APPENDIX 7-C. LCC ENERGY USE CALCULATIONS 

TABLE OF CONTENTS 

7-C.1	 INTRODUCTION ....................................................................................................... 7-C-1


7-C.2	 WATER HEATERS .................................................................................................... 7-C-1


7-C.2.2 WHAM Equation....................................................................................... 7-C-1


7-C.2.3 WHAM Equation for Heat Pump Water Heaters ...................................... 7-C-4


7-C.2.3.1 Comparison of energy use calculations for heat pump water heaters........ 7-C-7


7-C.2.3.2 Calculating HPWH Cooling Effects .......................................................... 7-C-8


7-C.2.4 WHAM Equation for Gas Instantaneous Water Heaters ......................... 7-C-11


7-C.3 POOL HEATERS ...................................................................................................... 7-C-13


7-C.4 DIRECT HEATING EQUIPMENT .......................................................................... 7-C-13


LIST OF TABLES 

Table 7-C.2.1 Comparison of HPWH Energy Use Results .............................................. 7-C-8


LIST OF FIGURES 

Figure 7-C.2.1 Methodology for Calculating Energy Consumption for Water Heaters .... 7-C-1 

Figure 7-C.2.2 Methodology for Calculating Storage WH Energy Consumption using 

WHAM Equation....................................................................................... 7-C-3 

Figure 7-C.2.3 Methodology for Calculating Electricity and Fuel Consumption for 

Gas and Oil Storage Water Heaters ........................................................... 7-C-4 

Figure 7-C.2.4 Methodology for Calculating HPWH Energy Consumption using 

Modified WHAM Equation ....................................................................... 7-C-5 

Figure 7-C.2.5 Methodology for Calculating HPWH Cooling Effects.............................. 7-C-9 

Figure 7-C.2.6 Methodology for Calculating Instantaneous WH Energy Consumption 

using Modified WHAM Equation ........................................................... 7-C-12


7-C-i 

EE-2006-STD-0129 and EERE-2006-BT-STD-0129 COMMENT 32.2
APPENDIX 7-C. LCC ENERGY USE CALCULATIONS 

7-C.1 INTRODUCTION 

This appendix contains the calculation methodology for calculating the energy use of 

residential water heaters, direct heating equipment, and pool heaters in the LCC Analysis. 

7-C.2 WATER HEATERS 

1 Water heaters energy consumption is calculated using the WHAM equation. Figure 7­

C.2.1 shows the methodology for calculating energy consumption for water heaters. 

Engineering 

Analysis 

Average Yearly Tank 

Temperature 

(Distribution) 

Average Monthly 

Inlet Water 

Temperature 

Average Daily Hot 

Water Use 

Operating 

Conditions 

Contractor 

Survey 

Weather 

Data 

Average Monthly 

Ambient 

Temperature 

Draw Model 

RECS 

Sample 

Equipment 

Type 

WHAM 

Modified WHAM 

for HPWHs 

Storage WH 

HP WH 

Monthly Energy 

Use 

Data Sources 

RE 

EF 

UA 

RECS Household 

Sampled 

WHAM Calculations depedent on 

Equipment Type 

Inlet Water 

Temp 

Methodolog 

y 

Well? 

Equipment Parameters 

Pon 

Modified WHAM 

for Tankless WHs 

Figure 7-C.2.1 Methodology for Calculating Energy Consumption for Water Heaters 

7-C.2.2 WHAM Equation 

1 The WHAM equation yields average daily water heater energy consumption (Qin), and is 

expressed as follows: 

7-C-1 

EE-2006-STD-0129 and EERE-2006-BT-STD-0129 COMMENT 32.2
⎛

⎟ +

⎞

⎟

⎠

(T in ) (T amb vol × den C
 × × − T
 UA
× − T
 ) P tank tank 1
− 24 (T amb Q
 ) in = ∗ ⎜ ×UA
× − T
 ⎜

⎝ tank RE
 P on 

Where: 

Qin = total water heater energy consumption, Btu/day,


RE = recovery efficiency, %,


Pon = rated input power, Btu/h,


UA = standby heat-loss coefficient, Btu/h-oF,


Ttank = thermostat setpoint temperature, oF,


Tin = inlet water temperature, oF,


Tamb = temperature of the air surrounding the water heater, o

F,


vol = volume of hot water drawn in 24 hours, gal/day,


den = density of stored water, set constant at 8.29 lb/gal, and


Cp = specific heat of stored water, set constant at 1.000743 Btu/lb-o

F.


