FEMA P-1019 / September 2014

Emergency Power Systems for

Critical Facilities: A Best 

Practices Approach to

Improving Reliability

FEMA P-1019

Emergency Power Systems for Critical Facilities:

A Best Practices Approach to 

Improving Reliability

Prepared by

APPLIED TECHNOLOGY COUNCIL

201 Redwood Shores Parkway, Suite 240

Redwood City, California 94065

www.ATCouncil.org

Prepared for

FEDERAL EMERGENCY MANAGEMENT AGENCY

Michael Mahoney, Project Officer

Greg Wilson, Task Monitor

John Gillengerten, Technical Monitor

Washington, D.C.

ATC MANAGEMENT AND OVERSIGHT

Christopher Rojahn (Program Executive)

Jon A. Heintz (Program Manager)

Ayse Hortacsu (Project Manager)

PROJECT TECHNICAL COMMITTEE

Robert Bachman (Project Technical Director)

Donald Bliss

Philip Caldwell

David Low

Derek Wilson

Steven Winkel

PROJECT REVIEW PANEL

Chad Beebe

Robert Berninger

James Carlson

William Coulbourne

Therese McAllister

Steve Sappington

September 2014
Notice

Any opinions, findings, conclusions, or recommendations expressed in this publication do not necessarily 

reflect the views of the Applied Technology Council (ATC), the Department of Homeland Security 

(DHS), or the Federal Emergency Management Agency (FEMA). Additionally, neither ATC, DHS,

FEMA, nor any of their employees, makes any warranty, expressed or implied, nor assumes any legal 

liability or responsibility for the accuracy, completeness, or usefulness of any information, product, or 

process included in this publication. Users of information from this publication assume all liability 

arising from such use.
Preface

The importance of emergency power in keeping critical facilities operational 

during and after a major natural disaster was apparent with Hurricane Sandy

in 2012. FEMA P-942, Mitigation Assessment Team Report, Hurricane 

Sandy in New Jersey and New York (FEMA, 2013a), contains observations 

and recommendations that should be considered in planning for emergency 

power in the event of a disaster. In addition, hazard-specific guidance 

documents developed over the years, including FEMA E-74, Reducing the 

Risks of Nonstructural Earthquake Damage – A Practical Guide (FEMA, 

2012b) have addressed various aspects of protecting emergency power 

systems from the damaging effects of natural hazards.

In September 2013, the Federal Emergency Management Agency (FEMA) 

awarded the Applied Technology Council (ATC) a task entitled “Emergency 

Power for Critical Facilities Guidance” under its “Seismic Technical 

Guidance Development and Support” contract (HSFE60-12-D-0242). 

Funding for this task was made available under the Hurricane Sandy Federal 

Disaster Declaration (DR-4085). Designated the ATC-118 Project, the 

primary objective of this work was to create a unified guidance document on 

emergency power vulnerabilities faced by critical facilities during natural 

disasters, along with associated mitigation strategies and code requirements 

intended to minimize these vulnerabilities. 

ATC is indebted to the leadership of Bob Bachman, Project Technical 

Director, and to the members of the ATC-118 Project Team for their efforts 

in the development of this report. Work was performed and guided by the 

Project Technical Committee, consisting of Don Bliss, Phil Caldwell, David 

Low, Derek Wilson, and Steve Winkel. Technical review and comment at 

key stages of the project were provided by the Project Review Panel 

consisting of Chad Beebe, Bob Berninger, Jim Carlson, Bill Coulbourne, 

Mark Early, Terri McAllister, and Steve Sappington. Material forming the 

basis of this publication was developed under a prior contract, and David 

Low deserves special recognition for his efforts in developing the initial draft 

report and recommendations under that contract. The names and affiliations 

of all who contributed to this report are provided in the list of Project 

Participants.

FEMA P-1019 Preface iii
ATC gratefully acknowledges Michael Mahoney (FEMA Project Officer), 

Greg Wilson (FEMA Task Monitors), and John Gillengerten (FEMA 

Technical Monitor) for their input and guidance in the preparation of this 

report. ATC also acknowledges Ayse Hortacsu for project management, and 

Amber Houchen for report production services.

Jon A. Heintz Christopher Rojahn

ATC Director of Projects ATC Executive Director 

iv Preface FEMA P695
Table of Contents

Preface .......................................................................................................... iii

List of Figures .............................................................................................. ix

List of Tables.............................................................................................. xiii

1. Introduction...................................................................................... 1-1

1.1 Purpose..................................................................................... 1-2

1.2 Emergency Power from a Code Perspective ............................ 1-3

1.2.1 Emergency System...................................................... 1-3

1.2.2 Legally Required Standby System.............................. 1-3

1.2.3 Optional Standby System............................................ 1-4

1.2.4 Critical Operations Power System.............................. 1-4

1.3 Planning for Facility Resilience............................................... 1-4

1.4 Target Audience ....................................................................... 1-5

1.5 Report Organization ................................................................. 1-6

1.6 How to Use this Document ...................................................... 1-7

2. Natural Hazard Effects on Utilities and Building Systems.......... 2-1

2.1 Overview of Utility Power Transmission and Distribution 

Systems..................................................................................... 2-1

2.1.1 Failures of Transmission Systems............................... 2-1

2.2 Winter Storms .......................................................................... 2-3

2.2.1 Effects of Winter Storms on Power Lines .................. 2-4

2.2.2 Effects of Winter Storms on Building Systems .......... 2-6

2.2.3 Case Study – Winter Storms of 2007.......................... 2-6

2.3 High Winds .............................................................................. 2-7

2.3.1 Effects of High Winds on Power Lines....................... 2-9

2.3.2 Effects of High Winds on Building Systems .............. 2-9

2.3.3 Case Study – 2011 Tornadoes in the Southeastern 

United States ............................................................. 2-10

2.3.4 Case Study – Derecho Winds – June 2012 ............... 2-12

2.3.5 Case Study – 2012 Superstorm Sandy in Long 

Island ......................................................................... 2-12

2.4 Flooding ................................................................................. 2-13

2.4.1 Effects of Flooding on Power Lines.......................... 2-14

2.4.2 Effects of Flooding on Building Systems ................. 2-16

2.4.3 Case Studies.............................................................. 2-16

2.5 Earthquakes............................................................................ 2-18

2.5.1 Effects of Earthquakes on Power Lines and 

Sub-stations............................................................... 2-19

2.5.2 Effects of Earthquakes on Building Systems............ 2-20

2.5.3 Case Study – 1994 Northridge Earthquake............... 2-24

2.6 Other Events........................................................................... 2-25

2.6.1 Case Study - Solar Storms of 1989 and 2012............ 2-26

FEMA P-1019 Table of Contents v
2.6.2 Case Study 

– Northeast Blackout of 2003.................2-26

3. Disaster Management and Operations Continuity .......................3-1

3.1 Critical Facilities ......................................................................3-2

3.1.1 Determining if a Facility is Critical.............................3-4

3.2 Emergency Preparedness and Business Continuity 

Planning....................................................................................3-4

3.2.1 PS-Prep ........................................................................3-4

3.2.2 Issues to be Considered in the Disaster Preparedness 

Plan ..............................................................................3-8

4. Identifying Emergency Power Needs in Critical 

Facilities.............................................................................................4-1

4.1 Requirements for Emergency Power Specified by 

Building Codes and Standards........................................4-2

4.2 Emergency Power Requirements....................................4-3

4.3 Assessing Emergency Power Needs in Detail ................4-5

4.3.1 Life-Safety Equipment.......................................4-6

4.3.2 Fire Pumps.......................................................4-12

4.3.3 Lighting............................................................4-14

4.3.4 Mechanical Equipment ....................................4-15

4.3.5 Other Building Systems...................................4-21

5. Emergency Power Sources and Systems........................................5-1

5.1 Emergency Power Sources .............................................5-1

5.1.1 Stored Energy Devices.......................................5-1

5.1.2 Emergency and Standby Generators..................5-3

5.2 Emergency Power Distribution ....................................5-10

5.3 Optional Standby Generators........................................5-12

5.3.1 Providing Reliable Vehicle Access .................5-12

5.3.2 Creating a Location..........................................5-13

5.3.3 Installing Connections.....................................5-13

5.3.4 Ensuring Availability.......................................5-14

5.4 Electrical Control and Coordination.............................5-14

5.4.1 System Protection and Control ........................5-15

5.4.2 Selectivity and Coordination ...........................5-16

6. Design Considerations for Emergency Power Systems in New 

Facilities ............................................................................................6-1

6.1 Holistic Approach to Design ....................................................6-2

6.1.1 Determining Emergency Power Load 

Requirements...............................................................6-2

6.1.2 Emergency Power System Design...............................6-3

6.1.3 Holistic Design Tools and Culture ..............................6-4

6.2 Identification of Emergency Power Needs and Emergency 

Power Sources ..........................................................................6-4

6.3 Fire Protection, Mechanical, and Electrical Design 

Considerations that Affect Emergency Power Systems...........6-5

6.3.1 Fire Protection and Mechanical Engineering ..............6-5

6.3.2 Electrical Engineering .................................................6-8

6.4 Design Considerations Regarding the Layout, Location, and 

Protection of Emergency Power Systems.................................6-9

vi Table of Contents FEMA P-1019
6.4.1 Design Considerations for Reducing Flood Risks.... 6-10

6.4.2 Design Considerations for Reducing Risks from 

High Wind Events..................................................... 6-13

6.4.3 Recommendations for Placement where Earthquake 

Hazards are Present................................................... 6-15

6.5 Code Design Requirements for Emergency Power Systems to 

Resist Severe Natural Hazards............................................... 6-16

7. Design Considerations for Optional Standby Power Systems in 

Existing Facilities............................................................................. 7-1

7.1 Considerations for Determining Optional Standby and 

Emergency Power Demands in Existing Facilities.................. 7-2

7.1.1 Identifying Electrical Sources that Supply Critical 

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

7.1.2 Reconfiguring Electrical Distribution to Supply Only 

Critical Loads from Emergency or Alternate Power 

Source.......................................................................... 7-4

7.1.3 Providing Optional Standby Power through the 

Electrical Service ........................................................ 7-6

7.2 Protecting Optional Standby Power Systems from Natural 

Hazards..................................................................................... 7-8

Appendix A: General Code Considerations for Emergency Power in 

Critical Facilities............................................................................. A-1

A.1 History of Building Codes....................................................... A-1

A.2 Emergency Power Requirements of the International Building 

Code ........................................................................................ A-2

A.2.1 IBC Emergency Power Requirements by Occupancy 

Classification.............................................................. A-3

A.2.2 Emergency Power Duration Requirements................ A-6

A.3 Fire Pump Requirements......................................................... A-6

A.4 Critical Healthcare Facility Power Distribution 

Requirements........................................................................... A-7

Appendix B: Redundancy of Electrical Power Systems........................ B-1

B.1 Redundant Utility Source Delivery..........................................B-1

B.2 N+1 Redundancy Strategy .......................................................B-4

Appendix C: Generator Sizing ................................................................ C-1

C.1 Generator Load Requirements .................................................C-1

C.2 Continuous Generator Load .....................................................C-4

C.3 Maximum Allowable Voltage Dip...........................................C-5

C.4 Maximum Allowable Frequency Dip.......................................C-5

C.5 Caution on Oversizing Generators...........................................C-6

Appendix D: Emergency Power System Operational Checklist .......... D-1

Appendix E: Examples of How to Utilize this Document ......................E-1

E.1 Example 1 – New Facility........................................................E-1

E.1.1 Emergency Power Functions Determination...............E-2

E.1.2 Proposed Solution .......................................................E-3

E.1 Example 2 – Existing Facility ..................................................E-4

FEMA P-1019 Table of Contents vii
E.2.1 Analysis: Emergency Power Functions 

Determination ............................................................. E-4

E.2.2 Proposed Solution....................................................... E-5

References.................................................................................................. F-1

Project Participants..................................................................................G-1

viii Table of Contents FEMA P-1019
List of Figures

Figure 1-1 Flowchart illustrating example logic for determining 

emergency power needs and generator selection .............. 1-8

Figure 2-1 Illustration of a simplified utility transmission and 

distribution system............................................................. 2-2

Figure 2-2 Damage to overhead distribution line caused by weight of 

ice accumulation ................................................................ 2-4

Figure 2-3 Typical failure modes of overhead power lines................. 2-5

Figure 2-4 Riser pole of an underground electrical line supplied 

from an overhead line ........................................................ 2-5

Figure 2-5 Illustrated Enhanced Fujita scale....................................... 2-9

Figure 2-6 Tornado damage to transmission lines, Tuscaloosa, 

Alabama, April 2011.. ..................................................... 2-10

Figure 2-7 Collapsed building housing switchgear and emergency 

generator after the Joplin, Missouri Tornado .................. 2-12

Figure 2-8 Steel deck/steel joist URM building housing the 

emergency generator and switchgear destroyed in the 

Joplin, Missouri Tornado................................................. 2-12

Figure 2-9 Example for map from FEMA Flood Map Service Center 

(MSC) .............................................................................. 2-13

Figure 2-10 Overhead line damaged when flooding saturated soils and 

reduced strength of guy anchors...................................... 2-15

Figure 2-11 Emergency generator in an exterior enclosure in Cedar 

Rapid, Iowa, inundated during the 2010 Midwest 

floods ............................................................................... 2-17

Figure 2-12 Interior view of the flooded emergency generator shown

in Figure 2-10................................................................... 2-17

Figure 2-13 Sylmar high voltage direct current converter station 

damaged in the 1971 San Fernando Earthquake.............. 2-20

Figure 2-14 Example of a connection which accommodates relative 

displacements................................................................... 2-22

Figure 2-15 Well-anchored equipment................................................ 2-22

FEMA P-1019 List of Figures ix
Figure 2-16 Falling debris from security wall and parapet damaged 

cooling equipment for servers resulting in the data center 

going off line in the 2011 Haiti earthquake .....................2-23

Figure 2-17 Example of seismic isolation bearings and typical 

installation location..........................................................2-23

Figure 2-18 Typical flexible utility connections in base isolated 

building ............................................................................2-24

Figure 4-1 Life-safety equipment: fire alarm control panel (top) and 

exit signage (bottom). ......................................................4-12

Figure 4-2 Typical fire pump controller............................................4-13

Figure 4-3 A typical jockey pump.. ...................................................4-14

Figure 4-4 Roof-top mounted DX HVAC units ................................4-17

Figure 4-5 Water-cooled chiller (left) with cooling tower (right).....4-17

Figure 4-6 Air-cooled chiller.............................................................4-18

Figure 4-7 Sump cover.......................................................................4-19

Figure 4-8 Domestic water booster pumps........................................4-19

Figure 4-9 Domestic hot water circulator pumps ..............................4-20

Figure 4-10 Commercial kitchen for critical facility that provides 

food for occupants............................................................4-21

Figure 4-11 Large commercial refrigerator and freezer in commercial 

kitchen..............................................................................4-22

Figure 5-1 UPS system containing an inverter (left) and battery rack 

(right) located in a low seismic area ..................................5-3

Figure 5-2 Rendering of flywheel system............................................5-4

Figure 5-3 Emergency generator installed on the interior (left) and 

exterior (right)....................................................................5-5

Figure 5-4 Exterior emergency generator placed in a soundattenuating enclosure .........................................................5-6

Figure 5-5 Fuel oil storage tank used for heating equipment that can 

supply an emergency diesel generator ...............................5-8

Figure 5-6 Multiple generators in parallel...........................................5-9

Figure 5-7 Generator synchronizing board........................................5-10

x List of Figures FEMA P-1019
Figure 5-8 Building-mounted twist-lock plugs for connecting 

temporary generator cables.............................................. 5-14

Figure 5-9 Electrical connection point for temporary generator using 

slip-fit connectors (left), and cables at building connection 

(right)............................................................................... 5-14

Figure 6-1 Diesel-driven fire pumps ................................................... 6-6

Figure 6-2 Example of an elevated generator; photograph shows the 

intake louver in Galveston, Texas, 2010 ......................... 6-11

Figure 6-3 Switchgear, normal, and emergency power feeds, and 

associated equipment elevated to the same level as the 

emergency generator at UTMB, Galveston, Texas in 

2010 ................................................................................. 6-11

Figure 6-4 Interior generator protected from the effects of wind and 

wind-borne debris............................................................ 6-14

Figure 6-5 Emergency generator supported by seismically-rated 

vibration isolators............................................................ 6-18

Figure 7-1 Schematic diagram showing changes to a facility that 

allows critical loads to be supplied from an optional 

standby generator............................................................... 7-5

Figure 7-2 Schematic diagram showing transfer switch installed to 

supply an electrical service from either the utility or an 

optional standby power source .......................................... 7-7

Figure B-1 Schematic diagram for one style of redundant service 

illustrating circuit breaker responses if a utility source 

fails. ...................................................................................B-3

FEMA P-1019 List of Figures xi

List of Tables

Table 2-1 Saffir-Simpson Hurricane Wind Scale .............................. 2-8

Table 2-2 Description of Modified Mercalli Intensity Levels......... 2-19

Table 2-3 Summary of Problems Related to Emergency Generators 

in the 1994 Northridge Earthquake.................................. 2-25

Table 3-1 Risk Category of Buildings and Other Structures ............. 3-3

Table 4-1 Elements Potentially Requiring Emergency Power........... 4-7

Table A-1 Occupancy Classifications................................................ A-4

Table A-2 Critical Facilities by Occupancy....................................... A-4

Table A-3 Emergency Power Requirement by Occupancy ............... A-5

Table A-4 Items Requiring Emergency Power in Healthcare 

Facilities: Life Safety Branch........................................... A-8

Table A-5 Items Requiring Emergency Power in Healthcare 

Facilities: Critical Branch................................................. A-8

Table A-6 Items Requiring Emergency Power in Healthcare 

Facilities: Equipment Branch ........................................... A-9

Table A-7 Items Requiring Emergency Power in Healthcare 

Facilities: Equipment Branch ........................................... A-9

Table C-1 Motor Codes and Associated Lock Rotor Apparent 

Power.................................................................................C-2

Table D-1 Checklist for Planning Prior to Emergency 

or Disaster......................................................................... D-1

Table D-2 Checklist for Operation During Emergency or Disaster... D-3

Table D-3 Checklist for Recovery Following Emergency or 

Disaster............................................................................. D-4

FEMA P-1019 List of Tables xiii

Chapter 1

Introduction

There is a significant likelihood that utility power will not be available for an 

extended period of time during severe natural hazard events. Thus, it is 

necessary for critical facilities to have reliable sources of sustained electrical 

power to achieve continued operation. This document provides guidance on 

the design and operation of emergency power systems in critical facilities so 

that they will be able to remain operational for extended periods, as needed.

Most critical facilities rely on a public utility grid, where power is typically 

transmitted and distributed by way of networked systems over long distances 

between where the power is generated and where it is consumed. The longdistance transmission and distribution of electricity leaves emergency power 

supplies vulnerable to a variety of natural hazards, even for sophisticated 

redundant networks. Both aboveground and belowground power lines are 

susceptible to damage from winter storms, high-wind events, flooding, 

earthquakes and tsunamis. In addition, while not specifically addressed in 

this document, utility electrical power systems are also vulnerable to other 

types of hazards including terrorist physical attacks, cyber attacks, accidental 

man-made hazards and large sunspot events (space weather). Regardless of 

the cause, the resulting loss of power to critical facilities providing muchneeded services during such events can be particularly devastating to 

communities, unless a reliable and sustained source of emergency power is 

provided. The continued operation of critical facilities is a key element of 

community resiliency. 

For purposes of this document, critical facilities are buildings that contain the 

following functions: 

• Hospitals and emergency medical treatment,

• Fire, rescue, ambulance and police stations, and emergency vehicle 

garages,

• Buildings designated by the community as earthquake, hurricane, or 

other emergency shelters, and

• Emergency preparedness, communications systems, and operations 

centers and other facilities and sites required for emergency response

command and control.

The term critical facility 

defines a building that is

intended to remain 

operational in the event of 

extreme environmental 

loading from flood, wind, 

snow, earthquakes, or 

tsunamis. In model 

building codes, they are 

often referred to as 

essential buildings.

FEMA P-1019 1: Introduction 1-1
Disruption of health care, fire, and police services can impair search and 

rescue, emergency medical care, and even access to damaged areas. Critical 

facilities must be prepared for a loss of utility power, and their ability to 

function without interruption during and in the aftermath of hazard events 

deserves special attention.

The definition of critical facilities can be expanded to also include other 

types of facilities, including those that contain significant quantities of

hazardous materials and those buildings that serve functions that are critical 

to ongoing operations of business or government. Although not covered in 

the scope of this guidance document, the information provided can be 

applied to any of these facilities.

1.1 Purpose

Modern building codes and standards acknowledge the vulnerability of 

electrical power supplied by utilities, and therefore require that most 

buildings have at least some emergency power to supply select loads when 

normal electrical power is interrupted. The level of emergency power 

required by code does not allow critical facilities to operate indefinitely when 

power is lost. For many buildings subjected to most natural hazards, coderequired emergency power is limited and focused on supplying the minimum 

amount of power to allow occupants to safely leave a building. 

This document examines the vulnerability of electrical power systems to 

natural hazards, describes what equipment in critical facilities should be 

supplied by emergency power sources, how long the emergency power may 

be needed, the specific equipment needs of different types of critical 

facilities, and how emergency power can be supplied. It provides guidance 

on how to assess the risks and vulnerabilities to the electrical power system, 

identifying performance goals for an emergency power system, and the 

importance of having realistic emergency management policies that address 

emergency power. It also discusses the advantages and limitations of 

redundant systems, the need for advanced planning of emergency power 

systems, potential pitfalls when sizing system components, such as fuel 

storage tanks, and provides examples of simple and complex installations. It 

emphasizes the need to apply a holistic approach to the design of a new 

emergency power system. In this document, a holistic approach means all 

elements of the design and operation of the emergency power system and the 

equipment using the power need to be considered, so that the facility will 

perform as intended under extreme design events, all in a cost effective 

manner. The report also provides summaries of relevant building code 

provisions that influence the design of emergency power systems.

In this document, the terms 

emergency power, 

alternate power, and 

standby power systems are

used. These include:

• Systems required by 

building codes and 

standards to supply 

life-safety equipment, 

equipment that 

reduces hazards, and 

equipment that helps 

rescue or fire-fighting 

operations. 

• Systems not required 

by code, but are 

desirable for 

preventing serious 

interruptions, 

discomfort, or 

damage when power 

is lost. 

1-2 1: Introduction FEMA P-1019
The guidance provided in this document is limited to traditional emergency 

power systems. There other power systems, such as co-generation facilities 

and micro-grids, that also can supply emergency power. These are typically 

considered in very large facilities where design professionals with experience 

in these systems provide guidance to clients on the reliability of systems 

when subjected to natural and other hazards. 

1.2 Emergency Power from a Code Perspective

The term “emergency power” has specific meanings for code application in 

building codes and standards. NFPA 70, National Electrical Code, (NFPA, 

2014), which has been adopted into law throughout the United States, uses 

varying terminology. It is important to understand all of the distinctions in 

terminology because the authority having jurisdiction (AHJ) or code official 

will expect systems called “emergency systems” to meet all the code 

requirements for emergency systems as defined in the National Electrical 

Code. 

1.2.1 Emergency System

Section 700.2 of NFPA 70 defines an emergency system as follows: 

“Those systems legally required and classed as emergency by 

municipal, state, federal, or other codes, or by any governmental 

agency having jurisdiction. These systems are intended to 

automatically supply illumination, power, or both, to designated 

areas and equipment in the event of failure of the normal supply or 

in the event of accident to elements of a system intended to supply, 

distribute, and control power and illumination essential for safety to 

human life.” 

There are a number of requirements in NFPA 70 for emergency systems,

including the need for an automatic transfer switch that transfers the load 

within 10 seconds of loss of normal power and the need for separation from 

the normal power supply. Emergency systems require permanent power 

supplies. Emergency systems are typically required in places of assembly and 

other large buildings that may be occupied by a large number of people. 

1.2.2 Legally Required Standby System

Section 701.2 of NFPA 70 defines legally required standby systems as

follows:

“Those systems required and so classed as legally required standby 

by municipal, state, federal, or other codes or by any governmental 

FEMA P-1019 1: Introduction 1-3 
agency having jurisdiction. These systems are intended to 

automatically supply power to selected loads (other than those 

classed as emergency systems) in the event of failure of the normal 

source.” 

Legally required standby systems also require an automatic transfer switch. 

However, the load must be transferred within 60 seconds of loss of normal 

power. Legally required standby systems require permanent power supplies.

These systems typically serve loads such as heating and air conditioning 

systems. They may also supply sewage disposal systems, lighting, and some 

industrial machinery.

1.2.3 Optional Standby System

These systems are defined in Section 702.2 of NFPA 70 as follows:

“Those systems intended to supply power to public or private 

facilities or property where life safety does not depend on the 

performance of the system. These systems are intended to supply onsite generated power to selected loads either automatically or 

manually.” 

There are no requirements for a timed transfer of load for these systems, but 

a transfer switch is required. Optional systems do not require permanent 

power supplies; they may be supplied by portable or mobile equipment. 

1.2.4 Critical Operations Power System

Some facilities designated as critical facilities must operate continuously. An 

example is an emergency operations center of a police department. Many of 

these facilities are supplied through a critical operations power system 

(COPS). These systems are defined in Section 708.2 of NFPA 70 as follows:

“Power systems for facilities or parts of facilities that require 

continuous operation for the reasons of public safety, emergency 

management, national security, or business continuity.” 

1.3 Planning for Facility Resilience 

The concept of resilience, when applied to a critical facility, calls for 

consideration of how the facility will function during and after a disaster. 

What systems will need to remain operational for the facility to function? 

Basic building code requirements for emergency or standby power systems

in almost all buildings are intended to sustain a number of functions for short 

term needs, such as evacuating building occupants safely. Code-mandated 

emergency power systems are not required to operate key functions in a 

1-4 1: Introduction FEMA P-1019
facility. These systems are not designed to operate for long durations of 

power outage. Therefore, it is necessary to understand and provide 

additional emergency power for operational needs and the duration of these 

needs if a critical facility is to remain operational following a severe hazard 

event.

A key component in any consideration of emergency power systems is a 

disaster management plan, which establishes the desired level of function and 

performance of the building after a natural hazard event. The disaster 

management plan defines the role of the building in the post-disaster 

environment, and fits the purpose and role of the building in the overall 

framework of the post-disaster response mission. Once critical functions are 

identified, the building systems required to support the critical functions can 

be identified, along with their electrical power requirements. The plan 

should take into account the changes in normal operational procedures that 

will be implemented in the event of a disaster, which may serve to reduce the 

electrical power demands. The potential for outside assistance, in the form 

of portable emergency generating equipment, for example, should be 

considered along with any necessary building infrastructure that is needed to 

accept outside power sources. The disaster management plan should also 

consider the length of time before fuel and other supplies, such as lubricating 

oil and filter stocks, will need to be replenished. 

Careful disaster management planning will help ensure that the emergency 

power system is adequately sized to provide the required of level of electrical 

service, and that this power can be reliably maintained for the necessary 

period of time. Chapter 3 of this report provides guidance for consideration 

of emergency power needs in the disaster management plan. 

1.4 Target Audience

The objective of this report is to assist a wide range of people associated with 

the design, construction, management, operation and maintenance of critical 

facilities in understanding the needs for emergency power. The list of 

interested parties includes (but is not limited to):

• Facility owners

• Facility managers

• Facility emergency managers

• Facility operating engineers

• Architects

• Structural engineers

FEMA P-1019 1: Introduction 1-5
• Electrical engineers

• Mechanical engineers

• Fire protection engineers

• First responders – fire

• First responders – other than fire

• Public sector emergency managers

• Contractors

• Subcontractors

• Equipment manufacturers

• Equipment suppliers

• Maintenance contractors

Each of these different groups will likely focus in detail on different aspects 

of this publication, but all of parties will benefit from examining the entire 

document. This knowledge will aid them in implementing sound measures 

that will decrease the vulnerability of critical facilities to power disruptions 

caused by natural hazard events. The intent of the document is to identify 

potential vulnerabilities that may be faced by critical facilities when 

preparing the loss of utility power, as well as the best ways to provide 

emergency power. 

1.5 Report Organization 

This report is organized to guide the reader through concepts required to 

assess the vulnerabilities of the electrical power system of a facility. 

Chapter 2 provides an overview of the electrical transmission system and the 

vulnerability of utility provided power and building systems to natural 

hazards. 

Chapter 3 provides guidance on disaster risk management planning for 

critical facilities including defining critical facility, deciding where the 

facility fits into the overall framework of local and regional emergency 

response.

Chapter 4 provides guidance on specific critical facility needs for emergency 

power, including determining what functions are deemed critical and which

equipment and systems that support those functions are needed, and the 

length of time emergency power is required. 

1-6 1: Introduction FEMA P-1019
Chapter 5 provides an overview of the elements of common emergency 

power generation systems.

Chapter 6 provides design considerations and best practices for emergency 

power systems in new critical facilities, including how to decide on what 

functions in a critical facility require emergency power, design decisions that 

affect the demand load for emergency power systems, and strategic decisions 

on the layout and locations of emergency power systems. 

Chapter 7 provides guidance for providing more reliable emergency power 

systems in existing critical facilities that will function as needed following 

severe natural hazard events. 

Appendix A provides an overview of current code requirements for 

emergency power systems. 

Appendix B provides an overview of utility power systems and redundancy

strategies.

Appendix C provides guidance on the design and selection of generators 

including load requirements, peak and continuous loads, along with how 

power quality basics, such as voltage and phase stability, frequency dip, 

harmonics, and transients, impact system reliability.

Appendix D provides checklists for emergency power systems to be used as 

helpful aids before, during, and after disaster events.

Appendix E presents examples on how to utilize this document for some 

typical situations.

A list of the references used in this document is included at the end of the 

report.

1.6 How to Use this Document

This document is intended as an introduction to the fundamental principles of 

providing emergency power for critical facilities. It is not intended to be a 

comprehensive design manual for developing actual plans and specifications. 

The information presented is intended to help readers understand broad risk 

reduction approaches and how to integrate them into facility planning and 

design. An example flowchart that one might use in a decision making 

process to evaluate emergency power generation needs using this document 

is provided in Figure 1-1. 

While emergency power systems are highly engineered systems, without 

well-defined requirements for extreme natural hazard events to guide their 

FEMA P-1019 1: Introduction 1-7
Do you have e-power 

needs beyond 90 minute 

egress/exit lighting?

Yes

Do you require 

e-power within hours of 

power loss?

Yes

No

Do you require 

immediate e-power with 

no power interruption? 

Develop equipment 

list for e-power 

system sizing – see 

Appendix C

No

Does system 

reliability need enhanced 

redundancy?

Yes

No

Investigate temporary 

generator options 

– see Section 5.3

Utilize battery 

pack lighting 

options

Healthcare application 

subject to NFPA 99

– see Section 5.2

Yes

Investigate stored 

energy devices 

– see Section 5.1.1

No

Single generator 

strategy

EMERGENCY POWER FLOWCHART

Utilize N+1 

redundancy 

strategies 

– see Appendix B

Locate and design generators and associated systems to 

resist natural hazards

Figure 1-1 Flowchart illustrating example logic for determining emergency 

power needs and generator selection. 

1-8 1: Introduction FEMA P-1019
design, installation and operation, it is quite possible they may not operate as 

needed when such events occur. Note that the building codes, consensus 

standards, and design guides referenced in this document are the current 

editions of these nationally recognized publications. These publications are 

updated on regular publication cycles, which may occur after the publication 

date of this document. Thus, there may be newer editions than those noted in 

this document. Also, not all local authorities having jurisdiction over critical 

facilities adopt the latest standards. It is essential for detailed design of 

specific facilities that the currently applicable requirements be determined in 

consultation with the authorities having jurisdiction over the specific project.

FEMA P-1019 1: Introduction 1-9

Chapter 2 

Natural Hazard Effects on 

Utilities and Building Systems 

In this section, utility power transmission and distribution systems are 

described along with their observed vulnerabilities to natural hazards. The 

vulnerabilities of emergency power systems to natural hazards are also 

discussed. 

