CHAPTER 7. ENERGY USE ANALYSIS

TABLE OF CONTENTS



### 7.1 INTRODUCTION

................................ ................................ ................................................. 7-1 7.2 EQUIPMENT ENERGY USE SAVINGS DETERMINATION

....................................... 7-1 7.2.1 Splitting Heating and Cooling Energy

................................ ................................ 7-1 7.2.2 Adjusting for Climate Change

................................ ............................................ 7-2 7.2.3 Adjusting for Capacity and Energy Efficiency Ratio

........................................ 7-4 7.3 PTAC AND PTHP EQUIPMENT ENERGY USE RESULTS

......................................... 7-5

LIST OF TABLES

Table 7.3.1 Annual Energy Use by Equipment Class and Efficiency Level for PTACs

.................. 7-6 Table 7.3.2 Annual Energy Use by Equipment Class and Efficiency Level for PTHPs

.................. 7-6

LIST OF FIGURES

Figure 7.2.1 Comparison of cooling degree days by state for TMY3 and TMY2

......................... 7-3

7-i

### CHAPTER 7. ENERGY USE ANALYSIS

7.1 INTRODUCTION

Whole

- building simulations from the 2008 packaged terminal air conditioning (PTAC) and packaged terminal heat pump (PTHP) e quipment rulemaking provided annual unit energy consumption (UEC) data by cooling capacity and energy efficiency ratio ( EER ). 1 Th ese data are used for those equipment classes and efficiency levels that are the same in this rulemaking and adjusted for those that
are different . T his chapter describes the methodology used to adjust the unit energy consumption of

PTA C and PTHP equipment for this rulemaking.



### 7.2 EQUIPMENT ENERGY USE SAVINGS DETERMINATIO N

Whole

- building simulations in the previous rulemaking were performed on PTACs and PTHPs for four equipment classes, six efficiency levels, and 51 location s (the U.S. States and the District of Columbia). The four equipment classes consist of combinations of PTAC and PTHP equipment and of representative cool ing capacities, namely 9,000 Btu/h and 12,000 Btu/h

. As whole

- building simulations are an excellent app roach to obtain UEC data, the 1, 224 annual UECs data points were leveraged for this rulemaking.

The current rulemaking considers a set of capacities and efficiency levels that differs from that in the previous rulemaking . In order to make relevant the UEC s , three transformations were performed : splitting heating and cooling energy, adjusting for climate change

, and adjusting for capacity and EER.



### 7.2.1 S plitting H eating and C ooling E nergy The first transformation prepares the UEC for the following two transformations. As the total annual UECs, UE C total , capture both a cooling and heating energy portion
, the UEC was split into
UE C cooling and UE C h eating . The U.S. Department of Energy ( DOE ) is aware that PTACs and PTHPs have slight differences in function and performance. However, PTACs and PTHPs have a similar functionality
other than a reversing valve

. In addition, insufficient data exist highlighting substantial differences in cooling energy consumption . For these reasons, DOE assumed that the UEC of a PTAC is equal to the energy expended during a PTHP’s operation in cooling mode, assuming that the equipment has the same efficiency level and capacity

, as shown in Eq. 7.2.1

. The remaining energy of a PTHP, which is the difference between the total UEC and the cooling energy, as shown in Eq. 7.2.2 , is the heating energy:

7-1UE C PTAC = UE C PTHP

_ cooling 

### Eq. 7.2 .1

UE C total = UE C h eating + UE C cooling Eq. 7.2 .2

It was assumed that the fan energy during periods of cooling was included with the cooling energy and the fan energy during periods of heating was included with the heating energy. I t was also assumed that the fan energy during periods of cooling scaled with the cooling energy and the fan energy during periods of heating scaled with the heating energy

.



### 7.2.2 Adjusting for Climate Change

The second transformation adjusts for the projected impact of global warming on hotter

sum mer days and warmer winter days. A n adjustment to the unit cooling energy consumption and unit heating energy consumption was made based on the change in cooling degree days (CDD) and heating degree days (HDD) from an older TMY2 (Typical Meteorological Year) weather dataset to a newer TMY3

weather dataset , which was updated in 2008

. 2

, 3 A comparison of the two datasets showed that total annual CDD have increased by 5% and total annual HDD have increased by 2 % at all locations used in this analysis, as shown in Figure 7.2 .1

.

7-2

### Figure 7.2 .1 Comparison of cooling degree days by state for TMY3 and TMY2

The figure shows the cooling degree days (CDD) relative to 65 °F computed from the TMY3 data vs. the CDD for TMY2. The calculation is done separately for day time (8 am to 8pm) and night time hours. Each point corresponds to a state; in cases where there a re multiple stations in a single state the data are averaged. As the TMY3 data are considered to be more representative of current weather, t he
total annual CDD increase and total annual HDD increase were assigned to the weather multipliers, W c and W h , for co oling and heating, respectively, and were applied to the separated cooling and heating
UECs in the manner as shown in Eq. 7.2.3 and Eq. 7.2.4 :



### UE C cooling_weat h er 

### = ( 1 + W c 

### )

∙ UE C cooling 

### Eq. 7.2

. 3

UE C h eating

_ weat h er 

### = ( 1 + W h



### )

∙ UE C h eating 

### Eq. 7.2

. 4

7-3

### 7.2.3 Adjusting f or Capacity and Energy Efficiency Ratio

The third transformation account s for adjustments of cooling capacity and/or EER values that
differ from those in the previous rulemaking (source) to those considered in the current rulemaking (target)

. UE C cooling

_ weat h er for each equipment class and each efficiency level was linearly scaled from
source to target cooling capacity and/or EER

. If the UEC only changed with cooling capacity, DOE performed a linear interpolation across a constant EER value; this operation is highlighted in Eq. 7.2.5 . If the UEC only changed with EER, DOE performed a linear interpolation across a constant cooling ca pacity value; this operation is highlighted in Eq. 7.2.6 . If the UEC changed with both cooling capacity and EER, DOE performed a linear interpolation across both variables, on e at a time, one after another, using the equations as already set forth in Eq. 7.2.5 and Eq. 7.2.6

. Similarly, for heating e nergy, DOE accounted for differences in coefficient of performance ( COP ) by linearly scaling UE C h eating

_ weat h er , at a constant cooling capacity, for each equipment class and each efficiency level, from source to tar get COP, as
shown in Eq. 7.2.7

.

