Companies are anxious to reduce power usage these days, both to save cash on energy bills and to reduce their environmental impact. One area that's ripe for power savings is the desktop. At companies across the globe, end-users leave their computers and monitors on day and night for any number of reasons, be it for late-night backups and patching or ensuring they can get cracking the moment they sit down at their desks each morning.

These conveniences come at an overlooked price: Keeping a PC running 24/7 can cost as much as £230 per year, depending on the type of computer and monitor, as well as energy rates in your region. Shutting down a PC for 16 hours or so per day can cut those costs by 66 percent. That translates to potential savings of more than £73,000 if you have 500 machines.

Rather than relying on end-users to power down their machines and monitors each night, then reboot them in the morning, organisations are increasingly turning to power management offerings, products capable of powering machines on and off at predetermined times to ensure that they're awake when it's time for work, backups, or patches. Otherwise, they'll be asleep so as not to waste energy and money.

I had an opportunity to test out three power management software systems aimed at the enterprise desktop market, from vendors Autonomic Software, BigFix, and Symantec. Notably, all three software products are part of suites intended to provide a great many more PC management functions beyond control over power usage, such as remote desktop support, configuration and patch management, vulnerability assessment, and endpoint protection.

Windows XP, Vista, and Windows 7 already come equipped with tools for putting a machine in a low-power state (ranging from standby and sleep to complete shutdown) at a set period of time or a predetermined amount of inactivity. Why, then, would an organisation invest in a separate power-management tool? The reason: These tools offer several useful features not available in Windows. For example, they can locate systems with hibernation disabled and re-enable it. They can shut down applications and save files before powering down the system. Admins can set different durations of inactive time before hibernation is triggered; for example, to prompt a machine to sleep after only a couple of minutes of inactivity during evenings and weekends, but not until, say, a half-hour during the work day. Admins also can use the tools to automatically restart PCs at predetermined times, such as in the middle of the night for software updates and patches, or in the morning, shortly before the users arrive.

Enter power mode

There are several modes of power saving, depending on the OS, motherboard, monitor, and power strip or UPS. When Windows powers down a monitor, for instance, power usage on the monitor doesn't drop to zero; rather, it enters a power-saving mode defined by the manufacturer, generally using less than 3 watts. Even if the monitor is turned off, its power supply may be using some electricity. This is true of PCs as well; even when shut down, they still draw some power to keep the clock running and enable wake-on-LAN and other features.

Notably, a new type of power strip/UPS from APC can eliminate much of this wasted power. The P7GT power strip and the BE750G Back-UPS model both power off up to three peripherals when the attached computer shuts down or goes into hibernate mode. This means that the power supplies for the peripherals are completely powered off, rather than using standby power or full power when the computer is shut off.

Windows XP, Vista, and Windows 7 offer three degrees of power saving: sleep (called standby in XP), hibernate, and shut down. Sleep saves system state to RAM in order to resume very quickly, while hibernate saves state to disk, taking longer to resume but allowing even RAM to be powered down. Standby mode in XP is essentially the same as sleep mode in Vista and Windows 7, except that standby saves system state only in RAM whereas Vista and Windows 7 also save it to disk as a safety measure.

Rather than focusing on the technical differences of these modes, it is useful to examine the recovery times to full operational. Booting from shutdown takes the longest, up to several minutes depending on the system, how many drivers load, how long it's been since a clean install, and other factors. Restoring from hibernate is generally quicker, and restoring from sleep is quickest of all, generally requiring only a few seconds.

Particularly during the day, shutting down a PC is not economical. If you power down a user's PC while he or she is at lunch, the 3 cents of electricity you save will be wiped out by the five minutes the user wastes waiting for the PC to boot up.

Go, go power savers

All three software products in my test help admins locate PCs that aren't using power management; moreover, they all enable policy-based enforcement of power-saving settings by remotely deploying agents to each PC on the network. Additionally, they offer considerably more flexibility than trying to use Group Policy in Active Directory, plus they deliver a wealth of other features unrelated to power management, although at additional cost.

The offerings aren't all created equal, however. Autonomic delivers the easiest and most granular power policy management, but the Autonomic management platform supports only Windows clients. BigFix approaches Autonomic in power management features, while being able to manage a very wide array of client and server platforms. Symantec boasts the broadest overall management platform, integrating many different products into a single management console and providing a limited but free power management capability along with the rest of the platform.