WHAM yields total water heater energy consumption (Qin ), which is the sum of fuel and 

electricity consumption. For gas-fired storage water heaters, gas-fired instantaneous water 

heaters, and oil-fired storage water heaters, it is necessary to disaggregate the electricity and fuel 

consumption. Figure 7-C.2.2 shows the methodology for calculating electricity and fuel 

consumption using WHAM. DOE calculated electricity consumption as follows: 

Qelecttricity = Qin × (Paux − Ps tan dy )− Ps tan dy × 24 

PON 

Where: 

Qelectricity = electricity consumption, kWh,


Qin = total water heater energy consumption, Btu/day,


PON = rated input power, kW,


Paux = electricity demand when burner is on, kW, and


Pstandy = electricity demand when burner is off, kW.


7-C-2 

EE-2006-STD-0129 and EERE-2006-BT-STD-0129 COMMENT 32.2
Average Yearly Tank 

Temperature 

(Distribution) 

Average Monthly 

Inlet Water 

Temperature 

Average Daily Hot 

Water Use 

Average Monthly 

Ambient 

Temperature 

Draw Model 

Mode 

Energy 

Consumption During Water 

Heating 

Energy 

Consumption 

During Standby 

Water Heating 

Standby 

Average Daily 

Total Energy Use 

for Month 

RE 

UA 

WHAM Calculation 

Pon 

Heat Capacity of 

Water Density of Water 

Average Monthly Temperature Difference 

Water Heater Heating Load 

Test Procedure 

Parameters 

WH ON = 24 hrs 

EF 

FueEle

Gas and 

WHs has 

and E

Figure 7-C.2.2 Methodology for Calculating Storage WH Energy Consumption using WHAM 

7-C-3 

EE-2006-STD-0129 and EERE-2006-BT-STD-0129 COMMENT 32.2
DOE calculated gas consumption by subtracting electricity consumption from total water 

heater energy consumption (Qin ). Figure 7-C.2.3 shows the methodology for calculating 

electricity and fuel consumption for gas and oil storage water heaters. 

Pstandby 

Mode 

Electricity 

Consumption Due 

to Water Heating 

Energy 

Consumption 

During Standby 

Water Heating 

Standby 

Paux 

(electronic ignition, 

controls, fan use) 

Pon 

Average Daily Elec 

Use for Month 

Average Daily 

Total Energy Use 

for Month 

Fuel Use 

Figure 7-C.2.3	 Methodology for Calculating Electricity and Fuel Consumption for Gas 

and Oil Storage Water Heaters 

7-C.2.3 WHAM Equation for Heat Pump Water Heaters 

For heat pump water heaters, energy efficiency and consumption is dependent on the 

ambient temperature. To account for this, DOE expanded the WHAM to utilize the calculation 

approach used in the NYSERDA Heat Pump Water Heater Site Screening Tool and DOE’s 

weatherization assistance program.2, 3 The equation for determining the energy consumption of 

heat pump water heaters is similar to WHAM, but the RE is adjusted with a performance 

adjustment factor, which is a function of the average ambient temperature. A heat pump water 

heater operates either in heat pump mode or in electric resistance mode. DOE assumed that 

electric resistance mode of operation is used 100 percent when the monthly ambient temperature 

is below 32 oF. A heat pump water heater also operates in the electric resistance mode for part of 

the time even when the monthly ambient temperature is above 32 o

F, due to the slower recovery 

rate of heat pump water heater compared to an electric resistance water heater. DOE determined 

that depending on household hot water consumption patterns, this type of operation occurs up to 

10 percent of the unit’s operating time. Figure 7-C.2.4 shows the methodology for calculating the 

energy consumption of HPWHs using the modified WHAM equation. 

