7-i 

CHAPTER 7. ENERGY USE ANALYSIS

TABLE OF CONTENTS

7.1 INTRODUCTION .............................................................................................................. 7-1

7.2 OVERVIEW OF ENERGY USE ANALYSIS BY EQUIPMENT CLASS ...................... 7-1

7.2.1 Simulation Tool Description ................................................................................... 7-2

7.2.2 Building Models...................................................................................................... 7-2

7.2.2.1 Modular Classroom Simulation Model ....................................................... 7-2

7.2.2.2 Modular Office Simulation Model.............................................................. 7-3

7.2.2.3 Telecommunication Shelter Simulation Model .......................................... 7-3

7.2.3 Equipment Modeling .............................................................................................. 7-5

7.2.4 Simulated Climates and Weather Data ................................................................... 7-7

7.2.5 Energy Use Extraction and Aggregation to State Level Data ................................. 7-7

7.2.6 Calculation of Gas Heating Impact ......................................................................... 7-9

7.3 ENERGY USE ANALYSIS RESULTS ........................................................................... 7-10

REFERENCES .......................................................................................................................... 7-12

LIST OF TABLES

Table 7.2.1 Development of Condenser-Only COP Values by Efficiency Level ....................... 7-7

Table 7.2.2 Calculation of UEC for Office Building in Atlanta, GA .......................................... 7-8

Table 7.3.1 National UEC Estimates for SPVAC and SPVHP Equipment ............................... 7-11

LIST OF FIGURES

Figure 7.3.1 Baseline National Unit Energy Consumption Estimates by Building Type.......... 7-10
7-1 

CHAPTER 7. ENERGY USE ANALYSIS

7.1 INTRODUCTION

The energy use analysis discusses the process used by the U.S. Department of Energy 

(DOE) to provide energy use estimates for baseline and higher-efficiency standard levels for 

single package vertical air conditioners (SPVAC) and heat pumps (SPVHP), collectively referred 

to here as single package vertical units (SPVU). 

This chapter describes the energy use analysis for SPVAC and SPVHP equipment with a 

cooling capacity less than 135,000 British thermal units per hour (Btu/h). This chapter details the 

determination of baseline annual per unit energy consumption (UEC) estimates for each 

equipment class and describes the development of UEC estimates for more-efficient equipment, 

up to the maximum technologically feasible (max-tech) levels defined in chapter 5 of the 

technical support document (TSD). 

For each of these equipment types, the existing or proposed Federal standard is expressed 

as an efficiency metric or metrics: energy efficiency ratio (EER) for cooling efficiency and

coefficient of performance (COP) for heating efficiency. For each equipment class, this chapter 

describes how an estimate of the UEC is developed corresponding to the different rated 

efficiencies. 

7.2 OVERVIEW OF ENERGY USE ANALYSIS BY EQUIPMENT CLASS

The analysis to assess the UEC of SPVAC and SPVHP equipment began with a review of 

the existing market and applications for the various classes of equipment. The market assessment

indicated that for SPVU equipment, the market is primarily modular buildings characterized as 

education (i.e., modular classrooms), modular offices, and what are commonly referred to as 

technical or telecommunication shelters—small, self-contained building structures housing 

electronic equipment but not intended for occupants. DOE analyzed the energy consumption of 

SPVU equipment using a building simulation approach for three classes of commercial 

buildings: modular classrooms, modular offices, and telecommunication shelters. To estimate the 

energy use of SPVAC and SPVHP equipment in these building types, DOE developed building 

simulation models for use with DOE’s EnergyPlus software.1

 In each case, the building 

construction elements (e.g., footprint, window-wall ratio, envelope construction, and general 

building form factor and design) were developed to be representative of typical building designs 

within the general class of building being modeled. The building simulation models were 

configured to use heating, ventilating, and air-conditioning (HVAC) systems representing

SPVAC or SPVHP equipment and were modeled in a diverse set of climates and for the range of 

efficiency levels developed in the engineering analysis. 

