5A-i

APPENDIX 5A. AHAM DATA SUBMITTAL

TABLE OF CONTENTS

5A.1 INTRODUCTION .................................................................................................. 5A-1

5A.2 AHAM MICROWAVE OVEN DATA SUBMITTAL.......................................... 5A-1

LIST OF FIGURES

Figure 5A.2.1 AHAM Standby Power Test Data ................................................................. 5A-6
5A-1

APPENDIX 5A. AHAM DATA SUBMITTAL

5A.1 INTRODUCTION

This appendix presents the shipments and incremental cost data submitted to the U.S. 

Department of Energy (DOE) by the Association of Home Appliance Manufacturers (AHAM) in 

support of the engineering analysis for this rulemaking. See chapter 5 of the technical support 

document (TSD) for details of the engineering analysis for which these data were used.

5A.2 AHAM MICROWAVE OVEN DATA SUBMITTAL

AHAM submitted the following microwave efficiency and standby test data and report to 

DOE on October 23, 2006.

October 23, 2006

Mr. Michael Rivest

Managing Director

Navigant Consulting, Inc.

1801 K Street, NW, Suite 500

Washington, D.C. 20006- 1301

Subject: AHAM Test Data on Microwave Ovens 

Summary: 

The Association of Home Appliance Manufacturers is the trade association representing the 

manufacturers of over 95% of the microwave ovens sold in the U.S. To assist the Department of Energy 

in its rulemaking for Microwave Ovens (MWOs), AHAM commissioned the independent testing at 

Intertek/ETL of 22 randomly selected MWOs (provided by 7 different manufacturers). The ovens 

represented a broad spectrum of units presently in the market place, and varied by size, power rating, 

components, and features.
5A-2

The tests were conducted using the DOE test procedures prescribed in 10 CFR Part 430 Appendix I, 

which references IEC Standard 705-1988 with Amendment 2-1993. The results of the tests are shown in 

the file embedded below. Each unit was tested 3 times. The average Energy Factor of the 3 runs for each 

unit is highlighted in yellow in the embedded file.

[File reproduced at the end of this letter]

The test results show that there is a very narrow range in energy efficiency between the least and most 

efficient unit (54.8% minimum to 61.8% maximum - less than a 13% spread). Using the annual useful 

cooking energy output of 79.8kWh/yr, as determined by DOE in its September 8, 1998 rulemaking, this 

range in efficiencies results in a difference of only about 16 kWh/yr (which is about $1.60/yr) between the 

least and most efficient unit.

The September 8, 1998 Final Rule on cooking products states that, “DOE has determined that there would 

be no significant conservation of energy for ... microwave ovens, and standards would not be 

economically justified.”a

 We believe the test data and information provided herein confirms that an

efficiency standard for MWOs is still not warranted.

DOE considered many design options for microwave ovens in its 1998 rule, and after extensive analysis, 

it was determined that no design options were technology feasible or economically justifiable. There 

have been no technological or economic breakthroughs since the previous determination which would 

change the previous conclusion. 

Factors and Features Impacting Efficiency:

There are many factors that impact the efficiency of MWOs, and many different features that are driven

by the demands of the marketplace. These features determine the need for components that consume 

electrical energy or absorb microwave energy during operation. Common components that affect the 

energy efficiency are shown in the table below:

Turntable motor Waveguide & cavity Magnetron tube

Stirrer motor Glass turntable High Voltage Transformer

Cavity lamp Turntable roller High Voltage Diode

Fan motor Turntable hub High Voltage Capacitor

Display, relays, & electronics Stirrer blade

Many of the components listed above may impact the energy consumption differently, depending upon 

the specific oven features and application. For example, an Over-The-Range (OTR) oven may require a 

larger cooling fan motor than a counter-top oven. This is because the ambient air at the OTR air inlet is at 

an elevated temperature due to the range beneath being in operation.

Wattage of the cavity lamp is another example. The consumer desires brightly illuminated oven cavities. 

Increasing the wattage of the lamp by only 10 watts could lower the efficiency of an oven by about 0.5%. 

Some manufacturers may choose higher wattage lamps for product differentiation.

 

a 63 Fed. Reg. 48,038 (Tuesday, September 8, 1998).
5A-3

Manufacturers do not optimize the efficiency of their designs around the DOE test procedure, which calls 

for a simplified method of heating one liter of water in the center of the oven. Rather, ovens are designed 

to heat various sizes, shapes, and types of food most efficiently and evenly. Again, consumer needs are 

the key drivers on MWO design.

For example, designers often use a stirrer to improve cooking performance as determined by Consumer 

Union testing in categories such as thermal uniformity and defrosting. The stirrer is a rotating device 

used to vary how the electromagnetic field is applied to the food in the oven cavity. As the stirrer sweeps 

through its rotation, the magnetron’s frequency and efficiency also change. The net effect is to improve 

cooking performance for the consumer, in exchange for a small decrease in oven efficiency.

