Power management technology was developed for personal computers (PCs) and monitors to reduce energy consumption when they are not in active use. In addition to the environmental benefits of reduced energy consumption, power management can improve equipment reliability by reducing waste heat. First developed for laptop computers, power management is now common in desktop PCs. As of early 1996, the EPA estimates that upwards of 70% of all new PCs and nearly 100% of all PC monitors sold have power management capability.

Power management interacts with every part of the computer-the operating system, software, CPU, monitor, network cards, video cards, peripherals, etc. Because of this there is the potential for unexpected interactions between power management and the computing environment. These problems can reduce the positive environmental impact of power management. Computer manufacturers have addressed this problem by making power management more flexible and more compatible with current PC networks. As the technology has matured, power management has emerged as an effective tool for saving energy.

This guide has been developed to aid computer professionals in enabling power management, to help to achieve maximum energy savings with a minimum of problems. The scope of the guide is primarily personal computers and monitors, though one type of computer workstation is also included. This guide is divided into four major chapters; chapters 1 and 2 provide an introduction and background to power management, and chapters 4 and 5 are designed to help computer support personnel implement energy-efficient practices in the office.

Power management can only save energy if it is enabled and working properly. Unfortunately, a general lack of information about power management has meant that many computers with power management capability are not saving energy-because they were never enabled, because they were actively disabled, or because of interference from the various elements of the computer system or network. To overcome these problems, computer professionals must become better informed about power management. This guide was developed to explain:

• the benefits of power management
• the fundamentals of how power management works
• integrating power-managed computers into a network environment
• avoiding negative interactions between power management and computer systems
• educating computer users about office energy use

The chapters need not be read in order, but doing so will lead to the most complete understanding of power management.

• Chapter 2 introduces power management, its benefits to users, and the Environmental Protection Agency's (EPA) ENERGY STAR program.
• Chapter 3 provides an in-depth explanation of how computer power management works, addressing the relationship among the PC, the monitor, the BIOS, software, etc. While is not necessary to have read Chapter 3 to understand Chapters 4 and 5, it is helpful to be familiar with the basics of power management so readers are encouraged to review it.
• Chapter 4 covers optimum use of power management, enabling computers and monitors for power management, educating computer users, and also provides solutions for potential problems with power management. Details for specific systems are in Appendix D.
• Chapter 5 provides guidelines for purchasing power-managed computers and monitors.
• Chapter 6 discusses possible future directions for PC power management.
• Chapter 7 provides references and resources for further information about power management.

Without power management, U.S. businesses could spend $1.75 billion on energy to power PCs and monitors by the year 2000. Ironically, much of this energy would be wasted: research shows that most of the time personal computers are on they are not actively in use--and an estimated 20% are left running at night and on weekends. A typical PC is actively used 4 hours each work day and idle for another 5.5 hours. The energy saving potential from reducing PC power consumption is enormous, from turning off those that don't need to be on, and from power managing PCs when they are on, but idle. Approximately 13 million PCs are sold each year, with most going to offices. Approximately 90% of those in offices are connected to networks.

Since the monitor usually consumes at least twice as much electricity as the CPU, turning off monitors is a big step in achieving significant energy savings. If just an additional 10% of monitors in the U.S. were shut off at night and on weekends, about $140 million of electricity could be saved each year (about 1.7 billion kWh; see Appendix E for assumptions).

First appearing in the laptop computer market, power management rapidly expanded into desktop PCs after 1993, and continues to evolve rapidly. However, despite the success in the manufacture and marketing of PCs and monitors capable of power management, studies show that most systems are not enabled, or are enabled but not operating to save energy. The primary reason for this guide is to realize the latent energy and dollar savings of these machines. The guide addresses power management in the installed base of desktop computers, as well as in new PCs and monitors, and one type of workstation. Power management has only recently been incorporated into high-end workstations, but in the future we should expect the technology to be built-in to more workstations and some servers.

The Environmental Protection Agency's voluntary ENERGY STAR program was originally developed to promote the use of power management technology in computer equipment. The EPA forms partnerships with manufacturers to identify equipment that consumes less than 30 watts of power in low-power mode (30 W for the computer and 30 W for the monitor). Such computers earn the right to bear the EPA's ENERGY STAR logo, though the EPA does not endorse any specific products or services. The EPA publishes a list of ENERGY STAR equipment, which is updated monthly. A sample of the resource listings is in Appendix B, along with information on how to interpret the product tables. The full, current listings are available on the ENERGY STAR web pages at http://www.epa.gov/energystar.html. As the PC industry evolves at a rapid pace, check the EPA web pages regularly for new products and information.

By the year 2000, ENERGY STAR computers and monitors are expected to collectively save 330 million dollars worth of electricity per year-several billion kWh-with the potential savings even higher. Appendix B summarizes the current provisions of the ENERGY STAR Office Equipment Program.

Continue to Chapter 2: What is Power Management?

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