7-C-4 

EE-2006-STD-0129 and EERE-2006-BT-STD-0129 COMMENT 32.2
Average Daily Hot 

Water Use 

Average Monthly 

Ambient 

Temperature 

Draw Model 

Mode of 

Operation 

WHAM 

Resista

WHA

Pum

Electric 

Resistance 

Mode 

HP Mode 

Heat Pump Load 

Factor (% Energy 

Use at HP Mode) 

REElectri

EF = 2.2 @ 50 Gal 

Tank 

ECR Model 

Data 

REHeat Pump. = 242% 

UA = 1.82 

RECS Sampled 

Household 

RE Adjustment 

Factor 

Test Data 

(John 

Maxwell) 

Monthly 

Calculation of 

HPWH Runtime 

Fraction 

1% ER runtime per 

9500 Btu of Daily 

Hot Water Load 

Engineering 

Spreadshee 

t 

Test Data/ 

Assumption 

PON,Electric. Res. = 4.5 

kW 

PON,HPWH = .5 kW 

Above 32 F? YES (Calculate) 

HP Load = 

Adjusted RE * 

PON 

ER Load = RE * 

PON 

NO (0% HP Mode) 

ECR Model 

Data 

ECR Model 

Data 

Figure 7-C.2.4	 Methodology for Calculating HPWH Energy Consumption using Modified W

Equation 

7-C-5 

EE-2006-STD-0129 and EERE-2006-BT-STD-0129 COMMENT 32.2
The HPWH WHAM equation is as follows:


⎡ HP frac
 ⎛ UA ⎞ ⎤ (T k − Tamb × ) _ tan 

RE × PA HPWH 

(1 − HP _ frac ) 

⎢

⎢

⎢

⎢

⎢

⎥

⎥

⎥

⎥

⎥

× 1 − +

P
ON ,HPWH 

⎜

⎜

⎝

⎟

⎟

hpwh ⎠ (T in ) + 24 ×UA × (TTank − Tamb Q vol den C
 = × × − T
 × ) in P tan k

⎛

⎜

⎜

⎞

⎟

⎟

UA (T k − Tamb × ) tan × 1 − RE
 P
 ⎣ ⎝ ON ,ER ⎠ ⎦ ER 

Where: 

Qin = total water heater energy consumption, Btu/day,


vol = daily draw volume, gal/day,


den = density of water, set constant at 8.29 lb/gal,


Cp = specific heat of water, set constant at 1.000743 Btu/lb-oF,


Ttank = tank thermostat set point temperature, o

F,


Tin = inlet water temperature, o

F,


REHPWH = recovery efficiency of heat pump mode, %,


REER = recovery efficiency of electric resistance mode, %,


UA = standby heat-loss coefficient, Btu/h-oF,


Tamb = temperature of the air surrounding the water heater, oF,


PON,HPWH = rated input power of heat pump mode, Btu/h,


PON,ER = rated input power of electric resistance mode, Btu/h,


PAhwh = performance adjustment factor,


= 0.00019738 × T 2 -0.01842 ×T +1.3222625 , and amb amb 

HP_frac = fraction of water heating load that is satisfied by heat pump mode. 

HP_frac is calculated using the following equation: 

HP × P × RE × PA on ON ,HPWH HPWH hpwh HP _ frac = HP on × PON ,HPWH × RE HPWH × PA hpwh + (1 − HP on ) × PON ,ER × RE ER 

Where: 

HPON = fraction of time when heat pump mode is operating, %, 

vol × den ×CP (Ttan k − Tin ⎛ ) ⎜

⎝

=
 100 − ⎞

⎟

⎠

, when Tamb>32oF and 0 when Tamb<32 oF. 

9500


= rated input power of heat pump mode, Btu/h, 

= rated input power of electric resistance mode, Btu/h, 

= recovery efficiency of heat pump mode, %, 

= recovery efficiency of electric resistance mode, %, 

= performance adjustment factor, %, 

2 = 0.00019738 × Tamb -0.01842 ×Tamb +1.3222625 , and 

= temperature of the air surrounding the water heater, o

F. 

PON,HPWH 

PON,ER 

REHPWH 

REER 

PAhwh 

Tamb 

7-C-6 

EE-2006-STD-0129 and EERE-2006-BT-STD-0129 COMMENT 32.2
7-C.2.3.1 Comparison of energy use calculations for heat pump water heaters 

The energy use calculation used by DOE in this analysis is slightly different than either 

the NYSERDA Heat Pump Water Heater Site Screening Tool or DOE’s weatherization 

assistance program. 

