Glossary - E

For your convenience, this page contains an alphabetically organized list of terms, definitions and common acronyms used in the electric utility industry.


Term/Acronym Definition
E-TAG Electronic Tag
EAF Equivalent Availability Factor
EAL Estimated Aggregate Liability
EC Electric Cooperative
ECI Element Competitiveness Index
EDI Electronic Data Interchange
EEA Energy Emergency Alert
EFT Electronic Funds Transfer
ELSE External Load Serving Entity
EMMS Energy and Market Management System
EMS Energy Management System
EP Energy Provider
EPRI Electric Power Research Institute
EPS ERCOT Polled Settlement

Electric Reliability Council of Texas

ERCOT BOARD The Board of Directors of the Electric Reliability Council of Texas, Inc.
ERS Emergency Response Service
ESI ID Electric Service Identifier
Electric Cooperative (EC)
  1. A corporation organized under the Electric Cooperative Corporation Act, TEX. UTIL. CODE ANN. ch 161 (Vernon 1998 & Supp. 2007);
  2. A corporation organized as an electric cooperative in a state other than Texas that has obtained a certificate of authority to conduct business in Texas; or
  3. A successor to an electric cooperative created before June 1, 1999 under a conversion plan approved by a vote of the members of the electric cooperative, regardless of whether the successor later purchases, acquires, merges with, or consolidates with other electric cooperatives.

Electric Reliability Council of Texas, Inc. (ERCOT)

A Texas nonprofit corporation that has been certified by the PUCT as the Independent Organization for the ERCOT Region.

Electric Reliability Organization The organization approved by the Federal Energy Regulatory Commission (FERC) to perform the electric reliability organization functions described in the Electricity Modernization Act of 2005, 16 U.S.C. § 824o (2005).
Electric Service Identifier (ESI ID) The basic identifier assigned to each Service Delivery Point used in the registration and settlement systems managed by ERCOT or another Independent Organization.
Electrical Bus
  1. A physical transmission element defined in the Network Operations Model that connects, using breakers and switches, one or more:

    1. Loads;
    2. Lines;
    3. Transformers;
    4. Generators;
    5. Capacitors;
    6. Reactors;
    7. Phase shifters; or
    8. Other reactive control devices to the ERCOT Transmission Grid where there is negligible impedance between the connected Transmission Elements.

  2. All Electrical Buses are designated by ERCOT and TSPs for modeling the electrical topology of the ERCOT Transmission Grid.

Electrically Similar Settlement Points

Two or more distinct Settlement Points that are either mapped to the same electrical location in a market model or are mapped to locations that are connected by a transmission element with a reactance of less than 0.0005 per unit.

Eligible Transmission Service Customer A Transmission and/or Distribution Service Provider (TDSP) (for all uses of its transmission system), or any electric utility, MOU, EC, power generation company, CR, REP, federal power marketing agency, exempt wholesale generator, Qualifying Facility (QF), Independent Power Marketer, or other Entity that the PUCT has determined to be an Eligible Transmission Service Customer.
Emergency Base Point The target MW output level for a Resource that is selected by ERCOT during an Emergency Condition.
Emergency Condition An operating condition in which the safety or reliability of the ERCOT System is compromised or threatened, as determined by ERCOT.
Emergency Notice The fourth of four levels of communication issued by ERCOT to declare that ERCOT is operating in an Emergency Condition.
Emergency Ramp Rate The maximum rate of change (up and down) in MW per minute of a Resource to provide Responsive Reserve (RRS) that is deployed by ERCOT and that is provided to ERCOT in up to ten segments, each represented by a single MW per minute value (across the capacity of the Resource), which describes the available rate of change for the given range (between High Sustained Limit (HSL) and Low Sustained Limit (LSL)) of the generation or consumption of a Resource. In Real-Time SCED Dispatch, the up and down Emergency Ramp Rates are telemetered by the QSE to ERCOT and represent the total capacity (in MW) that the Resource can change from its current actual generation or consumption within the next five minutes divided by five.
Emergency Rating See Rating

Emergency Response Service (ERS)

An emergency service consistent with P.U.C. SUBST. R. 25.507, Electric Reliability Council of Texas (ERCOT) Emergency Response Service (ERS), used during an Energy Emergency Alert (EEA) to assist in maintaining or restoring ERCOT System frequency. ERS is not an Ancillary Service.