Design Options:

In DOE’s March 15, 2006 Framework Document, several design options are listed for microwave ovens 

as possible considerations to improve energy efficiency. We offer the following comments on those 

design options:

• Add insulation – This is not a practical option, as it would not improve the Energy Factor. The 

DOE test is only about 45 seconds in duration and the temperature of the oven walls does not 

increase during use, thus no significant energy would be saved by adding insulation. It is likely 

that the net result would not even be measurable.

• Reflective surfaces – Manufacturers are already using surface finishes to optimize efficiency. If 

DOE is referring to the possibility of adding metallic plates inside the oven cavity to adjust cavity 

impedance to the highest oscillation impedance of the magnetron, this is best accomplished by 

better oven design without such metallic plates.

• More efficient fan – A typical fan only draws about 30 watts, resulting in less than 2% of the total 

energy consumed during the DOE test. Therefore, improving the fan efficiency by going to more 

expensive motors would at best improve the energy factor by less than 0.5%. Thus more efficient 

fans motors are not economically justified.

• Improve efficiency of magnetron – The magnetron tube is the heart of the MWO. As such, 

considerable engineering effort has already gone into optimizing their efficiency, and there is 

very little difference in available technologies. Virtually all magnetrons are the same. A review 

of magnetron manufacturers’ specifications shows that the typical efficiency is about 73%, with 

only a plus or minus 2% variance. Thus, there is no available technology for improvement.

• Improve efficiency of the power supply – There are two types of high voltage power supplies that 

are used in MWOs. The predominant type is the inductive capacitance transformer, known as the 

LC power supply, which has an efficiency of about 82%. The other type is the inverter type, 

which is more expensive, and has an efficiency of about 84%. (General purpose transformers 

have higher efficiencies, but the need for stable output power in MWOs requires the use of 

special transformers which have inherently lower efficiencies.) 

Three of the units tested utilized an inverter type power supply, whereas all others used the more 

typical LC transformer. Even though inverter power supplies are slightly more efficient than LC 

types, the Energy Factors of the 3 units with an inverter were right around the median of all the 

units tested. They ranged around 56% to 59%, with the average of the 3 units being 58%. 
5A-4

Therefore, the use of an inverter as a design option does not necessarily improve efficiency. We 

see no cost effective opportunity for improving the efficiency of the power supply. 

• Eliminate or improve ceramic stirrer cover – Virtually no residential solo-function microwave 

ovens still use a ceramic stirrer. Almost all MWOs use a polypropylene or mica film, which are 

low energy loss materials resulting in less losses than the ceramic type. Thus this design option 

has already been optimized.

• Modify wave guide – We are not aware of any improvement to the wave guide that would result 

in any significant increase in energy efficiency. Losses associated with the wave guide are 

typically less than 0.5% of the overall energy consumption.

• Dual magnetrons – This would not be an effective way to improve energy efficiency since 

magnetrons require energy to heat the magnetron heater. This energy is not converted to 

microwave energy, and thus is wasted. Thus, the more magnetrons used, the more wasted energy 

is consumed, not to mention the additional cost of extra magnetrons.

Standby Power:

Standby power was measured on all the ovens tested, in accordance with IEC Standard 62301-2005, 

Household electrical appliances – Measurement of standby power. The measurements ranged between 

1.5 and 5.8 watts, with an average of 2.9 watts. Each watt of standby power is approximately 8.7 kWh/yr, 

which amounts to about 85 cents/yr. Even if DOE limited the standby power of MWOs to 2 watts, it 

would only result in less than a dollar per year savings on average per unit.

There are three major types of displays used in microwave ovens today. They are LED (light emitting 

diodes), VFD (vacuum fluorescent display) and LCD (liquid crystal display). Typically, LCD without 

back-lighting uses the least amount of energy while VFD uses the most. Energy consumed by LCD 

would depend on whether back-lighting is present or not. And if present, the number of LEDs used for 

back-lighting is a major factor in energy consumption.

For LEDs, the number of segments, color and operating temperature has an impact on its 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 display is a major factor in its energy consumption. 

The type of display used, its size, and type of back-lighting, etc., all have a direct impact on the product’s 

appeal to the consumer. Thus, while an LCD without back-lighting may be most energy efficient, it may 

not have as much consumer appeal as a VFD, which is typically the best from a legibility perspective. 

Manufacturers (driven by consumer/market desires) want the flexibility to produce microwave ovens 

using the various displays described above in order to provide products with market differentiation, in 

turn meeting the diverse needs of consumers. This is the reason for the variance in the test results for 

measured standby power. Therefore, AHAM recommends that standby power not be considered as a 

separate prescriptive requirement. 

