5

- i CHAPTER 5
. ENGINEERING ANALYSIS

TABLE OF CO NTENTS
5.1 INTRODUCTION

................................ ................................ ................................ ........... 5

- 1 5.2 PRODUCT CLASSES ANAL YZED

................................ ................................ .............. 5

- 1 5. 3 EFFICIENCY LEVELS

................................ ................................ ................................ ... 5

- 2 5.3.1 Baseline Units

................................ ................................ ................................ .................. 5

- 2 5.3.2 Incremental Standby Power Levels

................................ ................................ ................. 5

- 3 5.4 METHODOLOGY OVERVIEW

................................ ................................ .................... 5

- 5 5.4.1 AHAM Data Submittal

................................ ................................ ................................ .... 5

- 6 5.4.2 Manufacturer Interviews

................................ ................................ ................................ .. 5

- 6 5. 4.3 Product Teardowns

................................ ................................ ................................ .......... 5

- 6 5.4.3.1 Selection of Units

................................ ................................ ........................... 5

- 7 5.4.3.2 Generation of Bill of Materials

................................ ................................ ...... 5

- 7 5.4.3.3 Cost Structure of the Spreadsheet Models

................................ ..................... 5

- 8 5.4.4 Product Testing

................................ ................................ ................................ ................ 5

- 9 5.5 ANALYSIS AND RESULTS

................................ ................................ .......................... 5

- 9 5.5.1.1 AHAM Data

................................ ................................ ................................ ... 5

- 9 5.5.1.2 Produc t Testing and Teardowns

................................ ................................ ... 5

- 11

LIST OF TABLES
Table 5.3.1 Standby Power Levels for Microwave

- Only Ovens and Countertop Combination Microwave Ovens

................................ ................................ .......... 5

- 4 Table 5.3.2 Standby Power Levels for Built

- In and Over

- the

- Range Combination Microwave Ovens

................................ ................................ ................................ 5

- 5 Table 5.4.1 Engineering Analysis Methods

................................ ................................ ............ 5

- 6 Table 5.4.2 Major Manufacturing Processes

................................ ................................ .......... 5

- 8 Table 5.5.1 Microwave Oven Standby Power Comparison

................................ .................. 5

- 11 Table 5.5 .2 Microwave

- Only Oven Features (Table 1 of 4)

................................ ................. 5

- 13 Table 5.5.3 Microwave

- Only Oven Features (Table 2 of 4)

................................ ................. 5

- 14 Table 5.5.4 Microwave

- Only Oven Features (Table 3 of 4)

................................ ................. 5

- 14 Table 5.5.5 Microwave

- Only Oven Features (Table 4 of 4)

................................ ................. 5

- 14 Table 5.5.6 DOE Microwave

- Only Oven Standby Power (Table 1 of 4)

............................. 5

- 15 Table 5.5.7 DOE Microwave

- Only Oven Standby Power (Table 2 of 4)

............................. 5

- 16 Table 5.5.8 DOE Microwave

- Only Oven Standby Power (Table 3 of 4)

............................. 5

- 16 Table 5.5.9 DOE Microwave

- Only Oven Standby Power (Table 4 of 4)

............................. 5

- 16 Table 5.5.10 DOE Standby Power Requirements among Similar Microwave

- Only Ovens with Different Options

................................ ................................ ............ 5

- 24 Table 5.5.11 Incremental Manufacturing Costs for Microwave

- Only Oven and Countertop Combination Microwave Oven Standby Power

............................. 5

- 265

- ii Table 5.5.12 DOE Countertop Combination Microwave Oven Standby Power

.................... 5

- 27 Table 5.5.13 Control Power Supply Transformer Standby Power Test Results

..................... 5

- 29 Table 5.5.14 DOE Built

- In and Over

- the

- Range Combination Microwave Oven Standby Power

................................ ................................ ................................ ... 5

- 29 Table 5.5.15 DOE Built

- In and Over

- the

- Range Combination Microwave Oven Disaggregated Components Standby Power Consumption

............................... 5

- 31 Table 5.5.16 Built

- In and Over

- the

- Range Combination Microwave Oven Incremental Manufacturing Costs

................................ ................................ .......................... 5

- 32

LIST OF FIGURE S Figure 5.4.1 Manufacturing Cost Assessment Stages

................................ .............................. 5

- 8 Figure 5.5.1 AHAM Microwave Oven Standby Power

................................ ......................... 5

- 10 Figure 5.5.2 DOE Microwave

- Only Oven Standby Power Consumption as a Function of Rated Output Power

................................ ................................ ....................... 5

- 18 Figure 5.5 .3 AHAM Microwave Oven Standby Power Consumption as a Function of Rated Output Power

................................ ................................ ........................... 5

- 19 Figure 5.5.4 DOE Microwave

- Only Oven Stand by Power Consumption as a Function of Display Size

................................ ................................ ................................ ... 5

- 20 Figure 5.5.5 DOE Standby Power Consumption as a Function of Display Size for Microwave

- Only Ovens with LED Displays

................................ ..................... 5

- 21 Figure 5.5.6 DOE Standby Power Consumption as a Function of Display Size for Microwave

- Only Ovens with VFD Displays

................................ ..................... 5

- 22 Figure 5.5.7 DOE Standby Power Consumption as a Function of Display Size for Microwave

- Only Ovens with LCD Displays

................................ ..................... 5

- 23 Figure 5.5.8 DOE Standby Power Consumption Associated with Different Design Options

................................ ................................ ................................ ............... 5

- 25 Figure 5.5.9 DOE Standby Power Consumption as a Function of Display Size for Countertop Combination Microwave Ovens

................................ ..................... 5

- 28 Figure 5.5.10 DOE Standby Power Consumption as a Function of Display Size for Built

- In and Over

- the

- Range Combination Microwave Ovens

......................... 5

- 305-1 CHAPTER 5. ENGINEERING ANALYSIS

5.1 INTRODUCTION After conducting the screening analysis, the U.S. Department of Energy (DOE) performed an engineering analysis based on the remaining design options

. The engineering analysis consists of estimating the standby energy consumption and costs of products at various levels of increased efficiency

. This section provides an overview of th e engineering analysis (section 5.1 ), discusses proposed product classes (section 5.2 ), establishes baseline unit specification s (section 5.3.1 ), discusses incremental efficiency levels (section 5.3.2 ), explains the methodology used during data gathering ( 5.4 ) and discusses the analysis and results (section 5.5 ) The primary inputs to the engineering analysis are baseline information from the market and techno logy assessment ( c hapter 3 of the technical support document ( TSD ) ) and technology options from the screening analysis ( c hapter 4

. ) Additional inputs include laboratory testing and
reverse - engineering of representative microwave ovens

. The primary output of the engineering analysis is a set of cost

- efficiency curves

. In the subsequent markups analysis ( c hapter 6 ), DOE determined customer ( i.e. , product purchaser) prices by applying distribution markups, sales tax and contractor markups

. After applying thes e markups, they serve as the input to the building energy - use and end

- use load characterization ( c hapter 7 ) and the life

- cycle cost (LCC) and payback period (PBP) analyses ( c hapter 8). DOE typically structures its engineering analysis around one of three m ethodologies

. These are: (1) the design

- option approach, which calculates the incremental costs of adding specific design options to a baseline model that will improve its efficiency ( i.e. , lower its energy use in standby mode and off mode) ; (2) the efficiency

- level approach, which calculates the relative costs of achieving increases in energy efficiency levels ( in this case , levels of reduced standby power) , without regard to the particular design options used to achieve such increases; and /or (3) the reverse engineering or cost

- assessment approach, which involves a “bottom

- up” manufacturing cost assessment based on a detailed bill of materials (BOM) derived from teardowns of the product being analyzed

. Deciding which methodology to use for the engineering analysis depends on the product, the design options under study, and any historical data that DOE can draw on.