ERS with a ten-minute ramp period.

ERS with a 30-minute ramp period.

Non-Weather-Sensitive ERS
A type of ERS in which an ERS Resource may participate in ERS without meeting the qualification requirements for weather sensitivity set forth in paragraph (5) of Section, Emergency Response Service Procurement.

Weather-Sensitive ERS
A type of ERS in which an ERS Load may participate in ERS only after meeting the qualification requirements for weather sensitivity set forth in paragraph (5) of Section

Emergency Response Service (ERS) Contract Period A period designated by ERCOT during which an ERS Resource is obligated to provide ERS consisting of all or part of the contiguous hours in an ERS Standard Contract Term.
Emergency Response Service (ERS) Generator Either (1) an individual generator contracted to provide ERS which is not a Generation Resource or a source of intermittent renewable generation and which provides ERS by injecting energy to the ERCOT System, or (2) an aggregation of such generators.
Emergency Response Service (ERS) Load A Load or aggregation of Loads contracted to provide ERS.
Emergency Response Service (ERS) Resource Either an ERS Load or an ERS Generator.
Emergency Response Service (ERS) Self-Provision The designation by a QSE of one or more ERS Resources to meet some or all of that QSE’s Load Ratio Share (LRS) of the total ERCOT-wide cost of ERS.
Emergency Response Service (ERS) Standard Contract Term One of three periods for which ERCOT may procure ERS.

Emergency Response Service (ERS) Time Period

Blocks of hours in an ERS Standard Contract Term in which ERS Resources are contractually committed to provide ERS.

Energy Emergency Alert (EEA) An orderly, predetermined procedure for maximizing use of available Resources and, only if necessary, curtailing load during an Emergency Condition while providing for the maximum possible continuity of service and maintaining the integrity of the ERCOT System.
Energy Imbalance Service An Ancillary Service that is provided when a difference occurs between the scheduled and the actual delivery of energy in Real-Time.
Energy Offer Curve A proposal to sell energy at a Settlement Point at a monotonically increasing price with increasing quantity.
Energy Trade A QSE-to-QSE financial transaction that transfers responsibility for energy between a buyer and a seller at a Settlement Point.
Entity Any natural person, partnership, municipal corporation, cooperative corporation, association, governmental subdivision, or public or private organization.
ERCOT Polled Settlement (EPS) Meter Any meter polled directly by ERCOT for use in the Settlement of the market.
ERCOT Region The power region, as defined in P.U.C. SUBST. R. 25.5, Definitions, represented by the ERCOT Control Area.
ERCOT System The interconnected power system that is under the jurisdiction of the PUCT and that is not synchronously interconnected with either the Eastern Interconnection or the Western Electricity Coordinating Council.
ERCOT System Demand The sum of all power flows, in MW, on the DC Ties and from Generation Resources metered at the points of their interconnections with the ERCOT System at any given time.
ERCOT Transmission Grid All Transmission Facilities that are part of the ERCOT System.
External Load Serving Entity (ELSE) An Entity that is registered as an LSE and is either:
  1. A distribution service provider (as that term is defined in P.U.C. Subst. R. 25.5, Definitions), which includes an electric utility, a Municipally Owned Utility (MOU), or an Electric Cooperative (EC) that has a legal duty to serve one or more Customers connected to the ERCOT System but that does not own or operate Facilities connecting Customers to the ERCOT System; or
  2. The CFE.