Heating, cooling, and supply blower energy use from each simulation was scaled by the 

ratio of representative cooling capacities analyzed in the rulemaking to the simulated equipment 

capacities for each building modeled. This provides climate-specific UEC statistics for the 

representative cooling capacities developed in the engineering analysis (36,000 Btu/h and 72,000 

Btu/h) for each building type. These climate-specific energy use results were weighted to provide 
7-2 

state-level UEC estimates by building type and equipment class. These state-level estimates were 

provided to the subsequent life-cycle cost (LCC) analysis.

7.2.1 Simulation Tool Description

DOE used the EnergyPlus version 8.0 software for the energy use analysis. EnergyPlus 

predicts the energy use of a building given hourly weather file data, a description of the building 

and the operation of the building, estimated internal loads, and a characterization of the building

HVAC equipment. Energy use results for the building can be readily extracted for different time 

steps and at detailed subcomponent levels if necessary. EnergyPlus is an integrated software tool, 

where both the building loads and how those loads are served by equipment are solved 

iteratively. EnergyPlus has a separate, but robust, ground heat transfer model, which is 

particularly useful in the simulation of smaller buildings. DOE is currently using EnergyPlus as 

the basis for most of its whole-building energy simulation research, and the tool and its ongoing 

development are actively supported within DOE. 

7.2.2 Building Models

A prototypical building model was developed for each building type and is described by 

the building footprint, general building size and design, and internal gains and operating 

schedules. A description of each building model is provided below, with further details, 

including operation schedules, found in appendix 7A. These three building models (modular 

classroom, modular office, telecommunication shelters) were used to establish the energy usage 

of SPVAC and SPVHP equipment used in the aforementioned building markets. 

7.2.2.1 Modular Classroom Simulation Model 

To estimate the energy consumption of SPVAC and SPVHP equipment in a classroom 

application, DOE developed a double wide (56 ft by 28 ft), single story, 1,568-ft2

 wood-frame 

modular classroom simulation model. Wood-frame construction was chosen because it is 

consistent with known modular classroom design. A crawlspace was used to represent the aboveground floor level construction characteristic of these buildings. A window-to-wall area fraction 

of 15 percent was used as representative of typical modular classroom construction. Envelope 

performance characteristics were established using the requirements in ANSI/ASHRAE/IESNAa

90.1-2004 to approximate a mix of existing stock and new construction.2 Schedules and load 

profiles were taken from classroom-space building zones in the DOE primary school commercial 

prototype building models.3 These schedules represent a building used as a classroom effectively 

10 months of the year, with light (but daily) usage during a 2-month summer period. Internal 

loads for receptacle (plug) loads were based on direct equipment power (watts per square foot) 

figures for the DOE primary school commercial prototype building model and were set to 

1.4 W/ft2 peak. Occupancy loads were also developed from the DOE primary school commercial 

prototype building and were set to 25 persons per 1,000 ft2. Lighting power and internal loads 

were based on ASHRAE 90.1-2004 lighting power density levels for classroom space at 

1.4 W/ft2 peak, which was selected to be representative of a mix of existing classroom lighting 

power in the building stock and in recent construction. Ventilation levels were based on the 

 

a ANSI is the American National Standards Institute; ASHRAE is the American Society of Heating, Refrigerating, 

and Air-Conditioning Engineers; IESNA is the Illuminating Engineering Society of North America.
7-3 

requirements of ASHRAE Standard 62.1-2004, which reflects current ventilation requirements in 

many building codes and would be appropriate for most new or replacement equipment. 

Mechanical ventilation was set at 0.37 cubic feet per minute (cfm)/ft2

 for the classroom based on 

ASHRAE 62.1-2004 requirements. The HVAC equipment was scheduled to operate the supply 

fan 14 hours a day during weekdays to provide both ventilation and circulation during occupied 

periods. It was scheduled off during weekends and holidays. 

