Glossary by "E"

  • 238

    Economic dispatch

    The allocation of demand to individual generating units on line to effect the most economical production of electricity.

  • 239

    Edison Electric Institute

    Acronym(s): EEI

    An association of investor-owned electric utility companies created in 1933 “to exchange information on industry developments and to act as an advocate for utilities on subjects of national interest.” The EEI acts as an information exchange for its members and a public relations voice for the electric energy industry as a whole.

    Source: ESA Technical Working Group
  • 240

    Elastic potential energy

    A form of potential energy that is stored in “elastic” materials (i.e. materials that can be stretched or compressed). So, elastic potential energy can be stored, for example, in springs, rubber bands and compressed air.

    Source: ESA Technical Working Group
  • 241


    An adjective meaning “needing electricity to operate” such as electric motor or wire. IEEE: Containing, producing , arising from, actuated by or carrying electricity.

    Source: ESA Technical Working Group
  • 242

    Electric cooperative

    Acronym(s): co-op

    A not-for-profit electric utility that is owned by the members it serves. A co-op exist solely to provide high-quality service at the lowest possible price for its customer-owners. A co-op’s profits are retained by the co-op to offset future costs and/or profit is returned to the customer-owner. Many co-ops are own T&D needed to serve member-owners though many own limited or no generation.

    Source: ESA Technical Working Group
  • 243

    Electric current

    Flow of electrons. The common metric is ampere or amp.

    Source: ESA Technical Working Group
  • 244

    Electric distribution information system

    Acronym(s): EDIS

    A computerized mapping system which tracks resources within a distribution network.

  • 245

    Electric energy time-shift

    Storage of energy during times when cost or price is low, for use or sale when the energy’s value is high.

    Source: ESA Technical Working Group
  • 246

    Electric grid

    See: Electrical utility grid

    A common term used to refer to the electric utility grid.

    Source: ESA Technical Working Group
  • 247

    Electric Reliability Council of Texas

    Acronym(s): ERCOT

    The independent system operator in Texas.

    Source: ESA Technical Working Group
  • 248

    Electric supply

    A source of electric energy and/or capacity, possibly including generation facilities and purchases.

    Source: ESA Technical Working Group
  • 249

    Electric supply resource

    A source of electricity and/or demand reduction that is included in a utility’s electric supply portfolio.

    Source: ESA Technical Working Group
  • 251

    Electric supply resources

    All generation, power purchases and load management resources that can be called upon to provide electricity to the grid.

    Source: ESA Technical Working Group
  • 252


    1. An adjective meaning “pertaining to electricity”. Electrical Engineer. 2. Related to, pertaining to or associated with electricity but not having its properties or characteristics.  

    Source: ESA Technical Working Group
  • 253

    Electrical energy

    The generation or use of electric power by a device over a period of time, expressed in kiloWatt-hours (kWh), MegaWatt-hours (MWh), or GigaWatt-hours (GWh).

  • 254

    Electrical island

    A portion of (i.e., electrical “island” within) a larger electric system that operates autonomously when the larger electric power system is not available or not operational. Traditionally electric utilities have discouraged islanded operation due to safety concerns related to exposing work persons to danger if equipment is energized during repair or maintenance.

    Source: ESA Technical Working Group
  • 255

    Electrical utility grid

    The network of generators, transformers, wires, capacitors and other equipment that comprise the physical utility electric power supply, transmission and distribution systems. Also referred to as the electric grid or just the grid.  

    Source: ESA Technical Working Group
  • 256

    Electrochemical battery

    See: Battery
    Source: ESA Technical Working Group
  • 257

    Electrochemical cell

    Devices in which oxidation-reduction (redox) reactions occur. Two types of electrochemical cells: 1. spontaneous reactions occur in galvanic (voltaic) cells and 2. nonspontaneous reactions occur in electrolytic cells. Both types contain electrodes where the oxidation and reduction reactions occur. Oxidation occurs at the electrode termed the anode and reduction occurs at the electrode called the cathode. The anode is positive (cathode is negative), because the anode attracts anions from the solution. However, the anode of a galvanic cell is negatively charged, since the spontaneous oxidation at the anode is the source of the cell’s electrons or negative charge. The cathode of a galvanic cell is its positive terminal. In both galvanic and electrolytic cells, oxidation takes place at the anode and electrons flow from the anode to the cathode.

  • 258

    Electrochemical couple

    The system of active materials within a cell that provides electrical energy storage through an electrochemical reaction.

