June 16, 2003
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Simple Symbols that Save Energy
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If you are reading this article on your computer screen, stop for a moment and check the controls on your monitor or computer. Chances are you will see one of these symbols, or something like them, meaning "this is the power switch."

If your computer has some type of "sleep" or power-saving mode, or perhaps more than one low-power mode, it may have one of these:


Or it may use some other symbol altogether. Before you started reading this article, did you know what these symbols mean? And do you know whether your computer and your screen are using energy in full-power mode, saving energy, "off" (but still wasting standby power), or truly off?

A project now underway at Lawrence Berkeley National Laboratory's Environmental Energy Technologies Division aims to clear up some of the confusion. It could save large amounts of energy as well -- worth perhaps hundreds of millions of dollars per year. Berkeley Lab's Bruce Nordman, the project manager, and Alan Meier are leading the effort.

An Energy Star success

The low-power or "sleep" mode is one of the big successes of the Energy Star program, run by the U.S. Environmental Protection Agency and the Department of Energy. Energy Star urged manufacturers to create these modes in nearly every type of office equipment, including PCs, monitor, copiers, fax machines, printers, and other tools of the modern office. After a pre-set amount of time without being used, these machines automatically move into a power-saving mode.

However, research by Berkeley Lab scientists shows that many devices with energy-saving modes aren't saving energy. "They may not be configured correctly," says Nordman. "The energy-saving feature may have been disabled by the user or by hardware and software conflicts. We have found in surveys that energy-saving features have been disabled in the majority of PCs. The feature is operational in a higher percent of copiers, printers and monitors, but the rate is highly variable."

"Another problem," he continues, "is that existing power management controls are confusing. The energy-saving mode can go by a dozen different names, depending on the make of the equipment. It can be represented by many different symbols; controls for low-power mode may be absent or hidden; even the on and off states are represented by different symbols. The result is a lot of wasted energy. Users may also gain a poor impression of energy efficiency and the product's quality."

A Berkeley Lab study published in 2000 by Kaoru Kawamoto, Alan Meier, and colleagues suggests that increased enabling of power management features in these devices could save thousands of gigawatt-hours (a gigawatt is a billion watts) per year. The savings gap from disabled power management is about $1.3 billion per year; so increasing the number of devices with power management enabled could eventually save billions of dollars in the U.S. alone.

These savings are likely to grow for a number of reasons. Sleep modes are expected to use even less energy in the future, which will increase the difference in power use between the active and sleep modes. There will be more types of devices with sleep modes, increasing stocks of devices with these modes, and they will be used more widely.

With funding from the California Energy Commission's Public Interest Energy Research program, Nordman studied the power management interface on office equipment. He worked closely with an industry advisory committee that includes representatives of such companies as Hewlett-Packard, Intel, IBM, Microsoft, and Sony, as well as the Energy Star program. Improving the user interface helps industry improve the usability and friendliness of electronic office equipment, reduces customer service requests, and may increase product sales.

"We determined that from device to device, many terms, symbols, and indicators are used differently or are not clear to begin with. On many devices, the controls are difficult or impossible for the average user to find," says Nordman. "Many PCs don't indicate when the equipment is in a low-power mode, so users are unaware that the PC can 'sleep.' Users can't always tell whether PC power management is working, and many don't realize that PC power management is distinct from monitor power management."

An important example of confusion is the standby problem. The term "standby" can mean anything from a fully on state, a low power mode, or the amount of power used by a device when it is functionally off. There is no standard usage for this word, and no symbol that is recognized to mean "standby."

Developing an interface standard

"The solution to the problem of fully realizing the energy benefit of the low-power mode may lie in creating a widely accepted, voluntary interface standard for power control that users can clearly understand -- and that they see in common use on all kinds and makes of office equipment and consumer electronics," says Nordman. "We have created and tested a draft interface standard, and we are now working with international standards organizations on its adoption."

For a power management interface standard to be effective, it needs three things: the standard should use a common set of symbols for on, off, and sleep; indicator lights for these three states should use the same colors, no matter what the type of equipment; and the same terminology should be adopted for these states, especially the low-power state.

Currently, computer users encounter a tremendous range of names indicating the low-power or energy-saving mode. They include, for example, Sleep, Energy-Saver, Power-Save, Idle, Suspend, Doze, Standby, and Low Power. And, as the symbols at the start of this article show, neither the low-power mode nor the power switch is indicated with uniform symbols.

Nordman developed a draft interface standard and tested it in focus groups held at Berkeley Lab, the University of California at Berkeley, and Cornell University, to determine how well users understood various types of symbols, indicators, and equipment states (like "sleep" versus "off").

The draft standard recommends, among other things, that there be only three terms for states: on, off, and sleep. It recommends standard colors for the three states and suggests using a moon-shaped symbol for the sleep state.

The standard also covers "dynamic behavior," or how devices behave over time and in response to input or activity. For example, the standard specifies using "power up" to mean turn on or wake up, "power down" for turn off or go to sleep -- with flashing green on the power indicator for powering up and flashing amber for powering down.

In September 2002, following months of presentations of the work at conferences and to the project's advisory committee, the Institute of Electrical and Electronic Engineers (IEEE) created a working group (#1621) for a "Standard for User Interface Elements in Power Control of Electronic Devices Employed in Office/Consumer Environments." This group is now working to adapt the User Interface Standard content into an IEEE standard.

A draft of the proposed standards is accessible online (see Additional information, below). It includes a discussion of "power metaphors" and suggests the uses of specific symbols and terminology.

Nordman is interested in inviting manufacturers and other stakeholders to provide comments on the standard. They can reach him through the project's web site (see Additional information, below). "In the long term, we hope to work with international standards organizations to implement a voluntary standard based on this research," says Nordman.

Future steps

Nordman believes that there are other ways to save energy through improved controls. "We need to explore areas for user interface improvement and standardization related to energy consumption such as lighting, space conditioning, and real-time pricing," he says. "Research has shown that thermostat controls are poorly understood by many users. Making these devices easier to use will substantially increase the energy savings they deliver. Considering human interface elements in future controls of all energy-using devices can increase the effectiveness of energy-saving controls."

Additional information