Infiltration was modeled using the EnergyPlus Airflow Network model, which provides 

for a wind- and temperature-based estimate of infiltration loads during the year that also

responds to HVAC system operation. An equivalent leakage area for the building was first 

established using an overall air exchange rate of 7 air changes per hour (ACH) under a 50-pascal

indoor-outdoor pressure difference. This equivalent leakage area was then spread evenly among

the walls, floor, and ceiling components. The 7 ACH value was selected as generally 

representative of range of reported ACH values from different studies.4 5 6

Economizer requirements by location were established consistent with those in ASHRAE 

90.1-2004 for equipment less than 65,000 Btu/h, and separately for equipment greater than or 

equal to 65,000 Btu/h, with both sets of economizer requirements being simulated to help 

establish the typical energy use per ton for equipment in these different size categories. 

7.2.2.2 Modular Office Simulation Model

To estimate SPVU energy use in an office type application, DOE developed a 1,568-ft2

(56-ft by 28-ft) wood-frame modular office simulation model similar in general design to the 

modular classroom model. A principal difference between the models is in the use of office type 

load and usage profiles for the modular office application. Schedules and load profiles as well as 

internal load estimates were all based on DOE’s small office commercial prototype building 

model.3 Internal receptacle loads were set to 0.63 W/ft2 peak. Peak scheduled occupancy was set 

to 5.6 persons per 1,000 ft2. Lighting power requirements were based on ASHRAE 90.1-2004 

requirements for office space, selected to be representative of a mix of lighting power in the 

building stock and in recent construction, at 1.0 W/ft2 peak. Air-side economizer requirements 

were established consistent with those in ASHRAE 90.1-2004 for SPVU equipment less than 

65,000 Btu/h, and separately for SPVU equipment greater than or equal to 65,000 Btu/h, with 

both sets of requirements being simulated to help establish the typical energy use per ton for 

SPVU equipment in both size categories. The HVAC equipment was scheduled to operate the 

supply fan 13 hours a day during weekdays and 12 hours on Saturday during occupied periods. It 

was scheduled off Sundays and holidays. 

7.2.2.3 Telecommunication Shelter Simulation Model

Telecommunication shelters are used to house electronic components like phone 

switches, optical fiber networking equipment, transmitters, and receivers in remote locations 

away from a central telecommunication office. These shelters protect the equipment from 

humidity, dust, solar overheating, and physical damage. As the housed electronic equipment 

generates heat during operation, there is a need to maintain the air temperature inside the shelter

within certain limits. To estimate SPVAC energy use in a typical technical/telecommunication 

shelter, DOE developed a small telecommunication shelter model in the form of a 240-ft2 precast 
7-4 

concrete wall and roof shelter (12 ft by 20 ft).

b The telecommunication shelter used continuous 

interior R-10 foam insulation in roof, floor, and wall assemblies. The pre-fab building was 

mounted on a concrete slab in all climates simulated as is typical commercial practice. 

For the telecommunication shelter, DOE did not identify a source for typical 

representative internal electronic loads as a function of building size and did not find substantial 

information on representative internal gain profiles. However, based on discussions with shelter 

retailers, DOE used a 10.55-kW (36,000-Btu/h) maximum internal load to reflect internal design 

load in the shelter. DOE determined that on average over the year, this internal load ran at a 

constant 65 percent of peak internal load, reflecting estimates for computer server 

environments.7 A study of options for improving energy efficiency in the telecommunications 

(e.g., cellular phone) network notes that power consumption for electronics in many shelters is

often fairly stable from day to night and largely independent of phone traffic. However, an 

available operating strategy that consists of turning certain radio transmitters and receivers off 

when the call traffic decreases can provide up to a 40 percent reduction in power consumption 

during these periods.8 Lacking further detail, DOE used a constant average thermal load of 6.86 

kW (23,400 Btu/h), which did not change with time of day. However, equipment sizing was 

based on the maximum internal load level plus design day environment loads in each climate. 