Conclusion:

All the ovens we tested were within a relatively narrow efficiency range without any current energy 

standards in effect. The tests indicated a range in efficiencies that results in a difference of only about 16 
5A-5

kWh/yr (which is about $1.60/yr) between the least and most efficient unit. This narrow range of 

efficiencies is a result of optimization of current cost effective design options and market competition to 

produce high quality microwave ovens at low prices for the consumer, while still being able to offer 

ample product features and differentiation. 

Efficiency standards for microwave ovens are not justified, as very little energy savings would result. 

The cost and risk of modifying today’s well-performing products with questionable design options should 

not be underestimated. Microwave ovens are much more efficient than conventional cooking products, 

and their use should be encouraged, not discouraged by adding cost to the products for very little overall 

energy savings benefit.

Therefore, we recommend that a “No Standard, Standard” be re-established for these products and 

that significant resources not be expended to conduct unnecessary analyses. Sufficient data and 

precedent exists to support and affirm DOE’s previous conclusion that standards for MWOs are not 

justified. DOE and industry resources would be better spent on expediting other rulemakings.

Thank you for the opportunity to provide this information. Please feel free to contact me with any 

questions that you might have. 

Sincerely,

Lawrence R. Wethje, P.E.

Vice President, Technical Services
5A-6

Figure 5A.2.1 AHAM Standby Power Test Data

Client: AHAM

Project No.: 3100653

Microwave Oven Re-Testing: 09/20-22/06

Tested per IEC 705-1988 and Amendment 2-1993

Unit

No.

Rated

Volume

(ft3)

Humidity

Sensor

(Y/N)

Rated 

Watts

Mw ,

(g)

Mc,

(g)

T0,

(oC)

T1,

(oC)

T2,

(oC)

t,

(Sec.) Win

Watts @ 

20 Sec.

P,

(Watts)

EF,

(%)

SP,**

(Watts)

1000 515 20.8 10.0 19.5 52 18.9 1292 753.6 58.3

1000 515 19.6 10.4 19.7 52 18.8 1286 749.7 58.3

1000 515 19.9 10.0 19.1 52 18.8 1292 725.8 56.2

57.6

1005 515 19.5 10.4 19.9 35 18.4 1875 1147.3 61.2

1000 515 21.9 11.7 21.3 35 18.4 1876 1140.7 60.8

995 515 20.8 10.5 20.2 35 18.3 1872 1146.8 61.3

61.1

1000 515 18.9 9.8 20.0 42 20.0 1730 1028.7 59.5

1000 515 19.5 10.1 20.3 42 20.1 1735 1025.5 59.1

1000 515 19.9 10.4 20.3 42 19.7 1705 991.3 58.1

58.9

1000 515 19.5 10.1 19.9 42 19.6 1696 981.3 57.9

1000 515 20.7 10.5 20.2 42 19.7 1704 961.6 56.4

995 515 20.5 10.5 20.3 42 19.4 1678 969.9 57.8

57.4

1000 515 20.7 10.8 20.4 42 19.1 1604 953.8 59.5

1000 515 19.3 10.1 19.8 42 19.1 1602 972.4 60.7

1000 515 19.2 9.9 19.8 42 19.1 1607 993.4 61.8

60.7

1000 515 19.1 10.1 20.1 35 19.6 1946 1209.2 62.1

1005 515 19.2 10.1 20.1 35 19.6 1951 1213.9 62.2

1000 515 21.1 10.8 20.8 35 19.6 1950 1192.4 61.1

61.8

1000 515 19.2 9.8 18.8 32 17.6 1988 1171.9 59.0

995 515 20.4 10.2 19.4 32 17.6 1986 1183.6 59.6

1000 515 20.8 10.8 19.8 32 17.5 1984 1163.4 58.6

59.1

1000 515 21.3 11.0 20.4 34 18.7 2010 1145.6 57.0

1000 515 19.6 10.6 19.9 34 18.8 2010 1149.3 57.2

1000 515 20.0 10.7 19.9 34 18.8 2010 1131.6 56.3

56.8

1005 515 18.7 9.3 18.6 34 18.8 2008 1149.7 57.3

995 515 19.3 9.8 19.3 34 18.7 2006 1164.0 58.0

1000 515 19.2 9.7 19.3 34 19.1 2009 1183.5 58.9

2.2 Y Average: 58.1

1.2 Y 1300 Average: 2.0

1.6 Y 1200 Average: 3.7

1.6 N

9

8 Average:

1.5

3.0

3.9

4.2

Average:

Average:

Average:

Average:

1.2 N 1.8

1250 2.2

1250 2.9

Average:

N 1200

1.6*

1000

1.6*

1.5

Y 1000

N 800

N 1000

1 0.8

3

4

5

2

6

7
5A-7

1000 515 19.6 10.0 19.8 60 20.2 1216 685.4 56.4

1000 515 21.8 11.8 21.3 60 20.3 1218 659.2 54.1

1000 515 21.7 11.8 21.4 60 20.0 1210 667.7 55.2

55.2

1000 515 19.7 10.1 20.3 60 20.0 1192 716.3 60.1

1000 515 21.6 11.4 21.4 60 19.6 1180 696.3 59.0

1000 515 21.7 11.1 21.0 60 19.6 1176 685.6 58.3

59.1

1000 515 21.8 11.3 21.0 42 19.8 1690 958.4 56.7

1000 515 19.2 10.1 19.9 42 20.1 1712 984.5 57.5

1000 515 19.6 10.0 19.6 42 19.6 1668 957.0 57.4

57.2

1000 515 18.5 9.1 19.2 38 20.9 1934 1121.2 58.0

1000 515 19.1 9.9 20.1 38 20.9 1959 1135.8 58.0

1000 515 19.1 9.9 19.8 38 20.6 1909 1099.2 57.6

57.8

1000 515 19.8 8.9 19.0 42 19.9 1670 998.2 59.8

1000 515 21.7 11.3 21.1 42 20.3 1686 970.5 57.6

1000 515 21.0 10.4 20.4 42 20.2 1683 990.4 58.8

58.7

1000 515 18.9 9.7 20.0 42 19.7 1672 1038.7 62.1

1000 515 19.1 10.1 20.3 42 19.7 1675 1029.8 61.5

1000 515 20.4 10.2 20.4 42 19.8 1676 1016.8 60.7

61.4

1000 515 19.5 10.0 20.0 52 21.0 1421 809.6 57.0

1000 515 21.7 11.2 21.1 52 20.6 1402 791.9 56.5

1000 515 21.6 11.0 20.8 52 20.6 1402 782.1 55.8

56.4

995 515 19.6 10.5 20.3 35 18.7 1878 1175.6 62.6

1000 515 21.1 11.1 20.7 35 18.6 1874 1143.3 61.0

1000 515 21.0 10.6 20.2 35 18.6 1875 1138.1 60.7

61.4

1000 515 21.3 10.6 20.7 42 20.8 1740 1000.4 57.5

1000 515 19.4 9.7 19.8 42 20.8 1745 1011.2 57.9

1005 515 20.0 10.5 20.3 42 20.8 1745 985.1 56.5

57.3

1000 515 19.4 9.2 18.8 42 19.9 1668 950.6 57.0

1000 515 20.7 10.3 19.7 42 19.8 1669 926.3 55.5

1000 515 21.3 11.6 20.8 42 19.8 1668 911.8 54.7

55.7

1000 515 20.0 10.7 20.2 38 21.1 1936 1049.1 54.2

1005 515 20.0 9.6 19.4 38 21.1 1941 1078.0 55.5

1000 515 20.1 10.0 19.6 38 20.8 1922 1051.8 54.7

54.8

1000 515 20.2 10.6 20.3 44 20.5 1630 924.1 56.7

995 515 21.1 11.1 20.6 44 20.5 1628 894.3 54.9

1000 515 19.9 10.4 19.9 44 20.2 1623 904.0 55.7

55.8

Legend:

P - is the microwave power output, in watts

M w - is the mass of the water, in grams

M c - is the mass of the container, in grams

T0 - is the ambient temperature, in degrees Celsius

T1 - is the initial temperature of the water, in degrees Celsius

T2 - is the final temperature of the water, in degrees Celsius

t - is the heating time, in seconds, excluding the magnetron filament heating-up time

Average:

Average:

Y 1000

1000

N 1000

Average:

Average:

Average:

Average:

0.7 N

Y 1100

1000

Average:

Average:

Average:

N

DAMAGED UNIT!!!!!

5.8

22 1.4* N 950 2.6

1.5* Y 1100 Average:

Average:

21

4.4

20 1.0 N 1000 1.7

19 1.5

2.0

18 1.5 N -

1.2 N 1200 Average:

Average:

17

1.8

16 0.8* Y 800 5.7

15 1.1

3.6

14 0.9*

Not

Listed 1000 2.0

13 2.0

0.7 700 2.0

2.1

1.9

700

12 1.6 N

10

11
5A-8

Win - is the energy input, in watt-hours

EF - is the Energy Factor, or efficiency, in percent

SP - is the standby power, in watts 

All tests were performed at 120 Vac, 60 Hz

* - Physical measurement performed by ETL

** - M easured with the microwave clock set to 12:00 and with door closed.