Distributed Energy Resource (DER) Reliability for Backup Electric Power Systems

Jeffrey Marqusee, Andrew Stringer

Research output: NRELTechnical Report


Hospitals, emergency services, military bases, ports, airports, industries, commercial facilities, and others rely on backup power systems to provide electricity for their critical loads during grid outages. The purpose of this report it to provide accurate reliability information on commonly deployed distributed energy resources (DERs) to improve quantitative estimates for the reliability of these backup power systems during a grid outage. A backup power system consists of DERs, an electric distribution system with its associated switches and other devices, and mechanisms to control and manage the flow of electricity. Too often, facilities and campuses fail to properly quantify the reliability of their backup power systems. DERs are assumed to be 100% reliable, with the only concern being the availability of fuel. Such assumptions can lead to gross errors in the backup system's reliability estimates, particularly for long-duration outages. This report provides a set of estimates for reliability of emergency diesel generators (EDGs), natural gas prime generators and combined heat and power (CHP) prime movers, solar photovoltaics (PV), wind turbines, and Li-ion battery energy storage systems (BESS). The estimates are derived from empirical data when available and supplemented by modeling results when needed. These reliability estimates are for the DERs ability to provide power during a grid outage, ranging from an hour to 2 weeks.
Original languageAmerican English
Number of pages46
StatePublished - 2023

Bibliographical note

Produced by the National Renewable Energy Laboratory (NREL) under the Department of Defense's Environmental Security Technology Certification Program (ESTCP) under Agreement IAG-18-02080

NREL Publication Number

  • NREL/TP-7A40-83132


  • backup power systems
  • CHP
  • DER
  • emergency generator
  • prime generator
  • solar photovoltaics
  • US Army Corps of Engineers
  • wind turbine


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