External Power Supplies


External power supplies (EPS), also known as power adapters, are the small black boxes on the cord of many small or portable electronic devices such as laptop computers, tablets, modems, computer speakers, and cordless and cell phones. Power supplies convert household electric current (around 120 volts in the United States) to lower AC or DC voltages on which many electronic products operate.


The Energy Independence and Security Act (EISA) of 2007 established standards for single-voltage EPSs with output power ≤250 W, which became effective in 2008. In active mode, devices supplying greater than 51 W are required to achieve 85% efficiency. Maximum standby power consumption for all output wattages is 0.5 W.

In February 2014 , DOE published a final rule strengthening efficiency requirements for the single-voltage EPSs and expanding coverage to other EPS types such as multiple-voltage, high-power, medical, and EPSs for motorized applications and detachable battery packs. The new standards will cut adapter energy use by 30 to 85% depending on the device. According to DOE, over thirty years of sales, net consumer savings will amount to about $3.8 billion. The standards went into effect in February 2016.

A 2016 rulemaking codified provisions of the 2014 legislation that exempted certain service or spare part EPSs from efficiency standards. 


According to DOE, annual shipments number about 345 million EPS units with the new standards affecting about 75-80% of those sales. Technology options for improving the efficiency of EPSs include improved transformers, low-power integrated circuits, and low-loss transistors.

Savings through what year?: 2044
Energy saved (quads): 0.94
CO2 savings (million metric tons): 47
Net present value savings ($billion) 3% discount rate: 3.8
Net present value savings ($billion) 7% discount rate: 1.9


Federal Date States
Updated DOE Standard Due 2021
2nd Federal Standard Effective 2016
2nd Federal Standard Adopted (DOE) 2014
2013 CA Standard Effective
2012 CA Standard Adopted
2012 DC Standard Effective
2012 MD Standard Effective
Test Procedure - Last Revised - Active Mode 2011
Test Procedure - Last Revised - Standby/Off Mode 2009
2008 WA Standard Effective
2008 VT Standard Effective
2008 CT Standard Effective
2008 AZ Standard Effective
2008 MA Standard Effective
2008 OR Standard Effective
1st Federal Standard Effective 2008
1st Federal Standard Adopted (Congress) 2007
2007 DC Standard Adopted
2007 MD Standard Adopted
2007 RI Standard Effective
2006 VT Standard Adopted
2006 CA Standard Effective
EPACT Initial Federal Legislation Enacted 2005
2005 WA Standard Adopted
2005 AZ Standard Adopted
2005 MA Standard Adopted
2005 RI Standard Adopted
2005 OR Standard Adopted
2005 NY Standard Adopted
2004 CT Standard Adopted
2004 CA Standard Adopted

States not showing an effective date have an ongoing rulemaking process to determine standards.

Timeline reflects state standards from 2001 to present; federal standards from inception to present.