5.2 PRODUCT CLASSES ANAL YZED DOE separated residential microwave ovens into product classes

. Because DOE formulated a separate energy conservation standard for standby power consumption for each product class, the criteria for separation into different classes are (1) type of energy used (natural gas or electricity), and (2) capacity or other performance

- related features such as those t hat provide utility to the consumer, or others deemed appropriate by the Secretary that would justify the establishment of a separate energy conservation standard

. (42 U.S.C

. 6295 (q))5-2 For the reasons discussed in chapter 3 of this TSD , DOE has analyzed for the purposes of this supplemental notice of proposed rulemaking (SNOPR) the following two product classes for microwave ovens:

**•** Microwave

- only ovens and countertop combination microwave ovens

**•** Built

- in and over

- the

- range combination microwave ovens

5.3 EFF ICIENCY LEVELS

5.3.1 Baseline Units DOE selected baseline units as reference points for each product class, against which DOE measured changes resulting from energy conservation standards

. The baseline unit in each product class represents the basic characterist ics of equipment in that class

. Typically, a baseline unit is a unit that just meets current required energy conservation standards and provides basic consumer utility

. DOE used the baseline units in the engineering analysis and the life

- cycle

- cost and payback

- period analysis

. To determine energy savings and changes in price, DOE compared each higher energy efficiency design option with the baseline unit

. The identification of baseline units required establishing the baseline standby power level

. For mi crowave oven standby power , energy conservation standard levels are expressed as a maximum s tandby power consumption, in w atts (W)

. As discussed in chapter 3 of this TSD, DOE is not aware of any current microwave ovens that are capable of operation in off mode. As a result, the standards do not include off mode power

. Based on product testing (see section 5.6.1.3 ) , DOE selected a baseline standby power level which was the highest typical standby power for a microwave oven to provide full consumer utility fo r each product class

. For the purpose of this rulemaking , DOE determined consume r utility to be the ability to display complex characters, brightness , and viewing angle of the display as well as the ability to automatically control the cooking operation ( i.e. , through the use of a n absolute humidity cooking sensor)

. For the built

- in and over

- the

- range combination microwave ovens product class, consumer utility also included a sufficiently sized power supply capable of operating additional features required to handle the thermal loads associated with their installation and to provide consumer utility, such as additional exhaust fan motors, convection fan motors and heaters, and additional lights. For both product classes, the baseline power supply used a
con ventional linear power supply with an efficiency of approximately 55 percent. DOE selected
a baseline standby power level of 4.0 W for the microwave

- only oven s and countertop combination microwave ovens product class

. For the built

- in and over

- the

- range co mbination microwave ovens product class, DOE selected a baseline standby power level of 4.5 W. As discussed in section 5.5.1.2 , DOE noted that the built

- in combinat ion microwave ovens in its test sample consumed more standby power than the over

- the

- range combination microwave ovens.5-3 However, DOE notes that built

- in and over

- the

- range combination microwave ovens have essentially the same features ( i.e. , exhaust fans a nd convection heaters). DOE also noted that the two built

- in combination microwave ovens in its test sample were high

- end units with large displays and a larger number of cooking settings and options. As a result, DOE believes that the standby power level of 4.5 W for the built

- in and over

- the

- range combination microwave ovens product class provides full consumer utility and that the higher levels observed in DOE’s test sample for built

- in combination microwave ovens are not appropriate for establishing the baseline standby power levels.

5.3.2 Incremental Standby Power Levels For the product classes presented in section 5.2 , DOE analyzed several standby power levels and obtained incremental cost data at each of these levels

. Table 5.3

. 1 and Table 5.3

. 2 provide standby power levels and the reference source of each level. DOE conducted the engineering analysis for microwave oven standby power for the two product class es DOE identified for microwave ovens

. To analyze the cost

- energy use relationship for microwave oven standby power , DOE defined standby power levels expressed as a maximum average standby power, in W

. For the reasons noted above in section 5.3.1 , the standard levels do not include off mode power.
For the microwave

- only ovens and countertop combination microwave ovens product class, t he standby power levels were derived from review of the Federal Energy Management Program (F EMP ) procur ement efficiency recommendation , the International Energy Agency’s (IEA) One

- Watt program to lower standby power consumption below 1 W for various electrica l appliances , and the current maximum microwave oven standby technology ( i.e. lowest standby power ) that DOE believes is or could be commercially available at the time the energy conservation standards become effective. T he max

- tech microwave

- only oven and countertop combination microwave oven standby power level of 0.02 W corresponds to a unit equipped with a default automatic power

- down function that shuts off certain power

- consuming components after a specified period of user inactivity. The standby power at max

- tech was obtained from a microwave oven currently on the mar ket in Korea which incorporates such a feature. DOE also added a standby power level as a gap

- fill between the FEMP Procurement Efficiency Recommendation and IEA One

- Watt Program levels

. Table 5.3

. 1 provide s the microwave

- only ovens and countertop combination microwave ovens product class standby power levels and the reference source for each level that DOE has analyzed

.5-4 Table 5.3
. 1 Standby Power Levels for Microwave

- Only Ovens and Countertop Combination Microwave Ovens

Standby Power Level Standby Power Level Source Standby Power (W) Baseline Baseline 4.0 1 FEMP Procurement Efficiency Recommendation 2.0 2 Gap Fill 1.5 3 IEA 1

- Watt Program 1.0 4 Max

- Tech 0.02
For the built

- in and over

- the

- range combination microwave oven product class , the standby power levels were determined based on reverse

- engineering analyses on a representative sample of built

- in and over

- the

- range combination microwave ovens to analyze the various components that contribute to the standby power consumption of the u nit. DOE also measure d the standby power consumed by these components individually. In its analysis , DOE observed that the absolute humidity cooking sensor used in these combination microwave ovens on average consume 0.9 W of standby power. For standby power l evel 1, DOE believes that standby power can be reduced by incorporating a zero

- standby cooking sensor. For standby power l evel 2, DOE analyzed potential improvements to the power supply design . DOE noted that microwave ovens at the baseline standby energy use incorporate a linear power supply. DOE measured the standby power consumption of the power supply and found that the transformer used to step down the line input voltage contributes most significantly to the standby power consumption. DOE then performed a power budget analysis to determine the size of the transformer needed to operate a microwav e at full load, and the results suggest that replacing the conventional linear power supply with a more efficient switch mode power supply will eliminate the need for a large transformer and effectively reduce the standby power associated with the power su pply. DOE thus estimated the standby power for standby power l evel 2 based on the improvement associated with changing from a conventional linear power supply with an efficiency of 55 percent to a switch mode power supply with an efficiency of 75 percent. DOE developed this estimate for the efficiency of a switch mode power supply based on research of such power supply designs for appliance applications. a

a Information on the design and efficiency of switch mode power supplies can be found at For standby power l evel 3, DOE analyzed the impact relays have in determining the size of a power suppl y. DOE compared the power budget of a control board with electromechanical relays to that with solid state relays, and observed that the power requirement of a control board, with similar input and load, is lower with solid state relays than with electrome chanical relays. Therefore, DOE estimated the standby power at standby power l evel 3 based on design improvements associated with using more efficient components in a switch mode power supply that incorporates solid state relays. For standby power l evel 4, DOE analyzed an automatic function that turns off power to standby power consuming components after a certain period of inactivity and that uses a transformerless power supply to maintain the microcontroller chip while the microwave oven is not powered on

.

http://www.powerint.com/en/applications/major

- appliances

.5-5 DOE estimated the standby power at standby power l evel 4 based on the standby power requirements of the controller microcontroller chip.
Table 5.3

. 2 presents the proposed standby power levels for built

- in and over

- the

- range combination microwave ovens.
Table 5.3
. 2 Standby Power Levels for Built

- In and Over

- the

- Range Combination Microwave Ovens

Standby Level Standb y Power Level Source Standby Power (W) Baseline Baseline 4. 5 1 Zero W Cooking Sensor 3.7 2 Switch Mode Power Supply 2.7 3 Improved Relay Power Supply Design 2.2 4 Max

- Tech (Automatic Power Down) 0.04

5.4 METHODOLOGY OVERVIEW In order to develop the cost

- efficiency relationships f or microwave ovens , DOE performed detailed product teardowns and reverse

- engineering analyses on a sample of product models spanning a range of standby power levels and product features

. DOE also conducted detailed standby po wer testing to gain insights into energy performance in standby mode and to evaluate individual components contributing to standby power consumption. AHAM also submitted data to DOE on standby power testing that it conducted

. DOE supplemented this informat ion by conducting interviews with manufacturers of microwave ovens. Table 5.4

. 1 below shows which methods DOE used for each product class

.5-6 Table 5.4
. 1 Engineering Analysis Methods

Method Microwave

- Only Ovens and Countertop Combination Microwave Ovens Built

- In and Over

- the

Range Combination

Microwave Ovens AHAM Data √ Product Teardown √ √ Product Testing √ √ Manufacturer Interviews √

5.4.1 AHAM Data Submittal
In support of this rulemaking effort, AHAM submitted data regarding standby power in microwave ovens. The AHAM submittal contained general descriptions of components related to standby power as well as data from standby power testing. The data provided to DOE by AHAM are contained in a ppendix 5 A.

5.4.2 Manufacturer Interviews
DOE conducted confidential interviews with microwave ovens manufacturers to develop a deeper understanding of the various combinations of technologies used to reduce standby power consumption , and their associated manufacturing costs

. Sample questions asked during the follow

- up interviews , which were also conducted in support of the manuf acturer impact analysis, are contained in a ppendix 12 B

. During the interviews, DOE also gathered information about the capital expenditures required to reduce the standby power consumption of the baseline units to various standby power levels ( i.e. , conversion capital expenditures by standby power level)

. The interviews provided information about the size and the nature of the capital investments

. DOE also requested information about the depreciation method used to expense the conversion capital.

