External Power Supplies


External power supplies (EPSs), 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, 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 current standards for EPSs took effect in 2016 and include minimum efficiency requirements for active mode and maximum power limits in no-load mode. 

In 2023, DOE proposed updated standards for EPSs, which would result in energy savings of around 3%. 


As of 2023, annual shipments of EPSs were about 730 million. Technology options for improving the efficiency of EPSs include improved transformers with lower losses and switched-mode power supplies.

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.