Natural hazards addressed in this section include winter storms (freezing 

rain, snow and ice), high-wind events (hurricanes, tornadoes, and 

nor’easters), flooding (riverine and coastal), and earthquakes. Each of these 

hazards presents a unique set of design challenges for electrical transmission 

and distribution power systems. 

2.1 Overview of Utility Power Transmission and

Distribution Systems

Electrical power supplied by utilities is carried from the point of generation to

the end user over two basic systems referred to as transmission and

distribution (Figure 2-1). The transmission system is the backbone of the

utility grid and carries power at the wholesale level. Utility power plants

connect directly to this backbone to transport power to local distribution

systems, and then on to the user. Transmission lines, which operate at very 

high voltages that range between 69,000 and 765,000 volts (69 to 765 kV), 

carry electricity to distribution sub-stations where it is dispersed to 

commercial, industrial, and residential customers. At boundaries of utility 

coverage areas the transmission lines connect to transmission systems of 

adjoining utilities. 

When it is necessary to transport large blocks of electrical power over long

distances, a highly specialized high voltage direct current (HVDC)

transmission system is used. For example, HVDC transmission systems are 

used to transport bulk power from a large but remote power station, such as a 

hydro-electric plant at a dam, to a city. 

2.1.1 Failures of Transmission Systems

Just like the inertia of a very large ocean going vessel moving at top speed,

the collective inertial energy of the generators and turbines at each power

FEMA P-1019 2: Natural Hazard Effects on Utilities and 2-1 

Building Systems
Figure 2-1 Illustration of a simplified utility transmission and distribution system. UG indicates 

underground; 3ø indicates three-phase (typical for industrial customers); 1ø indicates onephase (typical for residential customers). 

plant on the utility grid stabilizes the transmission system, due to the

enormous net inertial energy of all the connected sources. As a result, the 

transmission system is able to absorb minor disturbances from either 

individual power plants or retail distribution load points within the utilities 

system with almost no impact to the overall system. Utilities also design 

levels of redundancy into their systems to allow for loss of major elements in 

their system due to failures or essential maintenance. Sub-station equipment

at the transmission level typically costs millions of dollars and is available 

from a very small number of suppliers globally, and has long acquisition 

times. Therefore, utilities design their transmission systems for maximum 

reliability.

Failures of the transmission systems are unlikely, but have occurred. Rare 

natural hazard events that spread damage over a wide geographical area have 

caused failures to transmission systems. When a sufficient amount of 

damage accumulates, the overall transmission system goes down, taking with 

it neighboring utilities in a cascading sequence of failures. Automatic 

protective systems may trip generating stations offline and isolate ties to 

neighboring utilities as network operators race to protect their systems. 

2-2 2: Natural Hazard Effects on Utilities and FEMA P-1019

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Recovering from such a massive outage takes days as power plants restart, 

reconnect the major system elements, and pick up loads from the local 

distribution systems.

When natural hazard damage to transmission systems occur over a multistate 

area, weeks may pass before power is completely restored. In some cases,

the restoration of service may involve a substantial rebuilding of the utilities 

distribution systems over large areas. Since HVDC systems lack the 

redundancy of major utility transmission systems and usually span large 

distances, they are more vulnerable to extended outages due to natural 

disasters. Owners and facility managers of critical facilities that are 

dependent on HVDC transmission systems for power should carefully 

determine if these systems are sufficiently reliable during severe natural 

hazard effects or if alternate sources of onsite power are needed.

2.2 Winter Storms

Winter storms can bring freezing rain, sleet, snow, or a combination of the 

three. Snow and ice accumulation during winter storms places greater loads 

on structures, power lines, and trees. Winter storms can include any one or 

more of the following hazardous weather events:

• Heavy Snowstorm: Generally considered to include events with 

accumulations of 4 inches of snow or more in a 6-hour period, or 6 

inches or more in a 12-hour period.

• Sleet Storm: Significant accumulations of solid pellets, which form from 

the freezing of raindrops or partially melted snowflakes, causing slippery 

surfaces that create hazards to pedestrians and motorists.

• Ice Storm: Significant accumulations of rain or drizzle freezing on 

objects, such as trees, power lines, and roadways, as it strikes them, 

causing slippery surfaces and damage from the weight of ice 

accumulation (Figure 2-2) and increased area exposed to wind loads.

• Blizzard: Wind velocity of 35 miles per hour (mph) or more, 

temperatures below freezing, and considerable blowing snow with 

visibility frequently below 1/4 mile prevailing over an extended period of 

time.

• Severe Blizzard: Wind velocity of 45 mph or higher, temperatures of 10 

degrees Fahrenheit or lower, and a high density of blowing snow, with 

visibility frequently measured in feet, prevailing over an extended period 

time.

FEMA P-1019 2: Natural Hazard Effects on Utilities and 2-3

Building Systems
Figure 2-2 Damage to overhead distribution line caused by weight of ice 

accumulation (Nyether, 2014). 

2.2.1 Effects of Winter Storms on Power Lines

Overhead Power Lines: Overhead power lines are directly affected by winter 

storms when snow or ice accumulate on them and the lines fail under the 

weight and when ice accretion (as shown in Figure 2-2), coupled with high 

winds, stress the conductors and their supports to their breaking point. The 

following modes of failure have been observed:

• Conductors, guys, and guy connectors fail when applied loads exceed 

their tensile strengths; 

• Wooden structures supporting the lines typically fail when applied 

moments exceed their bending strengths; and

• Guy anchors (typically called foundation helical anchors) fail when loads 

exceed the amount of forces that the soils can resist and the guy anchors 

are pulled through the soils. Figure 2-3 depicts typical failure modes. 

Overhead power lines can also be damaged when trees or tree limbs fail 

under the weight of snow or ice and take down sections of overhead lines 

when they fall. Generally, overhead power lines are designed only for wind 

and ice loading, not for the loads caused by fallen trees or limbs. 

Repairs to damaged lines in adverse weather conditions are difficult, 

particularly when damage is widespread, utility crews have numerous repairs 

to complete, and when damage is in areas that are difficult to access. After a 

2-4 2: Natural Hazard Effects on Utilities and FEMA P-1019

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severe event, customers may be without power for some time. With severe 

storms, outages that last two weeks or more are not uncommon. 

Figure 2-3 Typical failure modes of overhead power lines.

Underground Power Lines: Given the nature of winter storms, a power 

distribution system comprised primarily of underground power lines is 

usually not directly affected by winter storms. However, most underground 

lines are fed from overhead lines at some point, and because the overhead 

lines remain vulnerable to winter storms, underground systems typically 

experience some outages. Figure 2-4 shows a riser pole that supplies 

underground electrical distribution from an overhead line.

Figure 2-4 Riser pole of an underground electrical line supplied from an 

overhead line.

FEMA P-1019 2: Natural Hazard Effects on Utilities and 2-5

Building Systems
2.2.2 Effects of Winter Storms on Building Systems

Some mechanical, electrical, and plumbing (MEP) components, such as 

chillers, cooling towers, roof-mounted HVAC units, and pad-mounted 

transformers, are often placed outside of a building and exposed to the 

elements. Those components can be damaged by wind and ice loads or by 

falling ice or sliding snow. Wet piping systems can freeze during extremely

cold periods, particularly those installed in temperate climates when exterior 

temperatures drop below design temperatures. Snow falling from roof levels

can damage equipment. In addition, if communication towers, utility poles, 

or light standards are located within lay-down range and fail when exposed

to ice and wind loading, they can damage equipment. 

Some components of MEP systems are placed within buildings that have 

structures and envelopes designed to resist code specified loads, offering

protection from winter storms. However, even when placed within a 

building, winter storms and winter temperatures can adversely affect the 

operation of building systems. For example, maintaining indoor air quality 

requires introducing fresh outside air into a building. When exterior 

temperatures are extremely low, the cold outside air can freeze HVAC 

equipment like pre-heat coils when the cold outside air is brought into the 

building. Modern HVAC equipment employs thermostatic freeze protection 

for air intakes. However, the functionality of even protected units can be 

interrupted when exterior temperature drops below design temperatures and 

force HVAC equipment to function beyond its design parameters. 

Another possible failure stems from the need for outside air for combustion 

and ventilation of emergency generators. Section 6.4 of NFPA 99, Health 

Care Facilities Code (NFPA, 2012a), requires fresh air intake louvers to be 

placed in generator rooms to provide unrestricted airflow to the generator. 

These louvers are required to fail in the open position to ensure that airflow 

is not restricted. However, louvers open to extremely low exterior

temperatures can rapidly introduce large volumes of cold air into the building

that can cause piping systems, domestic water systems, and fire suppression 

systems to freeze and fail. 

Also, other systems, such as battery systems for starting emergency 

generators and controlling medium voltage electrical switchgear, are also 

susceptible to failing at extremely cold conditions. 

2.2.3 Case Study – Winter Storms of 2007

In January 2007, a severe ice storm hit several states from Texas to New 

England, as well as some areas of southeastern Canada. The storm arrived in 

Lay-down hazards to refer 

to hazards caused by 

toppling trees and 

structures, such as 

communication towers, 

antennas, and lighting 

poles. 

2-6 2: Natural Hazard Effects on Utilities and FEMA P-1019

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three waves (Tulsa Tornado Tribune, 2007): The first wave hit Oklahoma on 

January 11 and was followed by a second wave in the southern United States 

that extended from Texas to the Carolinas from January 16 through January 

18. A third wave from January 19 through January 24 hit the southern plains 

and Mid-Atlantic regions of the United States, as well as the Canadian 

provinces of Newfoundland and Labrador. This long-lasting and widespread 

event resulted in widespread power outages. The impacts in several areas are 

described below.

• Oklahoma: More than 100,000 customers without power, 63,000 of 

which were without power for more than one week (CNN, 2007). 

Overall damage in the State totaled approximately $40 million.

• Missouri and Illinois: 330,000 customers in Missouri were without 

power at the peak of the storm, including 70,000 in Springfield, 

Missouri, alone. In east Missouri and central Illinois, over 110,000 

customers were without power. Overall damage in Missouri totaled 

approximately $353 million (Spellman, 2007).

• Texas: Approximately 60,000 customers were without power across the 

State between January 12 and 18 (USA Today, 2007).

2.3 High Winds

High winds occur in several types of storms, including hurricanes and 

tropical storms, tornadoes, and nor’easters. Each storm produces a unique 

set of weather conditions, but all have the potential for winds that exceed 

design wind speeds, particularly for overhead lines less than 60 feet tall 

designed to resist minimum loading requirements according to National 

Electrical Safety Code (IEEE, 2012). 

• Hurricane: A system of spiraling winds converging with increasing 

speed toward the storm’s center (the “eye” of the hurricane). These 

storms originate over warm ocean waters and can vary in diameter from 

50 to 600 miles. A hurricane’s forward movement (translational speed) 

can vary from approximately 5 mph to more than 25 mph. In addition to 

delivering extremely strong winds for several hours and moderately 

strong winds for a day or more, many hurricanes also bring very heavy 

rainfall and may occasionally spawn tornadoes. The Saffir-Simpson 

Hurricane Wind Scale is used to categorize hurricanes based on wind 

speed (See Table 2-1). Of all the storm types, hurricanes have the 

greatest potential to devastate a large geographical area and, hence, affect 

the largest sections of electrical lines and the greatest number of people.

FEMA P-1019 2: Natural Hazard Effects on Utilities and 2-7

Building Systems
Table 2-1 Saffir-Simpson Hurricane Wind Scale (NOAA, 2014a)

Category Sustained Winds Types of Damage Due to Hurricane Winds

1 

74-95 mph

64-82 kt

119-153 km/h

Very dangerous winds will produce some damage: Well-constructed frame 

homes could have damage to roof, shingles, vinyl siding and gutters. Large 

branches of trees will snap and shallowly rooted trees may be toppled. Extensive 

damage to power lines and poles likely will result in power outages that could last 

a few to several days.

2 

96-110 mph

83-95 kt

154-177 km/h

Extremely dangerous winds will cause extensive damage: Well-constructed frame 

homes could sustain major roof and siding damage. Many shallowly rooted trees 

will be snapped or uprooted and block numerous roads. Near-total power loss is 

expected with outages that could last from several days to weeks.

3 

(major)

111-129 mph

96-112 kt

178-208 km/h

Devastating damage will occur: Well-built framed homes may incur major 

damage or removal of roof decking and gable ends. Many trees will be snapped 

or uprooted, blocking numerous roads. Electricity and water will be unavailable 

for several days to weeks after the storm passes.

4 

(major)

130-156 mph

113-136 kt

209-251 km/h

Catastrophic damage will occur: Well-built framed homes can sustain severe 

damage with loss of most of the roof structure and/or some exterior walls. Most 

trees will be snapped or uprooted and power poles downed. Fallen trees and 

power poles will isolate residential areas. Power outages will last weeks to 

possibly months. Most of the area will be uninhabitable for weeks or months.

5 

(major)

157 mph or higher

137 kt or higher

252 km/h or higher

Catastrophic damage will occur: A high percentage of framed homes will be 

destroyed, with total roof failure and wall collapse. Fallen trees and power poles 

will isolate residential areas. Power outages will last for weeks to possibly months. 

Most of the area will be uninhabitable for weeks or months.

• Tornado: A rapidly rotating funnel of air extending toward the ground 

from a cumulonimbus cloud. Other hazards that accompany tornadoes 

include rainstorms, windstorms, large hail, and lightning. Tornadoes can 

occur at any time during the day or night, but are most frequent during 

late afternoon into early evening, the warmest hours of the day. The 

width of a tornado varies greatly, ranging from less than 100 feet to a 

mile. Some tornadoes never touch the ground and are short-lived, while 

others may touch the ground several times and cross several states. 

Nationwide, approximately 1,000 tornadoes are produced annually by 

severe thunderstorms. The intensity of a tornado is determined by the 

damage it causes according to the Enhanced Fujita (EF) scale (See 

Figure 2-5). 

• Northeaster (or nor’easter): A cyclonic storm occurring off the east 

coast of North America. These winter weather events produce heavy 

snow and rain, high waves, and strong winds. A nor’easter gets its name 

from its general path along the Atlantic Coast toward the northeast and 

from the continuously strong northeasterly winds it creates ahead of the 

storm. Nor’easters can last for several days.

Enhanced Fujita Scale

The Enhanced Fujita Scale 

classifies tornado damage 

using ratings of EF0–EF5. 

The EF Scale is calibrated 

by engineers and 

meteorologist and is based 

on 28 different types of 

buildings and structures 

(called “damage 

indicators”) that are 

observed for different 

types of damage after a 

tornado event (roof 

removed, broken 

windows). The resulting EF 

ranking is based on 

detailed observations of 

tornado damage. 

2-8 2: Natural Hazard Effects on Utilities and FEMA P-1019

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Figure 2-5 Illustrated Enhanced Fujita scale (NOAA, 2014b). 

2.3.1 Effects of High Winds on Power Lines

Overhead Power Lines: Overhead power lines are particularly vulnerable to 

high-wind events, and the damage can be acute and widespread because of 

the fragility of overhead components. Specifically, lines can be damaged by 

wind loading, fallen tree limbs and trees or other lay-down hazards, and 

failure of supporting power structures (e.g., poles, towers). Sub-station

equipment can be damaged from wind loads, debris impact, and lay-down 

hazards. Figure 2-6 shows transmission lines that were damaged by 

tornadoes that struck Tuscaloosa, Alabama, in April 2011. 

Underground Power Lines: A power distribution system comprising 

primarily underground power lines is not directly affected by high winds. 

However, because underground lines are fed from overhead lines at some 

point, and overhead sections are vulnerable to wind damage, underground 

systems often experience outages caused by high winds. 

2.3.2 Effects of High Winds on Building Systems 

Similar to the protection offered from winter storms, a properly designed 

building can also protect interior systems from high winds, particularly when 

the wind speeds do not exceed those that the building was designed to resist. 

FEMA P-1019 2: Natural Hazard Effects on Utilities and 2-9 

Building Systems
Figure 2-6 Tornado damage to transmission lines, Tuscaloosa, Alabama, 

April 2011 (FEMA, 2012a). 

Wind speeds that exceed design levels can penetrate the building envelope, 

damaging the critical interior system components, and may also weaken 

structural elements.

In properly designed and constructed buildings, envelope failures are more 

common than structural failures. Failures can result when wind loads exceed 

the ability of the envelope to resist those loads. Wall sheathing, roof 

sheathing, and the roof membrane can be torn, particularly near the edges 

and corners of a building where wind pressures are at their highest. Building 

envelope failures can also result from wind-borne debris. Wind-borne debris 

can be particularly damaging to glazing but can also damage non-glazed 

portions of the envelope. Damage can also result from water intrusion from 

wind-driven rain. Exterior equipment can also be damaged from lay-down 

hazards. FEMA 543 report, Design Guide for Improving Critical Facility 

Safety from Flooding and High Winds: Providing Protection to People and 

Buildings (FEMA, 2007a), provides additional information on the effects of 

winds on buildings. 

2.3.3 Case Study – 2011 Tornadoes in the Southeastern United 

States 

From April 25 to 28, 2011, widespread and destructive tornadoes in the 

southeastern United States left many homeless, and many more without 

power or water service. This tornado outbreak produced approximately four 

tornadoes rated EF5 (FEMA, 2012a). For comparison, typically only one 

EF5-rated tornado occurs per year. 

Building envelope refers 

to the exterior walls and 

roof of a structure.

2-10 2: Natural Hazard Effects on Utilities and FEMA P-1019

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The tornados destroyed 300 transmission towers in northern Alabama. As a 

result, all incoming transmission 161 kV and 500 kV lines were lost and 

power was not fully restored for two weeks. A nuclear power plant in the 

area lost all offsite power briefly and was only able to regain one incoming 

circuit, forcing the plant to operate its onsite backup diesel generators for 

four days.

Nearly 260,000 customers lost service in the Tuscaloosa, Alabama, area as a 

result of the tornadoes (Robertson and Severson, 2011). Emergency 

operations centers (EOCs) in three of the counties and one 9-1-1 dispatch 

system in one county affected by this storm were without power. EOCs and 

9-1-1 dispatch systems are in the greatest demand immediately following an 

event. When power is lost and no emergency power systems are in place, 

those systems and facilities can offer only limited functionality. 

Figures 2-7 and 2-8 show the remains of a building housing the switchgear 

and emergency generator for a critical facility in Joplin, Missouri, that was 

struck by tornado winds during the outbreak and collapsed. The building 

utilized steel deck/steel roof structures and unreinforced masonry block 

walls, which were designed for normal (non-tornadic) design winds speeds.

Figure 2-7 Collapsed building housing switchgear and emergency 

generator after the Joplin, Missouri Tornado (FEMA, 2012a).

In addition to the customers in Alabama affected by the storms, the 

Tennessee Valley Authority lost more than 200 towers and other structures in 

the events, leaving nearly 700,000 customers across several states without 

power. For approximately 150,000 of these customers, power was restored 

FEMA P-1019 2: Natural Hazard Effects on Utilities and 2-11

Building Systems
shortly after the storm. For the remaining, power was not restored for more 

than one week.

Figure 2-8 Steel deck/steel joist URM building housing the emergency 

generator and switchgear destroyed in the Joplin, Missouri 

Tornado (FEMA, 2012a).

2.3.4 Case Study – Derecho Winds – June 2012

The June 2012 “Derecho” winds damaged subtransmission and distribution 

systems over an 800-mile long path from Indiana to Virginia and Maryland 

with winds up to 100 mph. Damage was so extensive that it took up to ten 

days to restore power over this wide multi-state area.

2.3.5 Case Study – 2012 Superstorm Sandy in Long Island

Superstorm Sandy made landfall on October 29, 2012 near Brigantine, New 

Jersey. Sandy had been originally classified as a hurricane but the 

classification was revised to a post-tropical cyclone at landfall. Sandy 

impacted a 1,000 mile section of the United States with maximum sustained 

wind speeds estimated at 80 mph (FEMA, 2013a). 

Damages from Sandy interrupted power to over 90% (1.1 million customers) 

of Long Island Power Authority’s customer base. In some areas power 

outages lasted 14 days. While damage occurred to some transmission lines, 

distribution line damages, particularly damages to the main three-phase 

feeder lines, accounted for most of the customer service interruptions.

2-12 2: Natural Hazard Effects on Utilities and FEMA P-1019

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2.4 Flooding

Flooding is the most common natural hazard in the United States, affecting 

more than 20,000 local jurisdictions and representing more than 70 percent 

of Presidential disaster declarations. Several evaluations have estimated that 

7 to 10 percent of the Nation’s land area is subject to flooding. Some 

communities have very little flood risk, while others lie entirely within areas 

designated by FEMA as Special Flood Hazard Areas (SFHAs) on National 

Flood Insurance Program (NFIP) Flood Insurance Rate Maps (FIRMs)

(Figure 2-9). The SFHA designate the land area covered by the floodwaters 

of the base flood. The SFHA is the area where the NFIP’s floodplain 

management regulations must be enforced and where the mandatory 

purchase of flood insurance applies.

Figure 2-9 Example for map from FEMA Flood Map Service Center (MSC), the official 

public source for flood hazard information produced in support of the National

Flood Insurance Program (NFIP). Available at https://msc.fema.gov/portal for 

panel number 3604970377F. 

Flooding events are generally subcategorized as either riverine or coastal. 

Riverine flooding results when the volume of rainfall or runoff exceeds the 

capacity of waterway channels and spreads out over the adjacent land. 

Flooding depth, duration, and velocity are functions of many factors, 

including watershed size and slope, degree of upstream development, soil 

FEMA P-1019 2: Natural Hazard Effects on Utilities and 2-13

Building Systems
types and nature of vegetation, topography, and characteristics of storms (or 

depth of snowpack and rate of melting).

Coastal flooding occurs along the Atlantic, Gulf, and Pacific coasts, and 

along the shores of the Great Lakes. Coastal flooding is influenced by storm 

surges associated with tropical cyclonic weather systems (hurricanes, tropical 

storms, tropical depressions, typhoons), extratropical systems (nor’easters 

and other large low-pressure systems), and tsunamis (surges induced by 

seismic activity). Coastal flooding is characterized by wind-driven waves. 

The intensity of both riverine and coastal flooding events is measured by the 

depth and velocity of flood waters, the duration for which the waters remain 

above normal levels, and whether any debris damage, wave action, and 

erosion or scour occurred. 

Another type of flooding that must be considered is flash flooding, which can 

occur in both coastal and inland areas. Flash flooding results when there is 

an extremely intense rainfall for a relatively short period of time that causes 

rapid rises in water levels and flooding.

2.4.1 Effects of Flooding on Power Lines

Overhead Power Lines: Overhead lines are generally not at a significant risk 

for flood damage. Energized power lines are elevated to prevent people from 

accidentally coming into contact with them, and the elevation protects much 

of an overhead electrical system from flood inundation damage. However, 

some portions of an overhead electrical system, most notably sub-stations, 

are not elevated. Such portions of an overhead system may be vulnerable to 

inundation, particularly when located in low-lying areas or in SFHAs. 

Further, structures that support overhead lines can be damaged by moving 

floodwaters from scour, erosion, and hydrodynamic loads. They can also be 

damaged if they are struck by flood-borne debris. These risks are more 

common when overhead lines are routed along waterways or floodways. 

Flooding can also damage overhead lines by saturating soils, which reduces 

the soil strength. When soils are saturated, structures like poles and ground 

anchors, which rely on soil strength to resist loads imposed on the overhead 

lines, can fail (Figure 2-10). 

Even when not directly damaged by flooding, overhead electrical systems 

can be affected when floodwaters impede normal maintenance and operation 

activities. This is particularly true when electrical lines are routed through 

areas where long-duration floodwaters are slow to recede. If floodwaters are 

particularly deep (approximately 2 feet or so), equipment needed to repair 

2-14 2: Natural Hazard Effects on Utilities and FEMA P-1019

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overhead electrical lines may not be able to access damaged sections. In 

those instances, outages may persist until all floodwaters recede and the lines 

can be accessed and repaired.

Figure 2-10 Overhead line damaged when flooding saturated soils and 

reduced strength of guy anchors (Deleon, 2014). 

Hydrodynamic loads from moving floodwaters may have 

contributed to failure.

Underground Power Lines: Underground portions of power lines are 

generally resistant to damage from freshwater flooding. Most underground 

equipment can resist immersion in freshwater, particularly for short 

durations. Immersion in saltwater is more problematic because of the 

electrical conductivity of saltwater.

However, aboveground components of underground power line systems, 

such as pad-mounted transformers, medium-voltage sectionalizing switches, 

and pad-mounted switchgear, are vulnerable to floods. Like the supporting 

structures for overhead lines, pad-mounted equipment can be damaged by 

hydrostatic forces, hydrodynamic forces, flood-borne debris impact, scour, 

and erosion. Submersion can also short-circuit energized pad-mounted 

equipment, particularly the older style live-front equipment.

FEMA P-1019 2: Natural Hazard Effects on Utilities and 2-15

Building Systems
2.4.2 Effects of Flooding on Building Systems 

For many facilities, flood is the natural hazard that poses the greatest risk of 

damage to building systems that can prevent a facility from functioning. 

This is because major components of buildings systems, such as boilers, 

electrical service and distribution equipment, fuel tanks and fuel pumps, 

other pumps, and IT servers, are often located in the lowest level of a 

building, which is the level most vulnerable to flooding. 

The risk of flood damage is particularly high for buildings that were 

constructed before flood risks were quantified. Some buildings constructed 

after flood risks were quantified but before 2006 when the International 

Building Code (IBC) first referenced ASCE 24-05, Flood Resistant Design 

and Construction (ASCE, 2005), are also at risk. ASCE 24-05 requires that 

building systems (referred to as “utilities” in that standard) either be elevated

above design flood elevations or dry floodproofed. 

Flooding can have disastrous effects on emergency power systems. 

Floodwater can damage or inundate fuel tanks that supply diesel generators, 

fuel oil pumping equipment, and emergency power distribution equipment, 

such as transfer switches, panels, and feeders. Many post-flood event 

investigations have shown that components of the emergency power and 

distribution system are often placed at lower elevations than components of 

the normal power distribution system and therefore are more vulnerable to 

flooding.

2.4.3 Case Studies

During Hurricane Katrina in 2005, generators serving one hospital were 

elevated but automatic transfer switches that transfer critical loads from 

normal (utility) power to emergency power when utility power is lost, were 

not elevated. The floodwaters rendered the transfer switches inoperable. 

Thus, even though the generators themselves could still function, they could 

not provide power to critical equipment.

During Hurricane Ike in 2008, many buildings on a large hospital campus 

flooded and could no longer provide critical services. In one building, 

however, the emergency generators and all their associated equipment were

located on the second floor. While the storm surge flooded the first floor, the 

floodwaters did not reach the critical equipment so it remained operable 

during and after the flood. 

During the floods in the mid-western United States in 2008, emergency 

generators for several law enforcement facilities were destroyed by flooding. 

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Figures 2-11 and 2-12 show one of those facilities, where the floodwaters 

fully inundated the generator and submerged two thirds of the diesel engine 

prime mover.

Figure 2-11 Emergency generator in an exterior enclosure in Cedar Rapid, 

Iowa, inundated during the 2010 Midwest floods.

Figure 2-12 Interior view of the flooded emergency generator shown in 

Figure 2-11. The blue dashed horizontal line denotes the high 

watermark.

During Superstorm Sandy in 2012, a large hospital lost emergency power 

because the fuel pumps were immersed. Without emergency power, they 

were unable to operate the pumps used to fill storage tanks with potable 

FEMA P-1019 2: Natural Hazard Effects on Utilities and 2-17

Building Systems
water. When the storage tanks drained, the hospital lost potable water and 

the patients and staff had to be evacuated. 

2.5 Earthquakes

Earthquake ground motions are the result of sudden movements or fractures 

within the earth’s crust. The earthquake generates waves that travel through 

the rocks and soil outward from the epicenter of the earthquake, the source of 

the shaking. Most earthquakes occur on known faults, weakened planes in 

the earth’s crust that have generated earthquakes in the past, although not all 

earthquakes are associated with faulting. The propagation of waves through 

the earth’s crust produces shaking of the earth’s surface that can result in 

motions ranging from barely perceptible to violent shaking. The shaking 

effect or seismic ground motion diminishes with distance from the epicenter. 

The intensity of the ground motion at a given site is a function of the 

magnitude of the earthquake, the distance of from the earthquake source and 

site soil conditions. The magnitude of earthquake (most commonly referred 

to as the Richter Magnitude although other magnitudes are often used)

provides an indication of the energy released. If the intensity of shaking is 

high, most structures will sustain some damage and some may collapse. The 

most commonly used shaking intensity scale is the Modified Mercalli

Earthquake Intensity scale, which rates the level of ground motion at a site 

based on perceptions and observed damage (See Table 2-2).

The criteria used to evaluate the effects of ground motion on the built 

environment include displacement demands, i.e., deformations of the ground 

and structures, and acceleration demands, i.e., inertial forces generated by the 

shaking motion. For building code purposes, nonstructural components are 

considered tolerant of these damaging demands when they have a seismic 

capacity greater than the seismic demand.

In addition to the ground shaking, earthquakes can cause geological hazards, 

including surface fault ruptures, soil liquefaction, landslides, tsunamis, and 

seiches. Soil liquefaction occurs when ground shaking temporarily changes 

saturated loose granular soils and sands from a solid to a liquid. Liquefaction

occurs mainly at sites with high water tables near rivers, lakes, and bays. 

Earthquake shaking can trigger landslides on slopes that otherwise appear 

stable, and generate large waves in both oceans (tsunamis) and lakes 

(seiches). Both the ground shaking and subsequent geological hazards have 

the potential to disrupt or destroy power distribution lines and building 

systems.

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Table 2-2 Description of Modified Mercalli Intensity Levels (USGS, 2014)

Level Description

I Not felt except by a very few under especially favorable conditions.

II Felt only by a few persons at rest, especially on upper floors of buildings.

III Felt quite noticeably by persons indoors, especially on upper floors of buildings. Many people do not 

recognize it as an earthquake. Standing motor cars may rock slightly. Vibrations similar to the passing of 

a truck. Duration estimated.

IV Felt indoors by many, outdoors by few during the day. At night, some awakened. Dishes, windows, 

doors disturbed; walls make cracking sound. Sensation like heavy truck striking building. Standing 

motor cars rocked noticeably.

V Felt by nearly everyone; many awakened. Some dishes, windows broken. Unstable objects overturned. 

Pendulum clocks may stop.

VI Felt by all, many frightened. Some heavy furniture moved; a few instances of fallen plaster. Damage 

slight.

VII Damage negligible in buildings of good design and construction; slight to moderate in well-built 

ordinary structures; considerable damage in poorly built or badly designed structures; some chimneys 

broken.

VIII Damage slight in specially designed structures; considerable damage in ordinary substantial buildings 

with partial collapse. Damage great in poorly built structures. Fall of chimneys, factory stacks, columns, 

monuments, walls. Heavy furniture overturned.

IX Damage considerable in specially designed structures; well-designed frame structures thrown out of 

plumb. Damage great in substantial buildings, with partial collapse. Buildings shifted off foundations.

X Some well-built wooden structures destroyed; most masonry and frame structures destroyed with 

foundations. Rails bent.

XI Few, if any (masonry) structures remain standing. Bridges destroyed. Rails bent greatly.

XII Damage total. Lines of sight and level are distorted. Objects thrown into the air.

2.5.1 Effects of Earthquakes on Power Lines and Sub-stations 

Overhead Power Lines: Many structures supporting overhead transmission 

lines, such as poles and towers, are cantilevered (fixed to the soil at the base 

and free to translate at the top). If seismic loads are not considered during 

design, overhead power lines can be damaged or destroyed during an 

earthquake, particularly when they are near the epicenter and subjected to 

intense shaking. Even if designed to withstand seismic motion, overhead 

electrical lines may suffer outages when energized conductors experience 

excessive movement and come into contact with grounded surfaces or other 

energized conductors. Ground faults and phase-to-phase faults can cause 

protective devices, such as circuit breakers, fuses, or reclosers, to trigger and 

de-energize the line. Fortunately, when structures are not damaged, the 

outages are usually of short duration. 

