NREL is a national laboratory of the U.S. Department of Energy

Office of Energy Efficiency & Renewable Energy

Operated by the Alliance for Sustainable Energy, LLC

This report is available at no cost from the National Renewable Energy

Laboratory (NREL) at www.nrel.gov/publications.

Contract No. DE-AC36-08GO28308

Healthcare Energy End-Use 

Monitoring

Michael Sheppy, Shanti Pless, and Feitau Kung

National Renewable Energy Laboratory

Technical Report

NREL/TP-5500-61064

August 2014
NREL is a national laboratory of the U.S. Department of Energy

Office of Energy Efficiency & Renewable Energy

Operated by the Alliance for Sustainable Energy, LLC

This report is available at no cost from the National Renewable Energy

Laboratory (NREL) at www.nrel.gov/publications.

Contract No. DE-AC36-08GO28308

National Renewable Energy Laboratory

15013 Denver West Parkway

Golden, CO 80401

303-275-3000 • www.nrel.gov

Healthcare Energy End-Use 

Monitoring 

Michael Sheppy, Shanti Pless, and Feitau Kung

National Renewable Energy Laboratory

Prepared under Task No. ARCB1301

Technical Report

NREL/TP-5500-61064

August 2014
NOTICE

This report was prepared as an account of work sponsored by an agency of the United States government. 

Neither the United States government nor any agency thereof, nor any of their employees, makes any warranty, 

express or implied, or assumes any legal liability or responsibility for the accuracy, completeness, or usefulness of 

any information, apparatus, product, or process disclosed, or represents that its use would not infringe privately 

owned rights. Reference herein to any specific commercial product, process, or service by trade name, 

trademark, manufacturer, or otherwise does not necessarily constitute or imply its endorsement, recommendation, 

or favoring by the United States government or any agency thereof. The views and opinions of authors 

expressed herein do not necessarily state or reflect those of the United States government or any agency thereof.

This report is available at no cost from the National Renewable Energy

Laboratory (NREL) at www.nrel.gov/publications.

Available electronically at http://www.osti.gov/scitech

Available for a processing fee to U.S. Department of Energy

and its contractors, in paper, from:

U.S. Department of Energy

Office of Scientific and Technical Information

P.O. Box 62

Oak Ridge, TN 37831-0062

phone: 865.576.8401

fax: 865.576.5728

email: mailto:reports@adonis.osti.gov

Available for sale to the public, in paper, from:

U.S. Department of Commerce

National Technical Information Service

5285 Port Royal Road

Springfield, VA 22161

phone: 800.553.6847

fax: 703.605.6900

email: orders@ntis.fedworld.gov

online ordering: http://www.ntis.gov/help/ordermethods.aspx

Cover Photos: (left to right) photo by Pat Corkery, NREL 16416, photo from SunEdison, NREL 17423, photo by Pat Corkery, NREL 

16560, photo by Dennis Schroeder, NREL 17613, photo by Dean Armstrong, NREL 17436, photo by Pat Corkery, NREL 17721.

NREL prints on paper that contains recycled content.
iii

This report is available at no cost from the National Renewable Energy Laboratory (NREL) at www.nrel.gov/publications.

Acknowledgments

The authors would like to thank the U.S. Department of Energy’s (DOE) Building Technologies 

Office for its support of this project. This report was prepared by the National Renewable Energy 

Laboratory’s (NREL) Buildings and Thermal Systems Center under Task Number ARCB.1301.

The authors would like to thank the following partners for their energy monitoring and data 

contributions:

• Partners HealthCare and Massachusetts General Hospital (MGH) in Boston, 

Massachusetts

• The State University of New York Upstate Medical University (SUNY UMU) in 

Syracuse, New York

• Mazzetti, Inc.

We also acknowledge the input of Brian Ball and William Livingood of NREL during project 

planning, and we thank Ross Reucker of Mazzetti for sharing data from his work with medical 

offices. We also thank the following individuals for reviewing drafts of this document: Michael 

Deru and Ron Judkoff of NREL; Paul Holliday of Holliday Electrical Mechanical Engineering; 

Andrew Maynard and Chris Longchamps of Partners HealthCare; and Ron Westbrook of SUNY 

UMU.
iv

This report is available at no cost from the National Renewable Energy Laboratory (NREL) at www.nrel.gov/publications.

Executive Summary

Hospital facility and energy managers find it challenging to identify the energy inefficiencies in 

their buildings, because the industry lacks measured energy use data for major hospital end uses, 

such as cooling, heating, lighting, and plug loads. Historically, when these managers have 

compared alternative energy efficiency investments for various end-use systems, their 

benchmarks have been limited to end-use estimates derived from modeling.

To address this challenge, DOE commissioned NREL to partner with two hospitals (MGH and 

SUNY UMU) to collect data on the energy used for multiple thermal and electrical end-use 

categories, including preheat, heating, and reheat; humidification; service water heating; cooling; 

fans; pumps; lighting; and select plug and process loads. Additional data from medical office 

buildings were provided for an analysis focused on plug loads. Facility managers, energy 

managers, and engineers in the healthcare sector will be able to use these results to more 

effectively prioritize and refine the scope of investments in new metering and energy audits. 

Highlighted findings include:

• For the MGH Gray Building in Boston, Massachusetts, Table ES-1 lists the end-use 

categories with the highest site energy use intensities (EUIs). Whole-building meters 

were also available at this site, enabling estimation of end-use percentages relative to 

total building energy consumption.

Table ES-1 MGH Gray: End-Use Categories With the Highest EUIs

Site EUI 

(kBtu/ft·yr)

% of Building 

Site Energy 

Use

Reheat and Heating 108.4 27%

Lighting and Other Electric Loads (e.g., Plug) 86.2 21%

Steam Piping Losses 58.5 14%

Fans (Supply, Return, and Exhaust) 51.0 13%

Chiller Plant Energy (Chillers, Cooling Tower Fans, 

Cooling System Pumps) Allocated to Building 42.3 10%
v

This report is available at no cost from the National Renewable Energy Laboratory (NREL) at www.nrel.gov/publications.

• For the SUNY UMU East Wing in Syracuse, New York, Table ES-2 lists the end-use 

categories with the highest site EUIs. 

Table ES-2 SUNY UMU: End-Use Categories With the Highest EUIs

Site EUI 

(kBtu/ft·yr)

Fans (Supply and Return/Exhaust) 63.0

Reheat and Heating 53.6

Lighting 28.9

Chiller Energy Allocated to Building 26.8

Pumps 14.4

• The variability in the medical imaging equipment load profiles and the nighttime power 

consumption of some medical office building plug loads suggest an opportunity for 

device manufacturers and healthcare stakeholders to examine device operational modes 

more closely to determine if improvements can be made to: (1) the energy efficiency of 

“idle” modes; and (2) built-in controls for transitions between operational modes. An 

example of the first case is that, when medical devices remain at full power in a medical 

office building during non-business hours, such devices should be assessed more 

carefully to determine which ones can be powered down. An example of the second case 

is that manufacturers should consider designing controls that can reduce idle power while 

ensuring fast response and emergency readiness.
vi

This report is available at no cost from the National Renewable Energy Laboratory (NREL) at www.nrel.gov/publications.

Nomenclature

AHU air handling unit

ATS automatic transfer switch

BMS building management system

Btu British thermal units 

CT computed tomography

CTs current transducers

DEM digital energy meter 

EUI energy use intensity

HVAC heating, ventilation, and air conditioning

kW kilowatt

MGH Massachusetts General Hospital

MRI magnetic resonance imaging

SUNY UMU State University of New York Upstate Medical University

UPS uninterruptible power supply

VFD variable frequency drive
vii

This report is available at no cost from the National Renewable Energy Laboratory (NREL) at www.nrel.gov/publications.

