TECHNICAL SUPPORT DOCUMENT: 

ENERGY EFFICIENCY STANDARDS 

FOR CONSUMER PRODUCTS: 

NON­CLASS A EXTERNAL POWER SUPPLIES 

Including: 

Market Assessment 

Technology Assessment 

Engineering Analysis 

Energy Use and End­Use Load Characterization 

Life­Cycle Cost and Payback Period Analysis 

National Impact Analysis 

August 2009 

U.S. Department of Energy 

Assistant Secretary 

Energy Efficiency & Renewable Energy 

Office of Building Research and Standards 

Washington, DC 20585 

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This Document was prepared for the Department of Energy
�

by staff members of
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D&R International, Ltd
�

and
�

Navigant Consulting, Inc
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TABLE OF CONTENTS
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CHAPTER 1 MARKET ASSESSMENT................................................................................ 1­1
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1.1 Introduction................................................................................................................... 1­1
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1.2 Distribution Channels and Markups ............................................................................. 1­1
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1.2.1 Multiple­Voltage External Power Supplies ......................................................... 1­1
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1.2.2 High Output Power External Power Supplies...................................................... 1­2
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1.2.3 External Power Supplies for Medical Devices .................................................... 1­3
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1.2.4 External Power Supplies for Certain Battery Chargers ....................................... 1­4
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1.3 Interested Parties........................................................................................................... 1­6
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1.4 Existing Energy Efficiency Programs........................................................................... 1­7
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CHAPTER 2 TECHNOLOGY ASSESSMENT ..................................................................... 2­1
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2.1 Introduction................................................................................................................... 2­1
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2.2 Functionality of Non­Class A EPSs.............................................................................. 2­1
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2.2.1 Particular Functionality of Multiple­Voltage EPSs ............................................. 2­1
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2.2.2 Particular Functionality of High­Power EPSs ..................................................... 2­2
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2.2.3 Particular Functionality of Medical EPSs............................................................ 2­3
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2.2.3.1 Lifetime of Medical EPSs.................................................................................... 2­4
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2.2.3.2 Safety Concerns of Medical EPSs ....................................................................... 2­4
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2.2.3.3 Levels of Protection under UL 60601­1 .............................................................. 2­5
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2.2.3.4 Output Voltages of Medical EPSs ....................................................................... 2­5
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2.2.3.5 Leakage Currents in Medical EPSs...................................................................... 2­6
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2.2.3.6 Maintaining Safety Certification.......................................................................... 2­7
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2.2.4 Particular Functionality of EPSs for BCs ............................................................ 2­7
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2.2.5 Electromagnetic Interference Suppression .......................................................... 2­7
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2.3 Circuit Design of EPSs ................................................................................................. 2­9
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2.3.1 General Design of an External Power Supply ..................................................... 2­9
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2.3.2 Design Choice: Single Versus Multiple Voltage EPSs...................................... 2­10
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2.3.3 Class A AC/AC External Power Supplies ......................................................... 2­12
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2.3.4 Class A Unregulated Line­Frequency AC/DC External Power Supplies.......... 2­12
­

2.3.5 Class A Linear­Regulated Line­Frequency AC/DC External Power Supplies.. 2­13 

2.3.6 Class A Switching­Regulated Line­Frequency AC/DC External Power Supplies2­15 

2.3.7 Switched­Mode AC/DC External Power Supplies ............................................ 2­16
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2.3.8 Design of Output Cables.................................................................................... 2­18
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2.3.9 Particular Designs of Multiple­Voltage EPSs.................................................... 2­19
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2.3.9.1 Additional Regulators from a Single Tap .......................................................... 2­19
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2.3.9.2 Multiple Taps..................................................................................................... 2­20
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2.3.9.3 Multiple Windings ............................................................................................. 2­21
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2.3.9.4 Multiple Cores ................................................................................................... 2­22
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2.3.10 Particular Designs of High­Power EPSs............................................................ 2­23
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2.3.10.1 Line­Frequency Designs for High­Power EPSs .............................................. 2­24
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2.3.10.2 Switched­Mode Designs for High­Power EPSs .............................................. 2­24
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2.3.11 Particular Designs of Medical EPSs .................................................................. 2­28
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2.3.12 Particular Designs of EPSs for BCs................................................................... 2­29
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2.4 Technology Options for Improving Energy Efficiency.............................................. 2­29
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2.4.1 Transformers...................................................................................................... 2­29
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2.4.2 Diode Losses and Synchronous Rectification.................................................... 2­30
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2.4.3 Technology Options for Multiple­Voltage EPSs............................................... 2­31
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2.4.4 Technology Options for High­Power EPSs ....................................................... 2­31
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2.4.5 Technology Options for Medical EPSs.............................................................. 2­31
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2.4.6 Technology Options for EPSs for BCs .............................................................. 2­31
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CHAPTER 3 ENGINEERING ANALYSIS ........................................................................... 3­1
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3.1 Introduction................................................................................................................... 3­1
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3.2 DOE Methods for Determining ERMC ........................................................................ 3­1
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3.2.1 Summary of Methods........................................................................................... 3­2
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3.2.2 Available Data ..................................................................................................... 3­3
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3.2.2.1 SME Efficiency Measurements of 5 W EPSs...................................................... 3­3
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3.2.2.2 SME Teardowns................................................................................................... 3­3
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3.2.3 DOE Method for Determining ERMC from iSuppli Data................................... 3­4
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3.2.4 Assumptions......................................................................................................... 3­8
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3.2.4.1 Production Volume .............................................................................................. 3­8
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3.2.4.2 Data Included in the Cost­Efficiency Curves ...................................................... 3­8
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3.2.5 SME Cost­Scaling Methodology ......................................................................... 3­9
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3.2.5.1 Direct Substitution of iSuppli Component Costs................................................. 3­9
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3.2.5.2 Direct Substitution of Category­Average iSuppli Component Costs .................. 3­9
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3.2.5.3 Scaling of SME Costs Using SME­iSuppli Component Matches ..................... 3­11
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3.2.5.4 Substitute Category­Average iSuppli Component Costs................................... 3­14
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3.2.6 Summary............................................................................................................ 3­15
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3.3 Scaling EPS Efficiency with Output Power................................................................ 3­15
­

3.4 Scaling EPS Efficiency with Output Voltage ............................................................. 3­18
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3.4.1 Summary and Introduction ................................................................................ 3­18
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3.4.2 Experimental Basis ............................................................................................ 3­19
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3.4.3 Loss Calculations............................................................................................... 3­20
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3.4.4 Conclusion and Examples.................................................................................. 3­22
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3.5 Cost Scaling by Nameplate Output Power and Sales Volume ................................... 3­24
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3.5.1 Introduction........................................................................................................ 3­24
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3.5.2 Observed Relationships in Available Data ........................................................ 3­24
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3.5.3 Model Development........................................................................................... 3­26
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3.5.4 Model Deployment ............................................................................................ 3­30
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3.6 Representative Product Classes and Representative Units ......................................... 3­31
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3.6.1.1 Representative Product Classes and Units for Multiple­Voltage EPSs............. 3­31
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3.6.1.2 Representative Product Classes and Units for High­Power EPSs ..................... 3­33
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3.6.1.3 Representative Product Classes and Units for Medical EPSs............................ 3­35
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3.6.1.4 Representative Product Classes and Units for EPSs for BCs ............................ 3­37
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3.7 Selection of Candidate Standard Levels ..................................................................... 3­40
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3.7.1.1 Candidate Standard Levels for Multiple­Voltage EPSs..................................... 3­42
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3.7.1.2 Candidate Standard Levels for High­Power EPSs............................................. 3­45
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3.7.1.3 Candidate Standard Levels for Medical Device EPSs....................................... 3­45
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3.7.1.4 Candidate Standard Levels for EPSs for BCs.................................................... 3­47
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CHAPTER 4 ENERGY USE AND END­USE LOAD CHARACTERIZATION ................. 4­1
­

4.1 Introduction................................................................................................................... 4­1
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4.2 Walkthrough of Unit Energy Consumption Calculation .............................................. 4­1
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4.2.1 Usage Profile for Multiple­Voltage EPS (203W, Xbox 360).............................. 4­2
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4.2.2 EPS Power Consumption by Modes of Operation............................................... 4­2
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4.2.3 Active Mode Efficiency and No Load Mode Power Consumption..................... 4­3
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4.2.4 Calculating Unit Energy Consumption................................................................ 4­3
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4.3 Unit Energy Consumption Values for Non­Class A External Power Supplies ............ 4­8
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4.3.1 Multiple­Voltage EPS for Multifunction Devices ............................................... 4­8
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4.3.2 High­Power EPS for Amateur Radio Equipment ................................................ 4­9
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4.3.3 EPS for Medical Devices................................................................................... 4­12
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4.3.4 EPS for Battery Chargers for Floor Care Appliances........................................ 4­14
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4.3.5 EPS for Battery Chargers for Power Tools........................................................ 4­15
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4.4 EPS Power Consumption by Modes of Operation...................................................... 4­17
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4.4.1 EPS Energy Use................................................................................................. 4­20
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4.4.1.1 EPS Energy Consumption.................................................................................. 4­20
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CHAPTER 5 LIFE­CYCLE COST AND PAYBACK PERIOD ANALYSIS ....................... 5­1
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5.1 Life­Cycle Cost and Payback Period Analysis ............................................................. 5­1
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5.1.1 Introduction.......................................................................................................... 5­1
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5.1.2 Overview of LCC and PBP Inputs....................................................................... 5­2
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5.1.3 Life­Cycle Cost Inputs......................................................................................... 5­5
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5.1.3.1 Efficiency­Related Consumer Purchase Price Inputs .......................................... 5­6
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5.1.3.2 Operating Cost Inputs .......................................................................................... 5­7
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5.1.3.3 Other Inputs to the LCC Analysis...................................................................... 5­10
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5.1.4 Payback Period Inputs........................................................................................ 5­12
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5.1.4.1 Definition and Inputs ......................................................................................... 5­12
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CHAPTER 6 NATIONAL IMPACT ANALYSIS.................................................................. 6­1
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6.1 Introduction................................................................................................................... 6­1
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6.2 National Inventory ........................................................................................................ 6­2
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6.3 Layout of the NES­NPV Workbook............................................................................. 6­3
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6.4 NES­NPV Calculation Walkthrough ............................................................................ 6­7
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6.4.1 Calculation of Unit Energy Savings .................................................................... 6­7
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6.4.2 Calculation of National Energy Savings in kWh................................................. 6­9
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6.4.3 Calculation of National Energy Savings in 2008$............................................. 6­12
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6.4.4 Calculating Incremental Unit Cost Increases..................................................... 6­12
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6.4.5 Calculation of National Costs in $ (non­discounted)......................................... 6­14 

6.4.6 Calculation of National Costs in 2008$............................................................. 6­17 

6.4.7 Calculation of Net Present Value in 2008$........................................................ 6­17 

6.5 Net Present Value Results........................................................................................... 6­17
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APPENDIX A.	­NON­CLASS A EXTERNAL POWER SUPPLY COST­EFFICIENCY 

ESTIMATION SURVEY...................................................................................... I 

LIST OF FIGURES 

Figure 1.1 Distribution Channels for Multiple­Voltage External Power Supplies...................... 1­1 

Figure 1.2 Distribution Channels for High Power External Power Supplies .............................. 1­2 

Figure 1.3 Distribution Channels for External Power Supplies for Medical Devices ................. 1­4 

Figure 1.4 Distribution Channels for External Power Supplies for Certain Battery Chargers.... 1­5 

Figure 2.1 Example Circuit of an EMI Filter............................................................................... 2­8 

Figure 2.2 Topologies for External Power Supplies.................................................................. 2­10 

Figure 2.3 Power Distribution Configurations for Consumer Products With Subsystems 

Requiring Different Supply Voltages ..................................................................... 2­11
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Figure 2.4 Circuit Diagram for an AC/AC External Power Supply .......................................... 2­12
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Figure 2.5 Circuit Diagram of a Line­Frequency Raw Supply.................................................. 2­13
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Figure 2.6 Block Diagram of a Linear Regulator ...................................................................... 2­14
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Figure 2.7 Simplified Circuit Diagram of a Linear Regulator................................................... 2­14
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Figure 2.8 Block Diagram of a Switching­Regulated Line­Frequency AC/DC EPS................ 2­16
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Figure 2.9 Block Diagram of a Switched­Mode Power Supply ................................................ 2­16
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Figure 2.10 Simplified Circuit Diagram of a Flyback Switching Regulator ............................. 2­17
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Figure 2.11 The second winding is center­tapped, providing multiple voltages ....................... 2­21
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Figure 2.12 Multiple­Voltage EPS Design with Multiple Independent Cores, Which Allow the
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Operation of One of the Outputs to be Suspended When Not Needed .................. 2­23
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Figure 2.13 Switched­Mode Topologies and Corresponding Power Levels ............................. 2­25
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Figure 2.14 Two­Transistor Forward Converter Circuit............................................................ 2­26
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Figure 2.15 Push­Pull Converter Circuit ................................................................................... 2­27
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Figure 2.16 Half­Bridge Converter Circuit................................................................................ 2­27
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Figure 2.17 Full­Bridge Converter Circuit ................................................................................ 2­28
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Figure 3.1 Illustration of DOE Process Used to Compile High­Volume Cost Estimates for the
­

Non­Class A Eps Determination Analysis from Sme and Isuppli Teardowns......... 3­2 

Figure 3.2 SME Efficiency Measurements of 5 W EPSs ............................................................ 3­3 

Figure 3.3 Categorization of Components Used to Perform Substitution or Scaling.................. 3­9 

Figure 3.4 Tests of Variation and Number of Cost Estimates Necessary for Device Scaling... 3­10 

Figure 3.5 Schematic Illustration of the Distribution of Efficiency Versus Maximum Rated 

Output Power; the ENERGY STAR Level Is Shown as a Pink Line, while the Blue 

Background Indicates Where Most of the Units Lie .............................................. 3­16
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Figure 3.6 Schematic Illustration of Scaling EPS Efficiency with Output Power .................... 3­17
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Figure 3.7 ENERGY STAR Level and Calculated Best­in­Market and Worst­in­Market Curves3­17
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Figure 3.8 Schematic of EPS Loss Model Used for Scaling Efficiency with Voltage.............. 3­19
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Figure 3.9 Difference in Active Mode Efficiency vs. Nameplate Output Voltage................... 3­20
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Figure 3.10 Efficiencies of 5W, 5V EPS Test Units After Scaling to the 1.8 W, 6 V 

Representative Unit Level ...................................................................................... 3­23 

Figure 3.11 Efficiencies of 5W, 5V EPS Test Units After Scaling to the 4.8 W, 24 V 

Representative Unit Level. ..................................................................................... 3­23 

Figure 3.12 Manufacturer Selling Price Versus Volume For Specific 2W and 5W EPSs ........ 3­25 

Figure 3.13 Manufacturer Selling Price Versus Output Power for Specific 2 W And 5 W EPSs at 

Different Production Volumes................................................................................ 3­25 

Figure 3.14 Example EPS materials Cost Modeled as a Sum of Fixed and Incremental Costs.3­26 

Figure 3.15 Offset Efficiency­Related Materials Cost Versus Volume for Specific 2W and 5W 

EPSs........................................................................................................................ 3­27
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Figure 3.16 Extended Trendlines Based on Publicly Available EPS Data................................ 3­28
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Figure 3.17 Extended trendlines with confidential dataset trendline added. ............................. 3­29
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Figure 3.18 Product Count for Multiple­Voltage EPSs............................................................. 3­32
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Figure 3.19 Product Count for High­Power EPSs ..................................................................... 3­34
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Figure 3.20 Product Count for Medical EPSs............................................................................ 3­36
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Figure 3.21 Estimate of Energy Consumption for Different EPSs for BCs .............................. 3­39
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Figure 3.22 Comparison of Active Mode Efficiency and No­Load Power; Arrows Point in
­

Direction of Increased Efficiency........................................................................... 3­42 

Figure 4.1 Relationship Between EPS Input Power and Output Power at Five Loading Points as 

Measured by the Test Procedure............................................................................. 4­19 

Figure 5.1 Usage of External Power Supplies ............................................................................. 5­2 

Figure 5.2 Flow Diagram of Inputs for the Determination of LCC and PBP.............................. 5­3 

Figure 5.3 Normalized AEO2009 Residential Sector Reference Case Electricity Price Trend 5­10 

Figure 6.1 Flow Chart Showing the Calculation of National Energy Savings and Net Present 

Value......................................................................................................................... 6­3
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LIST OF TABLES 

Table 1.1 Markups for Multiple­Voltage External Power Supplies ............................................ 1­2
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Table 1.2 Markups for High Power External Power Supplies..................................................... 1­3
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Table 1.3 Markups for External Power Supplies for Medical Devices ....................................... 1­4
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Table 1.4 Markups for External Power Supplies for Battery Chargers ....................................... 1­5
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Table 1.5 Trade Associations and Their Likely Areas of Interest ............................................... 1­6
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Table 1.6 Trade Associations and Their Members ...................................................................... 1­7
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Table 1.7 Selected Energy Efficiency Programs for External Power Supplies ........................... 1­8
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Table 2.1 Maximum Leakage Current for Portable Equipment .................................................. 2­6
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Table 2.2 Quality of Core Steel and Level of Magnetic Induction............................................ 2­30
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Table 3.1 EPSs Torn Down by SMEs to Develop Low­Volume ERMCs................................... 3­4
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Table 3.2 Information for Five Components from EPS #106...................................................... 3­5
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Table 3.3 Information for All Components from EPS #106........................................................ 3­6
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Table 3.4 EPS #106 Production Related Device Information ..................................................... 3­7
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Table 3.5 EPS # 106 Summary of Component Costs by Efficiency Relevance.......................... 3­7
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Table 3.6 EPS and BC Units that iSuppli Tore Down and DOE Used in Data Scaling.............. 3­8
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Table 3.7 Example Matches Between SME and iSuppli Component Cost Estimates Used to
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Develop Category­Specific Scaling Ratios ............................................................ 3­12
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Table 3.8 Losses for Scaling Model for Efficiency with Output Voltage ................................. 3­20
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Table 3.9 Value of Calculated Model Parameters ..................................................................... 3­30
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Table 3.10 Representative Product Classes for Multiple­Voltage EPSs ................................... 3­31
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Table 3.11 Characteristics of the Multiple­Voltage EPS Representative Units ........................ 3­33
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Table 3.12 Representative Product Classes for High­Power EPSs............................................ 3­33
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Table 3.13 Characteristics of the High­Power EPS Representative Unit .................................. 3­35
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Table 3.14 Representative Product Classes for Medical EPSs.................................................. 3­35
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Table 3.15 Characteristics of the Medical EPS Representative Unit......................................... 3­37
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Table 3.16 Representative Product Classes for EPSs for BCs................................................... 3­37
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Table 3.17 Representative Unit Characteristics for Battery Chargers....................................... 3­38
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Table 3.18 Assumptions for Calculating Annual Energy Consumption.................................... 3­38
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Table 3.19 Characteristics of the EPS for BCs Representative Units........................................ 3­40
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Table 3.20 Candidate Standard Levels for a 40­Watt Multiple­Voltage EPS for a Multi­Function
­

Device ..................................................................................................................... 3­43 

Table 3.21 Candidate Standard Levels for a 203­Watt Multiple­Voltage EPS for a Video Game 

Console ................................................................................................................... 3­43
­

Table 3.22 Candidate Standard Levels for a 345­Watt High­Power EPS for a Ham Radio...... 3­45
­

Table 3.23 Candidate Standard Levels for an 18­Watt Medical Device EPS for a Nebulizer .. 3­46
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Table 3.24 Candidate Standard Levels for a 1.8­Watt EPS for BC for a Vacuum.................... 3­47
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Table 3.25 Candidate Standard Levels for a 4.8­Watt EPS for a Do­It­Yourself Power Tool.. 3­47
­

Table 4.1 Weighted­Average Usage and Output Power of EPS for Xbox 360 ........................... 4­2
­

Table 4.2 Load by Application State for EPS for Xbox 360 ....................................................... 4­3
­

Table 4.3 Candidate Standard Levels for an EPS for Xbox 360 ................................................. 4­3
­

Table 4.4 Equations Used to Calculate Energy Consumption in Each Application State........... 4­4
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Table 4.5 UEC for Active – Playing Video Game (EPS Output Power = 102.62 W)................. 4­5
­

Table 4.6 UEC for Active – Idle Video Game (EPS Output Power = 101.50 W)....................... 4­5
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Table 4.7 UEC for Active – Playing DVD (EPS Output Power = 95.02 W) .............................. 4­5
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Table 4.8 UEC for Active – Idle DVD (EPS Output Power = 95.02 W) .................................... 4­6
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Table 4.9 UEC for Active – Idle No­Disc (EPS Output Power = 86.38 W) ............................... 4­6
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Table 4.10 UEC for Active – Off (EPS Output Power = 2.35 W)............................................... 4­6
­

Table 4.11 UEC for Active ­ Continued ...................................................................................... 4­7
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Table 4.12 UEC for No Load Mode ............................................................................................ 4­7
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Table 4.13 UEC by Application State at Each Candidate Standard Level .................................. 4­8
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Table 4.14 Candidate Standard Levels for 40 W Multiple­Voltage EPS for Multifunction
­

Devices ..................................................................................................................... 4­8 

Table 4.15 Usage and Output Power of EPS for 40 W Multiple­Voltage EPS for Multifunction 

Devices ..................................................................................................................... 4­9 

Table 4.16 Unit Energy Consumption for 40 W Multiple­Voltage EPS for Multifunction Devices4­9 

Table 4.17 Candidate Standard Levels for 345 W High­Power EPS for Amateur Radio 

Equipment................................................................................................................. 4­9
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Table 4.18 Light Usage of 345 W High­Power EPS for Amateur Radio Equipment ............... 4­10
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Table 4.19 Medium Usage of 345 W High­Power EPS for Amateur Radio Equipment........... 4­10
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Table 4.20 Heavy Usage of 345 W High­Power EPS for Amateur Radio Equipment.............. 4­11
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Table 4.21 Weighted­Average Usage and Output Power of 345 W High­Power EPS for Amateur
­

Radio Equipment .................................................................................................... 4­11 

Table 4.22 Unit Energy Consumption for 345 W High­Power EPS for Amateur Radio Equipment4­12 

Table 4.23 Candidate Standard Levels for 18 W EPS for Medical Devices ............................. 4­12 

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Table 4.24 Medium Usage of 18 W EPS for Medical Devices ................................................. 4­12
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Table 4.25 Heavy Usage of 18 W EPS for Medical Devices .................................................... 4­13
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Table 4.26 Weighted­Average Usage and Output Power of 18 W EPS for Medical Devices .. 4­13
­

Table 4.27 Unit Energy Consumption for 18 W EPS for Medical Devices .............................. 4­13
­

Table 4.28 Candidate Standard Levels for 1.8 W EPS for Floor Care Appliances ................... 4­14
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Table 4.29 Usage and Output Power of 1.8 W EPS for Floor Care Appliances ....................... 4­14
­

Table 4.30 Unit Energy Consumption for 1.8 W EPS for Floor Care Appliances .................... 4­14
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Table 4.31 Candidate Standard Levels for 4.8 W EPS for Power Tools................................... 4­15
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Table 4.32 Light Usage of 4.8 W EPS for Power Tools............................................................ 4­15
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Table 4.33 Heavy Usage of 4.8W EPS for Power Tools........................................................... 4­16
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Table 4.34 Weighted­Average Usage and Output Power of 4.8 W EPS for Power Tools........ 4­16
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Table 4.35 Unit Energy Consumption for 4.8 W EPS for Power Tools.................................... 4­17
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Table 5.1 Draft Inputs to the Life­Cycle Cost and Payback Period Analysis.............................. 5­4
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Table 5.2 Annual Average Consumer Price Indices.................................................................... 5­9
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Table 5.3 AEO2009 Electricity Prices......................................................................................... 5­9
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Table 5.4 Shares and Interest or Return Rates Used for Household Debt and Equity Types.... 5­11
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Table 6.1 Example National Inventory Table.............................................................................. 6­2
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Table 6.2 Unit Energy Consumption in the Base Case (2013).................................................... 6­8
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Table 6.3 Unit Energy Consumption in the Standards Case (2013) ............................................ 6­8
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Table 6.4 Unit Energy Savings by Shipment Year .................................................................... 6­10
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Table 6.5 Unit Inventory In 2018 .............................................................................................. 6­10
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Table 6.6 Combination of Tables 6.4 and 6.5............................................................................ 6­11
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Table 6.7 Unit Cost in the Base Case ........................................................................................ 6­13
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Table 6.8 Unit Cost in the Standards Case ................................................................................ 6­13
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Table 6.9 Unit Incremental Cost by Shipment Year.................................................................. 6­15
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Table 6.10 Unit Shipments by Shipment Year .......................................................................... 6­15
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Table 6.11 Combination of Tables 6.9 and 6.10........................................................................ 6­16
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Table 6.12 Net Present Value of Standards at 3 Percent Discount Rate.................................... 6­18
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Table 6.13 Net Present Value of Standards at 7 Percent Discount Rate.................................... 6­19
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CHAPTER 1 MARKET ASSESSMENT 

1.1 Introduction 

This chapter of the Technical Support Document (TSD) contains information that 

supports and expands upon the market assessment section of the notice of proposed 

determination. The notice was issued by the U.S. Department of Energy as part of its 

determination concerning the potential for energy conservation standards for non­Class A 

external power supplies.a 

1.2 Distribution Channels and Markups 

1.2.1 Multiple­Voltage External Power Supplies 

Almost all EPSs in this group are contracted by two OEMs (Microsoft and HP) for use 

with two products (Xbox 360 and HP’s multifunction devices) and are not sold through EPS 

distributors or directly to retailers. Once packaged with the Xbox 360 or a multifunction device, 

products are sold exclusively through retailers. Figure 1.1 depicts the distribution system just 

described. Based on its understanding of distribution channels, DOE calculated a markup of 

between 3.15 and 3.18 for multiple­voltage EPSs from ERMC to post­tax consumer price. This 

markup is detailed in Table 1.1. 

Component Manufacturers

EPS Manufacturers

Consumers

OEMs

Consumer Product

Retailers

Figure 1.1 Distribution Channels for Multiple­Voltage External Power Supplies 

a The notice and the accompanying TSD can be downloaded from the Office of Energy Efficiency and Renewable 

Energy’s website: http://www1.eere.energy.gov/buildings/appliance_standards/residential/battery_external.html 

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Table 1.1 Markups for Multiple­Voltage External Power Supplies
­

Step Markup 

EPSs for MFDs EPSs for Xbox 360 

EPS Manufacturer Markup 64% 64% 

OEM Markup 32% 31% 

Device Retailer/Distributor Markup 37% 37% 

Sales Tax 6.8% 6.8% 

Consumer Price : ERMC 3.18 : 1 3.15 : 1 

Source: EPS Manufacturer markups based on interviews with EPS Manufactures. OEM and retailer markups are 

based on gross margin data for public companies retrieved from http://finance.yahoo.com. The population­weighted, 

national average sales tax figure is from the Sales Tax Clearinghouse, Inc. (http://www.thestc.com/FAQ.stm) 

1.2.2 High Output Power External Power Supplies 

Because of the flexible environment in which EPSs intended for use with amateur radio 

equipment are used, these EPSs are not supplied with specific applications or equipment. Rather, 

they are sold as stand­alone products, so their design and manufacture is initiated by the EPS 

manufacturer itself. The EPS manufacturer then distributes the product through specialty retailers 

for amateur radio equipment. Because of the small number of retailers and low volume of 

shipments involved, EPS distributors are generally not used. Figure 1.2 depicts the distribution 

system just described. Based on its understanding of distribution channels, DOE calculated the 

markup for high power EPSs at 1.80 from ERMC to post­tax consumer price. This markup is 

detailed in Table 1.2. 

Component Manufacturers

EPS Manufacturers

Consumer Product

Retailers

Consumers

Figure 1.2 Distribution Channels for High Power External Power Supplies
­

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Table 1.2 Markups for High Power External Power Supplies
­

Step Markup 

EPS Manufacturer Markup 24% 

Retailer 36% 

Sales Tax 6.8% 

Consumer Price : ERMC 1.80 : 1 

Source: EPS Manufacturer markups based on interviews with EPS Manufactures. OEM and retailer markup based 

on difference between estimated distributor price and retailer price. The population­weighted, national average sales 

tax figure is from the Sales Tax Clearinghouse, Inc. (http://www.thestc.com/FAQ.stm) 

1.2.3 External Power Supplies for Medical Devices 

Medical devices, unlike most other applications powered by EPSs, must meet certain 

design requirements before distribution. These requirements are maintained by the FDA’s Center 

for Devices and Radiological Healthb and covered under 21 CFR 800­1299.c Despite these 

additional design requirements, the distribution for EPSs for medical devices is roughly similar 

to that of other EPSs. This is because while the requirements of 21 CFR 800­1299 affect the 

design of the EPS, the medical devices to which the EPS provides power generally do not require 

anything beyond the requirements of a generic power source. Therefore, once an EPS is built to 

the requirements of 21 CFR 800­1299, it can be used with multiple medical devices, much as a 

generic Class A EPS can be used with multiple applications. For those medical devices requiring 

more specialized input power, custom EPSs may be used instead. 

Once the EPS is received by the OEM, it is packaged with the device itself then sold via 

medical device distributors or specialty retailers. OEM’s rarely sell medical devices directly to 

consumers. Figure 1.3 outlines the distribution system for EPSs used to power medical devices 

as just described. Based on its understanding of distribution channels, DOE calculated a markup 

for medical device EPSs between 3.46 and 4.02 times the ERMC and a shipment­weighted 

average markup of 3.60. This markup is detailed in Table 1.3. 

b http://www.fda.gov/CDRH/ c http://www.accessdata.fda.gov/scripts/cdrh/cfdocs/cfcfr/CFRSearch.cfm?CFRPartFrom=800&CFRPartTo=1299 

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Component Manufacturers

EPS Manufacturers

EPS
 Distributors
 

OEMs
 

Medical Product Medical Product
 Distributors Retailers
 

Consumers
 

Figure 1.3 Distribution Channels for External Power Supplies for Medical Devices 

Table 1.3 Markups for External Power Supplies for Medical Devices 

Step Markup 

EPS Manufacturer Markup 64% 

[EPS Distributor Markup] 16% 

OEM Markup 50% 

Retailer/Distributor Markup 32% 

Sales Tax 6.8% 

Consumer Price : ERMC (without 

distributor) 

Consumer Price : ERMC (with distributor) 

3.46: 1 

4.02 : 1 

Shipment­Weighted Average Markup 3.60 : 1 

Source: EPS Manufacturer markups based on interviews with EPS Manufactures. OEM and retailer markups are 

based on gross margin data for public companies retrieved from http://finance.yahoo.com. The population­weighted, 

national average sales tax figure is from the Sales Tax Clearinghouse, Inc. (http://www.thestc.com/FAQ.stm). 

Assumes 25 percent of EPS shipments pass through an EPS distributor on their way to the OEM. 

1.2.4 External Power Supplies for Certain Battery Chargers 

Similar to the design of multiple­voltage EPSs, the design of EPSs to be used with battery 

chargers is highly customized. Because of this, DOE believes that EPSs in this group are nearly 

always contracted by OEMS for use with a specific product. It is unlikely that any EPS to be 

used with a battery charger would ever be sold separately from the battery charging system, 

except possibly as a replacement part. In addition, DOE could find no instance of an OEM 

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selling directly to consumers. Therefore, DOE assumes that all EPSs in this category are 

contracted by an OEM and sold through a retailer. Figure 1.4 outlines the distribution system for 

EPSs for battery chargers as just described. Based on its understanding of distribution channels, 

DOE calculated markups for EPSs for battery chargers of 3.69 times the ERMC for floor care 

appliances and 4.14 times the ERMC for DIY power tools. See Table 1.4 for more detail. 

Component Manufacturers

EPS Manufacturers

Consumers

OEMs

Consumer Product

Retailers

Figure 1.4 Distribution Channels for External Power Supplies for Certain Battery 

Chargers 

Table 1.4 Markups for External Power Supplies for Battery Chargers 

Step 

Markup 

Floor Care 

Appliances 

DIY Power 

Tools 

EPS Manufacturer Markup 60% 60% 

OEM Markup 49% 61% 

Retailer Markup 45% 51% 

Sales Tax 6.8% 6.8% 

Consumer Price: ERMC 3.69 : 1 4.14 : 1 

Source: EPS Manufacturer markups based on interviews with EPS Manufactures. OEM and retailer markups are 

based on gross margin data for public companies retrieved from http://finance.yahoo.com. The population­weighted, 

national average sales tax figure is from the Sales Tax Clearinghouse, Inc. (http://www.thestc.com/FAQ.stm) 

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1.3 Interested Parties 

Table 1.5 lists a number trade associations that may have an interest in this determination 

and indicates which types of NCA EPS DOE believes each association has an interest in. Table 

1.6 gives examples of each association’s member companies. 

Table 1.5 Trade Associations and Their Likely Areas of Interest 

Trade Association 

MultipleVoltage 

EPSs 

High Power 

EPSs 

Medical 

EPSs 

EPSs for 

Certain 

Battery 

Chargers 

Advanced Medical 

Technology Assoc. X 

American Radio Relay 

League X 

Assoc. for the Advancement 

of Medical Instrumentation X 

Assoc. of Home Appliance 

Manufacturers X 

Consumer Electronics 

Assoc. X X 

European Power Supply 

Manufacturers Assoc. X X X X 

Information Technology 

Industry Council X 

Medical Device 

Manufacturers Assoc. X 

Power Sources 

Manufacturers Assoc. X X X X 

Power Tool Institute X 

Source: Trade association websites and lists of past participants in DOE’s battery charger and external power supply 

rulemakings. 

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Table 1.6 Trade Associations and Their Members
­

Trade Association Examples of Members 

Advanced Medical 

Technology Assoc. Baxter International, Covidien, Philips Healthcare 

American Radio Relay 

League 

(The ARRL is the largest national membership 

association for Amateur Radio operators in the U.S.) 

Assoc. for the Advancement 

of Medical Instrumentation (Membership list is not publicly available.) 

Assoc. of Home Appliance 

Manufacturers 

BISSEL Homecare, Black & Decker Corp., Dyson 

Limited, KitchenAid (Whirlpool), Panasonic, Philips 

Electronics, Remington, Wahl Clipper 

Consumer Electronics 

Assoc. 

Apple, Bose, Canon USA, Daewoo, Energizer, Epson, 

Dell, Garmin, HP, JVC, Kodak, LG, Microsoft, 

Mitsubishi, Nokia, Panasonic, Philips, Radio Shack, 

Ricoh, Samsung, Sanyo, Sony, Toshiba, Tyco 

European Power Supply 

Manufacturers Assoc. 

Artesyn Technologies, Astec Europe, Cherokee, Delta 

Electronics, Efore, FRIWO Power Solutions, Lambda 

Europe, MagnaTek, Roal Electronics 

Information Technology 

Industry Council 

Apple, Canon, Cisco, Dell, Kodak, HP, Lenovo, 

Lexmark, Microsoft, Panasonic, Sony, Texas Instruments 

Medical Device 

Manufacturers Assoc. (Membership list is not publicly available.) 

Power Sources 

Manufacturers Assoc. 

Artesyn, Astec, Ault, Cherokee, China Power Supply 

Society, Emerson Energy Systems, Leader Electronics, 

Power Integrations 

Power Tool Institute Black and Decker, Bosch, Dewalt, Delta, Dremel, 

Makita, Ryobi 

Source: AHAM, CEA, EPSMA, ITIC, PSMA, and PTI websites. 