5.4.3 Pr oduct Teardowns Other than obtaining detailed manufacturing costs directly from a manufacturer, the most accurate method for determining the production cost of a piece of equipment is to disassemble the equipment piece

- by

- piece and estimate the material an d labor cost of each component using a process commonly called a physical teardown

. A supplementary method, called a catalog teardown, uses published manufacturer catalogs and supplementary component data to estimate the major physical differences between a piece of equipment that has been physically disassembled and another piece of similar equipment

. DOE performed physical teardown analysis on microwave ovens for this rulemaking

. The teardown methodology is described in detail in section 5.5.3.1 through section 5.5.3.3

.5-7 5.4.3.1 Selection of Units During the process of selecting units for teardown, DOE consider s three main questions:

 What standby power levels should be captured in the teardown analysis?

 Are there un its on the market that capture all potential standby power levels and design options?

 Which of the available units are most representative? In responding to the preceding questions, DOE adopt s the following criteria for selecting units for the teardown ana lysis:

 T he selected products should span the full range of standby power levels for each product class under consideration;

 W ithin each product class, if possible, the selected products should come from the same manufacturer and be within the same product series;

 T he selected products should primarily come from manufacturer s with large market share in that product class, although the highest efficiency products were chosen irrespective of manufacturer; and

 T he selected products should have non - standby power

- related features that are the same as, or similar to, features of other products in the same class and at the same standby power level

.
5.4.3.2 Generation of Bill of Materials
The end result of each teardown is typically a structured bill of materials (BOM)

. The process is discussed here in the context of the general methodology used for teardown analysis, although it should be noted a more limited approach was used for microwave ovens due to the substantial uniformity in design and construction among the sample u nits

. Structured BOMs describe each equipment part and its relationship to the other parts, in the estimated order of assembly

. The BOMs describe each fabrication and assembly operation in detail, including the type of equipment needed ( e.g. , stamping pres ses, injection molding machines, spot

- welders, etc.) and the process cycle times

. The result is a thorough and explicit model of the production process
. The BOMs incorporate all materials, components, and fasteners , classified as either raw materials or p urchased parts and assemblies

. The classification into raw materials or purchased parts is based on DOE’s previous industry experience, recent information in trade publications, and discussions with high

- and low

- volume original equipment manufacturers (OE Ms). For purchased parts, the purchase price is an estimate based on volume

- variable price quotations and detailed discussions with suppliers

. For fabricated parts, the price of intermediate materials ( e.g. , tube, sheet metal) and the cost of transforming them into finished parts are an estimate based on current industry pricing.5-8 The cost of raw materials is determined using prices for copper, steel and aluminum from the American Metals Market. 1

5.4.3.3 Cost Structure of the Spreadsheet Models The price of steel drastically increased in 2005, and the price of copper has increased steadily since 2004

. Because DOE is using a 5

- year average in material prices from 200 5

– 200 9 , these price increases are normalized, which better represents long

- term material prices.

The manufacturing cost assessment methodology used is a detailed, component

- focused technique for rigorously calculating the manufacturing cost of a product (direct materials, direct labor and some overhead costs

. ) Figure 5.4

. 1 shows the three major steps in generating the manufacturing cost.

Figure 5.4
. 1 Ma nufacturing Cost Assessment Stages The first step in the manufacturing cost assessment is the creation of a complete and structured BOM from the disassembly of the units selected for teardown

. The units are dismantled, and each part is characterized accord ing to weight, manufacturing processes used, dimensions, material , and quantity

. The BOM incorporates all materials, components, and fasteners with estimates of raw material costs and purchased part costs

. Assumptions on the sourcing of parts and in

- house fabrication are based on industry experience, information in trade publications , and discussions with manufacturers

. Interviews and plant visits are also conducted with manufacturers to ensure accuracy on methodology and pricing. Following the development of a detailed BOM, the major manufacturing processes are identified and developed for the spreadsheet model

. These processes are listed in Table 5.4

. 2

. Table 5.4
. 2 Major Manufacturing Processes

Fabrication Finishing Assembly/Joining Quality Control Fixturing Washing Adhesive Bonding Inspecting & Testing Stamping/Pressing Powder Coating Spot Welding Brake Forming De

- burring Seam Welding Cut ting and Shearing Polishing Insulating Fabrication process cycle times are estimated and entered into the BOM

. For this analysis, $24.00 per hour was used as the average fully

- burdened labor rate based on typical annual wages and benefits of industry employees

. In the final step of the cost assessment,5-9 assembly times and associated direct labor costs are estimated

. Once the cost estimate for each teardown unit is finalized, a de tailed summary is prepared for relevant components, subassemblies and processes

. The BOM thus details all aspects of unit costs

. Design options used in units subject to teardown are noted in the summary sheet of each cost model and are cost

- estimated indi vidually

. Thus, various implementations of design options can be accommodated, ranging from assemblies that are entirely purchased to units that are made entirely from raw materials

. Hybrid assemblies, consisting of purchased parts and parts made on site a re thus also accommodated

.
5.4.4 Product Testing DOE conducted product testing on microwave ovens to develop a better understanding of the potential standby power improvements associated with various design options. As part of this testing, DOE measured the power consumption of components contributing to standby power individually to further evaluate the strategies manufacturers may take to reduce standby power

.

5.5 ANALYSIS AND RESULTS

5.5.1.1 AHAM Data AHAM provided data on mic rowave oven standby power for a sample of microwave
ovens currently available in the U.S. market. 2 Figure 5.5

. 1 Standby power was tested in accordance with the International Electrotechnical Commission ( IEC ) Standard 62301

- 2005, Household electrical appliances

– Measu rement of standby power (IEC Standard 62301 ( First Edition ) )

. displays AHAM

- measured microwave oven standby power data as a function of rated cooking output power

. Unlike efficiency, these data show a wide range of standby power, but there is no correlation between standby power and cooking output power

. Standby power ranged from 1.5 to 5.8 W , with 9 of the 21 m icrowave ovens meeting the FEMP recommendation of 2.0 W or less

. The average standby power measured was 2.9 W

. AHAM did not provide any information with which DOE could correlate standby power with other features such as cooking sensors or displays

. The da ta did not indicate the product type ( i.e. , microwave only, combination) or the installation configuration ( i.e. , countertop, over

- the

- range, built

- in).
DOE notes that m icrowave oven standby power consumption is impacted significantly by the digital clock display, with more complex graphical displays drawing more power

. According to AHAM, the three major types of displays used in microwave ovens are (1) LED displays, (2) VFDs, and (3) LCDs

. Typically, LCDs without back

- lighting use the least amount of ener gy while VFDs use the most

. Energy consumed by LCDs would depend on whether back

- lighting is present or not, and if present, the number of LEDs used for back

- lighting

. For LED displays, the number of segments, color, and operating temperature affect energy consumption

. The size of the display (number of digits and icons) also affects the energy consumed by the display

. For VFDs, the size of the display is a major factor in energy consumption. 3 Standby power consumption5-10 may also be affected by the electroni c controls required for features such as cooking sensors , along with associated power supplies

.

Figure 5.5
. 1 AHAM Microwave Oven Standby Power 4
Table 5.5

. 1 compares the AHAM

- measured microwave oven standby power data with data from other studies t hat have examined standby power in the United States and Canada

. It can be seen that average standby power has remained relatively constant since 1997 even though minimum and maximum levels have varied by a greater amount

. 0.0 1.0 2.0 3.0 4.0 5.0 6.0 7.0

600 700 800 900 1000 1100 1200 1300 1400 Rated Output Power (W)Standby Power (W)5-11 Table 5.5
. 1 Microwave Oven Standby Power Comparison

Source Microwave Oven Standby Power

Min ( W ) Average ( W ) Max ( W ) Std Dev ( W ) # Samples AHAM 2006 5 1.5 2.9 5.8 0.8 21 CBEEDAC 2006 6 0.4 1.9 3.3 0.8 19 CREEDAC 2001 (New Stock) 7 0.8 3.8 12.6

- 4 CREEDAC 2001 (Existing Stock) 8 0.0 2.1 7.3

- 64 LBNL 2008 9 1.4 3.1 4.9

- 18 Florida Solar Energy Center 1998 10

- 3.0

- - 25 LBNL 1997 11

- 3.1

- - - DOE recognize s that annual energy consumption can be significantly affected by standby power in real

- world usage

. For example, a 1

- W increase in standby power corresponds to an increase of 8.76 kilowatt

- hours ( kWh ) in annual energy consumption

. Prior to it being repeale d in a final rule published on July 22, 2010 ( 75 FR 42579), t he microwave oven test procedure
assume d an annual useful cooking energy output of 79.8 kWh

. For a baseline microwave oven that operates at 55.7 percent efficiency, annual energy consumption not including standby power would be 143.3 kWh

. Therefore each W of standby power included in the annual energy consumption metric would increase it by 6 percent for a baseline microwave oven

. Since the highest measured standby power was 5.8 W , the increment of 3.8 W over the FEMP

recommended level of 2.0 W would represent a 23

- percent increase in annual energy consumption for a baseline microwave oven.