Contents

Acknowledgments ......................................................................................................................................iii

Executive Summary................................................................................................................................... iv

Nomenclature ............................................................................................................................................. vi

Contents ..................................................................................................................................................vii

Figures and Tables ...................................................................................................................................viii

Figures ....................................................................................................................................viii

Tables ....................................................................................................................................viii

1.0 Background and Motivation................................................................................................................1

2.0 Overview of Hospitals in This Study..................................................................................................2

2.1 Massachusetts General Hospital: The Gray Building.................................................................. 2

2.2 The State University of New York Upstate Medical University: The East Wing ............................. 2

3.0 Analysis of Major End Uses................................................................................................................3

3.1 End-Use Energy for the Massachusetts General Hospital Gray Building...................................... 3

3.2 End-Use Energy for the State University of New York Upstate Medical University 

East Wing............................................................................................................................... 6

4.0 Medical Equipment in Hospitals and Medical Office Buildings ....................................................10

4.1 Hospital Medical Imaging Equipment ...................................................................................... 10

4.2 Medical Office Building Plug Loads......................................................................................... 16

5.0 Conclusions........................................................................................................................................20

5.1 End-Use Data for Informing Decisions .................................................................................... 20

5.2 Considerations for Medical Equipment .................................................................................... 20

6.0 References..........................................................................................................................................21

Appendix A: Hospital End-Use Energy Metering Methodology ..........................................................22

A.1 Data Collection for the Massachusetts General Hospital Gray Building ............................. 22

Preheat, Heating, and Reheat........................................................................................................................22

Humidification ...................................................................................................................................................22

Service Water Heating ....................................................................................................................................22

Cooling and Dehumidification ........................................................................................................................22

Fans ................................................................................................................................................................23

Pumps................................................................................................................................................................24

Lighting ..............................................................................................................................................................25

Large Hard-Wired Medical Imaging Equipment ..........................................................................................25

Elevators ...........................................................................................................................................................25

A.2 Data Collection for the State University of New York Upstate Medical University 

East Wing............................................................................................................................ 25

Preheat, Heating, and Reheat........................................................................................................................25

Humidification ...................................................................................................................................................26

Service Water Heating ....................................................................................................................................26

Cooling and Dehumidification ........................................................................................................................26

Fans ................................................................................................................................................................26

Pumps................................................................................................................................................................26

Interior Ambient Lighting.................................................................................................................................27

Large Hard-Wired Medical Imaging Equipment ..........................................................................................27

Operating Room Plug Loads..........................................................................................................................27

Appendix B: Sources of Uncertainty in End-Use Measurements and Calculations .........................28

Appendix C: Additional Medical Office Building Plug Load Data.......................................................31

Appendix D: Additional Resources........................................................................................................34
viii

This report is available at no cost from the National Renewable Energy Laboratory (NREL) at www.nrel.gov/publications.

Figures and Tables

Figures

Figure 3-1 MGH Gray Building: 1 year of monthly site energy end-use breakdowns.....................5

Figure 3-2 SUNY UMU East Wing: one year of monthly site energy end-use breakdowns............8

Figure 4-1 Frequency of CT power measurements rounded to the nearest 1 kW.........................11

Figure 4-2 Frequency of MRI power measurements rounded to the nearest 1 kW .......................12

Figure 4-3 CT 15-minute load profiles for an example weekend day (Sunday) .............................14

Figure 4-4 CT 15-minute load profiles for an example weekday (Wednesday)..............................14

Figure 4-5 MRI 15-minute load profiles for an example weekend day (Sunday)............................15

Figure 4-6 MRI 15-minute load profiles for an example weekday (Wednesday)............................15

Figure 4-7 Medical office plug loads (with peak power lower than 40 W) ......................................18

Figure 4-8 Medical office plug loads (with peak power higher than 40 W).....................................19

Tables

Table ES-1 MGH Gray: End-Use Categories With the Highest EUIs.................................................. iv

Table ES-2 SUNY UMU: End-Use Categories With the Highest EUIs................................................. v

Table 2-1 Location, Age, and Square Footage of the Hospitals.......................................................2

Table 3-1 MGH Gray Building: Annual End Use Summary...............................................................4

Table 3-2 SUNY UMU East Wing: Annual End Use Summary ..........................................................7

Table 4-1 CT and MRI Power Summary ............................................................................................13

Table 4-2 Medical Office Building Characteristics ..........................................................................16

Table 4-3 Summary of Medical Office Medical Plug Load Data .....................................................17

Table 4-4 Plug Load Location Abbreviations...................................................................................18

Table C-1 Medical Office Building 1: Plug and Process Load Data by Panel and Department...31

Table C-2 Medical Office Building 1: Plug and Process Load Data by Space Type .....................31

Table C-3 Medical Office Building 2: Plug and Process Load Data by Department.....................32

Table C-4 Medical Office Building 2: Plug and Process Load Data by Department.....................32

Table C-5 Medical Office Building 3: Plug and Process Load Data by Department/Space 

Type ....................................................................................................................................33

Table C-6 Medical Office Building 5: Plug and Process Load Data by Space Type .....................33
1

This report is available at no cost from the National Renewable Energy Laboratory (NREL) at www.nrel.gov/publications.

1.0 Background and Motivation

Hospital facility and energy managers find it challenging to identify the energy inefficiencies in 

their buildings, because the industry lacks measured energy use data for major hospital end uses, 

such as cooling, heating, lighting, and plug loads. Historically, when these managers have 

compared alternative energy efficiency investments for various end-use systems, their 

benchmarks have been limited to end-use estimates derived from modeling. 

To address this challenge, the U.S. Department of Energy (DOE) commissioned the National 

Renewable Energy Laboratory (NREL) to partner with two hospitals to collect data on the 

energy used for multiple thermal and electrical end-use categories, including preheat, heating, 

and reheat; humidification; service water heating; cooling; fans; pumps; lighting; and select plug 

and process loads. The hospital partners in this study were Massachusetts General Hospital 

(MGH) and the State University of New York Upstate Medical University (SUNY UMU). 

Additional data from medical office buildings were provided for an analysis focused on plug 

loads. Facility managers, energy managers, and engineers in the healthcare sector will be able to 

use these results to more effectively prioritize and refine the scope of investments in new 

metering and energy audits. A list of complementary resources is also provided in Appendix D, 

including the “Targeting 100!” hospital end-use energy study conducted by the University of 

Washington (Hatten et al. 2011) and hospital benchmarking work conducted by Lawrence 

Berkeley National Laboratory (LBNL 2014).
2

This report is available at no cost from the National Renewable Energy Laboratory (NREL) at www.nrel.gov/publications.

2.0 Overview of Hospitals in This Study

This study included two hospitals in which major end uses were monitored. The hospital 

locations, ages, and square footage are summarized in Table 2-1. Both sites are located in 

Climate Zone 5A as defined by the 2006 International Energy Conservation Code and ASHRAE 

Standard 90.1.

Table 2-3 Location, Age, and Square Footage of the Hospitals

MGH: Gray Building SUNY UMU: East Wing

City Boston, MA Syracuse, NY

Year Built 1966 1995

Total Floor Space 332,664 ft2 143,000 ft2

2.1 Massachusetts General Hospital: The Gray Building

MGH is a 900-bed medical center located in the heart of Boston, Massachusetts, that offers 

diagnostic and therapeutic care in multiple specialties of medicine and surgery through four 

Boston area health centers. The hospital also holds concurrent Level 1 verification for adult and 

pediatric trauma and burn care.

The Gray Building is an inpatient facility located at 90 Blossom Street on the MGH campus. The 

building has 16 floors above ground, a basement, and a subbasement for a total floor area of 

332,664 ft2. It was built in 1966 and has been renovated substantially over the years. 

Space types in the Gray Building include: exam rooms; treatment rooms; procedure rooms; 

operating rooms; research laboratory space; patient rooms; mechanical/electrical spaces; 

corridors, elevators, and stairs; offices; storage; and common areas.

2.2 The State University of New York Upstate Medical University: The East Wing

The East Wing, also known as the Concentrated Care Center, is a seven-story addition to SUNY 

UMU Hospital in Syracuse, New York. Opened in 1995, the building has a total gross floor area 

of approximately 143,000 ft2.

The East Wing was built to provide expanded services that were formerly located in the 

University Hospital plus new service groups, including: the emergency medicine department; a 

diagnostic imaging center with three computed tomography (CT) units and two magnetic 

resonance imaging (MRI) units; the endoscopy department; 58 single-patient intensive care 

rooms, including 14 infectious isolation rooms and two protective environment rooms; and a 

pharmacy with pharmacy prep laboratories. All areas of the East Wing are used for hospital 

services and were covered in this monitoring study.
3

This report is available at no cost from the National Renewable Energy Laboratory (NREL) at www.nrel.gov/publications.

3.0 Analysis of Major End Uses

The figures and tables in this section summarize end-use energy consumption for the two 

monitored hospitals. Each hospital had a different metering approach based on site-specific 

conditions, including different systems and differences in the organization of existing electrical 

circuitry, so some of the end-use categories differ. The metering methodology for each building 

is documented in Appendix A, and a discussion of sources of uncertainty in end-use 

measurements and calculations is provided in Appendix B.

3.1 End-Use Energy for the Massachusetts General Hospital Gray Building

At the MGH Gray Building, the end-use categories that consumed the most annual site energy 

were: reheat and heating (27% combined); “other electric loads (including lighting)” (21%); 

steam piping distribution losses (14%); fans (13%); and chiller plant energy allocated to this 

building (10%). Its overall site energy use intensity (EUI) was 407 kBtu/ft2·yr. Annual and 

monthly totals are summarized in Table 3-1 and Figure 3-1. The source energy calculation uses 

simplified typical site-to-source factors of 1.21 for steam and 3.34 for grid electricity (EPA 

2011).
4

This report is available at no cost from the National Renewable Energy Laboratory (NREL) at www.nrel.gov/publications.