Underground Power Lines: Widespread damage to belowground 

components of electrical systems due to earthquakes are not common, 

however, duct banks and their connections to manholes and hand holes, can 

FEMA P-1019 2: Natural Hazard Effects on Utilities and 2-19 

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be damaged when they cross fault lines or are located in areas that suffer 

ground failures due to geologic hazards, such as liquefaction. Since failures 

in underground systems take much longer to locate and repair than failures in 

overhead systems, extended outages can result unless power can be re-routed 

around damaged sections. 

Sub-stations: Postearthquake assessment reports, particularly those gathered 

following the 1971 San Fernando, California, earthquake, indicate that most 

of the damage to electrical transmission systems is to above ground 

equipment. Equipment in sub-stations, such as transformers, insulating 

bushings, surge arrestors, and switching equipment, are particularly 

vulnerable. Of particular significance was the loss of the Sylmar high 

voltage direct current converter station (See Figure 2-13), which impacted 

utility power capacity for months. Many sub-station components require 

long lead times to replace, and although most utilities maintain spare parts, a 

seismic event can cause damage so widespread that available spares are 

depleted, resulting in extended power outages.

Figure 2-13 Sylmar high voltage direct current converter station damaged in 

the 1971 San Fernando earthquake (NOAA/NGDC, E.V. 

Leyendecker, U.S. Geological Survey). 

2.5.2 Effects of Earthquakes on Building Systems 

Buildings respond dynamically to earthquake ground motion. The shaking 

intensity may increase by a factor of up to three at the roof level of a 

multistory building, compared to the shaking intensity at the ground level. In 

order to keep the cost of the structure within reason, building codes have 

long taken advantage of the ability of structural elements to deform 

Extensive loss of 

belowground utilities was 

experienced in the second 

Christchurch, New Zealand, 

earthquake due to 

liquefaction. 

2-20 2: Natural Hazard Effects on Utilities and FEMA P-1019

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inelastically without breaking in response to the earthquake, which dissipates

enormous amounts of energy. The advantage of this approach is that even in 

seismically active areas the increase in cost of the structure is to provide 

earthquake resistance to only a small fraction of the overall structural system. 

The disadvantage is that many elements of the structure will sustain damage.

If the structure were to be designed to remain elastic for earthquake loads

(elements of the structure remain undamaged) the cost of the structural 

system would be impractical for many buildings. 

Everything permanently anchored to the structure of a building but not part 

of the building structural system is referred to as a nonstructural component.

These items must be able to tolerate the combined demands of the 

earthquake-induced accelerations and building displacements. This means 

that nonstructural elements, such as cladding and windows, that are more 

likely to be damaged by the relative displacements of support points must be 

able to tolerate the displacements experienced by the building. Meanwhile,

nonstructural elements that are more likely to be damaged by seismic inertial 

forces must be able to withstand the seismic acceleration demands. 

Components mounted on vibration isolation springs or elastic mounts, such 

as generators and chillers, will experience significantly higher acceleration 

demands, and must be designed accordingly. Where flexible components, 

such as piping systems, are connected to relatively rigid components, the 

connections must be able to accommodate the relative displacements 

between the components (see Figure 2-14 for an example connection detail). 

Electrical and mechanical equipment that is vulnerable to acceleration 

demands should be well anchored (see example in Figure 2-15) and may 

require shake table testing to establish that they have the capacity to resist 

seismic shaking and remain operable. 

Observations after earthquakes consistently demonstrate that when 

nonstructural elements are properly attached to the building structure they 

perform well. Experience has also shown that if the entire MEP system is to 

survive, all of the interconnecting electrical raceways, process piping, and 

ductwork must be properly braced and installed. 

Earthquakes commonly damage architectural building elements, such as 

unreinforced masonry parapets, which can result in falling debris that can 

destroy exposed utilities and MEP equipment (See Figure 2-16), rendering 

the facility incapable of being quickly restored to operation. It is highly 

recommended that a rapid visual screening of an entire facility be conducted 

by qualified experts to identify vulnerable building components that threaten 

the seismic performance of essential MEP systems and, provide 

recommended actions to mitigate the hazards. The methodology set forth in 

FEMA P-1019 2: Natural Hazard Effects on Utilities and 2-21

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FEMA P-154, Rapid Visual Screening of Buildings for Potential Seismic 

Hazards: A Handbook (FEMA, 2014a), can be used for this screening.

Figure 2-14 Example of a connection which accommodates relative

displacements (FEMA, 2012b).

Figure 2-15 Well-anchored equipment (FEMA, 2012b). 

2-22 2: Natural Hazard Effects on Utilities and FEMA P-1019

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Figure 2-16 Falling debris from security wall and parapet damaged cooling 

equipment for servers resulting in the data center going off line 

in the 2011 Haiti earthquake.

For critical facilities where the tolerance for loss of operation and extended 

downtime is very low, base isolation of the entire building may provide a 

solution. Base isolated buildings are constructed on top of special bearings

(see Figure 2-17) that isolate the structure from earthquake ground motions, 

greatly reducing the intensity of shaking above the isolators. Flexible 

connections for all building utilities (see Figure 2-18) allow the isolators to 

laterally displace several feet without damage. Base isolation is not limited 

to buildings, and is beginning to be used to protect sub-station equipment. In 

recent large earthquakes in Chile and Japan, there are many examples of base 

isolated structures surviving the shaking with little or no damage.

Figure 2-17 Example of seismic isolation bearings and typical installation 

location (FEMA, 2007b).

FEMA P-1019 2: Natural Hazard Effects on Utilities and 2-23

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Figure 2-18 Typical flexible utility connections in base isolated building. 

2.5.3 Case Study – 1994 Northridge Earthquake 

The magnitude-6.7 Northridge earthquake occurred at 4:31 a.m. PST on 

January 17, 1994, near Los Angeles, California. It generated one of the 

highest ground accelerations recorded in a North American city (1.8 g) and 

shaking was felt as far away as Las Vegas, Nevada. The earthquake resulted 

in 60 deaths and over 7,000 injuries and produced an estimated $20 billion in 

damages. 

The Northridge earthquake induced soil liquefaction that damaged highvoltage transformers and the foundations of transmission-line towers. The 

resulting outage affected much of the greater Los Angeles area. Power was 

93% restored in 24 hours, and 99.5% restored in 72 hours. Total direct losses 

suffered by utilities include $138 million for the Los Angeles Department of 

Water and Power and $45 million for Southern California Edison (ASCE, 

1995). 

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The Northridge earthquake also triggered power outages as far away as 

British Columbia, Montana, Wyoming, Idaho, Oregon, and Washington. The 

longest disruption in those areas as a result of the earthquake was three

hours. This event demonstrates that earthquakes can cause interruptions in 

electrical networks well outside of the geographical location of the actual 

event, with implications for regions hundreds of miles away.

Emergency power systems in hospitals and emergency operations centers 

located in the affected area generally performed well following the 

Northridge earthquake. Many hospitals were forced to function for a week 

on emergency power because of the intermittent interruptions of utility 

power. However, 26 healthcare facilities did report issues with their 

emergency generators. Common problems documented by Office of 

Statewide Health Planning and Development are listed in Table 2-3. 

Table 2-3 Summary of Problems Related to Emergency Generators 

in the 1994 Northridge Earthquake (Office of Statewide 

Health Planning and Development, 1995)

Problem Number of Facilities

Generator failed to operate 6 

Damaged generator anchors 2 

Generator equipment damaged 1 

Generator anchors missing 7 

Unanchored batteries 8 

Unanchored fuel tank 5 

Unbraced exhaust stack 2 

The following are specific reasons some emergency generators in healthcare 

facilities failed to operate following the Northridge earthquake (Office of 

Statewide Health Planning and Development, 1995):

• Berkeley West Convalescent Hospital, Santa Monica: Offsite natural gas 

fuel supply was interrupted

• Chandler Convalescent Hospital, North Hollywood: Underground fuel 

tank was damaged

• Crescent Bay Convalescent Hospital, Santa Monica: Generator could not 

be started due to battery failure

2.6 Other Events 

In addition to natural hazards listed above, there are other events that have 

recently resulted in loss of power. 

FEMA P-1019 2: Natural Hazard Effects on Utilities and 2-25 

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2.6.1 Case Study – Solar Storms of 1989 and 2012

In March of 1989 a solar storm (also called a geomagnetic disturbance 

(GMD) or solar flare) led to the collapse of the Hydro-Quebec transmission 

systems. Six million customers were without power for nine hours before the 

system could be restored to normal operation (Hadhazy, 2009). 

A much larger solar storm developed in 2012 but narrowly missed the earth 

(Liu et al., 2014). This event was estimated to have been twice the sized of 

the largest known solar storm to strike the earth in 1859 that disrupted 

telegraph operation over the entire earth. If this event had occurred nine days 

earlier, it would have struck earth and the damage to earth-orbiting satellites, 

ground-based communications, and bulk power transmission systems could 

have taken as long as four years to fully restore. 

2.6.2 Case Study – Northeast Blackout of 2003

On August 14, 2003, the largest blackout to affect North America occurred. 

At its peak, over 50 million customers were without power for up to two 

days. Large sections of the northeast and Canada were affected, including

New York City, which lost power (NERC, 2004). The event has been 

extensively studied and many conclusions and recommendations have been 

developed to help prevent its recurrence. 

The problem originated when a generating unit in Northern Ohio went 

offline. This occurred at 1:31 PM while an operator was making voltage 

adjustments. This relatively common occurrence would typically be easily 

remedied by drawing additional power from other online sources to make up 

for the production loss of a single generator. However, 45 minutes after the 

generating unit tripped offline, the alarm and logging system that monitored

a large portion of the network failed. Over the next two hours, the operators, 

without the help of an alarm and logging system, were not able to detect

actual conditions in the grid and were unable to take appropriate actions to 

manage it. As loads shifted to account for loss of generating units or the loss 

of transmission lines, portions of the network became overloaded; heated 

electrical lines sagged and came in contact with inadequately trimmed trees; 

circuit breakers protecting those transmission lines tripped and the rapid 

reduction in electrical demand that resulted when transmission lines tripped

offline caused generators to overspeed and automatically trip offline in an 

attempt at self-preservation.

At its peak, 531 generating units at 263 plants shut down, interrupting about 

65,000 MW of load. The event resulted from no natural hazard and few, if 

any, physical damages affecting the grid. 

2-26 2: Natural Hazard Effects on Utilities and FEMA P-1019

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Chapter 3 

Disaster Management and 

Operations Continuity 

A strategy must be developed to protect assets, limit damage and injuries, 

restore operations, and coordinate the resources that are needed to effectively 

respond to a disaster event. Without effective and continuous planning, the 

impact of a disaster on a business, a community, or a region will be truly 

catastrophic. The goal of this chapter is to provide guidance on instituting a 

disaster planning process.

In the United States, the foundation for planning for disasters is the National 

Preparedness Goal (FEMA, 2014b):

“A secure and resilient nation with the capabilities required 

across the whole community to prevent, protect against, 

mitigate, respond to, and recover from the threats and hazards 

that pose the greatest risk.”

The goal can be applied at the federal, state and local government levels, and 

within the private sector. Without the commitment of the business and 

industrial sectors to effective disaster planning, the “whole community” as 

described in the National Preparedness Goal will never be secure and 

resilient. Disaster preparedness is not the sole responsibility of government;

facility owners and operators have an obligation as part of the “whole 

community” to plan and prepare for catastrophic events. The social needs of 

a community are supported by buildings and utilities that also need to remain 

functional. In particular, critical facilities need to define performance goals 

for desired levels of functionality for immediate, short term, and long term 

recovery plans.

Consequences from natural catastrophes continue to be on the rise primarily 

because of increased development in vulnerable areas. Furthermore, the 

dependence on technology increases a facility’s vulnerability to powersupply interruptions, loss of data, and the loss of ability to manage operations

with internet-dependent remote stations. Supply chains (including energy 

resources) are especially vulnerable to disasters which means that the event 

could be thousands of miles away. Without a disaster plan in place, a facility 

could suffer irreversible harm from events both near and far.

FEMA P-1019 3: Disaster Management and Operations Continuity 3-1
The failure to be able to react effectively to a disaster will have a significant 

negative impact on the financial performance and reputation of a company. 

3.1 Critical Facilities

All organizations should have disaster plans, but it is essential for the owners 

and operators of critical facilities and infrastructure to plan for catastrophic 

events. Performance goals for recovery plans should address the role of a 

critical facility within the community.

NIPP 2013: Partnering for Critical Infrastructure Security and Resilience

(Department of Homeland Security, 2013) defines critical infrastructure as 

“systems and assets, whether physical or virtual, so vital to the United States 

that the incapacity or destruction of such systems and assets would have a 

debilitating impact on security, national economic security, national public 

health or safety, or any combination of those matters.” While this definition 

focuses on critical infrastructure of national importance, state and local 

governments have identified assets in their respective jurisdictions that they 

consider to be critical infrastructure. A critical facility can be defined as a 

facility that is essential for the delivery of vital services or protection of a 

community. Critical facilities include, but are not limited to, hospitals, 

emergency operations centers, fire and police stations, schools, and primary 

utility and transportation facilities (FEMA, 2013).

Table 1604.5 in Section 1604.5 of the 2012 International Building Code 

(ICC, 2012) provides Risk Category classifications for buildings and other 

structures that address minimum design criteria based on the facility type and 

their role in many communities (Table 3-1). These Risk Category 

classifications are aligned with ASCE/SEI 7-10, Minimum Design Loads for 

Buildings and Other Structures (ASCE, 2010), which provides specific 

design criteria for each Risk Category type. While previous editions of

ASCE/SEI 7 contained a detailed list of what facilities were to be included in 

each Risk Category, the 2010 edition of ASCE/SEI 7 moved the descriptions 

of Risk Categories to the commentary and removed specific occupancy 

requirements. This was because it was felt that specific population number 

thresholds, such as more than 250 students in schools for younger children, 

may lead to incomplete consideration of all the factors that a decision maker 

must consider. The ASCE/SEI 7-10 approach supports the identification of 

the appropriate risk category for a facility based on the guidance that 

considers the impact of facility failure on the community. However, as a 

minimum, the facilities must at least satisfy IBC Section 1604.5.

Approximately 85% of all 

critical infrastructure in the 

United States is privately 

owned (Department of 

Homeland Security, 2014). 

Accordingly, the private 

sector plays a key role in 

planning efforts to protect 

and increase the resilience 

of critical infrastructure.

3-2 3: Disaster Management and Operations Continuity FEMA P-1019
Table 3-1 Risk Category of Buildings and Other Structures (IBC 2012, Table 1604.5)

Risk 

Category Nature of Occupancy

I 

Buildings and other structures that represent a low hazard to human life in the event of failure, 

including but not limited to:

• Agricultural facilities. 

• Certain temporary facilities.

• Minor storage facilities.

II Buildings and other structures except those listed in Risk Categories I, III, and IV.

III

Buildings and other structures that represent a substantial hazard to human life in the event of 

failure, including but not limited to:

• Buildings and other structures whose primary occupancy is public assembly with an occupant 

load greater than 300.

• Buildings and other structures containing elementary school, secondary school or day care 

facilities with an occupant load greater than 250.

• Buildings and other structures containing adult education facilities, such as colleges and 

universities, with an occupant load greater than 500.

• Group I-2 occupancies with an occupant load of 50 or more resident care recipients but not 

having surgery or emergency treatment facilities.

• Group I-3 occupancies.

• Any other occupancy with an occupant load great than 5,0001

. 

• Power-generating stations, water treatment facilities for potable water, waste water treatment 

facilities, and other public utility facilities not included in Risk Category IV.

• Buildings and other structures not included in Risk Category IV containing quantities of toxic 

or explosive materials that:

o Exceed maximum allowable quantities per control area as given in [2012 IBC] Table 

307.1 (1) or 307.1 (2) or per outdoor control area in accordance with the International 

Fire Code; and

o Are sufficient to pose a threat to the public if released2

. 

IV

Buildings and other structures designated as essential facilities, including but not limited to:

• Group I-2 occupancies having surgery or emergency treatment facilities.

• Fire, rescue, ambulance and police stations, and emergency vehicle garages.

• Designated earthquake, hurricane, or other emergency shelters.

• Designated emergency preparedness, communications and operations centers and other 

facilities requires for emergency response.

• Power-generating stations and other public utility facilities requires as emergency backup 

facilities for Risk Category IV structures.

• Building and other structures containing quantities of highly toxic materials that:

o Exceed maximum allowable quantities per control area as given in [2012 IBC] Table 

307.1 (2) or per outdoor control area in accordance with the International Fire Code; and

o Are sufficient to pose a threat to the public if released2

. 

• Aviation control towers, air traffic control centers and emergency aircraft hangars.

• Buildings and other structures having critical national defense functions.

• Water storage facilities and pump structures required to maintain water pressure for fire 

suppression.

 1 For purposes of occupant load calculation, occupancies required by [2012 IBC] Table 1004.1.2 to use gross 

floor area calculations shall be permitted to use net floor areas to determine the total occupant load.

 2 Where approved by the building officials, the classification of buildings and other structures as Risk Category 

III or IV based on their quantities of toxic, highly toxic, or explosive materials is permitted to be reduced to 

Risk Category II, provided it can be demonstrated by a hazard assessment in accordance with Section 1.5.3 of 

ASCE 7 that release of the toxic, highly toxic, or explosive materials is not sufficient to pose a threat to the 

public.

FEMA P-1019 3: Disaster Management and Operations Continuity 3-3 
Selection of a risk category implies specific minimum design load levels and 

associated design criteria that are to be used for design. Risk Categories III 

and IV address critical facilities and in their definitions, note the emphasis on

the intended use of the facility and exposed population. For instance, a 

school is often classified as a Risk Category III facility but if it will be used 

as a shelter, as a minimum, that section of the facility should be classified as 

a Risk Category IV facility. 

3.1.1 Determining if a Facility is Critical

The process to determine whether your facility is critical is straightforward. 

• Has a federal, state, or local government agency sent a notification that 

the facility has been classified as critical?

• Does the facility fit Risk Categories III or IV as defined in Section 

1604.5 of the IBC?

It is important to note that the definitions of “critical infrastructure” and 

“critical facilities” will vary depending on who is asking the question. The 

federal government focuses on critical infrastructure that will have a national 

impact. At the local level, however, even small facilities or structures can be 

considered critical. For example, the local gas station that provides fuel for 

volunteer firefighters and health care workers could be defined as “critical.” 

A local school or college facility could be used for evacuation sheltering, and 

nursing homes and assisted living facilities are often included in disaster 

surge capacity planning for acute care hospitals.

3.2 Emergency Preparedness and Business Continuity 

Planning

Planning that is based on an effective risk assessment process is the most 

effective way to mitigate the impact of a crisis on the financial health, 

reputation and long-term recovery of an organization. Fortunately, it is not 

necessary to re-invent the wheel; a great deal of reliable guidance is available 

to guide facility owners/operators in the development of disaster 

management and business continuity programs and plans.

3.2.1 PS-Prep

The U.S. Department of Homeland Security (DHS) has established a 

voluntary private sector preparedness accreditation and certification program 

known as PS-Prep. The program provides free, on-line resources that are 

designed to improve the preparedness of private-sector and not-for-profit 

organizations to consensus-based preparedness standards and best practices. 

The program focuses on the ability of organizations to identify and 

3-4 3: Disaster Management and Operations Continuity FEMA P-1019
implement steps to address business continuity, organizational resilience, and 

emergency and disaster management. DHS provides recognition for those 

entities that certify to the adopted preparedness standards.

As a voluntary program, PS-Prep serves as a resource for private and nonprofit entities interested in instituting a comprehensive business continuity 

management system. PS-Prep offers organizations the opportunity to 

develop and maintain certification to nationally recognized and respected 

approaches to resilience and preparedness. See http://www.fema.gov/aboutps-preptm. 

Three standards have been adopted by DHS under the PS-Prep Program:

• NFPA 1600, Standard on Disaster/Emergency Management Continuity 

Programs (NFPA, 2013b); 

• ASIS SPC. 1-2009, Organizational Resilience: Security, Preparedness, 

and Continuity Management Systems - Requirements with Guidance for 

Use (ASIS, 2009); and

• ISO 22301:2012, Societal Security—Business Continuity Management 

Systems—Requirements (ISO, 2012). 

Of these, the mostly commonly used is NFPA 1600, which establishes a 

common set of criteria for “all hazards” disaster/emergency management and 

business continuity programs. The standard provides the fundamental 

criteria to develop, implement, assess, and maintain activities for prevention, 

mitigation, preparedness, continuity, and recovery. The standard applies to 

private entities as well as public, not-for-profit, and nongovernmental 

organizations. 

Because there is no one size fits all emergency plan, NFPA 1600 enables an 

organization to customize a disaster management and business continuity 

program to its own specific needs and circumstances. The key elements of a 

program established in accordance with NFPA 1600 include the following:

• Program Management. In order to be successful, a disaster 

management/business continuity program must have the full 

commitment of the leadership of the organization. Commitment is 

demonstrated by a willingness to provide the necessary resources and by 

ensuring that the program is reviewed, evaluated and updated as 

necessary. A program coordinator is responsible for overall 

development, implementation and administration, with support from a 

program committee selected from key functional areas within the 

organization as well as external representatives, such as the local 

NFPA 1600 is available as a 

free, downloadable PDF at 

www.nfpa.org

FEMA P-1019 3: Disaster Management and Operations Continuity 3-5 
emergency management agency, fire service, or hospital. 

Documentation of program activities is essential, including the 

establishment of an executive policy that specifies the vision, mission 

statement, roles, responsibilities, and enabling authority. In addition, the 

costs and resources needed for the program should be clearly established.

• Planning. The planning and design process establishes the basis for the 

implementation of a plan that is customized to meet the specific risks and 

threats that are faced by the organization. During the planning process, 

three important evaluations should be performed:

o Risk Assessment: This is a process that identifies the natural hazards, 

human-caused events, and technology-caused events that are likely 

to be encountered. The vulnerability of people, property, operations, 

the environment and the entity itself should be assessed. In addition, 

the impact of the identified hazards should be evaluated. Risk 

assessment also examines the potential cascading effects of regional, 

national, or international incidents.

o Business Impact Analysis. This is an evaluation of the potential 

impact resulting from the interruption or disruption of individual 

functions, processes, and applications. This analysis includes a 

review of critical functions, processes, infrastructure, systems and 

applications and is used in the development of recovery strategies. 

o Resource Needs Assessment. This is based on the findings of the risk 

assessment and the business impact analysis. This assessment 

determines what human resources, equipment, training, facilities, 

funding, expert knowledge, materials, technology, information and 

intelligence will be needed to plan for, respond to, and recover from 

an event.

• Implementation. The implementation phase of NFPA 1600 describes 

the various plans and support functions that should be developed.

o Prevention: Development of a strategy that prevents an incident that 

could threaten life, property or the environment.

o Mitigation: Development of a strategy that includes measures to be 

taken to limit or control the consequences, extent or severity of an 

incident that cannot be prevented.

o Crisis Communications and Public Information: Development of a 

plan and procedures to disseminate information and establish a crisis 

communications capability.

Chapter 12 of NFPA 99, 

Health Care Facilities Code

(NFPA, 2012a), establishes 

the criteria for developing 

emergency management 

programs in new and 

existing health care 

facilities. NFPA 1600 is the 

foundation for this chapter.

3-6 3: Disaster Management and Operations Continuity FEMA P-1019
o Warning, Notifications, and Communications: Development of a 

reliable, redundant, and interoperable warning, notification, and 

communications capability.

o Operational Procedures: Development of operational procedures to 

support the program, including response, recovery, continuity, and 

mitigation.

o Incident Management: Development of an incident management 

system (IMS) to direct, coordinate, and control response, continuity 

and recovery operations.

o Emergency Operations Centers (EOCs): Establishment of a primary 

and alternate EOC, either physical or virtual, to manage response, 

continuity and recovery operations.

o Emergency Operations/Response Plan: Development of a plan that 

defines responsibilities for carrying out specific actions during an 

emergency.

o Business Continuity and Recovery: Development of a plan that 

includes recovery strategies to maintain critical or time-sensitive 

functions and processes.

o Employee Assistance and Support: Development of a strategy to 

support employees and their families during an emergency.

• Training and Education. A training and education curriculum should 

be developed with the goal of creating awareness and enhancing the 

knowledge, skills, and abilities required to implement, support, and

maintain the program. The program should include training on the 

incident management system (IMS) that is used by the organization 

during an event.

• Testing and Exercises. Testing and exercises are a critical component 

of any disaster preparedness and business continuity program. Exercises 

are designed to evaluate program plans, procedures and capabilities, and 

they provide a standardized methodology to practice procedures and 

interact with other entities in a controlled setting. They should be 

conducted on a regular basis so that required preparedness and response 

capabilities can be established and maintained. The FEMA Emergency 

Management Institute offers a free, on-line self-study course, IS-139 

Exercise Design. This course is designed as an introduction to the 

fundamentals of exercise design and to help design and conduct a small 

functional exercise for at the attendee’s organization. See 

http://training.fema.gov/IS/

FEMA P-1019 3: Disaster Management and Operations Continuity 3-7
• Program Maintenance and Improvement. The program should be 

evaluated on a regularly scheduled basis to ensure that the policies, 

performance objectives, and program implementation continue to be 

effective. Reviews should also be conducted based on post-incident 

analyses, lessons learned, and operational performance, or when internal 

or external conditions change that might impact the effectiveness of the 

program. Corrective action should be taken whenever deficiencies have 

been identified.

3.2.2 Issues to be Considered in the Disaster Preparedness Plan

The after-action reports and lessons-learned from Hurricane Sandy and other 

recent catastrophic events have identified a number of common deficiencies 

related to the loss of emergency power that should be addressed in the 

disaster preparedness and business continuity plan. Some examples of areas 

that should be included are as follows:

• Fuel delivery/fuel availability for standby power sources. A risk 

assessment study should determine the expected length of time needed to 

continue the operation of emergency generators. The plan should 

address such issues as:

o Reliable on-site storage of fuel. It is important to note that there are 

requirements in codes and standards that must be complied with in 

order to ensure that the fuel storage system is not an undue fire or 

explosion hazard,

o Contracts with fuel suppliers, including delivery, 

o Alternative fuel sources, 

o Capabilities and authorization to deliver fuel and critical 

maintenance supplies (e.g., filters) within restricted disaster zones, 

and 

o Generator maintenance, testing, and repair (both preventive and 

during the event). 

• Coordination/input from government agencies (state and local 

emergency management, fire service, law enforcement). The 

organization should establish a working relationship with local, regional 

or state emergency response authorities. The authorities can provide 

guidance and input during the development and implementation of the 

planning process and will be a critical resource during the disaster event. 

Emergency managers and first responders should be invited to participate 

in the development of the facility’s emergency operations and business 

3-8 3: Disaster Management and Operations Continuity FEMA P-1019
continuity plan. They can also be a valuable resource during drills and 

exercises that test the effectiveness of the plan. The facility plan should 

embrace key elements of the local emergency response plan to ensure 

proper coordination of critical activities, such as warnings, notifications, 

incident management, and evacuation. Authorizations for personnel to 

remain within or re-enter evacuation zones because of critical facility 

needs should be determined as part of the pre-event planning process.

• Situational awareness is critical to the success of response and recovery 

operations. The organization should utilize technologies to monitor onsite conditions, alerts and advisories from government agencies, weather 

conditions and other potential threats, the status of employees and their 

families, and the condition of supply chains and other resources. An 

internal and external communication plan is critically important and 

should include the ability to monitor social media and control rumors.

• Redundancy of operational facilities, data systems, remote operation 

(SCADA) systems and supply chains may be the most cost-effective 

strategy for emergency preparedness and business continuity. 

• Food and water supplies are a critical aspect of emergency planning. 

Supermarkets typically have only a two- to three-day supply of food in 

stock and their resources are quickly depleted by the general population. 

Critical facility operators should plan for alternative sources for food and 

water.

• The delivery of fuel and essential maintenance supplies (such as filters) 

within restricted disaster zones should be pre-approved by public safety 

officials in order to ensure access to the facility.

• A system must be developed that provides important operational 

information to key officials (up the chain of command).

• Staffing needs must be part of the operational plan, including the need 

for relief personnel for an extended incident.

• Implementation timing. Some equipment or personnel may not be 

immediately in place for an emergency. Plans must consider the timing 

necessary to place important elements into operation.

FEMA P-1019 3: Disaster Management and Operations Continuity 3-9

Chapter 4

Identifying Emergency Power 

Needs in Critical Facilities

A key element in the design of an emergency power system in a critical 

facility is to understand and determine the appropriate power needs in the 

event of a loss of utility power. The emergency power needs must be 

identified and assessed based on code requirements and on the essential 

services that must be maintained in order for the facility to maintain its 

critical functions. Emergency power needs in critical facilities fall into two 

broad categories:

• Emergency power needs established by building code and standards. 

The three primary sets of such requirements for the purposes of this 

document are contained in the 2012 International Building Code (IBC; 

ICC, 2012), NFPA 101, Life Safety Code (NFPA, 2012b), and NFPA 99,

Health Care Facility Code (NFPA, 2012a).

• Emergency power needs required to support the functionality of the 

critical facility. Following a hazardous event, critical facilities must 

continue to operate albeit at some reduced level of operations and select 

equipment must be powered to support those operations. The operation 

of non-essential systems and equipment often constitutes a desired use

that can only be met when cost effective emergency power is available. 

Emergency power should be limited to that required for essential services 

that must be maintained for the facility to function as required or as 

expected following a loss of utility power.

After code requirements and emergency power needs for functionality have 

been identified and demands have been limited to essential systems only, a 

detailed analysis of electrical power needs beyond code minimums should be 

conducted.

The following sections describe the identification of emergency power needs 

for each of the categories and needed duration of emergency power, where 

applicable. Section 4.3 provides a comparison of the emergency power 

requirements and needs along with a discussion of how needs must be 

limited in order to keep the critical functions of the facility operational.

FEMA P-1019 4: Identifying Emergency Power Needs in Critical Facilities 4-1
4.1 Requirements for Emergency Power Specified by 

Building Codes and Standards

Building codes and their referenced engineering and technical standards

govern the design and construction of most new buildings. They also often 

apply to major renovations, repairs, or substantial improvements to existing 

buildings. The purpose of a building code is to establish the minimum

acceptable design and construction requirements necessary for protecting the 

public’s health, safety, and welfare. Structural integrity (for both gravity 

loads and loads imposed by external hazards, such as wind, earthquake, and 

flooding), building envelope integrity, fire and smoke resistance, life-safety 

considerations, sanitation, and recently, energy efficiency, are some of the 

issues addressed by contemporary building codes and engineering standards.

Some portions of the building code consider the importance of critical

facilities performing their essential functions after extreme natural hazards by 

adding significantly greater requirements for resistance to some natural 

hazards. However, code requirements for emergency power are generally 

not directed at continued operation of the facility. They generally focus on 

emergency power required to allow people to evacuate a building quickly 

and safely. Appendix A provides a detailed description of requirements in 

widely adopted codes and referenced standards for emergency power in 

critical facilities.

While the intent of the International Building Code includes “other hazards,”

emergency power requirements for most buildings are based on fire as the 

primary hazard with additional requirements in areas where flooding, high 

winds, or earthquakes are to be expected. Fire and life-safety requirements 

are generally based on a 90-minute to two-hour window of time to provide 

egress of building occupants and protection of first-responders for expected 

durations of fire-fighting or evacuation taking place.

The code generally does not require provision of enough emergency power to 

allow buildings to remain functional during a power outage except for 

systems such as elevators in high-rise buildings or large assembly spaces 

where the conveying systems may be used by first responders to fight a fire 

or evacuate building occupants. The code-required 90-minutes of emergency 

power (excluding elevator power) can be supplied by batteries or other stored 

energy devices; in most cases, emergency generators are not required to 

satisfy code duration requirements. For the small percentage of facilities 

where onsite generators are needed to satisfy code requirements, the 

generators typically only supply the minimum loads required for life safety. 