UEC target = UE C source1 + ( UE C source2 − UE C source1 ) � Capacit y target - Capacit y source1 Capacit y source2 - Capacit y source1 � �

constant EER

Eq. 7.2 .5

W here :

UEC target = interpolated unit energy consumption at the target cooling capacity

, UE C source1 = unit energy consumption at the source cooling capacity, for the first point of the interpolation

, UE C source2 = unit energy consumption at the source cooling capacity, for the second point of the interpolation

, Capacit y target = target cooling capacity

, Capacit y source1 = source cooling capacity for the first point of the interpolation

, and Capacit y source2 = source cooling capacity for the second point of the interpolatio n.

UEC target = UE C source1 + ( UE C source2 − UE C source1 ) � EE R target − EE R source1
EE R source2 − EE R source1 ��

constant cooling capacity

Eq. 7.2 .6

W here :

UEC target = interpolated unit energy consumption at the target cooling capacity

,

7-4UE C source1 = unit energy consumption at the source cooling capacity, for the first point of the interpolation,
UEC source2 = unit energy consumption at the source cooling capacity, for the second point of the interpolation,
EER target = target EER,
EER source1 = source EER for the first point of the interpolation, and
EER source2 = source EER for the second point of the interpolation.

UEC target = UE C source 1 + ( UE C source 2 − UE C source 1 ) � CO P target − CO P source 1
CO P source 2 − CO P source 1 ��

constant cooling capacity

Eq. 7.2 .7

W here :

UEC target = inte rpolated unit energy consumption at the target cooling capacity

, UE C source 1 = unit energy consumption at the source cooling capacity, for the first point of the interpolation,
UE C source 2 = unit energy consumption at the source cooling capacity, for the second point of the interpolation,
COP target = target COP,
COP source 1 = source COP for the first point of the interpolation, and
CO P source 2 = source COP for the second point of the interpolation.



### 7.3 PTAC AND PTHP EQUIPMENT ENERGY USE RESULTS
DOE summed the cooling energy and heating energy, upon completion of the transformations, to give the total UEC. The U.S. average UEC s for each of the considered capacities and EER s are provided in Table 7.3 .1 for PTACs and Table 7.3 .2 for PTHPs. The UECs disaggregated by the 51 locations are pr esented in Appendix 7

- A.

7-5

### Table 7.3 .1 Annual Energy Use by Equipment Class and Efficiency Level for PTACs

Efficiency
Level >7,000 Btu/h >7,000 Btu/h and < 15,000 Btu/h >15,000 Btu/h

EER UEC (kWh) EER UEC (kWh) EER UEC (kWh)

0 * 11.7 892 11.1 1078 9.3 1688

1 † 11.9 881 11.3 1066 9.5 1671

2 12.2 866 11.5 1050 9.7 1657

3 12.6 839 12.0 1022 10.0 1625

4 13.1 813 12.4 994 10.4 1594

5 13.6 786 12.9 966 10.8 1563

6 13.8 773 13.1 952 11.0 1547
* This level represents the Federal minimum.

† This level represents the ANSI/ASHRAE/IES Standard 90.1

- 2013 minimum for this equipment type.



### Table 7.3 .2 Annual Energy Use by Equipment Class and Efficiency Level for PTHPs

Efficiency Level >7,000 Btu/h >7,000 Btu/h and < 15,000 Btu/h >15,000 Btu/h

EER
COP UEC (kWh) EER
COP UEC (kWh) EER
COP UEC (kWh)

0* 11.9
3.3 1728 11.3
3.2 1985 9.5
2.9 2847

1 12.2
3.5 1708 11.5
3.3 1956 9.7
2.9 2829

2 12.6
3.5 1674 12
3.4 1918 10
3 2778

3 13.1
3.6 1639 12.4
3.5 1879 10.4
3.1 2727

4 13.6
3.7 1605 12.9
3.6 1841 10.8
3.2 2676

5 13.8
3.8 1588 13.1
3.6 1822 11
3.2 2651

* This level represents the Federal minimum and the ANSI/ASHRAE/IES Standard 90.1

- 2013 minimum for this equipment type.

7-6REFERENCES



### 1. U.S. Department of Energy – Office of Energy Efficiency and Renewable Energy, Energy Conservation Program for Commercial and Industrial Equipment: Packaged Terminal Air Conditioner and Packaged Terminal Heat Pump Energy Conservation Standards., 2007. (Last accessed June, 2014.)

< http://www.regulations.gov/#!docketDetail;D=EERE

- 2007 -BT- STD

- 0012 >

2. National Renewable Energy Laboratory, National Solar Radiation Data Base 1961

- 1990: Typical Meterological Year 2, (Last accessed June, 2014.)

< http://rredc.nrel.gov/solar/old_data/nsrdb/1961

- 1990/tmy2/ >

3. National Renewable Energy Laboratory, National Solar Radiation Data Base 1991

- 2005 Update: Typical Meterological Year 3, (La st accessed June, 2014.)

< http://rredc.nrel.gov/solar/old_data/nsrdb/1991

- 2005/tmy3/ >

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