Table 3-4 MGH Gray Building: Annual End Use Summary

End-Use Category

Form of 

Energy 

Supply

Site 

MWh/yr

Site 

MMBtu/yr

Site EUI 

(kBtu/ft•yr)

% of 

Building 

Site 

Energy 

Use

Source 

MWh/yr

Source 

MMBtu/yr

Source 

EUI 

(kBtu/ft•yr)

% of 

Building 

Source

Energy 

Use

Supply Fans Electricity 2,917 9,952 29.9 7.3% 9,742 33,239 99.9 11.3%

Return Fans Electricity 700 2,389 7.2 1.8% 2,339 7,980 24.0 2.7%

Exhaust Fans Electricity 1,355 4,622 13.9 3.4% 4,524 15,436 46.4 5.2%

Pumps for Hot Water and Heat Recovery Steam 162 553 1.7 0.4% 196 670 2.0 0.2%

Reheat and Heating Steam 10,573 36,075 108.4 26.6% 12,793 43,651 131.2 14.8%

Preheat Steam 2,730 9,314 28.0 6.9% 3,303 11,270 33.9 3.8%

Humidification Steam 2,025 6,910 20.8 5.1% 2,451 8,361 25.1 2.8%

Domestic Hot Water Steam 431 1,470 4.4 1.1% 521 1,779 5.3 0.6%

Chiller Plant Energy (Chillers, Cooling 

Tower Fans, Cooling System Pumps) 

Allocated to Building

Electricity 4,128 14,084 42.3 10.4% 13,787 47,040 141.4 15.9%

Elevators Electricity 371 1,267 3.8 0.9% 1,240 4,232 12.7 1.4%

Medical Imaging Electricity 193 657 2.0 0.5% 643 2,195 6.6 0.7%

Other Electric Loads* Electricity 8,400 28,659 86.2 21.2% 28,055 95,722 287.7 32.4%

Steam Piping Losses Steam 5,700 19,449 58.5 14.4% 6,897 23,533 70.7 8.0%

Building Total Energy Use

Electricity 

and 

Steam

39,684 135,403 407 100.0% 86,492 295,109 887 100.0%

*The “other electric loads” category includes lighting systems and plug and process load equipment that were not directly monitored during the study.
5

This report is available at no cost from the National Renewable Energy Laboratory (NREL) at www.nrel.gov/publications.

Figure 3-1 MGH Gray Building: 1 year of monthly site energy end-use breakdowns

Reheat and heating are coupled in the same measurement, but some information about these end 

uses can be inferred by reviewing the monthly data. From December 2011 through March 2012, 

cooling is minimal, so the “reheat and heating” energy is assumed to be predominantly heating 

energy. Similarly, during July and August 2012, this building is unlikely to have required 

significant heating, so the “reheat and heating” energy is assumed to be predominantly reheat 

energy. If the percent contributions of reheat and heating are interpolated for other months, an 

estimate of the annual site energy breakdown between reheat and heating would be 13,000 
6

This report is available at no cost from the National Renewable Energy Laboratory (NREL) at www.nrel.gov/publications.

MMBtu/yr for reheat and 23,000 MMBtu/yr for heating. This would mean that reheat and 

heating consume 10% and 17% of annual whole-building site energy use, respectively.

The “other electric loads” category includes lighting systems and plug and process load 

equipment that were not directly monitored during the study. Energy consumption for this 

category was estimated by taking readings from a whole-building electric meter (excluding the 

chiller plant) and subtracting readings from electric end-use meters.

Similarly, energy consumption for the steam piping losses category was estimated by taking 

readings from a whole-building steam meter and subtracting readings from the steam end-use 

meters. Based on the steam end-use metering plan used in this building, one would expect the 

whole-building steam consumption value to be greater than the sum of the monitored steam enduse consumption values, because additional thermal losses occur from distributing steam 

throughout the building.

One apparent anomaly is that steam piping losses appear higher in summer months than in winter 

months. At the time of this report, this was being investigated. Sources of uncertainty are 

discussed further in Appendix B.

3.2 End-Use Energy for the State University of New York Upstate Medical 

University East Wing

At the SUNY UMU East Wing, the end-use categories with the highest annual site EUIs were: 

fans (63.0 kBtu/ft2

·yr); reheat and heating (53.6 kBtu/ft2·yr combined); lighting (28.9 

kBtu/ft2·yr); chiller energy allocated to this building (26.8 kBtu/ft2·yr); and pumps (14.4

kBtu/ft2

·yr). Monitoring at this site excluded cooling tower fans, six small fans with fractional 

horsepower motors, preheat, humidification, steam piping losses, plug loads, and a 10-ton 

process cooling unit that serves the rooms with MRI devices. In order to install meters for many 

of the excluded electrical loads, it would have been necessary to interrupt hospital operations, 

which was not practical. The site did not have whole-building meters for steam or electricity, but 

annual and monthly totals for monitored end uses are summarized in Table 3-2 and Figure 3-2. 

The source energy calculation uses simplified typical site-to-source factors of 1.21 for steam and 

3.34 for grid electricity (EPA 2011).
7

This report is available at no cost from the National Renewable Energy Laboratory (NREL) at www.nrel.gov/publications.

Table 3-5 SUNY UMU East Wing: Annual End Use Summary

End-Use Category

Form of 

Energy Supply

Site 

MWh/yr

Site 

MMBtu/yr

Site EUI 

(kBtu/ft•yr)

Source 

MWh/yr

Source 

MMBtu/yr

Source EUI 

(kBtu/ft•yr)

Fans (Supply and 

Return/Exhaust) Electricity 2,639 9,004 63.0 8,814 30,073 210.3

Pumps Electricity 604 2,061 14.4 2,018 6,884 48.1

Chiller Energy Allocated to 

Building Electricity 1,122 3,828 26.8 3,747 12,785 89.4

Lighting Electricity 1,211 4,133 28.9 4,046 13,805 96.5

Medical Imaging Electricity 345 1,178 8.2 1,154 3,936 27.5

Reheat Loop (Reheat and 

Heating) Steam 2,181 7,440 52.0 2,639 9,003 63.0

Radiation Loop (Heating) Steam 65 222 1.6 79 269 1.9

Domestic Hot Water Steam 14 48 0.3 17 58 0.4
8

This report is available at no cost from the National Renewable Energy Laboratory (NREL) at www.nrel.gov/publications.

Additionally, during April 2013, plug load data were collected for multiple operating rooms and 

extrapolated to the total operating room area, as discussed in Appendix A. Total operating room 

plug load energy was estimated to have a monthly site EUI of 1.7 kBtu/ft2

·mo in April. 

Assuming these loads are fairly constant throughout the year, extrapolating this result to other 

months results in an estimated annual site EUI of 21.2 kBtu/ft2

·yr. 

Figure 3-2 SUNY UMU East Wing: one year of monthly site energy end-use breakdowns

In Figure 3-2, the “reheat loop” provides both reheat and heating; thus, the reheat loop values are 

positive in months with little or no cooling. As with the MGH Gray Building, some information 

about reheat and heating in the SUNY UMU East Wing can be inferred from review of the 

monthly data. From January through March 2013, cooling is minimal, so the “reheat and

heating” energy is assumed to be predominantly heating energy. Similarly, during July and 

August 2012, this building is unlikely to have required significant heating, so the “reheat and 

heating” energy is assumed to be predominantly reheat energy. If the percent contributions of 
9

This report is available at no cost from the National Renewable Energy Laboratory (NREL) at www.nrel.gov/publications.

reheat and heating are interpolated for other months, an estimate of the annual site energy 

breakdown between reheat and heating would be 4,300 MMBtu/yr for reheat and 3,100 

MMBtu/yr for heating. This would mean that reheat and heating have annual site EUIs of 30.2 

kBtu/ft2·yr and 29.2 kBtu/ft2·yr, respectively.

One anomaly was that radiation loop energy use was negative (–1 MMBtu) in June and July 

2012. The SUNY UMU team investigated and reported that the radiation pumps were not 

switched off when heating was not needed, so they continuously circulated water throughout the 

system during the summer. On very warm days, the radiation loop would pick up heat from 

spaces such as stair towers, which were normally unoccupied and uncooled, causing the radiation 

energy use to appear negative.
10

This report is available at no cost from the National Renewable Energy Laboratory (NREL) at www.nrel.gov/publications.

4.0 Medical Equipment in Hospitals and Medical Office Buildings

Medical equipment energy is unique to the healthcare sector, so facility and energy managers 

may be particularly interested in data for this end-use category. This section includes additional 

detail on medical equipment devices that were directly monitored at the SUNY UMU East Wing. 

It also includes a summary of data provided by Mazzetti, Inc., from a plug load study that it 

conducted in five medical office buildings in California.

