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CHAPTER 4. SCREENING ANALYSIS

TABLE OF CONTENTS

4.1 INTRODUCTION ........................................................................................................... 4-1

4.2 SCREENED-OUT TECHNOLOGY OPTIONS ............................................................. 4-1

4.3 REMAINING DESIGN OPTIONS ................................................................................. 4-3

LIST OF TABLES

Table 4.2.1 Retained Design Options for Microwave Ovens–Standby Power....................... 4-4
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CHAPTER 4. SCREENING ANALYSIS

4.1 INTRODUCTION

This chapter details the screening analysis conducted by the U.S. Department of Energy 

(DOE) of the technology options identified in the market and technology assessment for 

residential microwave ovens (chapter 3 of this technical support document (TSD)). In the market 

and technology assessment, DOE presented an initial list of technologies that can be used to 

reduce the standby power consumption of microwave ovens. The goal of the screening analysis 

is to identify any technology options that will be eliminated from further consideration in the 

rulemaking analyses.

The candidate technology options are assessed based on DOE’s analysis as well as inputs 

from stakeholders including manufacturers, trade organizations, and energy efficiency advocates.

Technology options that are judged to be viable approaches for improving standby consumption

are retained as inputs to the subsequent engineering analysis, and are designated as design 

options. Technology options that are not incorporated in commercial products or in working 

prototypes, or that fail to meet certain criteria, as to practicability to manufacture, install and 

service, as to impacts on product utility or availability, or as to health or safety will be eliminated 

from consideration in accordance with Energy Conservation Program for Consumer Products: 

Procedures for Consideration of New or Revised Energy Conservation Standards for Consumer 

Products. 61 FR at 36974 (July 15, 1996). The rationale for either screening out or retaining each 

technology option is detailed in the following sections.

4.2 SCREENED-OUT TECHNOLOGY OPTIONS

The following section details the specific technology options that were screened out prior 

to the engineering analysis, along with the rationale for elimination.

The technologies identified in the market and technology assessment were evaluated 

pursuant to the criteria set out in the Energy Policy and Conservation Act (EPCA). (42 United 

States Code (U.S.C.) 6291-6309) EPCA establishes criteria for prescribing new or amended 

standards designed to achieve the maximum improvement in energy efficiency. Furthermore, 

EPCA directs the Secretary of Energy to determine whether a standard is technologically feasible 

and economically justified. (42 U.S.C. 6295(o)(2)(A)(B)) In view of the EPCA requirements for 

determining whether a standard is technologically feasible and economically justified, appendix 

A to subpart C of Title 10 Code of Federal Regulations part 430 (10 CFR part 430), Procedures, 

Interpretations and Policies for Consideration of New or Revised Energy Conservation 

Standards for Consumer Products (the Process Rule), sets forth procedures to guide DOE in the 

consideration and promulgation of new or revised product energy conservation standards under 

EPCA. These procedures elaborate on the statutory criteria provided in 42 U.S.C. 6295 and in 

part eliminate problematic technologies early in the process of revising an energy conservation
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standard. Under the guidelines, DOE eliminates from consideration technologies that present 

unacceptable problems with respect to the following four factors: 

(1) Technological feasibility. If it is determined that a technology has not been 

incorporated in commercial products or in working prototypes, then that technology will not be 

considered further.

(2) Practicability to manufacture, install, and service. If it is determined that mass 

production of a technology in commercial products and reliable installation and servicing of the 

technology could not be achieved on the scale necessary to serve the relevant market at the time 

of the effective date of the standard, then that technology will not be considered further.

(3) Impacts on product utility to consumers. If a technology is determined to have 

significant adverse impact on the utility of the product to significant subgroups of consumers, or 

results in the unavailability of any covered product type with performance characteristics 

(including reliability), features, size, capacities, and volumes that are substantially the same as 

products generally available in the United States at the time, it will not be considered further. 