1.4 Existing Energy Efficiency Programs 

DOE has identified both voluntary and regulatory energy efficiency programs that may 

affect the efficiency of NCA EPSs sold in the United States. The five most important programs, 

summarized in Table 1.7, include three domestic programs and two foreign programs. The three 

domestic programs are the federal mandatory standard for Class A EPSs, the U.S. EPA’s 

voluntary ENERGY STAR standard for EPSs, and California’s mandatory standard for so­called 

“State Regulated EPSs.” Among the many foreign programs, there are two particularly 

noteworthy programs in the European Union. All five programs are discussed below. 

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Table 1.7 Selected Energy Efficiency Programs for External Power Supplies
­

Country/Region Authority Program/Institution 

United States Mandatory Federal standard for Class A EPSs 

United States Voluntary ENERGY STAR for EPSs 

California Mandatory State standard for “State Regulated EPSs” 

European Union Mandatory Eco­design of Energy­using Products (EuP) 

Initiative, Directive 2005/32/EC 

European Union Voluntary Code of Conduct on Efficiency of External Power 

Supplies, EU Standby Initiative 

A federal standard for Class A EPSs took effect on July 1, 2008. This standard, while 

intended to regulate only Class A EPSs, may very well have a spillover effect on the efficiency 

of EPSs outside of Class A. The standard for Class A EPSs has increased the demand for, and 

lowered the cost of, some of the more efficient components and has stimulated the adoption of 

improved designs. Because many of the same techniques and components are used to 

manufacture NCA EPSs that are used to manufacture Class A EPSs, DOE assumes that some of 

these components and designs will carry over into the design and manufacture of NCA EPSs. 

New, more stringent ENERGY STAR criteria for EPSs took effect on November 1, 2008. 

As of December 2, 2008, there were already over 1,000 qualified models.d Like the existing 

federal standard, these voluntary criteria apply only to Class A EPSs. Nevertheless, DOE expects 

the ENERGY STAR program’s efforts to improve the energy efficiency of Class A EPSs to have 

some spillover effect on the efficiency of NCA EPSs. 

On December 3, 2008 the California Energy Commission adopted standards, retroactive 

to July 1, 2008, for certain “State Regulated EPSs.”e State Regulated EPSs appear to include 

EPSs for medical devices and for most battery chargers, but explicitly exclude multiple­voltage 

EPSs and high power EPSs. The standard levels are identical to those for Class A EPSs. 

California is home to about 12 percent of the U.S. populationf and probably represents about the 

same proportion of the U.S. market for EPSs for medical devices and certain BCs. Thus, if 

manufacturers are complying with California law, at least 12 percent of the NCA EPSs of these 

two types sold in the U.S. already comply with the standard for Class A EPSs. In fact, it is likely 

that an even larger proportion comply, given that manufacturers tend to sell the same products 

throughout the country. 

d External Power Supplies Ac­Dc QP List. U.S. Environmental Protection Agency. December 2, 2008. (Retrieved
­

12/17/08 from http://www.energystar.gov/index.cfm?c=manuf_res.pt_adapters)
­ e Proposed Amendments to Appliance Efficiency Regulations (Express Terms), California Code of Regulations,
­

Title 20, Sections 1601 through 1608. California Energy Commission. November 2008. (Retrieved 12/17/08 from
­

http://www.energy.ca.gov/2008publications/CEC­400­2008­021/CEC­400­2008­021­15DAY.PDF)
­ f Table 1: Annual Estimates of the Resident Population for the United States, Regions, States, and Puerto Rico: April
­

1, 2000 to July 1, 2008 (NST­EST2008­01). Population Division, U.S. Census Bureau. Released December 22,
­

2008. (Retrieved 12/22/08 from http://www.census.gov/popest/estimates.php)
­

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The European Commission, as part of its Eco­design of Energy­using Products (EuP) 

Initiative, has established mandatory minimum energy performance standards for all singlevoltage EPSs with nameplate output power up to 250 watts sold anywhere in the European 

Union. The current standard levels are set to take effect in 2010 and are identical to those for 

Class A EPSs in the U.S. Exclusions include medical devices, battery chargers, uninterruptible 

power supplies, voltage converters, and EPSs for low voltage tungsten halogen lamps. The 

Commission has also set more stringent standards, which take effect in 2011.g 

The European Commission Joint Research Centre developed and administers the E.U. 

Code of Conduct on Efficiency of External Power Supplies, a voluntary agreement. Signatories 

to the Code of Conduct, which include major manufacturers of external power supplies, agree to 

meet active­mode efficiency and no­load power consumption targets for at least 90 percent of 

their product lines. The current targets, which took effect on January 1, 2009, are more stringent 

than those for Class A EPSs in the U.S. All single­voltage EPSs and battery charger wall 

adapters with nameplate output power between 0.3 watts and 150 watts are covered under this 

standard. 

g Commission Regulation (EC) No. 278/2009, Official Journal of the European Union. L 93/3 of April 6, 2009. 

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CHAPTER 2 TECHNOLOGY ASSESSMENT 

2.1 Introduction 

The following chapter of Technical Support Document (TSD) contains information that 

supports and expands on the Technology Assessment section of the Notice of Proposed 

Rulemaking (NOPR), which can be referenced for further information regarding the following 

topics: 

• Definitions 

• The Role of Power Converters 

• Efficiency Metrics 

• Product Classes 

• Overlapping Terminology 

Specifically, this technology assessment TSD chapter examines the functionality and 

design of non­Class A external power supplies (EPSs) with a focus on the components and 

subsystems that have the biggest impact on energy efficiency. DOE believes that there are four 

types of non­Class A EPSs: (1) multiple­voltage EPSs, (2) high power EPSs, (3) medical EPSs, 

and (4) EPSs for battery chargers (BCs). 

The chapter begins with a description of the functionality provided by external power 

supplies in the context of the system that they power. Meeting the functionality requirements of 

EPSs is the objective of the circuit design. To that end, the chapter continues by presenting the 

circuit designs that manufacturers typically use to achieve these specifications. Because the 

design of non­Class A EPSs has much in common with Class A EPSs, the assessment first 

discusses designs of Class A EPSs (such as unregulated, linear regulated and switched­mode 

regulated EPSs). DOE then presents the unique traits of each of the four types of non­Class A 

EPSs. Last, the chapter presents technology options for improving the efficiency of non­Class A 

EPSs. 

2.2 Functionality of Non­Class A EPSs 

2.2.1 Particular Functionality of Multiple­Voltage EPSs 

This class includes both devices that provide power at more than one distinct voltage to a 

consumer product as well as devices that have one power level, but one or more signal 

connections to the consumer product. All the multiple­voltage external power supplies that DOE 

has analyzed to date provide a regulated DC voltage at each power “output bus,”a although a 

multiple­voltage AC/AC power supply is also a technological possibility. Similarly, although it 

is technically possible for multiple­voltage EPSs to have any number of outputs, DOE is only 

aware of dual­output EPSs in use with commercial products. 

a An “output bus” is a pair of conductors used to transfer power from the EPS to a consumer product, as opposed to 

a pair of conductors used to transmit a data signal. For example, an EPS may have two pairs of conductors—a 

power output bus and a pair used to transmit a “standby” signal, causing the EPS to enter a low­power state when 

the product is not using the EPS. 

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Although EPSs in this class provide multiple voltages simultaneously, they are designed 

to power a single consumer product. The wires that comprise the multiple output busses are 

typically contained within a single cable with a single output connector with multiple terminals 

or pins. The output busses provide power to the various subsystems within the consumer 

product, each of which has a particular voltage requirement that depends on its own function and 

components. 

Multiple­function devices use multiple­voltage EPSs to provide a dedicated voltage to the 

ink cartridges, called “pens,” and use a second voltage for all other functions (logic, print­engine 

motors, etc...) Multi­function devices are combination­printers that allow the user to scan, print, 

copy, and/or fax documents in addition to standard printing functions. 

Video­game consoles rely on multiple­voltage EPSs for a different reason. Because of 

their compact size, video­game consoles may use an EPS to minimize space constraints and heat 

exposure to the main console. In addition manufacturers use an external power supply to limit 

the number of products requiring UL recognition. The UL process adds to the cost of the unit and 

can take six to nine months to complete. This allows manufacturers to save money and time. In 

the topology of the video­game EPS there is an additional 5 V output for operation of the game 

console in a “standby”b mode. This output, which is provided by a separate transformer core 

within the EPS, provides all the power required by the product during standby, allowing the rest 

of the EPS to shut down. 

2.2.2 Particular Functionality of High­Power EPSs 

High­power EPSs are a fixture in any electronics laboratory and are sometimes used for 

commercial applications such as audio recording and processing and powering illuminated signs. 

However, as mentioned in the market assessment section of the NOPR, the primary consumer 

application of these EPSs is powering communications equipment, in particular amateur or 

“ham” radios. These radios are capable of transmitting information across the country and, given 

sufficient power, even around the world. Ham radios are mostly a hobby item for those wishing 

to communicate with others; however, these radios can be of particular importance in cases of 

emergency, for example, when natural disasters have disabled other means of communication. 

Although they range in power from 100 W to over 1 kW,c EPSs for ham radio 

applications provide a DC output at 13.8 V, allowing ham radio users to operate mobile 

equipment intended for use in a vehicled in a stationary location. Unlike stationary ham 

b This standby mode and the device mode that it enables should not be confused with the standby mode of the EPS, 

which is defined as the condition where the power supply is connected to mains, is disconnected from the load, and 

has any manual on­off switches in the on position. 

c EPSs for ham radio applications with output power less than or equal to 250 W are common, but are outside the 

scope of this determination analysis and are covered under DOE’s energy conservation standards for Class A EPSs. 

d Although lead­acid automobile batteries have a nominal voltage of 12 V, the voltage provided by the alternator 

must be higher to maintain the charge of the battery. Thus, when the car is running, the voltage across the battery 

ranges between 13 V and 15 V depending on alternator charge current, battery chemistry, and temperature, with 

13.8 V as a nominal value. D. Linden and T. Reddy. Handbook of Batteries. Third Ed. New York: McGraw­Hill, 

1995. pp. 23.68–23.75. 

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equipment, mobile equipment does not include an internal power supply because it was designed 

around the availability of DC power from a vehicle’s electrical system. Therefore, when this 

equipment is taken out of the vehicle, an EPS is required. 

Even though this ham radio equipment is mobile, it is not exactly portable: users are not 

expected to travel extensively with the transmitters and power supplies, unlike in the case of 

laptop computers. As a result, EPSs for radio applications tend to be larger and heavier than 

those for other consumer applications, when compared at output powers below 250 W. 

Because high­power EPSs are primarily used in communication applications, 

electromagnetic interference, or “noise,” impacts their functionality. The Federal 

Communications Commission (FCC) has regulations for electromagnetic compatibility (EMC), 

which limit interference from consumer products, such as high­power EPSs. Although 

manufacturers of high­power EPSs ensure that their products comply with these regulations, ham 

radio receivers have excellent sensitivity, enabling reception of very weak electromagnetic (EM) 

signals. Having a local noise source, such as a switching supply, can interfere with reception. 

As a result, the electronic noise generated by an EPS, however small, can couple to the radio 

receiver affecting its utility, and at high enough levels become an audible buzzing sound or a 

constant hum. The local emissions will also act to reduce the gain of the receiver if they are 

stronger than the desired signal. The receiver gain is determined by the strongest signal. This 

happens because of adaptive receiver behavior (automatic gain control). Noise is therefore an 

extremely important consideration that influences the EPS design. In EPSs significantly over 

100 W, it is possible to dramatically improve EMI suppression for a minimal increase in cost or 

efficiency. Doing so calls for a higher level of inductance in the common mode chokes (see 

section 2.2.5 for more detail). Most designers only design their ham radio EPSs to just meet 

FCC requirements, but technology exists that can cost­effectively eliminate the issue of 

interference in ham radios. As a result, line­frequency EPSs, which generate much less EM 

noise than switch­mode EPSs, are still used to a greater degree in amateur radio field setups. 

2.2.3 Particular Functionality of Medical EPSs 

Interviews with EPS manufacturers indicate that external power supplies used with 

medical devices, unlike Class A EPSs used with commercial information technology and 

entertainment (ITE) equipment, have additional requirements for use in a medical setting. One 

difference is that medical devices have longer lifetimes than other electrical products. Another 

requirement comes from the Food and Drug Administration, which regulates medical equipment 

under the Federal Food, Drug, and Cosmetic Act. The act stipulates that all medical devices 

must be safe and effectivee

. Although the FDA does not specify a single safety certification, 

safety is typically conferred by Underwriters Laboratory (UL), the major product safety 

certification organization in the United States. Overall, the additional requirements of medical 

EPSs affect their price, but have limited impact on achievable efficiency. 

e SEC. 513. [21 USC 360c ] – taken Sept. 4th 2008 from http://www.fda.gov/opacom/laws/fdcact/fdcact5a2.htm 

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2.2.3.1 Lifetime of Medical EPSs

Electronic medical devices are typically used for a period of as few as 5 years to 10 years 

or more, whereas consumers tend to use commercial ITE equipment for 1 to 4 years. Further, 

medical devices are often in use continuously as opposed to commercial products that operate at 

a maximum of 8 hours per day. During operation, medical EPSs typically operate at 75% to 

80% of their maximum rated output. Another consideration is the hold­up time of the EPS – 

how long it can provide output power during an interruption of its input power. Medical EPSs 

can have hold up times of around 50 ms as compared to EPSs for ITE products that have hold up 

times of just a few milliseconds. Most importantly, the consequences of a medical EPS failing 

are much more dire than for EPS for ITE products. When commercial equipment fails the 

consumer may be frustrated and upset; however, if a medical device were to fail it could result in 

injury or possibly death. Therefore, medical EPSs are more stringently designed not to fail over 

longer lifetimes and under continuous operating conditions than general EPSs. 

2.2.3.2 Safety Concerns of Medical EPSs

Another design consideration is safety. In the United States, medical EPSs must be 

proven safe, typically through certification under the Underwriters Laboratory 60601­1 standard, 

which is based on the internationally­harmonized standard IEC 60601­1, developed by the 

International Electrotechnical Commission (IEC). The primary philosophy of the standards is to 

ensure equipment safety in normal operating conditions and during a single fault condition. An 

example of a normal operating condition is that the consumer accidentally plugs in the EPS with 

reverse polarity of the mains supply. An instance of a single fault condition is failure of 

electronic components, one at a time. These standards are more stringent than those for general 

commercial equipment because medical patients may not be able to respond to electrical shocks 

or pain, there may be an electrical connection to the patient, and some medical devices provide 

life support, so their failure could result in the death of the patient. 

Similar to other electrical products, medical products have the option of using either an 

internal power supply or an external power supply. External power supplies offer the benefits of 

reducing the size of the medical device and reducing the safety requirements of the medical 

device, by placing it on the EPS. The size is reduced by placing the power supply circuitry 

outside the housing for the medical device. As compared to general EPSs, UL 60601­1 requires 

medical EPSs to have wider distances between the primary and secondary sides of the circuit for 

added safety, resulting in physically larger circuits. Furthermore, products that connect directly 

to mains must use tougher, more expensive materials to reduce the risk of failure. An EPS will 

isolate the medical devices from mains and, thus, reduce the device’s safety requirements. This 

benefit can be particularly useful for medical devices that deal with fluids. Those medical 

devices may use an EPS with a short, 2 ft. AC input cord and a long 10 – 15 ft. DC output cord, 

whereas an EPS for ITE applications could have input and output cords that are both 3 ft. long. 

These cord lengths increase the safety of the medical device by increasing the separation of the 

device and its fluids from mains power. 

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2.2.3.3 Levels of Protection under UL 60601­1

UL 60601­1 applies both to medical devices as well as their external power supplies. For 

medical EPSs, the primary concern is protection from electrical hazards in the circuit design. 

The standard stipulates that there must be two levels of protection against an unintentional 

leakage current passing through the patient. This current could pass between a live part 

connected to mains and an applied part that might contact the patient. The patient must be 

protected if they are accidentally grounded or accidentally connected to mains. The levels of 

protection can be (1) insulation to separate the patient from mains, (2) protective impedance to 

limit the current that can flow to a patient, or (3) protective earth that provides current a direct 

path to ground, rather than through the patient. 

For the insulation barriers, UL 60601­1 specifies spacing distances and dielectric 

withstand voltages, based on the input voltage of the EPS. The distances specify how close the 

primary and secondary sides of the circuit can be. For example, with a 125V input voltage, a 

circuit is considered to have “basic insulation” if the primary and secondary are separated by 3 

mm of creepage distance and 1.5 mm of air clearance. In addition, the dielectric separating the 

two sides is required to withstand a 1 kV drop across it. EPSs are often designed for universal 

input power, in which case the insulation barriers meet the more stringent requirements 

associated with 250 V, the European AC input voltage. 

The EPS could also use protective impedance as a level of protection. The impedance 

would act to limit the maximum current to the patient to 10 �A or 100 �A, depending on the 

specification requirements. 

Depending on the design, medical EPSs can also use a protective earth and are classified 

as either Class I or Class II. Class I EPSs have a protective earth connection, such as a metal 

enclosure, that is that tied to the ground pin of a three­pronged power plug. Class II EPSs do not 

have a protective earth, and instead use insulation as a layer of protection. In the United States, 

the protective earth must pass 15A or 1.5 times the nameplate current for 5 seconds. In Canada, 

the protective earth must pass 30 A or 2.0 times the nameplate current for 2 minutes. Typically, 

manufacturers of U.S. products test the protective earth with the Canadian requirement since 

most products are common between the two countries. 

2.2.3.4 Output Voltages of Medical EPSs

Another safety requirement for medical EPSs is lower output voltages. EPSs for ITE 

products can have a DC output voltage as high as 60 V. However, medical EPSs do not go 

above 30 V to have a safety extra low voltage (SELV). However, it is possible for medical EPSs 

to have higher output voltage, but that would require additional levels of protection. Typically, 

medical EPSs have an output voltage between 18 V and 30 V. 

Some medical EPSs have two or more output voltages. Multiple voltages are useful 

when there are different voltage requirements for different circuits within the medical device. 

For instance, logic circuits might require voltages around 3.3 V to 5 V whereas a pump or motor 

might require 12 V to 30 V. Currently, the trend is that manufacturers prefer single­voltage 

medical EPSs over multiple­voltage ones. This is because there is an increasing amount of logic 

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circuits in medical devices, each with a different voltage requirement. Consequently, it becomes 

less attractive for the medical EPS to have an increasing amount of output voltages. Rather it’s 

simpler to have an EPS with one high output voltage and many local DC­DC converters within 

the product for smaller voltages. Nonetheless, multiple­voltage EPSs continue to be used with 

legacy products as well as products with motors and pumps, which consume large amounts of 

power and require isolation from logic circuits. In terms of energy efficiency, multiple­voltage 

medical EPSs face the combined challenges of multiple­voltage ITE EPSs and single­voltage 

medical EPSs. 

2.2.3.5 Leakage Currents in Medical EPSs

In addition to having levels of protection and lower output voltages, medical EPSs have 

restrictions on leakage currents. The limits depend on the type of leakage current, the operating 

condition, the degree of protection against electric shock, and the type of medical equipment. 

The leakage current can be through the ground pin, to ground via the patient from the enclosure, 

or to ground through the patient from an applied part. For the operating conditions, the 

maximum allowable leakage current is lower in the normal condition than in the single fault 

condition. The degrees of protection are classified as type B, BF, or CF. Type B provides a 

basic degree of protection and the applied part may be directly connected to ground. Type BF 

has a higher degree of protection, where the “F” indicates that the circuit is floating with respect 

to ground. Type CF is typically used with cardiac applications and offers even more protection; 

again, the “F” denotes that it is floating. Patient care equipment and portable equipment are two 

types of medical equipment, each with different ratings for leakage current. 

For example, Table 2.1 shows the maximum leakage currents for portable equipment. 

The table indicates that for a Type BF device in the normal condition, 100 �A is the maximum 

current that can flow through the patient from the enclosure or from the applied part. If the 

device were type CF, the enclosure limit would still be 100 �A, but the maximum leakage 

current from the applied part would be 10 �A, which is very restrictive. 

Table 2.1 Maximum Leakage Current for Portable Equipmentf 

Leakage 

Current 

Type B Type BF Type CF 

Normal 

Condition 

Single 

Fault 

Condition 

Normal 

Condition 

Single 

Fault 

Condition 

Normal 

Condition 

Single 

Fault 

Condition 

Earth 

Leakage 

Current 

500 uA 1 mA 500 uA 1 mA 500 uA 1 mA 

Enclosure 

Leakage 

Current 

100 uA 500 uA 100 uA 500 uA 100 uA 500 uA 

Patient 

Leakage 

Current 

100 uA 500 uA 100 uA 500 uA 10 uA 50 uA 

f Taken in September 2008 from http://www.xppower.com/page.php?pagename=Medical&lang=EN 

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The medical device could cause leakage current to flow through the patient in two ways: 

the patient could be connected to ground or connected to mains power. The mains connection 

could happen due to a complete failure in another piece of equipment. A connection to mains 

will not harm the patient as long as the patient remains isolated from ground so that no current 

flows. The patient could be connected to mains due to failure in another medical device or 

simply from the patient contacting liquid that touches a grounding source, such as a cold water 

tap. The medical EPS must not exceed the leakage current limits in either scenario. 

In the design of medical EPSs, the tighter leakage current limits trade off with more 

lenient electromagnetic compatibility (EMC) requirements. There are two classes of EMC: 

Class A, for industrial and medical applications, and Class B, for commercial applications. As 

compared to ITE products, medical products have more lenient EMC limits. However, another 

concern for medical EPSs is the ranges of frequencies to avoid, known as keep out frequency 

ranges. For example, several major medical equipment manufacturers have established such 

ranges to ensure that the power supply switching frequency does not interfere with ultrasound 

equipment. 

2.2.3.6 Maintaining Safety Certification

To obtain safety certification, the EPS must document that it meets all of these safety 

requirements. Some manufacturers need up to a year to complete the testing and documentation. 

Once certification is achieved, the EPS design is fixed. No component can be changed without a 

justification and re­certification of the entire EPS. 

2.2.4 Particular Functionality of EPSs for BCs 

In its framework document for BCs and Class A EPSs, DOE describes different 

approaches for considering a BC wall adapter to be an EPS for BC.g Specifically, DOE is 

considering Approach A which considers BC wall adapters with constant­voltage output to be 

EPSs for BCs. In that case EPSs for BCs have the same electrical characteristics as Class A 

EPSs; the only difference between the EPSs is their end­use applications. 

2.2.5 Electromagnetic Interference Suppression 

There are two types of EMI when dealing with external power supplies. The two 

categories of interference are differential mode and common mode noise. What distinguishes the 

two is the manner in which the interference is manifested in the circuitry and transmitted to AC 

mains. Since the two types of noise develop differently, designers have different solutions that 

reduce the effects of the noise that is generated. The FCC and European entities established 

electromagnetic interference (EMI) limits among those frequencies allocated to commercial 

broadcasting and to short wave transmissions used for communication purposes. 

g U.S. Department of Energy­Office of Energy Efficiency and Renewable Energy. Energy Efficiency Program for 

Consumer Products: Public Meeting and Availability of Framework Document for Battery Chargers and External 

Power Supplies. Federal Register. June 4, 2009. vol. 74, No. 106: p. 26816. 

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Differential mode noise is associated with the switching frequency of an EPS as well as 

the first few upper, odd harmonics of that frequency. Those harmonics that fall into the 

broadcast bands are the frequencies of most concern. The general range of the broadcast band is 

550 kHz to 1650 kHz and is the broadcast band of AM radio. To suppress the effects of this type 

of EMI designers may add one or two, non­polarized capacitors (or “X” capacitors) across the 

AC mains input and an inductor filter (or differential­mode choke) in one of the AC input legs 

can help reduce the noise. Figure 2.1 shows the circuit diagram of an EMI filter that employs 

two “X” capacitors, C1 and C2, and a differential­mode choke, L2. 

The second type of noise, common mode noise, is created throughout the EPS circuitry. 

It occurs when fast rising pulses are coupled, via parasitic capacitance and inductance to other 

circuit elements and incoming AC wiring separate from the switch. Parasitic capacitance is the 

stray, unavoidable capacitance that exists between circuit elements. Common mode interference 

is generally seen at frequencies from 1 MHz up to 30 MHz. To combat this interference 

designers use a common mode choke on the AC input lines and a capacitor connected from each 

of the AC lines to ground, called a “Y” capacitor. Figure 2.1, shows the circuit diagram of an 

EMI filter that employs a pair of Y capacitors, C3 and C4, and a common mode choke, L1. 

Figure 2.1 Example Circuit of an EMI Filter 

Parasitic capacitive coupling among components can cause interference to be radiated 

around the common mode choke and appear at AC mains. To avoid this, sometimes an EMI 

filter like that shown above can be placed externally to the EPS. This filter is placed between the 

AC main power and before the input to the EPS. That way AC main power can only enter the 

EPS after passing through the filter. 

When designers make these additions to their EPSs, cost and size are the two most 

important considerations. To stay competitive, EPS manufacturers want to keep both of these 

characteristics to a minimum, while also meeting necessary EMI standards. The impact of 

additional cost and size of these electrical components becomes greater for EPSs with higher 

output powers. This is especially true of the “X” capacitors and both choke cores, whereas the 

size and cost of the “Y” capacitors will remain relatively constant. For example if the value of 

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the common mode and differential mode choke were to triple, the physical size could be as much 

as 10 times larger and 5 to 7 times as expensive. 

The FCC and the European Union (EU) have set limits for electromagnetic interference. 

The European standards are more stringent than those set by the FCC and are generally the 

specifications that manufacturers, even those in the United States design to. The reason U.S. 

EPS manufacturers still use the EU limits is that their products are designed for possible global 

consumption. For this reason, many U.S. products have labels declaring conformity with the 

standards set forth by the EU in EN 55022. 

The issue of noise is of particular importance for high power EPSs used in ham radio 

applications and is discussed in detail in section 2.3.10 below. 

2.3 Circuit Design of EPSs 

2.3.1 General Design of an External Power Supply 

EPSs must meet several specifications in order to power a consumer product; EPSs are 

generally designed to provide power at a fixed output voltage with variable current to a 

consumer product. The consumer product is what determines the EPS design criteria, including 

output power, output voltage, and the tolerance of the output voltage. EPSs designed for 

consumer products that require precise voltages (e.g., computers) will also incorporate output 

voltage regulation to minimize voltage fluctuations caused by load or power source variations. 

Other applications that can tolerate some voltage fluctuation may use simpler EPSs that do not 

regulate the output voltage. Also, EPSs might have other specifications, such as total harmonic 

distortion or power factor. 

Of all these specifications, output power and output voltage have the largest impact on 

EPS efficiency, because together they determine the output current, which directly affects 

conduction losses and associated power dissipation in the EPS. 

External power supplies can have different topologies for power conversion and 

regulation (Figure 2.2). Line­frequency EPSs have that name because the frequency of the 

current passing through their transformers is the same as that of the AC mains current (nominally 

60 Hz in the United States). Switched­mode power supplies (SMPS) convert power differently 

than line­frequency EPSs. SMPSs first rectify the AC mains voltage to DC, converting it to 

pulsating DC by switching the current on and off at high frequency. The high­frequency 

pulsating DC current passes through the primary winding of a transformer where it appears as a 

high frequency AC voltage. The high frequency output from that secondary winding of the 

transformer is rectified by high frequency diodes, resulting in a low­voltage DC output. Because 

the pulsating current passing through the transformer is at high frequency, the transformer is 

smaller, resulting in lower weight, material costs, and losses in the transformer, all of which 

decrease with transformer volume. 

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GENERAL EXTERNAL POWER SUPPLY TOPOLOGIES
­

POWER CONVERSION REGULATION TYPE 

Line­Frequency Unregulated 

Linear­Regulated
­

Switched­mode
­ SwitchingRegulated
­

Figure 2.2 Topologies for External Power Supplies 

2.3.2 Design Choice: Single Versus Multiple Voltage EPSs 

Consumer electronic products often use external power supplies and typically require 

different voltages within the product. As can be seen in Figure 2.3 the multiple voltages can be 

generated either inside the EPS or inside the consumer product. If generated inside the consumer 

product the EPS typically provides only a single output voltage (Figure 2.3b). Sometimes all of 

the voltages are generated outside the product, as in Figure 2.3a, or the design involves a 

combination approach with a multiple­voltage EPS and additional voltage regulation within the 

product (Figure 2.3c). 

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Multiple DC

AC Mains Multiple­Voltage

AC Subsystems

Subsystems

EPS Consumer

Product

a. 

Single DC

AC Mains Class A SingleAC Volt. Reg.

Volt. Reg.

Subsystems

Subsystems

Voltage EPS Consumer

Product

b. 

Multiple DC

AC Mains Multiple­Voltage

EPS

AC Volt. Reg.

Volt. Reg.

Subsystems

Subsystems

Subsystems

Consumer

Product

c. 

Figure 2.3 Power Distribution Configurations for Consumer Products With Subsystems 

Requiring Different Supply Voltages 

There is an increasing trend for consumer electronic products that use external power 

supplies, to use single­voltage EPS and create any additional voltages inside the consumer 

product itself with DC­DC converters. Because of this most consumer electronic products for 

sale today either use internal power supplies or a single­voltage power supply, followed by one 

or more voltage regulators. However, there remain two important consumer applications that 

continue to use multiple­voltage EPSs: video­game consoles and printing applications, which are 

discussed in section 2.2.1. In addition, DOE is aware of external hard drives, inkjet printers, 

security equipment and medical equipment that also might use multiple­voltage EPSs, although 

their use is uncommon. 

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2.3.3 Class A AC/AC External Power Supplies 

An AC/AC external power supply, a type of Class A EPS, is the simplest type of EPS, 

typically consisting only of a transformer and only one output voltage. A transformer contains 

two wires, each wrapped a number of times around a metal core, and as current passes through 

the primary wire, power is transferred to the secondary wire at a lower voltage through magnetic 

induction in the core. The size of the wires and core depend on the output power of the 

transformer. The output voltage is dependent on the turns ratio, which is the ratio of the number 

of times the primary wire is wrapped around the metal core to the number times the secondary is 

wrapped around the metal core. The windings of the transformer are wound so that the voltage 

generated in the secondary wire is at the design voltage for the consumer product when mains 

voltage is applied to the primary wire. Because the primary and secondary windings are two 

separate wires, the transformer also provides a safety function, electrically isolating the 

consumer product from the mains. The key factors that determine transformer losses are core 

size, core material, number of windings, and wire gauge. 

Figure 2.4 Circuit Diagram for an AC/AC External Power Supply 

2.3.4 Class A Unregulated Line­Frequency AC/DC External Power Supplies 

An unregulated line­frequency EPS is referred to as a “raw supply,” which has three 

distinct stages (Figure 2.5): a transformer to isolate and step down mains voltage, a rectifier to 

convert AC voltage to a pulsating DC voltage, and a filter capacitor to smooth the output voltage. 

The two main sources of loss are the transformer and the rectifying diodes. After passing through 

the transformer, current passes through rectifier diodes, which have voltage drops that also 

dissipate power. Typically, diodes have a drop of 0.8 –1.2 volts, if Schottky diodes are used 

these drops are less, around 0.6 volts. These drops constitute a proportionally larger share of the 

losses at lower output voltages. For AC­DC EPS that have a low output voltage, below 

approximately 12 V, the power consumed by the diodes also becomes significant in that it is 

more than 10% of losses, if the rectifier is a bridge with two diodes. 

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Figure 2.5 Circuit Diagram of a Line­Frequency Raw Supply 

The raw supply is directly responsive to the load: A change in the mains power or the 

resistance of the load directly affects the output voltage of the raw supply. If required, a regulator 

circuit follows the raw supply circuit, housed either in the EPS or in the device before the load. 

2.3.5 Class A Linear­Regulated Line­Frequency AC/DC External Power Supplies 

To achieve voltage regulation, manufacturers can add a second stage, such as a linear 

regulator, to the line­frequency power conversion stage described above, or redesign the power 

conversion stage entirely using a switched­mode topology. Of the two regulator technologies, 

linear regulators are simpler, bulkier, cheaper, and generally less efficient at higher power levels 

than switching regulators. Switching regulators, although more complicated and costly, provide a 

good alternative when portability is a concern, such as when an EPS is used with a mobile 

phone. 

The AC­DC conversion stage of a regulated line­frequency EPS is essentially the same as 

that of an unregulated EPS, with the same sources of power consumption. The linear voltage 

regulation stage adds to these losses by passing power from the AC­DC converter to the 

consumer product through a power­dissipating element. This regulation stage senses the output 

voltage and adjusts the voltage across the power­dissipating element to keep the output voltage 

fixed. Loss in a regulated line­frequency EPS is caused by the conversion stage delivering 

current at a higher voltage than needed by the consumer product, and dropping the excess 

voltage across the regulator to achieve the lower regulated output voltage. Dissipated as heat, the 

power lost in the regulator is the product of the voltage drop and the load current. 

Linear regulators have two key elements: a sensor and a pass device, which work 

together to produce a fixed output voltage (Figure 2.6). To determine those adjustments, the 

sensor element continuously compares the output voltage to a reference voltage. Whenever there 

is a difference between the two voltages, the sensor directs the pass device to adjust the output in 

order to reduce that difference. This continuous adjustment allows the regulator to yield a 

constant output voltage as the load resistance or mains voltage varies. The output voltage of the 

linear regulator circuit is what the user sees as the output voltage of the EPS. 

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Figure 2.6 Block Diagram of a Linear Regulator 

Figure 2.7 shows a circuit diagram of a “low­dropout” linear regulatorh

, one of the more 

common types of linear regulators. To determine the voltage drop across the pass device, an 

operational amplifier (commonly referred to as an “op­amp”) acts as a sensor that compares the 

output voltage against a reference voltage. Based on those two signals, the op­amp controls a 

transistor, which is the pass device. The voltage drop across the transistor determines the output 

voltage but also dissipates energy. The energy dissipated by the pass device is the main source of 

energy consumption in the linear regulator, and hence the main source of inefficiency and heat 

generation. Together, the sensor and the pass device adjust the output of the regulator to produce 

a stable output voltage, which is what the load receives as the output voltage of the EPS. 

Figure 2.7 Simplified Circuit Diagram of a Linear Regulator 

The efficiency of the linear regulator, ηLinReg, is: 

h Low dropout simply means the minimal voltage drop across the regulator at its maximum current rating. A low 

dropout regulator has very low voltage drop at maximum current and can therefore be very efficient at that point. 

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P V I LinReg _ out LinReg _ out LinReg _ out η = = Eq. 2.1 LinReg P V I LinReg _ in LinReg _ in LinReg _ in 

where	­ILinReg_in is the current into the linear regulator,
­

ILinReg_out is the current out of the linear regulator,
­

PLinReg_in is the power into the linear regulator,
­

PLinReg_out is the power out of the linear regulator,
­

VLinReg_in is the voltage into the linear regulator, and
­

VLinReg_out is the voltage out of the linear regulator.
­

Because the linear regulator directly attaches to the raw supply, VLinReg_in is equal to 

VRawSupp_out, the output voltage of the raw supply. 

