Windows XP
Shut Down (prompts to save documents)	Control-Option--Eject	Power key, or press Windows key-U-U
Restart (prompts to save documents)	Control--Eject	Windows key-U-R
Sleep	-Option-Eject	Windows key-U-S
Hibernate	Not Supported	Windows key-U-Shift+H
Dialog to choose Shut down, Restart, Sleep, or Cancel	Control-Eject	Alt-F4 or Power key (if you modify that key)

Conclusion

Windows XP surpasses Mac OS X here, with its superior UPS power options and ability to hibernate in addition to sleep. Mac OS X, however, does directly support scheduled start up and shut down times, which XP users will need to configure through their computer's BIOS (if it is supported) — not nearly as elegant. These issues start to cross over into hardware, however, so this is out of the scope of this site.

Mac OS X

• Flexible options for when to turn off monitors, hard disks, and the computer
• Automatic scheduled start up/shut down (although this seems to be a hardware issue)
• Can't create multiple custom power schemes
• No support for hibernation
• Setting the amount of delay before hard disks are turned off can only be done through the command line

Windows XP

• Can create multiple custom power schemes
• Zero-power hibernate mode saves the system state (including open applications and files), then powers down the computer, thereby preserving the computer's state indefinitely
• Superior UPS support. Invoke Hibernate, Shutdown, or any user defined tasks automatically when UPS power is low
• Can set amount of delay before hard disks are turned off
• Restrictive delay options for turning off monitors, hard disks, and the computer
• No scheduled start up or shut down (although this seems to be a hardware issue)
• Restarting after a power failure is usually available through the BIOS (again, this seems to be a hardware issue)

Mac OS X: 7
Windows XP: 8

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