External Power Adapters

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Portable devices are designed to be as small and light as possible. ENERGY STAR recognizes two classes of external power adapters: battery chargers and external power supplies.

An excellent example of this is a cell phone. It is designed to fit in a pocket but still provide the maximum number of services. One way this is done is to power the cell phone from a battery that is reenergized by a battery charger. This removes the power supply from the unit and places it in an external adapter. Other non-portable devices, such as desktop speakers, use a similar arrangement. In this case, by moving the bulky power supply module out of the speaker casing, space is saved on the desktop.

According to the ENERGY STAR Web site, 1.5 billion power adapters are in use throughout the United States. "The total electricity flowing through all types of power supplies is about 300 billion kWh/year, or 11% of the national electric bill." See http://www.energystar.gov/index.cfm? c=ext_power_supplies.power_supplies_consumers

The amount of energy consumed by these many small adapters is so large that ENERGY STAR has a special program to improve their performance. This program uses its own ENERGY STAR logo. Adapters with the ENERGY STAR adapter logo are usually 30 percent more efficient and smaller than less efficient units. To qualify for an ENERGY STAR certification, the external adapter must meet efficiency thresholds when it is providing power to the device and when it is idle.


It is a rare business that does not have printers sprinkled throughout the office. Usually these are networked and shared laser printers, although occasionally a desktop may have an inkjet printer for convenience or to make

Figure 5-1

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