On an individual basis, the energy wasted by a computer that remains in the full-power "on" state is almost insignificant no matter how long it remains idle. But for a corporation with hundreds or thousands of workstations operating on a local area network (LAN) or a wide area network (WAN), that wasted energy can be quite significant, easily translating to tens of thousands of dollars in unnecessary electricity expenditures each year.
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Why Is This Important?
Despite the fact that most of the 75 million-plus personal computers (PCs) operating in office settings in North America have the capability to shift into a low-power state after a specified period of inactivity, only a small fraction of those PCs actually do so. Recent research by Lawrence Berkeley National Laboratory (LBNL) suggests that about 60 percent of computer monitors are set to go into a low-power state after some specified interval of inactivity, but fully 94 percent of computers never go to sleep, no matter how long they remain unused. One study published in 2001 estimates that annual PC energy consumption in the U.S. could be cut by about 14 billion kilowatt-hours (kWh) simply by enabling power-management features and shutting PCs down at night and on weekends.
Why do so few computer users take advantage of power-management settings? There are a variety of reasons. Individual workers may not even be aware that these settings exist, or they simply may not care about saving a small amount of energy for their employer. Some workers with long memories may recall that early attempts at PC power management resulted in long, inconvenient waits while the PC and/or monitor woke up from a low-power state. In some cases, a full reboot was necessary. Another contributor is the fact that information technology (IT) staff rarely have any incentive to implement energy-saving policies. Without a directive from management, IT staffers are unlikely to enable power-management settings when deploying new computers and are even less likely to ensure that individual employees maintain those settings.
A number of software products have been developed in recent years with the common goal of simplifying the implementation of power-management policies across large numbers of networked PCs. The amount of energy savings these products can provide depends upon the power draw of the particular computers and monitors in use (Table 1), how the PCs are being used, and the aggressiveness of the power-management settings that are implemented. The potential for savings in an office that has lots of 21-inch CRT (cathode ray tube) monitors and an existing policy that discourages employees from shutting down their PCs at night will be much greater than in an office with LCD (liquid crystal display) monitors, laptops instead of desktop computers, and an IT staff that regularly encourages employees to use their PCs' power-management capabilities and to turn PCs off at the end of the day.
The bottom line is that in organizations where most employees work at desktop computers with CRT monitors, energy savings will frequently be on the order of 200 kWh per workstation per year. If the installed cost of the software is $25 per license (a conservative assumption) and electricity costs $0.07/kWh, savings of 200 kWh/year will result in a payback of less than two years. But some of the products discussed here are available free of charge, and several have installed costs well below $20 per license.
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What Are the Options?
There are basically three approaches to harnessing energy savings via the power-management settings of networked PCs:
- Encourage employees to enable and use the existing power-management capabilities of their PCs,
- Have the IT department develop and deploy logon scripts that control power-management settings, and
- Use third-party software to establish and implement a computer power-management policy across the company LAN or WAN.
The first of these approaches is quite inexpensive: Hold a meeting or two with IT staff, energy-management staff, and executive management to explain the plan. Then send an e-mail or two telling employees how to enable power management on their PCs and exhorting them to do so, and you're done. Unfortunately, there is no way of ensuring that employees will comply with the recommended power-management policy, or any means of determining energy savings. Certainly some fraction of employees would comply with such a request, but given LBNL data indicating that only a very small percentage of PCs currently have power-management settings enabled, it's likely that this approach would be only marginally successful. In addition, any savings would likely degrade over time as PCs are replaced and users disable power-management settings.
Using logon scripts to control power-management settings can help ensure compliance and sustained savings, but scripts pose their own set of problems. Perhaps the biggest hurdle is that the IT department will rarely be motivated solely by the prospect of energy savings to create a script flexible enough to accommodate the variety of hardware, operating systems, and users found on a company LAN. Because scripts tend to be static, one-size-fits-all solutions, they are likely to either establish such lenient power-management settings (so that the settings will work for all PC users) that they capture little of the potential energy savings or alienate some employees if settings interfere with their work habits. Scripts also provide no information on the level of energy savings.
Software solutions have the potential to address all of the problems associated with the first two approaches. There are several software packages that target energy savings in PC networks (see Table 2). Each package has advantages and disadvantages, and any one of them might turn out to be the most appropriate solution for a specific organization. For example, if your workforce has diverse schedules and computer usage patterns, one of the products that offers group-specific power-management settings may be the most appropriate choice.
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How to Make the Best Choice
Choose software that allows you to estimate energy savings and payback. You need to collect information about all of the PCs on the network in order to determine what the best power-management strategy is before you begin an implementation. Some software packages can track the time each computer spends in each operating mode—active, low power, hibernate, or off—and use these data to estimate the energy savings that would result from a range of policies before the network administrator implements any one of them. The reported data also help the administrator accurately determine energy savings after a given policy has been implemented.
Choose software that permits different settings for different users. A one-size-fits-all approach to PC power management will rarely be successful because employees have differing work schedules and use their computers in different ways. Ignoring this fact and trying to implement a policy that works for everyone will either be so lenient that it leaves a lot of potential energy savings on the table, or it will be unduly restrictive for some users, negatively affecting their productivity and leaving them frustrated.
Some power-management software packages allow the network administrator to define multiple groups of workstations and to establish different power-management settings for each group. For example, one group might consist of workers who are at their PCs continuously on a regular 9-to-5 schedule. Another group could include factory workers who need to intermittently monitor a production process that runs three shifts per day, and a third group could include staff who monitor real-time data on PC screens but only infrequently use the keyboard or mouse. And if the organization wishes to allow it, another profile could be established for specific employees who would be permitted to opt out of the PC energy-savings program.
Choose software that identifies the hardware and operating system used at each workstation. This information is critical to determining groups of similar machines and identifying machines for which power management is inappropriate. For example, machines running the Windows NT operating system have no low-power modes, and, for some older machines, enabling power management may lead to unacceptable delays when a user needs to "wake up" a computer from a low-power state.
Choose software that can shut computers down. In addition to controlling the amount of idle time after which PCs will enter a low-power state, some software packages can implement a turn-off schedule. In most cases, the shutdown procedure is terminated if any application running on a computer offers an "unsaved data" prompt. The shutdown feature can be used even with PCs running operating systems that are incompatible with power management (such as Windows NT), to ensure that those PCs are not left on overnight or over the weekend.
Consider "wake-on-LAN" capability. This feature can bring a networked computer into the active state from the off state. Wake-on-LAN capability is built into most newer computers, and some software takes advantage of it. Because wake-on-LAN gives network administrators access to any computer at any time, it overcomes one of the most common obstacles to using power-management software: the need to install software patches and updates on networked computers when they are not in use.
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