DOE’s weatherization assistance program calculates HPWH energy use by using the 

following formula: 

vol × den ×CP (Ttan k − Tin ) Qin = EF × (1 + PA ) 

Where:


Qin = total water heater energy consumption, btu/day,


vol = daily draw volume, gal/day,


den = density of water, lb/gal,


Cp = specific heat of water, Btu/lb-o

F,


Ttnk = tank thermostat set point temperature, o

F,


Tin = inlet water temperature, o

F,


EF = energy factor, and


PA = performance adjustment factor, %.


The performance adjustment factor is given by the following formula: 

3 2 o PA = 0.00008 ×Tamb + 0.0011 ×Tamb − 0.4833 ×Tamb + 0.0857, when Tamb > 32 F 

1 o PA = −1, when T amb ≤ 32 F 

EF 

The NYSERDA Heat Pump Water Heater Site Screening Tool calculates HPWH 

energy use by using the following formula: 

⎡

⎢

⎢

⎢

⎢

⎢

lfhp 

hpa 

(1 − lfhp ) 

⎛ ⎞ ⎤ ⎟

⎠

⎟ +

UA (T k − Tamb × ) tan 1 − ⎥

⎥

⎥

⎥

⎥

⎦

× ⎜

⎜ EF
 ⎝ PHP (T − Tin ) + 24 ×UA × (TTank − Tamb Q vol den C
 = × × × ) in P tan k

⎛ UA
× (T − T
 )⎞ tan k amb × ⎜1 − ⎜

⎝

⎟

⎟ ⎣ EF
r P
r ⎠

where, 

Qin = total water heater energy consumption, Btu/day, 

vol = daily draw volume, gal/day, 

den = density of water, lb/gal, 

Cp = specific heat of water, Btu/lb-o

F, 

Ttank = tank thermostat set point temperature, o

F, 

7-C-7 

EE-2006-STD-0129 and EERE-2006-BT-STD-0129 COMMENT 32.2
Tin = inlet water temperature, o

F,


UA = standby heat-loss coefficient, Btu/h-o

F,


Tamb = temperature of the air surrounding the water heater, o

F,


PHP = rated input power of heat pump mode, Btu/h,


PR = rated input power of electric resistance mode, Btu/h,


EFr = resistance mode energy factor,


EFhpa = heat pump mode adjusted energy factor,


2 

= EF hp × (0.00019738× Tamb -0.01842 ×Tamb +1.3222625), and 

lfhp = fraction of water heating load that is satisfied by heat pump mode, %, 

rthp × PHP × EF hpa =


rthp × PHP × EF hpa + (1 − rthp ) × PR × EF R


rthp = fraction of run time by heat pump mode (96.4%). 

Table 7-C.2.1 shows a comparison of energy use results for the DOE modified WHAM 

method used in this analysis, NYSERDA Heat Pump Water Heater Site Screening Tool method, 

and DOE’s weatherization assistance program method. 

Table 7-C.2.1 Comparison of HPWH Energy Use Results 

Calculation Methodology Average Annual 

Energy Use (kWh/y) 

% Diff from method 

used in this analysis 

DOE modified WHAM 1343 -

NYSERDA method 1445 +7.6% 

Weatherization program 1095 -18.4% 

7-C.2.3.2 Calculating HPWH Cooling Effects 

Heat pump water heaters draw heat from the space in which they are located. Thus, when 

the heat pump water heater is located in the conditioned space, its use affects the load that needs 

to be met by a home’s space heating and air conditioning equipment. When the home is being 

heated, use of the heat pump water heater increases the heating load, and when it is being cooled, 

such use decreases the cooling load. 

To account for these indirect effects on home energy use, DOE estimated the impact on 

space heating and air conditioning energy consumption only for homes with a water heater 

installed in the conditioned space. For these homes, DOE estimated the impact on space heating 

in heating months only (when indoor temperature is 10 degrees greater than the average outdoor 

temperature), and the impact on air conditioning for cooling months only (when indoor 

temperature is 5 degrees below the average outdoor temperature). Figure 7-C.2.5 shows the 

methodology DOE used to calculate the amount of cooling added (i.e., heat removed) by the heat 

pump water heater. 

