External Power Supplies

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THE PRODUCT:

External power supplies are the small black boxes attached to the cord of many small or portable electronic devices such as cordless phones, cell phones, computer speakers, telephone answering machines, and laptop computers. Power supplies convert AC supply voltage (around 120 volts in the United States) to lower AC or DC voltages on which many electronic products operate.

POTENTIAL STANDARD:

The Energy Independence and Security Act (EISA) of 2007 established the current standards for single-voltage EPSs with output power ≤250 W (Class A EPSs), which became effective in 2008. The standards include an active mode efficiency requirement based on nameplate output power, with devices supplying greater than 51 W required to achieve 85% efficiency; and a maximum standby (no-load) power consumption for all output wattages of 0.5 W. In May 2010, DOE published a final determination concluding that standards for non-Class A EPSs would be technically feasible and economically justified. Non-Class A EPSs include multiple-voltage EPSs, high-power EPSs, medical EPSs, and EPSs for motorized applications and detachable battery packs. DOE is currently conducting a rulemaking to amend the standards for Class A EPSs and to set standards for non-Class A EPSs.

The ASAP/ACEEE report, The Efficiency Boom, analyzed standard levels based on DOE’s September 2010 preliminary analysis that represent the minimum life-cycle cost. On average, the standards levels represent energy savings of about 50% relative to the current standard. These cost-effective standards could achieve annual energy savings in 2035 of about 5TWh and net present value savings of about $2.3 billion. DOE published a proposed rule in March 2012.

The statutory deadline for the final rule was July 1, 2011. DOE missed the deadline.

KEY FACTS:

Active mode efficiency is measured as the ratio of output power to input power. EPSs with higher nameplate output power tend to have higher active mode efficiency while EPSs with lower nameplate output power tend to have lower no-load power consumption. Technology options for improving the efficiency of EPSs include improved transformers, low-power integrated circuits,and  low-loss transistors.

Note: The federal standard has a narrower scope than most state standards because it does not apply to certain power supplies used with some products that include batteries. Federal preemption only applies to those products subject to federal standards, so states will continue to enforce standards with respect to some external power supplies.