Because the input current flows directly to the output through the pass device, with other 

currents being negligible, I ≈ I _ in . Therefore, the efficiency of the linear regulator LinReg _ out LinReg 

alone is approximately: 

VLinReg _ out η ≈ Eq. 2.2 LinReg VLinReg _ in 

The total efficiency of an EPS with a linear regulator depends on the efficiency of both 

the linear regulator stage and the raw supply stage. Depending on the load conditions, ηLinReg 

generally ranges from 0.6 to 0.8, meaning the linear regulator is about 60 to 80 percent efficient. 

The efficiency of raw supply, ηRawSup, also varies with load, generally from 0.7 to 0.9. The raw 

supply and linear regulator each are most efficient at different load conditions. Multiplied, ηLinReg 

and ηRawSupp yield the total efficiency of an EPS with a linear regulator, ηLin_EPS, which is 

generally about 50 percent, but is lower for EPSs with output power below 10 W: 

η =η *η	 Eq. 2.3 Lin _ EPS RawSupp LinReg 

2.3.6	­ Class A Switching­Regulated Line­Frequency AC/DC External Power Supplies 

An alternate to a linear regulator is a switching regulator that can also follow the raw 

supply (Figure 2.8). Switching regulators tend to be much more efficient than linear regulators 

because they do not dissipate excess power. Rather, to regulate output they take power as 

necessary to maintain constant output voltage. Due to their higher costs, these switching 

regulators tend not to be as common as linear regulators as an auxiliary regulator, since it is 

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typically more cost­effective to use a switched­mode power supply design in the first place, in 

which case there is no need for an auxiliary regulator. 

Figure 2.8 Block Diagram of a Switching­Regulated Line­Frequency AC/DC EPS 

2.3.7 Switched­Mode AC/DC External Power Supplies 

A switched­mode power supply consists of five stages: a 60Hz AC­DC conversion stage, 

a high frequency chopper stage, an energy transfer stage, a control stage, and an electricallyisolated feedback stage (Figure 2.9). First, the current is rectified and passed to the chopper, 

which converts the 120­Hz­pulsing DC voltage to pulsing DC, but at high frequency. The energy 

transfer stage (transformer) then takes energy from the chopper, briefly stores it, reconstitutes it 

as high frequency AC and then passes it to the rectifier to be the output to the consumer product. 

The energy transfer stage also serves to isolate the user from the mains. The level of the output 

voltage is fed back through a feedback isolation stage to the controller, which tracks the output 

voltage and adjusts the chopper duty cycle or frequency to set the desired voltage. 

Figure 2.9 Block Diagram of a Switched­Mode Power Supply 

The critical elements in a switched­mode EPS are the transistor, output rectifier, bulk 

capacitor, transformer, and controller. A transistor acts as a switch that constrains the flow of 

power rectified from mains into the transformer (or choke), through the output rectifier, and, 

ultimately, to the consumer product. A controller, typically an integrated circuit (IC), switches 

the transistor on and off based on the output voltage. By adjusting the duty ratio, the IC controls 

the rectified mains current into the primary winding of the transformer and thereby the output 

voltage of the EPS. The IC can also limit power dissipation in active mode by reducing 

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switching at low current or low voltage. Further, the IC can greatly increase efficiency by 

reducing power consumption in no­load mode, the condition when the EPS has been 

disconnected from the load, resulting in zero output current. After passing through the 

transformer, the current is rectified and filtered before reaching the consumer product. Principal 

sources of loss in a switched­mode EPS are the transistor on­state resistance and capacitive 

switching dissipation, magnetization, and resistive losses as a result of transformer current, 

controller IC power consumption, and rectifier losses. Although there are more sources of loss 

for switched­mode EPSs than line­frequency EPSs, in total, losses in switched­mode EPSs tend 

to much lower. 

The switching regulator usually consists of an integrated circuit controller and discrete 

components. The circuit diagram in Figure 2.10 depicts a “flyback” switching regulator, the most 

common type for EPSs used with consumer electronics; however, many other switching 

regulator designs also exist. The AC/DC conversion stage consists of a diode bridge and filter 

capacitor, similar to a raw supply. In this case, current flows directly from mains to the diode 

bridge, rather than through a transformer. 

The chopper stage uses a transistor, which switches on and off at high frequency to 

convert the DC current from the AC/DC converter back to a pulsating DC current for the energy 

transfer stage. A control stage drives the transistor; the duty cycle of the transistor determines 

how much energy is transferred through the energy transfer stage. The switching frequency is in 

the kilohertz range, with lower frequencies having lower switching losses. The minimum 

frequency is virtually always 20 kHz (typically above 50 kHz) above the audible range of human 

hearing. 

Figure 2.10 Simplified Circuit Diagram of a Flyback Switching Regulator 

The energy transfer stage consists of a transformer, a capacitor, and a diode. The choke is 

similar to a transformer and has the same symbol in the circuit diagram. One difference is that a 

transformer in a line­frequency EPS using a forward converter topology is designed to pass 

energy from one winding to another with minimal energy storage, while a transformer in a 

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flyback­topology switched­mode EPS is designed to store and release energy, similar to a way a 

choke. A typical forward converter requires a transformer but also an output filter choke. The 

less expensive flyback accomplishes the transformer and choke function in one component. The 

flyback approach creates additional undesirable output ripple that is typically acceptable in lower 

cost EPS units. Also, the phasing of the windings is not important in the line­frequency 

transformer, but it is critically important in the flyback switching regulator. This is represented in 

Figure 2.10 by dots on the transformer. 

When the chopper switch is closed, the primary winding of the transformer takes energy 

from the chopper and stores the energy in the transformers. When the chopper switch opens, the 

secondary winding transfers that energy through the diode to the capacitor and provides the 

output for the switching regulator, electrically isolating the load from the mains. Because the 

transformer operates at a high frequency, it benefits from the associated decreases in size and 

weight. The energy transfer scheme of the switching regulator is more efficient than a linear 

regulator, in part because the transformer, doubling as a choke, stores and returns energy with 

relatively low losses. 

The feedback isolation stage typically uses an optocoupler that consists of a light source 

and a photosensitive detector. By converting the electrical feedback signal to an optical one, the 

optocoupler maintains the load electrically isolated from the mains. The detector converts the 

optical signal back to an electrical signal for the controller. 

Generally, the controller is an integrated circuit that drives the chopper with a highfrequency pulse­width­modulated (PWM) waveform. The controller monitors the EPS output 

voltage and adjusts the pulse width to increase or decrease the amount of energy transferred by 

the chopper. If the output voltage dips, the controller will increase the duty cycle, thus increasing 

the energy passed by the energy transfer stage and increasing the output voltage. Conversely, if 

the output voltage rises, the controller will decrease the duty cycle or possibly skip cycles. This 

cycle­skipping feature is especially useful at low­load or when there is no load attached, because 

the EPS will only take from the mains the small amount of power it needs to keep itself running. 

As an alternative to an IC controller, a switched­mode EPS can also use discrete 

components, as in the case of a ringing choke converter. In that topology, discrete transistors 

control the chopper and the resulting energy transfer. EPSs without ICs tend to be more common 

at lower output powers. However, by not having an IC, the EPS may consume less overhead 

power, but offers less functionality, such as cycle­skipping at low load, which can limit EPS 

efficiency. 

2.3.8 Design of Output Cables 

Cable losses are related to the output power and output voltage of the external power 

supply as well as the resistance of the output cable, based on its materials, length, and gauge. 

This relation can be expressed in the following equation: 

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2  P 

2 

OUT P  LOSS = IOUT R =  R , Eq. 2.4   VOUT 

where PLOSS is the power lost in the output cable, 

IOUT is output current, power, voltage, 

POUT is the output power, 

VOUT is the output voltage, and 

R is the cable resistance. 

2.3.9 Particular Designs of Multiple­Voltage EPSs 

As described previously, multiple­voltage external power supplies can be divided into 

two different groups by number of output busses capable of delivering power to the load. The 

first group, which has only one output bus and one or more auxiliary signal outputs, are designed 

fundamentally the same as single­voltage external power supplies: the power conversion process 

is the same, but the EPS contains additional circuitry that provides the added signal outputs 

necessary for device operation. Although this signal circuitry is not in the power conversion 

path, it requires power to perform its function, affecting the efficiency of the EPS. Therefore, the 

strategies for improving the efficiency of this group of multiple­voltage external power supplies 

would focus on improving the efficiency and no­load power of the power­conversion process, as 

analyzed for single­voltage EPSs and/or reducing the power consumption of the circuits driving 

the auxiliary outputs. However, the power supplies in this group do not appear to be in the 

market; therefore they were not analyzed further in this determination analysis. 

The other group consists of EPSs that, in addition to any auxiliary signal outputs, have 

multiple power outputs at two or more voltages that operate load subsystems with differing 

supply voltage requirements. These EPSs power applications such as multi­function devices and 

video­game consoles, and can generate their multiple output voltages in several different ways: 

(1) through additional regulators connected to a single tap, (2) through multiple taps of a single 

transformer winding, (3) through multiple windings on a single core, and (4) through multiple 

cores. 

In each of the approaches—described in detail below—the power conversion stage 

utilizes either a line­frequency or switched­mode high­frequency design. Similarly, in the case 

of a line­frequency power conversion stage, voltage regulation at the output can be performed 

either not at all (e.g., in the case of an AC­AC EPS) or using linear or switching voltage 

regulators. 

2.3.9.1 Additional Regulators from a Single Tap

Topologically, this circuit approach is similar to using a single­voltage EPS followed by 

post­regulation, except the voltage post­regulators are located inside the external power supply 

rather than the consumer product. Although employing this approach as opposed to the one in 

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Figure 2.3.b may decrease the size of the consumer product, it has numerous disadvantages such 

as a thicker and heavier output cable with multiple conductors, higher losses in the output cable, 

and higher minimum tolerances on the output voltage, such that this approach is not commonly 

seen in practice. 

2.3.9.2 Multiple Taps

In its simplest form, a transformer couples the magnetic flux in a pair of windings, 

relating the AC voltage across the two windings by their turns ratio, such that: 

N1 = v1 , Eq. 2.5 N2 v2 

Where Ni is the number of turns and vi is the voltage of each winding. 

Rather than just obtaining the output voltage from the two ends of the secondary winding, 

it is also possible to place a tap at an intermediate point along the winding, in which case the 

location of the tap along the winding proportionally determines the voltage across the winding. 

For example a transformer with a 10:1 turns ratio and 120 V across the primary would have a 

secondary voltage of 12 V, whereas a tap placed in the middle of the winding would provide 6 V 

across each half of the winding. By placing additional taps, further voltages can be obtained 

from the secondary winding. 

Because the secondary voltages are related to each other by the turns ratio, it is possible 

to forgo the multiple voltage regulators—one on each output—of the previous approach. For 

example, in a switched­mode design, the voltage on the primary output is fed back to the control 

circuit that determines the duty ratio of the primary­side switch and the voltage across the 

primary side of the choke, the high­frequency transformer used in switched­mode designs. The 

output voltages across the secondary winding is distributed among the outputs proportionally, 

depending on the location of the tap or taps along the windings, so the closed­loop feedback 

regulation of one output results in some degree of regulation of the other outputs. An illustration 

of this approach can be found in Figure 2.11; the design in the Figure economizes on parts by 

eliminating the regulator that would otherwise be employed on the +12 V output. 

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­12

+12

+5

AC POW ER

FILTER

LINEAR

REG.

LINEAR

REG.

FILTER

LINEAR

REG.

FILTER

202 BLOCK DIAGRAM

Figure 2.11 The second winding is center­tapped, providing multiple voltages 

Although this approach results in a reduction in the number of components, it may not 

provide sufficient voltage regulation of the secondary outputs, and secondary post­regulation 

may be used on those outputs. For example, although the closed­loop feedback may provide a 

constant voltage to within 1% on the primary output, it may only provide cross­regulation to 

within 5% on the other outputs. Furthermore, this approach cannot be used to minimize the 

number of post­regulators in line­frequency designs, where the voltage across the primary is 

provided directly by the AC mains and not controlled by feedback from one of the outputs. 

2.3.9.3 Multiple Windings

Rather than provide a center tap, it is also possible to provide multiple windings on the 

secondary side of the transformer. These windings share the same core, but are not electrically 

connected with each other, which allows the resultant output busses to be isolated from each 

other, with different grounds.i This may be necessary if the application requires isolation 

between the circuits supplied by each output. Alternatively, even if it does not, a power supply 

that provides separate grounds that are later connected inside the product itself reduces the 

interference between circuits powered by each output bus. These benefits must be weighed 

i A ground is typically the lowest potential point in a circuit through which current returns to the supply, having 

performed useful work in a circuit. 

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against the increased complexity and cost of the transformer and output cable with multiple 

ground leads. Figure 2.11, for example, shows a line­frequency design that combines the two 

approaches: it contains two windings, one of which is center­tapped. 

Like the center tapped­designs described earlier, EPSs with multiple windings can also be 

designed with fewer voltage regulators than outputs because of cross­regulation between 

regulated and unregulated outputs. As before, the applicability of forgoing some voltage 

regulators depends on the output voltage accuracy requirements of the particular consumer 

product application, and it is not always seen in practice. Again, cross­regulation will generally 

not work with line­frequency designs because of the circuit’s inability to control the primary 

voltage. One exception would be a line frequency design with an AC pre­regulator. With a 

stable AC input voltage at the primary, the unregulated voltages will be much more stable. 

Linear regulators may still be used, but they will operate with consistently small voltage drops 

and much lower losses. 

2.3.9.4 Multiple Cores

A final approach to the design of multiple­voltage EPSs involves power supplies with 

multiple windings on multiple cores. This approach not only guarantees isolation between the 

different voltage outputs, but also allows the outputs to be operated independently. This allows 

for the operation of a portion of the EPS to be suspended when a particular output is not needed 

by the consumer product—for example, when the subsystem powered by the output is in standby 

mode. The result, depending on the design and usage of the consumer application, could be 

decreased losses at low loads as unused cores, and all the associated circuitry, shut down. 

The potential gains in efficiency come at a fairly high cost, as two transformers will 

require more core material than one transformer of equivalent power. Furthermore, in the case 

of a switched­mode design, each core will require its own duplicate switch and PWM controller 

with associated circuitry such as a snubber and an optocoupler. In this approach there are, to a 

significant degree, separate switching power supplies inside one enclosure. The only thing in 

common is that the multiple sections receive their rectified/filtered AC mains voltage from a 

common “front end.” The “front end” may consist of the basic AC conversion block as seen in 

Figure 2.10 or an AC/DC conversion stage that also incorporates power factor correction. 

Finally, to shut down individual outputs based on application needs requires communication 

between the application and the power supplies, adding further complexity and cost to the 

design. However, this design has been observed in practice, and is illustrated in Figure 2.12. 

This approach is often found where the equipment to be powered requires more than one output 

voltage of comparable power and voltage tolerance. 

Typical digital­circuit­oriented electronic equipment will generally require the largest 

portion of power for low voltage logic circuits, a smaller portion for mechanical devices or 

display circuits, and an even lower portion for what are often called “biasing” or control circuits. 

In these situations, these combined “auxiliary” outputs are typically much less than 50% of the 

total power and can be derived with auxiliary regulators without great efficiency penalty. 

However, sometimes a second output does not require logic type voltages, but nevertheless 

requires a large amount of tightly regulated, efficient power, just as the primary output does. In 

such a case, a second independent power “loop’ is called for. 

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RECTIFIER

FILTER

SWITCH

FILTER

PWM

CONTROL

ON \ OFF

CONTROL

+5 STANDBY

+12

PWM

CONTROL

SWITCH

INRUSH

LIMITER

AC

POWER .

. .

.

.

203 BLOCK DIAGRAM
 

Figure 2.12 Multiple­Voltage EPS Design with Multiple Independent Cores, Which Allow 

the Operation of One of the Outputs to be Suspended When Not Needed 

2.3.10 Particular Designs of High­Power EPSs 

Similar to other classes of EPSs, high­powered EPSs can be categorized based on their 

design as either line­frequency or switched­mode. Line­frequency power supplies are 

characterized by a relatively large, 60­Hz, transformer performing the isolation and voltage stepdown functions, followed by rectification and post regulation using either a linear or switching 

regulator. At lower power levels these linear­regulated EPSs are less expensive than switchingregulated EPSs because of their lower component count and less reliance (if at all) on integrated 

circuits for control. 

However, as the output power increases, the line­frequency transformer must become 

physically larger to accommodate saturation, necessitating an increase in wire size to carry 

higher current. This adds steel and copper to the power supply which causes it to become larger, 

heavier, and more costly. Switched­mode EPSs also become more expensive at higher output 

power levels; however, their cost is not as dependent on output power partly because fixed costs 

account for a larger proportion of the total cost. Therefore, their cost increases at a slower rate 

than line­frequency models. There is an additional factor which did not exist 20 years ago, but is 

a major consideration today. Global standardization today makes it virtually mandatory that 

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power supplies above 100 watts employ power factor correction. Doing this with power supplies 

employing 60Hz magnetics becomes size and cost prohibitive. On the other hand power factor 

correction circuits for switching power supplies are now standardized, require minimal space, 

and are relatively inexpensive, adding about a five to seven percent increase in material cost. 

The present global standards not only dictate high power factor, but also the minimization of 

harmonic generation. So, from a regulatory standpoint there is a decreasing global acceptability 

of higher power EPS units that use 60 Hz magnetics. In the end, at higher power levels 

switched­mode EPSs eventually become not only more efficient, but also less expensive than 

line­frequency EPSs. Nevertheless, both of these topologies are commonly used for ham radio 

applications. 

The use of line­frequency EPSs is in stark contrast with other segments of the EPS 

market, where it is difficult to find a line­frequency EPS with an output power above 10 W. The 

reason, touched upon previously, is electromagnetic interference or noise. Switched­mode 

designs use a high­frequency PWM controller to switch current rapidly through the EPS. 

Despite circuit measures such as filtering, these high­frequency currents both couple to the input 

and output of the power supply, where they appear as high frequency noise up to 30 MHz, 

creating fields that radiate from the switching circuitry. From there, the conducted and radiated 

energy can either be radiated with the input or output cable serving as antennas, or conducted 

directly into the load, causing undesirable interference. Even though these devices are designed 

to meet the regulations for class B digital devices set forth in Part 15(B) of the FCC regulations, 

they may still be unable to operate ham radio equipment, which requires the amplifying of weak 

external signals that may be corrupted by power supply emissions. Therefore, even though linefrequency EPSs are expensive and less efficient at high­power levels, they are still in use because 

they are not as electrically noisy as switched­mode EPSs. They also remain popular because of 

their relative simplicity and maintainability. 

2.3.10.1 Line­Frequency Designs for High­Power EPSs

Line­frequency EPSs are sometimes preferred for lower noise and emissions. Their 

efficiency can be improved with the use of either manual or automatic transformer tap switching. 

This minimizes the amount of voltage dropped across the linear regulator pass element. Another 

approach is line frequency switch mode, usually with silicon­controlled rectifiers (SCR) phase 

control, although, the use of SCRs is not as common now, because of the advent and availability 

of power MOSFETs. Again, the raw supply voltage into the linear regulator is kept low, to 

minimize the voltage drop and losses in the pass element. The switch frequency is usually twice 

the line frequency, so 120Hz for a 60Hz line. Switched­mode designs are discussed in the 

sections that follow. 

2.3.10.2 Switched­Mode Designs for High­Power EPSs

Switched EPSs use several different topologies, depending on the output power level, as 

shown in Figure 2.13. Of the different switching­regulated EPS topologies, those employing a 

“forward” converter, as opposed to a “flyback” converter are geared more towards high­power 

applications. There are fundamental differences between forward and flyback converters. The 

main difference between forward converters and flyback converters is that forward converters 

transfer energy to the secondary side of the transformer when the switching transistor is turned 

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on, whereas in a flyback EPS the energy transfer is done when the switching transistor is off. 

After the transformer in the energy transfer stage of the switching regulator there is a high speed 

diode and a ripple­filtering capacitor for flyback converters. In forward converters, there is a 

similar diode, (but usually a pair of them,) a similar ripple­filtering capacitor, as well as an 

output inductor. 

The presence or absence of the separate inductor is the most obvious difference between 

the two topologies. Often there is very little other substantive difference. However, the 

transformer core of a flyback converter usually requires a gapped core while the forward 

converter does not. The necessity for the gap restricts the options for choice of magnetic designs. 

This means that in certain situations or at certain power levels it may not be obvious which of the 

two methods the better option is. At higher power, the flyback approach can also be more prone 

to electrical noise generation. 

These extra components are shown in Figure 2.14. There are four types of forward 

converters used in high­power switched­mode EPSs: two­transistor, push­pull, half­bridge, and 

full­bridge. Figure 2.15 is an example of a push­pull topology. 

SWITCHED­MODE TOPOLOGIES
­

and corresponding power levels
­

High­Frequency
­

Switched­Mode
­

Flyback 

<125 W 

Forward 

One­transistor 

100 to 200 W 

Two­transistor 

150 to 600 W 

Push­pull 

<1000 W 

Half­Bridge 

150 to 600 W 

Full­Bridge 

>500 W 

Figure 2.13 Switched­Mode Topologies and Corresponding Power Levels
­

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Figure 2.14 Two­Transistor Forward Converter Circuit 

Two­Transistor Forward Converters 

The two­transistor forward converter layout is shown in Figure 2.14, above. This 

topology is typically used for 150 W to 600 W power supplies. In contrast to the following three 

topologies, this design is asymmetrical, meaning that the secondary of the transformer is not 

center tapped—i.e., the current only flows in one direction in the primary during energy transfer. 

One­transistor forward converters are used, but are generally used in lower power 

supplies. The voltage stresses on the single switch are about double the stresses on the switches 

in the two­transistor forward converter. Although, current technology has allowed the 

development of transistors that are designed for high voltage situations and thus, eliminate much 

of the switching related device stresses. The designer has to weigh the added cost of the higher 

voltage switch (one­transistor circuit) against the cost of providing floating gate drive for the 

upper switch (two­transistor circuit). At power levels where the flyback topology is no longer 

the best choice, the single transistor forward circuit is used. As power levels increase, the twoswitch topology becomes the better choice. 

Push­pull Converters 

In the push­pull converter topology, the primary and secondary sides of the transformer 

are connected symmetrically or center tapped as shown in Figure 2.15 below. Again, two 

transistors are used on the primary side. A controller turns the transistors on sequentially, with a 

short period of downtime in between to prevent simultaneous conduction. This causes a polarity 

change in the voltage across the transformer which maximizes energy transfer. While either 

transistor is on, energy is provided to the secondary side of the transformer. When the two 

transistors are off, the diodes on the secondary side act as snubbers to carry the output inductor 

current. The push­pull circuit transistors have the same voltage stresses as a single transistor 

forward circuit, about double Vin. Good use is made of the transformer core but primary side 

utilization is poorer than in the half and full bridge converter circuits. 

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Figure 2.15 Push­Pull Converter Circuit 

Half­Bridge Converters 

The operation of the half­bridge converter, shown in Figure 2.16 is very similar to the 

push­pull converter. However, in this topology the primary is not center­tapped and there are 

two capacitors that cause only half of the voltage to apply to the primary side of the transformer. 

Because of this, the half bridge converter is not used in applications requiring as much power as 

the push­pull converter, and like the two­transistor converter, this design is most commonly used 

in power supplies providing between 150 W and 600 W. 

Figure 2.16 Half­Bridge Converter Circuit 

Full­Bridge Converters 

Figure 2.17 below shows the full­bridge converter topology. It is very similar to the halfbridge converter, only the two capacitors prior to the transformer have been replaced with two 

more transistors. In this setup, the transistors work in pairs (1, 3 and 2, 4). These transistor pairs 

are then alternatively driven by a controller. The full­bridge converter provides two times the 

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output power of the half­bridge converter and is therefore more useful in very high­power 

applications, above 500 W. 

Figure 2.17 Full­Bridge Converter Circuit 

2.3.11 Particular Designs of Medical EPSs 

As described in section 2.2.3, medical EPSs face a number of design constraints. These 

include longer lifetimes, long output cords, levels of protection from insulation or protective 

ground connection, limited output voltages, and maximum leakage currents. 

Heat is the principle factor affecting the reliability and consequent lifetime of medical 

EPSs. The principal components that are susceptible to heat degradation over time are 

electrolytic capacitors, optocouplers, and integrated circuits. The EPS also dissipates heat 

through its components, particularly those that pass large amounts of current such as the 

transformer, switching transistor, and rectifier diodes. To mitigate against heat and extend the 

lifetime of the medical EPS, designs typically include MOSFETs with low Rds_on. 

Long output cords can be necessary for safety to separate the medical device from mains 

power. The main design option for the output cords is the wire gauge, which governs the 

resistance. Resistance, particularly for long output cords, can be a major source of loss, up to 

10% for high­power, low­voltage medical EPSs. 

Insulation and a protective connection to ground are two methods for providing a layer of 

protection. Insulation requirements typically affect spacing between components, but do not 

affect efficiency. One exception is for transformers where insulation spacing requirements 

between windings reduces efficiency. 

Lower output voltages, particularly those below 10 V, tend to decrease efficiency; 

although the SELV limit of 30 V is high enough that it should not overly constrain the efficiency 

of medical EPSs. 

Maximum leakage currents have the largest effect on the design and efficiency of 

medical EPSs. The primary barrier to leakage currents from mains to the patient is at the barrier 

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within the EPS between the primary (mains) and the secondary (output). Only a few components 

bridge both sides of that barrier: the transformer, an optocoupler, and a Y­capacitor, which is the 

largest conductor of leakage current. The transformer is the primary means of passing energy 

from mains through to the output. Leakage currents through the transformer can be reduced by 

increasing the insulation and spacing between the windings. An optocoupler provides feedback 

from the output to the controlling circuitry on the primary side. The optocoupler is not a 

significant source of leakage current. The purpose of the Y­capacitor is to reduce 

electromagnetic interference (EMI) and meet electromagnetic compatibility requirements. The 

Y­capacitor reduces EMI by shunting capacitive­coupled common mode noise generated 

between primary and secondary windings within the transformer. However, inductors at the 

input and output terminals of the EPS can offer similar EMI reductions. By replacing the Ycapacitor with such inductors, either of higher inductance values or in greater number, the 

medical EPS can still meet EMC requirements and eliminate a major conductive path for leakage 

currents. 

2.3.12 Particular Designs of EPSs for BCs 

j EPSs for BCs, as described in the NOPR, are electronically the same as Class A EPSs.

Therefore, there are no unique design traits for EPSs for BCs beyond those discussed in 

subsections 2.3.1 through 2.3.8. 

2.4 Technology Options for Improving Energy Efficiency 

2.4.1 Transformers 

For line­frequency BCs and EPSs, the largest losses are in the transformer, particularly at 

light loads. The most effective means to reduce transformer power loss at light loads is to select a 

transformer with higher quality core material and a lower level of magnetic induction. At line 

frequency, the transformer core material typically is thinly laminated steel alloyed with silicon. 

The amount of silicon affects the core power loss and the cost of the transformer. Core 

performance is enhanced by magnetically orienting the grain structure in the metal. The industry 

standard for common non­oriented grain­structure core material ratings range from M19 to M45, 

with the lower number having fewer electrical losses. M6 core steel is used in an energy efficient 

EPS transformer because it is a high­quality grain­oriented core steel that has very low electrical 

losses. 

The second important factor contributing to core loss is the level of magnetic induction. 

Core losses are measured in watts per pound (W/lb), and induction is given in kilogauss (kG). 

Induction levels in these devices typically range between 10 kG and 15 kG. Reducing the 

induction level will reduce the core losses, but increase the winding losses. Reducing the 

induction requires more wire turns and therefore a larger core for a given power rating. The 

trade­off of these improvements is the increased size and weight of the transformer, and 

ultimately the EPS. Table 2.2 shows the effects of material type and induction on core loss. 

j U.S. Department of Energy­Office of Energy Efficiency and Renewable Energy. Energy Efficiency Program for 

Consumer Products: Public Meeting and Availability of Framework Document for Battery Chargers and External 

Power Supplies. Federal Register. June 4, 2009. vol. 74, No. 106: p. 26816. 

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Power loss in the transformer core can be reduced by an order of magnitude by increasing the 

quality of the core steel and reducing the level of magnetic induction: 0.28 W/lb versus 3.1 W/lb. 

Table 2.2 Quality of Core Steel and Level of Magnetic Induction 

Steel Core Losses at Various Levels of Magnetic Induction 

10 kG 12 kG 15 kG 

M6 0.28 W/lb 0.40 W/lb 0.60 W/lb 

M19 0.85 W/lb 1.2 W/lb 2.0 W/lb 

M45 1.4 W/lb 1.9 W/lb 3.1 W/lb 

Additionally, some primary transformer windings have high resistance to prevent failure 

in the case of overload conditions. Using a separate fuse or thermal cutout to prevent failure 

would allow the transformer to have a lower winding resistance, thus reducing electrical losses. 

A large potential source of energy loss in a high­frequency EPS is the flyback 

transformer, similar to the transformer in line­frequency EPSs. Methods of improving the energy 

efficiency of chokes are similar to those for improving transformers, that is, improving the core 

material and increasing the amount of copper to reduce copper losses. 

Particularly, for EPSs with output power greater than 10 W, a switched­mode power 

supply is generally a more efficient alternative to a line­frequency. At lower wattages, however, 

neither regulation technology has a clear efficiency advantage. This is partly because the 

switching regulator circuit components themselves consume some energy, regardless of the 

output power of the device. At lower wattages, this fixed energy consumption is a more 

significant proportion of total EPS energy consumption. 

2.4.2 Diode Losses and Synchronous Rectification 

Diodes are another source of loss for DC line­frequency EPSs. These losses increase as 

the output voltage decreases, and become particularly significant below 12 V. The power 

consumed by a diode is the product of the current flowing through the diode multiplied by the 

voltage drop across it. When a line­frequency EPS is designed for low­output voltage, that drop 

becomes a significant portion of the overall losses in the EPS. Using Schottky diodesk reduces 

the voltage drop across the diodes, thus improving efficiency. Conventional diodes have a 

voltage drop of about 1.0 V at typical operating conditions, which can be reduced to about 0.5­

0.6 V by using Schottky diodes. 

Synchronous rectification offers even lower losses by replacing diodes with very low 

RDS_ON MOSFET transistors. In this situation, the transistor mimics the rectification effect of the 

diode. However, the loss across the source­to­drain resistance of the transistor is much lower 

k A Schottky diode is a metal­semiconductor diode with a smaller voltage drop than a conventional diode, therefore 

consumes less power. 

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than that of a diode. When synchronous rectification is used, it is virtually always on the 

secondary side of the transformer in switched­mode EPSs because that is where it offers the most 

energy savings. In a switching power supply the output rectifiers typically constitute 50­60% of 

all semiconductor losses in the unit. Consequently, reducing rectifier losses by a factor of 2 with 

synchronous rectification is very meaningful. 

2.4.3 Technology Options for Multiple­Voltage EPSs 

All technology options for Class A EPSs are applicable to multiple­voltage EPSs. 

2.4.4 Technology Options for High­Power EPSs 

There are several generic technology options for all EPSs that can increase the efficiency 

of high­power EPSs, as well as some technology options explicitly for EPSs. Manufacturers use 

various topologies when designing their EPSs which can change depending on intended utility. 

Line­frequency, linear­regulated EPSs are generally the least efficient of the topologies created, 

but they are still common in communications because of their lower electromagnetic 

interference. There are ways to improve the efficiency of these power supplies; however, as 

efficiency becomes a greater concern, some users are also changing to switched­mode EPSs. 

Even though noise is a concern with switched­mode designs, manufacturers can make 

switched­mode EPSs that meet FCC regulations on electromagnetic interference (EMI). This 

gives users a viable option if more efficiency is needed than an improved line­frequency EPS can 

provide. DOE considered several technology options, some of which can be used on linearregulated EPSs and some of which are only applicable to switched­mode EPSs. DOE also 

considered switched­mode EPSs a technology option for increasing efficiency from levels 

achievable by line­frequency EPSs. 

The technology options, discussed in detail previously and that DOE considered for 

improving the efficiency of high­power EPSs are: 

• Improved Core Steel in Transformer 

• Switched­Mode EPSs 

• Multi­Mode Integrated Circuits 

• Low­Loss Transistors 

• Resonant Switching 

• Schottky Diodes & Synchronous Rectification 

2.4.5 Technology Options for Medical EPSs 

All technology options for Class A EPSs are applicable to medical EPSs. 

2.4.6 Technology Options for EPSs for BCs 

All technology options for Class A EPSs are applicable to EPSs for BCs. 

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CHAPTER 3 ENGINEERING ANALYSIS 

3.1 Introduction 

This chapter of Technical Support Document (TSD) contains information that supports 

and expands on the Engineering Analysis section of the Notice of Proposed Rulemaking 

(NOPR). Specifically it provides examples and additional details for DOE’s methodology for 

scaling cost and efficiency of non­Class A EPSs. The chapter also provides details on 

representative product classes, representative units, and candidate standard levels discussed in 

the NOPR. In addition, Appendix A includes the manufacturer interview guide that Navigant 

Consulting, Inc. used when interviewing manufacturers on behalf of DOE. 

3.2 DOE Methods for Determining ERMC 

In the engineering analysis, DOE focused on efficiency­related materials cost (ERMC). 

DOE scaled data when the tested units were different than the representative units. DOE needed 

to scale the data because, although it attempted to purchase units for testing and teardown that all 

had the characteristics of the representative units, it was not always possible due to limited 

product availability in the market and changes to the representative units’ characteristics during 

the course of the analysis. DOE identified three key characteristics: output power, output voltage, 

and production volume. If the test units differed from the representative units by any of these 

three characteristics, their costs and efficiencies would not be directly applicable to the 

representative units. For these cases DOE developed a methodology to scale cost and efficiency 

data for test units to estimate what those values would be, if the test units were to have the 

characteristics of the representative units. The following section provides additional explanation 

and examples of how and why these scaling methods were used. 

As illustrated in Figure 3.1, DOE calculated ERMC from iSuppli data whenever possible. 

When iSuppli data was not directly available, DOE estimated the ERMCs of EPSs not directly 

costed by iSuppli by developing scaling methods. DOE’s scaling methods combined low­volume 

cost estimates performed by its subject­matter experts (SMEs) with iSuppli’s high­volume cost 

estimates for other units. Specifically, it developed four methods to determine the high­volume 

cost of individual components, which were used to construct a high­volume ERMC, which was 

subsequently scaled to the representative unit volume, power, and voltage, as described in 

sections 3.3, 3.4, and 3.5. 

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1 

 

 

 

 

 

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- - 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

        

 

 

 

          

 

 

 

1. DOE 

selected 

units 

2. SMEs 

measured 

efficiency 

3. SMEs 

costed 

units 

4. iSuppli 

costed 

units 

5. DOE 

developed 

methods 

7. DOE 

compiled highvolume costs 

6. DOE 

scaled 

costs 

2 

3 

4 

5

2 

3 

4 

5 

BOM $ 

Cap 

Res 

Xfmr 

$0.11 

$0.03 

$0.64 

BOM $ 

Low to High 

Volume 

Scaling 

Methods 

1

5 

2

3 

4 

# % $ 

75% 

46% 

$1.68 

$2.09 

2

3

75% $3.59 

32% 

46% 

$4.68 

$5.21 

1 

2

3

32% 

65% 

53% 

$1.22 

$1.03 

$1.54 

1 

4

5 

.........