4.1 Hospital Medical Imaging Equipment

At the SUNY UMU East Wing, three CT units and two MRI units were monitored for 1 year 

with power measured at 15-minute intervals. Figure 4-1 and Figure 4-2 depict how often the 

measured power was at various magnitudes.

Most CT measurements fell within a range of about 1 to 15 kW, and most MRI measurements 

fell within a range of about 8 to 20 kW, but there were sporadic instances of higher power. In 

Figure 4-1 and Figure 4-2, the “over” bin indicates how often the measured power exceeded 30 

kW. The maximum power recorded for each device ranged from 33 to 111 kW, depending on the 

device.
11

This report is available at no cost from the National Renewable Energy Laboratory (NREL) at www.nrel.gov/publications.

Figure 4-3 Frequency of CT power measurements rounded to the nearest 1 kW
12

This report is available at no cost from the National Renewable Energy Laboratory (NREL) at www.nrel.gov/publications.

Figure 4-4 Frequency of MRI power measurements rounded to the nearest 1 kW

The average, minimum, and maximum power measurements for the CT and MRI units are 

summarized in Table 4-1, which shows that the peak power is much higher than the average 

power for each unit. CT 1 and CT 2 have lower average power requirements than the other three 

devices, and the emergency department CT has the highest peak power of the five devices (111 

kW).
13

This report is available at no cost from the National Renewable Energy Laboratory (NREL) at www.nrel.gov/publications.

Table 4-6 CT and MRI Power Summary

Device Avg kW Min kW Max kW

CT 1 3 0 67

CT 2 3 0 65

CT 3 (Emergency Department) 11 0 111

MRI 1 13 0 33

MRI 2 11 4 54

Average power for these units may be of interest to engineers who need to estimate internal gains 

when sizing heating, ventilation, and air-conditioning (HVAC) systems. On the other hand, 

engineers who are concerned with electrical power system impacts may be interested in peak 

power and more comprehensive load profiles. The load profiles tend to vary with time of day and 

day of the week. Load profiles for an example weekend day and an example weekday are 

depicted in Figure 4-3 through Figure 4-6.

The 15-minute data from this study are informative for engineers who are interested in

understanding potential impacts of these devices on electricity demand charges, because such 

charges are often based on data collected at 15-minute intervals. To characterize different modes 

of operation, however, a finer data collection interval would be necessary, because operational 

modes and power input for medical imaging equipment can vary significantly within a 15-minute 

span.

Engineers should be cautioned that medical imaging equipment power input can vary with 

functionality, and different CT and MRI devices can have different average power, peak power, 

and load profiles. Load profiles also depend on usage patterns, which are expected to vary from 

hospital to hospital, or even from department to department.
14

This report is available at no cost from the National Renewable Energy Laboratory (NREL) at www.nrel.gov/publications.

Figure 4-5 CT 15-minute load profiles for an example weekend day (Sunday)

Figure 4-6 CT 15-minute load profiles for an example weekday (Wednesday)
15

This report is available at no cost from the National Renewable Energy Laboratory (NREL) at www.nrel.gov/publications.

Figure 4-7 MRI 15-minute load profiles for an example weekend day (Sunday)

Figure 4-8 MRI 15-minute load profiles for an example weekday (Wednesday)
16

This report is available at no cost from the National Renewable Energy Laboratory (NREL) at www.nrel.gov/publications.

4.2 Medical Office Building Plug Loads

Mazzetti, Inc., conducted an in-depth metering study of plug loads in five medical office 

buildings in California. Building characteristics are summarized in Table 4-2. Mazzetti’s 

estimates of plug load densities (Watts per square foot) for a variety of departments and space 

types in these buildings are summarized in Appendix C.

Table 4-7 Medical Office Building Characteristics

Location

Facility 

Age 

(Years)

Square 

Footage Functions

Building 1 28 50,950 Adult Medicine, Family Medicine, Flu Clinic, Optometry, Pediatrics, 

Pharmacy, Radiology/Diagnostic Imaging, Women's Health

Building 2 5 160,883

Adult Medicine, Ambulatory Surgery, Cancer Center 

(Chemotherapy/Infusion, Hematology, Oncology, Radiation 

Oncology), Dermatology, Health Education, Internal Medicine, 

Laboratory, Neurology, Occupational and Employee Health, 

Pediatric Rehabilitation, Pharmacy, Therapy

Building 3 90 43,050 Dermatology, EEG Sleep Laboratory, Head & Neck Surgery, 

Neurology, Orthopedic Surgery, Podiatry, Urology

Building 4 15 243,329

Cardiology, Dermatology, EKG, Infusion Center, Injury Center and 

Sports Medicine, Internal Medicine, Laboratory, Obstetrics & 

Gynecology, Oncology, Orthopedics, Radiology/Diagnostic 

Imaging, Urgent Care - After Hours

Building 5 11 21,434 Ambulatory Surgery

At two of the medical office buildings, Mazzetti measured power input to a range of specific 

medical plug load devices at 15-minute intervals. Depending on the device, the monitoring 

period ranged from about 13 to 48 hours. Average, minimum, and maximum power 

measurements are summarized in Table 4-3, Figure 4-7, and Figure 4-8; location abbreviations 

are listed in Table 4-4.

Some plug loads had a fairly consistent power input; others had widely ranging power input. 

Plug loads with a high minimum power, such as one of the exam chairs, may represent 

opportunities for energy savings. Such loads could be investigated on a case-specific basis to 

determine whether devices can be switched off or to a lower power mode during nonbusiness 

hours.
17

This report is available at no cost from the National Renewable Energy Laboratory (NREL) at www.nrel.gov/publications.

Table 4-8 Summary of Medical Office Medical Plug Load Data

Device and Location Abbreviation

First 

Timestamp

Last 

Timestamp Avg W Min W Max W

Blood Pressure Cuff, S1, Hea Sun 00:00 Mon 01:00 3.99 0.64 6.08

Blood Pressure Cuff, S1, InfInf Sun 00:00 Mon 16:00 3.92 3.77 4.88

Blood Pressure Device, S2, Inf Thu 05:00 Thu 19:45 3.93 3.77 4.88

Electrosurgical Unit, S1, DerExa Sun 00:00 Mon 23:45 5.85 5.76 5.94

Electrosurgical Unit, S1, DerPro Sun 00:00 Mon 23:45 0.53 0.00 5.26

Electrosurgical Unit, S1, HeaPro Sun 00:00 Mon 01:00 0.41 0.00 14.73

Exam Bed, S1, DerExa Sun 00:00 Mon 23:45 2.53 2.44 2.64

Exam Bed, S1, DerPro Sun 00:00 Mon 23:45 26.26 25.63 28.42

Exam Bed, S1, InfExa Sun 00:00 Mon 16:00 1.36 1.33 1.51

Exam Bed, S1, InfInf Sun 00:00 Mon 16:00 1.28 1.22 2.58

Exam Bed, S1, InfMin Sun 00:00 Mon 16:00 2.27 2.16 3.92

Exam Bed, S2, Exa Thu 05:00 Thu 19:45 1.35 1.33 1.37

Exam Bed, S2, Min Thu 07:00 Thu 19:45 1.35 1.33 1.37

Exam Chair, S1, HeaExa Sun 00:00 Mon 01:00 27.50 27.12 27.83

Exam Chair, S1, HeaPro Sun 00:00 Mon 01:00 5.28 0.00 179.73

Exam Chair, S2, Inf Thu 05:00 Thu 19:45 1.32 1.22 2.58

Exam Light, S1, DerExa Sun 00:00 Mon 23:45 0.06 0.00 5.66

Exam Light, S1, InfExa Sun 00:00 Mon 16:00 0.01 0.00 2.18

Infusion Pump, S1, InfInf Sun 00:00 Mon 16:00 11.51 11.49 11.56

Infusion Pump, S2, Inf Thu 05:00 Thu 19:45 11.51 11.49 11.53

Phototherapy Equipment, S1, DerPho Sun 00:00 Mon 23:45 5.05 3.82 37.67

Smoke Evaporator, S1, DerPro Sun 00:00 Mon 23:45 0.27 0.00 21.97

Surgical Clipper, S1, DerPro Sun 00:00 Mon 23:45 2.88 2.78 3.01

Surgical Light 1, S1, HeaPro Sun 00:00 Mon 01:00 10.75 7.37 125.66

Surgical Light 2, S1, HeaPro Sun 00:00 Mon 01:00 3.36 0.00 185.62

Vital Signs Monitor, S1, InfInf Sun 00:00 Mon 16:00 5.47 5.44 5.60

Vital Signs Monitor, S2, Inf Thu 05:00 Thu 19:45 5.46 5.44 5.60
18

This report is available at no cost from the National Renewable Energy Laboratory (NREL) at www.nrel.gov/publications.