7-C-8 

EE-2006-STD-0129 and EERE-2006-BT-STD-0129 COMMENT 32.2
Determination of HPWH Operating Hours 

Tank Thermostat 

Temperature 

Average Monthly 

Inlet Water 

Temperature 

Average Daily Hot 

Water Use 

(Draw Model) 

Heating or 

Cooling Month 

Cooling Output 

into Conditioned 

Space 

No Heating/Cooling Decerased Cooling Load 

Pon 

(1,700 Btu/hr) 

Average Monthly 

Indoor Temperature 

(thermostat) 

Thome < 

(Toutdoor + 5) 

= Cooling 

Water Heat 

Capacity 

Water 

Density 

Average Monthly Temperature Difference 

Thome > 

(Toutdoor + 10) 

= Heating 

Average Daily Water 

Heater Heating Load 

Cooling Capacity 

(3,500 Btu/hr) 

Additional Heating 

Load 

No Additional 

Heating/Cooling 

RE 

(rated vol depedant 

and Adjusted for 

Tamb) 

Average Monthly 

Outdoor Temperature 

Installation 

Location 

Conditioned 

space 

Non-conditioned space 

RECS Sampled 

Household 

Overcooling Effect 

(Decreases Load 

by 1/3) 

Heatin

Equipm

Efficien

Cooling Equ

Efficien

AEO 20

No Additional 

Heating/Cooling 

Space He

Determination of Heating or Cooling Month 

Figure 7-C.2.5 Methodology for Calculating HPWH Cooling Effects


7-C-9 

EE-2006-STD-0129 and EERE-2006-BT-STD-0129 COMMENT 32.2
The equation for calculating the cooling input (amount of cooling added or heat removed) 

by the heat pump water heater is as follows: 

vol × den ×Cp (Ttan k − Tin ) CoolingInput = CoolingCap HPWH ×

P × RE × PA ON ,HPWH HPWH HPWH 

Where:


CoolingInput = amount of cooling added by the HPWH, Btu/h,


vol = daily draw volume, gal/day,


den = density of water, lb/gal,


Cp = specific heat of water, Btu/lb-oF,


Ttank = tank thermostat set point temperature, oF,


Tin = indoor air temperature, oF,


PON,H,PWH = rated input power, Btu/h,


RE = recovery efficiency, %,


PAhwh = performance adjustment factor, %, and


CoolingCapHPWH = cooling capacity of heat pump water heater, Btu/h.


3 PON for heat pump water heaters is 500 W (1704 Btu/h), and CoolingCapHPWH is 3500 

2 4 Btu/h. DOE used RECS 2001 data for each household to determine the primary heating system 

and fuel used to heat the house as well as the cooling system type. DOE then assigned an energy 

efficiency to each type of equipment to determine the energy use loss (from heating) or gain 

(from cooling). DOE based the energy efficiency of the heating and air conditioning equipment 

5 on the stock-average values for 2015 given in EIA’s Annual Energy Outlook 2008. To account 

for the times during the summer months when the air conditioner is not operating (e.g., at night), 

DOE reduced the estimated cooling benefits from the water heater by one-third (8 out of 24 

hours). 

The analysis results that the HPWH cooling effect affects 46.4% of households for an 

average of 6.1 months in the heating season and 29.6% of households for an average of 4.7 

months in the cooling season. Overall 49.8% of households are affected either in cooling and/or 

heating season. The average net cost from heating is about $82 per year, while the average net 

benefit for cooling is about $10 per year. These impacts are account for in the LCC and NIA 

analysis. 

Alternatively, the household can install a venting system to vent the cold air out of the 

conditioned space. DOE estimates that the average cost for this installation would be similar to 

the average cost of adding a new plastic venting system for condensing furnaces which is found 

6 in the 2007 Furnace and Boilers Rulemaking. The cost would be $442.56. In addition, there 

would be the cost of adding an exhaust venting fan of about $100. The total cost would then be 

about $542.56. These estimates are provided for comparison only and are not applied in the 

analysis. 

