APPENDIX 6A. COOKTOPS AND OVENS: DETERMINATION OF ENERGY-USING COMPONENTS

TABLE OF CONTENTS

6A.1 INTRODUCTION .................................................................................................. 6A-1 6A.2 METHODOLOGY FOR DISAGG REGATING ELECTRIC RANGE ANNUAL ENERGY CONSUMPTION................................................................. 6A-1 6A.3 METHODOLOGY FOR ESTABLISHING GAS COOKING ENERGYUSING COMPONENTS ........................................................................................ 6A-4

LIST OF TABLES

Table 6A.2.1 Electric Cooking Products: Energy-Using Components............................ 6A-4 Table 6A.3.1 Gas Cooking Products: Energy-Using Components.................................. 6A-6

6A-iAPPENDIX 6A. COOKTOPS AND OVENS: DETERMINATION OF ENERGY-USING
COMPONENTS

6A.1 INTRODUCTION

As presented in Chapter 6, section 6.4.1.2, based on recent survey data, DOE determined that the representative annual energy consumpti on of an electric range is 281.5 kWh per year. Because DOE’s analysis of cooking products co nsisted of analyzing oven and cooktop product classes, DOE had to disaggregate the range ener gy consumption into the portion allocated to the oven and the portion allocated to the cooktop. In addition, because oven and cooktop energy use may consist of several energy-using components (i .e., cooking, ignition, self -cleaning, and clock) and potential increases in effici ency may affect only a subset of these components, DOE had to further disaggregate the oven and cooktop energy consumption into its specific energy-using components. The following sections deta il: (1) DOE’s method for disaggregating the representative electric range energy consumption into the vari ous energy-using components of electric ovens and cooktops; a nd (2) DOE’s method for establis hing the representative energy use of gas cooking product energy-using components based on the values that were determined for the electric cooking product energy-using components.

6A.2 METHODOLOGY FOR DISAGGR EGATING ELECTRIC RANGE
ANNUAL ENERGY CONSUMPTION

As noted above, DOE determined that the re presentative annual energy consumption of an electric range is 281.5 kWh per year. Based on the following equation, DOE assumed the energy consumption was equal to the sales weighted-average of standard and self-cleaning oven energy consumption plus the cook top energy consumption. Also included is the clock power associated with electric ovens.

UEC elec cooking = 281

. 5 kWh / yr

_ = MSe SC × 

# ( E CO _ SC + Ees × S
e 

# ) + 

# ( 1 MSe SC 

# ) × E CO

_ STD + E CA + 

## ( P

CL ×8760× 0

. 001 

## )

where:

UEC elec cooking = Annual energy consumption of electric cooking (kWh/yr), MSe SC = Market share of electric ove ns that are self-cleaning, 63.2%, 1

E CO_SC = Annual cooking energy consumption of self-cleaning electric ovens (kWh/yr), Ees = Typical self-cleaning energy consum ption per cycle for electric selfcleaning ovens, 5.286 kWh (as report ed in Chapter 6, Table 6.4.7), S e = Number of self-clean cycles per year for electric se lf-cleaning ovens according to the DOE test procedure, 4, 2

6A-1E CO_STD = Annual cooking energy consumpti on of standard electric ovens (kWh/yr), E CA = Annual energy consumption of electric cooktops (kWh/yr), P CL = Power input to clock (watts), 2, a 8760 = Hours in a year, and 0.001 = Conversion to convert watts in kW.

DOE estimated the annual cooking energy cons umption of electric self-cleaning ovens as a fraction of the cooking energy consumption of a standard electric oven. The annual cooking energy consumption of cooktops was also estim ated as a fraction of the cooking energy consumption of standard ovens. These fracti ons were taken from the ratios of energy consumption as established by the DOE test pro cedure. The following equations represent the calculations used by DOE:

= E CO _ SC Re SC _ STD × E CO

_ STD

E = Re × E

CA CT _ STD CO _ STD

where:

Re SC_STD = Ratio of annual self-cleaning electric oven cooking energy to annul standard electric cooking energy, and Re CT_STD = Ratio of annul electric cooktop cooking energy to annual standard electric oven cooking energy.

To calculate each of the a bove ratios, DOE took the annual useful cooking energy output values from the DOE test pro cedure and divided them by the ba seline cooking efficiencies reported in Chapter 6, Table 6.4.1. For cooktops, this assumes that the ratio of the cooktop and oven annual useful cooking energy output value has not changed significantly over time, even though there has been a decrease in the annual energy consumption of el ectric cooking products. 