5.5.1.2 Product Testing and Teardowns
Microwave

- Only Oven s and Countertop Combination Microwave Ove ns Section 310 of the Energy Independence and Security Act of 200 7 ( EISA 2007 ) (Pub. L. No. 110

- 140) amends Section 325 of the EPCA to require DOE to incorporate standby mode and off mode energy use into a single amended or new standard, if feasible, for covered products, including microwave ovens, for any final rule establishing or revising a standard adopted after July 1, 2010

. If such a single standard is not feasible, DOE shall prescribe a separate standard for standby mode and off mode energy consump tion, if justified

. (42 U.S.C. 6295(gg)(3)) As discussed in chapter 3 of this TSD, DOE published a final rule on July 22, 2010 repealing the provisions in the existing microwave oven test procedure relating to the measurement of cooking efficiency and ener gy factor (EF). 75 FR 42579. DOE notes that the absence of active mode testing provisions in the microwave oven test procedure results in a de facto separate energy use descriptor for microwave oven standby mode and off mode energy use. Therefore, DOE cond ucted microwave oven standby power testing to supplement the AHAM

- supplied data , investigate d design options , and develop ed a relationship between incremental manufacturing cost and standby power levels.5-12 As discussed in chapter 3 of this TSD, i n the Ma r ch 2011 TP Interim Final Rule , DOE adopted definitions of standby, off, and active mode based on the provisions in IEC Standard 62301 Second Edition , Final Draft International Standard (IEC Standard 62301 FDIS )

. 76 FR 12825, 12834

– 37 (Mar

. 9, 2011) . DOE defines “standby mode” as the condition in which an energy - using product is connected to a mains power source and offers one or more of the following user oriented or protective functions which may persist for an indefinite time

– (I) a remote switch (in cluding a remote control), internal sensor, or timer to facilitate the activation of other modes (including activation or deactivation of active mode) ; and (II) c ontinuous functions, including information or status displays (including clocks) or
sensor - ba sed functions. 76 FR 12825, 12836 (Mar. 9, 2011)

. DOE defines “off mode” as the condition in which an energy

- using product is connected to a mains power source , is not providing any active or standby mode function, and may persist for an indefinite time

. Off mode would also include an indicator that shows the user only that the product is in the off position. Id

. DOE defines “active mode,” as the condition in which an energy

- using product is connected to a main power source , has been activated , and provi des 1 or more main functions. Delay start mode is a one off user initiated short duration function that is associated with an active mode

. Id

. DOE considers “main functions” for a microwave oven to be those operations in which the magnetron and/or thermal element is energized for at least a portion of the time for purposes of heating, cooking, and/or defrosting the load

. According to the se definitions, standby mode would thus comprise the conditions in which the microwave oven is plugged in and consuming power for features including displays, cooking sensors, and sensors to reactivate the microwave oven from a low

- power state after a period of user inactivity

. For reasons discussed later in this section, DOE does not believe that any microwave ovens curren tly for sale in the United States are capable of operation in off mode.
General Microwave Oven Construction
All microwave

- only ovens examined by DOE contain a metal cavity that is mechanically attached to the front and rear chassis frames . Each of these p ieces had been formed by stamp ing, joined, and then the assembly is painted . To this frame, a bottom panel is attached. This bottom panel covers the turntable motor and also acts as an electrical ground for the magnetron power supply and the magnetron. The inner cavity occupies, on average, about 70 percent of the width and height of the microwave oven. The remaining space is used for cooling channels, the magnetron, the magnetron power supply, the cooling fan, the microwave oven controller, and other misce llaneous components.
All of the microwave

- only ovens examined have a door that is hinged on the left side of the unit. Beneath the right edge of the door, a latch mechanism with three switches ensures that the microwave oven cannot operate its magnetron w ithout the door being closed. To the right of the door, the user interface frame typically features a foil

- based button array under a flexible5-13 plastic cover, along with the display

. The display may be either attached directly to the user interface frame or integrated into the main control board for the microwave oven. The main control board typically consists of a single

- sided printed circuit board ( PCB ) which features a small alternating current to direct current ( AC

- DC ) power supply, several relays, and c ontrol logic . All power coming into the microwave oven is filtered through a separate power filtration board to which the power cord is attached. In addition to the aforementioned components, microwave

- only ovens contain a magnetron power supply featuring a microwave oven transformer, a high voltage diode, and a high

- voltage aluminum electrolytic capacitor. A single

- speed fan keeps the magnetron and microwave oven transformer cool during operation, while a turntable may rotate the food load inside the cavi ty while the microwave oven is operating. A single incandescent light bulb (20 W and higher) typically provides cavity illumination during operation and when the door is open. More sophisticated microwave ovens may contain cooking sensors, larger and multi

- colored displays with more complex graphics, and/or inverter

- based magnetron power supplies.
Test Units
DOE conducted standby power testing and reverse engineering analyses on a representative sample of 32 microwave

- only ovens. DOE noted key parameters for each test unit, presented in Table 5.5

. 2 through Table 5.5.5

. Since manufacturers are not required to report standby power for microwave ovens, DOE could not select its sample test units on the basis of standby power consumption. Instead, DOE selected its sample microwave ovens to cover a wide range of cavity sizes and output power, as well as other features such as display type, power supply type, and presence of cooking sensors. DOE was unable to identify any microwave oven models with an automatic powerdown feature. Within the test sample, DOE observed significant standby power differences which it believes are attributable to specific design options or design option combinations.
Table 5.5
. 2 Microwave

- Only Oven Features (Table 1 of 4) DOE1 DOE2 DOE3 DOE4 DOE5 DOE6 DOE7 DOE8

700 700 700 700 800 800 800 800 0.7 0.7 0.7 0.7 1 1 0.8 0.8

- - - - Y

- - -

- - - - - - - - Type LED LED LED LED VFD LED LCD LCD Characters #, 1 x 4 #, 1 x 4 #, 1 x 4 #, 1 x 4 A, 1 x 7 #, 1 x 4 #, 1 x 4 #, 1 x 4 # of LEDs for backlighting N/A N/A N/A N/A N/A N/A None None Size 1.50" x 0.43" 1.50" x 0.43" 1.45" x 0.70" 1.90" x 0.83" 2.25" x 0.75" 1.50" x 0.80" 1.87" x 0.83" 1.87" x 0.83"

- - - - - DOE5

- - DOE Unit Number Rated Output Power (W) Stated Volume (ft 3 ) Cooking Sensor Inverter Power Supply

Unit is Similar toDisplay5-14 Table 5.5
. 3 Microwave

- Only Oven Features (Table 2 of 4)

Table 5.5
. 4 Microwave

- Only Oven Features (Table 3 of 4)

Table 5.5
. 5 Microwave

- Only Oven Features (Table 4 of 4)

Three different display technologies were observed to be incorporated in the sample units: 1) LED; 2) LCD; and 3) VFD. The display format for each microwave oven was characterized as either numeric (#), alphanumeric (A), or dot matrix (D). Whereas numeric displays can only show time, alphanumeric displays can also display letters (though usually in simplified format). Dot matrix displays can show various fonts, letters, and symbols via matrices of pixels, making them the most flexible display technology. Si nce display power consumption is a function of not only the type of technology used but the overall size and number of digits in the display as well, the dimensions of each display were measured and the number of rows and columns of digits were recorded. F inally, some LCDs use LEDs for backlighting, allowing a microwave oven user to read the display both at night and in daylight. DOE9 DOE10 DOE11 DOE12 DOE13 DOE14 DOE15 DOE16

900 1000 1000 1000 1000 1100 1100 1100 0.9 1.1 1.1 1 0 1.1 1.1 1.8

- - - - - - Y Y

- - - - - - - - Type LED LED LED LED VFD LED LCD VFD Characters #, 1 x 4 #, 1 x 4 #, 1 x 4 #, 1 x 4 #, 1 x 4 #, 1 x 4 A, 1 x 6 A, 1 x 7 # of LEDs for backlighting N/A N/A N/A N/A N/A N/A 5 N/A Size 2.00" x 0.65" 1.85" x 1.10" 1.75" x 0.85" 1.75" x 0.70" 2.20" x 0.65" 2.00" x 0.65" 2.53" x 0.95" 2.25" x 0.75"

- - - - - - DOE14

-Display Stated Volume (ft 3 ) Cooking Sensor Inverter Power Supply

Unit is Similar to DOE Unit Number Rated Output Power (W)

DOE17 DOE18 DOE19 DOE20 DOE21 DOE22 DOE23 DOE24 1100 1100 1100 1100 1100 1100 1150 1200

1 1.4 1 1.3 1.1 1 1.4 2.2

- - - - - - Y Y

- - - - - - - Y Type LCD LCD LCD LED LED LCD VFD LCD Characters #, 1 x 4 A, 1 x 5 #, 1 x 4 #, 1 x 4 #, 1 x 4 #, 1 x 4 A, 1 x 7 A, 1 x 6 # of LEDs for backlighting 3 4 None N/A N/A 3 N/A 10 Size 1.83" x 0.80" 2.03" x 0.81" 1.87" x 0.83" 1.50" x 0.80" 1.47" x 0.80" 2.00" x 0.83" 2.25" x 0.75" 2.05" x 1.10"

