Understanding Efficiency Standards For External Power Supplies

July 17, 2012
CUI's Jeff Schnabel summarizes efficiency standards for external power supplies mandated by agencies around the world.

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The global regulatory environment surrounding the legislation of external power supply efficiency and no-load power draw has rapidly evolved since the California Energy Commission (CEC) implemented the first mandatory standard in 2004. Mandating higher average efficiencies in external power supplies has had a real impact on global power consumption.

However, the reduced draw on the power grid brings challenges and uncertainties to the electronics industry as it tries to keep up with this dynamic regulatory environment. OEMs who design external power supplies into their products must continue to monitor the latest regulations to ensure they comply in each region their product is sold. The goal of this article is to provide an up-to-date summary of the most current regulations worldwide (Table 1).

Table Of Contents

  1. Chronology
  2. Test Methods
  3. Current Regulatory Environment
  4. Exemptions
  5. Moving Forward
  6. References


In the early 1990s, it was estimated that there were more than 1 billion external power supplies active in the United States alone. The efficiency of these power supplies, mainly utilizing linear technology, could be as low as 50% and still draw power when the application was turned off or not even connected to the power supply (referred to as “no-load” condition).

Experts calculated that without efforts to increase efficiencies and reduce “no-load” power consumption, external power supplies would account for around 30% of total energy consumption in less than 20 years. As early as 1992, the U.S. Environmental Protection Agency started a voluntary program to promote energy efficiency and reduce pollution that eventually became the Energy Star program. However, the first mandatory regulation dictating efficiency and no-load power draw minimums wasn’t put in place until 2004. The following section traces the path from the CEC’s 2004 regulation up to the current standards that are in place today.

December 2004

California, having a long history of adopting energy standards before the rest of world, was the first to pass legislation for external power supplies. The CEC passed legislation that defined a schedule for the implementation of its Tier 1 standards in July 2006 and Tier 2 standards in January 2008. This move by California forced manufacturers to quickly adopt higher-efficiency power supplies, or forego sales in California and miss out on other regions that would soon follow.

January 2005

China implemented the voluntary China Energy Conservation Program (CECP), which allowed Chinese factories to market their power supplies as high-efficiency products. Meanwhile, Energy Star implemented its voluntary program for efficiency levels known as Tier 1.

July 2005

Europe approved Directive 2005/32/EC, establishing a framework for setting ecodesign requirements for energy-consuming products. While the directive targeted products that use energy, it did not provide specific targets for external power supplies at the time.

January 2006

Recognizing that California, China, and Australia were quickly defining their own standards, Energy Star defined the International Efficiency Marking Protocol to minimize confusion between regions and their similar standards. The defined markings set minimum efficiency and no-load levels for external power supplies:

  • Level I: Power supply does not meet any of the standards defined
  • Level II: Power supply meets minimum efficiencies that were set by China in November 2005
  • Level III: Power supply meets Energy Star Tier 1, CEC Tier 1, and Australian MEPS standards
  • Level IV: Power supply meets CEC Tier 2 and the Australian MEPS High Efficiency category
  • Level V: Future Energy Star Tier II Level that was TBD at the time
  • Level VI and Level VII: Reserved for future levels

April 2006

Australia implemented its Minimum Efficiency Performance Standard (MEPS).

July 2006

California implemented CEC Tier 1. Following the International Efficiency Marking Protocol, it’s commonly called the Level III efficiency standard.

December 2007

The U.S. Congress passed the Energy Independence and Security Act of 2007 (EISA 2007), originally called the Clean Energy Act. This act basically mirrored the legislation from California with a release date and harmonized requirements of California’s CEC Tier 2 legislation to be implemented in July 2008.

April 2008

Australia updated its MEPS program to include a voluntary “High Efficiency” category (equivalent to CEC Tier II and EISA 2007).

July 2008

EISA 2007 and CEC Tier 2 were implemented with the designations defined by the International Efficiency Marking Protocol as the Roman numeral IV surrounded by a circle to be clearly represented on each power supply’s label.

November 2008

Energy Star harmonized its specifications with EISA 2007 and CEC Level IV and announced that manufacturers may use the Energy Star logo on their products and datasheets if they met Level IV requirements.

April 2009

Europe enacted ErP Directive 2009/125/EC (Energy Related Products) with scheduled stages of implementation for efficiency and no-load requirements equivalent to Level IV and Level V standards. The schedule defined that the EU would harmonize with Level IV efficiency standards by April 2010 and Level V efficiency standards by April 2011.

April 2010

Europe implemented Phase I of its ErP Directive equivalent to Level IV Standards.