Table 4-9 Plug Load Location Abbreviations

Abbr. Description Abbr. Description

S1 Site 1 (25–48 hours) HeaExa Head and Neck Surgery Exam Room

S2 Site 2 (about 13 hours) HeaPro Head and Neck Surgery Procedure Room

DerExa Dermatology Exam Room Inf Infusion Center

DerPro Dermatology Procedure Room InfExa Infusion Center Exam Room

DerPho Dermatology Phototherapy InfMin Infusion Center Minor Procedure

Exa Exam Room InfInf Infusion Center Infusion Station

Hea Head and Neck Surgery Min Minor Procedure

Figure 4-9 Medical office plug loads (with peak power lower than 40 W)
19

This report is available at no cost from the National Renewable Energy Laboratory (NREL) at www.nrel.gov/publications.

Figure 4-10 Medical office plug loads (with peak power higher than 40 W)
20

This report is available at no cost from the National Renewable Energy Laboratory (NREL) at www.nrel.gov/publications.

5.0 Conclusions

End-use data from this study provided several valuable insights, including the following key 

ideas.

5.1 End-Use Data for Informing Decisions

The relative magnitude of the energy consumption of different end uses can be a starting point 

for prioritizing energy investments and action, whether the scope under consideration involves 

new metering, targeted energy audits, or end-use equipment upgrades. To inform such decisions, 

options for acquiring data for comparing end use energy consumption include:

1. Facility and energy managers can begin by assessing their current metering capabilities. 

For a link to guidance about how to build up metering capabilities, starting with no- and 

low-cost actions, see Appendix D.

2. For healthcare facilities without end-use level metering capabilities, facility and energy 

managers can review the data in this report to decide whether their facilities have 

characteristics (e.g., size, vintage, function, climate) that are similar to those of the 

hospitals in this study.

If the buildings are similar, facility and energy managers may wish to use the findings to 

help them prioritize early actions in an energy investment decision process, such as 

deciding where to invest first when expanding metering capabilities or defining the scope 

of a targeted energy audit.

The monitored facilities do not represent a statistically significant sample of hospitals; however, 

the data can help others to prioritize where to invest next in metering strategies or audits that can 

gather information specific to their hospitals.

5.2 Considerations for Medical Equipment

Medical equipment is unique to the healthcare sector, so facility and energy managers may be 

particularly interested in how medical equipment energy consumption compares to that of other 

hospital end uses. A comprehensive assessment of medical devices was outside the scope of this 

study, but several large, hard-wired, medical imaging devices were monitored. At both hospitals, 

these devices accounted for less than 5% of annual site energy use. In the near term, this 

percentage suggests that facility managers at other hospitals should start with other, larger end 

uses if they do not yet have end-use metering and want to increase metering capabilities.

On the other hand, the variability in the medical imaging equipment load profiles and the 

nighttime power consumption of some medical office building plug loads suggest an opportunity 

for device manufacturers and healthcare stakeholders to examine device operational modes more 

closely to determine if improvements can be made to: (1) the energy efficiency of “idle” modes; 

and (2) built-in controls for transitions between operational modes. An example of the first case 

is that, when medical devices remain at full power in a medical office building during nonbusiness hours, such devices should be assessed more carefully to determine which ones can be 

powered down. An example of the second case is that manufacturers should consider designing 

controls that can reduce idle power while ensuring fast response and emergency readiness.
21

This report is available at no cost from the National Renewable Energy Laboratory (NREL) at www.nrel.gov/publications.

6.0 References

EPA. (2011). Methodology for Incorporating Source Energy Use. Accessed from 

http://www.energystar.gov/ia/business/evaluate_performance/site_source.pdf. 

EPA. (2014). Healthcare Resources. Accessed from http://www.energystar.gov/buildings/sectorspecific-resources/healthcare-resources. 

Federal Energy Management Program. (2011). Metering Best Practices: A Guide to Achieving 

Utility Resource Efficiency. Release 2.0. Accessed from 

http://www1.eere.energy.gov/femp/pdfs/mbpg.pdf. 

Hatten, M.; Van Houten, B.; Burpee, H.; Loveland, J. (2011). Targeting 100! Energy Use and 

Model Calibration Study: Legacy Salmon Creek Medical Center. University of Washington. 

http://idlseattle.com/t100/TOL_DWN.php. 

LBNL. (2014). “Benchmarking: Healthcare Facilities.” Accessed from 

http://hightech.lbl.gov/benchmarking-hcf.html. 

NIST. (2014). “The NIST Reference on Constants, Units, and Uncertainty.” Accessed from 

http://physics.nist.gov/cgi-bin/cuu/Info/Uncertainty/combination.html. 

NREL. (2011). Healthcare Energy Metering Guidance. NREL Brochure No. BR-5500-50942. 

Golden, CO: National Renewable Energy Laboratory. 

http://www.nrel.gov/docs/fy11osti/50942.pdf. 

Sheppy, M.; Beach, A.; Pless, S. (2013). Metering Best Practices Applied in the National 

Renewable Energy Laboratory’s Research Support Facility: A Primer to the 2011 Measured and 

Modeled Energy Consumption Datasets. NREL Report No. TP-5500-57785. Golden, CO.: 

National Renewable Energy Laboratory. http://www.nrel.gov/docs/fy13osti/57785.pdf.

Torcellini, P.; Pless, S.; Deru, M.; Griffith, B.; Long, N.; Judkoff, R. (2006). Lessons Learned 

from Case Studies of Six High-Performance Buildings. NREL Report No. TP-550-37542. 

Golden, CO: National Renewable Energy Laboratory. 

http://www.nrel.gov/docs/fy06osti/37542.pdf. 
22

This report is available at no cost from the National Renewable Energy Laboratory (NREL) at www.nrel.gov/publications.

Appendix A: Hospital End-Use Energy Metering Methodology

At MGH and SUNY UMU, time-series energy end-use data were collected over a period of 1 

year and disaggregated by major end use. All meters were monitored at intervals no greater than 

15 minutes throughout the year. 

A.1 Data Collection for the Massachusetts General Hospital Gray Building

The following sections summarize the major end uses monitored in the Gray Building.

Preheat, Heating, and Reheat

Heating-related end uses were monitored at AHUs and at terminal boxes. At this site, preheat 

was defined to include thermal energy input at the AHUs, which was used when needed to raise 

the supply air temperature to 55°F. 

The thermal energy input at the terminal boxes included a combination of heating and reheat 

energy. Energy input at this location was defined as reheat if it was preceded by cooling; 

otherwise, it was defined as heating.

The source of heat for these systems is district steam, and the building has no boilers. Steam is 

used at the preheat coils in the AHUs; at the heat exchangers serving the reheat hot water loop; 

directly at the humidifiers; and for the domestic water heaters. Steam for the building was 

measured with a steam meter. The steam consumption through each meter was monitored at an 

interval no greater than 15 minutes. The steam consumption for the preheat coils was calculated 

by measuring the temperature rise through the preheat coil and volumetric airflow rate across the 

coil.

Reheat is accomplished with individual hot water reheat coils at variable air volume terminals 

throughout the HVAC system. Hot water is provided through steam-to-hot water converters. The 

building reheat energy consumption was determined by using Btu meters consisting of supply 

and return hot water temperature sensors and flow meters on these loops. 

Humidification

The humidifiers use district steam directly and are located at the central AHUs. The quantity of 

steam used for humidification was determined by subtracting preheat energy and fan energy 

from the measured heat gain at the AHUs.

Service Water Heating 

Steam is used to heat domestic water using steam converters. Steam energy consumption for this 

application was determined by using flow meters at the domestic hot water systems and 

calculating the difference between temperature measurements for the water entering and leaving 

the converters. 

Cooling and Dehumidification

Chilled water is provided from a central plant that is located in this building and serves multiple 

buildings. The cooling capacity consumed by the Gray Building and the total capacity generated 

at the plant were measured using Btu meters, each of which consists of a flow meter, supply 

temperature sensor, and return temperature sensor.
23

This report is available at no cost from the National Renewable Energy Laboratory (NREL) at www.nrel.gov/publications.

The cooling tower energy, condenser water pump energy, chilled water pump energy, and chiller 

energy of the entire plant were measured as described in the following subsections. The energy 

consumed by each system was allocated in proportion to the chiller capacity consumed by this 

building in relation to the amount generated by the plant. The data were captured at an interval of 

no less than 15 minutes throughout the year. These measured data were used to calculate the 

following variables with respect to the chiller plant:

Chiller plant capacity (tons of cooling)

Building cooling usage (tons of cooling)

Building consumption compared to plant capacity (%)

Cooling tower fan energy (building percentage)

Condenser water pump energy (building percentage)

Chilled water pump energy (building percentage)

Chiller energy (building percentage)

Entire plant efficiency (kW/ton).