- - DOE17

- - DOE17 DOE16 DOE30 DOE Unit Number Rated Output Power (W) Stated Volume (ft 3 ) Cooking Sensor Inverter Power Supply

Unit is Similar toDisplay

DOE25 DOE26 DOE27 DOE28 DOE29 DOE30 DOE31 DOE32 1200 1200 1200 1200 1200 1250 1300 1300 1.2 2.2 1.2 2 2 2.2 1.2 1.2

- Y Y Y Y Y Y Y

- Y

- - - Y Y Y Type LCD LCD LCD LCD LCD LCD LCD LCD Characters #, 1 x 4 A, 1 x 6 A, 1 x 7 D, 2 x 8 A, 1 x 7 A, 1 x 6 #, 1 x 4 A, 1 x 6 # of LEDs for backlighting 5 10 4 6 4 4 10 10 Size 1.85" x 0.83" 2.05" x 1.10" 2.03" x 0.78" 2.45" x 1.17" 2.03" x 0.78" 2.05" x 1.10" 1.75" x 0.80" 2.05" x 1.10" DOE17 DOE30 DOE25

- - DOE31

- DOE31 Inverter Power Supply

Unit is Similar to DOE Unit Number Rated Output Power (W) Stated Volume (ft 3 ) Cooking SensorDisplay5-15 Microwave

- Only Ovens Product Teardowns and Testing DOE conducted product teardowns and testing in support of its standby power investigation for microwave

- only ovens

. DOE also analyzed IEC Standard 62301 (First Edition) to determine its suitability for measuring standby power in microwave ovens

. DOE found the results produced by IEC Standard 62301 (First Edition) to be fairly cons istent for many microwave oven s
. However, for a few microwave oven s in the test sample, the standby power consumption varied by more than 5 percent over the course of 5 minutes, a threshold above which IEC Standard 62301 (First Edition) requires a longer 12

- hour standby test duration

. Investigating the source of these variations in power consumption, DOE determined that standby power can vary significantly with clock time, depending on the display type

. DOE tested a sub

- sample of microwave oven s over 12

- hour periods and subsequently developed an alternate 10

- minute standby power test that achieved results for average power consumption that were within 1 to 2 percent of the 12

- hour test results (see a ppendix 5B )

. Using the most consistent data fro m : (1) the IEC Standard 62301 5

- minute test, (2) the regression analysis as described in a ppendix 5B, and /or (3) 12

- hour tests, standby power for each microwave oven in the sub

- sample was characterized , t he minimum, maximum, and average input powers were r ecorded, and from the average standby power, an annual energy consumption in kWh was calculated

. Table 5.5

. 6 through Table 5.5

. 9 s ummarize these results.
Table 5.5
. 6 DOE Microwave

- Only Oven Standby Power (Table 1 of 4) DOE1 DOE2 DOE3 DOE4 DOE5 DOE6 DOE7 DOE8 700.0 700.0 700.0 700.0 800.0 800.0 800.0 800.0

0.7 0.7 0.7 0.7 1.0 1.0 0.8 0.8

- - - - Y

- - - Type LED LED LED LED VFD LED LCD LCD Characters #, 1 x 4 #, 1 x 4 #, 1 x 4 #, 1 x 4 A, 1 x 7 #, 1 x 4 #, 1 x 4 #, 1 x 4 # of LEDs for backlighting N/A N/A N/A N/A N/A N/A None None Size 1.50" x 0.43" 1.50" x 0.43" 1.45" x 0.70" 1.90" x 0.83" 2.25" x 0.75" 1.50" x 0.80" 1.87" x 0.83" 1.87" x 0.83" Min (W) 1.47 1.49 1.14 0.96 5.28 1.33 1.37 1.38 Average (W) 1.74 1.77 1.28 1.07 5.28 1.51 1.38 1.40 Max (W) 1.85 1.90 1.35 1.14 5.53 1.60 1.41 1.41 Annual (kWh) 15.22 15.47 11.21 9.40 46.28 13.22 12.12 12.28

- - - - - DOE5

- - DOE Unit Number
Stated Volume (ft 3 )

Unit is Similar toDisplayStandby Cooking Sensor Rated Output Power (W)5-16 T able 5.5
. 7 DOE Microwave

- Only Oven Standby Power (Table 2 of 4)

Table 5.5
. 8 DOE Microwave

- Only Oven Standby Power (Table 3 of 4)

Table 5.5
. 9 DOE Microwave

- Only Oven Standby Power (Table 4 of 4)

In the course of examining the 32 microwave

- only oven s in the test sample, DOE noted that all power supplies for the logic boards contain similar components

. Incoming AC line voltage is reduced via a small (2 to 7 VA) transformer, input to a bridge rectifier , and DOE9 DOE10 DOE11 DOE12 DOE13 DOE14 DOE15 DOE16 900.0 1,000.0 1,000.0 1,000.0 1,000.0 1,100.0 1,100.0 1,100.0

0.9 1.1 1.1 1.0 0.0 1.1 1.1 1.8

- - - - - - Y Y Type LED LED LED LED VFD LED LCD VFD Characters #, 1 x 4 #, 1 x 4 #, 1 x 4 #, 1 x 4 #, 1 x 4 #, 1 x 4 A, 1 x 6 A, 1 x 7 # of LEDs for backlighting N/A N/A N/A N/A N/A N/A 5 N/A Size 2.00" x 0.65" 1.85" x 1.10" 1.75" x 0.85" 1.75" x 0.70" 2.20" x 0.65" 2.00" x 0.65" 2.53" x 0.95" 2.25" x 0.75" Min (W) 1.26 1.09 1.11 1.42 2.46 1.16 3.08 3.08 Average (W) 1.49 1.23 1.26 1.75 2.48 1.40 3.10 3.08 Max (W) 1.58 1.30 1.33 1.88 2.49 1.49 3.12 3.31 Annual (kWh) 13.09 10.73 11.01 15.32 21.71 12.26 27.14 26.95

- - - - - - DOE14

- DOE Unit Number Rated Output Power (W) Stated Volume (ft 3 ) Cooking SensorDisplayStandby

Unit is Similar to

DOE17 DOE18 DOE19 DOE20 DOE21 DOE22 DOE23 DOE24 1,100.0 1,100.0 1,100.0 1,100.0 1,100.0 1,100.0 1,150.0 1,200.0

1.0 1.4 1.0 1.3 1.1 1.0 1.4 2.2

- - - - - - Y Y Type LCD LCD LCD LED LED LCD VFD LCD Characters #, 1 x 4 A, 1 x 5 #, 1 x 4 #, 1 x 4 #, 1 x 4 #, 1 x 4 A, 1 x 7 A, 1 x 6 # of LEDs for backlighting 3 4 None N/A N/A 3 N/A 10 Size 1.83" x 0.80" 2.03" x 0.81" 1.87" x 0.83" 1.50" x 0.80" 1.47" x 0.80" 2.00" x 0.83" 2.25" x 0.75" 2.05" x 1.10" Min (W) 1.64 1.64 1.30 1.46 1.32 1.70 3.05 2.57 Average (W) 1.65 1.66 1.31 1.65 1.55 1.72 3.05 2.59 Max (W) 1.67 1.67 1.34 1.73 1.66 1.73 3.18 2.60 Annual (kWh) 14.48 14.51 11.48 14.44 13.57 15.02 26.68 22.66

- - DOE17

- - DOE17 DOE16 DOE30 DOE Unit Number Rated Output Power (W) Stated Volume (ft 3 ) Cooking Sensor

Unit is Similar toDisplayStandby

DOE25 DOE26 DOE27 DOE28 DOE29 DOE30 DOE31 DOE32 1,200.0 1,200.0 1,200.0 1,200.0 1,200.0 1,250.0 1,300.0 1,300.0

1.2 2.2 1.2 2.0 2.0 2.2 1.2 1.2

- Y Y Y Y Y Y Y Type LCD LCD LCD LCD LCD LCD LCD LCD Characters #, 1 x 4 A, 1 x 6 A, 1 x 7 D, 2 x 8 A, 1 x 7 A, 1 x 6 #, 1 x 4 A, 1 x 6 # of LEDs for backlighting 5 10 4 6 4 4 10 10 Size 1.85" x 0.83" 2.05" x 1.10" 2.03" x 0.78" 2.45" x 1.17" 2.03" x 0.78" 2.05" x 1.10" 1.75" x 0.80" 2.05" x 1.10" Min (W) 1.68 2.57 3.50 3.86 3.38 2.79 2.08 2.81 Average (W) 1.70 2.59 3.52 3.88 3.41 2.82 2.09 2.82 Max (W) 1.71 2.60 3.60 3.93 3.46 2.86 2.10 2.86 Annual (kWh) 14.86 22.66 30.84 34.02 29.90 24.69 18.28 24.72 DOE17 DOE30 DOE25