DOE did not add an additional cooling sizing factor for the telecommunication shelter model as 

this was reflected in the underlying computer server data defining the average internal load. 

Lighting power was not explicitly modeled as its use would be expected to be minimal. 

The high internal load density and the insulated building envelope in the 

telecommunication shelter result in year round cooling loads. To reduce energy consumption, air 

side economizers represent a means to reduce the cooling load in telecommunication shelters. 

Discussion with different shelter retail and manufacturing firms indicated a wide variation in 

whether economizers are typically specified by the individual telecommunication firm 

customers. While some shelter manufacturer/retailers indicated climate variation in how these 

are specified,

c d

 others suggested it is often driven more by individual corporate user 

specifications.b

 A voluntary standard for telecommunication site development, Motorola R-56, 

suggests that all wall-mount HVAC units should be equipped with economizers.9

 However, 

discussion with manufacturer contacts during the engineering analysis suggested that overall 

only approximately 45 percent of SPVU equipment is shipped with an economizer option for the 

telecommunication market. These data were not available by equipment capacity. As a 

consequence, DOE simulated the telecommunication building in each location with and without 

an economizer option and provided both sets of results as inputs to the LCC analysis, where they 

could be appropriately sampled using the estimated market fraction with and without an 

economizer. 

The HVAC equipment is scheduled to operate in a fan cycling mode during all hours. In 

this mode, the fan will operate only for the duration of time that the SPVAC compressor operates 

 

b Typical shelter and peak equipment load based on Pacific Northwest National Laboratory (PNNL) communication 

with staff at Midwest Surplus, a retailer of new and refurbished communication shelters (May 18, 2012). 

<http://www.midwestsurplusinc.com/contactus.php> c Discussion between PNNL staff and Thermobond staff (July 3, 2012). < http://www.thermobond.com> 

d Phone discussion with PNNL and CellXion staff (Aug 1, 2012). <http://sabrebuildingsystems.com> 
7-5 

to serve the space conditioning loads, or in the event that the load is met through economizer 

cooling. 

7.2.3 Equipment Modeling

Equipment performance characteristics used in modeling are shown in appendix 7A. 

Each building model was simulated using one HVAC unit for the building, responding to a 

single space thermostat. In the case of the telecommunication shelter, redundant identical air 

conditioners with alternating usage during the year were assumed when establishing average 

annual energy consumption per unit. The use of redundant air-conditioning units was consistent 

with industry practice based on communication with shelter manufacturerse f as well as the 

Motorola R-56 guideline. To provide for this, the energy use per unit established for the 

equipment serving telecommunication shelters was calculated by dividing the energy use per ton 

for the simulated buildings by 2 and then multiplying by the representative capacity in tons for 

each equipment class.

Simulations were done for the buildings using SPVAC equipment with electric resistance 

heating, and then a separate set of simulations was done for buildings with SPVHP equipment. 

For each equipment class and building type combination, DOE simulated each efficiency level 

identified in the engineering analysis. Supply air fan/blower power at the baseline efficiency 

level was based on review of manufacturer literature and reported blower motor voltage and 

current data for 3-ton SPVAC equipment at a 9.0 energy efficiency ratio (EER) level and using a 

permanent-split capacitor (PSC) motor.10 The fan power data were not available, so a power 

factor of 0.9 was used to convert available blower motor volt-amps to watts. The corresponding 

fan power was estimated to be 154.4 watts per cooling ton (W/ton). Based on data developed in 

the engineering analysis, the energy analysis used PSC motors at this power level for EER values 

up to 9.5. Electronically commutated supply air fan motors were assumed for equipment with an 

EER of 10.0 and higher to reflect the engineering analysis assumptions. Direct fan power data 

were not available from manufacturer literature for fans using electronically commutated 