Cooling Tower Fan Energy 

Six open-cell cooling towers serve this plant. Each cooling tower fan is controlled through a 

variable frequency drive (VFD). Current transducers (CTs) measured amperage to enable 

monitoring of power input to the cooling tower fans. A constant voltage (480 V) and a constant 

power factor (0.85) were assumed based on data from previous metering efforts. (The same 

voltage and power factor assumption was used for all fans and pumps in this building.)

Chiller Energy 

Five chillers are used to produce chilled water in the spring, summer, and fall, and one flat plate 

heat exchanger is used for “free cooling” in the winter.

Three of the chillers are 800-ton units, and two of the chillers are 1,500-ton units. CTs measured 

amperage to enable monitoring of power input to the chillers. Four of five chillers use VFDs to 

modulate the compressor speed and are controlled directly by the chiller manufacturer control 

system, which is integrated with the building management system (BMS). The BMS directly 

controls the 1,500-ton chiller that does not have a VFD.

The building also uses a flat plate heat exchanger with an 800-ton capacity. The unit does not 

consume electricity directly.

Fans

Supply Fans (in Air Handling Units)

Before this study, most AHU supply fans already had CTs installed on their feeders. The power 

consumption of AHU supply fans was calculated by using the measured amperage and a 

predetermined voltage and power factor. Before the data collection phase, amperage was 

measured and recorded at fan speed intervals of 10%, starting at 10% and continuing to full 

speed. These measurements were performed for each AHU. Power input to each fan was 
24

This report is available at no cost from the National Renewable Energy Laboratory (NREL) at www.nrel.gov/publications.

calculated and uploaded into a database at 15-minute intervals throughout the project. The 

airflow and discharge static pressures were also measured and collected at the same interval.

Return Fans 

Energy consumption of return fans was measured via the same approach used for the AHU 

supply fans.

Exhaust Fans 

The exhaust fans are constant volume. The amperage and voltage for each fan motor were 

measured at the start, midway point, and end of the project. The status of each fan was 

continuously monitored and uploaded to a database at 15-minute intervals.

Ventilation Fans (Mechanical and Electrical Spaces) 

The ventilation fans are constant volume. The amperage and voltage for each fan motor were 

measured at the start, midway point, and end of the project. The status of each fan was 

continuously monitored and uploaded to a database at 15-minute intervals.

Pumps

The pumps serving this building include:

Hot water pumps

Heat recovery pumps

Domestic water booster pumps

Chilled water pumps

Condenser water pumps.

The energy consumption for each pump was monitored. The amperage and voltage for each 

pump motor were measured at the start, midway point, and end of the project. The status of each 

pump was continuously monitored and uploaded to a database at 15-minute intervals.

Chilled water and condenser water pumping energy are described in greater detail in the

following subsections. Pumping energy was allocated to the building based on the portion of 

cooling capacity the building consumed as a percentage of chiller plant production. This 

calculation was required because the chiller plant serves multiple buildings.

Condenser Water Pumping Energy 

All these condenser water pumps are controlled by VFDs. CTs measured the amperage of the 

electrical input, which was used to determine power.

Chilled Water Pumping Energy 

All the primary chilled water pumps are constant volume and do not have VFDs. Their power 

consumption was determined with CTs.

All the secondary chilled water pumps were controlled by VFDs. CTs measured the amperage of 

the electrical input, which was used to determine power.
25

This report is available at no cost from the National Renewable Energy Laboratory (NREL) at www.nrel.gov/publications.

Lighting

The energy consumption of lighting systems was not directly monitored in the Gray Building. 

An estimate of the combination of lighting loads and miscellaneous plug loads was derived by 

subtracting other monitored loads from whole-building electricity consumption.

Large Hard-Wired Medical Imaging Equipment

All medical imaging equipment in the Gray Building is fed from a dedicated imaging branch that 

is fed from both normal and emergency power via an automatic transfer switch (ATS). 

Individual imaging equipment feeders are fed from a dedicated distribution panel that is served 

by the ATS. The combined energy consumption of six fluoroscopy X-ray devices was measured 

at the normal power feeder circuit breaker to the imaging ATS by the circuit breaker trip unit and 

uploaded to the database at 15-minute intervals throughout the entire length of the project. The 

discrete meter in the ATS serving the imaging distribution panel was used for validation of 

consumption data.

Elevators

All elevators in the Gray Building are fed from a dedicated elevator branch. An ATS allows the 

elevators to be fed by either normal or emergency power. Individual elevator feeders are fed 

from a dedicated distribution panel that is served by the ATS. Total elevator energy consumption 

was measured at the normal power switchgear using a discrete metering device and uploaded 

into a database at 15-minute intervals throughout the project. The discrete meter in the ATS 

serving the distribution panel was used to validate consumption data. 

Other specific plug and process loads were not directly monitored as part of this study.

A.2 Data Collection for the State University of New York Upstate Medical 

University East Wing

The following sections summarize the major end uses monitored in the East Wing. 

Preheat, Heating, and Reheat

Heating for the SUNY UMU hospital buildings is provided by a university-owned and -operated 

boiler plant consisting of three boilers, each with a net capacity of 43.5 million pounds of steam 

at 125 pounds per square inch gauge. The boilers are primarily supplied by gas with #2 fuel oil 

for backup. Boiler gas use is continuously monitored by a digital meter. Boiler output is 

measured by a steam meter in the primary distribution line and recorded by a chart recorder that 

does not have an electronic interface to the BMS. 

The East Wing has a system of hot water duct coils supplied by a central steam-to-hot water heat 

exchanger, which delivers constant temperature hot water to a building reheat loop. Energy use 

monitoring for the hot water coils was calculated using a flow meter on the heating supply and 

the temperature difference between the water entering and leaving the reheat converters. This 

metering point captured a combination of reheat and heating energy.

The East Wing also has a hot water radiation system. Steam-to-hot water heat exchangers deliver 

constant temperature hot water to unit heaters and a fin tube radiation system, which is used on 

the perimeter of the building to offset thermal transmission losses, as well as for spaces that do 

not receive heated air via the ventilation system. Energy use monitoring for the radiation loop 

system was calculated using a flow meter on the heating supply and the temperature difference 

between the water entering and leaving the radiation convertor.
26

This report is available at no cost from the National Renewable Energy Laboratory (NREL) at www.nrel.gov/publications.

Preheat coils on ventilation systems consist of low-pressure steam coils, but preheat energy was 

not directly measured.

Humidification

Humidification was not separately monitored during this study. The steam used for 

humidification is part of the energy used by the steam preheat coils.

Service Water Heating

The East Wing has semi-instantaneous steam water heaters that provide 120°- to 125-°F water 

for all areas of the building. Hot water in this building is mainly used for hand washing. This 

building has no major hot water process uses. (Primary sterilization is done in another facility.)

Energy use for the water heating system was determined by using a flow meter in the primary 

loop combined with temperature sensors on the entering and leaving water streams. 

Cooling and Dehumidification

The East Wing has two electric centrifugal chillers providing chilled water to cooling coils 

within the building. Energy use monitoring for the electric chillers was conducted by using data 

from manual log readings taken up to six times daily. Recorded voltages, amperages, and 

runtime hours were multiplied to determine daily total energy use.

The chillers served both the East Wing and part of a tower addition that was outside the scope of 

this study. The square footage of the East Wing is about 40% of the total square footage served 

by the chillers, so meter readings for the chillers were multiplied by 40% to estimate the portion 

of chiller energy that is attributable to the East Wing.

The East Wing and East Tower chillers use a common cooling tower, and its power is provided 

through the electric service to the East Tower (not the East Wing), which was not monitored in 

this study.

Fans

All HVAC fans and some exhaust fans are monitored by the BMS. Single-phase fan motors less 

than 1⁄2 horsepower were not monitored.

Energy monitoring was accomplished with a digital energy meter (DEM) that was added to 

monitor motor current draw through the BMS. A DEM is a product that collects data from 

devices such as CTs and can communicate data to a BMS or log data locally.

Pumps

All pumps except condensate and sanitary pumps are monitored by the BMS. The pumps 

monitored in this study included primary and secondary chilled water pumps, condenser water 

pumps, reheat loop hot water pumps, and radiation loop hot water pumps.

The condenser water pumps served both the East Wing building and part of a tower addition that 

was outside the scope of this study. The square footage of the East Wing is about 40% of the 

total square footage served by the condenser water pumps, so meter readings for the condenser 

water pumps were multiplied by 40% to estimate the portion of chiller energy that is attributable 

to the East Wing.

The monitored chilled water and hot water pumps were dedicated solely to serving the East 

Wing building, so 100% of their energy was included in the East Wing end-use calculations.
27

This report is available at no cost from the National Renewable Energy Laboratory (NREL) at www.nrel.gov/publications.

