The Game of Energy Efficiency Leapfrog Continues – Make Sure You're Ready

May 9, 2017 by Jeff Schnabel

The Game of Energy Efficiency Leapfrog Continues – Make Sure You're Ready

To appreciate the full story of energy efficiency and standards, we have to understand the motivation, which very simply is about conserving energy. The concerted effort to reduce the use of energy, especially from non-renewable sources actually started in the early 1990s, when the US rolled out its Energy Star® program as a voluntary labelling initiative, allowing buyers of computer hardware and white goods to make informed decisions regarding their energy usage.

It was then that a study, undertaken by the University of California’s Berkeley Laboratory in 1998, revealed that as much as 5% of the total United States’ domestic electricity consumption was being wasted as a direct consequence of the standby power draw of external power adapters. At that time, most power adapters used linear power conversion technology, whose efficiency could be as low as 50% during normal operation. When the end equipment was turned off or disconnected, the power supplies would continue to burn energy.

This is where our story really begins, with the first introduction of mandatory energy efficiency standards by the California Energy Commission (CEC) in 2004. With the fear that growing numbers of external power adapters could see standby power consumption grow to as much as 30% of total domestic electricity usage, other legislators were quick to follow as can be seen in our Energy Efficiency Standards Timeline. This depicts an evolution of regulatory standards through a number of phases, or what we now refer to as levels, from Level III to the current Level VI.

What will also be apparent from this timeline is how these efficiency regulations have been adopted in a rather jumbled way across different geographies at different times, with some being mandatory and others voluntary. This leapfrog style of progress inevitably poses challenges for equipment manufacturers, particularly those wishing to supply their products to global markets. Therefore, until the often talked about harmonization of standards is achieved, it means OEMs must constantly be aware of new energy efficiency proposals and quick to implement these into their designs.

timeline infographic for external power efficiency standards
This timeline illustrates the dynamic regulatory environment over the past decade
(click to enlarge)

Department of Energy’s Current Level VI Efficiency Regulations

Currently, Level VI represents the peak of mandatory regulation, which became effective in the United States from February 2016. This standard mostly subsumes the European Code of Conduct (CoC) Tier 1 regulations, which were introduced on a voluntary basis in the EU in 2014, with the exception of an extra Tier 1 efficiency requirement that is specified under 10% load conditions. As power adapters are notoriously inefficient at low loads, this poses another design challenge that must be solved by power supply manufacturers.

European Union’s CoC Tier 2 Proposed Requirements

Unfortunately, the energy efficiency standards evolution does not end there. EU CoC Tier 2, proposed to become law in 2018, significantly tightens the limits set by the US Department of Energy (DoE) with its Level VI legislation. These lower limits apply to the minimum average active efficiency (measured at 25%, 50%, 75%, and full load), the new 10% load efficiency measure, and the maximum no-load power draw. Limits are also defined for various classes of power adapter, as illustrated in the tables below for low voltage and basic-voltage types. As an example of how much tougher these standards are becoming, consider a supply with a nameplate rating between 49 W and 250 W – this currently has a maximum no-load power limit of 210 mW under Level VI rules and 250 mW under CoC Tier 1, but will now have to consume less than 150 mW to satisfy Tier 2.

CoC Tier 1 Single-Voltage External Ac-Dc Power Supply, Low-Voltage
Nameplate Output Power (Pout) Minimum Average Efficiency in Active Mode
(expressed as a decimal)
10% Load Average Efficiency in Active Mode
(expressed as a decimal)
Maximum Power in No-Load Mode (W)
0.3 W ≤ Pout < 1 W ≥ 0.50 x Pout +0.086 ≥ 0.50 x Pout ≤ 0.150
1 W < Pout ≤ 49 W ≥ 0.0755 x ln(Pout) + 0.586 ≥ 0.072 x ln(Pout) + 0.50 ≤ 0.150
49 W < Pout ≤ 250 W ≥ 0.880 ≥ 0.780 ≤ 0.250
Pout > 250 W N/A N/A N/A
CoC Tier 2 efficiency specifications for low-voltage power adapters. A low-voltage power adapter is classified as having a nameplate output voltage less than 6 volts and nameplate output current greater than or equal to 550 milliamps.
CoC Tier 2 Single-Voltage External Ac-Dc Power Supply, Basic-Voltage
Nameplate Output Power (Pout) Minimum Average Efficiency in Active Mode
(expressed as a decimal)
10% Load Average Efficiency in Active Mode
(expressed as a decimal)
Maximum Power in No-Load Mode (W)
0.3 W ≤ Pout ≤ 1 W ≥ 0.50 x Pout + 0.169 ≥ 0.50 x Pout + 0.060 ≤ 0.075
1 W < Pout ≤ 49 W ≥ 0.071 x ln(Pout) - 0.00115 x Pout + 0.670 ≥ 0.071 x ln(Pout) - 0.00115 x Pout + 0.570 ≤ 0.075
49 W < Pout ≤ 250 W ≥ 0.890 ≥ 0.790 ≤ 0.150
Pout > 250 W N/A N/A N/A
CoC Tier 2 efficiency specifications for basic-voltage power adapters. A basic-voltage power adapter is anything not classified as a low-voltage power adapter.

Staying Compliant

Clearly OEMs who want to be able to sell a single product across different geographic markets would be best served to “future-proof” their designs by ensuring that their equipment ships with external power adapters that meet the most stringent energy efficiency standards. To do so, it is important to partner with a power manufacturer able to employ leading-edge designs that can deliver the efficiency performance demanded by both current and upcoming standards. At CUI, we pride ourselves on keeping our customers ahead of the game. We have already adapted our circuit topologies to meet efficiency requirements at all load levels, having recently announced that the majority of our external ac-dc power supplies now meet the CoC Tier 1 and Tier 2 efficiency regulations.

Helpful Resources


TODO: tags & categories
Jeff Schnabel

Jeff Schnabel

VP of Global Marketing

With over 15 years of experience in the electronics industry, Jeff Schnabel has a wealth of knowledge on the products, technologies, and standards of interest to design engineers. He has been instrumental in establishing CUI as a thought leader in the industry by developing the company’s extensive library of engineering resources and tools, expanding CUI’s global brand, and positioning the company for future growth. In his free time, Jeff enjoys hiking, traveling, and spending time with his kids, while moonlighting as an amateur competitive eater.