Cap 

Res 

Xfmr 

$0.02 

$0.007 

$0.26 ...... 

high volume 

from low to 

Costs scaled Highvolume 

costs only 

Low- Highvolume volume 

costs from costs from 

public private 

catalogs database 

Figure 3.1 Illustration of DOE Process Used to Compile High­Volume Cost Estimates for 

the Non­Class A Eps Determination Analysis from Sme and Isuppli Teardowns 

3.2.1 Summary of Methods 

To develop a high­volume ERMC from a low­volume ERMC provided, DOE analyzed 

eight high­volume iSuppli cost estimates for units with approximately the same production 

volume (150,000–225,000 units/year) and therefore had comparable component costs. DOE then 

used high­volume component costs and their averages, and ratios between the high­volume and 

low­volume component costs and their averages, to replace or scale the low­volume component 

costs, arriving at high­volume ERMCs comparable with the other high­volume cost­estimates 

used in later analysis. The methods that DOE used to perform these transformations are listed 

below. 

Method 1. Direct Substitution of iSuppli Component Costs: Directly substitute highvolume iSuppli component costs for low­volume component costs when there was an 

exact match between the two components (e.g., certain electrolytic capacitors). See 

section 3.2.5.1. 

Method 2. Direct Substitution of Category­Average iSuppli Component Costs: Directly 

substitute the category­average high volume iSuppli component costs across 

component categories where prices do not vary (e.g., surface­mount resistors). See 

section 3.2.5.2. 

1 

2 

3 

4 

5 

# % $ 

32% 

75% 

46% 

65% 

53% 

1 

2 

3 

4 

5 

1 

2 

3 

4 

5 

# % $ 

1 

2 

3 

4 

5 

......

# % $ # % $ 

1 

2 

3 

4 

5 

# % $ 

1 

2 

3 

4 

5 

iSuppli 

DOE 

scaling 

DOE 

scaling 

iSuppli 

iSuppli 

Source 

$1.22 

$1.68 

$2.09 

$1.03 

$1.54 

32% 

75% 

46% 

65% 

53% ... 

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Method 3. Scaling of SME Costs Using SME­iSuppli Component Matches: Multiply 

the low­volume SME component costs by a category­average scaling ratio between 

the low­volume SME component costs and the high­volume iSuppli component costs 

(e.g., bipolar­junction transistors). See section 3.2.5.3. 

Method 4. Substitute Category­Average iSuppli Component Costs : For the remaining 

components, for which no low­volume SME component costs were estimated, simply 

use the average high­volume iSuppli cost estimates for the component category. (e.g., 

some integrated circuits). See section 3.2.5.4 

3.2.2 Available Data 

3.2.2.1 SME Efficiency Measurements of 5 W EPSs

In 2007, DOE’s SMEs measured the efficiencies of 11 EPSs with nameplate output 

power at or around 5 W and voltage around 5 V. These were made by different manufacturers 

and featured disparate designs, resulting in a wide spread of active­mode efficiencies and no­load 

powers. The measurement results appear in the figure below. 

0

0.2

0.4

0.6

0.8

1

1.2

1.4

1.6

1.8

2

0% 10% 20% 30% 40% 50% 60% 70% 80%

Active Mode Efficiency [%]

No­Load Power [W]

5 W, 5 V

5.15 W, 5.15 V

5.2 W, 5.2 V

Figure 3.2 SME Efficiency Measurements of 5 W EPSs 

3.2.2.2 SME Teardowns

The SMEs tested 11 EPSs, nine with an output power of 5 W and output voltage of 5 V, 

one with 5.15 W, 5.15 V, and one with 5.2 W, and 5.2 V. Of these, nine were torn down. The 

teardowns, whose results are listed in Table 3.1, consisted of opening the EPS housing, counting 

and identifying the components, and costing them using component catalogs such as Digi­Keya 

a “Digi­Key Catalog,” Digi­Key Corporation, www.digikey.com. 

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and Mouser.b The costs for most components were obtained at low­volume quantities of 1000 

units, with the exception of line­frequency transformers, which were costed using a bottom­up 

approach, taking into account the cost of steel for the laminations ($1.667/lb), and adding in the 

costs of copper and assembly (assumed to be equal to the steel cost). In cases where the 

component could not be identified or located in the catalogs, costs for equivalent or similar 

components were used. 

Table 3.1 EPSs Torn Down by SMEs to Develop Low­Volume ERMCs 

Unit 

# 

Pout Vout Mfr. Model Active 

Mode 

Eff. 

No­Load 

Power 

[W] 

LowVolume 

ERMC 

27 5 5 Globtek 48­5­1000R 49% 1.424 $2.230 

17 5 5 Phc PV­51AR 36% 1.852 $2.950 

8 5 5 Phihong PSA05R­050­R 73% 0.112 $3.411 

22 5 5 Prs HP­5V2 59% 0.421 $3.978 

18 5 5 Ericsson PS­513 70% 0.540 $4.011 

24 5 5 Phihong PSA05R­050R 72% 0.109 $4.040 

21 5.2 5.2 Netbit DSC­51FL­52P US 71% 0.102 $4.670 

25 5 5 Phihong PSA05A­050 66% 0.641 $4.712 

37 5 5 Phihong PSA05A­050 66% 0.657 $5.020 

45 5 5 Reliapro DCU050100 50% 1.400 No 

Teardown 

10 5.15 5.15 Phihong PSAA05A­050­R 53% 0.108 No 

Teardown 

The SMEs tore down several BCs in a similar fashion. Because BCs and EPSs share 

many common components, these BC teardowns were used to develop the four methods for 

scaling between low­volume and high­volume parts costs, as described in section 3.2.5.3. 

3.2.3 DOE Method for Determining ERMC from iSuppli Data 

DOE subcontracted iSuppli to tear down and cost 20 EPSs and BCs, of which six were 

non­Class A EPSs. Specifically, DOE provided iSuppli with 20 units for which iSuppli 

determined the cost per component at high volume. DOE included in each unit’s ERMC the costs 

for components directly related to efficiency, but not costs for components secondarily or not 

related to efficiency. To better explain this approach, DOE provides an example of this approach 

for some of the components in EPS #106. 

Table 3.2 lists five of the components costed by iSuppli for EPS #106; Table 3.3 presents 

a complete list of components for the EPS. Table 3.4 and Table 3.5 illustrate an example for EPS 

#106. The ERMC of $1.13 for EPS #106 includes costs for the capacitor ($0.078) and diode 

($0.035) in the table. However, costs for the printed circuit board (PCB), enclosure and label are 

b “Mouser Electronics Catalog,” Mouser Electronics, Inc., www.mouser.com. 

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not included. In general, more efficient circuits tend to be smaller and would therefore require 

smaller, and consequently cheaper, enclosures and PCBs. Therefore, DOE considers the PCB 

and enclosure as secondarily related to efficiency because their cost can indirectly vary with 

efficiency. The ERMC does not include the cost for the label because the label has no relation to 

efficiency. 

Table 3.2 Information for Five Components from EPS #106 

Component Efficiency Type Component Cost Included in ERMC 

Capacitor (Film, 0.1uF) Direct $0.078 Included 

Diode (Schottky) Direct $0.035 Included 

Printed Circuit Board Secondary $0.094 Not Included 

Enclosure (Top) Secondary $0.210 Not Included 

Label (White Mylar) Not efficiency related $0.014 Not Included 

In addition to materials costs, iSuppli also provided conversion costs for labor, such as 

for assembly, insertion, and testing. However, DOE did not include labor costs in the ERMCs, 

but rather accounted for labor costs in the markup from ERMC to EPS manufacturer sales price. 

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Table 3.3 Information for All Components from EPS #106
­

Component Efficiency 

Type Quantity Cost Per Component 

Included in 

ERMC 

Analog Controller Direct 1 $0.1700 Included 

Analog Regulator Direct 1 $0.0180 Included 

Capacitor (Ceramic) Direct 3 $0.0028 Included 

Capacitor (Ceramic, 0.1nF) Direct 1 $0.0160 Included 

Capacitor (Electrolytic, 100uF) Direct 1 $0.0170 Included 

Capacitor (Electrolytic, 10uF) Direct 1 $0.0520 Included 

Capacitor (Electrolytic, 330uF) Direct 1 $0.0170 Included 

Capacitor (Electrolytic, 470uF) Direct 1 $0.0300 Included 

Capacitor (Electrolytic, 47uF) Direct 1 $0.0100 Included 

Capacitor (Film, 0.1uF) Direct 1 $0.0780 Included 

Capacitor (Film, 2.2uF) Direct 1 $0.0220 Included 

Diode Direct 5 $0.0052 Included 

Diode (Fast recovery) Direct 1 $0.0150 Included 

Diode (Melf) Direct 2 $0.0090 Included 

Diode (Schottky) Direct 1 $0.0350 Included 

Inductor Direct 1 $0.0380 Included 

Optocoupler Direct 2 $0.0450 Included 

Resistor Direct 2 $0.0120 Included 

Resistor Direct 3 $0.0009 Included 

Resistor Direct 9 $0.0003 Included 

Thermistor Direct 1 $0.0350 Included 

Transformer Direct 1 $0.2300 Included 

Transformer Direct 1 $0.1550 Included 

Transistor Direct 1 $0.0200 Included 

AC Plug Secondary 1 $0.1800 Not Included 

Enclosure (Bottom) Secondary 1 $0.2400 Not Included 

Enclosure (Top) Secondary 1 $0.2100 Not Included 

Printed Circuit Board Secondary 1 $0.0940 Not Included 

Spacer Secondary 1 $0.0550 Not Included 

Jack (USB) Not efficiency related 1 $0.0750 Not Included 

Label (Aluminized Mylar) Not efficiency related 1 $0.0580 Not Included 

Label (White Mylar) Not efficiency related 1 $0.0140 Not Included 

Label (White Paper) Not efficiency related 1 $0.0110 Not Included 

Jumper Wire Not efficiency related 1 $0.0100 Not Included 

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Table 3.4 EPS #106 Production Related Device Information
­

Device 

Category Cell­Phone Chargers 

ID# 106 

Reference Information EPS #106 – 2.5W Class A 

Annual Production Volume (K Units / Year) 1,000 

Production Lifespan (Years) 5 

Lifetime Production Volume (Units) 5,000,000 

Table 3.5 EPS # 106 Summary of Component Costs by Efficiency Relevance
­

EPS #106 – 2.5W Class A 

Cost Type Efficiency Family Type Component Type 

% of Total 

Component Cost 

$USD 

Sum of Total 

Component 

Cost 

$USD 

Sum of Qty 

Direct 

Material Cost 

Direct Magnetic (transformer only) 

Capacitor 

Metal - heatsinks only 

Transistor 

Resistor 

Diode 

Fan 

Magnetic 

Analog 

Fuse 

Coupler 

LED 

17.87% $0.39 

11.62% $0.25 

0.00% 

0.93% $0.02 

2.99% $0.06 

4.36% $0.09 

0.00% 

1.76% $0.04 

8.73% $0.19 

0.00% 

4.18% $0.09 

0.00% 

2 

11 

1 

15 

9 

1 

2 

2 

ERMC Efficiency related 

materials cost (Direct Total) 52.45% $1.13 43 

Not efficiency related Metals 

Switch 

Connector 

Hardware 

Other 

0.00% 

0.00% 

3.95% $0.09 

0.00% 

3.85% $0.08 

2 

3 

Not efficiency related Total 7.80% $0.17 5 

Secondary Plastics & Elastomers 

PCB 

Connector (Output Cord) 

31.80% $0.69 

4.36% $0.09 

0.00% 

4 

1 

Secondary Total 36.16% $0.78 5 

Direct Material Cost Total 96.41% $2.08 53 

Conversion 

Cost 

Not efficiency related Assembly 

Test 

Insertion 

0.00% $0.00 

2.28% $0.05 

1.31% $0.03 

Not efficiency related Total 3.59% $0.08 

Conversion Cost Total 3.59% $0.08 

Grand Total 100.00% $2.15 53 

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3.2.4 Assumptions 

3.2.4.1 Production Volume

As described in section 3.2.2.2, the SMEs analyzed the cost of the 5 W EPSs using 

production volumes of 1,000 units/year. Whereas iSuppli performed their cost estimates using 

component costs at volumes of 1,000 unit/year to 1,000,000 units/year. To develop high­volume 

ERMCs for the 5 W EPSs and several non­Class A EPSs, DOE relied on eight iSuppli teardowns 

developed assuming volumes around 225,000 units/year and listed in Table 3.6. 

Because iSuppli estimated the component costs assuming a similar volume, DOE was 

able to use cost estimate from across these eight teardowns to create its own high­volume 

ERMC. 

Table 3.6 EPS and BC Units that iSuppli Tore Down and DOE Used in Data Scaling 

Unit # Device Class Manufacturer Model 

Volume 

[units/year] 

EPS #117 Mid­Power EPSs Elpac FW1812­760F 225,000 

EPS #118 Mid­Power EPSs Elpac FWC1812­760F­NC 225,000 

BC #2 Low­Voltage BCs Norelco 7140XL 150,000 

EPS #120 Mid­Power EPSs SL­Power PW118RA1203F01 225,000 

BC #28 Low­Voltage BCs Wahl 9953 150,000 

BC #5 High­Voltage BCs Makita DC1804 T 150,000 

EPS #127 High­Power EPSs SL­Power PW122MA2403F01 225,000 

EPS #128 High­Power EPSs XP­Power AML120PS24 225,000 

3.2.4.2 Data Included in the Cost­Efficiency Curves

(1) Costs: Besides electronic components, an EPS contains a printed circuit board to 

which the components are attached and through which they are connected to each other, 

heat­sinks that dissipate heat generated during power conversion, mounting hardware as 

well as a plastic housing and output (and potentially input) cords and connectors. Except 

for heat sinks, which were excluded, the SME cost estimates included all components 

“directly related” to efficiency. The heat sinks and the remainder of the components, 

which are secondarily or not at all related to efficiency, were inventoried by iSuppli, but 

not by the SMEs, and were not included in the efficiency­related BOM cost estimates. 

(2) Power Losses: The low output voltage (5 V) of the 5 W EPSs used to estimate the 

efficiency typical of EPSs for BCs results in significant losses in the output cable, which 

decrease the active­mode efficiency. Because altering the length and gauge of the output 

cable is not a design option for increased efficiency (a different output cable may impact 

utility), the cable losses were not included in the analysis of the 5 W EPSs. DOE seeks 

comment on how it should treat cable losses and their variability in the future. 

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3.2.5 SME Cost­Scaling Methodology 

3.2.5.1 Direct Substitution of iSuppli Component Costs

In cases where there was an exact match between a component in the low­volume SME 

BOM and a component in the high­volume iSuppli BOM, DOE directly substituted the highvolume cost estimate. This was performed in the case of generic components such as 1N2007 

rectifier diodes and electrolytic capacitors with equal capacitances and voltage ratings. 

3.2.5.2 Direct Substitution of Category­Average iSuppli Component Costs

The costs of the components contained in the eight high­volume iSuppli teardowns were 

categorized by component family, component type, component subtype, and additional 

qualifications, which included qualities that affect cost such as package form, precision, or 

voltage, current, and power ratings. At each level of detail, the component costs belonging to the 

same category—and regardless from which of the eight teardowns the components originated— 

were grouped together and compared. 

For example, the component costs for all the precision resistors in 0603 packages across 

the eight teardowns were compared to each other. The same was done for the 0805­package 

precision resistors, and then all (precision and non­precision) 0603­ and 0805­package resistors 

and then 0603 package capacitors, etc., and then for all capacitors and all resistors, regardless of 

their package form. Finally, all the component costs in each family (e.g., passive, discrete 

semiconductor, etc.) were also compared. The relationships between the component categories, 

including some examples, are illustrated in Figure 3.3. 

Comp. Family 

Comp. Type 

Comp. Subtype 

Add’l Qualifications 

All Components 

Passive Discrete Semiconductor 

Capacitor Resistor Diode Transistor 

0603 0805 

Etc. 

Etc. 

IC 

Precision Precision 

Etc. 

Categories: 

Figure 3.3 Categorization of Components Used to Perform Substitution or Scaling 

Depending on the spread and number of component cost estimates within each category, 

a category­average cost was calculated and substituted for all members of that category. For 

example, 0402­package capacitors are a commodity item the cost of which does not depend 

strongly on manufacturer, capacitance, or temperature characteristics. Therefore, all 0402 

capacitors, regardless of capacitance, had similar costs, so the iSuppli cost estimates could be 

averaged and the average substituted directly into the 5 W teardown. 

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The same substitution, however, could not be performed with capacitors in general—the 

parent category containing 0402 capacitors. In addition to 0402 and other surface­mount 

capacitors, this category includes many leaded capacitors, the costs of which depend 

significantly on capacitance, rated voltage, and temperature characteristics. As a result, a 

comparison of the costs of all capacitors (i.e., surface­mount and leaded) showed great variation 

in the estimated component cost, meaning that an average would not be representative of the 

category as a whole. 

An average may also not be representative if, despite a low variation in the per­category 

component cost estimates, there is a limited number of estimates to average. Given two estimates 

that are within 0.5 cents of each other, it is difficult to predict where the third one will fall. A 

minimum number of cost estimates is therefore necessary to reassure that the variation of this 

sample of cost estimates is characteristic of the component category, and that an average based 

on the sample is representative. These two tests—variation and number of cost estimates—are 

illustrated in Figure 3.4. 

Figure 3.4 Tests of Variation and Number of Cost Estimates Necessary for Device Scaling 

In the derivation of high­volume 5 W curves for use in the non­Class A determination 

analysis, the substitution of component­category iSuppli cost estimates into the SME teardowns 

was performed under the following constraints on the variation and number of cost estimates: 

•	 Variation: The standard deviation of the cost estimates for the component category 

had to be under $0.01. A variation of $0.01 was assumed insignificant given a total 

unit cost of greater than $1.00. 

•	 Sample Size: The number of cost estimates for the component category had to be 

greater than 5. A number of cost estimates greater than 5 was deemed to be 

representative of the entire component category, and given a sufficiently low 

variation, usable as a basis for a category­wide average. 

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•	 Exceptions: Exceptions were made for standard­sized passive components, such as 

capacitors and resistors in 0402 and 0603 and resistors in 1/4 W and 1/2 W packages. 

These were assumed to exhibit sufficiently small variation, even if the number of cost 

estimates was less than 5, such that the average was always taken and substituted into 

the SME teardowns for components from these categories. 

As a result, the average iSuppli cost estimates for the following categories were 

substituted directly into the SME 5 W teardowns (the component costs for the remainder of 

categories had to be estimated using the other methods): 

•	 Discrete Semiconductor, Diode, 

Rectifier, 1­2A • Passive, Resistor, 0603 

•	 Discrete Semiconductor, Diode, 

Zener • Passive, Resistor, 0805 

•	 Discrete Semiconductor, Transistor, 

BJT, 500­1000 mA • Passive, Resistor, 0805, Precision 

•	 Optical Semiconductor • Passive, Resistor, 1206 

•	 Optical Semiconductor, Coupler • Passive, Resistor, 1210 

•	 Passive, Capacitor, 0402, • Passive, Resistor, 2512 

•	 Passive, Capacitor, 0603, • Passive, Resistor, 1/8 W 

•	 Passive, Capacitor, 0805, • Passive, Resistor, 1/4 W 

•	 Passive, Capacitor, Y1, • Passive, Resistor, 1/2 W 

•	 Passive, Capacitor, Y2 • Passive, Resistor, 1 W 

•	 Passive, Capacitor, Y2, 1­10nF • Passive, Resistor, 2 W 

•	 Passive, Resistor, 0402 • Passive, Resistor, Thermistor 

3.2.5.3 Scaling of SME Costs Using SME­iSuppli Component Matches

As can be seen above, the number of component categories that had sufficiently low 

variation and sufficiently large number of cost estimates was small, limited mostly to 

standardized surface­mount passives and leaded resistors in 1/8 W through 2 W packages.c In 

the other component categories, however, there was more variation in the characteristics of the 

components and therefore more variation in their cost. Rather than substitute category­average 

c The package size of resistors determines their power rating. 

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component costs directly into the 5 W SME teardowns, the SME cost estimates were scaled by a 

category­specific ratio. 

Of the eight units torn down by iSuppli (shown in Table 3.6) three were also torn down 

by the SMEs: BCs #2, #5, and #28. These were used to calculate the scaling ratios by matching 

the low­volume SME cost estimate for each component with the high­volume iSuppli cost 

estimate. The iSuppli component cost was then divided by the SME component cost, resulting in 

a scaling ratio between the two, as shown in Table 3.7. 

Table 3.7 Example Matches Between SME and iSuppli Component Cost Estimates Used 

to Develop Category­Specific Scaling Ratios 

SME iSuppli iSuppli 

SME Comp iSuppli Comp. iSuppli Comp. ScaComp. SME Comp. . Cost Comp. Descrip Comp. Cost Comp. Add’l ling 

Type Description [$] Type tion Pkg. [$] Subtype Qual. Ratio 

Choke 

Axial lead 

choke 3.9mH 

TDK in 

Mouser 

0.350 Magnetic 

Inductor 

­

Wound 

Ferrite 

Core 

SMD 0.0340 Wound 

Ferrite 0.10 

Choke 

Ferrite bead 

wound as 

small 

common 

mode choke 

0.100 Magnetic Ferrite 

Bead 0805 0.0025 Ferrite 

Bead 0.03 

Axial ­

Resistor 1/4W 0.012 Resistor Carbon 1/4 W 0.0044 1/4 W 0.37 

Film 

Capacitor 1500pF 

ceramic 0.025 Capacitor 

Ceramic 

Disc ­

Radial, 

Dipped, 

1.5nF 

Thru 

Hole 0.0125 Ceramic 1­10 

nF 0.50 

Transistor SOT­23 0.030 Transistor 

Bipolar 

­ NPN, 

50V, 

100mA 

SOT34 

6 0.0080 BJT 

100­

200 

mA 

0.27 

To illustrate, suppose that two of the units torn down by the SMEs featured transistors in 

the same package—TO­220. Unlike 0402 capacitors, which vary only in capacitance, TO­220 

transistors look similar but may vary in many substantive ways (e.g., device type, voltage and 

current ratings, on resistance, frequency response, etc.) that will significantly affect their cost. 

Therefore, it would not be appropriate to find the iSuppli costs of all TO­220 transistors, take the 

average, and substitute that for the cost of each TO­220 transistor that appears in the SME 

teardowns. Rather, a scaling ratio must be calculated that reflects the volume discounting typical 

for that component category and subsequently multiplied by the low­volume SME component 

costs to calculate high­volume component costs. 

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Once the match between the low­volume SME and high­volume iSuppli cost estimates 

for the same component was made, and a ratio calculated, the ratios were then grouped according 

to the categories in Figure 3.3. Components were first grouped by package form, then by 

component type, and finally by component family; average scaling ratios were calculated for 

each of the categories. 

Scaling ratios had to be developed for each category level due to the limited number of 

component matches,d a scaling ratio could not be calculated for all components. Using Table 3.7 

as an example, a scaling ratio was calculated for 3.9 mH chokes, but it may not be applicable 

when scaling a 39 mH choke. It was necessary, therefore, to calculate a scaling ratio for all 

magnetics and passives. The appropriate (as explained below) category­specific ratio was then 

used to scale the low­volume cost estimates of components for which substitution was not 

possible and to obtain a high­volume cost estimate. 

Scaling ratios varied within and between component categories, with greatest variation 

between the ratios for components in the integrated circuit component family (4 matches, 

average scaling ratio of 0.41, standard deviation of 0.40) and least variation between the 

components in the optical semiconductor component family (2 matches, average scaling ratio of 

0.233, standard deviation of 0.01). Furthermore, each category level (e.g., component type, 

package form, etc.) had its own scaling ratio that differed from the scaling ratio of the broader 

categories above it. For instance: 

•	 The 2–5 A rated rectifier diode fully qualified component category had an average 

scaling ratio of 0.09; 

•	 The rectifier diode component subtype (which includes rectifiers of all current 

ratings) had an average scaling ratio of 0.21; 

•	 The diode component type (which includes rectifiers as well as switching and Zener 

diodes) had an average scaling ratio of 0.26; and 

•	 The discrete semiconductor component family (which includes diodes as well as 

transistors and thyristors) had an average scaling ratio of 0.36. 

In this example, the choice of scaling ratio could change the high­volume cost by a factor 

of four. DOE considered several approaches to choose the ratio. 

In one approach, DOE could simply take the ratio for the narrowest category that 

includes the component undergoing cost scaling. Under this scheme, the low­volume SME cost 

of a 2–5 A rated rectifier diode would be multiplied by 0.09 to arrive at a high­volume cost. 

Similarly the cost of a generic rectifier diode with an unknown current rating would be 

multiplied by 0.21, the cost of a diode with an unknown function (e.g., rectification, switching, 

etc.) would be multiplied by 0.26, while the cost of a thyristor—a semiconductor component 

d Again, only three BCs had undergone both SME and iSuppli teardowns, resulting in only 66 component matches 

that could be used to calculate scaling ratios. 

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used for power switching—would be multiplied by 0.36, the average discrete­semiconductorfamily scaling ratio. 

The narrower the component category, however, the fewer matches there are between 

SME and iSuppli cost estimates from which to calculate an average scaling ratio. Because DOE 

performed matching on a limited set of teardowns (i.e., the three BC units), some categories had 

no matches, while many more had only one match. As with the price substitutions, an average 

ratio based on only a few matches may not be representative of the relationship between lowvolume and high­volume costs for all components within that category. 

Therefore, when DOE selected which scaling ratio to use for a particular category, the 

standard deviation of the scaling ratios for matches within that category and its broader parent 

categories (if any) were compared, and the average scaling ratio of the category with the lowest 

standard deviation was used. 

Using the above example, there was only one match between SME and iSuppli cost 

estimates for 2–5 A rectifier diodes, so no standard deviation could be calculated. Therefore, the 

scaling ratio for the parent category (i.e., rectifier diodes, which had five matches) was used, and 

the SME cost estimates for 2–5 A rated rectifier diodes were multiplied by 0.21 (the general 

rectifier diode scaling ratio) to arrive at a high­volume cost estimate. Thus, even though the 

broader parent category includes a greater diversity of components, the larger number of 

components it contains may lead to a lower variation in the scaling ratio, as reflected in the 

standard deviation. 

3.2.5.4 Substitute Category­Average iSuppli Component Costs

Finally, in several of the EPSs torn down by the SMEs, DOE was unable to estimate 

some of the low­volume costs for a few components. Although most components are either 

identified with specific part numbers or other markings (e.g., transistors) or are generic enough 

that such markings are unnecessary when estimating cost (e.g., surface­mount capacitors), some 

components fall into neither of these groups. 

In particular, some integrated circuits are custom­made for a specific application so their 

part number cannot be found in a component catalog, making identification and pricing 

intractable. Alternatively, some diodes and many surface­mount discrete semiconductors may 

lack part numbers entirely, displaying instead a short manufacturing code that may distinguish 

the component from others made by the same manufacturer. However, such codes also do not 

appear in component catalogs. 

Nonetheless, it is possible to determine the component’s location and function in the 

circuit. Based on this information, DOE was able to categorize the component by type (e.g., 

transistor) and occasionally even by subtype (e.g., field­effect transistor). Subsequently, DOE 

proceeded to substitute the category­average iSuppli component cost, as described in section 

3.2.5.2. However, unlike in the original application of that method, the variability and number of 

samples upon which the averages were based were not considered, as this was the only method 

remaining for estimating the high­volume cost of these components. 

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3.2.6 Summary 

For the units that iSuppli tore down, DOE used iSuppli data exclusively. In cases where 

DOE not could obtain high­volume iSuppli cost estimates to support its non­Class A EPS 

engineering analysis, it relied on teardowns and low­volume cost estimates performed by its 

SMEs. As described above, the high­volume iSuppli component costs were then either directly 

substituted for the low­volume estimates obtained by the SMEs, or used to scale the SME 

estimates. The component costs thus adjusted were then compiled into a high­volume ERMC for 

the unit, for use in subsequent analysis. 

3.3 Scaling EPS Efficiency with Output Power 

The practically achievable efficiency of an EPS depends on its nameplate output power: 

lower­power EPSs tend to exhibit lower active­mode efficiencies than similar units with higher 

output powers. (Changes in output power do not impact the no­load power consumption.) 

However, some of the EPSs that DOE analyzed for the non­Class A engineering analysis differ 

in output power from the representative units for their product class. DOE therefore developed a 

model for estimating the change in active mode efficiency when the output power of an EPS is 

shifted to that of the representative unit. 

Figure 3.5 is a schematic representation of the EPS efficiency distribution with power, 

which shows the relationship between the two. Based on this distribution, DOE concluded that if 

a manufacturer were to design two similar EPSs with slightly different powers, the efficiency of 

the higher­power EPS would be higher, and vice versa. However, there is a wider range of 

efficiency at low output power than at high output power. Any shift of a manufacturer’s unit to 

the representative unit output power should therefore take into account both effects, preserving a 

unit’s relative standing in terms of efficiency among other units in the market. 

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Efficiency [%]

ENERGY STAR demarcates the 75th

percentile of efficiency.

Rated Output Power [W]
 

Figure 3.5 Schematic Illustration of the Distribution of Efficiency Versus Maximum 

Rated Output Power; the ENERGY STAR Level Is Shown as a Pink Line, while the Blue 

Background Indicates Where Most of the Units Lie 

A unit’s relative standing could be calculated by comparing its efficiency to the level 

specified in the ENERGY STAR EPS Eligibility Criteria Version 1.1 (2005)e as well as the bestin­market level, defined as the curve­fit of the highest­efficiency units in the ENERGY STAR 

qualifying products database. Because of the fundamental similarities in the design of Class A 

and non­Class A EPSs, DOE extended these same relationships and datasets to model the 

impacts on non­Class A EPS efficiency. 

To preserve the relative standing of the manufacturer’s unit in the market, while shifting 

the results to the representative unit output power, DOE maintained the ratios among the unit’s 

efficiency, the ENERGY STAR level, and the best­in­market level. Figure 3.6 illustrates this 

process, while Figure 3.7 shows how DOE generated the best­in­market curve­fit using the 

ENERGY STAR qualifying products database. Since no correlation has been found between noload power and output power, DOE did not scale the no­load power. 

e EPA, “ENERGY STAR Program Requirements for Single Voltage External Ac­Dc and Ac­Ac Power Supplies: 

Eligibility Criteria,” Ver. 1.1, 2005. 

http://www.energystar.gov/ia/partners/product_specs/program_reqs/archive/EPS_Eligibility_Criteria_V1.1.pdf 

3­16 

EERE-2009-BT-DET-0005 COMMENT 03
 

     

   

       

 

     

Shift

η BEST_IN_MARKET

Efficiency [%]

PMFR_UNIT PREP_UNIT

η′MFR_UNIT

η ENERGY_STAR

η MFR_UNIT

Rated Output Power [W]

Figure 3.6 Schematic Illustration of Scaling EPS Efficiency with Output Power 

0%

10%

20%

30%

40%

50%

60%

70%

80%

90%

100%

0 50 100 150 200 250

Rated Output Power [W]

Conversion Efficiency

Highest performing units

ENERGY STAR v. 1.1 level

Best­in­market level

Worst­in­market level

Figure 3.7 ENERGY STAR Level and Calculated Best­in­Market and Worst­in­Market 

Curves 

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DOE performed the shift in efficiency relative to the best­in­market and ENERGY STAR 

levels using the following equations: 

η′ =η′	 − r ⋅(η′ −η′ MFR _ UNIT BEST _ IN _ MARKET BEST _ IN _ MARKET ENERGY _ STAR )

Eq. 3.1 

and 

η	 

BEST _ IN _ MARKET MFR −η _ UNIT 

r =	 , η	 

BEST _ IN _ MARKET ENERGY −η _ STAR 

Eq. 3.2 

where: 

η MFR , η	 , and η are the efficiencies of the unit under analysis, _ UNIT BEST _ IN _ MARKET ENERGY _ STAR 

the best­in­market point, and the ENERGY STAR level, respectively, at the 

manufacturer­provided nameplate output power, while 

the primed terms refer to the same quantities at the nameplate output power of the representative 

unit, to which the unit efficiency is being scaled, and 

r is a scaling ratio that represents the position of the efficiency of the manufacturer­provided unit 

to that of other EPSs in the market. 

3.4 Scaling EPS Efficiency with Output Voltage 

3.4.1 Summary and Introduction 

Together with the nameplate output power, the nameplate output voltage constrains a 

power supply’s achievable efficiency. Given two EPSs with an identical design but different 

output voltages, the lower­voltage unit will be less efficient, primarily due to: 

•	 Resistive losses: outputting the same power at a lower voltage requires higher output 

current, increasing the resistive losses, which are proportional to the square of the 

current; and 

•	 Rectifier losses: the voltage drop across the output rectifier increases with higher 

current, such that at a lower voltage more power (current times the voltage drop 

across the rectifier) will be dissipated, decreasing the efficiency of the power supply. 

In addition to the above losses, the EPS also experiences fixed losses that do not depend on the 

output voltage. These losses are associated with, for example, the quiescent current of the 

controller IC for switched­mode designs or the core magnetization losses for line­frequency 

designs and are equal to the no­load power consumption of the power supply. The schematic in 

Figure 3.8 summarizes the loss mechanisms described above. 

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IQ ROUTPUT RCORD
 

+

−

+

-

VOUT

VS - VDIODE

+

Figure 3.8 Schematic of EPS Loss Model Used for Scaling Efficiency with Voltage 

When scaling the efficiency of a power supply with voltage, DOE first calculated the 

typical losses according to the model presented in Figure 3.8. Because the characteristics of each 

of the components in the loss model were fixed, the losses calculated using the model depended 

only on the output current and voltage, not the design specifics of the EPS. In short the model 

returned the same losses for any two EPSs with the same output characteristics, regardless of 

their designs. 

However, because each EPS has its own specific design, the actual losses of the power 

supply differ from those calculated according to this generic model. This difference between the 

modeled and actual losses does not depend on the output power or voltage, but is correlated 

instead with the active mode efficiency and no­load power of the EPS. Thus the actual losses of 

an EPS can be said to be the sum of two components: (1) generic losses, dependent on output 

power and voltage and modeled as described above; and (2) additional losses, dependent on the 

design of the EPS. Because the additional losses reflect the design of the EPS, and the purpose of 

scaling was to estimate the losses of a particular design at the representative­unit output power 

and voltage, the additional losses were held constant between the original EPS and the 

representative unit to which it was being scaled. 

Having obtained the generic losses for the original EPS using the model and its 

technology­dependent additional losses, the generic losses for the representative unit were 

calculated. These were then added to the technology­dependent additional losses, resulting in an 

estimate of the total losses of the EPS design at the representative­unit output power and voltage. 

The representative unit’s efficiency was finally calculated as the ratio of output power and the 

sum of the output power and the losses thus estimated. 

3.4.2 Experimental Basis 

As can be seen in Figure 3.9, there is a direct relationship between the nameplate output 

voltage and average active mode efficiency for EPS units within the same design family (group 

of EPSs that share a common output power and fundamental design, but vary in output voltage). 

Because of this relationship, it is possible to estimate the efficiency of one EPS unit given the 

voltage of the unit as well as the voltage and efficiency of another unit in the same EPS design 

family. Similarly, given the output voltage and efficiency of an EPS it is possible to estimate the 

efficiency at the output power and voltage of the representative unit. 