One pump (labeled “Pump P-3”) was a spare that could be manually lined up as either a 

condenser water pump or a chilled water pump, but its designation was not recorded by SUNY 

UMU. For the calculations in this report, this pump was assumed to be used equally for both 

purposes, and its meter readings were multiplied by 70% (the average of the aforementioned 

40% and 100% utilization factors).

Energy monitoring was accomplished with a DEM added to monitor motor current draw through 

the BMS.

Interior Ambient Lighting

The energy consumption of interior ambient lighting (which excludes task lighting) was 

monitored in the East Wing. The lighting systems include 277-V fluorescent troffers with a 

variety of 120-V T4 accent downlights and a few standard 120-V fixtures with compact 

fluorescent bulbs. Power for the 277-V lighting distribution is segregated from the receptacle 

power. 

Energy monitoring was accomplished with a DEM to record feeder current on the distribution 

riser.

Large Hard-Wired Medical Imaging Equipment

Several pieces of large medical imaging equipment are located in the East Wing. This study 

included monitoring of two MRI and three CT units.

Energy use monitoring was provided by a DEM in the branch circuit to each system. In some 

cases, these systems are supplied power via an uninterruptable power supply (UPS); for the UPSsupplied systems, the DEM was located on the discharge side of the UPS.

Operating Room Plug Loads

Toward the end of the project, DEMs were installed on part of the primary distribution panel 

serving the operating rooms, providing data for April 2013 for eight of the 14 operating rooms 

and one half of the recovery room. The SUNY UMU team extrapolated the measured data to the 

building’s total operating room area based on the plug load Watts per square foot found in the 

monitored fraction of the operating rooms.
28

This report is available at no cost from the National Renewable Energy Laboratory (NREL) at www.nrel.gov/publications.

Appendix B: Sources of Uncertainty in End-Use Measurements 

and Calculations

Uncertainty in commercial building energy end-use calculations has a variety of sources. Major 

sources of uncertainty include (but are not limited to) the following:

• Metering design for existing buildings is particularly challenging, given that many 

buildings do not have dedicated panels for energy end uses of interest; as a result, a single 

panel may feed circuits that serve multiple types of loads (e.g., lighting and plug loads). 

Furthermore, existing building electrical panels sometimes have poorly labeled circuits—

a problem that is exacerbated over time as space uses and equipment change, which can 

cause panel uses to change. These changes are not always well documented.

These factors complicate the design of metering systems, as well as verification and

troubleshooting of metered data. These factors can cause a variety of errors, including 

failing to capture certain loads, mischaracterizing circuits under incorrect end-use 

categories, and double-counting loads with multiple meters.

• In healthcare buildings such as hospitals, it may be infeasible to shut down circuits to 

install metering devices. This can limit the number of meters that can be installed for a 

particular end use. For example, when the SUNY UMU team attempted to monitor 

operating room plug load energy, the team was only able to access circuits for eight of 

the 14 operating rooms and one half of the recovery room. The SUNY UMU team 

extrapolated the measured data to the building’s total operating room area based on the 

plug load Watts per square foot found in the monitored fraction of the operating rooms. 

This is a less accurate approach than directly monitoring all rooms, but it reflects 

practical obstacles that are typical in a healthcare setting.

• Chiller plant energy allocations were estimated in both hospitals. In the MGH Gray 

Building, the allocation was based on using flow meters and temperature measurements 

to disaggregate the fraction of cooling capacity supplied to the monitored building. In the 

SUNY UMU East Wing, a comparable disaggregation was not feasible, and a simple 

square footage multiplier was applied, which introduces a potentially much greater source 

of error.

• In some cases, monitored equipment may serve multiple functions, which can complicate 

assignment of their energy use to the right category. Reheat coils in terminal boxes, for 

example, can serve both reheat and heating functions, depending on environmental 

conditions and how the HVAC system is controlled and operated. 

• Assumed constant values can introduce additional error. A few examples from this study 

include:

o The meters for fans and pumps in the MGH Gray Building were monitored by 

measuring current, but not voltage or power factor; the latter two values were 

assumed to be constant and were based on data from previous metering efforts.

o Measured motor speeds were used as a proxy for energy consumption. This is 

sometimes done by initially measuring motor current at a discrete set of motor 

speeds before a monitoring period begins; later, during the monitoring period, 

motor speed is measured as a proxy for current.
29

This report is available at no cost from the National Renewable Energy Laboratory (NREL) at www.nrel.gov/publications.

o The building steam meter recorded only mass flow. To translate this into an 

energy estimate, the building’s rate of steam energy consumption per unit mass of 

steam was assumed to be a constant 1,066 Btu/lbm—this value was estimated 

from conditions for the steam entering the building and the condensate leaving the 

building, which involved additional assumptions:

 The steam was assumed to enter the building at about 68 pounds per 

square inch gauge, based on the pressure set point of the district steam 

system. The metered quantity of steam was also assumed to be entirely 

saturated vapor, which at this pressure would be about 314°F. Differences 

in actual entering steam conditions are a potential source of error.

 The calculations also assumed that condensate left the building at a 

constant 150°F, because condensate temperature was not monitored. 

Building staff reported that condensate temperatures fluctuate between 

140° and 160°F, so the constant temperature assumption is a potential 

source of error.

These sources of uncertainty are typical in commercial building metering. When viewing the 

results of this and other end-use metering studies, engineers and facility managers should 

recognize that end-use breakdowns based on field data are approximations that reflect the 

practical constraints of implementing metering in existing, occupied, operational buildings.

An additional consideration is the measurement uncertainty associated with random instrument 

error and any uncorrelated error source. Such errors are calculated as follows. Suppose a value of 

interest, Y, takes the following form (NIST 2014):

Y = a1X1+ a2X2+ . . . aNXN (Equation 1)

where the values of X1 through XN are uncorrelated and can be estimated with measurements at 

points 1 through N. In such cases, the combined measurement error (excluding systematic bias) 

can be estimated with the following equation (NIST 2014):

uc(y) = �a1

2u12(x1) + a22u22(x2) + ... + aN

2 uN

2 (xN) (Equation 2)

where:

y = estimate of Y

x1...N = measured estimates of X1 through XN

uc = combined error

u1...N = error for measurements at points 1 through N

a1...N = coefficients from Equation 1

End-use power input or energy consumption can take the form of Equation 1, where Y is end-use 

power or energy, x1 through xN are power values from specific metering points, and each 

coefficient from a1 through aN equals 1. In such cases, Equation 2 reduces to:
30

This report is available at no cost from the National Renewable Energy Laboratory (NREL) at www.nrel.gov/publications.

uc = �� (ui

2) N

i=1 (Equation 3)

For any given end-use category with a reported energy consumption value, the combined 

measurement uncertainty for that value is therefore a function of the accuracy of the meters 

associated with the end-use category.

For some end uses in this study, there were insufficient data on meter specifications to quantify 

the combined measurement error, particularly if existing meters were involved. In other cases, 

sufficient data were available to estimate combined measurement error. For example, the enduse category of medical imaging equipment in the SUNY UMU East Wing was evaluated using 

five electrical meters, each associated with a different medical imaging device. Each meter had a 

reported accuracy of ± 1%. Applying Equation 3 to this case, the estimated combined 

measurement error associated with total medical equipment energy is:

�� (ui

2) N

i=1 = �5(±1%)2 = ±2.2% (Equation 4)
31

This report is available at no cost from the National Renewable Energy Laboratory (NREL) at www.nrel.gov/publications.

Appendix C: Additional Medical Office Building Plug Load Data

Table C-1 through Table C-6 summarize additional data provided by Mazzetti from its study of 

plug loads in medical office buildings. (For a summary of the buildings’ characteristics, see 

Section 4.2, Table 4-2.) For buildings 1, 2, 3, and 5, Mazzetti collected or estimated sufficient 

square footage data to generate department- and space-specific estimates of plug load Watts per 

square foot.