(brushless direct current) motors (ECM). An estimate of the fan power for systems using an 

ECM fan motor was made based on the ratio of typical motor efficiency for fractional (1/3) 

horsepower (hp) PSC and ECM motors.g The resulting ECM motor horsepower was estimated 

at 113.6 W/ton. Fan motors were assumed to run at constant speed and constant power while 

operating and did not reduce speed as a function of thermal load.h

 

Equipment cooling EER and heating COP were converted to corresponding condenseronly cooling COP and condenser-only heating COP simulation inputs for each efficiency level 

simulated for the nominal 95 °F and 47 °F outdoor temperature rating conditions, respectively. 

 

e Typical shelter and peak equipment load based on Pacific Northwest National Laboratory (PNNL) communication 

with staff at Midwest Surplus, a retailer of new and refurbished communication shelters (May 18, 2012). 

<http://www.midwestsurplusinc.com/contactus.php> 

f Discussion between PNNL staff and Thermobond staff (July 3, 2012). < http://www.thermobond.com> g Nominal PSC motor efficiency is estimated at 0.54 and nominal ECM fan motor efficiency is estimated at 0.725. 

Adjusting for the benefit of the fan heat reduction and greater net capacity yielded a supply fan power per ton ratio 

of 0.737 and an equivalent 113.6 W/ton for a system with an ECM blower.

h While certain high-efficiency equipment on the market today may utilize the benefits of variable speed fan 

operation, it was assumed that this would not be a required feature for equipment built to meet a standard with a fullload (e.g., EER) efficiency rating metric.
7-6 

Each of these latter two metrics is used as an input to the EnergyPlus simulation model and 

represents the performance of the cooling equipment’s refrigeration component without the 

supply fan power and corresponding heat gain into the supply air stream. They are calculated by 

backing out the estimated supply fan power at nominal rating conditions from the rated energy 

consumption while simultaneously accounting for the effect of fan heat. This is done for the 

condenser-only cooling COP and condenser-only heating COP using the following equations: 

COPCU_Cool =

CAPC

3.413 + AHRIFanPower

CAPC

EER − AHRIFanPower

Eq. 7.1 

COPCU_Heat =

CAPh

3.413 − AHRIFanPower

CAPh

COPx3.413 − AHRIFanPower

Eq. 7.2 

Where: 

COPCU_Cool = condenser-only cooling COP, 

COPCU_Heat = condenser-only heating COP,

CAPc = cooling capacity at Air-Conditioning, Heating, and Refrigeration Institute (AHRI) rating 

conditions (Btu/h), 

CAPh = heating capacity at AHRI rating conditions (Btu/h), 

EER = rated energy efficiency ratio (Btu/W) at AHRI rating conditions, 

COP = heating rated coefficient of performance at AHRI rating conditions, and 

AHRIFanPower = supply fan power at AHRI rating conditions. 

The estimated AHRIFanPower for equipment with PSC and ECM blower motors and the 

nominal rating conditions for SPVAC and SPVHP equipment as discussed above were used to 

develop the condenser-only cooling and heating COP values. The calculated COPCU_Cool and 

COPCU_Heat are shown in Table 7.2.1 for each EER and COP combination developed in the 

engineering analysis. 

Capacity and efficiency performance curves as a function of indoor and outdoor 

conditions representative of SPVAC and SPVHP equipment were developed for this simulation 

analysis and are provided in appendix 7A. 
7-7 

Table 7.2.1 Development of Condenser-Only COP Values by Efficiency Level

Efficiency Level EER COP* AHRIFanPower

W/ton COPCU_Cool COPCU_Heat* 

EPCA** Baseline 9.0 3.0 154.4 3.113 3.303

ASHRAE Baseline 10.0 3.0 113.6 3.341 3.214

1† 10.5 3.2 113.6 3.526 3.453

2† 11.0 3.3 113.6 3.714 3.574

3† 11.75 3.9 113.6 3.999 4.317

4† 12.3 3.9 113.6 4.211 4.317

* Heat pumps only.