(4) Safety of technologies. If it is determined that a technology will have significant 

adverse impacts on health or safety, it will not be considered further.

After reviewing the technology options to reduce standby power consumption of 

microwave against the screening criteria, DOE did not eliminate any technology options from 

consideration in its standby power rule making analysis for microwave ovens.

For lower-power display technologies, DOE understands that the consumer utility of a 

microwave oven display is associated with its brightness, viewing angle, and ability to display 

complex characters. Interviews DOE conducted with display manufacturers revealed that 

vacuum fluorescent displays (VFDs) can achieve higher brightness levels, wider viewing angles, 

and higher contrast than backlit liquid crystal displays (LCDs). Display manufacturers also stated 

that light-emitting diode (LED) displays have largely comparable performance to VFDs in terms 

of brightness and viewing angle. A VFD manufacturer mentioned that, while VFD technologies 

with efficiencies comparable to backlit LCDs do exist, such displays are substantially more 

expensive than the ones commonly found in microwave ovens today. 

Multiple manufacturers of cooking products stated in interviews the need to differentiate 

their cooking appliance lines from those of their competitors with (among other features) 

coordinated displays and user interfaces. Manufacturers noted that LCD displays (backlit or not) 

do not work well in appliances that get very hot, such as ovens, due to thermal limitations in the 

technology. Manufacturers also opposed switching entirely to LED-based displays since it could 

make it harder for them to differentiate their products, particularly in a market as commoditized 

as microwave ovens. Lastly, manufacturers noted that larger, more complex, and more colorful 

displays are usually associated with premium appliances, which will thus have a harder time 
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achieving the same standby power consumption as units with smaller, dimmer, and simpler 

displays. 

DOE notes that the current rulemaking does not seek to regulate the standby power 

consumption of conventional cooking appliances, and microwave ovens do not feature high 

surface temperatures which could preclude certain display options, as noted in the DOE sample. 

DOE also notes that not all high-end appliance manufacturers use the same display technology 

across all cooking appliances that they manufacture. For example, at least one manufacturer uses 

a backlit LCD in its microwave oven, with the backlighting LEDs color-coordinated with the 

VFDs found in its ovens. For these reasons, DOE believes that lower-power display technologies 

which maintain consumer utility can be incorporated in microwave ovens, and meet all of the 

screening criteria.

Similarly, the number of different sensor technologies available on the market that do not 

require standby power suggests that the utility of a cooking sensor can be maintained with zero 

standby power. Since improved power supplies and control board options also have no consumer 

utility impacts and have been incorporated in products currently available on the market, both of 

these technology options meet the screening criteria.

For automatic power-down, DOE interviewed the Japanese Electrical Manufacturers’ 

Association (JEMA). These discussions revealed that there are a large number of microwave 

ovens in the Japanese market that implement this feature. For a power-down function, DOE 

believes that the entire microwave oven can be switched off, with a dedicated, low power 

controller waiting for a controls input, door opening, etc. before re-animating the rest of the 

microwave. This controller then subsequently detects a period of inactivity before switching the 

rest of the microwave oven off again. Power consumption could be reduced to well below 1 W, 

though at a reduction in consumer utility since displays, night lights, etc. would remain off until 

a consumer interacts with the microwave oven. DOE has determined, however, that control 

strategies are available to allow manufacturers to make design tradeoffs between incorporating 

standby-power-consuming features such as displays or cooking sensors and including a function 

to turn power off to these components during standby. Therefore, this technology option was 

retained for further analysis.

4.3 REMAINING DESIGN OPTIONS

The following sections list the technology options for each product covered by this 

rulemaking that were retained by DOE and subsequently designated as design options. Each of 

these technologies will be evaluated further in the subsequent engineering analysis.
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Table 4.3.1 Retained Design Options for Microwave Ovens–Standby Power

1. Lower-power display technologies

2. Cooking sensors with no standby power requirement

3. Improved power supply and control board options

4. Automatic power-down