Wall warts, power bricks, and little black boxes are about to become more energy efficient

Posted on February 2, 2016 by
Marianne DiMascio

crowded power stripAs of this month, the little black boxes attached to many small electronic devices will cost less to run due to Department of Energy (DOE) standards that will reduce the amount of energy they waste. Though the energy use per unit is small, the combined energy use from the more than 1 BILLION external power supplies (EPSs) in use in the United States adds up. And the number of black boxes keeps growing—DOE estimates that about 340 million external power supplies are currently shipped each year. That’s at least two additional EPSs every year for each household in the United States, adding to the 5-10 power supplies the average American home already has.

The efficiency standards, which will reduce EPS energy use by about 33%, affect power supplies manufactured or imported as of February 10. Once all power supplies comply, consumers will save $300 million annually. The standards will also reduce energy use nationally by 93 billion kilowatt hours over the next 30 years and decrease CO2 emissions by 47 million metric tons, equivalent to the annual emissions from nearly 10 million cars. Not bad results from making those little wall warts a bit more energy efficient.

External power supplies usually convert electricity from 110 volt alternating current (AC) at the outlet to low voltage direct current (DC) suitable for devices such as laptops, mobile and cordless phones, Bluetooth headsets, and power drills. EPSs consume electricity in active mode, when the device powered by the power supply is in use; and “no-load” mode, when the EPS is plugged in to the wall with no device attached. In both cases, inefficient power supplies waste energy, as evidenced by the heat emanating from them when plugged in.   

Congress set initial standards for one type of power supply (Class A) in 2007. The 2014 rulemaking which developed the standards taking effect this month extended the scope to a broader range of EPS products and increased the efficiency levels. The new efficiency levels vary according to output power, voltage, active or no-load mode, and type of conversion (AC-DC, AC-AC). Certain EPSs used for medical devices and replacement parts are exempt from the standards and some safety and security equipment EPS are exempt from the no-load requirements.

Legislation pending as part of the energy bill under consideration this week would exempt power supplies for solid state lighting products (e.g. LEDs). For example, LEDs used for office lighting have a power supply that meets the definition Congress wrote in 2007, but these products had not yet been developed at that time and cannot be tested to determine compliance with the new standard. The pending bill would exempt them from the new standards but still permit DOE to design future standards specific for solid state lighting power supplies if warranted.

Here's to building a more energy efficient future, one power brick at a time, or, in this case, 340 million bricks per year!