The Difference Between Efficiency Level VI and V

International Efficiency Marking Protocol is a system that allows manufacturers to designate the efficiency performance of external power supplies. These designations are identified with a Roman numeral system: I, II, III, IV, VI, V and VI.

Historical perspective

In the 1990s, external power supplies could have efficiencies as low as 50 percent and still draw power when the appliance was turned off or even disconnected from the power supply. (This is what’s known as “no-load” power consumption.)

To remedy this problem, the U.S. Environmental Protection Agency instituted voluntary energy efficiency/pollution reduction measures for power supplies, which would eventually evolve into the Energy Star program.

Energy Star Program

The first mandatory efficiency and no-load power draw regulations – created by the California Energy Commission – were implemented in 2004. In 2006, Energy Star unveiled a protocol to unite global efficiency efforts. Over the years, other countries would adopt the Roman numeral marking system established by Energy Star.

In 2008, Energy Star began letting manufacturers use their seal provided the manufacturers’ power supplies reached Level IV standards.

Level V standards went into effect in the USA in 2010 and Europe the following year. In 2014, the U.S Department of Energy introduced more rigid Level VI standards, which went into effect in 2016.

Efficiency Levels

Efficiency levels are defined by no-load power consumption and the average efficiency tested at 25%, 50%, 75% and 100% load levels.  The charts below illustrate the Minimum Average Efficiency in Active Mode for basic voltage and low voltage.


This last chart shows a comparison of the Maximum Power in No Load Mode for the USA versus Europe for No Load and Average Efficiency.

If you would like more information on these efficiency standards, please view our external power supply presentation.

MEGA Electronics power supplies meet the efficiency standards for countries around the world. We offer a one-stop solution to your global power supply sourcing needs.  Please call us today at 732-249-2656 to speak with one of our engineering experts or send us an email to


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