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0%

1%

2%

3%

4%

10 12 14 16 18 20 22 24

Nameplate Output Voltage [V]

Difference in Active Mode Efficiency

Relative to 12

V Unit

75 W EPS Family

60 W EPS Family 1

60 W EPS Family 2

60 W EPS Family 3

60 W EPS Family 4

Figure 3.9 Difference in Active Mode Efficiency vs. Nameplate Output Voltage 

The relationship displayed in Figure 3.9 is representative of higher­power, higher­voltage 

EPSs. However, the analysis of EPSs for BCs for the non­Class A determination required the 

aggregation of efficiency at the 1.8 W, 6 V and 4.8 W, 24 V representative unit powers and 

voltages for accurate comparison. Because the experimental data in Figure 3.9 does not extend to 

the output powers and voltages of these representative units, a different model was developed 

based on the losses inherent in the components of the EPS. 

There was no correlation between nameplate output voltage and no­load power 

consumption. 

3.4.3 Loss Calculations 

To scale the efficiency of a given EPS to the representative­unit output power and 

voltage, the losses in the EPS must first be modeled. These are assumed to conform to the 

simplified model below, which takes into account the quiescent losses, which are independent of 

the output voltage, as well as losses in the output cord, rectifier diode, and the output resistance 

of the EPS. This loss model is illustrated in Figure 3.8. The losses in each component are 

summarized in Table 3.8 Losses for Scaling Model for Efficiency with Output Voltage. 

Table 3.8 Losses for Scaling Model for Efficiency with Output Voltage 

Loss Type Power Loss Equation Explanation 

Quiescent 

Loss 

LOSS = PP −LOADNO Where: 

P LOSS is the power lost in the 

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modeled component; and 

P −LOADNO is the no­load power 

consumption of the EPS. 

Rectifier P LOSS = LOAD ⋅VI DIODE Where: 

Diode Loss 





 



 ⋅= ln +1

S 

LOAD 

TLOAD I 

I VI 

LOAD I is the load current; 

V T is the thermal voltage equal to 

0.026 V; and 

S I is the saturation current equal to 

1x10­12 . 

Cord 

Resistance 

Loss 

P LOSS LOAD RI CORD ⋅= 2 Where: 

LOAD I is the load current; and 

R CORD is the cord resistance. 

Output P LOSS LOAD ⋅= RI OUTPUT

2 Where: 

Resistance 

Loss 



 



 Δ ⋅= MAX 

OUT 

LOAD I 

V I 2 2 LOAD I is the load current; 

R OUTPUT is the output or source 

resistance; 

ΔV OUT is the voltage regulation (e.g., 

5% of the nameplate voltage); and 

MAX I is the nameplate output current. 

After the above component losses are calculated for an EPS at its original output power 

and voltage and at each loading condition, they are subtracted from the total unit power loss at 

each of the active mode loading conditions (25%, 50%, 75%, and 100% of nameplate output 

current) resulting in an additional loss term. This additional loss is related to the specifics of the 

EPS design; for example an EPS that uses a Schottky rectifier diode will have a lower diode 

voltage drop, resulting in lower rectification losses, and possibly a negative additional loss term. 

The relationship between the unit efficiency at a given loading condition and the component and 

additional losses is reflected in the equation below. 

P P OUT OUT POUT Eff = = = , P P IN OUT LOSS OUT LOSS + P P + P _ COMP LOSS + P _ ADD'L 

Where: 

Eff is the efficiency at a given loading condition; 

POUT is the output power at the loading condition; 

PIN is the input power at the loading condition; 

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PLOSS_COMP is the power lost by the unit modeled by the component losses at the loading 

condition; and 

PLOSS_ADD’L is the power lost by the unit not modeled by the component losses at the loading 

condition. 

Because the additional losses are technology dependent and do not show any correlation 

when plotted against output power or voltage, they are assumed to remain constant for EPSs in 

the same design family. This is not the case for the modeled component losses, which are 

dependent on the EPS output power and voltage and must be recalculated for each unit. The 

efficiency of the EPS scaled to representative unit power and voltage was therefore calculated as 

follows: 

P′ Eff ′ = OUT 

POUT LOSS ′ + P′ _ MODELED LOSS + P _ ADD'L 

Where: 

The primed quantities are calculated at the representative unit output power and voltage. 

The efficiencies thus calculated at each of the four active mode loading conditions are 

then averaged to obtain the representative­unit average active mode efficiency. The no­load 

power consumption does not depend on voltage, so it is assumed to remain constant when 

scaling to the representative unit. 

3.4.4 Conclusion and Examples 

The above model was used to develop the engineering curves for the EPSs for BCs 

analysis, which focused on two representative units with output power and voltage of 1.8 W, 6 V 

and 4.8 W, 24 V. Efficiency data on several low­power EPSs were first scaled to the 

representative­unit output power using their relative standing in the market. The above model 

was then used to adjust the efficiency to the representative­unit output voltage. The results 

returned by the model are illustrated in Figure 3.10. 

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30%

35%

40%

45%

50%

55%

60%

65%

70%

75%

80%

4.8 5 5.2 5.4 5.6 5.8 6 6.2

Nameplate Output Voltage

Average Active­Mode Effiiciency

Figure 3.10 Efficiencies of 5W, 5V EPS Test Units After Scaling to the 1.8 W, 6 V
­

30%

40%

50%

60%

70%

80%

90%

100%

0 5 10 15 20 25 30

Nameplate Output Voltage

Average Active­Mode Effiiciency

Representative Unit Level
­

Figure 3.11 Efficiencies of 5W, 5V EPS Test Units After Scaling to the 4.8 W, 24 V
­

Representative Unit Level.
­

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3.5 Cost Scaling by Nameplate Output Power and Sales Volume 

3.5.1 Introduction 

A wide variety of Non­Class A EPSs exists on the market in the product classes analyzed 

by DOE for the NCA EPS determination. Because analyzing every available EPS in each 

product class was not feasible, DOE chose one EPS in each product class as a representative unit 

of analysis in order to develop relationships between cost and efficiency. To supplement the 

cost­efficiency analysis, DOE also tore down a selection of other available EPSs in each product 

class to obtain data on efficiency, no­load power consumption, output power, ERMCs, and 

production volumes. 

DOE research suggests that for a given EPS design, the ERMC is dependent the output 

power of the EPS as well as its production volume. In order to compare costs and efficiencies of 

various EPSs and develop cost­efficiency curves, DOE had to account for variations in output 

power and production volume across the EPSs analyzed. DOE did this using a scaling model that 

estimated what the ERMC of a torn­down EPSs would be at the production volume and output 

power of the representative unit. The development of this model is described in the sections that 

follow. 

3.5.2 Observed Relationships in Available Data 

DOE used two datasets to develop the scaling model. The two datasets allowed DOE to 

assess relationships between materials cost, production volume, and output power. 

The first dataset was a confidential submission of EPS production cost data to DOE. This 

dataset contained production costs for EPSs with various output powers (including 5 W) at low 

volumes. DOE observed a linear statistical relationship (with R2 values of approximately 0.94) 

between manufacturer selling price and output power for EPSs in the dataset. 

The second dataset was a public submission of manufacturer selling price (MSP) to the 

California Energy Commission (CEC) in support of CEC’s 2006 appliance standards 

rulemaking.f This dataset contained MSP versus production volume data for 2 W and 5 W EPSs 

at high volumes. The relationship between MSP (and, hence ERMC) and production volume 

appeared to be nonlinear, as shown in Figure 3.12 (where production volume is plotted on a 

logarithmic scale). 

Based on the observed linear relationship between EPS output power and EPS production 

cost in the confidential dataset, DOE assumed that the relationship between EPS output power 

and MSP in the public dataset would also be linear. Linear trendlines and associated equations 

for the dataset are shown in Figure 3.13 for three different production volumes. 

f Available at: http://www.energy.ca.gov/appliances/archive/2006rulemaking2/documents/comments/NRDC.PDF. 

Last accessed March 2, 2009. 

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$0.00

$0.50

$1.00

$1.50

$2.00

$2.50

$3.00

$3.50

$4.00

$4.50

$5.00

MSP [$]

50,000

100,000

10,000,000

$2.50

$2.00

$1.50

MSP

$1.00

[$]

2 W

$0.50 5 W

$0.00

10,000 100,000 1,000,000 10,000,000 100,000,000

Shipment Volume (log scale)

Figure 3.12 Manufacturer Selling Price Versus Volume For Specific 2W and 5W EPSs
­

0 5 10 15 20 25

Output Power [W]

Figure 3.13 Manufacturer Selling Price Versus Output Power for Specific 2 W And 5 W 

EPSs at Different Production Volumes 

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$0

$5

$10

$15

$20

$25

Per­Unit Production Cost [$]

Incremental Cost

Total Cost

3.5.3 Model Development 

As mentioned above, there appears to be a nonlinear relationship between MSP and 

volume for EPSs.g DOE modeled this relationship as a sum of incremental and fixed costs, as 

illustrated in Figure 3.14. The per­unit incremental costs account for the component, labor, and 

other variables costs necessary to manufacture an EPS and do not vary with the number of EPSs 

manufactured.h The fixed costs, on the other hand, account for the capital and other one­time 

costs of manufacture, which are amortized across the number of units. 

Under this model, at single unit volume, the total cost of the unit would equal the cost of 

setting up the assembly line plus the incremental costs for the components, etc. On the other 

hand, at infinite volume, the fixed cost of setting up the assembly line would be distributed 

across the infinite number of units so the per­unit fixed costs would approach zero. The total perunit costs would therefore only equal the incremental costs. 

1,000 10,000 100,000 1,000,000

Volume ['000s] (Log Scale)

Figure 3.14 Example EPS materials Cost Modeled as a Sum of Fixed and Incremental 

Costs. 

Because the per­unit fixed costs approach zero at infinite volume and approach infinity at 

1 zero volume, DOE modeled them as proportional to x , where V is the volume and x, the V 

exponent, is a positive number. The per­unit total cost, which also includes a variable cost, can 

therefore be modeled as: 

g Because MSP is directly derived from the ERMC through markups, this discussion will focus on the latter term for 

consistency with the remainder of the engineering analysis. 

h A manufacturer may pay different prices for components purchased at different volumes, but DOE assumes that 

because the similarity in EPS designs, an EPS manufacturer purchases components at a volume much larger than 

that of an individual design and reuses the same components across several designs—e.g., a change in volume from 

10,000 to 100,000 will not have much of an effect if a manufacturer has purchased components in volumes of 10 

million. 

3­26 

EERE-2009-BT-DET-0005 COMMENT 03
Power (2 W)

 

 

 

 

 

 

 

 

 

 

 

 

 

 

   

   

   

   

     

   

 

 

 

 

ERMC = aV −b + c Eq. 3.6 

Where: 

ERMC = EPS efficiency­related materials cost;
­

a = Linear scaling term;
­

b = Positive exponent;
­

c = Offset term representative of the variable cost; and
­

V = EPS production volume.
­

To find the parameters a, b, and c, in the above model for the publicly available 5 W 

manufacturer data, DOE first chose a trial value for c, subtracted if from the ERMC, and 

performed a regression on 

ERMC − c = ERMC′ = aV −b Eq. 3.7 

DOE subsequently repeated the regression for different values of the variable­cost offset, 

c, to maximize the R2 value of the resulting curve fit. Once the resultant variable cost, c, was 

subtracted, the materials cost was equal to a power function of the volume with parameters a and 

b. An illustration of this curve­fit can be seen in, with the values for a and b listed directly on the 

figure. 

MSP ­ Offset [$]

$0.70

$0.60

$0.50

$0.40

$0.30

$0.20

$0.10

$0.00

2 W

5 W

= 138.85x­0.4985 y

R2 = 0.9997

y = 135.9x­0.5224

R2 = 1

10,000 100,000 1,000,000 10,000,000 100,000,000

Shipment Volume (log scale)

Figure 3.15 Offset Efficiency­Related Materials Cost Versus Volume for Specific 2W and 

5W EPSs 

As could be seen in Figure 3.15, it was possible to determine the model for either a 2 W 

or 5 W EPS based on the data provided. Going forward, however, DOE used the 5 W model 

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exclusively because of the second, confidential dataset, which included MSP data at low 

volumes for a 5 W EPS. By combining these two datasets, DOE was able to increase the 

robustness of the scaling model at low production volumes. 

Figure 3.16 shows the ERMC versus output power for the publicly available 2 W and 

5 W data. As before, the 2 W and 5 W points at constant volume are connected with linear 

trendlines. Note that the 2 W/5 W trendlines intersect, roughly at the same point, forming a 

family of curves that describe the cost of a particular design as one adjusts output power and 

production volume. 

­$1.00

$0.00

$1.00

$2.00

$3.00

$4.00

$5.00

­15 ­5 5 15 25

MSP [$]

50,000

100,000

10,000,000

Output Power [W]

Figure 3.16 Extended Trendlines Based on Publicly Available EPS Data 

Figure 3.17 adds the trendline for the confidential dataset to the extended trendlines in 

Figure 3.16. The exact volume at which the prices are displayed has been withheld to protect 

proprietary manufacturer information. It is clear, however, that the volumes must be much lower 

than those previously displayed. 

Despite this stark difference in volume and manufacturer,i this new trendline intersects 

the earlier trendlines near where they intersect each other. Even though the intersections are 

imperfect, DOE nonetheless was able to incorporate this trendline into its family of curves by 

taking the x­ and y­coordinates of the average intersection point, and setting this average as the 

common intersection point for the entire family of curves. 

i Even though a different manufacturer provided the information underlying this trendline, all data pertains to similar 

designs able to meet the same efficiency levels. 

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MSP [$]

$12.00

$10.00

$8.00

$6.00

$4.00

$2.00

$0.00

25

­$2.00

50,000

100,000

10,000,000

Confidential Dataset

­15 ­10 ­5 0 5 10 15 20

Output Power [W]

Figure 3.17 Extended trendlines with confidential dataset trendline added. 

The resultant family of curves models the dependence of ERMC on output power and 

production volume, taking into account the data of two manufacturers spanning several decades 

of shipment volumes. This family of curves is described by Eq. 3.8, which captures the linear 

dependence on output power as well as the nonlinear dependence on volume. The calculated 

values for all the parameters are summarized in Table 3.9. 

aV −b + c −Y ERMC = (P − X )+Y Eq. 3.8 P5W − X 

Where: 

ERMC = EPS efficiency­related materials cost; 

a = Linear scaling term; 

b = Positive exponent; 

c = Offset term representative of the variable cost; 

V = EPS production volume; 

P = EPS output power; 

P5W = Output power of 5 W EPS; 

X = X coordinate (power) of average trendline intersection 

point; and 

Y = Y coordinate (cost) of average trendline intersection point. 

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Table 3.9 Value of Calculated Model Parameters
­

Parameter Calculated Value 

a 128.64

b 0.49

c $1.45

P5W 5 W 

X ­5.7 W

Y $0.47

The parameters are assumed fixed; thus, the relationship and its associated parameters is 

assumed reasonable enough to allow scaling across the range of production volumes and output 

powers of the torn­down EPSs and representative units. 

3.5.4 Model Deployment 

With this relationship in hand, DOE was able to estimate changes to ERMC that would 

result from changes to the unit output power and/or production volume. Given a known ERMC, 

output power, and production volume of a torn­down EPS, together with a known representative 

unit output power and production volume, DOE used Eq. 3.9 to estimate the ERMC that the torndown EPS would have at the representative unit output power and production volume. 

−b  c −
 

(

( ) aV
�R + Y  − +



















P X
� Y R P5 W − X

ERMC
� =
 ERMC Eq. 3.9
­ Scaled −b T

aV
� + c − Y ) T 

P5 

PT − X
� + Y
�

W − X

Where:
­

ERMCScaled = Torn­down EPS efficiency­only materials cost at 

representative output power and production volume 

ERMCT = Torn­down EPS original efficiency­only materials cost; 

a = Linear scaling term; 

b = Positive exponent; 

c = Offset term representative of the variable cost; 

V = EPS production volume; 

PR = Representative unit output power; 

PT = Torn­down EPS output power; 

P5W = Output power of 5 W EPS; 

X = X coordinate (power) of average trendline intersection 

point; and 

Y = Y coordinate (cost) of average trendline intersection point. 

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3.6 Representative Product Classes and Representative Units 

3.6.1.1 Representative Product Classes and Units for Multiple­Voltage EPSs

DOE proposed two product classes for multiple­voltage EPSs. Because those product 

classes are sufficiently different from each other, DOE used both as representative product 

classes (Table 3.10). 

Table 3.10 Representative Product Classes for Multiple­Voltage EPSs 

Nameplate Output Power 

< 100 watts ≥100 watts 

Product Class Multiple­Voltage Product Class 1 Multiple­Voltage Product Class 2 

DOE chose one representative unit for each representative product class based on a 

market survey it conducted that identified popular nameplate output powers among multiplevoltage EPSs (Figure 3.18). The survey counted the number of products available in online 

distributor catalogs, including Mouser.com and Jameco.com, which sell multiple­voltage EPSs 

independent of an end­use consumer product. The survey also included websites, such as 

Amazon.com and RadioShack.com, that offer replacement EPSs for existing products. Typically, 

multiple­voltage EPSs are sold packaged with end­use products; however, DOE evaluated 

individual multiple­voltage EPSs because it could not obtain detailed data for EPSs sold with 

end­use products. In total, the survey counted 129 unique multiple­voltage EPSs. Most of the 

multiple­voltage EPSs in the survey had nameplate output power below 70 watts, with popular 

ratings at 10 watts, 20 watts, and 40 watts. In addition, there were three EPSs with nameplate 

output power at 203 watts for use with a video game console. 

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0

5

10

15

20

25

Product Count [#]

0 5 10 15 20 25 30 35 40 45 50 55 60 65 70 . . . 203

Nameplate Output Power [W]

Figure 3.18 Product Count for Multiple­Voltage EPSs 

Based on the market survey, DOE decided to have two representative units with 

nameplate output power at 40 watts and 203 watts. Originally, DOE considered using nameplate 

output voltages at 5 V and 12 V for the 40­watt representative unit because that was the most 

popular voltage combination in the survey. However, during manufacturer interviews it became 

clear that 40­watt EPSs with that output voltage combination were legacy products in a very 

small and shrinking market. Because of that, DOE selected the output voltages for the 40­watt 

unit to be 16 V and 32 V, which are a popular voltage combination for EPSs used in printing 

applications. 

Printing and video game applications are by far the most popular uses for multiplevoltage EPSs. The 203­watt representative unit corresponds to the EPS used with the Microsoft 

Xbox 360, currently the only video game console to use a multiple­voltage EPS. Therefore, the 

unit’s combination of output voltages corresponded to that of the Xbox 360: 5 volts and 12 volts. 

In researching the market, DOE noted that there is a trend for EPSs for video game consoles to 

use EPSs with lower output powers. Specifically, the Xbox 360 originally used a 203­watt EPS, 

but uses a 175­watt EPS currently. This occurs because the video game console requires less 

power, in part due to improvements in its components. In the future, the video game console will 

probably use an EPS with even lower output power. Nonetheless, DOE analyzed a 203­watt EPS 

because it is the most established EPS, having multiple manufacturers. DOE believes that it can 

scale results for the 203­watt EPS to lower power EPSs in future analyses. A full list of multiplevoltage EPS design parameters that DOE fixed for isolating the impacts of efficiency is 

presented in Table 3.11. 

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Table 3.11 Characteristics of the Multiple­Voltage EPS Representative Units
­

Parameter Values for 40 W EPS Values for 203 W EPS 

Output Voltages and Currents V1 = 16 V, I1 = 0.625 A, 

V2 = 32 V, I2 = 0.940 A 

V1 = 5 V, I1 = 1 A, 

V2 = 12 V, I2 = 16.5 A 

Input Voltage 115 volts rms, 60 Hz 115 volts rms, 60 Hz 

Input Protection Primary current fuse, 

inrush current limiting 

Primary current fuse, inrush 

current limiting 

Output Voltage Regulation ± 5% (excluding cord) ± 1% (excluding cord) 

Output Voltage Ripple 2% VP­P maximum 1% VP­P maximum 

Transient Response 0.5 ms for 50% load 

change typical 

0.5 ms for 50% load change 

typical 

Output Protection Overcurrent protection, 

short­circuit protection 

Overcurrent protection, 

short­circuit protection 

Unit Volume 1M units per year 4M units per year 

Application Multi­Function Device Video Game System 

Package Sealed polycarbonate Sealed polycarbonate 

Output Cord Length 6 feet 6 feet 

Regulatory Compliance UL, FCC UL, FCC 

Product Lifetime 5 years 5 years 

3.6.1.2 Representative Product Classes and Units for High­Power EPSs

DOE proposed one product class for high­power EPSs which it used as a representative 

product class (Table 3.12). Since ham radios are essentially the only end­use consumer 

application for high­power EPSs, the nameplate output voltage of the representative unit was 

13.8 volts corresponding to the standard ham radio operating voltage. 

Table 3.12 Representative Product Classes for High­Power EPSs 

Nameplate Output Power 

> 250 watts 

Product Class High­Power Product Class 1 

DOE chose one representative unit within the representative product class based on a 

market survey it conducted that identified popular nameplate output powers among high­power 

EPSs (Figure 3.19). The survey counted the number of products available in online distributor 

catalogs that sell high­power EPSs for use with ham radios, including UniversalRadio.com and 

AESham.com. Typically, high­power EPSs are purchased through these types of ham radio part 

distributors separately from other ham radio products; therefore this data gathering method 

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reflects the high­power EPS market. However, there was a limited amount of EPSs available 

because ham radios are a niche application. Nonetheless, the survey counted 37 unique highpower EPSs. Among those units there was a range of nameplate output power from 276 watts to 

786 watts. DOE selected 345 watts because it was the most popular (9 units available) and is in 

the middle of the output power range for all units. Because the output power is in the middle of 

the range, DOE believes that it will be easier to scale the results of the 345­watt EPS across the 

whole range of high­power EPSs. A full list of high­power EPS representative unit design 

parameters that DOE fixed for isolating the impacts of efficiency is presented in Table 3.13. Number of Units [#]

10

8

6

4

2

0

276 303.6 317.4 345 414 510.6 552 690 786.6

Nameplate Output Power [W]

Figure 3.19 Product Count for High­Power EPSs
­

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Table 3.13 Characteristics of the High­Power EPS Representative Unit
­

Parameter Values for 345 W EPS 

Output Voltages and Currents V1 = 13.8 V, I1 = 25 A 

Input Voltage 115 volts rms, 60 Hz 

Input Protection Primary current fuse, inrush 

current limiting 

Output Voltage Regulation ± 1% (excluding cord) 

Output Voltage Ripple 1% VP­P maximum 

Transient Response 0.5 ms for 50% load change 

typical 

Output Protection Overcurrent protection, 

short­circuit protection 

Unit Volume 1,000 units per year 

Application Ham radio 

Package Metal enclosure with slats 

and fan. 

Output Cord Length 6 feet 

Regulatory Compliance UL, FCC 

Product Lifetime 10 years 

3.6.1.3 Representative Product Classes and Units for Medical EPSs

DOE proposed six product classes for medical EPSs and identified similarities between 

medical EPSs and Class A EPSs. Because of these similarities, DOE chose only one 

representative product class and one representative unit for medical EPSs (Table 3.14). 

Table 3.14 Representative Product Classes for Medical EPSs 

Nameplate 

Output Voltage 

Nameplate Output Power 

4–60 watts 

≤12 volts Medical Product Class 2 

DOE chose the medical EPS representative unit based on a market survey it conducted 

that identified popular nameplate output powers among medical EPSs (Figure 3.20). The survey 

counted the number of individual medical EPSs available in online distributor catalogs, including 

Newark.com and AlliedElec.com. Typically, medical EPSs are sold packaged with end­use 

products; however, DOE evaluated medical EPSs sold separately because it could not obtain 

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detailed data for EPSs sold with medical products. In total, the survey counted 86 unique medical 

EPSs. In the survey, most of the units had less than 70 watts nameplate output power. There was 

a cluster of units with nameplate output power near 18 watts. EPSs with nameplate output power 

at 50 watts and 60 watts were also popular. DOE chose 18 watts for the medical EPS 

representative unit because it is a popular wattage and it is the same output power as the Class A 

EPS representative unit. A full list of high­power EPS representative unit design parameters that 

DOE fixed for isolating the impacts of efficiency is presented in Table 3.15. 

25
 

20
 

15
 

10
 

5
 

0
 

Figure 3.20 Product Count for Medical EPSs Product Count [#]

0 10 20 30 40 50 60 70 80 90 100 110 120
 

Nameplate Output Power [W]

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Table 3.15 Characteristics of the Medical EPS Representative Unit
­

Parameter Values for 18 W EPS 

Output Voltages and Currents V1 = 12 V, I1 = 1.5 A 

Input Voltage 115 volts rms, 60 Hz 

Input Protection Primary current fuse, inrush 

current limiting 

Output Voltage Regulation ± 1% (excluding cord) 

Output Voltage Ripple 1% VP­P maximum 

Transient Response 0.5 ms for 50% load change 

typical 

Output Protection Overcurrent protection, 

short­circuit protection 

Unit Volume 10,000 units per year 

Application Medical diagnostic 

Package Sealed polycarbonate 

Output Cord Length 6 feet 

Regulatory Compliance UL 60601­1, FCC 

Product Lifetime 8 years 

Also, among the 86 medical EPSs surveyed, five units had multiple voltage outputs. 

Because this group was so limited, DOE did not create a separate product class and 

representative unit for it. However, medical EPSs with multiple­voltage outputs may be 

considered in future analyses and/or rulemakings. 

3.6.1.4 Representative Product Classes and Units for EPSs for BCs

DOE proposed six product classes for EPSs for BCs and identified similarities between 

EPSs for BCs and Class A EPSs. Because of these similarities, DOE chose two representative 

product classes for EPSs for BCs (Table 3.16). 

Table 3.16 Representative Product Classes for EPSs for BCs 

Nameplate 

Output Voltage 

Nameplate Output Power 

<4 watts 4–60 watts 

≤12 volts EPS for BC Product Class 1 

>12 volts EPS for BC Product Class 5 

DOE chose the EPSs for BCs representative units based on previous analysis of BCs, 

detailed in the Framework Document and Draft Technical Report. That analysis identified four 

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representative units for battery chargers. Table 3.17 lists their characteristics along with the 

characteristics of their wall adapters. Among these four units, three use wall adapters that were 

considered as possible representative units for EPSs for BCs: wall adapters for shavers, vacuums, 

and do­it­yourself tools, which could be considered EPSs for BCs if they meet the scope of 

DOE’s Approach A for EPSs and BCs discussed in the technology assessment section of the 

NOPR. 

Table 3.17 Representative Unit Characteristics for Battery Chargers 

Application 

Wall­Adapter 

Characteristics Battery Charger Characteristics 

Output 

Power [W] 

Output 

Voltage [V] 

Battery 

Voltage [V] 

Battery 

Capacity [Ah] 

Charge 

Rate [C] 

Shaver 0.3 3 1.2 1.2 0.1 

Vacuum 1.8 6 4.8 1.2 0.1 

DIY tool 4.8 24 18 1.5 0.15 

Pro tool N/A N/A 18 2.4 1 

In addition to the three wall adapters from the BC representative units, DOE also 

considered wall adapters for camcorders because they were identified as a unique application 

that uses detachable batteries. To decide which among these four possible units would be used as 

representative units, DOE estimated the total energy consumption for all units sold in a year. 

DOE chose this metric since it is a good indication of potential savings and impact. Also, DOE 

could not use the market survey method it used with the other non­Class A EPSs because it is 

still developing a method for distinguishing EPSs for BCs from other BCs for wall adapters. 

To estimate energy consumption, DOE used data listed in Table 3.18 in addition to the 

data previously discussed. Figure 3.21 presents the estimated total energy consumption for the 

wall adapters that would be considered EPSs for BCs under DOE’s Approach A.j Among these 

applications, vacuums and DIY tools consume more than 10 GWh/yr whereas shavers and 

camcorders consume less than 2 GWh/yr. Therefore, DOE selected as the representative units for 

EPSs for BCs a 1.8­watt EPS for a vacuum and 4.8­watt EPS for a DIY tool, characteristics of 

which are detailed in Table 3.19. 

Table 3.18 Assumptions for Calculating Annual Energy Consumption 

Application 

Amount of BC wall adapters 

that are EPSs for BCs* [%] 

Monthly Use 

[uses per month] 

Amount Typically 

Unplugged After Use [%] 

Shaver 5 ** 4 90 

Vacuum 5 ** 4 10 

DIY tool 5 ** 2 20 

Camcorder 5 ** 0.5 90 

* Based on DOE’s Approach A scope of EPSs for BCs.
­

** The true percentage is lower. Five percent was used as a maximum value.
­

j These estimates are preliminary. More thorough calculations are in section 5.1 

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20,000,000

15,000,000

10,000,000

5,000,000

0

Shaver Vacuum DIY Power Tool Camcorder

Application of EPS for BC

Figure 3.21 Estimate of Energy Consumption for Different EPSs for BCs Estimate of Annual Energy Consumption [kwh/hr]

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Table 3.19 Characteristics of the EPS for BCs Representative Units
­

Parameter Values for 1.8 W EPS Values for 4.8 W EPS 

Output Voltages and Currents V1 = 6 V, I1 = 0.3 A V1 = 24 V, I1 = 0.2 A 

Input Voltage 115 volts rms, 60 Hz 115 volts rms, 60 Hz 

Input Protection ­ ­

Output Voltage Regulation ­ ­

Output Voltage Ripple ­ ­

Transient Response ­ ­

Output Protection ­ ­

Unit Volume 1M units/year 1M units/year 

Application Cordless Hand Vacuum Cordless DIY Power Tool 

Package Sealed plastic Sealed plastic 

Output Cord Length 6 feet 6 feet 

Regulatory Compliance UL, FCC UL, FCC 

Product Lifetime 5 years 5 years 

3.7 Selection of Candidate Standard Levels 

CSLs are generally based on (1) efficiencies achievable by commonly used design 

options, (2) voluntary guidelines or mandatory standards already in existence that have prompted 

manufacturers to develop products at particular efficiency levels, and (3) the max­tech level.k For 

example, DOE often considers the ENERGY STAR level as one CSL, while the least efficient 

models in a product class typically serve as the baseline CSL. Basing CSLs on established 

guidelines or standards increases the availability of data because manufacturers may have 

already designed products to meet the CSL, and may therefore be able to provide cost 

information. Furthermore, products meeting the CSL may exist in the marketplace and be 

available for testing and teardowns, further strengthening the analysis. 

Specifically in this analysis CSLs are based on (1) EPSs that have been tested and torn 

down, (2) data points provided in manufacturer interviews and (3) the International Efficiency 

Marking Protocol for External Power Supplies.l In choosing the basis for the CSLs, DOE gave 

k The max­tech level represents the most efficient design that has been demonstrated in a prototype with materials or
­

technologies available today. Max­tech is not constrained by economic justification, and typically is the most
­

expensive design option considered in the engineering analysis.
­ l Energy Star. International Efficiency Marking Protocol for External Power Supplies. 2008.
­

www.energystar.gov/ia/partners/prod_development/revisions/downloads/International_Efficiency_Marking_Protoco
­

l.pdf (Last accessed November 18, 2008.)
­

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the highest priority to units that were torn down and tested because DOE had complete data for 

efficiency and cost. If test and teardown data were not available then DOE used data points 

provided by manufacturers. Last, if no data were directly available, DOE referred to the 

International Marking Protocol. Where possible, DOE tried to relate CSLs to design options. 

However, even if CSLs are based on design options in units currently being 

manufactured, they should not be seen as technologically prescriptive. In other words, 

manufacturers are free to use any combination of design options to achieve the efficiency 

specified by a given CSL. To maintain this approach throughout the analysis, DOE did not 

examine CSLs that could only be achieved through proprietary design options not available to all 

manufacturers. 

The CSLs are specified in terms of the efficiency metrics utilized in DOE’s test 

procedure for single­voltage EPSs and a proposed test procedure for multiple­voltage EPSs: 

active mode conversion efficiency and no­load mode power consumption. Because both of the 

efficiency metrics output by the EPS test procedure affect the energy consumption of the unit, 

DOE developed CSLs that included “matched pairs” of limits on both metrics simultaneously. 

Matched pairs allowed DOE to base CSLs on existing EPS standards, such as those developed by 

ENERGY STAR. As these CSL matched pairs progress from least to most efficient, either the 

active mode efficiency or no­load power­consumption requirements, or both, increase in 

stringency. By preventing a decrease in the stringency of these metrics, DOE makes a tacit 

assumption that there is no trade­off between EPS performance in the two modes, and increasing 

the energy savings in one mode does not necessarily cause a decrease in energy savings in the 

other. 

To verify this assumption, DOE analyzed the relationship between active mode efficiency 

and no­load power consumption for products currently in the market. Figure 3.22 plots efficiency 

measurements conducted by DOE on EPSs with nameplate output power around 5 watts and 

60 watts. The figure shows that EPSs with higher active mode efficiencies tend to also have 

lower no­load­mode power consumption. This is probably true only up to a point, however, and 

one can imagine cases in which an EPS manufacturer tries to minimize no­load power, but can 

only do so at the expense of lower active mode efficiency. Therefore, DOE based its matched 

pairs on those currently seen in the market. The CSLs followed—as much as possible—the 

efficiency metrics achieved by actual EPSs at representative­unit output powers and voltages. 

This ensured that EPSs currently produced would be able to meet both active mode and no­loadmode requirements. 

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0

0.5

1

1.5

2

2.5

No­Load Power [W]

0–6 Watts Maximum Rated Output Power

40–66 Watts Maximum Rated Output Power

20% 30% 40% 50% 60% 70% 80% 90%

Average Efficiency [%]

Figure 3.22 Comparison of Active Mode Efficiency and No­Load Power; Arrows Point in 

Direction of Increased Efficiency 

For each of the six representative units, DOE created four CSLs, although it may create 

more levels in future analysis or in response to stakeholder comment. These CSLs are intended 

to reflect the efficiencies in the market, although they do not necessarily include the highest 

efficiencies. The CSLs in this analysis are sufficient for the determination analysis to 

demonstrate whether DOE should conduct a standards rulemaking. In future analysis, DOE may 

include a max­tech CSL to reflect the highest achievable efficiency. 

3.7.1.1 Candidate Standard Levels for Multiple­Voltage EPSs

On behalf of DOE, Navigant Consulting, Inc. collected data from original equipment 

manufacturers (OEMs) of multi­function devices and video games that use multiple­voltage 

EPSs with their products as well as EPS manufacturers themselves. In addition, DOE tested the 

efficiency of two EPSs for multiple­function devices and four EPSs for video games. These 

data sources indicated that there is a limited spectrum of efficiencies in the multiple­voltage 

EPS market, typically with conversion efficiency above 80%. No­load power for multiplefunction devices tended to be less than one watt whereas DOE measured EPSs for video game 

consoles with no­load power greater than 12 watts. 

Table 3.20 and Table 3.21 show the CSLs for the two multiple­voltage EPSs. 