## ( O O EFFeo SC 

## ) = 0

. 881 Re SC _ STD = 

## ( O O EFFeo STD 

## )
( EFFe CT 

## ) O CT = 0

. 971 Re CT

_ STD = 

## ( O O EFFeo STD 

## )

where:

a DOE assumed a clock power consumption of 2 watts for purposes of disaggregating the electric range annual energy consumption into its energy-using components. As reported in Chapter 6, the baseline clock power consumption for electric standard and self-cleaning ovens are 3.9 watts and 3.8 watts, respectively. 6A-2O O = Annual useful cooking energy out put for ovens according to the DOE test procedure, 29.3 kWh, 2
O CT = Annual useful cooking energy output for cooktops according to the DOE test procedure, 173.1 kWh, 2

EFFeo SC = Cooking efficiency of the baseline self-cleaning electric oven, 13.79%, EFFeo STD = Cooking efficiency of the baseline standard electric oven, 12.15%, and EFFe CT = Cooking efficiency of the ba seline electric cooktop, 74.0%.

The baseline cooking efficiency of electric cooktops (74%) is the sales weighted-average efficiency of coil and smooth cooktops.

_ EFFe = MSe × EFFe + 

# ( 1 MSe 

# ) × EFFe CT COIL CT _COIL COIL CT _ SMTH

where:

MSe SC = Market share of electric cooktops that are coil, 46.3%, 1

EFFe CT_COIL = Cooking efficiency of the baseli ne electric coil cooktop, from the cost/efficiency table, 73.7%, and EFFe CT_SMTH = Cooking efficiency of the baseli ne electric smooth cooktop, from the cost/efficiency table, 74.2%.

With both the annual cooking energy consump tion of self-cleaning electric ovens and electric cooktops expressed as a function of standard electric oven annual cooking energy consumption, DOE solved for the standard el ectric oven annual cooking energy consumption by the using the following equation:

281

. 5 MSe × Ees × S P ×8760× 0

. 001 SC e CL E = _ _

CO _ STD

_ MSe × Re +1 MSe + Re SC SC _ STD SC CT _ STD
281

. 5 63

. 2 % ×5

. 286× 4 2×8760× 0

. 001

= _ _ = 132

. 4 kWh / yr

_ 63

. 2 % × 0

. 881+1 63

. 2 % + 0

. 971

With the standard electric oven annual cooking energy consumption established ( E AO_STD ), DOE solved for the self-cleaning el ectric oven and cooktop annual cooking energy consumption values by usi ng the following equations:

E = Re × E

CO _ SC SC _ STD CO _ STD = 0

. 881×132

. 4 = 116

. 6 kWh / yr

E = Re × E

CA CT _ STD CO _ STD = 0

. 971×132

. 4 = 128

. 3 kWh / yr

6A-3Table 6A.2.1 summarizes the energy-usi ng components of electric cooking products. Also provided are the annual useful cooking en ergy output values—one set based on the DOE test procedure and another set deduced from the lower annual energy consumption values.

Table 6A.2.1 Electric Cooking Products: Energy-Using Components Energy-Using Components Cooktop St andard Oven Self-Cleaning Oven Cooking Efficiency 74.0% 12.15% 13.79% Cooking Energy (kWh/yr) 128.2 132.4 116.6 Self-Cleaning Energy (kWh/yr) 21.1
Clock (kWh/yr)* 34.2 33.3 Total (kWh/yr) 128.2 166.5 171.0 Annual Useful Cooking Energy Output (O CT for cooktops; O O for ovens)

Current DOE test procedure (kWh) 173.1 29.3 29.3 Based on electric range annual cooking energy of 281.5 kWh/yr (kWh) 94.8 16.1 16.1

* Clock energy based on clock power of 3.9 W for standard ovens and 3.8 W for self-cleaning ovens.