Life-safety loads include fire alarm and annunciation systems, smoke control 

A critical facility that is 

fully compliant with the 

minimum building code 

requirements may not be 

able to operate as needed 

or provide the expected 

services when power is 

lost. 

4-2 4: Identifying Emergency Power Needs in Critical Facilities FEMA P-1019
systems, emergency and egress lighting, and conveyance systems that are 

required for egress. In most cases, onsite generators required by code have 

neither the power generation capacity nor the fuel supply that a facility needs 

to remain functional during prolonged power outages.

4.2 Emergency Power Requirements 

This section discusses the conduct of a needs assessment to identify how 

long a critical facility must remain functional while using emergency power 

and what equipment needs to be operational to allow the facility to function. 

An example of the type of planning that is necessary based on anticipated 

need and use is that for Emergency Operations Centers. These facilities, 

which are designed for disaster response, are often provided with emergency 

power sufficient for 100% operation of the entire facility with onsite fuel 

capacity, allowing full-scale operations for a week or more. This duration is 

not code mandated, but the result of a careful review of when the center will 

be most needed and for how long.

The functional duration identified affects both what loads are supplied and 

how they are supplied. Typically, the most significant effect on the 

emergency power requirements of a facility is its location in relation to 

climatic conditions and whether air conditioning equipment needs to be 

supplied from an emergency power system. Additionally, the purpose of the 

critical facility plays a significant role in determining emergency power 

needs. For example, if the facility only needs to remain functional for 

several hours (as in a tornado safe room), equipment required for heating or 

food preparation does not need to be powered. In contrast, heating or food 

preparation equipment would need a power supply in a host shelter facility 

used after an ice storm, major flood event or a hurricane expected to operate

for several days or weeks. 

The duration that a facility must remain functional depends on the use of the 

facility, which is typically easy to identify, and on the length of time utility 

power will be out, which is difficult to quantify in advance of an event. The 

duration of a power outage can range from a few minutes to several weeks

(though it is rare for utility power to be unavailable for longer than one

month since mutual assistance allows most utilities to rebuild damaged 

utilities as soon as practical).

There are no hard and fast guidelines for assessing the emergency power 

needs of a critical facility. The following approach identifies four levels of 

operation, each with a different duration and need for supply of emergency 

power: 

FEMA P-1019 4: Identifying Emergency Power Needs in Critical Facilities 4-3
• Level IA operations are based on the minimum code requirements from 

the International Building Code. These operations include electrical 

loads that are required for short-duration use only, such as fire alarm 

equipment, exit and egress lighting, and starting and operating fire 

pumps (when present), as well as the minimum lighting equipment 

required to allow occupants to move throughout the facility. The 

expected duration of these operations is typically 90 minutes. The 

purpose of these requirements is to allow safe egress or occupant 

relocation from a building in an emergency and to provide a minimal 

level of illumination or equipment operations for first-responders to 

assist in evacuation of the building. With only a few limited exceptions 

for certain building uses or types, minimum requirements of the IBC are 

not intended to provide operational levels of illumination or power to 

allow continued use of the facility. For the code required 90-minute 

duration, power supplies are sized for the code-mandated loads and will 

likely not allow anywhere near normal operations of the facility. 

Therefore, significant additional emergency power provisions are likely 

necessary for continued operation of facilities beyond those provided for 

Level IA operations.

• Level IB operations are defined as those required for critical health care 

facilities per NFPA 99, Health Care Facilities Code. Appendix A

provides a detailed discussion of these requirements. These requirements 

are meant to apply in conjunction with the requirements of Level IA and 

do not supplant Level IA requirements. Although written specifically to 

apply to health care facilities, the principles of power distribution and 

requirements for selection of systems to be operated on emergency 

power provide good guidance for all types of critical facilities. Note that 

even when the criteria of Level IB are met, there may be unpowered 

operations based on facility-specific needs. Significant additional 

emergency power provisions are still likely to be necessary for continued 

operation of facilities beyond those provided for Level IB operations.

• Level II operations are defined as facilities that must remain operational

for more than just the duration of emergency occupant evacuation, but do 

not require air conditioning. Level II operations include electrical loads 

for Level IA (and Level IB for healthcare facilities) in addition to 

powering heating and ventilation systems and food preparation and 

preservation equipment. Additionally, operational systems, such as 

computers and other radios, may need to be accommodated in this level

as well, since the power demands of these systems will likely exceed the 

capacity of the battery or rechargeable (UPS) systems based on 

anticipated duration of operations. Longer term Level II operations may 

4-4 4: Identifying Emergency Power Needs in Critical Facilities FEMA P-1019
come into play when a facility needs to be used for longer than 12 hours 

or when the facility provides food for occupants. Loads supplied under 

Level II operations may not be adequate under extreme weather 

conditions, particularly during periods of extreme high exterior 

temperatures or high humidity. In addition, it is important that limits be 

assessed for areas that may not need heating, ventilation, food service, or 

other operational support such as computing or communications. During 

the planning process, it is imperative to ascertain the anticipated duration 

of operations and to identify which operations can be curtailed during an 

emergency to reduce demand on the critical facility support mechanisms.

• Level III operations are defined as facilities that must remain operational 

and must provide air conditioning in at least some areas. Level III 

operations include electrical loads required for both Levels I and II in 

addition to equipment required for air conditioning. Level III capacities 

are appropriate for long-duration use during periods of high exterior 

temperatures or high humidity levels when air conditioning is needed for 

a facility to remain functional. It is important that limits be assessed for 

areas that may not need air conditioning or other mechanical systems, 

food service, or other support systems. It may be possible to curtail 

certain operations during an emergency to reduce demand on the critical 

facility support mechanisms and achieve Level II operations.

4.3 Assessing Emergency Power Needs in Detail

Assessing emergency power needs requires determining what equipment 

must operate for a facility to function during a power outage. The design and 

construction and the mechanical and electrical layouts of critical facilities 

vary greatly, so it is not possible to provide specific guidance and 

requirements for all facilities. However, the following general discussion 

will help facility managers identify which equipment should have backup 

emergency power. 

While detailed code requirements are based on the occupancy classification 

(e.g., a hospital) and size (e.g., a high-rise) of the facility, the basic 

requirements for each system are fairly consistent. Table 4-1 presents a 

simplified checklist of systems that should be considered, in the general 

order as the levels of operation discussed in the previous section. Many of 

the items noted in Table 4-1 may not be required by the code, but must be 

considered in the design of the emergency electrical systems for critical 

facilities. Some items in the table may have varying requirements for 

different occupancies or building types. Examples of these are elevators, 

lighting, ventilation, water supply, sanitary sewer pumps, sump pumps, and 

FEMA P-1019 4: Identifying Emergency Power Needs in Critical Facilities 4-5
air conditioning. In addition, Table 4-1 does not take into account that 

engineering requirements for certain life-safety systems and structural 

systems will vary by location. Thus, design requirements for earthquakeprone areas may vary from those in high-wind areas or in flood zones. 

Table 4-1 is intended to give guidance on options for providing emergency 

power over the range of levels that facility operators may elect to pursue. 

Column for Level IA describes the basic code requirements from the 

International Building Code. The third column (Level IB) describes the 

requirements from NFPA 99 Health Care Facilities Code. NFPA 99 Health 

Care Facilities Code defines three branches within an emergency distribution 

system: (1) equipment branch; (2) critical branch; and (3) life-safety branch. 

Of these, the life-safety branch is the most important and given the highest 

priority. Each of the systems with code mandates can be presumed to have 

the phrase “where required by the code for the intended use” appended to 

them. Appendix A provides further discussion of the requirements contained 

in various codes and referenced standards.

It is assumed here that the basic code-mandated functions in both parts of

Level I will continue to be maintained for whatever duration the facility 

remains in operation. The fourth column lists the requirements for Level II 

operations. The fifth column shows Level III operations that are 

discretionary uses, including the other levels, but with the addition of air 

conditioning loads.

The following subsections provide guidance on the emergency power needs 

of life-safety equipment, fire pumps, lighting, mechanical equipment 

(heating, ventilation, plumbing, and air conditioning), food preparation 

facilities, and other items that are commonly found in critical facilities.

4.3.1 Life-Safety Equipment

Although life-safety equipment is designed primarily to allow occupants to 

safely exit a building, it is just as important when people must stay in a 

building during an extended power outage. Code-required fire and smoke 

alarm systems, exit signage, and egress lighting must remain powered while 

the facility is in use. Figure 4-1 depicts life-safety equipment required by the 

International Building Code for several occupancy classifications.

4-6 4: Identifying Emergency Power Needs in Critical Facilities FEMA P-1019
Table 4-1 Elements Potentially Requiring Emergency Power

Duration of Operation

Level IA

Basic IBC Requirements

Level IB 

NFPA 99 Requirement for 

Critical Healthcare Facilities

Level II

Discretionary Uses

Without Air Conditioning

Level III

Discretionary Uses

With Air Conditioning

90-Minute Minimum 

Duration Per NFPA 99 As Needed As Needed

Exit signs   

Life-Safety Branch

  

Means of egress illumination 

(code minimum is for 

emergency egress only) 

 

Life-Safety Branch

 



(if continued use is desired, 

requires discretionary increase)



(same scope as Level II)

Elevator car lighting and 

communications

  

Life-Safety Branch 

  

Emergency alarm systems   

Life-Safety Branch 

  

Emergency communications 

systems

  

Life-Safety Branch 

  

Electrically powered fire 

pumps and jockey pumps 



(if required) 

 

Life-Safety Branch

  

Power operated doors and 

locks

 

(if required for occupant 

security or egress) 

 

Life-Safety Branch 

 

Generator set location lighting 

and local power

  

Life-Safety Branch 

 

Ventilation of smokeproof 

enclosures 

 

(if ventilation is required by 

code) 

 

Equipment Branch

 

(if code requirement, continue 

operations) 

 

(if code requirement, continue 

operations)

Legend:

 

 Required for code minimum durations 

 Discretionary increase if continued operation of system is required for continued occupancy

 Discretionary increase, added at the indicated level

 Air conditioning systems to be provided with emergency power

FEMA P-1019 4: Identifying Emergency Power Needs in Critical Facilities 4-7 
Table 4-1 Elements Potentially Requiring Emergency Power (Continued)

Level IA

Basic IBC Requirements

Level IB 

NFPA99 Requirement for 

Critical Healthcare Facilities

Level II

Discretionary Uses 

Without Air Conditioning

Level III

Discretionary Uses

With Air Conditioning

Duration of Operation

90-Minute Minimum 

Duration Per NFPA 99 As Needed As Needed

Smoke control system  

(if smoke control is required 

by code)

 

Equipment Branch



(if code requirement, continue 

operations)



(if code requirement, continue 

operations)

Horizontally sliding electric 

doors



(if doors are used for egress) 

 

Life-Safety Branch



(if code requirement, continue 

operations)



(if code requirement, continue 

operations)

Elevator operations  

(only in occupancies 

requiring fire service use for 

elevators, e.g., high-rise, 

atrium) 

 

Equipment Branch



(if code requirement, continue 

operations)



(emergency power will be 

required for short term 

operational uses)



(if code requirement, continue 

operations)



(same scope as Level II)

Platform lifts 

(if used for accessibility)



(if code requirement, continue 

operations)



(if provided for operational

reasons, verify number of lifts 

to be powered)



(if code requirement, continue 

operations)



(same scope as Level II)

Task lighting outside of egress 

paths

 

Critical Branch



(extent as required outside of 

egress paths for short term 

critical operations)



(same scope as Level II)

Legend:

 Required for code minimum durations 

 Discretionary increase if continued operation of system is required for continued occupancy

 Discretionary increase, added at the indicated level

 Air conditioning systems to be provided with emergency power

4-8 4: Identifying Emergency Power Needs in Critical Facilities FEMA P-1019
Table 4-1 Elements Potentially Requiring Emergency Power (Continued)

Level IA

Basic IBC Requirements

Level IB 

NFPA 99 Requirement for 

Critical Healthcare Facilities

Level II

Discretionary Uses 

Without Air Conditioning

Level III

Discretionary Uses

With Air Conditioning

Duration of Operation

90-Minute Minimum 

Duration Per NFPA 99 As Needed As Needed

Sump pumps  

Equipment Branch 



(if required to prevent 

damaging water accumulation)



(same scope as Level II)

Ventilation for identified 

operational areas

  

Equipment Branch



(for minimum number of 

ventilation fans at areas 

required for critical operations)



(same scope as Level II)

Telephone equipment  

Critical Branch



(Can use short term UPS for 

charging, mobile phone 

charging systems or central 

switchboard)



(same scope as Level II)

Sewage lift pumps  

(same scope as Level II)

Water system booster pumps 

(if required for adequate 

system pressure in critical 

areas)



(same scope as Level II)

Domestic hot water circulator 

pumps

 

(if low power use and serving 

areas required for critical 

operations)



(same scope as Level II)

Legend:

 Required for code minimum durations 

 Discretionary increase if continued operation of system is required for continued occupancy

 Discretionary increase, added at the indicated level

 Air conditioning systems to be provided with emergency power

FEMA P-1019 4: Identifying Emergency Power Needs in Critical Facilities 4-9
Table 4-1 Elements Potentially Requiring Emergency Power (Continued)

Level IA

Basic IBC Requirements

Level IB

NFPA 99 Requirement for 

Critical Healthcare Facilities

Level II

Discretionary Uses 

Without Air Conditioning

Level III

Discretionary Uses

With Air Conditioning

Duration of Operation

90-Minute Minimum 

Duration Per NFPA 99 As Needed As Needed

Heating equipment (eg. 

boilers, fans, air handling units, 

pumps and controls)

  

Equipment Branch

(select areas)





(applies to all equipment

serving critical areas and 

operations)



(same scope as Level II)

EMCS (Environmental 

Management and Control 

Systems)

 

(as required for long term 

operations)



(same scope as Level II)

Computer equipment 

(provide UPS to supply critical 

systems during generator start 

up)



(same scope as Level II)

Network servers and routers 

(provide UPS to supply critical 

systems during generator start 

up)



(same scope as Level II)

Food preservation equipment 

refrigeration

 

(if required to maintain critical 

functions for on-site personnel)



(same scope as Level II)

Food preparation and service 

equipment

 

(if required to maintain critical 

functions for on-site personnel)



(same scope as Level II)

Intercom systems mobile phones should suffice 

for short term



(same scope as Level II)

Legend:

 Required for code minimum durations 

 Discretionary increase if continued operation of system is required for continued occupancy

 Discretionary increase, added at the indicated level

 Air conditioning systems to be provided with emergency power

4-10 4: Identifying Emergency Power Needs in Critical Facilities FEMA P-1019
Table 4-1 Elements Potentially Requiring Emergency Power (Continued)

Level IA

Basic IBC Requirements

Level IB 

NFPA 99 Requirement for 

Critical Healthcare Facilities

Level II

Discretionary Uses 

Without Air Conditioning

Level III

Discretionary Uses

With Air Conditioning

Duration of Operation

90-Minute Minimum 

Duration Per NFPA 99 As Needed As Needed

Central clock systems 

(if critical to facility function)



(same scope as Level II)

Radio communication 

equipment

 

(if critical to facility function)



(same scope as Level II)

Air conditioning systems 

(if required for long-term 

operations. Determine extent 

of facility to be airconditioned. See Section 4.3

for discussion of system 

choices)

Legend:

 Required for code minimum durations 

 Discretionary increase if continued operation of system is required for continued occupancy

 Discretionary increase, added at the indicated level

 Air conditioning systems to be provided with emergency power

FEMA P-1019 4: Identifying Emergency Power Needs in Critical Facilities 4-11
Figure 4-1 Life-safety equipment: fire alarm control panel (top) and exit 

signage (bottom).

4.3.2 Fire Pumps

Fire pumps or sprinkler system pumps boost water system pressures and 

ensure adequate water flow to sprinklers for fire suppression. Unlike most 

other electrical equipment, fire pumps, including the motors, electrical 

feeders, and pump controls, are exempted by NFPA 70, National Electrical 

Code (NFPA, 2014), from many of the code requirements protecting

electrical equipment from damage. The assumption is that, in the event of a 

fire, a fire pump must continue to operate until the fire is suppressed, even if 

it damages or destroys the pump and associated equipment. Having a fire 

pump shut down to protect itself may save the pump, but would increase 

risks to the occupants and the facility. Figure 4-2 shows a typical fire pump 

controller.

4-12 4: Identifying Emergency Power Needs in Critical Facilities FEMA P-1019
Figure 4-2 Typical fire pump controller.

4.3.2.1 Emergency Power Recommendations for Fire Pumps 

Although fire pumps are critical for protecting occupants, they are only 

rarely powered from emergency generators. A common arrangement is to 

power the fire pump “upstream of the main.” That is, the fire pump is 

connected to the electrical service equipment on the distribution line side of 

the main electrical service disconnect. This allows fire fighters to shut off 

power to a building in order to reduce potential for injury during manual fire 

suppression without sacrificing the fire suppression provided by the sprinkler 

system. When connected upstream of the main, fire pumps receive power 

from the electrical utility. If normal utility power is not available, the fire 

pumps cannot operate and the occupants are not fully protected. Because of 

this, fire pumps should be provided with emergency power.

NFPA 20, Standard for the Installation of Stationary Pumps for Fire 

Protection (NFPA, 2013d), only requires auxiliary power for the following 

two circumstances: (1) when the primary power supply is deemed unreliable; 

and (2) when pumps are located in high-rise buildings where the height of the 

building is above the pumping capabilities of the fire department apparatus. 

Although NFPA 20 does not require auxiliary power for every fire pump 

installation, it does require auxiliary power for fire pumps in critical facilities 

that must remain operational when the primary power supply is not reliable 

(i.e., not available when needed). 

Another component of a fire suppression system is a jockey pump (Figure 

4-3). Jockey pumps maintain sprinkler system pressures. In fire suppression 

FEMA P-1019 4: Identifying Emergency Power Needs in Critical Facilities 4-13 
systems that contain fire pumps, jockey pumps can prevent inadvertent 

operation of the fire pump itself. Jockey pumps are typically much smaller 

than fire pumps, often operating at only a fraction of a horsepower. Jockey 

pumps are only required to have backup power if they are installed in a

healthcare facility. In other facilities, they are not usually supplied by the 

emergency system. 

Figure 4-3 A typical jockey pump. 

4.3.3 Lighting

Code-required emergency lighting ensures that egress paths have the 

minimum amount of illumination needed to exit a building. Most codes 

specify an average initial illumination of 1 foot-candle (fc) with a minimum 

illumination of 0.1 fc at the end of the 90-minute duration. By comparison, 

office areas are typically illuminated to 50 to 100 fc and corridors at 15 fc. 

Egress lighting must be provided for more than 90 minutes if the facility is to 

be occupied. The level of lighting in the egress system may be fairly low, 

but that level will not be adequate for operational spaces.

4.3.3.1 Emergency Power Recommendations for Lighting 

For most facilities, lighting egress paths with a relatively low level of 

illumination is not adequate for operations during prolonged power outages. 

4-14 4: Identifying Emergency Power Needs in Critical Facilities FEMA P-1019
Illumination levels of 30 percent to 50 percent of the normal lighting levels 

are more likely to be appropriate for most areas to function at a base level. 

For areas where visual tasks are demanding, full lighting levels should be 

provided. 

4.3.4 Mechanical Equipment

Mechanical equipment heats and cools a building’s interior and also provides 

fresh air for ventilation. Nearly all heating and cooling equipment requires 

electrical power to operate, so an emergency power supply must be provided 

if heating and cooling may be needed during a prolonged utility power 

outage. Mechanical equipment described in this section includes heating, air 

conditioning, and electrical components of plumbing systems that provide 

water service and sanitary waste removal.

4.3.4.1 Heating 

In cold climates, heating is required for both occupant comfort and freeze 

protection. For occupant comfort, only critical areas need to be heated but 

for freeze protection, all areas vulnerable to freezing need to be heated. 

Minimum temperatures may also need to be maintained for piping systems 

that contain condensable gases. 

Emergency Power Recommendations for Heating

Emergency power should be provided to all heating equipment serving 

critical areas and operations whenever the heating equipment is needed to 

maintain adequate interior temperatures for occupant comfort or freeze 

protection. The following is a list of major heating system components that 

may need to be supplied from emergency power sources.

• Forced air systems: With forced air systems, emergency power needs to 

be supplied to the furnaces, distribution system, and where in use, supply 

and exhaust fans and the heating, ventilation, and air conditioning 

(HVAC) controls. 

• Hydronic systems: With hydronic systems, emergency power needs to be 

supplied to the boilers, circulating pumps, HVAC controls and, where 

used, supply and exhaust fans. Power may also need to be provided for 

fuel oil pumps and for equipment that chemically treats boiler make-up 

water.

• Combined systems: With combined hydronic and force air systems, 

emergency power is needed for the boilers, circulating pumps, air 

handling units, and HVAC controls. Emergency power to ventilation 

systems and make-up water systems may also be needed.

FEMA P-1019 4: Identifying Emergency Power Needs in Critical Facilities 4-15 
4.3.4.2 Air Conditioning

Air conditioning systems mechanically cool the interiors of buildings. Most 

air conditioning systems also dehumidify because when air is cooled below 

its dew point, condensation forms on cooling coils and removes water vapor 

from the conditioned air. 

Air conditioning is provided by forced air systems where supply air is cooled 

and distributed to the conditioned areas and warmer air is returned to the air 

conditioning units to be re-cooled and dehumidified. There are two common 

systems, described below. 

DX systems consist of two components: (1) an interior evaporator coil and 

fan unit; and (2) an exterior compressor and condensing unit. In DX 

systems, refrigerants undergo a reversible phase change (condensation and 

evaporation) and the heat required for evaporation is drawn is from the 

interior of a building and released to the exterior when the refrigerant 

condenses. Figure 4-4 shows roof mounted DX units that provide airconditioning to a school. 

In chilled water systems, water is cooled and circulated through air handling 

units where it absorbs heat from interior spaces. Slightly warmer chilled 

water often is returned to be re-chilled. Several styles of chillers exist. Most 

contain compressors and condensers and use a refrigerant cycle (like DX 

units) where the refrigerant goes through a phase change between vapor and 

liquid, and in doing so transfers heat to the refrigerant from the chilled water. 

Heat is removed from the chiller condensers by air cooling or by evaporating 

water in cooling towers. Pumps circulate chilled water from the chiller unit 

to the air handlers and returns the warmer water for re-cooling.

Figure 4-5 shows two major components of a chilled water air conditioning 

system that uses a cooling tower. Figure 4-6 shows an integral air-cooled 

chiller unit that does not require a cooling tower.

Emergency Power Recommendations for Air Conditioning

Air conditioning systems require a lot of electricity to operate, and when 

added to emergency power systems, these loads significantly increase the 

required generator capacity. Because of this, adding air conditioning loads to 

an emergency power system should be done judiciously. No more air 

conditioning loads than what are truly needed for operations should be 

connected to an emergency power source. 

Air conditioning may be required for occupant comfort, humidity control, 

and equipment protection, particularly temperature sensitive electronic 

4-16 4: Identifying Emergency Power Needs in Critical Facilities FEMA P-1019
equipment. Air conditioning may also be needed to protect stored 

temperature sensitive materials like many pharmaceuticals. 

Figure 4-4 Roof-top mounted DX HVAC units.

Figure 4-5 Water-cooled chiller (left) with cooling tower (right).

For a DX system to function, power is required to supply the interior 

evaporator coil and fan unit, the exterior compressor and condensing unit, 

and all control equipment. In a DX system, the exterior unit draws the 

majority of the system’s total electrical load. The interior unit, which 

contains distribution fan(s), draws much less power. 

FEMA P-1019 4: Identifying Emergency Power Needs in Critical Facilities 4-17
Figure 4-6 Air-cooled chiller.

For a chilled water system to function, the power is required to supply the 

interior air handling units, chilled water circulating pumps, chillers, control 

equipment, and where used, evaporative cooling tower pumps and fans. 

4.3.4.3 Plumbing Systems

The electrical load requirements for plumbing systems are generally less than 

other mechanical systems. However, if emergency power is not provided, 

plumbing systems may not operate during a prolonged power outage. 

Many facilities that are built below grade have sump pumps to prevent site 

water from seeping into below-grade areas. Those pumps can range from 

only a fraction of a horsepower to about 5 horsepower. Figure 4-7 shows a 

below-grade sump. The sump pump is located within the sump.

Sanitary lift pumps are needed when the municipal sanitary sewer lines are at 

a higher elevation than the building’s sanitary sewer piping. While lift 

pumps are normally placed in sumps that have some storage capacity, the 

storage capacity is usually limited.

For taller buildings where water service pressure is not sufficient to lift water 

to upper floors, domestic water booster pumps are often used. Figure 4-8 

shows a typical domestic water booster pump station.

Commercial domestic hot water systems often have a circulator pump to 

prevent hot water from cooling in the piping when hot water usage is low. 

Those pumps are typically driven by small motors that do not add significant 

4-18 4: Identifying Emergency Power Needs in Critical Facilities FEMA P-1019
loads. The blue pumps in Figure 4-9 are circulator pumps for a domestic hot

water system.

Figure 4-7 Sump cover; pump is within the sump.

Figure 4-8 Domestic water booster pumps.

Emergency Power Recommendations for Plumbing Systems

Pumps associated with plumbing systems do not typically add significant 

loads to an emergency power source, but not providing emergency power to 

them can reduce the functionality of a critical facility that is without power 

for a significant period of time. 

FEMA P-1019 4: Identifying Emergency Power Needs in Critical Facilities 4-19
Figure 4-9 Domestic hot water circulator pumps.

Sump pumps do not add significant loads to an emergency power source and 

should be supplied with emergency power to prevent flooding in belowgrade areas. 

Since the storage capacity associated with sanitary lift pumps is usually 

limited, the pumps must receive emergency power if a facility needs to 

operate during power outages that extend a few hours or more.

If upper floors will be occupied during extended power outages, booster 

pumps should be supplied by emergency sources to retain water pressure on 

upper floors. Water pressures on lower floors are less vulnerable to pressure 

loss than are fixtures on higher floors. 

Although domestic water systems will still operate during power outages, hot 

water may be wasted while users of the system wait for cooled water to work 

its way through hot water piping unless the circulator pumps are supplied 

with emergency power. Circulator pumps require relatively little power to 

operate and should be supplied when emergency power is provided. 

4.3.4.4 Food Preparation and Preservation

For critical facilities that must prepare food for occupants, food preparation 

equipment must be provided with emergency power. Unless the power 

outages are of short duration, food preservation equipment must also be 

provided with emergency power. Figures 4-10 and 4-11 show food 

preparation and preservation equipment for a typical commercial kitchen.

4-20 4: Identifying Emergency Power Needs in Critical Facilities FEMA P-1019
Figure 4-10 Commercial kitchen for critical facility that provides food for 

occupants.

Emergency Power Recommendations for Food Preparation and 

Preservation

Electrical requirements for food preparation vary greatly. “All electric” 

kitchens require more electrical power than kitchens where cooking 

equipment operates on natural gas or liquid propane. Even with gas-fired 

kitchens, power is needed for igniters, gas solenoid valves, and controls. 

Food preservation equipment, such as walk-in freezers, walk-in refrigerators, 

and smaller chest or upright refrigerators and freezers need emergency power 

to maintain temperatures during a prolonged power outage. 

Even with all-electric kitchens, the total power requirements for food 

preparation and preservation are typically a lot less than power requirements 

for building heat and certainly less than for air conditioning. Power 

requirements for kitchens are typically easy to accommodate by using 

generators sized to supply mechanical systems.

4.3.5 Other Building Systems

The following list identifies other building systems that may need to operate 

if the facility is to be used during a prolonged power outage:

• ECMS (Environmental Control and Management Systems)

• Telephone equipment

• Network servers and routers

• Computer equipment

FEMA P-1019 4: Identifying Emergency Power Needs in Critical Facilities 4-21 
Figure 4-11 Large commercial refrigerator and freezer in commercial 

kitchen.

• Intercom systems

• Central clock systems

• Radio and telephone communication equipment

• Mechanical alarm systems (like sump or lift pump monitoring 

equipment)

• Elevators and conveyance systems

• Medical equipment in health care facilities (detailed information is 

provided in Appendix A)

4-22 4: Identifying Emergency Power Needs in Critical Facilities FEMA P-1019
Chapter 5

Emergency Power Sources and 

Systems 

This chapter provides an overview of the elements of common emergency 

power generation systems. Power sources are devices that create (or store) 

electricity and ancillary equipment needed for power production or storage. 

The sources include generators, fuel supplies, stored energy devices, and 

controls for operating them. Power distribution systems deliver power from 

the power source to the critical equipment. The distribution system consists 

of switchgear or switchboards, feeders, distribution panels, panelboards, 

protective devices, and transfer switches. Many aspects of an emergency 

power distribution system are similar to normal power distribution systems. 

The difference is that emergency power distribution systems can receive 

power from either the normal power source or from an emergency power 

source. 

Many factors come into play for an emergency power system to function for 

a sustained periods. Therefore, a holistic approach, as discussed in Chapter 6

to the entire system is needed to ensure emergency power is functional and 

reliably available when needed. 

5.1 Emergency Power Sources

In general, critical facilities employ two common methods of providing 

emergency power: (1) stored energy devices, such as battery and inverter 

systems; and (2) standby/emergency generators. Nearly all non-residential 

facilities possess some stored energy devices (typically those for emergency 

and egress lighting) and many facilities have both stored energy devices and 

emergency generators. 

Both methods of supplying emergency power must be properly sized, 

properly installed, and properly maintained to be reliable and effective. Fuelfired generators must be supplied with appropriate fuel from a reliable 

source. 

5.1.1 Stored Energy Devices 

Stored energy devices are frequently used to provide short-duration 

emergency power. When used alone, they often are sized to supply loads for 

FEMA P-1019 5: Emergency Power Sources and Systems 5-1 
90 minutes, the duration required by NFPA 101, Life Safety Code (NFPA, 

2012b), which allows safe egress from the facility for many occupancies. 

When used in conjunction with standby or emergency generators, stored 

energy systems are often used to supply power only during the time required 

to start an emergency or standby generator, stabilize its operation, and 

transfer critical load to the generator. 

5.1.1.1 Battery-Powered Systems

Battery systems are the most common short-duration emergency power 

supply systems. They typically provide emergency power for approximately 

5 minutes (when used with standby generators) to 2 hours when required to 

supply life-safety loads without a generator. However, some facilities, such 

as telephone company central offices and data centers, have battery systems 

designed to power communications equipment for longer periods, often 24 

hours or more. The most common type of battery-powered emergency 

systems is the uninterruptible power supply (UPS) system. 

UPS systems provide continuous (uninterruptible) power and are typically 

used to supply critical equipment that can be adversely affected by even 

momentary power outages. UPS systems are typically used in computer 

rooms, data centers, mission-critical medical centers, emergency operation 

centers (EOC), and similar facilities. They are generally sized to provide

power long enough either to allow an orderly shut-down of electronic 

equipment or for an onsite emergency generator to sense the loss of utility 

power, start the generator’s prime mover, allow the prime mover to achieve 

operating speed, and allow the generator’s automatic controls to transfer 

critical loads to the generator. For medical facilities, NFPA 99, Health Care 

Facilities Code (NFPA, 2012a), specifies the maximum allowable time to 

transfer power to an emergency power supply and UPS systems are often 

designed to provide power for that duration.

UPS systems contain batteries, a battery charger, and an inverter that 

converts the direct current (DC) supplied by batteries into alternating current 

(AC). UPS systems may also have by-pass features that allow them to be 

tested and maintained without taking them out of service. While utility 

power is supplied to the building, the UPS battery charger maintains the UPS 

battery in a fully charged state. When utility power is lost, the UPS draws 

power from the batteries to supply the critical loads. Figure 5-1 shows 

typical equipment found in a medium-sized UPS system.