Table C-10 Medical Office Building 1: Plug and Process Load Data by Panel and Department

Panel Department Square 

Footage

Avg 

kW

Avg 

W/ft2 Peak kW

Peak 

W/ft2 kWh/wk kWh/ft2

·yr

L1A Primary Care 8,850 0.66 0.07 1.61 0.18 111 0.65

L1B Pediatrics 6,840 1.91 0.28 2.80 0.41 322 2.45

L1C

Shipping/Receiving, 

Tele. Equip. Room, 

Injection Room

6,400 3.26 0.51 7.80 1.22 547 4.45

L1D Laboratory 6,430 1.58 0.25 2.84 0.44 266 2.15

L2A Internal Medicine 5,930 1.48 0.25 3.67 0.62 248 2.18

L2B Surgery-O.B./GYN 5,720 2.65 0.46 4.47 0.78 445 4.04

EL1A L1A+L1D 15,280 0.66 0.04 1.29 0.08 111 0.38

EL1B L1B+L1C 13,240 1.55 0.12 3.43 0.26 260 1.02

EL2A Internal Medicine 5,930 0.96 0.16 2.86 0.48 161 1.41

EL2B Surgery-O.B./GYN 5,720 0.33 0.06 0.80 0.14 55 0.50

Table C-11 Medical Office Building 1: Plug and Process Load Data by Space Type

Space Type Square 

Footage

Avg 

kW

Avg 

W/ft2

Peak 

kW

Peak 

W/ft2 kWh/wk kWh/ft2

·yr

Waiting Area/Corridors 4,952 1.38 0.28 3.12 0.63 232 2.44

Reception 2,230 0.50 0.22 1.04 0.46 83 1.94

Exam Rooms 10,040 3.36 0.33 5.57 0.55 567 2.93

Offices 5,031 1.02 0.20 1.77 0.35 171 1.77

Nurse/Work Station 701 1.12 1.59 2.74 3.91 190 14.09

Breakroom/Lounge 320 0.03 0.09 0.79 2.47 6 0.90

Procedure/Operating Rooms 4,292 1.02 0.24 1.78 0.42 172 2.08

Imaging 1,935 0.88 0.46 1.83 0.95 151 4.06

Lab/Storage 1,394 0.27 0.19 0.69 0.50 45 1.69

Mechanical/Electrical Rooms 960 0.30 0.31 0.40 0.41 51 2.79

Other 8,765 1.68 0.19 5.72 0.65 285 1.69

Pharmacy 280 0.06 0.20 0.21 0.74 9 1.73
32

This report is available at no cost from the National Renewable Energy Laboratory (NREL) at www.nrel.gov/publications.

Table C-12 Medical Office Building 2: Plug and Process Load Data by Department

Department Square 

Footage

Avg 

kW

Avg 

W/ft2

Peak 

kW

Peak 

W/ft2 kWh/wk kWh/ft2

·yr

Oncology 12,800 7.37 0.58 11.24 0.88 1,238 5.03

Material Services/Biomed 2,500 0.83 0.33 1.62 0.65 140 2.91

Conference Rooms/

Classrooms 8,700 2.72 0.31 4.50 0.52 458 2.74

Neurology 12,000 1.30 0.11 6.17 0.51 218 0.95

Pharmacy and Medical Legal 12,000 0.23 0.02 0.81 0.07 39 0.17

Physical/Occupational 

Therapy Pediatric Rehab 24,000 5.35 0.22 10.22 0.43 899 1.95

Hemo/Oncology & Infusion 

Center 11,800 4.47 0.38 7.70 0.65 751 3.31

Eye Procedures, Hospice, 

Medical Transcription 12,200 2.64 0.22 7.44 0.61 444 1.89

Dermatology 10,500 2.49 0.24 11.05 1.05 419 2.08

Internal Medicine 13,500 3.13 0.23 5.88 0.44 526 2.03

Employee Health/

Occupational Health, Medical 

Staff Development

13,000 3.72 0.29 5.90 0.45 626 2.50

Medical Secretaries, Health 

Education Admin 11,000 4.85 0.44 9.03 0.82 816 3.86

Table C-13 Medical Office Building 2: Plug and Process Load Data by Department

Space Type Square 

Footage

Avg 

kW

Avg 

W/ft2

Peak 

kW

Peak 

W/ft2 kWh/wk kWh/ft2

·yr

Waiting Area/Corridors 4,520 0.30 0.07 1.01 0.22 51 0.58

Reception 840 1.33 1.58 3.78 4.50 223 13.79

Exam Rooms 8,810 3.09 0.35 6.14 0.70 520 3.07

Offices 5,100 2.02 0.40 5.00 0.98 339 3.45

Nurse/Work Station 5,740 3.03 0.53 7.00 1.22 509 4.61

Breakroom/Lounge 1,890 1.63 0.86 6.36 3.37 274 7.54

Prep Area, Pre-Op 800 3.93 4.91 5.34 6.67 660 42.88

Procedure/Operating Rooms 3,690 0.79 0.21 2.12 0.57 133 1.87

Imaging/Linear Accelerator 3,590 3.02 0.84 9.14 2.55 507 7.34

Lab/Storage 1,350 0.57 0.42 1.19 0.88 96 3.69

Mechanical/Electrical Rooms 1,835 2.89 1.57 3.81 2.08 485 13.75

Other 5,400 0.77 0.14 2.89 0.54 130 1.25

Conference/Meeting Areas 5,075 0.37 0.07 1.51 0.30 62 0.63

Pharmacy 300 0.90 3.01 0.94 3.14 152 26.27
33

This report is available at no cost from the National Renewable Energy Laboratory (NREL) at www.nrel.gov/publications.

Table C-14 Medical Office Building 3: Plug and Process Load Data by Department/Space Type

Department/Space Type Square 

Footage

Avg 

kW

Avg 

W/ft2

Peak 

kW

Peak 

W/ft2 kWh/wk kWh/ft2

·yr

Head & Neck Surgery 12,000 2.57 0.21 6.71 0.56 432 1.87

Dermatology 12,000 1.92 0.16 6.92 0.58 322 1.40

Urology, Neurology, EEG/

Sleep Lab 12,000 1.96 0.16 4.45 0.37 329 1.43

Orthopedics & Podiatry 6,000 0.51 0.08 1.87 0.31 86 0.74

Cast Room 2,000 0.23 0.11 0.47 0.24 38 1.00

Waiting Area & Reception 1,500 0.62 0.42 1.37 0.91 105 3.63

Procedure Room 2,500 0.93 0.37 3.04 1.21 157 3.26

Table C-15 Medical Office Building 5: Plug and Process Load Data by Space Type

Space Type Square 

Footage

Avg 

kW

Avg 

W/ft2

Peak 

kW

Peak 

W/ft2 kWh/wk kWh/ft2

·yr

Public/Waiting Area 2,246 0.33 0.15 0.54 0.24 55 1.27

Corridors/Auto Doors 3,568 0.18 0.05 0.47 0.13 30 0.44

Exam Rooms 404 0.73 1.82 2.12 5.26 124 16.00

Offices 400 0.04 0.11 0.26 0.65 9 1.14

Nurse/Work Stations 565 1.11 1.97 2.01 3.56 189 17.38

Breakroom/Lounge 572 1.06 1.85 2.53 4.43 195 17.72

Prep Area/Pre-Op 3,136 2.98 0.95 8.35 2.66 540 8.95

Procedure/Operating Rooms 2,840 1.22 0.43 4.99 1.76 241 4.41

Labs/Medical Storage 2,343 0.99 0.42 1.58 0.68 168 3.73

Mechanical/Electrical Rooms 2,690 0.00 0.00 0.08 0.03 1 0.02

Post-Op 2,662 1.83 0.69 2.52 0.95 309 6.04
34

This report is available at no cost from the National Renewable Energy Laboratory (NREL) at www.nrel.gov/publications.

Appendix D: Additional Resources

Research has shown that that metering leads to better energy management and improved energy 

performance (Torcellini et al. 2006). For hospital facility managers and energy managers who 

are interested in increasing metering capabilities at their sites, the following resources may be 

helpful:

• For a comprehensive guide on metering in commercial buildings, please refer to the 

Federal Energy Management Program’s (FEMP) Metering Best Practices guide at 

http://www1.eere.energy.gov/femp/pdfs/mbpg.pdf (FEMP 2011). This guide includes 

case study and success story information from the National Institutes of Health 

headquarters in Bethesda, Maryland, and a metering program at the U.S. Department of 

Veterans Affairs.

• For benchmarking resources that address hospitals and medical office buildings, see the 

ENERGY STAR® website at http://www.energystar.gov/buildings/sector-specificresources/healthcare-resources (EPA 2014). For follow-on benchmarking and 

measurement steps for major end uses, see the High-Performance Buildings for HighTech Industries website at http://hightech.lbl.gov/benchmarking-hcf.html (LBNL 2014).

• For a study of end uses from a hospital in Vancouver, Washington, see the “Targeting 

100!” reports at http://idlseattle.com/t100/TOL_DWN.php (Hatten et al. 2011).

• For a high-level summary of recommended steps for building a metering program for 

healthcare facilities, as well as examples of success from peer hospitals, see the 

Healthcare Energy Metering Guidance brochure at 

http://www.nrel.gov/docs/fy11osti/50942.pdf (NREL 2011).

• For a simple guide on data processing and analysis for commercial buildings, refer to 

Metering Best Practices Applied in the National Renewable Energy Laboratory’s 

Research Support Facility: A Primer to the 2011 Measured and Modeled Energy 

Consumption Datasets at http://www.nrel.gov/docs/fy13osti/57785.pdf. (Sheppy et al. 

2013).