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Table 3.20 Candidate Standard Levels for a 40­Watt Multiple­Voltage EPS for a MultiFunction Device 

Level Reference Minimum 

Efficiency [%] 

Maximum 

No­Load Power [W] 

Basis 

0 Current Market 80.8 0.50 Manufacturer interview 

1 Mid level 85.9 0.45 Manufacturer interview 

2 High level 89.9 0.31 Manufacturer interview 

3 Higher level 90.9 0.20 Manufacturer interview 

Table 3.21 Candidate Standard Levels for a 203­Watt Multiple­Voltage EPS for a Video 

Game Console 

Level Reference Minimum 

Efficiency [%] 

Maximum 

No­Load Power [W] 

Basis 

0 Generic Replacement 82.4 12.33 Tested unit (#213) 

1 Manufacturer Provided 86.4 0.40 Tested units (#206, 

#214) 

2 EU Qualified Level 86.4 0.30 Manufacturer 

interview 

3 Higher level 88.5 0.30 Manufacturer 

interview 

DOE created CSLs for the 40­watt EPS based on values provided by a manufacturer 

during an interview. The manufacturer provided cost­efficiency points at four levels in terms of 

both maximum efficiency and no­load power consumption. The manufacturer describes an EPS 

meeting CSL 0 as a switched­mode EPS with a flyback topology. To achieve the higher 

efficiency of CSL 1, the metal–oxide–semiconductor field­effect transistor (MOSFET) that 

controls the current into the transformer could be replaced with a MOSFET with lower resistance 

when turned on (Rds_on). To meet CSL 2 the manufacturer would design an EPS with three major 

changes in addition to maintaining the MOSFET with lower Rds_on: (1) use a more advanced 

integrated circuit (IC) with a more efficient switching algorithm, (2) use a transformer with 

lower losses, and (3) change the output diode from a standard diode to a Schottky diode. Last, to 

meet CSL 3, the EPS would have synchronous rectification instead of a Schottky diode and the 

transformer, chokes, and MOSFET would all have low losses. 

The manufacturer’s range efficiencies encompassed the measured efficiencies of EPS 

#217 (85.7% efficient, 0.27 watts no­load power) and EPS #218 (84.4% efficient, 0.26 watts noload power). Originally, the manufacturer provided the conversion efficiency values in terms of 

efficiency at full load (100% of nameplate output current) rather than at average loading, which 

is DOE’s metric. DOE analysis of EPSs #217 and #218 indicate that their average efficiency was 

1.01 times higher than the full­load efficiency. Therefore, DOE multiplied the original 

manufacturer maximum efficiency points by 1.01 to estimate the average efficiency. There was 

no need to adjust the no­load power, which DOE used directly in the CSLs. EPSs #217 and #218 

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meet CSL 0 because their efficiency is not greater than the efficiency at CSL 1. DOE chose to 

maintain the manufacturer’s levels for consistency between the matched pairs and because the 

no­load power is an indication of a maximum, so there was no conflict if the tested units had 

lower no­load power than the candidate standard level. 

For candidate standard level 0 and CSL 1 for the 203­watt EPS, DOE based its CSLs on 

units measured in the market. Specifically, CSL 0 reflects the efficiencies of generic replacement 

EPSs made by manufacturers other than Microsoft. DOE tested two such EPSs whose 

efficiencies were lower than the EPS currently provided by the video game manufacturer: EPS 

#213 (82.4% efficient, 12.33 watts no­load power) and EPS #216 (81.2% efficient, 5.16 watts 

no­load power). DOE based CSL 0 directly on the tested values measured for EPS #213 because 

it also obtained an estimated ERPC for the unit. Maintaining the same source for both allows for 

consistency between the EPS cost and efficiency. 

For the 203­watt EPS, CSL 1 is supposed to reflect the efficiency of the 203­watts EPSs 

that were sold with the Xbox 360 game console. DOE based CSL 1 on two units: the conversion 

efficiency of EPS #203 (86.4% efficient, 3.29 watts no­load power) and the no­load power of 

EPS #214 (84.5% efficient, 0.4 watts no­load power). DOE used two different units because of 

possible discrepancies within the data. In particular, DOE purchased EPS #203 individually (as 

opposed to being sold with the game console) through a third­party retailer on Amazon.com. 

Because EPS #203 was not purchased with the game console, DOE cannot definitively confirm 

that the EPS is an authentic Microsoft product, despite having a Microsoft label. Further, 

Microsoft reported to DOE that the original 203­watt EPS it used with the console has a no­load 

power of approximately 0.4 watts.m To that end, Microsoft provided DOE with EPS #214, which 

DOE tested to verify Microsoft’s assertion. Therefore, DOE used the conversion efficiency from 

EPS #203 because DOE has an estimate of the ERPC for this unit. However, the no­load power 

comes from EPS #214 to better reflect the no­load power consumption of products sold in the 

market. 

Candidate standard level 2 and CSL 3 come from manufacturer interviews with Microsoft 

who detailed methods for improving the no­load power and conversion efficiency of the 203­

watt EPS. CSL 2 reflects a reduction in no­load power to 0.3 watts. To achieve this Microsoft 

reduced losses in the transformer core, changed the switching frequency, and optimized the 

circuitry of the EPS. n Microsoft originally designed the EPS for lower no­load power 

consumption as part of an effort to comply with the European Union standard for a maximum of 

one­watt standby power consumption (when the console is turned off and attached to the EPS), 

hence CSL 2 is referred to as the “EU qualified level.” In addition, Microsoft believes that it can 

increase the conversion efficiency of the EPS by 2.15% by replacing Schottky diodes with a 

synchronous rectification circuit and by using MOSFETs with lower Rds_on.

o 

m Calland, T. Personal communication. Microsoft Corp, Redmond, WA. Email to Michael Vladimer, Navigant
­

Consulting, Inc. February 9, 2009.
­ n Calland, T. Personal communication. Microsoft Corp, Redmond, WA. Email to Michael Vladimer, Navigant
­

Consulting, Inc. February 9, 2009.
­ o Calland, T. Personal communication. Microsoft Corp, Redmond, WA. Email to Victor Petrolati, DOE, and 

Michael Vladimer, Navigant Consulting, Inc. November 4, 2008. 

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3.7.1.2 Candidate Standard Levels for High­Power EPSs

DOE developed candidate standard levels for the 345­watt representative unit for highpower EPSs based on data from tested and torn down units as well as manufacturer interviews. 

On behalf of DOE, Navigant Consulting, Inc. collected data from distributors and manufacturers 

of power supplies for ham radios. In addition, DOE tested the efficiency of four high­power 

EPSs. These data sources indicated that there is a wide, divided spectrum of efficiencies in the 

high­power EPS market: lower efficiencies for line­frequency power supplies and higher 

efficiencies for switched­mode power supplies. Table 3.22 shows the CSLs for high­power 

EPSs. 

Table 3.22 Candidate Standard Levels for a 345­Watt High­Power EPS for a Ham Radio 

Level Reference Minimum 

Efficiency [%] 

Maximum 

No­Load 

Power [W] 

Basis 

0 Line Frequency 62.4 15.43 Tested unit (#401) 

1 Switched­mode ­ Low 

Level 

81.3 6.01 Tested unit (#402) 

2 Switched­mode ­ Mid 

Level 

83.5 1.50 Manufacturer 

interview 

3 Switched­mode ­ High 

Level 

85.0 0.50 Manufacturer 

interview 

The lowest CSL corresponds to line frequency EPSs. DOE tested two line frequency 

EPSs: EPS #401 (62.4% efficient, 15.43 watts no­load power) and EPS #404 (50.7% efficient, 

12.6 watts no­load power). DOE used EPS #401 as the sole basis for CSL 0 because that unit 

was costed by iSuppli which allows the cost for the CSL to be related to an exact data point. 

Similarly, DOE based CSL 1 on the tested values of a switched­mode EPS #402 (81.3% 

efficient, 6.01 watts no­load power) because iSuppli also costed this unit. CSL 2 and CSL 3 

came from interviews with a designer and distributor of high­power EPSs. Specifically, the highpower EPS designer indicated that the higher efficiency of CSL 2 could be achieved by using an 

IC with a more efficient switching algorithm. The distributor of high­power EPSs indicated that 

higher efficiencies such as CSL 3 were possible by changes such as replacing rectifying diodes 

with a synchronous rectification circuit. Candidate standard levels 2 and 3 were verified as 

reasonable by a subject matter expert familiar with high power EPSs.p 

3.7.1.3 Candidate Standard Levels for Medical Device EPSs

DOE developed candidate standard levels for the 18­watt representative unit for medical 

device EPSs based on data from manufacturer interviews, laboratory testing, and the 

international efficiency marking protocol. On behalf of DOE, Navigant Consulting, Inc. 

collected data from medical device EPS manufacturers. Manufacturers indicated that medical 

p Rodriguez, E. Personal communication. OptoThermal Technologies, Wakefield, MA. Telephone conversation with 

Michael Vladimer, Navigant Consulting, Inc. February 5, 2009. 

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requirements should not affect an EPS’s efficiency. DOE verified that assertion by testing two 

medical EPSs and comparing them to four Class A EPSs. These test data indicated that 

efficiencies are comparable between the two types of EPSs. Therefore DOE based most of the 

CSLs for medical EPSs on the International Efficiency Marking Protocol for External Power 

Supplies that applies to Class A 18W EPSs (Table 3.23). The lowest level, “Less than the II 

mark” is based on the efficiency of a line­frequency Class A EPS with a nameplate output power 

of 14.4 watts and nameplate output voltage of 12 volts. DOE scaled the efficiency of the unit to 

determine that its expected efficiency, if it were to be an 18­watt EPS is 66.0 percent, hence the 

conversion efficiency of CSL 0. The maximum no­load power for CSL 0 is the same as for 

CSL 1, the mark II level. Candidate standard level 0 has a maximum no­load power of 1 watt, 

which is the same level as CSL 1, because EPS #130 consumed 0.56 watts of no­load power. 

To develop the requirements for CSL1 and CSL2, DOE observed that there was no clear 

relationship for the switched­mode EPSs with average active­mode efficiency and the no­load 

power requirements between mark II (70% efficient and 1­watt no­load power consumption) and 

mark IV (76% efficient and 0.5­watts no­load power consumption) for an 18­watt EPS according 

to the International Efficiency Marking Protocol for External Power Supplies. DOE was 

confident that EPSs already available on the market could meet a standard set at the mark IV 

requirements because some tested units demonstrated this fact. DOE thus chose to use these 

requirements for CSL2. A manufacturer stated that it is possible to meet this CSL with a switchmode EPS using a flyback topology and a specific PWM IC as well as a Schottky diode on the 

EPS’s output rectifier. 

The same manufacturer discussed ways to produce a medical device EPS with an average 

active­mode efficiency of 85% and a maximum no­load power of 0.15 watts. DOE used these 

characteristics as the requirements for CSL3 for medical device EPSs. These requirements can be 

met through the usage of a quasi­resonant PWM circuit, a primary field­effect transistor (FET) 

and secondary synchronous circuit with low voltage drops, wiring with an increased gauge, and a 

planar transformer. Table 3.23 details the minimum active­mode efficiency and maximum noload power requirements for all CSLs for medical device EPSs. 

Table 3.23 Candidate Standard Levels for an 18­Watt Medical Device EPS for a 

Nebulizer 

Level Reference Minimum 

Efficiency [%] 

Maximum 

No­Load Power [W] 

Basis 

0 Less than the II mark 66.0 1.00 

Scaled tested unit 

(#130), Marking 

protocol 

1 Meets the II mark 69.9 1.00 Marking protocol 

2 Meets the IV mark 76.0 0.50 Marking protocol 

3 Higher level 85.0 0.15 Manufacturer interview 

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3.7.1.4 Candidate Standard Levels for EPSs for BCs

DOE developed candidate standard levels for the 1.8­watt and 4.8­watt representative 

units for EPSs for BCs based on data from laboratory testing of Class A EPSs. DOE based 

CSL 0 on the scaled efficiency test results of the least efficient tested unit, EPS #17, which is a 

line­frequency EPS. The higher CSLs are based on the international efficiency marking levels for 

a Class A 1.8W EPS and a Class A 4.8W EPS, shown in Table 3.24 and Table 3.25, respectively. 

DOE chose to use the marking levels because DOE observed that there were EPSs available on 

the market that could already meet the average active­mode efficiency and no­load power 

requirements of the levels. 

Table 3.24 Candidate Standard Levels for a 1.8­Watt EPS for BC for a Vacuum 

Level Reference Minimum 

Efficiency [%] 

Maximum 

No­Load Power [W] 

Basis 

0 Less than the II mark 24.3 1.85 Scaled tested unit (#17) 

1 Meets the II mark 45.3 0.75 Marking protocol 

2 Meets the IV mark 55.3 0.50 Marking protocol 

3 Meets the V mark 65.9 0.30 Marking protocol 

Table 3.25 Candidate Standard Levels for a 4.8­Watt EPS for a Do­It­Yourself Power 

Tool 

Level Reference Minimum 

Efficiency [%] 

Maximum 

No­Load Power [W] 

Basis 

0 Less than the II mark 37.6 1.85 Scaled tested unit (#17) 

1 Meets the II mark 55.8 0.75 Marking protocol 

2 Meets the IV mark 64.1 0.50 Marking protocol 

3 Meets the V mark 72.0 0.30 Marking protocol 

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CHAPTER 4 ENERGY USE AND END­USE LOAD CHARACTERIZATION
­

4.1 Introduction 

This chapter provides an example walkthrough of the methodology DOE used in its 

determination analysis to calculate the annual unit energy consumption (UEC) of an external 

power supply (EPS). The methodology is implemented in a Microsoft® Excel workbook that can 

be downloaded from the EERE web site.a 

Section 4.2 provides a walkthrough of unit energy consumption for the multiple voltage 

EPS used to power an Xbox 360. 

Section 4.3 provides inputs and calculated unit energy consumption values for all 

remaining EPSs. 

Section 4.4 provides the methodology for calculating EPS power consumption for all 

modes of operation. 

4.2 Walkthrough of Unit Energy Consumption Calculation 

This section presents the inputs and calculations in the same order as they appear in the 

NOPR. In the following sub­sections, DOE discusses the following inputs: 

4.2.1 Usage Profile for Multiple­Voltage EPS (203W, Xbox 360) 

4.2.2 EPS Power Consumption by Modes of Operation 

4.2.3 Active Mode Efficiency and No Load Mode Power Consumption 

4.2.4 Calculating Unit Energy Consumption 

a Available for download from the EERE website: 

http://www.eere.energy.gov/buildings/appliance_standards/residential/battery_external.html 

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4.2.1 Usage Profile for Multiple­Voltage EPS (203W, Xbox 360) 

In the NOPR, DOE defined two usage profiles for the Xbox 360, one for a light user and one 

for a heavy user. These usage profiles were combined to create a weighted­average usage 

profile as shown in Table 4.1 

Table 4.1 Weighted­Average Usage and Output Power of EPS for Xbox 360 

EPS Mode Application 

State 

Annual Usage (hours/year) EPS 

Output 

Power* 

[W] 

Light User 

[80%] 

Heavy User 

[20%] 

WeightedAverage 

User 

Active Playing Video 

Game 

500 2,100 820 

102.62 

Idle Video 

Game 

560 560 560 

101.50 

Playing DVD 90 90 90 95.02 

Idle DVD 150 150 150 95.02 

Idle – No Disc 150 150 150 86.38 

Off 7,310 5,710 6,990 2.35 

No Load Disconnected 

from EPS 

0 0 0 0 

Unplugged — 0 0 0 0 

* Output power levels for all application states were derived from input power 

measurements reported in NRDC, "Lowering the Cost of Play: Improving the Energy 

Efficiency of Video Game Consoles," November 2008 using DOE’s measurements of 

the efficiency and no­load power consumption of the EPS that ships with the Xbox 360. 

Video game application state usage estimates: Nielsen Wireless and Interactive 

Services, "The State of the Console ­ Video Game Console Usage ­ Fourth Quarter 

2006," 2007. 

DVD Usage Estimates: TIAX, "Energy Consumption by Consumer Electronics in U.S. 

Residences," Final Report to the Consumer Electronics Association, January 2007. 

(Adjusted to 33% of use per “Lowering the Cost of Play,” cited above.) 

4.2.2 EPS Power Consumption by Modes of Operation 

In the NOPR, DOE described the following loads for each application state. In addition, 

DOE calculated the load as a percentage of nameplate output power, to be used in the next 

section to determine the equation used for calculating energy consumption. Table 4.2 shows an 

example of load by application state for the EPS for the Xbox 360. 

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Table 4.2 Load by Application State for EPS for Xbox 360
­

EPS Mode Application State EPS Output Power 

[W] 

Percentage of 

Nameplate Output 

Power [%] 

Active Playing Video Game 102.62 51 

Idle Video Game 101.50 50 

Playing DVD 95.02 47 

Idle DVD 95.02 47 

Idle – No Disc 86.38 43 

Off 2.35 1 

No Load Disconnected from 

EPS 

0 ­

Unplugged — 0 ­

4.2.3 Active Mode Efficiency and No Load Mode Power Consumption 

Table 4.3 shows the minimum active mode efficiency and the maximum no load mode 

power consumption for each CSL. 

Table 4.3 Candidate Standard Levels for an EPS for Xbox 360 

CSL Minimum Active Mode 

Efficiency [%] 

Maximum 

No­Load Power [W] 

0 82.4 12.33 

1 86.4 0.40 

2 86.4 0.30 

3 88.5 0.30 

4.2.4 Calculating Unit Energy Consumption 

Using the above inputs, DOE calculated UEC as the sum of energy consumption in all 

EPS modes: 

ECon = PCON­Active1 * TActive1 + Eq. 6.1 

PCON­Active2 * TActive2 + 

PCON­Active3 * TActive3 + 

PCON­Active4 * TActive4 + 

PCON­Active5 * TActive5 + 

PCON­Active6 * TActive6 + 

PCON­No­Load * TNo­Load 

For all the active application states, PCon is a function of POut. The function selected 

depends on the load of the application state. For each application state with a load greater or 

equal to 25 percent of nameplate output power, PCon was calculated using the following equation: 

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PCon = POut x (1/η – 1) Eq. 6.2 

For each application state with a load less than 25 percent of nameplate output power, 

PCon was calculated using the following equation: 

PCon = ({[(25% x [PNameplate / η]) – PNL] / [25% x PNameplate]}­1) x POut + PNL Eq. 6.3 

For no load mode, PCon is simply PNL: 

PCon = PNL Eq. 6.4 

Table 4.4 indicates which equation was used to calculate energy consumption in each 

application state and each EPS mode. 

Table 4.4 Equations Used to Calculate Energy Consumption in Each Application State 

EPS Mode Application State EPS Output 

Power* [W] 

Percentage of Nameplate 

Output Power [203 W] 

Equation 

Used 

Active Playing Video Game 102.62 51 6.2 

Idle Video Game 101.50 50 6.2 

Playing DVD 95.02 47 6.2 

Idle DVD 95.02 47 6.2 

Idle – No Disc 86.38 43 6.2 

Off 2.35 1 6.3 

No Load Disconnected from 

EPS 

0 ­ 6.4 

Unplugged — 0 ­ ­

* The values in this table are the results of the calculations described above and so, due to rounding errors, may not 

exactly match the values actually used in the determination analysis. 

PCon and UEC are calculated for each application state and each EPS mode in the 

following seven tables. 

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Table 4.5 UEC for Active – Playing Video Game (EPS Output Power = 102.62 W)
­

CSL Minimum 

Active Mode 

Efficiency 

[%] 

PCon­Active1 

[W] 

(Equation 6.2) 

Weighted 

Average Usage 

[hours/year] 

Unit Energy 

Consumption 

[kWh/year] 

0 82.4 102.62 x [(1/0.824)­1] = 

21.92 

820 17.97 

1 86.4 102.62 x [(1/0.864)­1] = 

16.15 

820 13.24 

2 86.4 102.62 x [(1/0.864)­1] = 

16.15 

820 13.24 

3 88.5 102.62 x [(1/0.885)­1] = 

13.33 

820 10.93 

Table 4.6 UEC for Active – Idle Video Game (EPS Output Power = 101.50 W)
­

CSL Minimum 

Active Mode 

Efficiency 

[%] 

PCon­Active1 

[W] 

(Equation 6.2) 

Weighted 

Average Usage 

[hours/year] 

Unit Energy 

Consumption 

[kWh/year] 

0 82.4 101.50 x [(1/0.824)­1] = 

21.68 

560 12.14 

1 86.4 101.50 x [(1/0.864)­1] = 

15.97 

560 8.94 

2 86.4 101.50 x [(1/0.864)­1] = 

15.97 

560 8.94 

3 88.5 101.50 x [(1/0.885)­1] = 

13.18 

560 7.73 

Table 4.7 UEC for Active – Playing DVD (EPS Output Power = 95.02 W)
­

Level Minimum 

Active Mode 

Efficiency 

[%] 

PCon­Active1 

[W] 

(Equation 6.2) 

Weighted 

Average Usage 

[hours/year] 

Unit Energy 

Consumption 

[kWh/year] 

0 82.4 95.02 x [(1/0.824)­1] = 

20.29 

90 1.83 

1 86.4 95.02 x [(1/0.864)­1] = 

14.95 

90 1.35 

2 86.4 95.02 x [(1/0.864)­1] = 

14.95 

90 1.35 

3 88.5 95.02 x [(1/0.885)­1] = 

12.35 

90 1.11 

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Table 4.8 UEC for Active – Idle DVD (EPS Output Power = 95.02 W)
­

CSL Minimum 

Active Mode 

Efficiency 

[%] 

PCon­Active1 

[W] 

(Equation 6.2) 

Weighted 

Average Usage 

[hours/year] 

Unit Energy 

Consumption 

[kWh/year] 

0 82.4 95.02 x [(1/0.824)­1] = 

20.29 

150 3.04 

1 86.4 95.02 x [(1/0.864)­1] = 

14.95 

150 2.24 

2 86.4 95.02 x [(1/0.864)­1] = 

14.95 

150 2.24 

3 88.5 95.02 x [(1/0.885)­1] = 

12.35 

150 1.85 

Table 4.9 UEC for Active – Idle No­Disc (EPS Output Power = 86.38 W)
­

CSL Minimum 

Active Mode 

Efficiency 

[%] 

PCon­Active1 

[W] 

(Equation 6.2) 

Weighted 

Average Usage 

[hours/year] 

Unit Energy 

Consumption 

[kWh/year] 

0 82.4 86.38 x [(1/0.824)­1] = 

18.45 

150 2.77 

1 86.4 86.38 x [(1/0.864)­1] = 

13.60 

150 2.04 

2 86.4 86.38 x [(1/0.864)­1] = 

13.60 

150 2.04 

3 88.5 86.38 x [(1/0.885)­1] = 

11.22 

150 1.68 

Table 4.10 UEC for Active – Off (EPS Output Power = 2.35 W)
­

CSL Minimum 

Active Mode 

Efficiency 

[%] 

PNL 

[W] 

PCon­Active1 

[W] 

(Equation 6.3) 

0 82.4 12.33 ({[0.25 x [203/0.824])­12.33]/[0.25 x 203]}­1) x 2.35 + 

12.33 = 12.26 

1 86.4 0.40 ({[0.25 x [203/0.864])­0.4]/[0.25 x 203]}­1) x 2.35 + 0.4 = 

0.75 

2 86.4 0.30 ({[0.25 x [203/0.864])­0.3]/[0.25 x 203]}­1) x 2.35 + 0.3 = 

0.66 

3 88.5 0.30 ({[0.25 x [203/0.885])­0.3]/[0.25 x 203]}­1) x 2.35 + 0.3 = 

0.59 

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Table 4.11 UEC for Active ­ Continued
­

CSL PCon­Active1 

[W] 

Weighted 

Average Usage 

[hours/year] 

Unit Energy 

Consumption 

[kWh/year] 

0 12.26 6,990 85.70 

1 0.75 6,990 5.24 

2 0.66 6,990 4.61 

3 0.59 6,990 4.12 

Table 4.12 UEC for No Load Mode
­

CSL PNL 

(W) 

PCon­NoLoad 

[W] 

(Equation 6.4) 

Weighted Average 

Usage [hours/year] 

Unit Energy 

Consumption 

[kWh/year] 

0 12.33 12.33 0 0 

1 0.40 0.40 0 0 

2 0.30 0.30 0 0 

3 0.30 0.30 0 0 

The UECs calculated in the preceding tables are summarized in Table 4.13.
­

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Table 4.13 UEC by Application State at Each Candidate Standard Level
­

EPS Mode Application 

State 

UEC (kWh/year)* 

CSL 0 CSL 1 CSL 2 CSL 3 

Active Playing Video 

Game 17.9 13.3 13.3 10.9 

Idle Video 

Game 12.1 9.0 9.0 7.4 

Playing DVD 1.8 1.3 1.3 1.1 

Idle DVD 3.0 2.2 2.2 1.8 

Idle – No Disc 2.8 2.0 2.0 1.7 

Off 88.3 4.6 4.0 3.7 

No Load Disconnected 

from EPS 0 0 0 0 

Unplugged — 0 0 0 0 

Total UEC: 126.01 32.44 31.85 26.57 

* The values in this table are the results of the calculations described above and so, due to rounding errors, may not 

exactly match the values actually used in the determination analysis. 

Inputs and calculated UEC values for other EPSs are listed in the following sections. For 

the specific calculations please refer to the UEC workbook. 

4.3 Unit Energy Consumption Values for Non­Class A External Power Supplies 

The following tables show, for each type of non­Class A EPS, the candidate standard 

levels, usage profiles and unit energy consumption values calculated at each candidate standard 

level in each application state. 

4.3.1 Multiple­Voltage EPS for Multifunction Devices 

Table 4.14 Candidate Standard Levels for 40 W Multiple­Voltage EPS for Multifunction 

Devices 

CSL Reference point for level Minimum Efficiency 

[%] 

Maximum No­Load Power 

[W] 

0 Current level 80 0.6 

1 EISA level 83 0.5 

2 Greater than EISA 85 0.4 

3 Higher level 89 0.3 

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Table 4.15 Usage and Output Power of EPS for 40 W Multiple­Voltage EPS for 

Multifunction Devices 

EPS 

Mode 

Application State Annual Usage 

[hours/year] 

EPS Output Power 

[W] 

Active Printing, 

Photocopying, 

Faxing, Scanning 

52 32* 

Idle 1,606 9.1 

Off 7,102 6.2 

No Load Disconnected from 

EPS 

0 0 

Unplugged Disconnected from 

EPS 

0 0 

* DOE estimated EPS output power for printing, photocopying, faxing, and scanning to 

be 80 percent of nameplate output power. 

Table 4.16 Unit Energy Consumption for 40 W Multiple­Voltage EPS for Multifunction 

Devices 

CSL Unit Energy Consumption (kWh/year) 

EPS Active Mode (Application State) EPS NoLoad Mode Total 

Printing, Copying, 

Faxing, Scanning 

Idle Off 

0 0.40 3.55 11.81 ­ 15.75 

1 0.27 2.47 8.47 ­ 11.22 

2 0.19 1.69 5.79 ­ 7.66 

3 0.17 1.49 4.95 ­ 6.61 

4.3.2 High­Power EPS for Amateur Radio Equipment 

Table 4.17 Candidate Standard Levels for 345 W High­Power EPS for Amateur Radio 

Equipment 

CSL Reference point for level Minimum Efficiency 

[%] 

Maximum No­Load Power 

[W] 

0 Line Frequency 50 16 

1 Switched­mode – Low Level 81 6 

2 Switched­mode – Mid Level 84 2 

3 Switched­mode – High Level 87 1.5 

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Table 4.18 Light Usage of 345 W High­Power EPS for Amateur Radio Equipment
­

EPS 

Mode 

Application 

State 

Annual 

Usage 

(hours/year) 

Reasoning 

Active Transmitting 10 Radio setup is used roughly 2 hours a 

week, during which time the equipment 

is transmitting for 10 percent of the time, 

receiving for 10 percent of the time, and 

idle for the remaining time. 

Receiving 10 

Idle 80 

No Load Disconnected 

from EPS 

0 The EPS is never disconnected from the 

load but left connected to mains. 

Off or 

Unplugged 

— 8,660 The EPS is either turned off or 

unplugged and stored when not in use. 

Table 4.19 Medium Usage of 345 W High­Power EPS for Amateur Radio Equipment
­

EPS 

Mode 

Application 

State 

Annual 

Usage 

(hours/year) 

Reasoning 

Active Transmitting 100 Radio setup is used roughly 20 hours a 

week, during which time the equipment 

is transmitting for 10 percent of the 

time, receiving for 10 percent of the 

time, and idle for the remaining time. 

Receiving 100 

Idle 1,600 Assumes that roughly 90 percent of 

medium users turn the EPS off when 

not in use and that the remaining 

10 percent leave it on. 

No Load Disconnected 

from EPS 

0 The EPS is never disconnected from 

the load but left connected to mains. 

Off or 

Unplugged 

— 6,960 The EPS is turned off when not in use, 

but is never unplugged. 

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Table 4.20 Heavy Usage of 345 W High­Power EPS for Amateur Radio Equipment
­

EPS 

Mode 

Application 

State 

Annual 

Usage 

(hours/year) 

Reasoning 

Active Transmitting 438 Radio setup is always on, during which 

the equipment is transmitting for 

5 percent of the time, receiving for 

5 percent of the time, and idle for the 

remaining time. 

Receiving 438 

Idle 7,884 

No Load Disconnected 

from EPS 

0 The EPS is never disconnected from the 

load but left connected to mains. 

Off or 

Unplugged 

— 0 The EPS is never turned off or 

unplugged. 

Table 4.21 Weighted­Average Usage and Output Power of 345 W High­Power EPS for 

Amateur Radio Equipment 

EPS Mode Application 

State 

Annual Usage (hours/year) EPS 

Output 

Power 

[W]* 

Light 

User 

(50%) 

Medium 

User 

(25%) 

Heavy 

User 

(25%) 

Weighte 

dAverage 

User 

Active Transmitting 10 100 438 140 276 

Receiving 10 100 438 140 69 

Idle 80 1,600 7,884 2,411 69 

No Load Disconnected 

from EPS 

0 0 0 0 0 

Off or 

Unplugged 

— 8,660 6,960 0 6,070 0 

* DOE estimated output power levels at 80 percent of nameplate for transmitting and at 

20 percent of nameplate for receiving or idle. 

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Table 4.22 Unit Energy Consumption for 345 W High­Power EPS for Amateur Radio 

Equipment 

CSL Unit Energy Consumption (kWh/year) 

EPS Active Mode (Application State) EPS NoLoad Mode Total 

Transmitting Receiving Idle 

0 23.23 6.24 107.82 ­ 137.29 

1 8.84 2.38 41.08 ­ 52.30 

2 7.61 1.94 33.60 ­ 43.15 

3 6.79 1.71 29.60 ­ 38.11 

4.3.3 EPS for Medical Devices 

Table 4.23 Candidate Standard Levels for 18 W EPS for Medical Devices 

CSL Reference point for level Minimum Efficiency 

[%] 

Maximum No­Load Power 

[W] 

0 Less than the II mark 66 2 

1 Meets the II mark 70 1 

2 Meets the IV mark 76 0.5 

3 Meets the V mark 80 0.3 

Table 4.24 Medium Usage of 18 W EPS for Medical Devices
­

EPS 

Mode 

Application 

State 

Annual 

Usage 

(hours/year) 

Reasoning 

Active On 121.7 The medical device is used twice daily. 

Off 8,638.3 The medical device is turned off when 

not in use. 

No Load Disconnected 

from EPS 

0 The EPS is never disconnected from the 

load. 

Unplugged — 0 The EPS is never disconnected from 

mains. 

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Table 4.25 Heavy Usage of 18 W EPS for Medical Devices
­

EPS 

Mode 

Application 

State 

Annual 

Usage 

(hours/year) 

Reasoning 

Active On 182.5 The medical device is used three times 

daily. 

Off 8,577.5 The medical device is turned off when 

not in use. 

No Load Disconnected 

from EPS 

0 The EPS is never disconnected from the 

load. 

Unplugged — 0 The EPS is never disconnected from 

mains. 

Table 4.26 Weighted­Average Usage and Output Power of 18 W EPS for Medical Devices
­

EPS 

Mode 

Application 

State 

Annual Usage (hours/year) EPS 

Output 

Power 

[W]* 

Light 

User 

(33%) 

Medium 

User 

(34%) 

Heavy 

User 

(33%) 

WeightedAverage 

User 

Active On 60.8 121.7 182.5 121.7 14.4 

Off 8,699.2 8,638.3 8,577.5 8,638.3 0.9 

No Load Disconnected 

from EPS 

0 0 0 0 0 

Unplugged — 0 0 0 0 0 

* DOE estimated output power levels at 80 percent of nameplate when the application is 

on, and at 20 percent of nameplate when the application is off. 

Table 4.27 Unit Energy Consumption for 18 W EPS for Medical Devices
­

CSL Unit Energy Consumption (kWh/year) 

EPS Active Mode (Application State) EPS No­Load 

Mode 

Total 

On Off 

0 0.90 7.20 ­ 8.11 

1 0.55 5.42 ­ 5.97 

2 0.43 3.65 ­ 4.08 

3 0.31 2.21 ­ 2.52 

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4.3.4 EPS for Battery Chargers for Floor Care Appliances 

Table 4.28 Candidate Standard Levels for 1.8 W EPS for Floor Care Appliances 

CSL Reference point for level Minimum Efficiency 

[%] 

Maximum No­Load Power 

[W] 

0 Less than the II mark 30 1.5 

1 Meets the II mark 45 0.75 

2 Meets the IV mark 55 0.5 

3 Meets the V mark 66 0.3 

Table 4.29 Usage and Output Power of 1.8 W EPS for Floor Care Appliances
­

EPS 

Mode 

Application 

State 

Annual 

Usage 

(hours/year) 

Reasoning EPS 

Output 

Power 

(W) 

Active Active 

Charging 

416 The battery undergoes one 

24 hour charging cycle a 

week. During this charging 

cycle, the battery is in an 

active charging state for 8 

hours. 

1.44 

Maintenance 8,292 When the vacuum is not in 

an active charging state or 

in use, the vacuum is left 

in the cradle and/or 

attached to the EPS. 

0.63 

No Load Disconnected 

from 

EPS/Cradle 

52 The vacuum is used for a 

total of 1 hour per week. 

While in use, the vacuum 

(and integrated battery) are 

disconnected from the 

cradle/EPS. 

0 

Unplugged — 0 The EPS is never 

disconnected from mains. 

0 

Table 4.30 Unit Energy Consumption for 1.8 W EPS for Floor Care Appliances
­

CSL Unit Energy Consumption (kWh/year) 

EPS Active Mode (Application State) EPS NoLoad Mode Total 

Active Charging Maintenance No­Battery 

0 1.87 16.23 0.10 ­ 18.20 

1 0.73 6.31 0.04 ­ 7.08 

2 0.49 4.22 0.03 ­ 4.74 

3 0.31 2.71 0.02 ­ 3.03 

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4.3.5 EPS for Battery Chargers for Power Tools 

Table 4.31 Candidate Standard Levels for 4.8 W EPS for Power Tools 

CSL Reference point for level Minimum Efficiency 

[%] 

Maximum No­Load Power 

[W] 

0 Less than the II mark 30 3 

1 Meets the II mark 56 0.75 

2 Meets the IV mark 64 0.5 

3 Meets the V mark 72 0.3 

Table 4.32 Light Usage of 4.8 W EPS for Power Tools
­

EPS 

Mode 

Application 

State 

Annual 

Usage 

(hours/year) 

Reasoning 

Active Active 

Charging 

36 The battery is charged once a month and 

takes 3 hours to fully charge. 

Maintenance 252 Each time the battery is charged, it is left 

in the charger for 21 hours after being 

fully charged. 

No­Battery 0 The battery charger and EPS are 

unplugged and stowed when not in use. 

No Load Disconnected 

from EPS 

0 The battery charger and EPS are 

unplugged and stowed when not in use. 

Unplugged — 8,472 The battery charger and EPS are 

unplugged and stowed when not in use. 