5-2 5: Emergency Power Sources and Systems FEMA P-1019
Figure 5-1 UPS system containing an inverter (left) and battery rack (right)

located in a low seismic area. 

5.1.1.2 Flywheel Systems

Flywheel systems are short-duration power supplies that provide emergency 

power for a duration of 1 minute or less, sufficient to allow emergency 

generators to start, stabilize, and transfer loads (typically 10 seconds). 

Flywheel systems are good alternatives to battery systems because of their 

simple design, small size, and limited maintenance requirements. Figure 5-2 

shows one type of flywheel system.

The flywheel system stores energy in the inertia of a rotating mass. The 

major system components are a motor that can function as a generator 

directly attached to a heavy flywheel and the flywheel itself. While power is 

supplied to the system, the motor drives the heavy flywheel. When power is 

lost, the inertia forces allow the flywheel to continue to rotate and the motor 

instantaneously begins to function as a generator. The inertia of the heavy 

flywheel keeps the generator spinning at nearly the same speed for 20 

seconds or more. 

5.1.2 Emergency and Standby Generators

Emergency and standby generators serve a wide range of applications. Small 

facilities with immediate but infrequent generation needs may employ a

single generator with manual start and manual power transfer control 

scheme. Larger critical facilities may employ complex systems utilizing

FEMA P-1019 5: Emergency Power Sources and Systems 5-3 
Figure 5-2 Rendering of flywheel system.

parallel generator installations, complex generator control, automatic transfer 

switches, and sophisticated power monitoring. 

Generators are available in a wide range of sizes, with ratings from 1 

kilowatt to several megawatts. They can operate almost indefinitely when 

properly sized, installed, maintained, and supplied from reliable fuel sources. 

5.1.2.1 Generators and Engines

Emergency generators consist of an engine (often called a prime mover), a 

synchronous generator, monitoring equipment, and controls. The prime 

mover provides mechanical power to the generator; for units 1 megawatt and 

below they are typically piston driven; larger units may be turbines. The 

synchronous generator converts the mechanical power into alternating 

current; the monitoring equipment senses the state of the generator (primarily 

its speed); and the controls adjust fuel flow to match the prime mover power 

output with the power drawn from the generator. The generator also senses

generator output voltage and adjusts the generator’s output for voltage 

control. 

Generators require cooling to remove heat created by the prime mover and 

the generator and ventilation for the combustion air required by the prime 

mover. Usually, the combustion air also helps cool the equipment. In 

5-4 5: Emergency Power Sources and Systems FEMA P-1019
addition, emergency generators require equipment (typically lead-cell 

batteries) to start the prime mover. Battery chargers are integral to the total 

system to ensure starting capability is maintained. 

Generators can be installed either within the facility or in exterior enclosures

(Figure 5-3). When placed outside, generators are more exposed to damage 

from natural hazards. The natural hazards (wind, flood, and earthquake) that 

most often damage generators are described in Chapter 2. Chapters 6 and 7 

contain guidance on how to protect generators from those hazards in new and 

existing facilities.

Figure 5-3 Emergency generator installed on the interior (left) and exterior (right).

When generators are located outside, they are typically placed in an 

enclosure to protect the generator and its controls from weather. Some 

enclosures allow generators to be heated; this feature improves the ability of 

the fuel-fired unit to start in cold weather. Some enclosures also provide 

sound attenuation to reduce the noise emitted from an operating generator 

(Figure 5-4). Facility operators should also be cognizant of restrictions on 

diesel exhaust emissions when planning generator locations in urban areas. 

Local ordinances sometimes require up blast fans or other exhaust 

disbursement mitigation.

5.1.2.2 Fuel Selection and Delivery 

The vast majority of emergency and standby generators operate on fossil 

fuels. Fuel delivery systems are critical to the reliability of fuel-fired 

generators. Selecting the proper fuel source is important, and many factors 

play into that decision, including generator consumption rates, the 

availability of fuels and the ability to replenish the fuel supply after a natural 

hazard that blocks roads or disrupts infrastructure. Fuel sources for 

generators are either liquid (gasoline or diesel) or gas (propane or natural

gas). Most generators under 15 kW are fueled by gasoline, propane, or

FEMA P-1019 5: Emergency Power Sources and Systems 5-5
Figure 5-4 Exterior emergency generator placed in a sound-attenuating 

enclosure.

natural gas. Generators over 15 kW can also be fueled by diesel while those 

over 300 kW are almost exclusively fueled by diesel. 

Fuel can be either stored onsite or delivered from offsite. Onsite fuels 

include gasoline, diesel fuel, No. 2 fuel, and propane. For onsite storage, 

provisions for refueling are critical, particularly immediately after an event. 

It is also critical that the fuel tanks, fuel pumps, and fuel lines be protected 

from natural hazards. Guidance for protection is provided in Chapter 6. Fuel 

sources must be reliable to ensure they are available when generators need to 

operate. Municipal or utility fuel sources are commonly shut off in 

preparation for an oncoming hazard event (most notably floods or 

hurricanes) to reduce the risk of fire and explosion. If a generator receives 

fuel only from a source that may be interrupted, the fuel source is not 

considered reliable. For generators used for life-safety protection, NFPA 

110, Standard for Emergency and Standby Power Systems (NFPA, 2013c),

requires an onsite fuel supply that is not solely dependent on a public utility.

NFPA 110 requires enough onsite fuel to operate the emergency power 

systems at full load for between 5 minutes and 48 hours depending on the 

facility’s use, location, and the equipment served; a minimum of 90 minutes

is typically required for most installations to support emergency egress. In 

high seismicity areas for critical facilities, NFPA 110 requires 96 hours of 

onsite fuel storage to address the risk of widespread damage to infrastructure. 

FEMA 543, Design Guide for Improving Critical Facility Safety from 

Flooding and High Winds: Providing Protection to People and Buildings

(FEMA, 2007), and Guidelines for Design and Construction of Healthcare 

Facilities (FGI, 2014) also recommend that generators be able to run 96 

hours without refueling.

5-6 5: Emergency Power Sources and Systems FEMA P-1019
Diesel

Diesel, nearly the same as fuel No. 2, with its low vapor pressure and high 

ignition temperature, is less volatile than gasoline and propane, and it can be 

stored longer than gasoline without deteriorating. Diesel fuel also has a high 

energy content (approximately 145,000 BTUs/gallon) and is readily available 

in most areas. However, diesel fuel eventually degrades over time, and this 

degradation can severely affect generator operation and reliability. If too 

much fuel is stored onsite, fuel inventories can become stagnant and degrade

if not used. 

Fuel degradation is a complex problem, and providing comprehensive 

recommendations on preventing degradation is beyond the scope of this 

document. However, the following are general recommendations for owners 

and operators:

• Supply emergency generators from fuel tanks that serve other fuel 

burning devices (like boilers) to benefit from more constant fuel use.

• Test fuel frequently to identify fuel quality, and replace fuel when the 

quality degrades to unacceptable levels.

• Provide parallel fuel filters that will allow clogged filters to be quickly 

by-passed while maintaining constant fuel filtration.

• Provide polishing systems to circulate and clean fuel of biologic growth 

that can foul filters.

• Avoid oversizing fuel tanks, particularly those that supply only 

generators that run occasionally.

• Be aware of the problems with fuel degradation and maintain vigilance 

to prevent fuel degradation from affecting system reliability.

Supplying diesel generators from shared fuel tanks is a good method to

reduce the risk of fuel degradation because heating fuels are cycled more 

frequently. Diesel engines can operate on No. 2 fuel oil, which is a common 

fuel for many boilers. When emergency generators are supplied from shared 

fuel tanks, provisions must be put into place to ensure fuel inventories do not 

fall below critical levels. Figure 5-5 shows a large shared fuel oil storage 

tank.

Propane

Propane can be stored indefinitely, but is highly volatile. The risks 

associated with its volatility can be reduced with proper installation and 

routine testing and maintenance. Unless site limitations prevent placing 

FEMA P-1019 5: Emergency Power Sources and Systems 5-7
sufficiently large tanks onsite, adequate quantities of fuel can generally be 

stored onsite.

Figure 5-5 Fuel oil storage tank used for heating equipment that can supply an emergency 

diesel generator.

Natural Gas

Natural gas, unlike propane and diesel, is not stored on site but rather piped 

to a site from a local utility. Natural gas supplies can be interrupted during 

high-wind, flood, or earthquake events. Also, natural gas services are often 

intentionally shut down prior to a storm event to reduce the risk of fires and 

explosions. Because of this, natural gas should not be used as a fuel for 

providing emergency power to critical facilities unless the facility can 

confirm that natural gas service will not be interrupted.

5.1.2.3 Generator Synchronizing 

When multiple generators are employed in a system, each generator must be 

synchronized before it is connected to the power system. The frequency, 

phase angle, and voltage of the generator being brought on-line must be 

closely matched to the system before closing the generator breaker. 

Generator synchronizing boards (GSBs) automatically control the starting, 

stopping and synchronizing of generators. Modern GSBs are often equipped 

with data acquisition features as well as programmable parameters that allow 

demand control, load shedding, and alarm notifications. Strategies on 

5-8 5: Emergency Power Sources and Systems FEMA P-1019
redundancy of systems can be supported with modern synchronization board 

controls. Appendix B discusses redundancy strategies. Figure 5-6 shows 

multiple generators supplying emergency or standby power. Figure 5-7 

shows the GSB that synchronizes the generators and provides load shedding 

and demand control.

Figure 5-6 Multiple generators in parallel.

5.1.2.4 Load Shedding

Load shedding is a controlled response to excessive electrical demand, that 

ensures that the most critical equipment receive emergency power. Loads 

supplied from the emergency power system are assigned a priority and shed 

based on that priority. Lower priority loads (e.g., mechanical cooling) are 

shed first and then more critical loads (e.g., specialty equipment) are shed 

only if needed. Life-safety loads are given the highest priority and are not 

available to be shed. With sophisticated controls, the GSB monitors total 

generator production capacity and automatically sheds least critical loads to 

match generator output. In this way, the loss or curtailment of any generator 

only impacts the least critical loads. 

5.1.2.5 Battery Starting Systems

Battery starting system for a generator is an often overlooked but critical 

component of the total system. The single most frequent reason for generator 

failure to start is its battery system. Battery systems should be installed in 

conditioned space to avoid extreme temperatures. Proper design and

FEMA P-1019 5: Emergency Power Sources and Systems 5-9
Figure 5-7 Generator synchronizing board.

installation of interconnecting cables can compensate for voltage drop. 

Routine maintenance should verify proper charging and that cable 

connections remain tight and corrosion free. Frequently battery failure is due 

to an inoperable charger caused by an open breaker left off during routine 

maintenance. Care should be taken by maintenance personnel to check all 

automatic settings and connections after each preventive maintenance check.

5.2 Emergency Power Distribution

The emergency power distribution system includes all wiring and equipment 

between the emergency or alternate power sources and the critical equipment 

the sources supply. Similar to the normal power distribution system, 

emergency distribution systems consist of switchboards or distribution 

panels, feeders, branch circuit panelboards, and branch circuits and devices 

downstream of overcurrent protection. Unlike normal power distribution 

systems, emergency power systems are fed from both normal and emergency 

power sources. The transfer from normal to emergency power system is 

completed through transfer switches, which may be automatic or manual. 

Upon sensing normal power loss, an automatic transfer switch (ATS)

automatically sends a start signal to the generator and monitors power 

quality. When the generator produces power within acceptable voltage and 

frequency limits (i.e., the generator has stabilized enough to accept electrical 

loads), the ATS automatically switches from the normal to the emergency 

5-10 5: Emergency Power Sources and Systems FEMA P-1019
power source. The ATS then continuously monitors normal power and 

automatically re-transfers back to the normal source when utility power has 

been restored and stabilized. Typically, the transfer back to normal power is 

delayed to help prevent nuisance or premature transfers. 

Manual transfer switches (MTS) are similar but need to be operated 

manually. Also, manual transfer switches lack the generator start controls of 

an ATS. 

NFPA 99 Health Care Facilities Code defines three branches within an 

emergency distribution system: (1) equipment branch; (2) critical branch; and 

(3) life-safety branch. The life-safety branch is the most important and given 

the highest priority. As the name implies, the life-safety branch is reserved 

for loads, such as exit lights and emergency lights required by NFPA 101 

Life Safety Code. Fire detection and signaling devices complying with 

NFPA 72 National Fire Alarm and Signaling Code (NFPA, 2013a) can also 

be supplied from the life-safety branch as can hospital communication 

systems, systems that support the generator and elevator controls and 

elevator cab illumination. No other loads can be supplied from the life safety 

branch. NPFA requires the generator to start, stabilize, and transfer to 

energize loads on the life-safety branch in less than 10 seconds. 

NFPA 99 Health Care Facilities Code requirements for the critical branch 

and the equipment branch are less restrictive than those for the life-safety 

branch. Manual control and load shedding are allowed on selected 

equipment branches and more time is allowed for energizing those branches. 

NFPA 70 National Electrical Code also contains requirements for emergency 

systems. Article 700, Emergency Systems, defines three distinct 

classifications of emergency power systems: (1) emergency systems; (2)

legally required standby systems; and (3) optional standby systems. Of 

these, emergency systems are for “the safety of human life” and are 

consistent with the loads specified by the NFPA 101 Life Safety Code and the 

life safety branch of NFPA 99 Health Care Facilities Code. The second

classification, legally required standby system, supplies loads other than life 

safety loads that are required by municipal, state, federal, or other codes, or 

by governmental agencies having jurisdiction. The informational note of 

NFPA 70 states that legally required standby systems could create hazards or 

hamper rescue or firefighting operations if their functionality is interrupted. 

One example of a legally required standby system is a smoke control system. 

Optional standby systems are systems that provide power to equipment that, 

if interrupted, could cause discomfort, serious process interruptions, or 

product damage. Many of the systems required for a critical facility to 

At the time of this writing, 

pending updates to NFPA 

99, 2015 edition, NFPA 

101, 2015 edition, and 

regulations from Centers for 

Medicare / Medicaid 

Services (CMS) are under 

consideration that may 

increase best practice 

recommendations for the 

health care environment.

FEMA P-1019 5: Emergency Power Sources and Systems 5-11
function following an event fall into the category of optional standby 

systems.

NFPA 70 National Electrical Code requires wiring within emergency 

systems to be separate from all other wiring and prohibits (with listed 

specific exceptions) emergency system wiring from sharing raceways, 

cables, boxes, and cabinets with general wiring. NFPA 70 also limits what 

loads can be placed on emergency systems. In addition, recent editions of 

the NFPA 70 also require emergency system wiring to be routed through 

areas that are fully protected by sprinkler systems or provided with 2-hour 

fire protection. Article 700 of NFPA 70 also requires protective devices in 

emergency systems be coordinated to ensure that the minimum amount of 

equipment is affected when overcurrent devices, such as circuit breakers 

operate to isolate electrical faults. 

Wiring for legally required standby systems and optional standby systems 

can share raceways, cables, boxes, and cabinets with general wiring. 

5.3 Optional Standby Generators

Many smaller critical facilities find the capital cost of permanently installed 

generator redundancy prohibitive. An alternative to providing full 

redundancy for emergency power is to install means for rapidly connecting a 

temporary generator. Installing these connections, often called quick 

connects, and using temporary generators offer several advantages over 

permanently installed redundant systems. Temporary generators do not 

require large capital expenditures and do not require facility owners to 

continually maintain and test the units. Routine maintenance requirements 

can be shifted to unit supplier or contract vendor. However, temporary 

generators require significant advance planning to ensure that they will be 

available when needed and provisions that allow them to be safely connected 

to the facility’s electrical system. 

The following sections describe the preparations that must be made before a 

temporary generator can power a critical facility. 

5.3.1 Providing Reliable Vehicle Access 

In order to place a temporary generator into service, vehicular access to the 

temporary generator location must be available. If the generator is delivered 

after the event, at least one access route must be clear of fallen trees, not 

blocked by debris or other obstructions, and not rendered inaccessible by 

floodwaters. Temporary generators are heavy (for example a 100 kW unit 

weighs approximately 10,000 pounds), and paved roads or gravel road beds 

5-12 5: Emergency Power Sources and Systems FEMA P-1019 
may need to be constructed to support the heavy equipment used to transport 

generators to the site and to support trailer-mounted generators after they are 

delivered to the site. 

5.3.2 Creating a Location 

The generator location is usually controlled by the need to access the 

electrical service and distribution equipment. The temporary generator must 

be located reasonably close to where it will be electrically connected to the 

facility. Cables are used to connect the generator to the facility, and long 

cable runs create an undesirable voltage drop that can damage equipment. 

For long runs, oversized cables can be used or additional cables can be 

installed to reduce voltage drop, but those options are relatively expensive. 

Concrete slabs can be placed to support generators, or designated parking 

areas can be assigned to site the trailers. When siting a temporary generator, 

facilities should make sure the temporary unit can be refueled while on site. 

In addition, when possible, temporary generators should be placed where 

their operating noise will not be objectionable.

5.3.3 Installing Connections 

When preparing to connect the generator, the types of cables that will be 

used for the connection, as well as where it will be electrically connected, 

should be connected. 

Flexible cables are normally used to connect the temporary generator to a 

facility. For smaller installations (approximately 15 kW single-phase or 25 

kW three-phase), a multi-conductor cable that terminates in a twist-lock 

receptacle is often used. The receptacle can connect to a mating plug 

mounted on the building. Figure 5-8 shows two styles of building-mounted 

twist-lock plugs for connecting temporary generators. For larger generators, 

single conductor cables that terminate in slip-fit plugs and matching 

receptacles are typically used. Conductors can be installed in parallel to meet 

the amount of current drawn by the building. Figure 5-9 shows two 

installations of slip-fit devices. To prevent injury or death, the method used 

to connect the must prevent any power from being back-fed onto utility lines.

FEMA P-1019 5: Emergency Power Sources and Systems 5-13 
Figure 5-8 Building-mounted twist-lock plugs for connecting temporary generator cables. 

 

Figure 5-9 Electrical connection point for temporary generator using slip-fit connectors (left), and cables 

at building connection (right). 

5.3.4 Ensuring Availability 

To ensure generators are available when needed, facility operators should 

establish contracts with equipment rental agencies before an event strikes. 

Agreements may also be developed between neighboring municipalities or 

State agencies. For larger municipalities that have several similar facilities 

(such as fire stations, police stations, or water or wastewater pumping 

stations), a single generator could be purchased and used to serve standby 

power for several sites provided concurrent use is not required. 

5.4 Electrical Control and Coordination

When electrical systems are properly designed, properly installed, and free 

from failures or damages, they can safely distribute large amounts of power. 

That power can range from 1,000 watts for an individual branch circuit 

supplying a piece of electrical equipment to 100 kilowatts for an electrical 

5-14 5: Emergency Power Sources and Systems FEMA P-1019 
feeder in a commercial building or industrial plant to 1 megawatt for a 

distribution line circuit supplying a small community to several 100 

megawatts for transmission lines supplying an entire city or a large 

geographic area. However, the beneficial power that electrical systems can 

distribute can rapidly become destructive when failures occur either within 

those systems or when they are damaged by external forces. 

5.4.1 System Protection and Control

Electricity is distributed at essentially the speed of light and therefore the 

power systems that distribute potentially damaging energy must include 

automatic protective devices fully integrated into the system. Those 

protective devices must detect anomalies within the system often in fractions 

of a microsecond and initiate automatic protective actions in order to: (1) 

eliminate or minimize damage to both the power source and the downstream 

equipment; and (2) isolate the damaged elements of the system to minimize 

the loss of electrical power. 

Power system controls can be automatic or manual and are custom designed 

for each facility to configure the power system to accommodate the code 

requirements and specific performance goals of the owner. Control systems 

can monitor the actions of protective systems but are not allowed to interfere 

with the protective actions. The actions of the protective systems are then 

incorporated into how the control system may respond. A code required 

example is the automatic detection of the loss of utility power by the 

emergency generator controls. The protective system initiates the isolation 

of the facility power system from the utility, starts the generator(s) and 

transfers the source of facility power to the generator(s). 

Significantly more complex power control systems may be capable of 

connecting a facility’s generators to its power system for parallel connection 

to the utility source. In this co-generation mode, facility power is supplied 

by both the facility generators and outside utility. The seamless transfer is 

made possible by custom generator controls continuously sensing utility and 

generator parameters, such as voltage, frequency, and power factor, to 

automatically adjust the generator output to be synchronized with the utility 

before connection is allowed. If the proper control action cannot be 

achieved, the protective functions of the generator switchgear act to prohibit 

the paralleling of the generator to the utility source. 

Each facility may employ one or more protection schemes with varying 

degrees of complexity to meet the goals of functionality for the institution as 

FEMA P-1019 5: Emergency Power Sources and Systems 5-15 
a whole. These emergency power and normal power protection controls 

must be carefully coordinated to ensure proper operation.

5.4.2 Selectivity and Coordination

The term selective coordination refers to the selection and setting of

protective devices in an electric power system in such a manner to ensure the 

smallest possible portion of the system is deenergized by an abnormal

condition.

If faulty equipment with an internal short circuit in its internal power wiring 

is plugged into an outlet in a critical facility, the expectation would be that 

the branch circuit breaker feeding the outlet would immediately trip and 

prevent the building wiring to the outlet from overheating and failing. If 

instead, the main circuit breaker controlling the power for the entire facility 

opens before the individual branch circuit, all power downstream of the main 

circuit breaker would be lost and the entire facility could go dark. In a 

properly designed, installed, and maintained building electrical power 

system, the protective circuit breaker closest to the fault, or short circuit, 

senses the problem and acts to open the power circuit at the lowest possible 

level. When this outcome is achieved, the power system is providing the 

maximum possible selectivity and coordination. 

Modern electrical codes contain requirements for selectivity and coordination 

of normal power systems that should also be applied to emergency power 

systems. Design decisions made during the collaborative process between 

facility owners and the engineering team should not sacrifice selectivity and 

coordination.

5-16 5: Emergency Power Sources and Systems FEMA P-1019 
Chapter 6

Design Considerations for 

Emergency Power Systems in

New Facilities

Appropriate planning during the design of a new facility can greatly improve 

the ability to provide emergency power for that facility following severe 

natural hazard events when the facility is needed most. If proper 

considerations are made, what may be extremely difficult to achieve in 

existing construction can readily be achieved with a new facility. The keys 

to a successful design are the following: (1) getting all design professionals

and the building owners and operators to take a holistic approach to the 

design process; and (2) having the design team work closely with the owner 

or operator of the facility to identify all critical operations that must remain 

functional when utility power is lost. 

In this chapter, considerations and best practices for design of emergency 

power systems in new critical facilities are provided. These include 

determination of functions that require emergency power, decisions that 

affect the demand load for emergency power systems, and strategic decisions 

on the layout and locations of emergency power systems. Although it is 

easier to implement these recommendations in new facilities, the procedures 

discussed in this chapter are also applicable to the design of emergency and 

standby power systems in existing buildings. Finally, specific minimum 

code requirements applicable to emergency power systems are discussed 

along with best practices that go beyond those code minimums so that critical 

facilities will be better able to resist severe natural hazards and keep 

functioning when needed.

Best practices are presented to aid architects and engineers in developing 

effective designs for electrical systems in facilities that must remain 

operational during a prolonged power outage, when the facility site and 

surrounding area are subjected to severe natural events. While best practices

aim to create cost-effective electrical designs, the recommendations also 

influence architectural, civil, electrical, and mechanical engineering 

disciplines. Involvement from all design professionals is critical. 

FEMA P-1019 6: Design Considerations for Emergency Power 6-1

Systems in New Facilities
6.1 Holistic Approach to Design

Whether designing a new building’s emergency power system, adding 

capacity to an existing system, or simply analyzing an existing system, a 

holistic approach considers all aspects of the emergency power system 

design, installation and operation, along with the essential building systems it 

will be serving. This means a systems point of view must be taken at the 

start of the design and carried all the way through construction. 

The functionality of an emergency power system (and thus the critical 

facility) will only be as strong and reliable as its weakest link. If a holistic 

approach is taken, the system will be properly sized, designed, constructed 

and maintained. It has been observed that too often, each component supplier 

in the job optimizes each of their individual subtotals at the expense of an 

optimized total. Many mistakes can be avoided by having one engineering 

firm or project manager oversee the entire endeavor. A comprehensive view 

of the total system will generally provide improved results.

6.1.1 Determining Emergency Power Load Requirements

When planning or analyzing the needs of an emergency power system, one of 

the most difficult engineering tasks is to properly identify the required loads 

that must be powered when normal power fails. Facility managers should 

not underestimate the planning required to thoroughly identify equipment 

and their associated controls to be supplied by the emergency power system. 

Most codes simply mandate life-safety components only. NFPA 99, Health 

Care Facilities Code (NFPA, 2012a), provides additional requirements for 

health care critical facilities beyond the basic requirements of the 2012 

International Building Code (IBC; ICC, 2012), listing specific equipment 

that must be on emergency power, as well as required branch circuitry. 

NFPA 99 mandates emergency power for “selected” HVAC equipment only, 

e.g., in the emergency, intensive care unit, labor and delivery departments. 

Care must be taken in utilizing these documents to create the intended result, 

as code minimums will generally not achieve institutional goals. For 

example, an institution may choose to operate a catheterization lab on the 

emergency power equipment branch in accordance with NFPA 99; however, 

without proper cooling for patients and control rooms, the emergency 

powered catheterization lab may be rendered non-functional. 

A second example is a pharmacy. NFPA 99 specifies that in hospitals 

pharmacy task illumination and selected receptacles should receive 

emergency power from the critical branch. However, the code is silent on 

HVAC for pharmacy locations. Many pharmaceuticals must be stored within 

6-2 6: Design Considerations for Emergency Power FEMA P-1019

Systems in New Facilities
 

narrow temperature limits that may not be maintained when only codeminimum emergency power is provided. Accordingly, health care 

institutions should evaluate the pharmacology operations expected and the 

temperature ranges required for the pharmaceuticals to determine if HVAC 

in pharmacies should actually be required to meet the overall planned 

mission of the institution, regardless of what is specified by codes and 

standards. 

6.1.2 Emergency Power System Design

After the emergency power load requirements have been determined, the 

entire system must be planned with the overall institutional goals in mind. 

Individual mechanical, electrical, and plumbing equipment, conveyance 

equipment (e.g., elevators, escalators, and lifts), and other critical equipment 

should be considered as individual components in a heavily interconnected 

system. The vulnerability of any one piece of critical equipment can affect 

the performance of the entire system and the adverse effects of that system 

can affect other systems. For a critical system to function, often all 

components of that system must function, as well as those of other 

interconnected systems. 

Emergency power systems are a prime example of the interdependence of the 

overall system to its components and to other systems. For an emergency 

power system to operate and supply power to essential equipment, all 

components of the emergency power system must be undamaged and able to 

function. This includes: the emergency power source and all of its ancillary 

equipment (equipment to start and regulate the prime mover, lubrication and 

cooling equipment); the emergency power distribution system (distribution 

panels or switchboards, branch circuit panel boards and the feeders and 

branch circuits that interconnect them), and the transfer switches that supply 

critical loads from either normal or emergency power sources.

Protected locations are imperative for the entire emergency power system 

and the equipment it serves, which take into account local conditions of the 

facility. Each component of the system should be evaluated in conjunction 

with expected hazards and by understanding how each interrelated 

component impacts another. For example, fresh air intakes should not 

impinge on sprinklers or any freeze-sensitive components. Although a 

generator installation may be acceptable when considered in isolation, if its 

operation creates unacceptable ambient conditions, the generator will not 

provide satisfactory performance or life cycle expectations. Generator 

FEMA P-1019 6: Design Considerations for Emergency Power 6-3 

Systems in New Facilities
exhaust should be directed to a proper location away from facility air intakes

to avoid reentry into buildings and occupied spaces. 

A holistically planned electrical distribution system is as important as power 

generation. Dedicated and protected emergency power wiring is 

recommended to reduce the potential that failures of non-critical equipment 

and wiring disrupt critical equipment. A study of the electrical system

performed by a competent design professional will highlight additional areas 

of interrelated functionality and help broaden the design view, thus 

strengthening the holistic approach.

6.1.3 Holistic Design Tools and Culture

In order to foster holistic design and implementation on any project starts 

with assembling a diverse team early in the schematic design phase. 

Contracting methods that bring together multiple disciplines of engineering 

to the project early in the design process have the advantaged of breaking

down silos of work product, driving a holistic collaborative effort. Often, 

trade subcontractors can provide significant project-wide input when 

employed to provide design phase services. Contracting methods which 

foster this holistic design approach during the programming phase can pay 

dividends far in excess of upfront consulting costs. 

Recent technological advances in design also promote a holistic approach. 

Building Information Modeling (BIM) is widely being used to create threedimensional architectural drawings with component information embedded 

in the file structure. BIM can produce integrated multi-disciplinary design 

documents that can be analyzed and reviewed by a diverse engineering 

design team allowing for simultaneous input, as well as better collaboration 

throughout the design and construction process. 

6.2 Identification of Emergency Power Needs and 

Emergency Power Sources

Early in the design process, the critical functions of a facility need to be 

identified. For example, for a high school design, will the school’s 

gymnasium be used as a secondary shelter? For a fire station, will the entire 

facility need to remain functional after a hazard event or will just the dispatch 

and communication center within the building be sufficient? For a hospital, 

what departments or critical functions are needed to provide expected 

services when utility power is lost and what functions can possibly be 

postponed or diverted to other facilities? Chapter 3 provides guidance on 

whether a facility should be considered a critical facility and Chapter 4 

provides guidance on selecting building systems to be considered essential 

6-4 6: Design Considerations for Emergency Power FEMA P-1019

Systems in New Facilities
 

for purposes of needing emergency power and the duration, assuming these 

functions cannot be postponed or diverted.

The decision of whether to power the facility from permanently installed or 

temporary generators also needs to be made. If alternate power is not needed 

immediately following a loss of utility power, temporary generators may be 

adequate. However, if power is needed before temporary generators can be 

delivered to the site and connected to the facility, on-site generation will need 

to be installed. Both permanently installed and temporary generators require 

reliable fuel sources. Chapter 5 contains discussions on selecting the fuel 

source for emergency generators. 

6.3 Fire Protection, Mechanical, and Electrical Design 

Considerations that Affect Emergency Power Systems

The design team for a new critical facility can have a significant impact on 

design requirements and engineering of the emergency power system. In this 

section, guidance to these professionals from a holistic perspective is 

provided.

6.3.1 Fire Protection and Mechanical Engineering 

Fire pumps and air conditioning are two of the heaviest loads to serve from 

emergency generators. Accordingly, fire protection engineering and 

mechanical engineering can have a significant impact on emergency power 

demand loads. 

6.3.1.1 Fire Suppression

Fire pumps are required by code in high-rise structures, or when the available 

water flow or water pressure is inadequate to operate the fire sprinkler 

system. Often, the amount of water available for suppression is outside of 

the designer’s control. When facilities are constructed remote from water 

sources or are placed on elevated sites, fire pumps are needed to boost water 

pressures and flows to acceptable levels. In those instances, generators must 

be sized to accommodate electrically driven fire pumps or separate diesel fire 

pumps need to be installed. It should be noted that use of diesel fire pumps 

would reduce emergency power requirements (Figure 6-1). However, there 

are instances where water sources can provide acceptable flow rates if larger 

sprinkler piping is used. In those cases, fire suppression systems should be 

designed to function without fire pumps or with the smallest fire pump

required. If fire pumps are needed to provide adequate water flow for fire 

suppression, past analyses show that generator capacity requirements may 

increase ten-fold over emergency power requirements for loads not related to 

fire pumps. 

FEMA P-1019 6: Design Considerations for Emergency Power 6-5 

Systems in New Facilities
If fire pumps are required, either diesel-driven fire pumps or electric fire 

pumps with separate emergency generators should be considered. This is to 

avoid oversizing an emergency or standby generator, sized to provide power 

to essential equipment.

Figure 6-1 Diesel-driven fire pumps.

6.3.1.2 Heating and Ventilation 

Most commercial facilities are heated by fossil fuels, such as No. 2 fuel oil, 

natural gas, and occasionally propane. No. 2 fuel oil is heating oil nearly 

identical to off-road diesel fuel. 