7-C-10 

EE-2006-STD-0129 and EERE-2006-BT-STD-0129 COMMENT 32.2
7-C.2.4 WHAM Equation for Gas Instantaneous Water Heaters 

For instantaneous water heaters, DOE calculated the energy use using a similar approach 

to storage water heaters, but modified to account for the absence of storage tank and adjusted for 

the performance observed in the field compared to that measured with the DOE test procedure. 

Figure 7-C.2.6 shows the methodology for calculating the energy consumption of instantaneous 

water heaters using the modified WHAM equation. 

The instantaneous water heater WHAM equation is as follows: 

where: 

Qin = total water heater energy consumption, Btu/day, 

⎛

⎜

⎜

⎝

vol = daily draw volume, gal/day,


den = density of water, lb/gal,


Cp = specific heat of water, Btu/lb-oF,


Ttank = tank thermostat set point temperature, oF,


Tin = inlet water temperature, oF,


RE = recovery efficiency, %,


PAiwh = performance adjustment factor = (100% – 8.8%), %,


Qp = pilot input rate, Btu/h,


Qout = heat content of the water drawn from the water heater, Btu/h, and


Pon = rated input power, Btu/h,.


The performance adjustment factor for instantaneous water heaters (PAiwh) is derived 

7 from a study conducted for California Energy Commission (CEC) in 2006. According to this 

report, current DOE test procedure energy factor calculations for gas-fired instantaneous water 

heaters overvalue their performance by not accounting for the impact of small hot water draws 

and heat exchanger “cool down” on overall performance. The DOE test procedure measures six 

successive draws of about 10 gallons, while actual field use has many more draws many of 

which are small draws. The 8.8% depredating factor is derived using average hot water use 

profiles and weighting more efficient “hot starts” and less efficient “cold starts”. 

⎟ +

⎞

⎟

⎠

(T in ) Q


P
ON 

vol den C
 × × P k − T
 p (T amb ) tan Q
 = × 1
− 24
×Q
 × − T
 in p Tank RE PA × hpwh 

7-C-11 

EE-2006-STD-0129 and EERE-2006-BT-STD-0129 COMMENT 32.2
Average Yearly Tank 

Temperature 

(Distribution) 

Average Monthly 

Inlet Water 

Temperature 

Average Daily Hot 

Water Use 

Average Monthly 

Ambient 

Temperature 

Draw Model 

Mode 

Energy 

Consumption During Water 

Heating 

Energy 

Consumption 

During Standby 

Water Heating 

Standby 

Average Daily 

Total Energy Use 

for Month 

RE 

Qp 

Modified WHAM Calculation 

Pon 

Heat Capacity of 

Water Density of Water 

Average Monthly Temperature Difference 

Water Heater Heating Load 

WH ON = 24 hrs 

Perfor

Adjustme

Figure 7-C.2.6 Methodology for Calculating Instantaneous WH Energy Consumption using Modified 

7-C-12 

EE-2006-STD-0129 and EERE-2006-BT-STD-0129 COMMENT 32.2
7-C.3 POOL HEATERS 

8 DOE calculated the average annual fossil fuel energy, EF, using the DOE test procedure:

EF = BOH ×QIN − (POH − BOH ) ×Qp 

Where: 

BOH = burner operating hours, h/year, 

Qin = pool heater input rate, kBtu/h, 

POH = pool operating hours, h/yr, and 

Qp = pilot light input rate, kBtu/yr. 

The burner operating hours are calculated using the pool heater heating load (PHHL) for 

each sample household. The equation for BOH is as follows: 

LOAD BOH = QIN × Et 

Where:


BOH = burner operating hours, h/year,


PHHL = Pool heater heating load, btu/year, (see Appendix G),


Qin = pool heater input rate (kBtu/h) =250 kbtu/h,


Et = thermal efficiency.


DOE calculated the electricity consumption using the following formula 

EF = BOH × PE − (POH − BOH ) × PE s tan by 

Where:


BOH = burner operating hours,


PE = electrical consumption of the heater,


POH = pool operating hours (h/yr), and


PEstby = electrical consumption of the heater when the burner is off.