  • 259


    An electrical conductor through which an electric current enters or leaves a conducting medium, whether it be an electrolytic solution, solid, molten mass, gas, or vacuum. For electrolytic solutions, many solids, and molten masses, an electrode is an electrical conductor at the surface of which a change occurs from conduction by electrons to conduction by ions. For gases and vacuum, the electrodes merely serve to conduct electricity to and from the medium.  

  • 261


    For electrochemical batteries; A chemical compound which, when fused or dissolved in certain solvents, usually water, will conduct an electric current. All electrolytes in the fused state or in solution give rise to ions which conduct the electric current.

    Source: BatterySpace
  • 262

    Emergency or BES emergency

    Any abnormal system condition that requires automatic or immediate manual action to prevent or limit the failure of transmission facilities or generation supply that could adversely affect the reliability of the bulk electric system.

  • 263

    Emergency rating

    The rating as defined by the equipment owner that specifies the level of electrical loading or output, usually expressed in megawatts (MW) or Mar or other appropriate units, that a system, facility, or element can support, produce, or withstand for a finite period. The rating assumes acceptable loss of equipment life or other physical or safety limitations for the equipment involved.  

  • 264

    End user

    The person or entity that uses energy, as distinct from, for example, entities that engage in wholesale energy transactions or purchases made by a landlord or other “distributor.”

    Source: ESA Technical Working Group
  • 265

    End-of-discharge voltage

    For electrochemical batteries; the voltage of the battery that has been fully discharged.

    Source: ESA Technical Working Group
  • 266

    End-point voltage

    Cell/battery voltage below which the connected equipment will not operate or below which operation is not recommended.  

  • 267


    1. Energy is the potential of a physical system to perform work.  (A common unit of work is foot-pound—the amount of energy needed to lift one pound up a distance of one foot.) Energy exists in several forms such as electromagnetic radiation (light and heat), kinetic or mechanical energy, potential energy, electric, chemical and others. Note that power is the rate at which energy is generated, transferred or used. So energy generated, transferred or used is a function of power and time. For example, power generation, transfer or use of 1 kilowatt (kW) for one hour indicates energy use of one kilowatt-hour (kWh). See also kinetic energy and potential energy. 2. The ability a physical system has to do work on other physical systems, typically measured in kWh in the electric utility context. Measured in kWh kilowatt hours as well as other units. 3. Ability to do work, force through a distance.  

    Source: ESA Technical Working Group
  • 268

    Energy balancing

    Periodic balancing of energy supply and demand between two or more entities. For example, during one 15 minute period entity 1 needs more energy than its scheduled resources can provide. So entity 1 receives the necessary energy from entity 2. During the next 15 minute period entity 1 supplies an amount of energy to entity 2 equal to the extra energy used (from entity 2) during the previous 15 minute period.

    Source: ESA Technical Working Group
  • 269

    Energy density

    The amount of energy that a storage system can store per unit volume occupied by the system.

    Source: ESA Technical Working Group
  • 270

    Energy emergency

    A condition when a Load-Serving Entity has exhausted all other options and can no longer provide its customers

  • 271

    Energy imbalance service

    An ancillary service provided via a wholesale market which operates under a tariff approved by the FERC and consistent with the mandate of FERC Order No. 2000, which requires real-time EIS and market monitoring functions. One of six ancillary services specified by the FERC under Order 888.

    Source: ESA Technical Working Group
  • 272

    Equipment rating

    The maximum and minimum voltage, current, frequency, real and reactive power flows on individual equipment under steady state, short-circuit and transient conditions, as permitted or assigned by the equipment owner.  

  • 273

    Exempt wholesale generator

    Acronym(s): EWG

    A generator of electric energy for sale exclusively to competing wholesale customers, and who is exempt from some requirements of the Public Utilities Holding Company Act of 1935. An exempt wholesale generator may sell to publicly-owned municipal utilities, but their exemption allows them to sell - or not sell - energy to whomever they choose at whatever rate they choose. The exemption applies federally, but is usually subject to approval by state and regional bodies who may override the exemption if it is felt that this is in the public interest and require a generator to sell within a certain price range or to a certain customer or group of customers.

  • 274

    Extended range electric vehicle

    Acronym(s): EREV

    An extended-range electric vehicle (EREV) operates as a battery electric vehicle for a certain number of miles. After the battery has been discharged, a gas engine powers an electric generator for several hundred miles of

  • 275


    Expenses, costs, or potential costs which are not included in cost analyses, cost/benefit studies or prices, usually because they cannot be readily quantified, determined or allocated. Typically the term externalities refer to social and environmental costs, but they can be any costs which are not incurred by the responsible party.  

    Source: ESA Technical Working Group