** EPCA is the Energy Policy and Conservation Act of 1975, as amended by the Energy Independence and Security Act of 2007. 

† Efficiency Level applies to SPVAC <65,000 Btu/h and SPVHP <65,000 Btu/h equipment classes only.

7.2.4 Simulated Climates and Weather Data

DOE used typical meteorological year (TMY3) weather data for each of 237 locations for

the EnergyPlus simulations.11 The locations correspond to 237 U.S. climate locations for which 

DOE had previously generated state weighting factors. DOE sized equipment for each building 

simulation using a design-day sizing approach incorporating the design data found in the 

EnergyPlus design-day weather data files for each location.

i

 DOE also incorporated an 

additional cooling sizing factor of 1.1 for the equipment used in the modular office and modular 

classroom simulations, reflective of the typical sizing adjustment needed to account for discrete 

available equipment capacities in SPVAC and SPVHP equipment. As stated earlier, DOE did not 

incorporate additional sizing factors for the telecommunication equipment. 

7.2.5 Energy Use Extraction and Aggregation to State Level Data 

From the annual simulation results for buildings using SPVAC and SPVHP equipment in 

each climate, DOE extracted the condenser energy use for cooling, the supply air blower energy 

use for both heating and cooling hours, the electric resistance heating energy, and the equipment 

capacity for each building type, climate, and efficiency level. DOE developed corresponding 

normalized annual cooling energy per cooling ton and annual blower energy per cooling ton for 

the SPVAC equipment at the efficiency simulated by dividing the annual energy use data for 

each end-use by the total building cooling capacity in tons. In addition, the normalized electrical

heating energy per ton was calculated by dividing the electrical heating energy use by the total 

building cooling capacity in tons for the building. In the case of SPVAC equipment, this per-ton 

heating energy use was based on electric resistance heating. In the case of SPVHP equipment, 

this per-ton heating energy was based on the sum of the compressor heating energy and the 

electrical resistance heating energy provided. 

The per-ton cooling, fan, and heating energy use were then individually aggregated to 

state-level estimates. For each state, relative weighting factors associated with each TMY 

location were used based on previously developed climate weights. DOE used population-based 

weighting factors developed for each of the 237 TMY climates based on detailed population 

 

i

EnergyPlus TMY3-based weather data files and design day data files available at: 

<http://apps1.eere.energy.gov/buildings/energyplus/weatherdata_about.cfm> 
7-8 

statistics from the U.S. Geological Survey (USGS) Populated Places dataset to weight each 

climate in each state. The development and documentation of these weighting factors is found in 

appendix 7B. The original weighting factors were developed based on 239 TMY212 locations. As

DOE used the more recent TMY3 weather files for the energy simulations, DOE first identified 

all TMY2 locations with a corresponding TMY3 weather file. DOE did not include the TMY2 

island locations of San Juan, Puerto Rico, and Guam in the development of state-level data, 

which reduced the data set to 237 locations for this analysis. 

For each combination of equipment class, building type, climate, and efficiency level, 

DOE developed per-ton cooling, blower, and heating annual energy consumption values for each 

simulation by location, and aggregated these to corresponding state values using the previously 

discussed weighting factors to establish the contribution of each climate to each state. Once 

developed at the state level, these per-ton energy end-use estimates were multiplied by the 

representative cooling capacity estimated for the equipment class being modeled (3 or 6 tons). 

This provided state-average cooling, blower, and heating annual energy consumption for both 

equipment sizes. 