The electrical requirements for operating fossil fuel heating systems 

generally include:

• Power to operate furnaces, air distribution equipment, and controls (hot 

air systems)

• Power to operate boilers, hot water circulation pumps, air distribution 

equipment, and controls (hydronic systems)

Compared to all-electric heating systems (also called electric resistance 

systems), fossil fuel-fired heating systems place relatively low loads on 

emergency power sources. Most of the energy required to heat a space is not 

provided by the generator but rather is obtained from fuel combustion. 

Therefore, if the option is available, heating for critical facilities that must be 

supplied by emergency power systems should be provided by fossil fuels

rather than by electric resistance.

6-6 6: Design Considerations for Emergency Power FEMA P-1019

Systems in New Facilities
Besides selecting which fossil fuel will be used to heat the building, other 

design decisions can further reduce generator requirements, including:

• Air handling equipment that uses the smallest distribution fans practical

should be selected. For larger fans, motor controls and starters that 

reduce starting currents should be selected. 

• For hydronic systems, hot water distribution pumps should be controlled 

to reduce starting currents. 

• For hydronic systems requiring multiple pumps to operate, control 

systems should be developed that allow the largest pump motor to 

operate continuously and smaller pump motors to operate cyclically 

when additional flow is needed. With this control approach, the 

generator will not be exposed to the starting load of a large cyclically 

operated motor. 

Another option that is becoming more prevalent is geothermal systems. In 

these systems, heat pumps are typically used to draw heat out of an earth 

loop while heating the building or rejecting heat to an earth loop while air 

conditioning. Geothermal loops can use large motors (50 horsepower or 

greater) to circulate water through the facility. When used with conventional 

across-the-line starters, those large motors place great demands on a 

generator when they are started. For all large motors like geothermal pumps, 

starters like wye-delta starters, or other “soft” starters should be used when 

those motors must be supplied from an emergency power source. Appendix 

C provides additional discussion on starter options.

6.3.1.3 Air Conditioning 

The selection of air conditioning equipment can have a profound effect on 

generator requirements for facilities where air conditioning is considered 

critical. 

In general, direct expansion (DX) units place lower demands on an 

emergency power source than central chilled water systems. Also, they more 

readily allow selection of specific areas of a facility to be mechanically 

cooled. Central chilled-water systems, on the other hand, require operating 

the chiller (which requires a large generator to start and run) whenever any 

space needs to be air conditioned. However, the decision to select DX units 

or central systems usually is dictated by the day-to-day use of the facility and 

not on its occasional use as an emergency facility. 

FEMA P-1019 6: Design Considerations for Emergency Power 6-7

Systems in New Facilities
For DX units, the following are recommended: 

• Configure controls to allow individual areas to be operated separately. 

Allow units that serve areas not used for sheltering or other critical 

functions to be turned off when normal power is not available.

• As far as practical, control large fan motors with variable frequency 

drives (VFD) or use starters that limit motor-starting currents. Avoid 

across-the-line starters for all large motors.

• Supply operating and control power from single feeders.

For central systems, the following are recommended: 

• Select chiller units to operate in stages and base load the larger 

compressors within the chillers.

• Control chilled water pumps with VFDs that limit starting currents.

• As much as practical, control large fan motors with VFDs or use starters 

that limit motor-starting currents. Avoid across-the-line starters for all 

large fan motors. See Section 6.3.2.2 for additional discussion.

6.3.2 Electrical Engineering 

Historically, much of a building’s electrical design is in response to the 

mechanical engineering design. The electrical engineer typically designs 

power delivery to equipment selected by the mechanical engineer. However, 

since the electrical engineer will need to design the critical power system and 

that system is greatly affected by the mechanical design, a collaborative

approach is needed, making electrical engineering input on the selection of 

mechanical equipment appropriate. Also, HVAC controls can be 

programmed to reduce peak electrical demand. Peak demand reduction may 

reduce the size of the generator required. 

Emergency power and distribution systems, particularly power and 

distribution systems that operate over 600 volts, can be vulnerable to 

transient voltage surges. Transient voltage surges can result from lightning, 

from the switching of heavily loaded circuits, from the operation of vacuum 

switches, and from the operation of non-linear power supplies. Standards 

developed by the Institute for Electrical and Electronics Engineers (IEEE

1990 and 1993) contain discussions and recommendations on reducing the 

effects of transient voltage surges. 

6.3.2.1 Lighting 

Compared to the generator capacity required to operate mechanical systems, 

the generator capacity needed for lighting systems is relatively low. 

6-8 6: Design Considerations for Emergency Power FEMA P-1019

Systems in New Facilities
However, efficient lighting design is still important. Lighting systems in 

commercial facilities generally consist of fluorescent luminaires or high 

intensity discharge (HID) fixtures, such as high pressure sodium or metal 

halide or more recently light emitting diodes (LEDs). These light sources 

have efficiencies of around 100 lumens per watt. Few light sources are 

commercially available that exceed that level. Incandescent light sources

should be avoided since their efficiency is greatly less than that of 

fluorescent, HID, or LED sources.

Metal halide HID fixtures have a prolonged restrike (restart) period where 

lamps within metal halide fixtures need to cool off following even a 

momentary power interruption before they can restart and illuminate the 

space. Auxiliary lighting systems using quartz or fluorescent lamps are often 

required to provide illumination during that restrike period. 

6.3.2.2 Controls

Where possible, large motors should be designed to be started in sequence 

(i.e., stagger-started or delay-started) to reduce peak loads placed on 

emergency generators. All large motors that need to be supplied from 

emergency power systems should be provided with soft-start features to 

reduce motor starting loads.

Control for HVAC loads should be provided from the electrical feeders that 

power those loads. This approach simplifies providing emergency power to 

select equipment since energizing the feeders that power those loads from a 

generator will also provide emergency power to their control devices. Where 

possible, HVAC equipment should be controlled to reduce fluctuations in 

demand when operated by the emergency power source. 

6.4 Design Considerations Regarding the Layout, 

Location, and Protection of Emergency Power 

Systems 

Once the critical functions are identified, mechanical and electrical needs can 

be identified. Critical functions should be grouped together where possible 

to enable the portions of the facility that house these functions to be made 

more structurally robust and less vulnerable to natural hazards than other 

portions of the structure. Where and how these functions and emergency 

power systems are located are dependent upon the natural hazard of concern.

It should be noted that sometimes recommendations for one hazard may 

conflict with those of another. For such situations, the final placement of the 

system should be taken under careful consideration by the design team.

FEMA P-1019 6: Design Considerations for Emergency Power 6-9

Systems in New Facilities
6.4.1 Design Considerations for Reducing Flood Risks 

For an emergency power system to be effective, the entire system must be 

above the flood level or otherwise protected from flood waters. This 

includes the generator and all electrical distribution equipment that is part of 

the emergency system, transfer switches, feeders, panel boards, fuel tanks, 

and controls. In addition, all critical equipment that the emergency power 

system supplies must be elevated. Flood risk considerations should not be 

limited to the emergency power systems. Electrical conduits, even those that 

are not part of the emergency power system, can provide pathways that allow 

floodwaters to enter a building when they are located below the flood levels. 

Sanitary sewer lines can allow floodwaters to enter a building if not provided 

with backflow devices or other methods of flood protection. Below grade 

utility trenches can be particularly problematic. When utility trenches are 

required to be placed in flood hazard areas, they should be provided with 

barriers to prevent floodwater entry.

For an emergency power system to serve a critical facility, it must, as a 

minimum, be provided with the same level of flood protection as that 

provided for the facility itself. However, due to the importance of 

emergency power systems and the essential equipment they serve, it is 

prudent to provide more flood protection than what is provided for the 

facility. Figures 6-2 and 6-3 show an elevated generator and associated 

switchgear that withstood Hurricane Ike with no flood damage. 

Codes and standards, such as the 2012 IBC and ASCE 24-05, Flood 

Resistant Design and Construction (ASCE, 2005), contain criteria that are 

based on the base flood, i.e., the flood event that has a 1% chance of being 

equaled or exceeded in any given year, or the design flood when adopted 

locally. The minimum flood protection is tied to the base flood elevation

(BFE) (the elevation of floodwaters including wave height associated with 

the base flood) or the design flood elevation (DFE) (the flood elevation 

associated with the design flood). For example, ASCE 24-05 requires flood 

protection a height of 1, 2, or 3 feet in addition to the DFE or the BFE levels, 

depending on the importance of the facility and its orientation to approaching 

waves.

Other more stringent criteria may apply. For example, following a major 

flood event, Interim Recovery Maps that depict Advisory Base Flood 

Elevations (ABFEs) are often developed to help communities benefit from 

the best available data during rebuilding and some federal funding requires 

protection to the 0.2% annual chance flood. Also, FEMA 543, Design Guide 

for Improving Critical Facility Safety from Flooding and High Winds:

6-10 6: Design Considerations for Emergency Power FEMA P-1019

Systems in New Facilities
Figure 6-2 Example of an elevated generator; photograph shows the intake 

louver in Galveston, Texas, 2010.

Figure 6-3 Switchgear, normal, and emergency power feeds, and associated equipment elevated

to the same level as the emergency generator at UTMB, Galveston, Texas in 2010.

Providing Protection to People and Buildings (FEMA, 2007a), recommends 

critical equipment be elevated as required by ASCE 24-05 or the 500-year 

flood level (the level of the flood event that has a 0.2% chance of being 

equaled or exceeded in any given year) whichever is greater. It should be 

noted that the minimum flood provisions and design flood elevations of 

FEMA P-1019 6: Design Considerations for Emergency Power 6-11

Systems in New Facilities
contemporary codes and standard continue to be revised as more information 

is gathered following flood events.

Regardless of the criteria, it is recommended that minimum flood provisions 

specified by codes and standards apply to all systems within a facility. For 

emergency power systems and the equipment they supply in critical facilities, 

it is recommended that more stringent criteria be applied. After Superstorm 

Sandy destroyed emergency power systems and critical equipment in many 

critical facilities, FEMA P-942 report, Mitigation Assessment Team Report, 

Hurricane Sandy in New Jersey and New York (FEMA, 2013a),

recommended building systems in Risk Category IV structures and certain 

Risk Category III structures be provided with one additional foot of flood 

protection above that specified for other structures.

In summary, it is recommended that critical facilities be protected to the 

greatest of the following flood elevations:

• Base Flood Elevation (BFE) plus 2 feet,

• Locally adopted Design Flood Elevation (DFE), and

• 500-year flood elevation (flood event having a 0.2% chance of being met 

or exceeded annually).

Emergency power systems within critical facilities and the equipment they 

supply should be protected to the greatest of the following flood elevations:

• Base Flood Elevation (BFE) plus 3 feet,

• Locally adopted Design Flood Elevation (DFE) plus 1 foot, and

• 500-year flood elevation (flood event having a 0.2% chance of being met 

or exceeded annually) plus 1 foot.

Whenever possible, flood protection should be provided by locating critical 

systems and equipment above predicted flood levels. When that is not 

possible, critical systems and equipment can be protected by dryfloodproofing to the elevation of predicted flood levels. However, the 

elevating critical systems and equipment is greatly preferred over dryfloodproofing since once floodwaters overtop dry-floodproofing provisions, 

equipment will be rapidly inundated and potentially destroyed.

It is also recommended that fuel tanks for emergency generation systems be 

placed above the DFE and the recommended flood elevations for critical 

facilities. If exposed to floodwaters, the tanks should be anchored to resist 

buoyant forces and the crushing forces of hydrostatic loads. ASCE 24-05

requires buoyancy to be calculated on an empty tank and that anchorage be 

6-12 6: Design Considerations for Emergency Power FEMA P-1019

Systems in New Facilities
 

provided to resist 150% of the buoyant forces. ASCE 24-05 also requires fill 

and vent pipes to extend above the DFE to ensure floodwaters do not enter 

tanks and displace fuel during a design flood. 

6.4.2 Design Considerations for Reducing Risks from High Wind 

Events

High winds generated by hurricanes, tropical storms, and tornadoes can 

damage both exterior equipment and equipment installed within a building if 

the building’s structure or its envelope cannot withstand wind forces or is 

damaged by wind-borne debris. 

In all installations where an emergency power system serves a critical 

facility, the entire emergency power system and its components should be 

protected from natural hazards. When an emergency power system is 

required by ICC 500-2008, Standard for the Design and Construction of 

Storm Shelters (ICC, 2008), the system must be protected from design event 

conditions.

6.4.2.1 Protecting Interior Installations 

To protect equipment from high winds, it should be placed in areas that will 

resist wind pressures, will not be penetrated by wind-borne debris, will not 

allow wind-driven rain to affect equipment operation, and will not be 

exposed to lay-down hazards (Figure 6-4). 

To resist wind pressures, the walls and roof of the generator room must be 

structurally robust and possess load path continuity that transfers all wind 

loads to the foundation. The total weight of the building, including its 

foundation, must be sufficient to resist overturning or sliding, or anchorage 

must be provided to secure the building in place. Because even small 

generators require large penetrations in the building envelope for ventilation

(for combustion air) and cooling, a generator room should be designed as a 

partially enclosed building per ASCE/SEI 7-10, Minimum Design Loads for 

Buildings and Other Structures (ASCE, 2010). Any interior walls shared 

with the rest of the building should be designed to resist at least the wind 

pressure associated with the internal pressures of a partially enclosed 

building. It may be prudent to design the internal walls of the generator 

room to resist external wind pressures to counteract failure of ventilation 

grills and louvers. 

To be effective, grills and louvers for combustion air and cooling must be 

strong enough to resist wind-borne missiles. If missile-resistant grills and 

louvers are not readily available, baffles or alcoves can be constructed to

FEMA P-1019 6: Design Considerations for Emergency Power 6-13 

Systems in New Facilities
Figure 6-4 Interior generator protected from the effects of wind and windborne debris.

prevent direct missile impact. ICC 500-2008 provides criteria for baffles and 

alcoves. This national standard bases its criteria on a much more energetic 

missile than an Type E missile, as defined by ASTM E-1996-14, Standard 

Specification for Performance of Exterior Windows, Curtain Walls, Doors, 

and Impact Protective Systems Impacted by Windborne Debris in Hurricanes 

(ASTM, 2014), so an alcove and baffle design based on ICC 500-2008 will 

likely be conservative. In addition, having a secondary roof membrane 

reduces the potential for water entry when the primary membrane is 

punctured or penetrated. FEMA 543 provides guidance on secondary 

membranes.

To prevent damage, emergency power systems and associated equipment 

should be placed in areas that are not vulnerable to lay-down hazards. If the 

equipment cannot be installed away from lay-down hazards, the lay-down 

hazards themselves should be removed or relocated. 

Another benefit of interior installation is that it allows staff to operate the 

generator without being exposed to injury. 

6.4.2.2 Protecting Exterior Installations

While exterior enclosures offer some protection from the elements, few can 

offer the same protection from high-energy wind-borne missiles and laydown hazards as a properly designed interior location. Where possible, 

exterior enclosures should be designed to resist wind pressures for Category 

IV buildings, as defined by ASCE/SEI 7-10 and resist at least a Type D, or 

6-14 6: Design Considerations for Emergency Power FEMA P-1019

Systems in New Facilities
 

preferably a Type E missile, as defined in ASTM E1996-14. Generators 

should be located where they cannot be damaged by lay-down hazards or by 

wind-borne debris. If site restrictions require placing a generator in an area 

where lay-down hazards exist, the hazards should be removed or relocated.

Structural fencing can be constructed around generator enclosures for 

additional protection, particularly from horizontal missiles. The fencing, 

which typically consists of reinforced masonry or reinforced concrete walls, 

must be designed so as not to impede airflow required for generator cooling. 

Structural fencing does not protect against vertical missiles. 

6.4.3 Recommendations for Placement where Earthquake 

Hazards are Present 

Buildings typically respond to an earthquake such that the accelerations at 

the top of a building can be two or three times stronger than those at the base. 

Therefore, if flood or storm surge hazards are not present, it is recommended 

that emergency power equipment and ancillary systems be located at grade

since seismic demands will be lower. It is generally not good practice to 

locate emergency power systems in the basement, since they may be flooded 

by seismic failure of piping systems. 

Where both seismic and flood risks exist, critical functions and the 

equipment needed to support those functions should be located on floor(s) 

with elevations above Design Flood Elevation and these functions and 

equipment should also be protected from wind forces, wind-borne debris and 

seismic effects. All critical equipment and interconnecting piping, wiring, 

and ducts should be elevated or protected as recommended in Sections 6.4.1

and Section 6.4.2. ASCE /SEI 7-10 provides requirements for designing 

buildings (including mechanical and electrical equipment) to resist seismic 

loads and FEMA E-74, Reducing the Risks of Nonstructural Earthquake 

Damage – A Practical Guide (FEMA, 2012b), provides guidance for 

designing and seismically qualifying MEP systems to perform as expected 

following Design Earthquake events. 

It is advisable that the structural engineer of the project work with the project 

architect, MEP and HVAC design team members to ensure they are fully 

aware of seismic design, equipment qualification and seismic certification 

requirements at the proposal stage of the project and that the design 

documents fully define and document design requirements, including 

anchorage bracing. Where the design and qualification of these items are 

being deferred until construction, a clear plan should be developed on how 

these requirements will be handled by the construction manager. It is likely 

that these additional engineering services will entail additional fees and these 

FEMA P-1019 6: Design Considerations for Emergency Power 6-15 

Systems in New Facilities
should be included in proposals and the initial project costs. If the project 

involves consideration of seismic requirements for MEP and HVAC systems, 

it is imperative that a structural engineer with practical design experience in 

seismic design of nonstructural systems be selected for the team. 

6.5 Code Design Requirements for Emergency Power 

Systems to Resist Severe Natural Hazards

In the United States, buildings and other structures and their architectural, 

mechanical, electrical systems are designed for natural hazards to satisfy the 

requirements of the International Building Code (IBC). The current version 

of the IBC was published in 2012. In Chapter 16 of the 2012 IBC, structures 

are classified depending on their level of importance with higher 

requirements mandated for those structures with higher importance. Most 

critical facilities are identified as essential facilities in Chapter 16 and 

classified as Risk Category IV. Other important, but less critical structures 

will classified as Risk Category III. The 2012 IBC references ASCE/SEI

7-10 for natural hazard loading and design requirements. Design maps are 

provided in the ASCE/SEI 7-10 for natural hazards that vary by location in 

the United States, depending upon the risk of that hazard occurring at 

individual site.

In ASCE/SEI 7-10, higher risk categories have higher importance factors for 

seismic and snow loads. These importance factors amplify the design 

loading, and may trigger special design and detailing provisions. On the other 

hand, wind design requirements assign different wind speeds to be used for 

design depending on Risk Category. Risk Category III and IV structures are 

to be designed for a wind speed with a 1700-year mean return interval as 

compared to normal structures (Risk Category II) which are to be designed 

for a 700-year mean return interval. On the other hand, seismic loads are 

based on Design Earthquake ground motions with a mean return period range 

between 500 and 1,000 years. For Risk Category IV structures, seismic loads 

are increased by an importance factor of 1.5 and by an importance factor of 

1.25 for Risk Category III structures. No increase is applied to Risk 

Category II structures. Therefore, considering the importance factor, Risk 

Category IV facilities are effectively being designed for design ground 

motions that have a return period that ranges between 1,000 years and 2,500 

years. In ASCE/SEI 7-10, wind loads are adjusted depending on their height 

above grade, the local topography and the wind exposure while seismic loads 

are adjusted based on soil conditions and several other factors including the 

level of seismic detailing. Certain types of structural systems are not 

permitted in areas of high seismic activity. 

6-16 6: Design Considerations for Emergency Power FEMA P-1019

Systems in New Facilities
Because critical facility structures require special expertise, it advisable that 

the project team include a structural engineer with experience in design of 

critical facilities for natural hazards that are significant to the site. Critical 

facility structures designed to satisfy the requirements of the 2012 IBC and 

ASCE/SEI 7-10 should have a high likelihood of performing well 

structurally when subjected to most severe natural hazards. It should be 

noted that ASCE/SEI 7-10 does not have design provisions for tornados or 

tsunami waves. The next version of the document, ASCE/SEI 7-16, still 

under development is scheduled to address tsunami hazards. Also,

ASCE/SEI 7-10 only considers a 100-year return period for flooding, which 

is very low considering the much higher return periods required for design 

for wind and seismic loadings. Therefore, for design of critical facilities for 

flooding, the recommendations of Section 6.4.1 of this document should be 

utilized. 

Chapter 13 of ASCE/SEI 7-10 provides seismic design requirements for

nonstructural components. Nonstructural components are defined as 

architectural, mechanical, and electrical equipment and systems associated 

with structures. The primary focus of Chapter 13 is the design of anchorage 

and bracing of nonstructural components. Procedures for determining 

seismic design forces are specified and are a function of building ground 

motion values, relative height of the component within the structure, type of 

nonstructural component, and the importance of the component. 

Nonstructural components in Risk Category IV structures have the highest 

importance and design forces. For important nonstructural components in 

higher seismic areas, not only does the anchorage bracing need to be 

designed for seismic forces but also the nonstructural components themselves

need to be designed or seismically qualified. This means that piping systems, 

HVAC ducting, and cable trays all need to be designed for seismic forces. 

Furthermore, active mechanical and electrical equipment (including those 

associated with emergency power systems), including the emergency 

generators and engines, need to be shake table tested to demonstrate they will 

function following design earthquake hazard events. FEMA E-74 provides 

guidance for designing, detailing, and seismically qualifying MEP systems to 

perform as expected following Design Earthquake events in a manner that 

would satisfy ASCE/SEI 7-10. An example of an emergency generator with 

seismically rated vibration isolators is shown in Figure 6-5.

ASCE/SEI 7-10 does not currently provide specific requirements for 

nonstructural components for natural hazards other than earthquakes. 

However, it is prudent that MEP components and systems that are part of the 

emergency power system and the MEP systems and components considered 

FEMA P-1019 6: Design Considerations for Emergency Power 6-17

Systems in New Facilities
essential for functionality of the critical facility be designed to resist the other 

natural hazards. MEP systems and components with direct wind or snow 

load exposure should be designed for the same wind speeds and snow 

loadings as Risk Category IV building structures. In addition, the IBC 

requires that structures supporting MEP systems or utilities be elevated and 

protected in accordance with ASCE 24-05. Finally, MEP systems that have 

direct wind or snow load exposure should be designed for the same wind 

speeds and snow loadings of Risk Category IV building structures.

Figure 6-5 Emergency generator supported by seismically-rated vibration 

isolators.

6-18 6: Design Considerations for Emergency Power FEMA P-1019

Systems in New Facilities
Chapter 7

Design Considerations for

Optional Standby Power 

Systems in Existing Facilities

This chapter provides guidance for providing reliable emergency or optional 

standby power systems in existing facilities. It is intended for use in cases 

where optional standby power beyond the code-minimum level is needed

following severe natural hazard events. This chapter covers two situations in 

the event utility power is not available. The first is where an evaluation made 

of an existing facility as suggested in Chapter 4 determines that optional 

standby power is needed where none currently exists. The second situation is 

where an emergency or optional standby power system exists but may have 

vulnerabilities or limitations that will make it less likely to function as 

desired following severe natural hazard events. 

As noted in Chapter 1, NFPA 70, National Electrical Code (NFPA, 2014),

classifies standby power systems as emergency systems, legally required

standby systems, optional standby systems, or critical operation power 

systems with specific requirements for each type of system. In this chapter, 

it is presumed that the standby power system addition or modification is 

being done as a voluntary upgrade and is not associated with a code mandate.

However, if the addition is being done to satisfy mandated requirements, all 

current code requirements must be followed.

When contemplating adding optional standby power to such a facility, the 

local authority having jurisdiction should be consulted, since the addition of 

a new optional standby power system may need to include upgrades to meet 

the minimum emergency power requirements of current code, as well as 

fulfill the operational goals of the owner. There are several options for 

providing sources of emergency or optional standby power in existing critical 

facilities where none currently exist. These include providing alternate 

power sources, moving the critical function to a backup facility or providing 

a new emergency power system. 

It is important to understand the potential total scope of the project early in 

the planning process. For example, if there are changes in the use or building 

code “occupancy” classification of a building that place it into Risk Category 

FEMA P-1019 7: Design Considerations for Optional Standby 7-1

Power Systems in Existing Facilities
III or IV in Table 1604.4.5 of the International Building Code (ICC, 2012)

the authority having jurisdiction may impose the code requirements for new 

buildings on the facility. The requirements for new buildings are discussed 

in Chapter 6 of this report.

For existing systems with identified vulnerabilities or limitations, there are 

several options for improving performance and reliability. However, as 

indicated in Chapter 6, what can be readily achieved with a new facility is 

much more difficult to achieve in an existing facility because of physical 

limitations and constraints. These physical limitations and constraints, as 

well as budget considerations, mean that an incremental or phased approach 

to adding or upgrading the emergency power system is a more feasible 

approach. Again, the local authority having jurisdiction should be consulted, 

regarding potential upgrades that may be required to meet the minimum 

emergency power requirements of current code.

Incremental and phased upgrades will involve compromise – what can be 

done within the time and budget constraints? In order to determine this, an 

assessment of the desired operational performance is needed, as well as an 

assessment of the existing electrical systems and physical plant. Work may 

be spread out over a number of years, as components are replaced and 

upgraded over time for operational reasons, as well as improvement of 

disaster response. Many successful phased upgrades to emergency or 

optional standby power systems have been tied to mechanical and electrical 

system upgrades that are driven by the replacement of obsolete or inefficient 

MEP systems. Replacement equipment components that draw less power 

and have special certification for seismic loads (if needed) can be selected. It 

may be possible to reconfigure some systems during an equipment

replacement or upgrade project to reduce the number of components that 

must be on optional standby power.

7.1 Considerations for Determining Optional Standby

and Emergency Power Demands in Existing Facilities 

The first step is to define the critical electrical loads that must be powered by 

emergency or optional standby power systems. This means all equipment 

related to building critical functions and their associated electrical circuits,

along with their peak and steady-state electrical loads, should be considered 

in determining the critical electrical loads. Once everything about the 

mechanical, electrical, and plumbing systems is known and documented, and 

the critical functional equipment and systems are identified, the most 

practical approach to providing standby power system capacity can be 

determined. 

7-2 7: Design Considerations for Optional Standby FEMA P-1019

Power Systems in Existing Facilities
The preferred method of operating a facility on emergency or standby power 

is to energize only those loads required to operate the facility. Energizing 

more equipment than what is necessary requires a larger generator than 

necessary and more importantly, energizing non-critical loads reduces overall 

system reliability since the failure of any non-critical equipment or faults in 

any portion of the electrical system that supplies non-critical equipment can 

interrupt power to critical equipment. It should be noted that there are some 

critical facilities, such as dedicated emergency operation centers (EOCs), 

where all portions of the facilities are deemed critical. 

An alternative, but a much less desirable method of operating a facility (other 

than an EOC type of facility) on emergency or optional standby power, is to 

energize the facility’s main electric service. Theoretically, energizing the 

main service allows an optional standby generator to deliver power to any 

electrical load within the facility and provided the generator is large enough, 

any load can be run from that source. However, since it is rarely practical to 

supply a generator large enough to power all electrical loads (except for a 

dedicated EOC type facility), energizing a facility’s electrical service 

equipment can create a risk that more power is drawn from a generator than 

it can be reliably or safely supplied. 

When properly connected and operated, energizing a facility’s electrical 

service can be an acceptable option until the facility can be modified to allow 

generators to only power equipment that is needed. In addition, Section 5.3 

provides some considerations that should be made if optional standby

generators are used as the alternate power.

7.1.1 Identifying Electrical Sources that Supply Critical Loads

All critical loads are supplied from a building’s electrical service and 

distribution system but, because of insufficient documentation, it is often not

known how the loads are supplied. This is particularly true in older facilities 

that have legacy wiring and equipment intermingled with newer wiring and 

equipment. Older facilities may have had modifications that were not fully 

documented and newer facilities may lack documentation of the original 

construction. 

Construction drawings, when available, should be investigated first. 

Electrical one-line diagrams that show the entire service and distribution

system, or riser diagrams that are one-line diagrams that also depict the 

physical layout of the service and distribution systems are particularly 

informative. One-line and riser diagrams also can identify logical connection 

points for introducing emergency power into a facility. 

FEMA P-1019 7: Design Considerations for Optional Standby 7-3 

Power Systems in Existing Facilities
Some construction drawings contain circuit lists, which list individual branch 

circuits or feeders and what equipment is supplied by those circuits and 

feeders. That documentation can be invaluable at identifying power 

distribution within the facility. Mechanical equipment schedules should also 

be investigated for additional information. 

Critical loads that draw large amounts of power are often supplied by 

electrical feeders which can have capacities of 100, 200 or even 1,000 

amperes (often shortened to amps). Small critical loads may draw very little 

current and can be supplied by 15 or 20 ampere branch circuits. For 

reference, a 120 volt hair dryer typically draws about 10 amperes; a typical 

desktop computer draws around 2 amperes, whereas a 150 ton water cooled 

chiller, large enough to air condition a 40,000 square foot office building, 

draws the equivalent of 1,200 amps.

If electrical system documentation is incomplete, system information can be 

gathered by electrical circuit tracing where electrical signals are applied to 

individual circuits or feeders and then traced through the distribution system 

with sensing devices. This method can identify the branch circuits, branch 

circuit panelboards, and feeders that supply individual pieces of critical 

equipment. Once circuits, feeders, and panelboards that supply critical 

equipment are identified, additional investigation should be conducted to 

identify non-critical loads. 

Information can also be developed by selectively de-energizing portions of 

the electrical service and distribution system and observing what equipment 

is affected. This can be done by opening circuit breakers, service 

disconnects, and overcurrent devices. This method should only be used when 

loss of power does not pose unacceptable risks to equipment or occupants. 

One benefit of selective de-energizing circuits and feeders is that doing so 

readily identifies both the critical and non-critical loads supplied by portions 

of the electrical system.

7.1.2 Reconfiguring Electrical Distribution 

Once all pieces of critical equipment and the circuits, feeders, and 

panelboards that supply them are identified, methods of providing power 

from an emergency or optional standby source can be developed. In most 

cases, it will likely be more practical to construct new power distribution 

(i.e., new feeders, new distribution panelboards, new branch circuit 

panelboards, possibly new motor control centers) within the building and 

then transfer the individual circuits or feeders that supply critical loads to the 

new power distribution system. 

7-4 7: Design Considerations for Optional Standby FEMA P-1019

Power Systems in Existing Facilities
The new power distribution system will require transfer switches, either 

manual or automatic, to transfer the critical loads from the normal power 

system when utility power is available to the emergency or alternate power 

source when utility power is lost. Transfer switches, or other methods, are 

required to prevent power from the optional standby power supply from back 

feeding through the building’s electrical service onto utility lines. Back 

feeding can kill or injure utility workers trying to repair damaged lines and 

restore power. 

Figure 7-1 is a schematic diagram that shows changes to an existing 

distribution system that allows selected loads to be supplied from an 

emergency or optional standby power system. The existing feeder and 

branch circuit that supply the critical equipment (labeled CE) are shown as 

dashed lines. Those must be disconnected when the critical loads are 

transferred to the new emergency or optional standby system. The diagram 

shows a new circuit breaker installed in the existing main service 

switchboard, a generator (labeled GEN), an automatic transfer switch 

(labeled ATS) that receives power from either the main service or from the 

generator and supplies the new optional standby power distribution system, a 

new emergency or optional standby distribution panel (labeled EDP) and a 

new branch circuit panelboard (labeled EP). 

Figure 7-1 Schematic diagram showing changes to a facility that allows critical loads to be supplied 

from an optional standby generator. 

The schematic also shows two pieces of critical equipment (CE) that need to 

operate to allow the facility to function. One piece of critical equipment is 

assumed to draw little power (e.g., a computer for HVAC controls) and can 

be supplied from the emergency branch circuit panelboard; the other critical 

equipment is assumed to draw more power (e.g., a sanitary sewer lift pump) 

and is fed from the higher capacity emergency distribution panel. In this 

schematic, since the transfer switch receives power from either the main 

service or the generator, it prevents power from the generator from back 

feeding into the main service equipment and the upstream utility system.