7-C.4 DIRECT HEATING EQUIPMENT 

DOE calculated the average annual fuel energy, EF, for single-stage direct heating 

9 equipment using the following formula from the current revision of DOE’s test procedure:

EF = BOH SS × (QIN − QP ) + 8760 ×QP 

Where: 

7-C-13 

EE-2006-STD-0129 and EERE-2006-BT-STD-0129 COMMENT 32.2
BOH = burner operating hours, h/year, 

Qin = input capacity (at the max input rate), kBtu/h, 

8760 = hours per year, and 

Qp = pilot light input rate, kBtu/h. 

The burner operating hours are calculated using the calculated house heating load (HHL) 

for each sample household (see Appendix G). The equation for BOH is as follows: 

BOH SS = A× HHL − 4160 ×QP ×η U , 

Where: 

BOH = burner operating hours, h/year, 

100,000 A = , 341,000 × PE + (Qin − QP )×η U 

HHL = house heating load (see Appendix G), btu/year, 

PE = maximum electric power, kW, 

4160 = average heating season hours, 

QP = pilot light input rate, kBtu/h, 

ηU = 

2950 AFUE ×η SS ×Qin , and 2950 ×η SS ×Qin − AFUE × 2.033 × 4600 ×QP 

ηSS = steady state efficiency, %. 

The steady state efficiency (ηSS) is calculated by solving for ηSS in the equation given in 

section 4.1.17 of the DOE test procedure using the following equation and the values for the 

parameters DF, DS, PF, and LJ given in the DOE test procedure: 

AFUE +1.78 × D +189 × D −129 × P − 2.8× L +1.81 

η = F S F J 

SS 0.968 

The electricity consumption is calculated as follows: 

ElectUse PE BOH ×−+×= PBOH stby (8760 )

Where: 

ElecUse = DHE electricity consumption, kWh/year, 

BOH = burner operating hours, h, 

PE = electricity demand when the product is firing, kW, and 

Pstby = DHE standby power draw (when the burner is OFF), kW. 

7-C-14 

EE-2006-STD-0129 and EERE-2006-BT-STD-0129 COMMENT 32.2
REFERENCES 

1.	 Lutz, J., C. D. Whitehead, A. Lekov, D. Winiarski, and G. Rosenquist, WHAM: A 

Simplified Energy Consumption Equation for Water Heaters., in 1998 ACEEE Summer 

Study on Energy Efficiency in Buildings. 1998: Asilomar, CA. p. 1.171-1.183. 

2.	 Kelso, J., Incorporating Water Heater Replacement into The Weatherization Assistance 

Program, May 2003, 2003. D&R International, Ltd. Information Tool Kit. 

3.	 Maxwell, J., Heat Pump Water Heater Economic Model, personal communication. 

NYSERDA. 2004. 

4.	 U.S. Department of Energy - Energy Information Administration, Residential Energy 

Consumption Survey: 2001 Public Use Data Files, 2001. 

<http://www.eia.doe.gov/emeu/recs/recs2001/publicuse2001.html> 

5.	 U.S. Department of Energy - Energy Information Administration, Annual Energy 

Outlook 2008 (Revised Early Release) with Projections to 2030, 2008. Washington, DC. 

Report No. DOE/EIA-0383(2008). 

6.	 U.S. Department of Energy - Energy Efficiency & Renewable Energy, Technical Support 

Document: Energy Efficiency Standards for Consumer Products: Residential Furnaces 

and Boilers, 2007. Washington, DC. 

7.	 Davis Energy Group, Measure Information Template: Tankless Gas Water Heaters, May 

18, 2006. Docket # 07-BSTD-1. 

<http://www.energy.ca.gov/title24/2008standards/prerulemaking/documents/2006-05­

18_workshop/2006-05-11_GAS_WATER.PDF> 

8.	 Department Of Energy, Appendix E to Subpart B of Part 430-Uniform Test Method For 

Measuring The Energy Consumption Of Water Heaters. filed as "WH Test Procedure 10 

CFR 430 subpart B, Appendix E". 

9.	 Department Of Energy, Appendix O to Subpart B of Part 430-Uniform Test Method For 

Measuring The Energy Consumption Of Vented Home Heating Equipment. filed as "WH 

Test Procedure 10 CFR 430 subpart B, Appendix E". 

7-C-15 

EE-2006-STD-0129 and EERE-2006-BT-STD-0129 COMMENT 32.2