- - DOE31

- DOE31 Rated Output Power (W)

Unit is Similar to Stated Volume (ft 3 ) Cooking SensorDisplayStandby DOE Unit Number5-17 subsequently smoothed with capacitors to produce unregulated DC voltage (VDC)

. Multiple voltages for logic integrated circuits (ICs) (usually 5 VDC or less) an d relay control (12 to 24 VDC) are established either via multiple taps on the transformer or through the use of voltage regulators

. None of the microwave oven s analyzed by DOE feature an on/off switch or electromechanical controls

. DOE is unaware of any m icrowave oven s still on the market with electromechanical controls and no displays ; DOE believes that the U.S. microwave oven market has completely transitioned to electronic controls with displays

. Thus, all sampled microwaves
consume standby power while waiting for user input

. DOE does not believe that any domestic microwave ovens are capable of operating in off mode, as defined by EPCA

. (42 U.S.C. 6295(gg)(1)(A)(ii))
The average standby power, disaggregated by display type and the presence of a cooking
sensor as shown in Figure 5.5

. 2 , exhibits a relatively wide range of values

. These measured data correlate well with the standby power measurements that AHAM submitted to DOE (see Fi gure 5.5.3 )

. In the DOE test sample, none of the microwave oven s with LED displays include a cooking sensor, and these models all consume less than 2 W in standby mode

. Similar low standby pow er requirements were observed for microwave ovens with LCD displays and no cooking sensors

. For those microwave ovens with LCD displays and cooking sensors, the standby power ranged from 2 to 4 W

. VFD

- equipped microwave ovens demonstrate fairly consistent power draw , and the microwave oven with the highest standby power use s a cooking sensor and a VFD. In the following figures , the legend key includes designations for the presence of a cooking sensor (CS), backlighting (B), and inverter drive for the magne tron (I).5-18 Figure 5.5
. 2 DOE M icrowave

- Only Oven Standby Power Consumption as a Function of Rated Output Power While AHAM did not identify specific models in its data submittal, and thus DOE could not derive information on display type, the data do es note which microwave oven s contain cooking sensors

. Like the microwave oven s in the DOE test sample, the microwave ovens with cooking sensors in the AHAM sample, ha ve on average, higher standby power consum ption than microwave oven s without cooking sensors

. 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0 5.5 6.0

650 750 850 950 1050 1150 1250 1350 Rated Power Output (W)Standby Power (W) LED VFD VFD, CS LCD LCD, B LCD, B, CS LCD, B, CS, I5-19 Figure 5.5
. 3 AHAM Microwave Oven Standby Power Consumption a s a Function of Rated Output Power 12 Based on these standby p ower observations, DOE conclude s that standby power is a function of features including the display, the presence of a cooking sensor, and controller power requirements

. The following sections discuss the impact of each of these features on overall standby power consumption. Impact of Display Type on Standby Power DOE noted three different types of displays among the 32 microwave oven s in its sample

. The sampled display capabilities ranged from only being able to display numbers, to displaying alphanumeric characters, to incorporating dot

- matrix

- based displays which allow the display of multiple fonts, symbols, and , in some cases, graphics. Display power requirements depend on the fundamental technology as well as the size of the display, the brightness, and the number and range of charac ters it can display

. Figure 5.5

. 4 illustrates measured standby power consumption as a function of display size

. 1 1.5

2 2.5

3 3.5

4 4.5

5 5.5

6

650 750 850 950 1050 1150 1250 1350 Rated Output Power (W)Standby Power (W) No Sensor
Sensor5-20 Figure 5.5
. 4 DOE Microwave

- Only Oven Standby Power Consumption as a Function of Display Size Figure 5.5

. 5 through Figure 5.5

. 7 show the average measured standby power with minimum and maximum values for each type of display

. See a ppendix 5C for a further discussion of display technologies

.

**•** Light Emitting Diode ( LED) LED displays operate by individually lighting up each element in the display to create a character or number or to illuminate a symbol

. DOE confirmed that the power consumption of such displays varies depending on how many elements (and hence diodes) are active at any given time

. Thus, LED

- display

- equipped microwave oven s demonstrate the greatest variation in standby power consumption over the course of a day as the clock cycles. The span between the maximum and minimum standby power consumption, based on the number of elements illuminated, range s from 0.2 to 0.4 W in the DOE test sample

. Figure 5.5

. 5 shows the average standby power consumption (with maximum and minimum values) for microwave ovens with LED displays as a function of the measured size of the display in square inches

. DOE fou nd no apparent correlation between display size and standby power consumption

. DOE recognizes that diode energy efficiency characteristics may be an important variable, but one for which DOE was not able to ascertain any information

. 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0 5.5

0.5 1.0 1.5 2.0 2.5 3.0 Display size (in 2 )Standby Power (W) LED VFD VFD, CS LCD LCD, B LCD, B, CS LCD, B, CS, I5-21 Figure 5.5
. 5 DOE Standby Power Consumption as a Function of Display Size for Microwave

- Only Ovens with LED Displays

**•** Vacuum

- Fluo rescent Display (VFD) VFDs typically require more power than LCD

- or LED

- based displays, but offer h igh brightness levels and wide viewing angles

. Note that the three VFD models with cooking sensors ha ve a feature that allow s the display to be switched off , but selecting this option decrease s standby power consumption by only 0.1 to 0.25 W

. According to the IEC Standard 62301 test procedure, standby power would be measured with the displays powered off, resulting in a constant average value over the 12

- hour period

. These data are denoted in Figure 5.5

. 6 by the symbols

. DOE also measured the variations in standby power with the display s on during the 12

- hour cycle for these units , and these variations , which are all additive from the minimum standby power levels measured with the displays turned off, are indicated on the chart by bars on each symbol

. 0.8 1.0 1.2 1.4 1.6 1.8 2.0

0.5 1.0 1.5 2.0 2.5 Display Size (in 2 )Standby Power (W)5-22 Figure 5.5
. 6 DOE Standby Power Consumption as a Function of Display Size for Microwave

- Only Oven s with VFD Displays

**•** Liquid Crystal Display (LCD), with or without backlighting
An LCD without backlighting requires some ambient light to allow a user to read it because it relies on reflected light to create a visible contrast

. LCDs without backlighting are frequen tly found on entry

- level microwave oven s, whereas more expensive units tend to have backlit displays

. LCDs with backlighting can be read regardless of ambient lighting conditions

. The backlighting typically consists of multiple LEDs mounted behind the LCD display on the same circuit board

. LCDs with backlighting were found on 12 of the microwave ovens in the DOE sample

. As shown in Figure 5.5

. 7 , the standby power consum ption for microwave ovens with LCDs in the DOE sample remains nearly constant over time (since the bars showing variation during 12

- hour tests are virtually indistinguishable from the symbols denoting the average values.) Figure 5.5

. 7 also shows that the addition of a cooking sensor raises standby power consumption, on average, to over 2 W. 2.0 2.5 3.0 3.5 4.0 4.5 5.0 5.5 6.0

1.4 1.5 1.6 1.7 1.8 Display Size (in 2 )Standby Power (W)

VFD VFD, CS5-23 Figure 5.5
. 7 DOE Standby Power Consumption as a Function of Display Size for Microwave

- Only Oven s with LCD Displays Based on its research, DOE conclude s that certain display technologies such as VFDs inherently consume more power, on average, than compara b ly

- sized display s using other illumination technologies

. Standby power is also a function of the size and the complexity of the display ; more complex and larger displays typically consume more power than smaller, simpler displays. Impact of a Cooking Sensor on Standby Power
DOE noted from its testing that microwave oven s with cooking sensors typically consume more power than comparable models that do not feature a cooking sensor

. From its
reverse - engineering activities, DOE identified two different types of cooking sens ors generally used in microwave oven s: (1) absolute humidity sensors; and (2) piezo

- electric steam sensors

. A literature review of identifiable absolute humidity cooking sensors indicates that such sensors typically supply power to a resistive heating element whose conductivity changes in response to the presence of water vapor or other gases associated with food cooking processes

. Based on its standby power observations between otherwise identical microwave ovens and information provided by sensor manu facturers, DOE concludes that the resistive elements in the cooking sensors are typically maintained at operating temperature during standby mode because warmup times (which can be several minutes) are longer than many microwave oven cooking times. The spe cification sheet for one representative absolute humidity cooking sensor note s that the sensor requires approximately 0.9 W to remain warm and ready for use

. Based on a typical power supply efficiency of about 65 percent, the required microwave oven input power associated with the absolute humidity cooking sensor is thus approximately 1.6 W

. Other 1.0 1.5 2.0 2.5 3.0 3.5 4.0

1.0 1.5 2.0 2.5 3.0 Display size (in 2 )Standby Power (W)

LCD LCD, B LCD, B, CS LCD, B, CS, I5-24 microwave

- only oven s in the DOE sample use absolute humidity sensors whose power requirements appear comparable to those for the absolute humidity sensor referenc ed above