December 2010

Energy Star removed the external power supply category, as it felt the marking should be part of the final product type. After the end of 2010, compliant external power supply part numbers would no longer be listed on the Energy Star Web site, and the Energy Star logo had to be removed from power supply datasheets.

April 2011

EISA 2007, CEC Tier 3, and ErP Phase 2 took effect in full harmony of their standards leaving us with what is now simply known as the “Level V Efficiency” standard, designated by the Roman numeral V surrounded by a circle.

April 2012

NRCan (Natural Resources Canada) implemented its Tier 1 standards in harmony with Efficiency Level IV Requirements. The agency then required the verification of Tier 1 standards to be certified by a third-party agency approved by NRCan.

Test Methods

The IEC has published the internationally approved test method for determining efficiency as AS/NZS 4665 Part 1 and Part 2. The approach taken to establish efficiency level is to measure the input and output power at four defined points: 25%, 50%, 75%, and 100% of rated power output. Data for all four points are separately reported as well as an arithmetic average active efficiency across all four points.

Current Regulatory Environment

The preceding timeline demonstrates just how dynamic the regulatory environment has been over the past eight years. As different countries and regions enact stricter requirements and move from voluntary to mandatory programs, it has become vital that OEMs continually track the most recent developments to ensure compliance and avoid costly delays or fines.

While many countries are establishing voluntary programs harmonized to the international efficiency marking protocol system first established by Energy Star, the following countries and regions now have regulations in place mandating that all external power supplies shipped across their borders meet the specified efficiency level (Table 2).

Today, Level V will meet or exceed the requirements of any governing body around the globe. Power supply manufacturers indicate compliance by placing a Roman numeral V on the power supply label.

Although the European Union is currently the only governing body to enforce compliance with the Level V standard, most external power supply manufacturers are adjusting their product portfolios to meet these requirements. The adjustments are a direct response to the needs of OEMs to have a universal power supply platform for their products that ship globally.


Not all external power supplies are treated the same, and exemptions exist in both the United States and the European Union. In the U.S., Congress has written provisions into section 301 of EISA 2007 that exclude some types of external power supplies. These devices:

  • Require federal Food and Drug Administration listing and approval as a medical device in accordance with section 513 of the Federal Food, Drug, and Cosmetic Act (21 U.S.C. 360c)
  • Power the charger of a detachable battery pack or charge the battery of a product that is fully or primarily motor-operated.
  • Are made available as a service part or spare part by the manufacturer of an end-product that was produced before July 1, 2008 for which the external power supply was the primary load; power supplies used for this purpose can be manufactured after July 1, 2008

The European Union has instituted similar exemptions to the United States. External power supplies for medical devices, battery chargers, and service products are exempt. In addition, an exemption exists for low-voltage EPS devices. Low-voltage external power supply means a unit with a nameplate output voltage of less than 6 V and a nameplate output current greater than or equal to 550 mA.

Moving Forward

As rapidly as regulations have changed over the past eight years, they will continue to evolve as power technologies improve and the price of energy continues to rise. The U.S. Department of Energy (DOE), for example, has issued a Notice of Proposed Rulemaking (NOPR) that would lay out the first mandatory regulations for external battery chargers and further tighten regulations on external power supplies.

In what would effectively become the “Level VI” efficiency standard, the proposal on the table would mandate no-load efficiencies down to 0.1 W for external power supplies ranging from 1 W to approximately 49 W, boost mandatory average efficiency by about 1%, and set standards for models with power ratings above 250 W for the first time.  

The EPA estimates that external power supply efficiency regulations implemented over the past decade have reduced energy consumption by 32 billion kW, saving $2.5 billion annually and reducing CO2 emissions by more than 24 million tons per year. Moving beyond the mandated government regulations, many OEMs are now starting to demand “greener” power supplies as a way to differentiate their end products, driving efficiencies continually higher and even pushing the implementation of control technologies that in some cases eliminate no-load power consumption altogether.

In early 2010, CUI Inc. began exclusively manufacturing Level V external power supplies across its 2.5-W to approximately 250-W external power supply product line. Today, CUI continues to look for ways to implement the latest energy-saving technologies into its external power supplies to address market demands and stay one step ahead of current and future regulations. View all Level V compliant power supplies at www.cui.com/Catalog/Power/AC-DC_Power_Supplies/External.


  1. Multiple Standards Confound Power-Supply Designers
  2. Energy Efficiency Standards Around the Globe
  3. California Standards for External Power Supplies
  4. Energy Conservation Standards Rulemaking Framework Document for Battery Chargers and External Power Supplies

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