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Table 4.33 Heavy Usage of 4.8W EPS for Power Tools
­

EPS 

Mode 

Application 

State 

Annual 

Usage 

(hours/year) 

Reasoning 

Active Active 

Charging 

312 The battery is charged twice a week and 

takes 3 hours to fully charge. 

Maintenance 7,616 For each charge cycle, the battery is left 

in the charger for 22 hours (total 66 

hours). In addition, the battery is left in 

the charger in general, except when in 

use. (An additional time of 24 hours a 

year is added to this time as a correcting 

factor.) 

No­Battery 416 The power tool is used twice a week, for 

8 hours each time. Fifty percent of power 

tools come with cradle chargers. Thus 

half the time is allocated to the no­battery 

state. The remaining half is allocated to 

no­load mode. 

No Load Disconnected 

from EPS 

416 (see reasoning above) 

Unplugged — 0 The battery charger and EPS are never 

disconnected from mains. 

Table 4.34 Weighted­Average Usage and Output Power of 4.8 W EPS for Power Tools
­

EPS Application Annual Usage (hours/year) EPS 

Output 

Power 

[W] 

Mode State Light User 

(75%) 

Heavy User 

(25%) 

WeightedAverage 

User 

Active Active 

Charging 

36 312 105 3.84 

Maintenance 252 7,616 2,093 1.68 

No­Battery 0 416 104 1 

No Load Disconnected 

from EPS 

0 416 104 0 

Unplugged — 8,472 0 6,354 0 

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Table 4.35 Unit Energy Consumption for 4.8 W EPS for Power Tools
­

CSL Unit Energy Consumption (kWh/year) 

EPS Active Mode (Application State) EPS NoLoad Mode Total 

Active Charging Maintenance No­Battery 

0 0.67 5.83 0.20 0.19 6.90 

1 0.32 2.79 0.10 0.08 3.28 

2 0.23 1.97 0.07 0.05 2.31 

3 0.16 1.37 0.05 0.03 1.60 

4.4 EPS Power Consumption by Modes of Operation 

In the NOPR, DOE defined power consumption as a function of three factors: the 

nameplate output power of the EPS, the efficiency of the EPS, and the consumption of the EPS 

when in no load mode. 

Note: When discussing power consumption, DOE is referring to the power loss 

associated with the use of the EPS. That is, the power “consumed” by the EPS is the difference 

between input and output power. 

No­load mode power (PNL) is the measured power drawn by the EPS from mains while in 

no­load mode. Because the EPS is disconnected from the application, all of the power drawn 

from mains is consumed by the EPS. For each candidate standard level, an associated no­load 

mode power is given. No­load mode power levels for each of the representative units are 

discussed in the engineering analysis section of this notice. 

EPS power consumption while in active mode varies as the power requirements of its 

load vary. Nameplate output power is the highest output power that an EPS is capable of 

delivering. In the case of high power EPSs used for amateur radio equipment, nameplate output 

power is also described as instantaneous, intermittent, peak or surge power. Nameplate output 

power is the product of nameplate output voltage and nameplate output current, which are 

defined in the EPS test procedure. Nameplate output voltage is the voltage output of the EPS as 

specified by the manufacturer on the label on the housing of the EPS. (10 CFR 430, Appendix Z) 

Nameplate output current is the current output of the EPS as specified by the manufacturer on the 

label on the housing of the EPS. (10 CFR 430, Appendix Z) 

DOE used two different approaches to calculating EPS power consumption in active 

mode—one for those application states requiring 25 percent or more of the EPS’s nameplate 

output power and another for those application states requiring less than 25 percent of the EPS’s 

nameplate output power. 

The approach for application states requiring 25 percent or more of the EPS’s nameplate 

output power is straightforward. The EPS test procedure measures the active mode efficiency (η) 

of the EPS at 25, 50, 75, and 100 percent of nameplate output power or current. The active mode 

efficiency of the EPS is then defined as the average of these 4 values (points 2, 3, 4, and 5 in 

Figure 4.1) As such, power consumption is 

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PCon = PIn – POut 

where 

POut = PIn x η 

or 

PIn = POut x (1/η) 

Therefore, 

PCon = POut x (1/η – 1) 

For example, an EPS delivering an output power of 10 watts at 75 percent efficiency 

would consume: 

PCon = 10 W x (1/0.75 – 1) = 3.33 W 

Active mode efficiency (η) levels for each of the representative units are discussed in the 

engineering analysis section of this notice. 

The approach for application states requiring less than 25 percent of the EPS’s nameplate 

output power blends measures of the EPS’s active­mode efficiency and no­load mode power 

consumption. Most applications have some application states that require an output power below 

25 percent of nameplate. Additionally, many applications spend a significant portion of time in 

these states. However, at these low power levels the efficiency of an EPS is relatively low (see 

Figure 4.1.). Because of this, DOE did not use the active­mode efficiency metric alone. 

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5

Input Power

X

4

X

3

X

2

X

X

0% 25% 50% 75% 100%

Output Power (Percent of Nameplate)

Figure 4.1 Relationship Between EPS Input Power and Output Power at Five Loading 

Points as Measured by the Test Procedure 

Instead, DOE calculated energy consumption in this region by interpolating between 

two known points: (1) the no load power consumption and (2) the active mode consumption at 

25 percent of nameplate output power. These are points 1 and 2 in Figure 4.1. At an output 

power of 25 percent, the energy consumed by the EPS is: PConsumed = POut x (1/η – 1). At an 

output power of 0 percent (no load mode), the energy consumed by the EPS is: PConsumed = PNL. 

Given these two known values, DOE assumed that the energy consumed by an EPS at an 

output power between 0 and 25 percent of nameplate output power must fall on a curve 

between these two points. 

DOE approximated this curve with a straight line between points 1 and 2, which can be 

described by the following equation relating input power to output power: 

PIn = m x POut + B 

Where B is the y­axis intercept, or PNL, and m is the slope, or: 

m = ∆y/∆x 

m = [(25% x [PNameplate / η]) – PNL] / [(25% x PNameplate) – 0] 

Thus, for output power levels below 25 percent nameplate output power, the input power of the 

EPS is: 

1

(0W, PNL)

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PIn = {[(25% x [PNameplate / η]) – PNL] / [25% x PNameplate]} x POut + PNL 

Since 

PConsumed = PIn – POut 

Then 

PConsumed = {[(25% x [PNameplate / η]) – PNL] / [25% x PNameplate]} x POut + PNL – POut 

Or 

PConsumed = ({[(25% x [PNameplate / η]) – PNL] / [25% x PNameplate]}­1) x POut + PNL 

DOE seeks comment on its methodology for calculating energy consumption at output 

power levels below 25 percent of nameplate output power. 

4.4.1 EPS Energy Use 

4.4.1.1 EPS Energy Consumption

Unlike most other consumer products using electricity, the energy consumption of an 

EPS cannot always be measured as the energy drawn from mains, since the function of an EPS is 

to deliver power for the operation of other end­use applications. DOE calculated the energy 

consumption of an EPS (ECON) as the difference between energy drawn from mains (EIN) and the 

energy supplied to the end­use application (EOUT), or: 

ECON = EIN ­ EOUT 

Since energy measures power (P) multiplied by a duration of time (T), the following 

equation is used: 

PCON * T = (PIN – POUT) * T 

Factoring in the different EPS modes we get: 

PCON * TTOTAL =	­ PCON­Active * TActive +
­

PCON­No­Load * TNo­Load
­

Further factoring in application states, we get: 

PCON * TTOTAL =	­ PCON­Active1 * TActive1 +
­

PCON­Active2 * TActive2 +
­

PCON­Active3 * TActive3 +
­

... 

PCON­No­Load * TNo­Load 

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Thus, to calculate the energy consumption of an EPS, DOE then combined the time and power 

consumption values (from shown in the usage profiles) with power consumption values. 

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CHAPTER 5 LIFE­CYCLE COST AND PAYBACK PERIOD ANALYSIS 

5.1 Life­Cycle Cost and Payback Period Analysis 

5.1.1 Introduction 

This chapter of Technical Support Document (TSD) contains information that supports 

and expands on the Life­Cycle Cost and Payback Period Analysis section of the Notice of 

Proposed Rulemaking (NOPR). Specifically, this section describes the methodology that the 

Department of Energy (DOE) used to analyze the economic impacts of possible energy 

efficiency standards on individual consumers. DOE performed this analysis on the same 

representative units evaluated in the engineering analysis section of the NOPR. The effects of 

standards on individual consumers include a change in operating expenses (usually decreased) 

and a change in purchase price (usually increased). This section describes the two metrics DOE 

used in the consumer analysis to determine the effect of potential standards on individual 

consumers: 

• Life­cycle cost (LCC) is the total consumer expense over the lifetime of an appliance, 

including the up­front cost (the total price paid by a consumer before the appliance can be 

operated) and all operating costs (including energy expenditures). DOE discounts future 

operating costs to the time of purchase. 

• Payback period (PBP) represents the number of years it would take the customer to 

recover the assumed higher purchase price of more energy­efficient equipment through 

decreased operating expenses.a Sometimes more energy­efficient equipment can have a 

lower purchase price than the less energy­efficient equipment that it substitutes for; in 

this case, the consumer realizes an immediate financial benefit and thus there is no 

payback period. 

a DOE computes a “simple PBP,” where only the first year of operating costs are used. Thus, operating costs are not 

discounted. See section 5.1.4.1 for further information. 

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EPSs are unique appliances because they are always used in conjunction with other 

products of interest, as shown in Figure 5.1. Most EPSs are packaged with particular products; 

thus, consumers usually do not buy EPSs directly. Instead, for example, consumers obtain EPSs 

for video game systems when buying the video game systems themselves. Thus, although the 

LCC and PBP analysis uses the consumer purchase prices of EPSs, in reality those prices are a 

“hidden” portion of the prices that consumers pay for the products of interest. 

Figure 5.1 Usage of External Power Supplies 

Because EPSs are used in conjunction with other products, their energy consumption is 

directly related to the usage of those other products as well as the technologies that the EPSs 

utilize. The energy consumption of the analyzed Non­Class A EPSs is assessed in further detail 

in the energy use and end­use load characterization section of the NOPR. The technologies of the 

analyzed Non­Class A EPSs are assessed further in the technology assessment section of the 

NOPR. 

5.1.2 Overview of LCC and PBP Inputs 

For the Non­Class A EPS determination analysis, DOE categorized inputs to the LCC 

and PBP analysis as follows: (1) inputs for establishing the consumer purchase price of an EPS, 

and (2) inputs for calculating the operating cost. In this analysis, all dollar amounts are in 2008 

dollars. 

The primary inputs for establishing the consumer purchase price are: 

•	 efficiency­related materials cost (ERMC) in 2008 dollars, which is based on the 

bill of materials cost of the efficiency­related components of the EPS; and 

markups as scaling factors applied to the manufacturer production cost to create the final 

efficiency­related consumer purchase price. The primary inputs for calculating the operating cost 

are: 

•	 unit energy consumption in kilowatt­hours per year (kWh/year), which is the 

annual site energy use of the EPS; 

•	 electricity prices in 2008 dollars, which are the prices paid by consumers for 

electricity; 

•	 an electricity price trend, which is applied to the 2008 electricity price to forecast 

electricity prices into the future; 

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•	 start year, which is the year in which the EPS and its associated product are 

purchased (for the LCC and PBP analysis, DOE uses 2013 as the start year for all 

products); 

•	 lifetime, which is the age at which the EPS and its associated product are retired 

from service (lifetimes vary by product); and 

•	 discount rate, which is the rate at which DOE discounted future expenditures to 

establish their values in the start year. Note that future expenditures are 

discounted for the LCC calculation and not the PBP calculation, as DOE uses a 

simple PBP. See section 5.1.4 for further information. 

Figure 5.2 presents the flow diagram for the draft determination analysis LCC developed 

by DOE. The figure depicts LCC inputs in yellow boxes, interim calculated values in green 

boxes, and final output values (i.e., LCC and PBP results) in aqua boxes. Table 5.1 lists the draft 

inputs DOE developed for the determination analysis. 

Figure 5.2 Flow Diagram of Inputs for the Determination of LCC and PBP 

EfficiencyRelated

Materials Cost

Markups

EfficiencyRelated

Consumer

Purchase

Price

Unit Energy

Consumption

Electricity Prices

Annual

Energy Cost

Lifetime

Discount

Rate

Electricity

Price Trend

Lifetime

Operating

Expense

Payback

Period

Life­Cycle

Cost

Start Year

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Table 5.1 Draft Inputs to the Life­Cycle Cost and Payback Period Analysis
­

Input Description Average or 

Typical 

Value 

Sources 

EfficiencyRelated 

Materials Cost 

The bill of materials cost, in 

2008 dollars, of the 

efficiency­related components 

of the EPS. 

$2.95 EPS testing and 

teardowns, manufacturer 

interviews, and 

distributor catalogues. 

Markups The factor increase applied to 

the production cost to arrive at 

the consumer purchase price 

including the OEM markup, 

the retailer and distributor 

markups, and sales tax. 

3.6 Discussed in the NOPR. 

Unit Energy 

Consumption 

The annual on­site electricity 

consumption of an EPS in 

kWh per year. 

24.1 

kWh/year 

Discussed in the NOPR. 

Electricity Prices The national residential sector 

average price in 2008 dollars 

per kilowatt­hour ($/kWh). 

$0.118/kWh Residential national 

average electricity price 

based on data from the 

Energy Information 

Administration (EIA) 

year 2006 Form 861b and 

the EIA AEO2009 

(Annual Energy Outlook, 

Year 2009), c both 

discussed in section 

5.1.3.2. 

Electricity Price 

Trend 

The projected changes in the 

price of electricity over the 

analysis period. 

11 percent 

increase by 

2030 

EIA AEO2009 residential 

reference case electricity 

price trend, discussed in 

section 5.1.3.2. 

b Department of Energy. Energy Information Administration. Table 8. Electricity Supply, Disposition, Prices, and 

Emissions. Report #:DOE/EIA­0383(2009) Early Release. December 2008. 

http://www.eia.doe.gov/oiaf/aeo/excel/aeotab_8.xls. 

c Department of Energy. Energy Information Administration. Form 861. 2006. 

http://www.eia.doe.gov/cneaf/electricity/page/eia861.html. 

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Input Description Average or 

Typical 

Value 

Sources 

Lifetime The total number of years in 

use after which the consumer 

retires the EPS and associated 

product from service. This 

may be before the EPS 

reaches the end of its useful 

life. 

6 years Discussed in the NOPR. 

Discount Rate The discount rate DOE 

estimates to be representative 

of EPS consumers, used to 

establish the value of future 

expenditures in the start year 

of analysis. 

5.6 percent Weighted average of 

residential financing 

methods, discussed in 

section 5.1.3.3. 

Start Year The year in which the EPS is 

purchased by the consumer. 

2013 The potential effective 

date of an energy 

conservation standard for 

Non­Class A EPSs, 

discussed in section 

5.1.3.3. 

5.1.3 Life­Cycle Cost Inputs 

The life­cycle cost of an EPS consists of the consumer purchase price plus all of the 

operating costs over the lifetime of the EPS, as shown in Eq. 5.10. When calculating the LCC, 

DOE discounted all future operating costs to the start year. See section 0 for further details on 

discounting. 

N 

LCC = PRICE +∑ OCt 

t Eq. 5.10 (1+ r)

where: LCC is the life­cycle cost in 2008 dollars, 

PRICE is the efficiency­related consumer purchase price in 2008 dollars, 

t =1 

∑

N 

is the sum over the EPS lifetime, from year 1 to year N, t =1 

N is the lifetime of EPS in years,
­

OCt is the operating cost in 2008 dollars in year t,
­

r is the discount rate, and
­

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t is the year for which operating cost is being determined (where the start year of 

the analysis is year 1). 

The following sections discuss efficiency­related consumer purchase price, operating 

cost, EPS lifetime, discount rate, and start year. 

5.1.3.1 Efficiency­Related Consumer Purchase Price Inputs

The consumer purchase price for an EPS is based on how the consumer purchases 

the EPS. DOE defined markups for converting manufacturer production costs into consumer 

purchase prices. The inputs for determining the consumer purchase price are listed below. 

• Efficiency­Related Materials Cost 

• Overall Markup 

DOE calculated the consumer purchase price for all EPSs based on Eq. 5.11: 

PRICE = ERMC × MARKUP Eq. 5.11 

where: PRICE is the efficiency­related consumer purchase price in 2008 dollars, 

ERMC is the efficiency­related materials cost in 2008 dollars, and 

MARKUP is the overall markup factor (product of original equipment 

manufacturer (OEM) markup, retailer or distributor markup, and sales tax). 

In the LCC analyses in several other DOE rulemakings,d the up­front cost of an appliance 

includes a purchase price for the appliance as well as a price for its installation. EPS installation, 

however, typically entails a consumer simply unpacking the EPS from the box it was sold in and 

connecting it to mains power and its associated product. Because the cost of this “installation” is 

not quantifiable in dollar terms, DOE did not include it in the LCC for Non­Class A EPSs. 

Furthermore, recall that most EPSs are purchased in conjunction with the consumer products that 

they power; thus, consumers usually do not pay the consumer purchase price of the EPS directly. 

For this determination analysis, DOE has also chosen to focus specifically on efficiency­related 

prices, as the efficiency­related prices depend directly on the different technologies 

manufacturers would use to reach various candidate standard levels. 

DOE researched information about each of the input variables that it used to calculate the 

consumer purchase price. DOE developed its manufacturer production costs through 

manufacturer interviews, EPS testing and teardowns, and research of distributor catalogues. 

Information from these sources was used to develop the bill of materials (BOM) cost, direct 

overhead costs, and labor costs that comprise the manufacturer production cost. 

d For examples, see the Energy Conservation Standards for Commercial Ice­Cream Freezers; Self­Contained 

Commercial Refrigerators, Commercial Freezers, etc., (74FR1092); the Packaged Terminal Air Conditioner and 

Packaged Terminal Heat Pump Energy Conservation Standards (73FR58772); and the Energy Conservation 

Standards for Residential Furnaces and Boilers (72FR65136). 

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Markups represent how the price of an EPS increases as it travels along the distribution 

chain from manufacturer to consumer. Generally, an OEM markup is first applied to create the 

EPS manufacturer selling price to a distributor or retailer. The retailer or distributor then applies 

another markup along with sales tax to create the consumer purchase price. Thus, the total 

markup factor is the product of the OEM markup, the distributor/retailer markup, and the sales 

tax. DOE developed OEM and retailer/distributor markups based on manufacturer interviews. 

The sales tax of 6.8 percent was computed based on a population­weighted average in 13 

geographic regions and large states. 

5.1.3.2 Operating Cost Inputs

The operating cost of the EPS consists of the cost of electricity associated with the 

consumer’s usage of the EPS. The inputs to the operating cost calculation are as follows: 

• Unit Energy Consumption (UEC) 

• Electricity Prices 

• Electricity Price Trend 

For every analysis year in the Non­Class A EPS LCC analysis, DOE computed the 

operating cost as shown in Eq. 5.12: 

OCt = UEC × EPt Eq. 5.12 

where: OCt is the cost associated with operating the EPS in year t in 2008 dollars, 

UEC is the unit energy consumption of the EPS in kWh per year, 

EPt is the electricity price in year t in 2008 dollars, 

t is the year for which operating cost is being determined (where the start year of the analysis is 

year 1). 

Although operating costs for several other DOE rules have encompassed repair and 

maintenance costs,e DOE did not consider those costs (which are usually associated with larger 

products and appliances) in the draft LCC for the determination analysis of Non­Class A EPSs. 

In making this decision, DOE recognized that the service life of an EPS typically exceeds that of 

the consumer product with which it is designed to operate. Thus, a consumer would not incur 

repair or maintenance costs for an EPS. Also, if an EPS did fail, DOE expects that consumers 

would typically discard the EPS and purchase a replacement. 

e For examples, see the Energy Conservation Standards for Commercial Ice­Cream Freezers; Self­Contained 

Commercial Refrigerators, Commercial Freezers, etc., (74FR1092); the Packaged Terminal Air Conditioner and 

Packaged Terminal Heat Pump Energy Conservation Standards (73FR58772); and the Energy Conservation 

Standards for Residential Furnaces and Boilers (72FR65136). 

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The unit energy consumption is the site energy use associated with operating the EPS. 

The UEC varies with the product efficiency and the number of hours that the product is used. 

Generally, the unit energy consumptions associated with candidate standard level EPSs (i.e., 

EPSs with efficiencies greater than the baseline EPSs) are less than the UECs associated with 

baseline EPSs. For the LCC and PBP analysis described in this section, UECs representing 

nominal usage were developed and used. 

Electricity prices are the prices paid by consumers for electricity during the years of 

analysis. Multiplying the UEC of a particular EPS by the electricity price for a given year yields 

the EPS’s operating cost for that year. DOE developed residential sector future electricity prices 

using the residential sector national average electricity price in EIA’s most recent (year 2006) 

Form 861 along with the residential sector national average electricity price trend from EIA’s 

Annual Energy Outlook year 2009 reference case. Though the AEO2009 contains actual 

residential sector national average electricity prices for 2008 (note that they are in 2007 dollars), 

DOE uses EIA Form 861 instead for the electricity price because the form contains actual sales 

data from electric utilities across the country and thus is of a higher resolution. 

DOE’s LCC and PBP analysis, however, is in 2008 dollars and depends on the most upto­date electricity price information. Because the EIA Form 861 electricity price is in 2006 

dollars, DOE first converted the price to 2008 dollars using annual average consumer price 

indices (CPIs) from the U.S. Bureau of Labor Statistics.f To do this, DOE multiplied the 2006 

electricity price by the ratio of the 2008 CPI to the 2006 CPI, as shown in Table 5.2, to produce 

the 2006 electricity price in 2008 dollars. Next, DOE projected the 2006 electricity price to 2008 

by multiplying the price by the ratio of the AEO2009 residential 2008 electricity price to the 

AEO2009 residential 2006 electricity price, as shown in Table 5.3. DOE thus arrived at the 2008 

residential sector national average initial electricity price of $0.121/kWh in 2008 dollars. An 

equation detailing the creation of the 2008 initial electricity price is shown in Eq. 5.13. 

 CPI   AEO  2008 2006 2008 2008 IEP2008 = EIA2006 × 

×  Eq. 5.13     CPI 2006   AEO2006 

where: IEP2008 is the 2008 initial electricity price in 2008 dollars, 2008

EIA2006 is the EIA Form 861 2006 electricity price in 2006 dollars, 2006

CPI is the 2008 consumer price index, 2008 

CPI 2006 is the 2006 consumer price index, 

AEO2008 is the AEO2009 2008 electricity price in 2007 dollars, and 

f Bureau of Labor Statistics. Table Containing History of CPI­U U.S. All Items Indexes and 

Annual Percent Changes From 1913 to Present. 2009. 

ftp://ftp.bls.gov/pub/special.requests/cpi/cpiai.txt. 

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AEO2006 is the AEO2009 2006 electricity price in 2007 dollars. 

Table 5.2 Annual Average Consumer Price Indices 

Year 

Annual Average Consumer Price 

Index 

2006 201.6 

2008 215.303 

Ratio 1.1 

Table 5.3 AEO2009 Electricity Prices
­

AEO2009 Price 

Year 2007$/kWh 

2006 0.1065 

2008 0.1103 

Ratio 1.0363 

To develop electricity prices for all of the years in the LCC analysis, DOE normalized the 

AEO2009 residential sector electricity prices using the AEO2009 electricity price for the year 

2008 to create the electricity price trend. The electricity price trend is shown in Figure 5.3. The 

start year of analysis (2013) and the associated scaling factor are indicated in the figure. The 

normalized AEO2009 price trend was then used as a set of scaling factors to produce the 

electricity price for each of the analysis years, as shown in Eq. 5.14. DOE used an electricity 

price of $0.118/kWh in the start year of 2013, based on the scaling of the initial electricity price 

($0.121/kWh) by the 2013 scaling factor 0.98. 

EP = IEP2008 × AEOTREND Eq. 5.14 t 2008 t 

where: EPt is the electricity price in year t in 2008 dollars, 

IEP2008 is the 2008 initial electricity price in 2008 dollars, 2008

AEOTRENDt is the scaling factor for year t based on the electricity price trend, 

and 

t is the year for which electricity price is being determined (where the start year of 

the analysis is year 1). 

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Figure 5.3 Normalized AEO2009 Residential Sector Reference Case Electricity Price 

Trend 

Scaling Relative to 2008

1.15

1.10

1.05

1.00

0.95

0.90

Start Year:

2013

Scaling:

0.98

2005 2010 2015 2020 2025 2030 2035

Year

5.1.3.3 Other Inputs to the LCC Analysis

To compute the life­cycle cost of an EPS, the operating costs of the EPS must be 

discounted to the start year of the analysis period. DOE assumes that money consumers spend in 

the future is worth less to them than money they spend today. For example, a dollar obtained 

today may only be worth 90 cents to the consumer a year from now. Thus, discounting reflects 

the current value of money spent or saved in the future. The inputs that DOE used to perform the 

discounting for the LCC and PBP analysis are as follows: 

• EPS Lifetime 

• Discount Rate 

• Start Year 

The EPS lifetime is discussed in the NOPR. The discount rate and start year are described 

in the sections below. 

START YEAR AND EFFECTIVE DATE OF STANDARD 

The effective date is the date when a new standard becomes operative, i.e., the date by 

which EPS manufacturers must manufacture products that comply with the standard. For the 

purpose of this analysis, DOE has assumed that a Non­Class A EPS efficiency standard would be 

published in conjunction with an efficiency standard for Class A EPSs. Publication of a final 

standard for Class A EPSs is scheduled for July of 2011 (42 U.S.C. 6295(u)(6)(D)(I)), and the 

effective date of this standard is July 1, 2013 (42 U.S.C. 6295(u)(6)(D)(II)). DOE assumes that 

all consumers will purchase an EPS in the year of the effective date of standard. Thus, the start 

year for the LCC analysis is 2013. 

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DISCOUNT RATE 

The calculation of the LCC required DOE to use a discount rate to determine the present 

value (at the start year of the LCC analysis) of the money the consumer would spend to operate 

the EPSs over their lifetime. Because consumers can use a variety of financial means to purchase 

an EPS, the discount rate should equal the average cost of capital to the consumer. DOE assumed 

these financial means, listed in Table 5.4, to be similar to the ones residential consumers use 

when purchasing and financing replacement appliances for the home. DOE’s approach involved 

identifying all possible debt or asset classes those consumers might use to purchase replacement 

equipment, including household assets that might be affected indirectly. 

DOE estimated the shares of the various debt and equity classes in the typical U.S. 

household portfolio using the Federal Reserve’s Survey of Consumer Finances (SCF)

g data for 

1989, 1992, 1995, 1998, 2001, and 2004. DOE also used SCF data to determine rates of return 

for each class. DOE then calculated an average rate weighted by the share of each class of debt 

or equity, equal to 5.6 percent, to represent a household discount rate, shown in Table 5.4. 

Table 5.4 Shares and Interest or Return Rates Used for Household Debt and Equity 

Types 

Type 

Average Share of 

Household Debt Plus 

Equity* [%] 

Mean Real 

Effective Discount 

Rate** [%] 

Home Equity Loans 3.6 4.0 

Credit Cards 2.0 11.0 

Other Installment Loans 1.7 6.0 

Other Residential Loans 4.9 4.6 

Other Line of Credit 0.5 8.7 

Checking Accounts 4.5 0.0 

Savings and Money Market Accounts 15.7 2.3 

Certificates of Deposit 9.0 2.4 

Savings Bonds 1.5 3.5 

Bonds 10.0 4.2 

Stocks 29.1 8.8 

Mutual Funds 17.5 7.0 

Total: 100 Weighted 

Average: 5.6 

* Not including primary mortgage or retirement accounts.
­

** Adjusted for inflation and, for home equity loans, loan interest tax deduction.
­

g The Federal Reserve Board. Survey of Consumer Finances. 

http://www.federalreserve.gov/PUBS/oss/oss2/scfindex.html. 

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5.1.4 Payback Period Inputs 

5.1.4.1 Definition and Inputs

The PBP is the amount of time it takes the consumer to recover the assumed higher 

purchase cost of a more energy­efficient EPS as a result of lower operating costs, in comparison 

with a specific less energy­efficient EPS. In general, a PBP that is longer than the lifetime of the 

EPS is an indicator that a consumer purchasing that EPS will realize negative LCC savings. This 

is because the increased purchase price is too great for the consumer to recover in operating cost 

savings before the EPS and its associated product are retired from use. 

Numerically, the PBP is the ratio of the increase in purchase cost (i.e., from a less 

efficient design to a more efficient design) to the decrease in first year operating costs. This type 

of calculation is known as a “simple” PBP, because it does not take into account changes in 

operating cost over time or the time value of money. That is, the calculation is done at an 

effective discount rate of zero percent. The PBP uses the same inputs as the LCC calculation 

described in section 5.1.3, except that electricity price trends are not required. The required 

electricity cost is only for the year in which DOE has a new energy conservation standard for 

Non­Class A EPS to take effect—in this case, 2013. Thus, the electricity price DOE uses in the 

PBP calculation for electricity cost is the price projected for 2013, expressed in 2008 dollars. 

PBPs are expressed in years. 

The equation for PBP is: 

ΔPRICEk →L PBPk →L = Eq. 5.15 ΔOC1,k →L 

where: PBPk→L is the payback period (in years) that a consumer replacing an EPS at 

CSL k with an EPS at CSL L would experience, 

ΔPRICE → is the difference in efficiency­related consumer purchase price k L 

between an EPS at CSL L and an EPS at CSL k, and 

OC is the difference in the first year of operating costs between an EPS at 1,k→L 

CSL L and an EPS at CSL k. 

PBPs greater than the life of the EPS generally indicate that the increased efficiencyrelated consumer purchase price of the more efficient product is not recovered in reduced 

operating costs over the lifetime of that product. It is also possible for a more efficient EPS to 

have a lower efficiency­related consumer purchase price than the baseline EPS. In this case, the 

consumer would immediately realize financial benefits and there would be no PBP. 

Note that because the simple PBP does not take into account changes in operating cost 

over time or the time value of money, there are some situations where consumers will realize 

negative LCC savings when purchasing an EPS with a simple PBP that is slightly less than the 

EPS lifetime. Alternatively, there are some situations where consumers will realize positive LCC 

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savings when purchasing an EPS with a simple PBP that is slightly greater than the EPS lifetime 

(e.g. when electricity prices increase over the lifetime). As done for several other DOE 

rulemakings,h DOE uses the simple PBP to express to the public the approximate amount of time 

that a consumer will have to operate an EPS to recover the increased purchase cost through 

savings in electricity expenditures. When assessing the economic benefits of a standard, DOE 

prefers to use the LCC savings due to its higher fidelity (including discounting and the change in 

electricity prices over time). 

h For examples, see the Energy Conservation Standards for Residential Furnaces and Boilers (72FR65136) and the 

Packaged Terminal Air Conditioner and Packaged Terminal Heat Pump Energy Conservation Standards 

(73FR58772). 

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CHAPTER 6 NATIONAL IMPACT ANALYSIS 

6.1 Introduction 

This chapter provides supplemental information on the methodology DOE used in its 

determination analysis to calculate the National Energy Savings (NES) and the Net Present 

Value (NPV) as part of the National Impact Analysis (NIA) for non­Class A external power 

supplies (EPSs). 

The calculations for NES and NPV were implemented in two Microsoft® Excel 

workbooks that can be downloaded from the EERE web site.a The workbooks are identical in 

design. The first workbook, titled “NCAEPS Determination NOPR NIA PartA.xls” contains the 

NES and NPV calculations for four types of EPS: 

A) Multiple voltage EPSs used for multifunction devices 

B) Multiple voltage EPSs used for Xbox 360 video game consoles 

C) High power EPSs 

D) EPSs used to power medical devices 

The second workbook, titled “NCAEPS Determination NOPR NIA PartB.xls” contains the NES 

and NPV calculations for two EPSs: 

A) EPSs used for battery chargers for cordless handheld vacuums
­

B) EPSs used for battery chargers for power tools
­

This document is a guide to these two workbooks. Section 6.3 provides an overview of 

the layout of the workbooks. Section 6.4 contains a step­by­step walkthrough of the calculation 

of NES and NPV, using as an example the multiple­voltage EPSs used with Xbox 360 video 

game consoles. References in the walkthrough to specific cells refer to cell in the workbook with 

the filename: “NCAEPS Determination NOPR NIA PartA.xls” 

The analyses referred to collectively as the national impact analysis are depicted 

graphically in Figure III.19 of the NCA EPS NOPR. The national impact analysis consists of 

four calculations: 

•	 National inventory, which measures the total number of units affected by the 

standard; 

•	 Unit energy savings (UES), which measures the change in unit energy consumption 

due to the impact of the standard; 

a Available for download from the EERE website: 

http://www.eere.energy.gov/buildings/appliance_standards/residential/battery_external.html 

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•	 National energy savings (NES), which combines unit energy savings and the national 

inventory to obtain the aggregate energy savings generated by the standard; and 

•	 Net present value, which calculates the net present savings and costs of a standard by 

comparing the present value of energy savings from national energy savings with the 

present value of the increased consumer purchase costs associated with the standard. 

6.2 National Inventory 

DOE used a national inventory model to represent the installed base of EPSs that a 

standard would affect. Because the EPSs remain in use for several years, the national inventory 

represents the stock of EPSs in service for any given year of the analysis period. It is important 

to track the date of manufacture, or vintage, of products in the installed base because the energy 

efficiency and price of products sold changes over time. DOE used three inputs to calculate the 

national inventory for the determination analysis: start­year shipments, shipment growth rates, 

and product lifetimes. Values for these three inputs are given in section Section III of the NCA 

EPS NOPR. 

Table 6.1 shows how the national inventory model tracks the number of products by 

vintage in the installed base for a given year. In 2013, 100 units are sold and enter the installed 

base. In this example, the product has an average lifetime of 3 years. Therefore, the units sold in 

2013 are retired at the end of 2015, and removed from the inventory for 2016. The shipment 

growth rate is 5 percent, so 105 units are sold in 2014. These units are added to the 100 units that 

remain in the installed base from the year before. In 2014, 205 units are in the installed base. 

This process of adding to and subtracting from the installed base is carried forward throughout 

the analysis period. Figure 6.1 shows the flow of the calculations. 

Table 6.1 Example National Inventory Table 

Vintage Year of Analysis 

2013 2014 2015 2016 2017 2018 2019 

2013 100 100 100 ­ ­ ­ ­

2014 ­ 105 105 105 ­ ­ ­

2015 ­ ­ 110 110 110 ­ ­

2016 ­ ­ ­ 116 116 116 ­

2017 ­ ­ ­ ­ 122 122 122 

2018 ­ ­ ­ ­ ­ 128 128 

2019 ­ ­ ­ ­ ­ ­ 134 

Total 100 205 315 331 348 366 384 

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Electricity Price 

National Energy
­

Savings ($)
­

Discount Rate Net Present Value 

Figure 6.1 Flow Chart Showing the Calculation of National Energy Savings and Net 

Present Value 

6.3 Layout of the NES­NPV Workbook 

The NES­NPV workbook contains 10 worksheets (tabs) as follows: 

Cover 

This worksheet gives a brief description of the functions of the tabs within the workbook. 

1 Controls 

This worksheet contains the controls and outputs of the NES­NPV calculations. 