To be consistent with the energy uses typically associated with air-conditioning 

equipment and reported in other rulemaking analyses, DOE based the energy use for SPVAC 

equipment on cooling and fan energy only and did not include total heating energy in the overall 

UEC. However, the analysis indicated that where fan power was reduced for higher efficiency 

levels (10 EER and above), there was a corresponding non-trivial increase in the amount of 

heating required in each climate to make up for the loss of heat energy imparted into the supply 

air stream through the use of the more-efficient supply air blower during the heating season. The 

scale of this impact was climate dependent, with little heating impact in warm climates, and 

greater heating impact in cold climates where space heating requirements dominate during the 

year. To account for this heating energy impact, for each climate, DOE calculated a heating “take 

back” effect for higher efficiency levels as a deviation from the baseline heating energy use per 

ton for each SPVAC equipment capacity and efficiency level. The final SPVAC energy 

consumption estimates were then based on the calculated cooling and supply blower energy uses 

plus this heating “take back,” which allowed the energy savings estimates to correctly account 

for the heating energy increase during the year that occurs at certain high efficiency levels when 

using higher efficiency blower motors. 

An example of the impact of the heating take back is shown below for a modular office 

in Atlanta, Georgia, for a 3-ton SPVAC unit at the ASHRAE baseline efficiency level relative to 

the EPCA baseline level using the data shown in Table 7.2.2. 

Table 7.2.2 Calculation of UEC for Office Building in Atlanta, GA

Cooling Energy 

kWh/yr-ton

Blower Energy 

kWh/yr-ton

Heating Energy 

kWh/yr-ton

Total Energy 

kWh/yr-ton

EPCA Baseline 1,091 600 4,294 5,986

ASHRAE 

Baseline 992 455 4,364 5,812

Heating Take

Back

70
7-9 

UEC_SPVACi,j = (Cooling_energy_per_toni,j + Blower_energy_per_toni,j 

+ Heating_takeback _per_toni,j) × Representative Capacity (tons) 

Eq. 7.3 

Where: 

Cooling_energy_per_toni,j = Cooling_energy_per_ton for climate i at efficiency level j, 

Blower_energy_per_toni,j = Blower_energy_per_ton for climate i at efficiency level j, and 

Heating_takeback_per_toni,j = Heating_energy_per_ton for climate i at efficiency level j – 

Heating_energy_per_ton for climate i at the baseline efficiency level. 

Using Eq. 7.3, the SPVAC UEC for 3-ton cooling equipment used in modular offices in

Atlanta at the ASHRAE baseline is as follows. 

UEC_SPVACAtlanta, ASHRAE Baseline = [992 kWh/yr-ton + 455 kWh/yr-ton + (4,364 

kWh/yr-ton – 4,294 kWh/yr-ton)] × 3 tons 

UEC_SPVACAtlanta, ASHRAE Baseline = 4,551 kWh/yr 

Eq. 7.4 

The analysis method for SPVHP equipment included the heating energy (compressor 

heating and electric resistance backup) directly from the simulation results in developing the 

UEC by climate, and thus DOE did not separately calculate a heating “take back” effect.

The results of the steps described above, taken for each building type and equipment 

class, provided the annual expected energy consumption for each SPVAC or SPVHP class for 

each combination of building type, climate, and efficiency level. 

Once state-level UEC estimates for each equipment class were established, they were 

provided to the LCC analysis. National average UEC estimates for each equipment class and 

efficiency were also established based on population-based weighting across states and shipment 

weights to the different building types. See chapter 8 of the notice of proposed rulemaking 

(NOPR) TSD for discussion of weighting across states and building types. With regard to the 

latter, while DOE established shipment weights for SPVAC equipment to three building types 

(education, office, and telecommunication), DOE determined that SPVHP equipment was not 

used to a significant extent in telecommunication facilities and thus only allocated shipments of 

SPVHP equipment to two building types: education and office. 