FEMA P-1019 7: Design Considerations for Optional Standby 7-5

Power Systems in Existing Facilities
If the existing electrical distribution system that supplies critical equipment 

only supplies critical equipment or if it supplies some non-critical equipment 

but the non-critical equipment does not add significant power demands on

the optional standby power source, then entire portions of the existing 

electrical distribution may be reconfigured to be supplied from the optional 

standby power source and the reconfiguration need not be done on an 

individual feeder/branch circuit level.

When reconfiguring the electrical system, code requirements must be 

considered. For example, to ensure reliability of the portion of the electrical 

system that supplies code-required critical loads, both the NFPA 70, National 

Electrical Code (NFPA, 2014) and NFPA 99, Health Care Facilities Code

(NFPA, 2012a), limit what equipment can be supplied from critical sources

or placed on feeders or circuits that supply code required critical loads. Code 

required loads, like emergency lighting, exit signage, and fire detection and 

alarms systems must be powered from dedicated circuits or feeders that do 

not supply other non-critical equipment. Equipment that is essential for a 

facility to function but that is not considered critical by those codes, must be 

fed separately. 

7.1.3 Providing Optional Standby Power through the Electrical 

Service

When possible, providing optional standby power by energizing the entire 

electrical service should be avoided except for EOC type critical facilities. 

However, energizing the entire electrical service may be necessary before the 

electrical system can be reconfigured to supply only critical loads from 

optional standby sources. 

The most critical aspect of energizing the building’s service equipment from 

optional standby power sources is ensuring that power cannot be back fed 

onto the utility system. The preferred method is to install a transfer switch 

upstream of the building’s service. The transfer switch allows the facility to 

be fed from either the utility or the optional standby power source but never 

simultaneously. Other methods of preventing back feeding onto utility lines 

may be acceptable. Alternate methods need to be acceptable to the electrical 

utility serving the facility. 

Of the types of standby power systems defined by NFPA 70, the only one 

where a manual transfer switch is permitted is the optional standby systems. 

Each of the other systems requires an automatic transfer switch in order to 

meet the transfer time requirements. Therefore, if an onsite generator is 

present as the optional standby power source, the transfer switch could be 

either manual or automatic. If only a pre-wired connection for a portable 

7-6 7: Design Considerations for Optional Standby FEMA P-1019

Power Systems in Existing Facilities
generator is installed, the transfer switch should be manual. However, the 

transfer switch would need to be automatic (and the generator would need to 

be sufficiently sized to power the entire building) if code required loads rely

on that generator for emergency power. 

Figure 7-2 is a schematic diagram of a transfer switch installed to supply 

service equipment from either the utility or from an optional standby power 

source.

Figure 7-2 Schematic diagram showing transfer switch installed to supply an electrical service 

from either the utility or an optional standby power source.

Another critical aspect of energizing the electric service is ensuring that the 

generator is not overloaded. Energizing the electric service will allow power 

to be delivered to any device in the building unless it can be electrically 

isolated from the service. Opening all circuit breakers within the service 

equipment that do not supply critical equipment will prevent non-essential

equipment from drawing power from and potentially overloading the 

emergency power supply. Identifying which circuit breakers that can be 

opened requires a detailed knowledge of the facility’s electrical distribution 

system. 

Often individual feeders or branch circuits supply both critical and noncritical equipment. In those instances, isolating the non-critical equipment 

may need to be done remote to the service equipment. NFPA 70 requires

that means for disconnecting be located near equipment to allow it to be deenergized for servicing. If present, they can also be used to isolate the 

equipment from the optional standby power source. If service disconnects 

are not in place, the non-critical equipment may need to be manually turned 

off. If so, procedures to prevent the inadvertent operation of the equipment 

should be developed. 

Transfer Switch

Generator 

Circuit 

Breaker

Optional Standby Power Source

Utility Power 

FEMA P-1019 7: Design Considerations for Optional Standby 7-7

Power Systems in Existing Facilities
Providing emergency power through the main service requires equipment to 

be automatically controlled. Failure to do so and allowing equipment to be 

connected manually could cause an unacceptable voltage drop, or in the 

worst case, stall the generator or cause it trip offline. 

7.2 Protecting Optional Standby Power Systems from 

Natural Hazards

Providing an optional standby power system to serve critical loads makes the 

facility much less vulnerable to loss of utility power. Making the optional 

standby power system resistant to floods, high winds, and seismic events can 

make the facility’s ability to operate more reliably. In some cases, reliability 

of an existing facility can be improved by conducting simple steps to 

strengthen or harden the equipment connections and enclosures of the 

emergency power system. 

In Section 6.4, recommendations for the layout and placement of new 

emergency power systems are provided to improve their resistance to 

withstand severe natural hazards. In Section 6.5, the code and regulatory 

requirements of new emergency power systems designed to withstand severe 

natural hazards are discussed. For situations where new optional standby

power systems are being installed in existing critical facilities, it is 

recommended that the recommendations and code requirements of Sections 

6.4 and 6.5 be followed for both the optional standby power system and the 

building or structure in which it is housed. If physical or financial limitations 

and constraints do not permit the recommendations of Sections 6.4 and 6.5 to 

be satisfied, it is recommended that the project design team minimize the 

vulnerability to the natural hazards to the maximum extent practicable to do 

so. This can be done in a cost effective manner, by addressing the 

components with the greatest vulnerabilities first. For example, unanchored 

optional standby power system components in regions of seismic risk are 

likely to displace or topple in moderate shaking. Simply anchoring the 

generator, battery racks and charger, day tank, exhaust system, and 

switchgear will significantly improve the likelihood that the optional standby

power system will function after a seismic event. If the generator is in need 

of replacement, selecting a unit that has been seismically qualified by shaketable testing will greatly improve the odds of the generator functioning 

following a strong earthquake.

The project design team should also provide the facility owner a comparison 

of natural hazards for which the facility was designed, as compared to the 

recommendations of Sections 6.4 and 6.5 in the event the owner may elect to 

do further upgrades or replacements at a later date. It should be noted that 

7-8 7: Design Considerations for Optional Standby FEMA P-1019

Power Systems in Existing Facilities
laws in some states mandate that critical facilities be retrofitted to function 

following severe natural hazards, as defined by the regulations. The project 

design team should check the laws and regulations that govern critical 

facilities for the jurisdiction for the existing critical facility for any laws and 

regulations that are applicable. It should be noted that if the primary goal is 

to have more reliable optional standby power, both the facility structure and 

the emergency power system should be evaluated and retrofitted as needed.

FEMA P-1019 7: Design Considerations for Optional Standby 7-9

Power Systems in Existing Facilities

Appendix A

General Code Considerations 

for Emergency Power 

in Critical Facilities

Building codes, and their referenced architectural and engineering standards, 

govern the design and construction of buildings. The purpose of a building 

code is to establish the minimum acceptable design and construction 

requirements necessary for protecting the public, health, safety, and welfare.

Structural integrity, building envelope integrity, fire and smoke resistance, 

life-safety considerations, sanitation, and recently, energy efficiency, are 

some of the issues addressed by contemporary building codes.

A.1 History of Building Codes

Over the last 50 years, numerous building codes have been developed. In the 

past, individual States, and occasionally individual cities, developed their 

own codes. However, because of the level of effort required to write and 

maintain effective building codes, private organizations were formed with 

the charge to write and maintain “model” building codes. Once developed, 

model codes are put through an extensive consensus process, which includes

input from all interested parties. 

Until 2000, three different model codes were widely adopted in the United 

States. Each of these codes was adopted in different regions of the country, 

and the provisions were strongly influenced by the specific concerns in each 

region. In the Northeast, the National Building Code developed by the

Building Officials and Code Administrators (BOCA) was widely adopted;

the Uniform Building Code developed by the International Council of 

Building Officials (ICBO) was widely adopted in the West; and the Standard 

Building Code developed by the Southern Building Code Congress 

International (SBCCI) was widely adopted in the Southeast. In the 1990s, 

BOCA, ICBO, and SBCCI elected to stop maintaining their individual codes 

and merged to become the International Code Council (ICC). The ICC

developed a single series of building codes, commonly referred to as the ICodes, which were intended for adoption throughout the United States. The 

series includes the: International Building Code (IBC), International 

This appendix is not

intended to be an 

exhaustive discussion of 

emergency power 

requirements, but an 

overview of codes and 

standards and how they 

relate to emergency power, 

with emphasis on the 

emergency power 

requirements of the 

International Building 

Code. 

There are other codes, 

engineering standards, and 

other requirements (like 

Joint Commission 

requirements for certifying 

health care facilities) that 

can apply to the design and 

construction of a building. 

Therefore, any discussion 

on code requirements for a 

wide range of facilities will 

inherently be limited. 

FEMA P-1019 A: General Code Considerations for Emergency Power A-1

in Critical Facilities
Residential Code (IRC), International Mechanical Code, and the 

International Energy Code. The first editions of the I-Codes were issued in 

2000. 

The IBC and the IRC are the predominant building codes that have been 

adopted in the United States. These documents are revised every three years, 

but it is not unusual for the model codes to be amended by the adopting 

authority (state and local jurisdictions) to meet local needs. Facility owners 

and operators should consult with their local building and fire officials to 

determine what requirements are currently in effect.

The National Fire Protection Association (NFPA) also developed a model 

building code. NFPA 5000, Building Construction and Safety Code (NFPA, 

2012c), was first issued in 2000 and continues to be updated and maintained.

However, it is not widely adopted in the United States. Many jurisdictions 

have adopted NFPA 101, Life Safety Code (NFPA, 2012b), for new and 

existing occupancies. Health care facilities that are regulated by the Centers 

for Medicare and Medicaid Services (CMS) are required to comply with 

NFPA 101. NFPA 101 includes requirements for emergency power and 

emergency lighting systems.

Other national standards that establish requirements for electrical systems in 

critical facilities include NFPA 70, National Electrical Code (NFPA, 2014),

NFPA 99, Health Care Facilities Code (NFPA, 2012a), and NFPA 110, 

Standard for Emergency and Standby Power Systems (NFPA, 2013c).

A.2 Emergency Power Requirements of the International 

Building Code

While the intent of the IBC includes language to guard against “other 

hazards,” emergency power requirements for most buildings are based on fire 

as the primary internal hazard and are included in Chapters 1-15 of IBC 

2012. Structural design requirements for natural hazards are provided in 

Chapter 16 (See Section 6.4 of this document), but only the seismic 

requirements provide special requirements for provision of emergency

power. However, the IBC references ASCE 24-05, Flood Resistant Design 

and Construction (ASCE, 2005), which requires utilities and equipment to 

either be elevated or dry floodproofed above the design flood elevation. 

Simply stated, Chapters 1 through 15 of the IBC requires most facilities to 

have enough emergency power to allow occupants to leave a building safely.

It does not require emergency power to allow buildings to remain functional 

during a power outage. 

A-2 A: General Code Considerations for Emergency Power FEMA P-1019

in Critical Facilities
The IBC requirements for emergency power are generally for short duration, 

typically 90 minutes, or about the maximum time required for occupants to 

exit a building. Ninety minutes of emergency power can, in most instances, 

be supplied by batteries or other stored energy devices. In most cases, 

emergency generators are not required to satisfy these code requirements. 

For the small percentage of facilities where onsite generators are needed to 

satisfy code requirements, the generators typically only supply the minimum 

loads required for life safety. Life safety loads include: fire alarm and 

annunciation systems, smoke control systems, fire pumps where present, 

emergency and egress lighting, and conveyance systems that are required for 

egress. In most cases, onsite generators required by code have neither the 

capacity nor the supply that a facility needs to remain functional during 

prolonged power outages. 

A.2.1 IBC Emergency Power Requirements by Occupancy 

Classification

Chapters 3 and 4 of the IBC contain provisions on the use and occupancy of 

buildings. How the buildings are used dictate methods of construction, 

egress requirements, life-safety requirements, and size requirements. 

Buildings are classified by Occupancy Classifications, and some occupancy 

classifications are further described by two or more Groups. For example, 

buildings with an occupancy classification of “Assembly” are used as 

gathering locations for civic, social, or religious functions, recreation or food 

consumption, or awaiting transportation. Within the “Assembly” occupancy 

classification, there are Groups A-1 (production or viewing of performing 

arts) through A-5 (participation or viewing of outdoor activities). Table A-1 

lists the occupancy classifications of the 2012 IBC. 

Facilities that typically house critical functions fall into the occupancy 

classifications shown in Table A-2. Note that building occupancies are 

determined by the locally adopted codes, as enforced by the authority having 

jurisdiction. The information in Table A-2 is provided to describe 

occupancies that are typically used for select critical facilities and should not 

be used to determine occupancy classifications. 

For structural design purposes, buildings are classified in “Risk Categories” 

in IBC Chapter 16. Buildings considered to be critical facilities that are to be 

classified into Risk Category IV are listed in IBC 2012 Table 1604.5. 

Section 3.1 provides a description of the types of buildings included in Risk 

Category IV. Structural design of buildings is to be a level to avoid 

“unacceptable performance.” Such unacceptable performance for an 

essential facility in this code context would be for the building to experience 

FEMA P-1019 A: General Code Considerations for Emergency Power A-3 

in Critical Facilities
a structural failure such that is could not perform its essential functions when 

subjected design level hazards. In addition, the seismic requirements of 

ASCE/SEI 7-10, which is referenced by 2012 IBC, also require that 

mechanical and electrical equipment and systems in Risk Category IV 

facilities that are necessary for the facility to perform its essential function be 

designed or seismically qualified so they will continue to function after being 

subjected to Design Earthquake motions. 

Table A-1 Occupancy Classifications

Occupancy Classification Groups

Assembly A-1, A-2, A-3, A-4, A-5

Business B

Educational E

Factory and Industrial F-1, F-2

High Hazard H-1, H-2, H-3, H-4, H-5

Institutional I-1, I-2, I-3, I-4

Mercantile M

Residential R-1, R-2, R-3, R-4

Storage S-1, S-2

Utility and Miscellaneous U

Table A-2 Critical Facilities by Occupancy

Occupancy Classification Critical Facility

Group A –Assembly Host shelters

Evacuation shelters

Community safe rooms1

Group B – Business Police stations

Emergency Operations Centers

Fire stations (engine house/equipment bay 

excluded)

Schools beyond the 12th grade

Group E – Educational K through 12 schools

Group I – Institutional Hospitals

Nursing homes

1 The 2012 IBC does not list community safe rooms in a specific occupancy classification. 

In the absence of a specific classification, Section 3.8 of FEMA P-361, Design and 

Construction Guidance for Community Safe Rooms (FEMA, 2008), recommends 

community safe rooms be designed as assembly Group A-3 when the space is used only as 

a safe room. For multi-use safe rooms where other occupancies apply, the requirements 

for the most stringent occupancy need to be met. 

A-4 A: General Code Considerations for Emergency Power FEMA P-1019

in Critical Facilities
Emergency power requirements specified by the IBC and its referenced 

standards depend on the occupancy classification. Most of the emergency 

power requirements are to address the risk of fire as follows: 

• Exit signs must identify doors that lead to the exterior to help occupants 

leave a building safely. 

• Emergency lights to illuminate egress routes are required, particularly for 

corridors, which can fill with smoke. 

• Fire alarm systems, either manually operated or automatically operated 

by smoke or heat detectors, or valves that detect water flow in sprinkler 

systems, must notify occupants when fire is present and may notify the 

local fire department. 

In addition to the occupancy-based requirements, the IBC also requires 

emergency power for non-specific occupancy. For instance, the IBC requires 

emergency power for elevators, personnel lifts, and other conveyance 

systems when they are relied upon for building egress. The IBC also 

requires emergency power for smoke control systems. Table A-3 

summarizes the occupancy-based IBC emergency power requirements for 

several occupancies.

Table A-3 Emergency Power Requirement by Occupancy

Emergency Power 

Requirement

IBC 

Reference

Occupancy Classification

Group A - 

Assembly 

Group B - 

Business

Group E - 

Educational

Group I - 

Institutional

Exit signs Section 

1011 X X X X 

Emergency lighting Section 

1006 X X X X 

Fire alarm Section 

907 X X X X 

Emergency 

voice/alarm systems

Section 

907 X X X X 

Smoke 

control/management 

systems 

Section 

909 X 

Elevators, lifts, and 

other conveyance 

systems required for 

egress1

 

Section 

1007 X X X X 

1 For high-rise buildings, some emergency power is required for elevators (e.g., car lighting) even 

when the elevators are not required for egress.

Some of the most stringent emergency power requirements are for 

Occupancy Group H (High Hazard). In those facilities, emergency power is 

FEMA P-1019 A: General Code Considerations for Emergency Power A-5 

in Critical Facilities
required to prevent the release of hazardous materials and prevent explosions 

that can occur when normal power is lost. The IBC also contains emergency 

power requirements for underground buildings, covered mall buildings, and 

membrane (air inflated) structures; however, because those structures are 

rarely used for a community’s critical facilities, IBC emergency power 

requirements for those types of buildings are not discussed here. 

Several other model codes, engineering standards, and guidance documents 

apply to health care facilities in the Institutional Group. This document does 

not provide an exhaustive list or description of applicable codes for those 

facilities.

A.2.2 Emergency Power Duration Requirements

The IBC has the following requirements for emergency power duration:

• Exit Signs: IBC 2012 Section 1011.6.3 requires that emergency power 

systems for exit signs provide power for a minimum of 90 minutes. 

• Emergency Lighting: IBC 2012 Section 1006.3 requires the same 90-

minute duration for emergency lighting. 

• Fire Alarm Systems: IBC 2012 references NFPA 72, National Fire 

Alarm and Signaling Code (NFPA, 2013a), for fire alarm system

requirements. 

Smoke control systems, elevators, lifts, and other equipment required for 

egress require continuous emergency power.

A.3 Fire Pump Requirements

Many facilities use automatic sprinkler systems, which use water for fire 

suppression. For various reasons, sufficient water pressure and volume may 

not be available from a municipal water system to meet code requirements 

for a facility sprinkler system. In those facilities, fire pumps are required to 

boost municipal water pressure and volume. The specific requirements for 

fire pumps can be found in NFPA 20, Standard for the Installation of 

Stationary Pumps for Fire Protection (NFPA, 2013d). 

Fire pumps can be powered by direct-coupled diesel engines or electric 

motors. Fire pumps powered by electric motor have special code 

requirements. Fire pumps are code-mandated to have a reliable source of 

power. Determining the reliability of power sources, however, is subjective, 

and decisions are often made by the local authority having jurisdiction (plan 

examiners or inspectors) without the benefit of specific reliability criteria. 

To ensure this important device has reliable power, plan examiners and 

A-6 A: General Code Considerations for Emergency Power FEMA P-1019

in Critical Facilities
inspectors often require a second power source. The second source is often 

an onsite stand-by generator; a feeder from the generator to provide this 

second source is included. NFPA 20 specifies the requirements for standby 

power for fire pumps. Facility owners and operators should work closely 

with the authority having jurisdiction to ensure compliance with the 

applicable code requirements. The insurance company that is providing 

coverage for the facility may also provide guidance that can reduce risk 

premiums.

Section 3-6.4 of Unified Facilities Criteria (UFC) 3-600-01, Design Manual 

for Fire Protection (Department of Defense, 2006), provides some guidance 

on utility system reliability. UFC 3-600-01 defines a reliable electrical 

source as “a power source having an average forced down time, excluding 

scheduled repairs, which does not exceed 8 consecutive hours for any one 

incident or more than 24 hours cumulatively over the last 3 years.” The goal 

of fire protection is the protection of life and property. To protect occupants 

of critical facilities that may be occupied during prolonged power outages, 

UFC 3-600-01 recommends that fire pumps be connected to emergency 

power generators (even if not required by local authorities) to provide power 

whenever the facility is occupied, and thereby ensure the pumps can operate 

when normal power is not available.

A.4 Critical Healthcare Facility Power Distribution 

Requirements

NFPA 99 Healthcare Facilities Code lists requirements for provision of 

emergency power in critical healthcare facilities. These requirements are 

subdivided into distribution branches to power various groups of medical 

equipment and support facilities. These are the following: (1) equipment 

branch; (2) critical branch; and (3) life-safety branch. The life-safety branch 

is the most important and given the highest priority. 

These requirements are specifically designed for healthcare facilities, but 

they offer a good set of guidelines for other facilities to consider when 

determining what elements should be provided with emergency power 

beyond the basic code minimum requirements.

A detailed list of elements, taken from NFPA 99 is listed in Tables A-4 

through A-7. Those elements which correspond to basic code requirements, 

generally the items on the Life Safety Branch, are included in Table 4-1.

FEMA P-1019 A: General Code Considerations for Emergency Power A-7

in Critical Facilities
Table A-4 Items Requiring Emergency Power in Healthcare Facilities: Life Safety Branch

Life Safety Branch

A. Egress lighting

B. Exit signs and exit directional signs

C. Hospital communications systems where used for issuing emergency related instructions

D. Generator set location as follows

a. Task illumination

b. Battery charger for emergency battery-powered lighting unit(s)

c. Select receptacles at the generator set location and essential electrical system transfer switch locations

E. Elevator cab lighting, control, communications 

F. Electrically powered doors used for building egress

G. Fire alarms and auxiliary functions of fire alarm systems complying with NFPA 72

Table A-5 Items Requiring Emergency Power in Healthcare Facilities: Critical Branch

Critical Branch

A. Task lighting and select receptacles in anesthetizing gases locations

B. Isolated power systems in special environments

C. 

Task illumination and select receptacles in patient care rooms including infant nurseries, selected acute 

nursing areas, psychiatric bed areas (omit receptacles),and ward treatment rooms, medication preparation 

areas, pharmacy dispensing areas, nurses’ stations (unless adequately lighted by corridor luminaires)

D. Additional specialized patient care task illumination and receptacles, where needed

E. Nurse call systems

F. Blood, bone, and tissue banks

G. Telephone equipment rooms and closets

H. 

Task illumination, select receptacles, and select power circuits for general care beds with at least one 

duplex receptacle per patient bedroom, and task illumination as required by the governing body of the 

health care facility, angiographic labs, cardiac catheterization labs, coronary care units, hemodialysis rooms 

or areas, emergency room treatment areas, human physiology labs, intensive care units, postoperative 

recovery rooms 

I. 

Additional task illumination, receptacles, and select power circuits needed for effective facility operation, 

including single-phase fractional horsepower motors, which are permitted to be connected to the critical 

branch

A-8 A: General Code Considerations for Emergency Power FEMA P-1019

in Critical Facilities
Table A-6 Items Requiring Emergency Power in Healthcare Facilities: Equipment Branch 

(Automatic Connection)

Equipment Branch

A. Central suction systems serving medical and surgical functions

B. 

Sump pumps and other equipment required to operate for the safety of major apparatus, including 

associated control systems and alarms

C. Compressed air systems serving medical and surgical functions

D. Smoke control and stair pressurization systems

E. Kitchen hood supply or exhaust systems, or both, if required to operate during a fire in or under the hood

F. 

Supply, return, and exhaust ventilating systems for airborne infectious/isolation rooms, protective 

environment rooms, exhaust fans for laboratory fume hoods, nuclear medicine areas where radioactive 

material is used, ethylene oxide Evacuation, anesthetic evacuation.

G. 

Where delayed automatic connection is not appropriate, ventilation system shall be permitted to be placed 

on the Critical Branch

Table A-7 Items Requiring Emergency Power in Healthcare Facilities: Equipment Branch 

(Automatic or Manual Connection) 

Equipment Branch

A. 

Heating equipment used to provide heating for operating, delivery, labor, recovery, intensive care, 

coronary care, nurseries, infection/isolation rooms, emergency treatment spaces, and general patient 

rooms; and pressure maintenance (jockey or make-up) pump(s) for water-based fire protection systems

B. 

Heating of general patient rooms during disruption of the normal source shall not be required under any of 

the following condition

a. Outside design temperature is higher than 6.7°C (+20°F)

b.

Outside design temperature is lower than 6.7°C (+20°F), where a selected room(s) is provided for the 

needs of all confined patients [then only such room(s) need be heated]

C. Elevator(s) selected to provide service to patient, surgical, obstetrical, and ground floors

D. 

Supply, return, and exhaust ventilating systems for surgical and obstetrical delivery suites, intensive care, 

coronary care, nurseries, and emergency treatment spaces

E. Hyperbaric facilities

F. Hypobaric facilities

G. 

Autoclaving equipment, which is permitted to be arranged for either automatic or manual connection to 

the alternate source

H. Controls for equipment listed in NFPA 99, 6.4.2.2.4

I. Other selected equipment

FEMA P-1019 A: General Code Considerations for Emergency Power A-9 

in Critical Facilities

Appendix B

Redundancy of Electrical 

Power Systems

Redundancy is a key strategy for improving the reliability of both utility 

power systems and individual critical facility emergency power systems. In 

this Appendix, the concepts and the common implementation approaches to 

redundancy for these systems are described.

B.1 Redundant Utility Source Delivery

The point at which the utilities revenue metering is installed is called the 

“utility service entrance” point. The system upstream of that point is the 

utility’s responsibility; the downstream components are generally the 

responsibility of the end users. In order to create utility service redundancy, 

critical facilities, such as hospitals, large campuses, and industrial plants or 

complex commercial facilities, often negotiate with the utility (or 

occasionally with other utilities) to supply power from more than one utility 

source. In some cases the separate source may be supplied by the utility 

from dedicated sub-transmission or distribution lines. With this level of 

utility redundancy, a high level of reliability is attained. 

The theory of redundant services is that the probability of all electrical 

services failing simultaneously is much less than the probability of a singleservice failure. Redundant services can provide uninterrupted electric power 

even when one service fails or, as a minimum, redundant services can 

significantly reduce outage durations when an electrical failure occurs.

However, having multiple incoming distribution lines can be expensive and 

may be cost prohibitive for many users. 

One of the more common methods of employing redundant utility feeds is 

shown in Figure B-1. With this method, two separate utility transformers 

provide power to two separate services that supply a double-ended service 

switchboard. The switchboard contains two main circuit breakers (one for 

each of the two services) and a tie circuit breaker. The facility can be 

operated in two possible line-ups. In the normal operation mode shown 

below (Figure B-1a), both main circuit breakers are kept closed and the tie 

breaker kept open. Operation from both utility sources is referred to as 

“normal” because the loading of utility equipment keeps it warm and 

FEMA P-1019 B: Redundancy of Electrical Power Systems B-1
minimizes deterioration of condensing humidity. With the normal operation 

mode, both utility services supply the facility: One utility service supplies the 

left-hand switchgear and the other utility service supplies the right-hand 

switchgear with the tie breaker in open position, separating the two. With the 

line-up shown in Scenario #1 and Scenario #2 (Figures B-1b and B-1c, 

respectively), one of the main service circuit breakers and the tie breaker are 

kept closed, and the other main service breaker is open. With these line-ups, 

the entire facility is powered from one of the two services. Physically, there 

is no difference in the wiring configuration between the two line-ups. The 

difference is only in how they are typically operated and how the facility can 

respond to an electrical outage. 

As shown in Figure B-1b (Scenario #1), the loss of Utility Source #2 will 

briefly shut down the left-hand section of the switchgear, but by opening the 

failed service circuit breaker and closing the previously open tie breaker, the 

facility can be re-energized quickly. In Scenario #2, the loss of Utility 

Source #1 will interrupt power to the right-hand switchgear of the circuit but 

power can be reestablished quickly by opening the failed service circuit 

breaker and closing the tie breaker. In critical facilities, this “main – tie –

main” circuit breaker opening and closing is generally automatic.

It can be observed that another option for normal operation is as follows: the 

entire facility could operate from one of the utility sources with one main and 

the tie breaker closed and the redundant utility feeder open; but in ready 

reserve. Failure of the normally closed utility feed could initiate a switch 

from one source to the other with the tie breaker remaining unchanged. The 

transfer from one utility to the other source would require a delay of many 

seconds. This delay is necessary to allow for all facility motor loads to spin 

down and preclude them from acting as generators. This temporary source of 

electrical energy would be out of synch with the utility source and result in a 

damaging fault if connected to the utility. It is noted that for redundant feeds 

to be most effective, utility sources should originate from different 

distribution line circuits and preferably from different distribution 

substations. 

Other variations of redundant utility source delivery are possible with 

cooperation with the electrical service provider. A common example where 

a single point of utility power delivery is used but where some redundancy is 

provided would be a “spot network.” With a spot network, power is 

introduced into a network (also called “collector bus”) at several points. For 

power at the collector bus to be lost, all power connections feeding that bus 

would need to fail. The network is typically operated at distribution voltages 

B-2 B: Redundancy of Electrical Power Systems FEMA P-1019
Figure B-1 Schematic diagram for one style of redundant service illustrating 

circuit breaker responses if a utility source fails. 

(a)

(b)

(c)

FEMA P-1019 B: Redundancy of Electrical Power Systems B-3
Again, for redundant feeds to be most effective, they should originate from 

different distribution line circuits and preferably from different distribution 

substations. 

While there are many variations of utility-networked systems, they all have 

in common the ability to supply uninterrupted power to the customer’s 

facility through some parallel redundancies should one or more of the 

utility’s sources fail. This type of utility scheme is especially advantageous 

for users with large inductive motor loads where voltage sags can occur. 

This paralleling of utility sources requires highly specialized network 

equipment and redundant power feeders. 

B.2 N+1 Redundancy Strategy

Critical facility managers often feel that the installation of an onsite

emergency generator will provide uninterrupted power to the facility. 

However, it is important to realize that any power source, whether it is a 

utility service or an onsite generator, can fail. Each critical facility manager 

should be acutely aware that any power system employed can be called upon 

in the most critical time. Prudent planning dictates careful consideration be 

given to the potential for failure even in an emergency power system. 

N+1 is a strategy providing redundancy to safeguard against a single 

component failure. N+1 is a term used in numerous applications including 

power distribution, mechanical systems, and information technology. In N+1 

terminology, “N” stands for the minimum number of devices, such as

modules, power sources, and pumps, required to perform the intended 

function. “N+1” stands for the minimum plus one redundant unit. For 

example, one large generator may supply critical loads in a building. But 

when called upon, a simple failure will prevent from operating when it is 

needed. Instead, a strategy involving two smaller generators to supply the 

load, with a third generator of equal size in parallel as a group provide N+1 

redundancy. Most highly critical facilities, such as hospitals and large data 

centers, employ an N+1 strategy whether utilizing batteries, generator 

systems, or a combination of both. This strategy is also advocated by 

operations and maintenance considerations, allowing single units to be taken 

offline for preventive maintenance without sacrificing operations protection. 

N+1 strategy can be applied to each component of the critical system. One 

large fuel tank can be replaced by two smaller tanks with parallel fuel rails 

feeding the multiple generator system. Parallel filter sets allow a filter clog 

or be changed while continuing to operate. Parallel generator start battery 

packs with individual chargers are inexpensive options providing significant 

redundancy to components historically most likely to fail. Critical facilities, 

B-4 B: Redundancy of Electrical Power Systems FEMA P-1019
such as hospitals, are required by code to maintain parallel utility feeds into 

the main switchgear as described above. Applying N+1 strategy, many 

large-scale critical facilities also use parallel emergency bus feeders to 

emergency panel boards. 

When formulating an N+1 design strategy, it is important to consider the 

impact of any aspects of the design having a common failure mode that could 

negate the intended N+1 performance objective. An example would be the 

placement of the “normal power” electrical switchgear in the same room (or 

within the same fire barrier) as the emergency generator electrical 

switchgear. A fire, flood, or other hazard that causes all of the electrical 

switchgear to fail negates the N+1 design.

Regardless of what customer or utility supplied redundancy is determined to 

meet the post-event operational performance expectations of the critical 

facility, it is imperative that all stakeholders consider the increased space and 

facility requirements. The overall business performance expectations may be 

such that more than twice the space would be required over that of a baseline code compliant facility. This reality of design and construction 

requirements should not be overlooked when planning new systems or 

retrofitting into a completed facility. The implementation of redundancy 

strategies for critical equipment and systems is an integral part of emergency 

management contingency planning and should be carefully considered by 

facility operators and design professionals.