Input controls are on the left side of the worksheet, and highlighted in light yellow. The controls 

are arranged, from top to bottom, in the following manner: 

B5 to B8 Market Growth Rate 

B12 to B15 Lifetime (Not used in this analysis) 

B19 to B22 Base Case Standard Level 

B26 to B29 Standard Case Standard Level 

Unit Energy Savings 

National Inventory 

National Energy
­

Savings (kWh)
­

National
­

Improvement Costs
­

Unit Improvement
­

Cost
­

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C31 Efficiency Progression
­

C33 Market Response to Standard (Not used in this analysis)
�

C35 Electricity Price Case (Not used in this analysis)
�

B39 Electricity Price Ratio (Not used in this analysis)
�

C42 Discount Rate
­

Outputs for NES and NPV are on the right side of the worksheet and are arranged as follows: 

G4 to G8 National Energy Savings in kWh 

H4 to H8 National Energy Savings in Quadrillion BTU 

I4 to I8 National Energy Savings in 2008$ 

J4 to J8 Total Costs in 2008$ 

K4 to K8 Net Present Value in 2008$ 

In addition, 3 output figures give the annual results as follows: 

Figure 1 National Energy Savings in 2008$ 

Figure 2 Total Costs in 2008$ 

Figure 3 Net Present Value in 2008$ 

2 Inputs 

This worksheet contains all the input values used in the calculations. The inputs are divided into 

four categories as follows: 

Rows 9 to 84 Constant Values and Structural Values 

Rows 85 to 195 Market and Usage Values 

Rows 196 to 389 Variable Values 

Rows 390 to 411 Model Reference Values 

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3 NES 

This worksheet contains the National Energy Savings calculations. In this worksheet, results are 

displayed in units of kWh. 

Columns G to AT Results/Values for each year from 2008 to 2047 

Column AU Total results for all years 

Rows 1 to 6 Summary Results 

Rows 41 to 45 Results for EPS Type A 

Rows 80 to 84 Results for EPS Type B 

Rows 119 to 123 Results for EPS Type C 

Rows 158 to 162 Results for EPS Type D 

4 NPV 

This worksheet contains the Net Present Value calculations. 

Columns G to AT Results/Values for each year from 2008 to 2047 

Column AU Total results for all years 

Rows 2 to 6 NES in kWh (copied from 3 NES) 

Row 8 Electricity Price ($/kWh) 

Rows 10 to 14 NES in $ (non­discounted) 

Rows 16 to 20 Incremental Installed Costs in $ (non­discounted) 

Row 22 Discount Multiplier 

Rows 24 to 28 NES in 2008$ (discounted) 

Rows 30 to 34 Incremental Installed Costs in 2008$ (discounted) 

Rows 36 to 40 NPV in 2008$ (discounted) 

Rows 75 to 79 Incremental Installed Costs for EPS Type A 

Rows 114 to 118 Incremental Installed Costs for EPS Type B 

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Rows 153 to 187 Incremental Installed Costs for EPS Type C
­

Rows 192 to 196 Incremental Installed Costs for EPS Type D
­

5 Inventory 

This worksheet contains the rolling inventory for each EPS type. 

Columns D to AQ Inventory for each year from 2008 to 2047 

Column AS Shipments for each year 

Rows 4 to 46 Inventory for EPS Type A 

Rows 50 to 92 Inventory for EPS Type B 

Rows 96 to 138 Inventory for EPS Type C 

Rows 142 to 184 Inventory for EPS Type D 

6, 7, 8, 9 Distribution Tables 

This section addresses the following worksheets: 

6 MV­MFD EPS Dist Tables
­

7 MV­Xbox EPS Dist Tables
­

8 High­Power EPS Dist Tables
­

9 MED EPS Dist Tables
­

These worksheets contain the distribution of shipments by efficiency for each year. These 

worksheets also contain the calculations for unit energy savings (UES) and incremental installed 

costs. 

Columns C to O display the scenario where efficiency does not progress in the absence of 

a standard. Because the distribution of shipments by efficiency level in this scenario remains 

static (unchanging), this walkthrough will hereafter refer to this scenario as the static scenario. 

Within this group of columns: 

• Columns D to G display the distribution of efficiency by year. 

• Column L displays the weighted­average unit energy consumption 

• Column M displays the unit energy savings 

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• Column N displays the unit cost 

• Column O displays the incremental unit cost (as compared the unit cost at CSL0) 

Columns AE to AQ display the scenario where efficiency does progress even without a 

standard. Because the distribution of shipments by efficiency level is dynamic (changing), this 

walkthrough will hereafter refer to this scenario as the dynamic scenario. Within this group of 

columns: 

• Columns AF to AI display the distribution of efficiency by year. 

• Column AN displays the weighted­average unit energy consumption 

• Column AO displays the unit energy savings 

• Column AP displays unit cost 

• Column AQ displays the incremental unit cost (as compared the unit cost at CSL0) 

Starting at the top, and moving down, forecasts are outlined for each CSL, with CSL 0 

(Rows 15 to 59) at the top, CSL 1 (Rows 61 to 105) and CSL 2 (Rows 107 to 151) in the middle, 

and CSL 3 (Rows 153 to 197) at the bottom. 

6.4 NES­NPV Calculation Walkthrough 

This section presents an example walkthrough for the calculation of NES and NPV for the EPSs 

used to power Xbox 360 video game consoles. For this walkthrough, DOE will conduct the 

calculations for a dynamic scenario, and with a standard set at CSL 1. For the calculation of 

NPV, DOE will use a 3 percent discount rate. When referring to specific cells in the 

walkthrough, DOE will use the following format: 

Tab Name ­ Cell 

6.4.1 Calculation of Unit Energy Savings 

For each year in the analysis period: 

Step 1: Weighted Average Unit Energy Consumption (UEC) in the Base Case 

Starting in 2013 we take the base case distribution of shipments by CSL 

[7 MV­Xbox EPS Dist Tables ­ AG25 to AJ25] 

and the UEC by CSL 

[Inputs – C182 to F182]. 

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Using these values, we calculate the weighted average (using the Excel SUMPRODUCT 

function). This result is displayed in [7 MV­Xbox EPS Dist Tables – AN25]. 

Table 6.2 Unit Energy Consumption in the Base Case (2013) 

Candidate Standard Level CSL 0 CSL 1 CSL 2 CSL 3 Weighted 

Average 

Percentage of Current UEC 

Shipments 

2.5% 92.5% 5% 0% 

UEC (kWh/year) 126.01 32.44 31.85 26.57 34.75 

This calculation is then repeated for each year new products are shipped during the analysis 

period, with the results displayed in [7 MV­Xbox EPS Dist Tables – AN25 to AN44]. 

Step 2: Weighted Average Unit Energy Consumption in the Standards Case 

Starting in 2013 we take the standards case distribution of shipments by CSL
­

[7 MV­Xbox EPS Dist Tables ­ AG71 to AJ71]
­

and the UEC by CSL
­

[Inputs – C182 to F182].
­

Using these values, we calculate the weighted average (using the Excel SUMPRODUCT 

function). This result is displayed in [7 MV­Xbox EPS Dist Tables – AN71]. 

Table 6.3 Unit Energy Consumption in the Standards Case (2013) 

Candidate Standard Level CSL 0 CSL 1 CSL 2 CSL 3 Weighted 

Average 

Percentage of Current UEC 

Shipments 

0% 95% 5% 0% 

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UEC (kWh/year) 126.01 32.44 31.85 26.57 32.41 

This calculation is then repeated for each year new products are shipped during the analysis 

period, with the results displayed in [7 MV­Xbox EPS Dist Tables – AN71 to AN90]. 

Step 3: Calculating the Unit Energy Savings (UES) due to the standard: 

Using the results from steps 1 and 2, we calculate the difference in UEC for each year. 

Starting in 2013, we take the UEC for the base case: 

[7 MV­Xbox EPS Dist Tables – A025] 34.75 kWh/year 

and subtract the UEC for the standard case: 

[7 MV­Xbox EPS Dist Tables – A071] 32.41 kWh/year 

Yielding a UES of 2.34 kWh/year 

This result is displayed in [7 MV­Xbox EPS Dist Tables – AP71]. This calculation is repeated 

for each year new products are shipped during the analysis period, with the results displayed in 

[7 MV­Xbox EPS Dist Tables – AP71 to AP90]. 

6.4.2 Calculation of National Energy Savings in kWh 

To calculate energy saving in a year, we combine the inventory of products for that year with the 

unit energy savings for each shipment year. Performing this calculation for each year of the 

analysis period generates the National Energy Savings in kWh. 

For example, in 2018: 

We take the unit energy savings by shipment year:
­

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[7 MV­Xbox EPS Dist Tables – AP71 to AP90] 

Table 6.4 Unit Energy Savings by Shipment Year 

Year UES 

2013 2.3391 

2014 1.8713 

2015 1.4035 

2016 0.9357 

2017 0.4678 

2018 0.0000 

2019 0.0000 

2020 0.0000 

2021 0.0000 

2022 0.0000 

2023 0.0000 

2024 0.0000 

2025 0.0000 

2026 0.0000 

2027 0.0000 

2028 0.0000 

2029 0.0000 

2030 0.0000 

2031 0.0000 

2032 0.0000 

We then take the inventory of units in 2018: 

[5 Inventory – N56 to N75] 

Table 6.5 Unit Inventory In 2018 

Year 

Number of 

Units 

2013 ­

2014 4,776,209 

2015 4,919,495 

2016 5,067,080 

2017 5,219,093 

2018 5,375,666 

2019 ­

2020 ­

2021 ­

2022 ­

2023 ­

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2024 ­

2025 ­

2026 ­

2027 ­

2028 ­

2029 ­

2030 ­

2031 ­

2032 ­

Combining these tables yields: 

Table 6.6 Combination of Tables 6.4 and 6.5 

Shipment 

Year 

UES 

kWh 

Number 

of Units 

Total 

Energy 

Savings 

2013 2.3391 ­ ­

2014 1.8713 4,776,209 8,937,720 

2015 1.4035 4,919,495 6,904,511 

2016 0.9357 5,067,080 4,741,267 

2017 0.4678 5,219,093 2,441,492 

2018 0.0000 5,375,666 0 

2019 0.0000 ­ ­

2020 0.0000 ­ ­

2021 0.0000 ­ ­

2022 0.0000 ­ ­

2023 0.0000 ­ ­

2024 0.0000 ­ ­

2025 0.0000 ­ ­

2026 0.0000 ­ ­

2027 0.0000 ­ ­

2028 0.0000 ­ ­

2029 0.0000 ­ ­

2030 0.0000 ­ ­

2031 0.0000 ­ ­

2032 0.0000 ­ ­

Total Energy Savings (2018) 23,024,800* 

*Total value may be different due to rounding. 

The resulting total is displayed in: 

[3 NES – Q3] 

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This calculation is repeated for each year, until no inventory is left to generate savings. In the 

case of the Xbox 360, which has a lifetime of 5 years, the last year of shipments is 2032, so the 

last year of savings would be 2036. The values by year are displayed in: 

[3 NES – G3 to AT3] and the sum of all years is displayed in [3 NES – AU3]. 

6.4.3 Calculation of National Energy Savings in 2008$ 

To convert the NES from kWh to discounted 2008$, we combine the results of 

­National Energy Savings in kWh [3 NES – G3 to AT3] with 

­the electricity price for each year [2 Inputs – C287 to AP287] 

The results for each year are displayed in: 

[4 NPV – G11 to AT11] with the total for all years in [4 NPV –AU11] 

These values are multiplied against 

­the discount multiplier for each year from [4 NPV – G22 to AT22] 

The results for each year are displayed in: 

[4 NPV – G25 to AT25] with the total for all years in [4 NPV –AU25] 

6.4.4 Calculating Incremental Unit Cost Increases 

Incremental Unit Costs are calculated in the same way that unit energy savings are calculated. 

Step 1: Weighted Average Unit Cost in the Base Case 

Starting in 2013 we take the base case distribution of shipments by CSL
­

[7 MV­Xbox EPS Dist Tables ­ AG25 to AJ25]
­

and the unit cost by CSL
­

[Inputs – C192 to F192].
­

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Using these values, we calculate the weighted average (using the Excel SUMPRODUCT 

function). This result is displayed in [7 MV­Xbox EPS Dist Tables – AQ25]. 

Table 6.7 Unit Cost in the Base Case 

Candidate Standard Level CSL 0 CSL 1 CSL 2 CSL 3 Weighted 

Average 

Percentage of Current Unit Cost 

Shipments 

2.5% 92.5% 5% 0% 

Unit Cost ($) 19.07 28.10 28.48 38.27 27.90 

This calculation is then repeated for each year new products are shipped during the analysis 

period, with the results displayed in [7 MV­Xbox EPS Dist Tables – AQ25 to AQ44]. 

Step 2: Weighted Average Unit Cost in the Standards Case 

Starting in 2013 we take the standards case distribution of shipments by CSL
­

[7 MV­Xbox EPS Dist Tables ­ AG71 to AJ71]
­

and the unit cost by CSL
­

[Inputs – C192 to F192].
­

Using these values, we calculate the weighted average (using the Excel SUMPRODUCT 

function). This result is displayed in [7 MV­Xbox EPS Dist Tables – AQ71]. 

Table 6.8 Unit Cost in the Standards Case 

Candidate Standard Level CSL 0 CSL 1 CSL 2 CSL 3 Weighted 

Average 

Percentage of Current Unit Cost 

Shipments 

0% 95% 5% 0% 

Unit Cost ($) 19.07 28.10 28.48 38.27 28.12 

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This calculation is then repeated for each year new products are shipped during the analysis 

period, with the results displayed in [7 MV­Xbox EPS Dist Tables – AQ71 to AQ90]. 

Step 3: Calculating the Unit Incremental Cost Increase due to the standard: 

Using the results from steps 1 and 2, we calculate the difference in unit cost for each year. 

Starting in 2013, we take the unit cost for the standards case:
­

[7 MV­Xbox EPS Dist Tables – AQ71] $28.12
­

And subtract the unit cost for the base case:
­

[7 MV­Xbox EPS Dist Tables – AQ25] $27.90
­

Yielding an incremental unit cost increase of $0.23*
­

(* Note, values may be different due to rounding.)
­

This result is displayed in [7 MV­Xbox EPS Dist Tables – AR71]. This calculation is repeated 

for each year of the analysis period, with the results displayed in [7 MV­Xbox EPS Dist Tables – 

AR71 to AR90]. 

6.4.5 Calculation of National Costs in $ (non­discounted) 

To calculate total improvement costs, we combine the weighted­average incremental unit costs 

from the previous step with the numbers of EPSs shipped. Performing this calculation for each 

year of the analysis period generates the total costs in $ (non­discounted). 

Take the incremental unit cost: 

[7 MV­Xbox EPS Dist Tables – AR71 to AR90] 

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Table 6.9 Unit Incremental Cost by Shipment Year
­

Shipment Year 

Unit Incremental 

Cost Increase ($) 

2013 0.2258 

2014 0.1807 

2015 0.1355 

2016 0.0903 

2017 0.0452 

2018 0.0000 

2019 0.0000 

2020 0.0000 

2021 0.0000 

2022 0.0000 

2023 0.0000 

2024 0.0000 

2025 0.0000 

2026 0.0000 

2027 0.0000 

2028 0.0000 

2029 0.0000 

2030 0.0000 

2031 0.0000 

2032 0.0000 

Take the shipments of EPSs by year. 

[5 Inventory – AS56 to AS75] 

Table 6.10 Unit Shipments by Shipment Year 

Shipment Year Vintage Number of Units Shipped 

2013 4,637,096 

2014 4,776,209 

2015 4,919,495 

2016 5,067,080 

2017 5,219,093 

2018 5,375,666 

2019 5,536,935 

2020 5,703,044 

2021 5,874,135 

2022 6,050,359 

2023 6,231,870 

2024 6,418,826 

2025 6,611,391 

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2026 6,809,732 

2027 7,014,024 

2028 7,224,445 

2029 7,441,178 

2030 7,664,414 

2031 7,894,346 

2032 8,131,176 

Combining these tables yields: 

Table 6.11 Combination of Tables 6.9 and 6.10 

Shipment 

Year 

Unit Incremental 

Cost Increase ($) Number of Units Total Costs by Year 

2013 0.2258 4,637,096 1,047,056 

2014 0.1807 4,776,209 862,831 

2015 0.1355 4,919,495 666,537 

2016 0.0903 5,067,080 457,689 

2017 0.0452 5,219,093 235,710 

2018 0.0000 5,375,666 0 

2019 0.0000 5,536,935 0 

2020 0.0000 5,703,044 0 

2021 0.0000 5,874,135 0 

2022 0.0000 6,050,359 0 

2023 0.0000 6,231,870 0 

2024 0.0000 6,418,826 0 

2025 0.0000 6,611,391 0 

2026 0.0000 6,809,732 0 

2027 0.0000 7,014,024 0 

2028 0.0000 7,224,445 0 

2029 0.0000 7,441,178 0 

2030 0.0000 7,664,414 0 

2031 0.0000 7,894,346 0 

2032 0.0000 8,131,176 0 

Total Costs 3,269,891 

The resulting total by year is displayed in:
­

[4 NPV – G17 to AT17]
­

and the sum of all years is displayed in:
­

[4 NPV – AU17].
­

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6.4.6 Calculation of National Costs in 2008$ 

To convert the national costs to discounted 2008$, we combine the results of 

­National Costs [4 NPV – G17 to AT17] with 

­the discount multiplier for each year from [4 NPV – G22 to AT22] 

The results for each year are displayed in: 

[4 NPV – G31 to AT31] with the total for all years in [4 NPV –AU31] 

6.4.7 Calculation of Net Present Value in 2008$ 

To calculate Net Present Value, we simply calculate the difference between 

National Energy Savings (in 2008$) [4 NPV – G25 to AT25] and 

National Costs (in 2008$) [4 NPV – G31 to AT31] 

The results for each year are displayed in: 

[4 NPV – G37 to AT37] with the total for all years in [4 NPV –AU37] 

6.5 Net Present Value Results 

This section contains tables which show the net present value (NPV) of standards for non­Class 

A external power supplies using discount rates of 3 percent (Table 6.12) and 7 percent (Table 

6.13). The NPV of standards at each candidate standard level (CSL) is expressed as a range, 

reflecting uncertainty about the rate of efficiency improvements in the absence of a standard. The 

lower value represents the NPV using a base case efficiency forecast where efficiency would 

improve even in the absence of a standard. The higher value represents the NPV using a base 

case efficiency forecast where efficiency would not improve without a standard. These efficiency 

forecasts are explained in section III.A.3 “Market Assessment ­ Shipments, Efficiency 

6­17 

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Distributions, and Market Growth” of the NOPR and can be viewed in the NES­NPV Excel 

workbooks.b Negative values are shown in parentheses. 

Table 6.12 Net Present Value of Standards at 3 Percent Discount Rate 

Type of EPS 

Net Present Value at 3 Percent Discount Rate 

2013 to 2042 ($ millions) 

CSL 1 CSL 2 CSL 3 

Multi­Voltage for 

Multifunction Devices 113.6 ­ 129.1 139.3 ­ 157.4 155.9 ­ 174.4 

Multi­Voltage for Xbox 360 13.1 ­ 189.4 (0.96) ­ 187.5 (517.1) – (341.0) 

High Power (>250 W) 1.8 ­ 2.3 2.1 ­ 2.7 2.36 ­ 2.94 

For Medical Devices 31.9 ­ 56.7 141.8 ­ 192.0 80.9 ­ 129.9 

For Battery Chargers for 

Floor Care Appliances 2.8 ­ 4.8 4.4 ­ 6.3 8.0 ­ 10.1 

For Battery Chargers for 

Power Tools 1.3 ­ 2.3 2.62 ­ 3.5 4.1 ­ 5.1 

Note: Negative values are shown in parentheses.
­

b Available for download from the EERE website: 

http://www.eere.energy.gov/buildings/appliance_standards/residential/battery_external.html 

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Table 6.13 Net Present Value of Standards at 7 Percent Discount Rate
­

Type of EPS 

Net Present Value at 7 Percent Discount Rate 

2013 to 2042 ($ millions) 

CSL 1 CSL 2 CSL 3 

Multi­Voltage for 

Multifunction Devices 59.9 ­ 67.8 68.2 ­ 76.9 75.9 ­ 84.8 

Multi­Voltage for Xbox 360 9.4 ­ 100.9 0.7 ­ 98.4 (316.4) – (225.2) 

High Power (>250 W) 0.9 ­ 1.2 1.1 ­ 1.4 1.2 ­ 1.5 

For Medical Devices 16.9 ­ 28.2 74.2 ­ 97.8 26.8 ­ 49.5 

For Battery Chargers for 

Floor Care Appliances 1.6 ­ 2.6 2.5 ­ 3.5 4.5 ­ 5.6 

For Battery Chargers for 

Power Tools 0.7 ­ 1.2 1.5 ­ 1.9 2.3 ­ 2.8 

Note: Negative values are shown in parentheses.
­

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APPENDIX A. NON­CLASS A EXTERNAL POWER SUPPLY COST­EFFICIENCY 

ESTIMATION SURVEY 

Navigant Consulting, Inc. (NCI) is conducting an engineering analysis to understand the 

relationship between manufacturers’ cost and the efficiencya of external power supplies (EPSs). 

This engineering analysis is part of a larger determination analysis on whether the U.S. 

Department of Energy should conduct an energy conservation standards rulemaking on nonClass A external power supplies (NCA EPSs). These EPSs are defined in contrast to “Class A” 

EPSs as defined by EISA 2007 as being less than 250 W output power, not for medical devices, 

and single­output voltage – among other criteria. Through this worksheet, NCI is seeking your 

guidance on design changes you might make to external power supplies to improve their 

efficiency. 

NCI is currently focusing its analysis on: 

1.	­ A medical EPS with a nameplate output rating of 18 W and 12 V 

2.	­ A multiple­voltage EPS with a nameplate output rating of 40 W with 16 V and 32 V 

busses 

3.	­ A multiple­voltage EPS with a nameplate output rating of 203 W with 12 V and 5 V 

busses 

4.	­ A linear­regulated high power EPS with nameplate output rating of 345 W with a 13.8 V 

bus 

5.	­ A switching­regulated high power EPS with nameplate output rating of 345 W with a 

13.8 V bus 

Please describe the discrete design steps you would undertake to achieve the efficiency level and 

no­load power specification shown in the table below. In each case, start with a baseline SMPS, 

and list the necessary design changes to enable it to meet the higher efficiency levels. The 

efficiency levels are defined to be: 

Efficiency 

Level Descriptor Explanation 

0 Baseline, lowest cost A cheap, low­efficiency model 

1 Intermediate level A model with improved efficiency, but less than 

EISA 2007 

2 Exactly EISA 2007 A model that has efficiency just at the EISA 2007 

level 

3 EISA 2007 qualified A model that comfortably qualifies as EISA 2007 

4 Maximum commercially 

achieved 

The highest efficiency of the ENERGY STAR 

qualifying units (US EPA 2007) b 

5 Maximum technologically 

feasible 

The highest­efficiency model possible 

a “Efficiency” is used in this worksheet as a proxy for both conversion efficiency and no­load power. 

b Taken in 2007 from “Table 6­1 – Outstanding EPS in terms of average efficiency and no­load losses” from 

www.ecocharger.org/docs/BioConsortium_EuP_Lot7_Task%206.pdf 

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For each design change, please also provide an estimate of your incremental production cost over 

the baseline, as well as the total unit selling price to an OEM or distributor. In case it is not 

possible to list the increase in cost per design change, please specify the total bill­of­materials 

(BOM) cost increase for all the improvements. Finally, please describe your markup structure to 

make it clear how increases in production costs impact the total per­unit manufacturer’s selling 

price. 

We recognize that detailed designs may be difficult to prepare; therefore, in the interests of 

generating reasonable results in a short space of time, we invite you to use your best judgment 

and experience when completing the following tables. 

In addition, we believe that the output cord can be a significant source of loss for the external 

power supply. To address this, we consider efficiency at two points: at the output where the 

PCB connects to the output cord and at the end of the output cord. 

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Please use the following design specifications:
­

EPS 1: 18W MEDICAL EXTERNAL POWER SUPPLY 

Input voltage: 115 volts rms, 60 Hz Unit volume: 5,000 units per year 

Input protection: Primary current fuse, 

inrush current limiting Application: Medical diagnostic 

Output voltage 

regulation: ± 1% (excluding cord) Package: Sealed polycarbonate 

Output voltage ripple: 1% VP­P maximum Output cord 

length: 6 feet 

Transient response: 0.5 ms for 50% load 

change typical 

Regulatory 

compliance: UL 60601­1, FCC 

Output protection: Overcurrent protection, 

short­circuit protection Product lifetime: ~10 years 

EPS 2: 40W MULTIPLE VOLTAGE EXTERNAL POWER SUPPLY 

Input voltage: 115 volts rms, 60 Hz Unit volume: 1M units per year 

Input protection: Primary current fuse, 

inrush current limiting Application: Printer 

Output voltage 

regulation: ± 5% (excluding cord) Package: Sealed polycarbonate 

Output voltage ripple: 2% VP­P maximum Output cord 

length: 6 feet 

Transient response: 0.5 ms for 50% load 

change typical 

Regulatory 

compliance: UL, FCC 

Output protection: Overcurrent protection, 

short­circuit protection Product lifetime: 4 years 

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EPS 3: 203W MULTIPLE VOLTAGE EXTERNAL POWER SUPPLY 

Input voltage: 115 volts rms, 60 Hz Unit volume: 4M units per year 

Input protection: Primary current fuse, 

inrush current limiting Application: Video Game System 

Output voltage 

regulation: ± 1% (excluding cord) Package: Sealed polycarbonate 

Output voltage ripple: 1% VP­P maximum Output cord 

length: 6 feet 

Transient response: 0.5 ms for 50% load 

change typical 

Regulatory 

compliance: UL, FCC 

Output protection: Overcurrent protection, 

short­circuit protection Product lifetime: 4 years 

EPS 4 and EPS 5: 345W HIGH POWER EXTERNAL POWER SUPPLY 

Input voltage: 115 volts rms, 60 Hz Unit volume: ? units per year 

Input protection: Primary current fuse, 

inrush current limiting Application: Ham radio 

Output voltage 

regulation: ± 1% (excluding cord) Package: Sealed polycarbonate 

Output voltage ripple: 1% VP­P maximum Output cord 

length: 6 feet 

Transient response: 0.5 ms for 50% load 

change typical 

Regulatory 

compliance: UL, FCC 

Output protection: Overcurrent protection, 

short­circuit protection Product lifetime: 4(?) years 

Thank you for your input. If you have any questions or suggestions, please contact:
­

Matt Malinowski Michael Vladimer 

202­481­7304 202­481­7323 

Matt.Malinowski@NavigantConsulting.com MVladimer@NavigantConsulting.com 

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The table on this page provides an example of the kind of information we need in order to create 

a cost­efficiency curve for non­Class A EPSs. In this particular example, we show one set of 

improvements for increasing the efficiency of an 80%­efficient 75 W, 12 V Class A EPS to meet 

the requirements of the EISA 2007. This example is purely illustrative. However, this table 

does provide an indication of the level of detail being requested for the tables on the following 

pages. The column labeled “Incremental Unit Cost per Improvement” represents the cost of the 

specific improvement described. If additional rows are needed to describe all the design changes 

you would make, please feel free to modify the tables. The column labeled “Total Mfr. Unit 

Selling Price” is your final selling price to your customers, such as OEMs or distributors. 

Example: EPS 1: Class A EPS POUT = 75 W, VOUT = 12 V 

# Efficiency 

Level 

Conversion 

Efficiency NoLoad 

Power 

Defining Design 

Characteristics Mfr. Production Cost 

Total 

Mfr. 

Unit 

Selling 

Price 

Board 

Output 

EndofCord 

2­stage topology with ­ PFC 

$8 

UC3844 PWM controller ­

0 Baseline, 

lowest cost 74% 1 W E­type transformer ­

Output rectifier w/ 

Schottkies ­

Size: 4 in x 2.5 in x 1.5 ­ in 

# Efficiency 

Level 

Conversion 

Efficiency NoLoad 

Power 

Improvements over 

Baseline to Meet 

Efficiency Level 

Incremental Cost 

(over Baseline) per 

Improvement 

Total 

Mfr. 

Unit 

Selling 

Price 

Board 

Output 

EndofCord 

Variable­frequency 

PWM controller IC + $0.05 

Change in transformer + $0.20 

due to higher IC 

2 Exactly 

EISA 2007 85 % 0.5 W switching frequency $10 Additional filtering caps 

due to higher IC EMI 

+ $0.12 

Miscellaneous additional + $0.10 

components (e.g., 

XXXXX) 

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EPS 1: Medical Grade, POUT = 18 W, VOUT = 12 V 

Conversion 

# Efficiency 

Level 

Efficiencyc NoLoad 

Power 

Defining Design 

Characteristics 

Mfr. 

Production 

Cost 

Total Mfr. 

Unit Selling 

Price Board 

Output 

EndofCord 

0 Baseline: 

lowest­cost 65%d 1 W 

# Efficiency 

Level 

Conversion 

Efficiency NoLoad 

Power 

Improvements over 

Baseline to Meet 

Efficiency Level 

Incremental 

Cost (over 

Baseline) per 

Improvement 

Total Mfr. 

Unit Selling 

Price Board 

Output 

EndofCord 

1 Intermediate 70% 0.8 W 

2 

Exactly EISA 

2007 

76% 0.5 W 

3 

EISA 2007 

qualified 

78% 0.3 W 

4 

Maximum 

Commercially 

Achieved 

88% 0.15 W 

c Conversion efficiency, as defined by DOE, ENERGY STAR, and CEC test procedures, is the arithmetic mean of
­

efficiencies at 100%, 75%, 50%, and 25% of maximum rated output current.
­ d These are NCI’s straw­man estimates of efficiency values. We welcome your input on these values.
­

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5 

Maximum 

Technologically 

Feasible 

90% 0.10 W 

• How do you apply markups to your production costs in order to arrive at an OEM 

and distributor selling price? 

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EPS 2: Multiple­voltage EPS POUT = 40 W, V1 = 16 V @ 0.625 A, V2 = 32 V @ 0.940 A
­

Conversion 

# Efficiency 

Level 

Efficiencye NoLoad 

Power 

Defining Design 

Characteristics 

Mfr. 

Production 

Cost 

Total Mfr. 

Unit Selling 

Price Board 

Output 

EndofCord 

0 Baseline: 

lowest­cost 65%f 1.4 W 

# Efficiency 

Level 

Conversion 

Efficiency NoLoad 

Power 

Improvements over 

Baseline to Meet 

Efficiency Level 

Incremental 

Cost (over 

Baseline) per 

Improvement 

Total Mfr. 

Unit Selling 

Price Board 

Output 

EndofCord 

1 Intermediate 75% 1 W 

2 

Exactly EISA 

2007 

83.6% 0.5 W 

3 

EISA 2007 

qualified 

85% 0.45 W 

4 

Maximum 

Commercially 

Achieved 

89% 0.31 W 

e Conversion efficiency, as defined by DOE proposed multiple­voltage test procedure, is the arithmetic mean of
­

efficiencies at 100%, 75%, 50%, and 25% of simultaneous loading to maximum rated output current, adjusted for
­

derating and minimum output requirements.
­ f These are NCI’s straw­man estimates of efficiency values. We welcome your input on these values.
­

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 5 

Maximum 

Technologically 

Feasible 

90% 0.2 W 

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EPS 3: Multiple­voltage EPS POUT = 203 W, V1 = 12 V @ 16.5 A, V2 = 5 V @ 1 A
­

Conversion 

# Efficiency 

Level 

Efficiencyg NoLoad 

Power 

Defining Design 

Characteristics 

Mfr. 

Production 

Cost 

Total Mfr. 

Unit Selling 

Price Board 

Output 

EndofCord 

0 Baseline: 

lowest­cost 80%h 1.4 W 

# Efficiency 

Level 

Conversion 

Efficiency NoLoad 

Power 

Improvements over 

Baseline to Meet 

Efficiency Level 

Incremental 

Cost (over 

Baseline) per 

Improvement 

Total Mfr. 

Unit Selling 

Price Board 

Output 

EndofCord 

1 Intermediate 82% 1 W 

2 

Exactly EISA 

2007 

85% 0.5 W 

3 

EISA 2007 

qualified 

86.5% 0.45 W 

4 

Maximumi 

Commercially 

Achieved 

89% 0.3 W 

g Conversion efficiency, as defined by DOE proposed multiple­voltage test procedure, is the arithmetic mean of 

efficiencies at 100%, 75%, 50%, and 25% of simultaneous loading to maximum rated output current, adjusted for 

derating and minimum output requirements. 

h These are Navigant Consulting’s straw­man estimates of efficiency values. We welcome your input on these 

values. 

i These values have not been commercially achieved for multiple­voltage EPSs. We welcome your input on these 

values. 

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 5 

Maximum 

Technologically 

Feasible 

91% 0.3 W 

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EPS 4: High Power EPS (Linear­Regulated) POUT = 345 W, V1 = 13.8 V @ 25 A
­

# Efficiency 

Level 

Conversion 

Efficiencyj NoLoad 

Power 

Defining Design 

Characteristics 

Mfr. 

Production 

Cost 

Total Mfr. 

Unit Selling 

Price Board 

Output 

EndofCord 

0 Baseline: 

lowest­cost 55%k 18 W 

# Efficiency 

Level 

Conversion 

Efficiency NoLoad 

Power 

Improvements over 

Baseline to Meet 

Efficiency Level 

Incremental 

Cost (over 

Baseline) per 

Improvement 

Total Mfr. 

Unit Selling 

Price Board 

Output 

EndofCord 

1 Intermediate 1l 62% 15 W 

2 Intermediate 2 75 % 12 W 

3 Exactly EISA 

2007 

85% 8 W 

j Conversion efficiency, as defined by DOE proposed multiple­voltage test procedure, is the arithmetic mean of
­

efficiencies at 100%, 75%, 50%, and 25% of simultaneous loading to maximum rated output current, adjusted for
­

derating and minimum output requirements.
­ k These are NCI’s straw­man estimates of efficiency values. We welcome your input on these values.
­ l This level corresponds to data points measured by Navigant Consulting.
­

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EPS 5: High Power EPS (Switched­mode) POUT = 345 W, V1 = 13.8 V @ 25 A
­

# Efficiency 

Level 

Conversion 

Efficiencym NoLoad 

Power 

Defining Design 

Characteristics 

Mfr. 

Production 

Cost 

Total Mfr. 

Unit Selling 

Price Board 

Output 

EndofCord 

0 Baseline: 

lowest­cost 80%n 10 W 

# Efficiency 

Level 

Conversion 

Efficiency NoLoad 

Power 

Improvements over 

Baseline to Meet 

Efficiency Level 

Incremental 

Cost (over 

Baseline) per 

Improvement 

Total Mfr. 

Unit Selling 

Price Board 

Output 

EndofCord 

1 Intermediateo 81% 6 W 

2 

Exactly EISA 

2007 

85% 0.5 W 

3 

EISA 2007 

qualified 

86% 0.45 W 

4 

Maximum 

Commercially 

Achieved 

90% 0.3 W 

m Conversion efficiency, as defined by DOE proposed multiple­voltage test procedure, is the arithmetic mean of
­

efficiencies at 100%, 75%, 50%, and 25% of simultaneous loading to maximum rated output current, adjusted for
­

derating and minimum output requirements.
­ n These are NCI’s straw­man estimates of efficiency values. We welcome your input on these values.
­ o This level corresponds to data points measured by Navigant Consulting. 

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 5 

Maximum 

Technologically 

Feasible 

93% 0.2 W 

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