7.2.6 Calculation of Gas Heating Impact

Based on discussions with manufacturers in the engineering model development, it was 

estimated that approximately 5 percent of the market for the SPVAC less than 65,000 Btu/h class 

utilizes gas furnace heating, and thus the corresponding heating take back is an effect on gas heat 

consumption. To account for this, DOE multiplied the heating take back for the simulated 

SPVAC equipment, based on electric resistance heat, by the ratio of the electric resistance heat 

generation efficiency (assumed 100 percent) to an assumed gas heating efficiency. The gas 
7-10

heating efficiency was based on an estimated 81 percent furnace annual fuel utilization 

efficiency. The gas heating take back was then converted to annual thousand British thermal 

units (kBtu) of natural gas for monetizing the purchases in the LCC. 

7.3 ENERGY USE ANALYSIS RESULTS

Figure 7.3.1 shows the national average EPCA baseline UEC estimates for each 

equipment class by building type assuming electric heat and based on the state population 

weights discussed in chapter 8 of the NOPR TSD. UEC for SPVAC equipment includes cooling 

energy and supply fan energy only. UEC for SPVHP equipment includes cooling, supply fan, 

and heating energy consumption. SPVHP heating energy use results in much higher UEC figures 

than SPVAC equipment for both modular classrooms and offices. For the telecommunication 

shelters modeled, internal gains provide essentially all the heating energy needed for the 

buildings within the defined control temperature range. As such, no heating energy use is seen in 

the models, and SPVAC and SPVHP UEC figures are the same for the same capacity equipment. 

In addition, for modular offices and classrooms, the 6-ton equipment uses slightly less than twice 

the energy as the 3-ton equipment at the baseline efficiency level for both equipment types. 

While 6-ton baseline units have a lower EER than 3-ton baseline units (8.5 vs. 8.9), they also 

benefit from greater use of economizers in the analysis. By contrast, the UEC estimate for 

baseline 6-ton units serving the telecommunication shelters is slightly more than twice that of the 

3-ton telecommunication unit due only to the difference in baseline EER for the two sizes. 

Figure 7.3.1 Baseline National Unit Energy Consumption Estimates by Building Type 
7-11

Table 7.3.1 shows the national average annual UEC estimates for SPVAC and SPVHP 

equipment corresponding to the EER and COP levels analyzed, when weighted across building 

types, states, and heating fuel types. These estimates presume shipments for SPVAC equipment 

to education, office, and telecommunication sectors at 35 percent, 30 percent, and 35 percent, 

respectively, of the entire market for SPVAC equipment, as detailed in chapter 9 of the NOPR 

TSD. For SPVHP equipment, DOE presumed that heating energy needs were such that 

telecommunication shelter manufacturers would not purchase SPVHP equipment. As such, 

shipment weightings for SPVHP equipment were apportioned only to the education and office 

building use categories at 54 percent and 46 percent, respectively. See chapter 9 of the NOPR

TSD for details. UEC estimates by state for each equipment class are found in the LCC analysis 

spreadsheet tool, and are discussed in chapter 8. 

Table 7.3.1 National UEC Estimates for SPVAC and SPVHP Equipment 

Efficiency Level

Equipment Class

SPVAC <65 kBtu/h SPVHP <65 

kBtu/h

SPVAC, ≥65 and 

<135 kBtu/h

SPVHP ≥65 and 

<135 kBtu/h

kWh/yr Gas 

kBtu/yr* kWh/yr kWh/yr kWh/yr

EPCA Baseline 6,880 - 20,921 13,743 41,721

ASHRAE Baseline** 6,175 54 20,383 12,251 40,589

Level 1 5,923 54 19,921 NA NA

Level 2 5,694 54 19,629 NA NA

Level 3 5,387 54 18,775 NA NA

Level 4** 5,185 54 18,633 NA NA * Calculated average gas heating “take back” per unit based on 5 percent of market with gas heat. ** ASHRAE baseline represents max-tech levels established for SPVAC and SPVHP equipment greater than or equal to 65,000 

Btu/h, but less than 135,000 Btu/h. Level 4 represents max-tech levels established for SPVAC and SPVHP equipment less than 

65,000 Btu/h.
7-12

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