6A.3 METHODOLOGY FOR ESTABLISHING GAS COOKING ENERGY

USING COMPONENTS

DOE estimated the annual energy consum ption of gas cooking products based on the lower (revised) annual useful cooking energy output values that DOE deduced from the electric range annual energy consumption of 281.5 kWh per year. As represented by the following equations, DOE assumed that the ratio of the revised-to-current annua l useful energy output values for electric cooking products a pplied to gas cooking products as well:

O O

_ ELEC

_ REV 16

. 1 kWh O = O × = 88

. 8 kBtu × = 48

. 7 kBtu

O _GAS

_ REV O _GAS

_ DOE O 29

. 3 kWh O

_ ELEC

_ DOE

O CT _ ELEC _ REV 94

. 8 kWh O = O × = 527

. 6 kBtu × = 288

. 9 kBtu

CT _GAS

_ REV CT _GAS

_ DOE O 173

. 1 kWh CT _ ELEC _ DOE

where:

O O_GAS_REV = Revised annual useful co oking energy output for gas ovens, O O_GAS_DOE = DOE test procedure annual useful cooking energy output for gas ovens, O O_ELEC_REV = Revised annual useful cooking energy output for electric ovens, O O_ELEC_DOE = DOE test procedure annual useful cooking energy output for electric

ovens, O CT_GAS_REV = Revised annual useful cooki ng energy output for gas cooktops,

6A-4O CT_GAS_DOE = DOE test procedure annual us eful cooking energy output for gas cooktops, O CT_ELEC_REV = Revised annual useful cooking ener gy output for electric cooktop, and O CT_ELEC_DOE = DOE test procedure annual useful cooking energy output for electric cooktops.

With the revised annual useful cooking output values known for gas cooking products, DOE used the following test procedure equa tions to calculate the annual cooking energy consumption of gas cooking products. In the eq uations below, DOE used the baseline cooking efficiencies reported in Chapter 6, Table 6.4.1.

O O _GAS

_ REV 48

. 7 kBtu E CO

_ SC _GAS = = = 683

. 5 kBtu / yr EFFgo SC 7

. 13 %

O O _GAS

_ REV 48

. 7 kBtu E CO

_ STD _GAS = = = 822

. 6 kBtu / yr EFFgo STD 5

. 92 %

O CT _GAS

_ REV 288

. 9 kBtu E CC _GAS = = = 724

. 4 kBtu / yr EFFg CT 39

. 9 %

where:

E CO_SC_GAS = Annual cooking energy consumpti on of gas self-cleaning ovens, EFFgo SC = Cooking efficiency of the baseli ne self-cleaning gas oven, 7.13%, E CO_STD_GAS = Annual cooking energy consumption of gas standard ovens, EFFgo STD = Cooking efficiency of the base line standard gas oven, 5.92%, E CC_GAS = Annual cooking energy consumption of gas cooktops, and EFFg CT = Cooking efficiency of the baseline gas cooktop, 39.9%.

Table 6A.3.1 summarizes the energy-using components of gas cooking products. Also provided are the annual useful cooking energy output values—one set based on the DOE test procedure and the other based on the revised set of va lues. Ignition, self -cleaning, and clock energy consumption values are described and repor ted in Chapter 6, Tables 6.4.5, 6.4.8, and 6.4.9 for gas cooktops, standard ovens, and self-cleaning ovens, respectively.

6A-5Table 6A.3.1 Gas Cooking Products: Energy-Using Components

Energy-Using Components Cooktop Standard Oven SelfCleaning

Oven With pilot Without pilot With pilot Without pilot Cooking Efficiency 39.9% 39.9% 5.92% 5.92% 7.13% Cooking Energy (MMBtu/yr) 0.72 0.72 0.82 0.82 0.68 Self-Cleaning Energy Gas (MMBtu/yr) 0.17 Electric (kWh/yr) 0.7 Ignition Gas (MMBtu/yr) 2.02 1.01 Electric (kWh/yr) 21.1 21.1
Clock (kWh/yr)* 31.5

Total Gas (MMBtu/yr) 2.74 0.72 1.83 0.82 0.85 Electric (kWh/yr) 21.1 55.1 Annual Useful Cooking Energy Output (O CT for cooktops; O O for ovens)

Current DOE test procedure (kBtu) 527.6 88.8 88.8 Revised values (kBtu) 288.9 48.7 48.7

* Clock energy based on clock power of 3.6 W for self-cleaning ovens.

6A-6REFERENCES

1 Association of Home App liance Manufacturers. AHAM Data on Cooking Products for Efficiency Standards Rulemaking, August 23, 2006. Letter to Building Technologies Program, U.S. Department of Energy.

2 U.S. Office of the Federal Register. Code of Federal Regulations, Title 10, Energy. Part 430, Subpart B, Appendix I: Uniform Test Method fo r Measuring the Energy Consumption of Conventional Ranges, Conven tional Cooking Tops, Conven tional Ovens, and Microwave Ovens, 2006. Washington, DC.

6A-7