FEMA P-1019 B: Redundancy of Electrical Power Systems B-5

Appendix C

Generator Sizing

This appendix discusses the sizing of generators for emergency or alternate 

power systems.

C.1 Generator Load Requirements

Generators must be large enough to supply their peak electrical load while 

maintaining adequate voltage and frequency. The peak electrical load is 

generally the load required to start the largest motor (or the motor with the 

most extreme starting characteristics) while being base-loaded by all other 

equipment that may need to run concurrently. 

Motors require much more current to start than to operate. Their starting 

characteristics depend on many factors, such as their synchronous speed, 

their inertia, and their electrical characteristics. When designing supplies for 

motors, engineers consider a motor’s locked rotor current. As the name 

implies, the locked rotor current is the amount of current drawn when a 

motor’s shaft is locked in place and prevented from rotating. When started, 

the amount of current a motor draws approaches its locked rotor current and 

in most installations, the locked rotor current must be provided while the 

generator is already operating other loads. 

Motors are assigned a code letter that correlates their locked rotor current to 

their horsepower (hp). Table C-1, based on NFPA 70, National Electrical 

Code (NFPA, 2014), lists code letters for motors and the associated ranges of 

locked rotor kVA/hp. As an example, a 10 hp Code K motor would draw 

between 80.0 kVA (10 hp × 8.0 kVA/hp) and 89.9 kVA (10 hp × 8.99

kVA/hp) under a locked rotor condition. 

Assuming that the generator had to supply a 35 kVA load while starting that 

motor, its peak load would be 35 kVA plus 89.9 kVA for a total of 125 kVA. 

A generator with a peak capacity of 125 kVA would be the minimum 

required: a 150 kVA generator would likely be chosen to provide some room 

for expansion. If the motor had a less severe starting characteristic (for 

example, a Code D motor) a smaller generator would suffice. An 80 kVA

generator could start a 10 hp Code D motor (10 hp × 4.49 kVA/hp for a total 

of 45 kVA) while concurrently supplying a 35 kVA load. Again, the prudent 

selection of a 100 kVA unit would provide capacity for load expansion.

FEMA P-1019 C: Generator Sizing C-1
Table C-1 Motor Codes and Associated Lock Rotor Apparent Power (kVA/hp)

(from NFPA 70)

NFPA 70 Table 430-7(B) - Locked Rotor Indicating Code Letters

Code Letter Kilovolt-Ampere per Horsepower with Locked Rotor

A 0 - 3.14

B 3.15 - 3.54

C 3.55 - 3.99

D 4.0 - 4.49

E 4.5 - 4.99

F 5.0 - 5.59

G 5.6 - 6.29

H 6.3 - 7.09

J 7.1 - 7.99

K 8.0 - 8.99

L 9.0 - 9.99

M 10.0 - 11.19

N 11.2 - 12.49

P 12.5 - 13.99

R 14.0 - 15.99

S 16.0 - 17.99

T 18.0 - 19.99

U 20.0 - 22.39

V 22.4 and up

It should be noted that for short durations, generators can supply loads in 

excess of their nameplate rating. The amount of additional capacity depends 

on how closely the prime mover is matched to the generator, on the 

synchronous speed and the inertia of the generator and the prime mover and 

on the duration that the load must be supplied. Generator manufacturers 

should be consulted to determine the ability of a generator to support short 

duration loading. 

Often several motors, all smaller than the largest motor, are connected to an 

electrical system in a fashion that as soon as the system is energized (either

by normal or emergency power), the motors will attempt to start 

C-2 C: Generator Sizing FEMA P-1019
simultaneously. When powered from an emergency generator, the generator 

recognizes the group as one large motor and that significant generator 

capacity is needed to successfully start those motors. Simple controls, like 

adding time delay relays so all of the generators do not try to start 

immediately after power resumes or controls that stagger-start motors can 

prevent the simultaneous starting of several motors. Such controls are 

relatively easy to obtain, can be installed relatively inexpensively, and can 

significantly reduce required generator capacity. When this strategy is 

deployed, it is common practice to start the motor with the largest surge 

current first. An exception to this is when larger motors are associated with 

cycling loads. For this case, the largest cycling motor should be started last 

and therefore the generator size will be increased to handle the running 

steady-state load of the non-cycling motors plus the starting surge current of 

the cycling motor(s). Strategies for progressively starting allow the smallest 

generator set for the overall total emergency power load. 

Other improvements are available to reduce required generator capacity 

needed to start the largest motor(s). For example, wye-delta (or star-delta) 

starters allow the motor to be started with reduced voltage, which reduces the 

starting currents and the required generator capacity. Also, reactor starting 

where reactors (inductive impedance) are introduced in series with the motor 

can also reduce starting currents. The inductors are removed from the circuit 

after the motor reaches its operating speed. Digital soft starters and variable 

frequency drives (VFDs), used to vary the speed of motors, can also reduce 

starting demand and required generator capacity. Often, the savings 

associated with reducing generator capacity more than offset the cost of 

installing motor controls (particularly if sophisticated controls are only 

needed only on a few motors). 

Most steps that reduce starting demand reduce the torque that the motor 

produces while starting. Before those actions are taken, it should be 

confirmed that reduced starting torque is acceptable. 

Non-linear loads must be reviewed to determine if it will be necessary to derate generator capacity to compensate for heating effects of harmonic

currents. If field measurements are used to determine harmonic 

contributions, it will be necessary to utilize specialized instrumentation to 

determine harmonic content. Typical non-linear loads are caused by the use 

of the following:

• Variable frequency drives,

• Solid-state type uninterruptible power supply units,

FEMA P-1019 C: Generator Sizing C-3
• Battery charger loads used to convert AC to DC and provide a controlled 

charge to batteries,

• Lighting loads, except incandescent, and 

• In the case of a high-density environment of personal computers, it may 

be necessary to increase neutral capacity to carry significantly larger 

“third harmonic current.”

Other specialized loads which can impact generator sizing are:

• Medical imaging loads – Voltage dip limits must not be exceeded when 

operated with all other loads, and

• Regenerative loads, such as elevators, cranes, and hoist, where the power 

source absorbs power during braking when the motor is being overhauled 

by its dynamic load and acting as a generator.

C.2 Continuous Generator Load

Predicting the continuous load on a generator follows the same approach as 

estimating the continuous load on a utility power service. The total 

connected load on an emergency system is totaled and demand and diversity 

factors are applied to address the fact that all loads do not operate 

continuously at their maximum load. Diversification is a common term used 

to refer to the cyclic or non-concurred operational characteristics of multiple 

loads on the entire system. The design engineer should have a good 

understanding of the diversity component of the total expected load early in 

the sizing calculation.

Predicting demand and diversity factors is never straightforward. There are 

several publications available to assist electrical engineers and designers 

estimate continuous load, many published by the Institute of Electrical and 

Electronics Engineers (IEEE).

Designers are cautioned not to use the same demand and diversity factors for 

an emergency system as used for the normal utility system. When a facility 

is operated under emergency power, the occupancy of the facility may be 

significantly different than during non-emergency operations and the 

equipment that is energized from the generator may be operated with 

different demand and diversity factors than those under normal conditions. 

To address this, designers need to select demand and load factors that 

accurately represent the system when powered from the emergency power 

source.

C-4 C: Generator Sizing FEMA P-1019
C.3 Maximum Allowable Voltage Dip

The ideal generator would provide constant voltage under any load condition. 

However, like utility power systems, generators are not ideal. With both 

types of systems, voltage dips or momentary sags occur as loads are added.

Invariably, utility power systems are “stiffer” than standalone generators and 

experience less voltage fluctuation for a given added load. 

Commercially available generators have a certain amount of voltage output 

variation as a function of their rated load. As load is added to a generator, 

the voltage output dips until the generator engine and regulator can work 

together and compensate for the added load (by increasing fuel flow) and 

return the voltage to normal. Large, instantaneous load additions contribute 

to larger voltage dips. 

If the entire load that a generator serves is added simultaneously, the 

generator can experience a severe voltage dip. However, if the load is added 

gradually, in a step-wise fashion, the generator voltage drop will be less. For 

this reason, generator sizing should consider not only the maximum load but 

how loads in a facility will be applied. For example, consider a building that 

has no building automation system to control HVAC loads. If the generator 

for that building were required to carry the load on a hot or cold day, many of 

the HVAC units would likely start simultaneously when the loads were 

transferred to the generator, contributing to a higher-than-normal voltage 

drop. To limit the voltage drop to acceptable levels, a larger generator would 

need to be selected. Alternatively, controls must be chosen. 

The allowable step voltage dip percentage must also be chosen. Some 

generator manufacturers list a 35% default allowable voltage dip percentage. 

This amount of voltage dip can be excessive for an office building with a 

high concentration of sensitive electronics, such as computers and data 

processing equipment. For such facilities, a more moderate voltage dip 

percentage of 20% may be preferred and included in the calculations. 

Reducing the allowable voltage dip will require a generator with a larger 

capacity. 

C.4 Maximum Allowable Frequency Dip

The ideal generator power frequency output would always exactly match that 

of the electric utility, which in the United States is typically 60 Hz (many 

European countries operate on 50 Hz). However, similar to voltage dip 

described previously, frequency decreases as loads are added to a generator 

until the generator engine and regulator can compensate and return the 

FEMA P-1019 C: Generator Sizing C-5
frequency to normal. Large, instantaneous load additions generally result in 

larger frequency dips. 

The allowable frequency dip percentage must also be chosen. Some 

manufacturers list a 10% default allowable frequency dip. This may be 

excessive for some facilities. A more moderate dip of 6% may be preferred. 

Like tighter voltage control, tighter frequency control results in a need for 

larger generators. 

C.5 Caution on Oversizing Generators 

Although capacity for additional allowance should be considered for future 

growth, providing a diesel generator that is oversized by more than double 

the current load is not advised. Operating a diesel generator for extended 

periods under light loading conditions can lead to engine damage, reducing 

its reliability and significantly increasing maintenance costs. In some cases, 

generators have required a complete engine overhaul within only a few 

hundred hours of operation because of this phenomenon. Most 

manufacturers recommend continuous loading on the diesel generator of at 

least 30% of its rated capacity. This minimum continuous loading level 

requirement factors heavily into decisions regarding generator capacity 

sizing and selection. 

Unlike gasoline engines utilizing spark plugs, a diesel engine utilizes hot 

compressed air in the cylinder to vaporize and ignite the fuel. Diesel 

generators operating under low load conditions burn very little fuel and as a 

result run cooler than their design temperature. Cooler temperatures within 

the cylinder create less than optimum burn conditions resulting in soot 

forming in the engine and exhaust system. This soot condenses in exhaust 

stacks creating “wet stacking.” This condition, over a prolonged period, can 

seriously degrade engine performance and can lead to permanent engine 

damage. Careful design and thorough generator test protocols should be 

used to eliminate potential wet stacking. 

To avoid oversizing generators, yet still provide for load growth, engineers 

should size generators close to the required load but consider adding 

additional generators in the future in the design provisions. Ensuring 

generator rooms have space for additional units, additional switchgear, and 

likely synchronizing gear will allow logical and effective expansions to an 

emergency power system. When properly planned, installing additional units 

for increased system capacity can also facilitate maintenance and improve 

reliability.

C-6 C: Generator Sizing FEMA P-1019
Appendix D

Emergency Power System 

Operational Checklist 

The following checklists are provided as a helpful aid on items that should be 

checked before, during and following an extreme natural hazard event. They 

should be tailored to the individual facility situation. 

Disclaimer: The following information supplements the generator 

manufacturer’s application, installation, operation, and maintenance 

information and requirements. Always read, understand, and follow the 

manufacturer’s guidance. When there is conflict between the manufacturer’s 

and the below information, consult with qualified personnel to determine 

necessary methods and materials.

Table D-1 Checklist for Emergency Planning Prior to Emergency or Disaster

Checklist for Emergency Planning Prior to Emergency or Disaster 3

1. Combustion Air Intake and Exhaust Systems

a. Louvers Operational with no restricted movement and no obstructions

b. Rain cap No restricted movement

c. Exhaust piping No foreign object blockage, i.e., bird and rodent nesting, condensation drained 

2. Batteries

a. Batteries installed in conditioned air space to avoid temperature extremes

b. Interconnecting cables sized to compensate for voltage drop

c. Charging system operational and alarms tested

d. Specific gravity and voltages checked and acceptable

e. Cable connections corrosion free and tight on both ends

3. Generator set controller

a. All lock-out faults investigated, corrected, and cleared

b. AUTO start engaged

4. Output circuit breakers Closed or ready and able to close if electrically operated 

5. Load cables Clean and terminations checked for proper spacing and torque 

6.

Engine block, generator space heaters, 

circulating pump(s)

Operational and circulating warm coolant and oil (if equipped 

with pump)

FEMA P-1019 D: Emergency Power System Operational Checklist D-1 
Table D-1 Checklist for Emergency Planning Prior to Emergency or Disaster (Continued)

Checklist for Emergency Planning Prior to Emergency or Disaster 3

7. Fuel Delivery System

a. Fuel quality tested and storage vessels maintained to prevent water accumulation and bacterial growth 

b. Storage vessels, including day tanks, topped to appropriate levels

c. Fuel transfer pumps powered by emergency system and periodically tested

d. Preferred customer agreements in place with fuel suppliers to assure delivery

8. Engine oil

a. Low run time, capable of at least 48 hours continuous run time

b. Level proper

c. Scheduled Oil Sample results reviewed and proper actions taken

d. Spare oil and delivery methods, i.e. funnels, pumps, drum carts, etc. nearby

e. Leaks Inspect and correct

9. Consumables 10 day supply (minimum) in on-site storage

a. Fuel filters

b. Oil filters

c. Air filters

d. Oil

e. Coolant 

10. Local, state, and federal authorities and service organizations

a. Emergency plans developed

b.

Road maintenance crews aware and in agreement that site’s public access is critical and shall be 

maintained and at all times to allow emergency vehicle passage

c.

Aware and in agreement that fuel delivery and engine generator set parts and service organizations are to 

be considered and labeled as emergency vehicles with authorized site passage

d. 

Service organizations have developed emergency plans to assure effective support staffing is available and 

capable

11. Communications

a. Portable cell towers available and capable of being placed and made operational in short time

b. Site two-way radios and cell phones charged and fully operational

c.

Site data reception and transmission systems inspected and proper operation tested with remote facilities 

and personnel

12. Generator

a. Windings clean

b. Space heaters operational

c. Bearings properly greased

d. Air intake and exhaust air paths cleared of dirt, debris, and obstructions

13. Cooling system

a. Proper levels

b. Leaks Inspect and correct

D-2 D: Emergency Power System Operational Checklist FEMA P-1019
Table D-2 Checklist for Operation During Emergency or Disaster

Checklist for Operation During Emergency or Disaster 3

1. Combustion air intake Louvers open and no obstructions

2. Output circuit breakers Closed or ready and able to close if electrically operated

3. Fuel delivery system

a. Fuel quality tested and storage vessels maintained to prevent water accumulation and bacterial growth 

b. Storage vessels, including day tanks, topped to appropriate levels

c. Fuel transfer pumps powered

d. Water separators drained

4. Engine oil

a. Level checked periodically and determined proper

b. Plan oil changes on the fly if needed

5. Consumables Restock to 10 day supply (minimum) in on-site storage

a. Fuel filters

b. Oil filters

c. Air filters

d. Oil

e. Coolant 

6. Local, State, and Federal Authorities and Service Organizations

a. Emergency plans implemented

b. Road maintenance crews maintaining site’s public access

c. Fuel delivery and engine generator set parts and service organizations allowed site access

d. 

Service organizations implemented emergency plans to assure effective support staffing is available and 

capable

7. Communications

a. Portable cell towers available and capable of being placed and made operational in short time

b. Site two-way radios and cell phones charged and fully operational

c. Site data reception and transmission systems properly operating

8. Generator

a. Winding temperatures acceptable

b. Bearings properly greased

c. Air intake and exhaust air paths cleared of debris and obstructions

d. Stable output voltage and frequency

9. Condition Monitoring

a. Receiving data

b. Results normal

FEMA P-1019 D: Emergency Power System Operational Checklist D-3 
Table D-3 Checklist for Recovery Following Emergency or Disaster 

Checklist for Recovery Following Emergency or Disaster 3

1. Combustion Air Intake and Exhaust Systems

a. Louvers Closed and no obstructions

b. Rain cap Closed

c. Exhaust piping Inspect and drain condensation

d. Wet stacking Inspect and develop corrective action plan

2. Batteries

a. Charging system operational and alarms tested

b. Specific gravity and voltages checked and acceptable

c. Cable connections corrosion free and tight on both ends

3. Generator set controller 

a. All lock-out faults investigated, corrected, and cleared

b. AUTO start engaged

4. Output circuit breakers Closed or ready and able to close if electrically operated

5. Load cables Clean and terminations checked for proper spacing and torque

6. Engine block, generator space heaters, circulating 

pump(s)

Operational and circulating warm coolant and oil (if 

equipped with pump)

7. Fuel delivery system

a. Fuel quality tested and storage vessels maintained to prevent water accumulation and bacterial growth 

b. Storage vessels, including day tanks, topped to appropriate levels

8. Engine oil 

a. Change oil and filter(s) and sample as needed

b. Level proper

9. Consumables Re-stock to 10 day supply (minimum) in on-site storage

a. Fuel filters

b. Oil filters

c. Air filters

d. Oil

e. Coolant 

10. Local, state, and federal authorities and service organizations

a. Emergency plans reviewed and improved

b. Road maintenance crews remove debris and repair damage to allow site access

c. Service organization emergency plans reviewed and improved

11. Communications

a. Portable cell towers retracted, maintained, and properly stored

b. Site two-way radios and cell phones charged and fully operational

c. Site data reception and transmission systems inspected and proper operation tested with remote facilities 

and personnel

D-4 D: Emergency Power System Operational Checklist FEMA P-1019
Table D-3 Recovery Following Emergency or Disaster (Continued)

Checklist for Recovery Following Emergency or Disaster 3

12. Insulation system test conducted and results analyzed to detect erosion

a. Space heaters operational

b. Air intake and exhaust air paths cleared of debris and obstructions

c.

Air gap between rotor pole and stator measured at 12:00, 3:00, 6:00, and 9:00 positions, recorded, and 

analyzed to detect bearing wear or misalignment

d. Excitation system inspected and tested

e. Voltage regulator connections inspected and properly torqued

f. Insulation system test conducted and results analyzed to detect erosion

13. Cooling System

a. Proper levels

b. Drain, flush, and replace coolant as needed

c. Leaks Inspect and correct

FEMA P-1019 D: Emergency Power System Operational Checklist D-5 

Appendix E 

Examples of How to Utilize this 

Document

This appendix provides two examples complete with descriptions of 

challenges and solutions as an instructional tool to better understand the use 

of this document to aid in decision making for emergency power systems.

The flow chart provided in Chapter 1 illustrates the underlying decision 

making process. As stated throughout this document, facility owners and 

operators should collaborate with a qualified integrated design team to 

develop solutions.

E.1 Example 1 – New Facility

A rural town in the Midwest is planning the construction of three new 

schools: a new elementary school (grades K through 4), a middle school 

(grades 5 through 8) and a high school. Design for the first phase, the new 

elementary school is complete. The construction project has been awarded 

and site work is scheduled to begin within two months. The remaining two 

schools are planned to be completed within 12 years. The town is 

approaching its bond limit and the schedule for the final school will be

dictated by final construction costs of the first two schools.

The area is vulnerable to tornadoes and winter storms. An EF-2 tornado 

struck the town four years ago and destroyed 20 homes; more were damaged 

but were repairable. Many of the overhead distribution lines were 

constructed in the 1940 and 1950s and are particularly vulnerable to damage 

when radial ice accretion levels exceed 1/4 inch. Power outages from winter 

storms typically last four days but can extend into two weeks. 

The local planning board passed a resolution to fund construction of tornado 

safe rooms in each new school to provide protection for students, staff, and 

volunteers. The planning board also passed a resolution to support the use of 

schools for short-term host shelters for residents of the town. 

The school board, planning board, and the design team for the middle school 

are collaborating to determine the feasibility of providing emergency power 

that will allow the gymnasium to be used as a host shelter that can house 

residents following winter storms. Emergency power for the tornado safe 

FEMA P-1019 E: Examples of How to Utilize this Document E-1
room, estimated to be only 7.5 kW for lights and ventilation, will be part of 

the safe room budget. The bond limits are placing constraints on the project 

budget. 

E.1.1 Emergency Power Functions Determination

A needs assessment is conducted, as follows. 

E.1.1.1 Normal Operations

• The school will be designed for a population of 600 students and a staff 

of 40 teachers, administrative staff, and custodial staff. 

• The single floor structure will be constructed on grade. No below grade 

spaces are proposed. 

• The entire school will be heated and mechanically cooled by packaged 

natural gas fired rooftop units with integral DX units with compressors, 

condensers and evaporative coils. 

• Sanitary sewer will be gravity fed; a potable water service and a fire 

suppression service will be provided. Hydrant tests confirm domestic 

pressures are sufficient; no fire pump or domestic water booster pump 

will be required. A fractional horsepower jockey pump may be installed 

on the sprinkler system to maintain pressure. 

• Exit signage, egress lighting and a fire alarm detection and annunciation 

system will be provided to meet the requirements of NPFA 101, Life 

Safety Code (NFPA, 2012b). The emergency power source for exit and 

emergency lighting and for the fire alarm system will be provided by 

batteries integral to that equipment. 

• A 100 foot by 125 foot gymnasium will be constructed on the east side of 

the site. Restroom and locker room facilities will be adjacent to the 

gymnasium. 

• The gymnasium will have dedicated HVAC units. 

• Gymnasium lighting will be high intensity discharge (HID) metal halide.

• A 30 foot by 70 foot kitchen and a 70 foot by 70 foot cafeteria will be 

constructed on the west side of the site.

• The kitchen’s ovens, grills, and steam tables will be natural-gas fired and 

controlled electrically. A commercial walk-in freezer and walk-in 

refrigerator are proposed. 

• The cafeteria will have movable furnishings to allow the space to 

function as an auditorium. 

E-2 E: Examples of How to Utilize this Document FEMA P-1019
E.1.1.2 Operations as a Host Shelter

• The usable space in the gymnasium can provide space to shelter 100 

people at the recommended 50 square feet per person. 

• The host shelter will be made available approximately two days after an

event and will remain operational for up to 14 days. 

• The host shelter will be used primarily to house occupants displaced 

from their homes by loss of power following winter storms. 

• Food service is desired.

E.1.2 Proposed Solution

Preliminary electrical load analyses based on square footage estimates 

predict that the total operating load for the gymnasium, kitchen, and 

cafeteria, while operating in the heating mode, will be 100 kW. Air 

conditioning would add an additional 75 kW. 

At current construction pricing, a permanently installed generator is 

estimated at $200,000. The additional cost required to allow the equipment 

serving the gymnasium, kitchen, and cafeteria to be operated as optional 

standby equipment is estimated at $20,000. That includes the cost of 

dedicated feeders, manual transfer switches, and panelboards. The flanged 

connection for a permanent generator is estimated at $12,000. 

The permanent generator and its required maintenance are considered 

impractical with the town’s projected construction projects and its bond 

status. The planning board considered the additional site work and 

infrastructure that will allow the gymnasium, kitchen, and cafeteria to be

supplied from an optional standby generator acceptable.

The design team developed the following concepts to allow portions of the 

facility to function as a host shelter:

• Provide a concrete pad with vehicle access adjacent to the electrical 

service room. 

• Install an emergency distribution panel in the electrical room. Distribute 

emergency power from a manual transfer switch that receives power 

from the main electrical service or from a portable generator. 

• Install two dedicated panelboards in the kitchen wing and two in the 

gymnasium. Combining the distribution equipment for the gymnasium 

and kitchen is not practical due to the physical separation of the two 

areas. (One panelboard for HVAC loads and one for lighting and other 

electrical loads.) 

FEMA P-1019 E: Examples of How to Utilize this Document E-3 
• Select each HVAC unit for the kitchen and the gymnasium from two 

separate feeders. One feeder will supply heating, ventilation, and control 

functions; the second feeder will supply air conditioning.

• Supply the fire alarm, egress lighting, and exit signage from an 

emergency power panel.

• Supply other desired loads (telephone, network server, computer outlets, 

clock system, staff lounge) from an emergency power panel when the 

desired equipment improves functionality, but does not significantly 

increase required loads on the emergency system. 

• Elevate all essential equipment to protect from flooding; install all 

essential equipment to resist wind damage and damage from seismic 

events. 

• Establish contracts with local suppliers for temporary generators, fuel, 

and generator service. 

E.2 Example 2 – Existing Facility

A medium size community hospital is planning an expansion. The current 

bed tower has NFPA 99, Health Care Facilities Code (NFPA, 2012a),

compliant emergency power and distribution but would like to provide for a

new 50-bed expansion wing, as well as air conditioning for the total inpatient population and expanded emergency services in radiology. The 

current hospital employs one 2,000 kW generator to serve the existing 

emergency power needs but is fully loaded by the existing building. The 

hospital administration is lobbying to install a second 2,000 kW generator to 

double generation capacity. Budgetary constraints are an issue as 

construction of the 50-bed addition absorbs the majority of available funding. 

E.2.1 Analysis: Emergency Power Functions Determination

• It is readily understood that minimum NFPA 99 required emergency 

power will not satisfy the business model of sustained community health 

care service during a local emergency event advocated by upper 

management. A detailed study of the exact equipment and emergency 

power loads needed shows that the proposed additional 2,000 kW load is 

generally divided equally between NFPA 99 requirements for the new 

bed tower including air conditioning and the upgrades for the existing inpatient spaces and radiology equipment. 

• Maintenance operations note that during a recent winter storm power 

outage, a small day tank pump at the generator failed. Maintenance was 

E-4 E: Examples of How to Utilize this Document FEMA P-1019
able to troubleshoot and bypass this pump quickly but noted the facility 

was within 20 minutes of generator failure at a critical moment.

• Engineering analysis recognizes the current basement level of the 

hospital is below the 500-year base flood elevation.

• Budgetary constraints become evident that the entire 2,000 kW desired 

addition will not be immediately financially achievable.

E.2.2 Proposed Solution 

• The realization of the maintenance issue concerning the day tank pump

resonates with management. The value of an N+1 redundant scheme is 

readily apparent (see Appendix B). The addition of two 1,000 kW

generators instead of the one 2,000 kW is preferred.

• The redundancy scheme is extended to distribution feeders as well. It is 

noted that the current emergency bus carrying the supply to the building 

was originally sized to handle the original 2,000 kW generator and is at 

capacity. Rather than up-size the current bus, a second bus can be 

installed parallel to the existing bus. This allows constructability of the 

new system while keeping the existing building emergency power 

capability intact, lowering the construction costs of removing the existing 

busway. 

• Generator synchronizing board and switchgear installations are planned 

for an extended mechanical space on the second floor protecting the new 

gear from flooding. 

• The fuel storage tank must also be upsized to maintain the hospital’s 

regulatory requirement of 96-hour runtime. A second tank can be 

installed with cross-connect capability such that any generator’s day tank 

can be fed from either main storage tank. Care must be taken in a recirculating fuel rail assembly such that returning fuel cannot route to a 

single tank either starving one or overfilling another.

• Budgetary constraints are a major concern and a phased approach is 

offered. 

o Phase 1 – Install one 1,000 kW generator, second bus, and new 

synchronizing switchboard. This new service will primarily serve 

the new bed tower expansion but feeding a common board for 

distribution as needed. The new programmable switchgear and 

multiple generators will allow for loads to be categorized into 

priority blocks. Life-safety equipment will reside in a priority block, 

which will keep life safety and selected loads from the new tower 

and existing building operational in the event of a single generator 

FEMA P-1019 E: Examples of How to Utilize this Document E-5 
failure. Subsequent equipment can operate at a lower priority and be 

load shed in case of a single generator failure.

o Phase 2 – In a subsequent budget year, the second 1,000 kW

generator can be added to the existing system, readily expanding the 

capabilities of equipment served by emergency power. General 

patient population air conditioning for the existing in-patient 

population, as well as select radiology services, can be added.

o Phase 3 - If the second bus is sized properly, a future third generator 

can be added to the set. With proper synchronizing board 

programming modifications, the current bus hardware can be utilized 

providing additional emergency power with lower installation costs.

E-6 E: Examples of How to Utilize this Document FEMA P-1019
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:www.joplinglobe.com/carthage_jasper_county/x212107033/Ice-storm-sdamage-toll-may-reach-400-million

/print+&cd=1&hl=en&ct=clnk&gl=us. Last accessed on September 14, 

2014.

Tulsa Tornado Tribune, 2007, Historic Ice Storm of January, 2007, National 

Weather Service Tulsa, Oklahoma. Available at 

http://www.srh.noaa.gov/media/tsa/tribune/spring07.pdf. Last accessed 

September 14, 2014. 

F-4 F: References FEMA P-1019
USA Today, 2007, Storms Give Texas an Unexpected Shiver, published on 

January 18, 2007. Available at http://usatoday30.usatoday.com/weather

/stormcenter/2007-01-18-ice-storm_x.htm. Last accessed on September 

14, 2014.

USGS, 2014, http://earthquake.usgs.gov/learn/topics/mercalli.php. Last 

accessed September 19, 2014.

FEMA P-1019 F: References F-5

Project Participants

ATC Management and Oversight

Christopher Rojahn (Program Executive)

Applied Technology Council

201 Redwood Shores Parkway, Suite 240

Redwood City, California 94065

Jon A. Heintz (Program Manager)

Applied Technology Council

201 Redwood Shores Parkway, Suite 240

Redwood City, California 94065

Ayse Hortacsu (Project Manager)

Applied Technology Council

201 Redwood Shores Parkway, Suite 240

Redwood City, California 94065

FEMA Oversight

Michael Mahoney (Project Officer) 

Federal Emergency Management Agency

500 C Street, SW, Room 416

Washington, D.C. 20472

Gregory P. Wilson (Task Monitor) 

Federal Emergency Management Agency

1800 S. Bell Street,

Arlington, Virginia 22202 

Erin Walsh (Task Monitor) 

Federal Emergency Management Agency

500 C Street, SW, Room 416

Washington, D.C. 20472

John Gillengerten (Technical Monitor)

5155 Holly Drive 

Shingle Springs, California 95682

Project Technical Committee

Robert E. Bachman (Project Technical Director)

25152 La Estrada Dr. 

Laguna Niguel, California 92677 

Donald P. Bliss

National Fire Protection Association

1 Batterymarch Park

Quincy, Massachusetts 02169

Philip J. Caldwell

Schneider Electric

1990 Sandifer Blvd.

Seneca, South Carolina 29682

David Low

4900 Summer Lane

Earlysville, Virginia 22936

Derek Wilson 

55 Ponderosa Lane

Lake Monticello, Virginia 22963

Steven R. Winkel

The Preview Group, Inc.

2765 Prince Street

Berkeley, California 94705

FEMA P-1019 G: Project Participants G-1 
Project Review Panel

Chad Beebe

American Society for Healthcare Engineering

155 N. Wacker Drive 

Suite 500

Chicago, Illinois 60606

Robert Berninger

Memorial Sloan-Kettering Cancer Center

3751 Waverly Ave.

Seaford, New York 11783

Jim Carlson

Seismic Source International

9814 Whithorn, Suite A

Houston, Texas 77095

William L. Coulbourne 

Applied Technology Council

19266 Coastal Highway, Unit 4, #19

Rehoboth Beach, Delaware 19971

Mark Early

National Fire Protection Association

1 Batterymarch Park

Quincy, Massachusetts 02169

Therese P. McAllister

National Institute of Standards and Technology

100 Bureau Dr.

Gaithersburg, Maryland 20899 

Steve Sappington

175 Cutstone Court

Fayetteville, Georgia 30215

G-2 G: Project Participants FEMA P-1019