. Testing performed on the steam sensors used in a number of microwave

- only ovens in the DOE sample revealed that these sensors do not consume power in standby mode

. For further discussion of steam cooking sensors, refer to chapter 3 of this TSD

. Table 5.5 .10 shows a comparison of standby power for three pairs of microwave oven s in the DOE sample containing the same basic parts (power conditioner , transformer, magnetron, and cavity) with and without a n absolute humidity cooking sensor

. In all three cases, the microwave oven s with a cooking sensor consume at least 1.6 W more than comparable microwave oven s without a sensor

. In the case of DOE test units #5 and #6, assuming the absolute humidity cooking sensor consumes about 1.6 W implies that the remaining differential between the two units of approximately 2.2 W of standby power consumption is attributable to the use of a VFD instead of an LED

. The standby power consumption of other absolute humidity sensors, which can be inferred from units #25 and 27 with similar displays, is approximately 1.8 W

. Table 5.5
. 10 DOE Standby Power Requirements among Simi lar Microwave

- Only Ovens with Different Options

Figure 5.5.8 shows the cumulative impact of each design option on overall standby power
. The figur e shows the average standby power consumption for all microwave oven models in the DOE sample which have the designated design options , as well as the minimum and maximum values for each group

. Test Unit # Display Type # of LEDs used to backlight display Display Size Cooking Sensor Type Avg. Standby Power Consumption (W)
DOE21 LED N/A 1.47" x 0.80" None 1.55 DOE15 LCD 5 2.53" x 0.95" Absolute Humidity 3.10 DOE6 LED N/A 1.50" x 0.80" None 1.51 DOE5 VFD N/A 2.25" x 0.75" Absolute Humidity 5.28 DOE25 LCD 5 1.85" x 0.83" None 1.70 DOE27 LCD 4 2.03" x 0.78" Absolute Humidity 3.525-25 Figure 5.5
. 8 DOE Standby Power Consumption Associated with Different Design Options
Incremental Cos t Data for Standby Powe r Levels for Microwave

- Only Ovens and Countertop Combination Microwave Ovens From the standby power testing and reverse

- engineering, DOE observ ed correlations between (1) specific components and technologies, or combinations thereof, and (2) measured standby power

. Costs for each of the components and technologies were estimated by DOE using quotes obtained from suppliers, interviews with manufac turers, interviews with subject matter experts, research and literature review, and numerical modeling

. Preliminary incremental manufacturing costs associated with the standby power levels were then obtained by considering combinations of these components as well as other technology options identified to reduce standby power

. Manufacturer interviews were also conducted to obtain greater insight into the design strategies to improve efficiency and the associated costs. As discussed above in section 5.2 , DOE believes the standby power levels and characteristics of power supply designs ( i.e. , size of the power supply) associated with microwave

- only countertop and over

- th e - range units as well as countertop combination microwave ovens are similar. As a result, DOE proposed to analyze microwave

- only ovens and countertop combination microwave ovens as a single product class. Therefore, DOE developed a single cost

- energy use r elationship for this product class. The design options DOE considered in the engineering analysis include various display technologies, cooking sensors with no standby power requirement, higher

- efficiency controller power supplies and relays, and improved control strategies

. For details on the microwave oven standby design options, refer to chapter 3 of this TSD

. DOE selected the design option(s) it believed manufactures would most likely implement to achieve a given standby power level for a given display technology

. The incremental cost, then, for each display technology was weighted by the estimated percentage of shipments currently using that type of display in order to obtain a 0.0 1.0 2.0 3.0 4.0 5.0 6.0

LED LCD LCD Backlit LCD Backlit, Absolute Humidity Cooking Sensor LCD Backlit, Steam Cooking Sensor, Inverter VFD VFD, Absolute Humidity Cooking SensorStandby Power (W) Maximum Minimum Average5-26 weighted

- average incremental cost at each standby power level above the bas eline

. DOE believes that, in order to meet standby power level 1, manufacturers would likely have to utilize a cooking sensor with no standby power requirements

. Additionally, for microwave oven s with VFDs and backlit LCDs, the conventional power supplies would need to be upgraded to higher efficiency conventional power supplies

. Standby power level 2 would likely also require LED

equipped microwave oven s to upgrade the efficiency of the existing power supply, and DOE believes that manufacturers would have to change to sensitive

- coil relays in order to continue using VFDs

. To move from standby power level 2 to standby power level 3, DOE believes that manufacturers would have to additionally incorporate the sensitive

- coil relays for LED and backlit LCD

- based microwave oven s
. Optionally, manufacturers of LED

- equipped microwave
oven s could choose to change to a switching power supply without upgrading the relays

. Each of these two LED options was assumed to be equally likely since the cost of each path was simil ar
. At standby power level 3, backlit LCD

- equipped microwave oven s would likely also need to be change d to a switching power supply along with implementing the sensitive

- coil relays

. DOE believes t he only way for manufacturers of VFD

- equipped microwave ove n s to meet a 1 W standby threshold would be to implement an automatic powerdown feature, in which a controller turns off power to standby

- power - consuming components after a certain period of inactivity

. This feature would also allow VFD

- equipped microwave oven s to meet standby power level 4, and would be the approach for microwave oven s with the other display technologies to meet standby power level 4 as well

. Table 5.5 .11 presents the incremental manufacturing costs for each standby power level for microwave ovens

. DOE originally developed and presented these costs the October 2008 NOPR, and therefore costs were presented in $2007. DOE updated these costs to $20 10 to reflect changes in the producer price index (PPI) for electronic components and accessories

. Based on conversations with manufacturers and OEM suppliers, and the reverse

engineering analysis, DOE believes that all manufacturers can and likely will implement zero

standby cooking sensors by the effective date of standby mode and off mode energy conservation standard s
. Thus, DOE believes that consumer utility would not be impacted by a standard at standby power levels 1 or 2, since all disp lay types could continue to be u s ed

. At standby power level 3 for VFDs and standby power level 4 for all display technologies , DOE analysis suggests the need for a separate controller (auto power

- down) that automatically turn s off all other power consuming components during standby mode

. Such a feature would affect the consumer utility of having a clock display only if the consumer could not opt out of auto power

- down

. Table 5.5
. 11 Incremental Manufacturing Costs for Microwave

- Only Oven and Countertop Combination Microwave Oven Standby Power

Standby Power Level Standby Power , W Incremental Cost , 2007$ Incremental Cost , 20 10 $ Baseline 4.0 $ 0 $ 0 1 2.0 $ 0.30 $ 0.27 2 1.5 $ 0.67 $ 0.6 0 3 1.0 $ 1.47 $ 1.3 1 4 0.02 $ 5.13 $ 4. 585-27 Countertop Combination Microwave Oven Testing and Product Teardown
DOE also conducted standby power testing on 5 countertop combination microwave
ovens , presented below in Table 5.5

. 12

. Testing showed standby power levels ranging from 1.2 W to 4.7 W , with an average of 3.0 W . As discussed above in section 5.2 , these standby power levels are similar to the standby power levels for microwave

- only ovens. DOE also noted that the countertop combination microwave ovens used similar display types as microwave

- only ovens ( i.e. , LED displays, LCDs, and VFDs).
Table 5.5
. 12 DOE Countertop Combination Microwave Oven Standby Power DOE Countertop

Combo MWO Test Unit Rated Microwave Cooking Output Power, W Display Type Display Size, in. 2 Cooking Sensor # of Heaters Average Standby Power, W DOE CTC1 1,000 LED 2.25

- 2 1.20
DOE CTC2 900 LCD w/ LED Backlight 3.75

- 2 2.36
DOE CTC3 900 VFD 3.00 Yes 1 3.23
DOE CTC4 1,100 LCD w/ LED Backlight 2.66 Yes 1 3.55
DOE CTC5 1,000 VFD 10.86 Yes 1 4.68 Figure 5.5

. 9 illustrates the measured standby power consumption as a function of display size for countertop combination microwave ovens. Similar to microwave

- only ovens, DOE observed that standby power tends to increase as display size increases.5-28 Figure 5.5
. 9 DOE Standby Power Consumption as a Function of Display Size for Countertop Combin ation Microwave Ovens DOE also conducted product teardowns and standby power testing of individual components contributing to the total standby power consumption. DOE noted that the cooking sensors used in these models were similar to those used in micro wave - only ovens. DOE also investigated the requirements for the size of the controls power suppl y for countertop combination microwave ovens. DOE noted that the size of a conventional linear power supply depends largely on the transformer used to step down the line input voltage to operate the controls. DOE isolated the power supply transformers in the controls these countertop combination microwave ovens and measured the standby power consumption. DOE similarly measured the power supply transformer standby power consumption for a limited number of the microwave

- only ovens in its test sample. The results from this testing, presented below in Table 5.5

. 13 , showed that th e size of the controls power supplies ( i.e. , the standby losses associated with the power supply transformers) were similar for both countertop combination microwave ovens and microwave

- only ovens. In addition, as presented above in T able 5.5

. 12 , the total standby power consumption for countertop combination microwave ovens is similar to that for microwave

- only ovens. For these reasons, DOE believes that the size s of the power suppl i es for countertop microwave ovens are similar to those for microwave

- only ovens. As a result , DOE did not establish a separate product class for countertop combination microwave ovens. Therefore, the incremental manufacturing costs listed above in Table 5.5 .11 would also apply for countertop combination microwave ovens.5-29 Table 5.5
. 13 Control Power Supply Transformer Standby Power Test Results DOE Countertop Combo MWO Test Unit Transformer Standby Power, W DOE Microwave

Only Test Unit Transformer Standby Power, W DOE CTC1 0.57 DOE28 1.44 DOE CTC2 0.95 DOE29 0.89 DOE CTC3 0.93 DOE30 1.11 DOE CTC4 1.81 DOE CTC5 1.08

Built

- In and Over

- the

- Range Combination Microwave Ovens

. Built

- In and Over

- the

- Range Combination Microwave Oven Testing and Product Teardown
As discussed above in section 5.2 , DOE proposed to analyze a separate product class for built

- in and over

- the

- range combination microwave ovens. DOE conducted standby power testing on a sample of six over - the

- range combination microwave ovens and two built

- in combination microwave ovens. The results from this testin g are shown below in Table 5.5

. 14

. Testing showed standby power levels ranging from 4.1 W to 8.8 W. DOE noted that all of the units in its test sample had a cooking sensor and either a LCD touch screen with backlighting or a VFD

. DOE noted that the built

- in combination microwave ovens in its test sample consumed more standby power than the over

- the

- range combination microwave ovens. However, DOE also noted that these two units were high er - end units with larger displays and a larger number of cooking settings and options.
Table 5.5
. 14 DOE Built

- In and Over

- the

- Range Combination Microwave Oven Standby Power DOE Built

In/Over

- the

Range Combo MWO Test Unit Installation Rated Microwave Cooking Output Power, W Display Type Display Size , in. 2 Cooking Sensor # of Heaters Average Standby Power, W DOE OTRC1 Over

- the

Range 1,200 LCD Touch w/ Backlight 13.66 Y 4 4.19
DOE OTRC2 Over

- the

Range 1,200 LCD Touch w/ Backlight 13.66 Y 4 4.37
DOE OTRC3 Over

- the

Range 1,100 VFD 3.91 Y 4 4.50
DOE OTRC4 Over

- the

Range 1,100 VFD 3.91 Y 1 4.59
DOE OTRC5 Over

- the

Range 1,000 VFD 7.75 Y 1 4.14
DOE OTRC6 Over

- the

Range 900 VFD 4.00 Y 4 6.65 DOE BC1 Built

- In 975 VFD 7.39 Y 4 8.16 DOE BC2 Built

- In 950 VFD 7.39 Y 4 8.765-30 As discussed above for microwave

- only ovens, display power requirements depend on the fundamental technology as well as the size of the display, the brightness, and the number and range of characters it can display. Figure 5.5

. 10 illustrates the measured standby power consumption as a function of display size for built

- in and over

- the

- range combination microwave
ovens
.

Figure 5.5
. 10 DOE Standby Power Consumption as a Function of Display Size for Built

- In and Over

- the

- Range Combination Microwave Ovens For each sample test unit, DOE also conducted standby power testing on individual components contribu ting to the total standby power consumption of each unit

. DOE isolated and measured the standby power consumption of power filtration printed circuit boards, cooking sensors, and displays/user interface control boards. Results of this testing are shown bel ow in Table 5.5

. 15 . DOE noted that the power filtration boards consumed on average approximately 0.03 W. Similarly, cooking sensors consumed on average 0.86 W in stan dby mode. DOE also noted that display and user interface control board standby power consumption ranged from 0.75 W to 4.24 W, with an average of 2.03 W. Note that DOE was not able to isolate every component consuming power in standby mode, therefore the p ower consumption of the individual components listed in the Table 5.5

. 15 will not add up to the total standby power consumption of the unit.5-31 Table 5.5
. 15 DOE Built

- In and Over

- the

- Range Combination Microwave Oven Disaggregated Components Standby Power Consumption DOE Built

- In/Over

the

- Range Combo MWO Test Unit Standby Power Consumption, W Power Filtration Board Cooking Sensor Display/User Interface Total Unit DOE OTRC1 0.06 0.82 1.88 4.19 DOE OTRC2 0.06 0.84 1.96 4.37 DOE OTRC3 0.03 0.82 0.75 4.50 DOE OTRC4 0.03 0.82 0.75 4.59 DOE OTRC5 0.01 0.92 1.38 4.14 DOE OTRC6 0.01 0.68 1.1 6.65

DOE BC1 0.01 1.05 4.15 8.16 DOE BC2 0.01 0.96 4.24 8.76

Incremental Cost Data for Standby Power Levels for Built

- In and Over

- the

- Range Combination Microwave Ovens DOE conducted standby power testing and reverse engineering analyses on the 8 built

- in and over

- the

- range combination microwave ovens in its test sample in order to develop the cost

efficiency relationships. DOE used a design

- option approach to determine t he incremental manufacturing costs of combination microwave ovens for each standby power level. As discussed ab ove for the microwave

- only oven and counte rtop combination microwave oven product class, DOE observed correlations between specific components an d technologies, or combinations thereof, and measured standby power. Costs for each of the components and technologies used at each standby power level were estimated by DOE using quotes obtained from various component suppliers as well as interviews with manufacturers. For standby power level 1, DOE believes that, similar to the microwave

- only oven and countertop combination microwave oven product class, manufacturers would likely have to utilize a cooking sensor with no standby power requirements. DOE estimated that the manufacturing cost of a zero

- standby cooking sensor would be the same as that of the cooking sensor with high standby power. DOE believes that, in order to achieve standby power level 2, manufacturers would likely change the conve ntional linear power supply to a switch mode power supply. DOE used reverse engineering to determine the cost of the components used in a design of a switch mode power supply capable of delivering the same output power as the baseline conventional linear p ower supply. To move from standby power level 2 to standby power level 3, DOE estimated the cost of implementing a control board design with a switch mode power supply and replacing the electromechanical relays (used to drive components such as heaters , motors, lights, etc.) with solid state relays capable of driving the same loads as the electromechanical rela ys. Because implementing solid state relays would decrease the total power requirements of the control5-32 board, DOE also estimated the cost of chan ging power supply components based on the smaller power supply size. For standby power level 4, DOE estimated the manufacturing cost based on the cost of the components needed to design an automatic power

- down function that uses a transformerless power s upply for the microprocessor chip along with a conventional linear power supply that is activated when the unit goes into active mode. DOE also estimated the costs associated with a door limit switch and Triac to control power through the transformer.

T he results of this analysis for built

- in and over

- the

- range combination microwave ovens
are summarized in Table 5.5

. 16

. Table 5.5
. 16 Built

- In and Over

- the

- Range Combination Microwave Oven Incremental Manufacturing Costs Standby Power Level Maximum Average Standby Power Consumption, W Incremental Cost, 20 10 $ Baseline 4.5 $ 0 1 3.7 $ 0 2 2.7 $ 2. 29 3 2.2 $ 9. 44 4 0.04 $ 5.1 85-33 REFERENCES

1 American Metals Market . Available online at http://www.amm.com/

. (Accessed May 2011)

2 Association of Home Appliance Manufacturers (AHAM). 2006. AHAM Test Data on Microwave Ovens . October 23, 2006

. Docket No. EE

- 2006

- STD

- 0127, Comment Number 17.

3 Ibid.

4 Ibid

.
5 Ibid

.
6 Fish, N. et al . 2006. Standby Power Energy Use of Common Household Appliances

. Canadian Building Energy End

- Use Data and Analysis Centre, CBEEDAC 2006

- RP

- 04

- DRAFT, July 2006.

7 Aulenback, A. et al . 2001. Stand

- By Power Requirements for Household Appliances

. Canadian Residential Energy End

- Use Data and Analysis Centre, CREEDAC

- 2001

- 05

- 04, May 200 1.

8 Ibid

.
9 Lawrence Berkeley National Laboratory (LBNL). 2008

. Low

- Power Mode Energy Consumption in California Homes

. Report CEC

- 500

- 2008

- 035 prepared for California Energy Commission, September 2008. Available online at http://www.energy.ca.gov/2008publications/CEC

- 500

- 2008

- 035/CEC

- 500

- 2008

- 035.PDF

. (Accessed May 2011)

10 Floyd, D. and Webber, C. 1998. “Leaking Electricity: Individual Field Measurement of Consumer Electronics

. ” Proceedings of American Council for an Energy

- Efficient Economy , Florida Solar Energy Center, August 1998.

11 Meier, A. and Huber, W. 1997. Results from the Investigations on Leaking Electricity in the USA . Lawren ce Berkeley National Laboratory, Berkeley, CA, LBNL

- 40909, 1997.