Glossary of Electric Utility Terms
Alternating Current (AC) - An electric current that reverses its direction of flow periodically as contrasted to direct current.
Alternative Fuels - Any non-traditional energy or fuel source. Under the Energy Policy Act of 1992 (EPAct) alternative fuels for vehicles include: methanol; dematured ethanol; mixtures containing a volume of 85 percent or more of methanol, denatured ethanol, or other alcohols with gasoline or other fuels; natural gas; liquefied petroleum gas; hydrogen; coal-derived liquid fuels; fuels derived from biological materials; electricity (including electricity from solar energy); and any other substantially non-petroleum fuel designated by the Secretary.
Ampere (amp) - The unit of measure of an electric current. It is proportional to the quantity of electrons flowing through a conductor past a given point in one second. It is analogous to cubic feet of water flowing per second. It is the unit current produced in a circuit by one volt acting across a resistance of one ohm.
Atom - The smallest particle of an element that cannot be divided or broken up by chemical means. It consists of a central core called a nucleus, which contains protons and neutrons. Electrons revolve in orbits in the region surrounding the nucleus.
Average Cost - A method of determining the cost of providing service to the various customer classes. Average cost-of-service figures may be used in setting rates. Average costs are determined with the aid of information gathered in a cost-of-service study. Average costs are total costs divided by the number of units produced. This method of costing, while distinguishing costs between different customer classes, fails to recognize that not all kilowatts and kilowatthours are produced at the same cost within one customer class. Seasonal, time-of-day and marginal cost-based rates more accurately reflect the true costs of producing each kilowatt or kilowatthour.
Back-up Power - Power which a wheeling utility must provide by contract to another utility or by virtue of its control area responsibility to a customer when that customer's normal source of power is not available.
Biomass - The amount of living matter in a given unit of the environment. A variety of organic fuel sources which can either be processed into synthetic fuels or burned directly to produce steam or electricity.
Blackout - Total loss of power to electrical eqipment, causing loss of memory and restarting.
British Thermal Unit (Btu) - The standard unit for measuring quantity of heat energy, such as the heat content of fuel. It is the amount of heat energy necessary to raise the temperature of one pound of water one degree Fahrenheit.
Brownout - A system voltage reduction in response to a shortage of power relative to demand. Although service is not disrupted completely, a brownout will cause a dimming of lights and may result in a loss of load.
Capacitor - An electrical device that maintains or increases voltage in power lines and improves the efficiency of the electrical system by compensating for inductive losses which produce wasted energy.
Capacity Factor - That ratio of the average operating load of an electric power generating unit for a period of time to the capacity rating of the unit during that period.
Carbon Dioxide (CO2) - A colorless, odorless, nonpoisonous gas normally part of the ambient air; fossil fuel combustion produces significant quantities of CO2.
Carbon Monoxide (CO) - A colorless, odorless, toxic gas produced by the incomplete combustion of carbon-containing substances. One of the major air pollutants, it is emitted in large quantities by exhaust of gasoline-powered vehicles.
Demand - That portion of the charge for electric service based upon the electric capacity (kW or KVa) consumed and billed on the basis of billing demand under an applicable rate schedule.
Energy - That portion of the charge for electric service based upon the electric energy (kWh) consumed or billed.
Circuit (Electric) - A conductor or a system of conductors through which an electric current flows or is intended to flow.
Circuit Breaker - A protective device located on an electric circuit to interrupt the flow of current at that particular point. If a transmission or distribution line or transformer experiences an electrical fault or short circuit, it can be disconnected from the rest of the system by means of a circuit breaker. The interrupting medium can be either air, oil or gas.
Classes of Electric Service
Residential - A customer, sales, and revenue classification covering electric energy supplied for residential (household) purposes. The classification of an individual customer's account where the use is both residential and commercial is based on principal use.
Other Public Authorities - A customer, sales, and revenue classification covering electric energy supplied to municipalities or divisions or agencies of federal or state governments (as ultimate customers) under special contracts or agreements or service classifications applicable only to public authorities, except such items included in the classifications Public Street and Highway Lighting, Sales to Railroads and Railways, and Sales for Resale. Excludes Department of Energy sales which are classified as Industrial.
Clean Air Act (CAA) - The primary federal law governing the regulation of emissions into the atmosphere. Originally passed in 1963, it has been amended several times with major changes occurring in 1970 and 1990. In 1970, primary responsibility for administering the CAA was given to the newly created Environmental Protection Agency. This act required promulgation and ongoing enforcement of National Ambient Air Quality Standards and National Emission Standards for Hazardous Air pollutants which limit the maximum local concentrations of various air pollutants. In addition, the act limits the amount of various pollutants that vehicles may emit. The 1990 amendments set stricter provisions for motor vehicle emissions, attainment of the national ambient air quality standards, and specific restrictions on use or emissions of chlorofluorocarbons, NOx, and sulfur dioxide (SO2). the SO2 restrictions involve a system of tradeable emissions allowances.
Coal - A black or brownish solid combustible substance formed by the partial decomposition of vegetable matter without free access of air and under the influence of moisture and often intense pressure and temperature. The rank of coal (anthracite, bituminous, subbituminous, and lignite) is determined by its heating value.
Anthracite - Hard and jet black with a high luster, it is the highest rank of coal and is mined in Northeast Pennsylvania.
Bituminous - The most common coal - soft, dense, black with well-defined bands of bright and dull material. Bituminous is ranked between anthracite and subbituminous and is mined chiefly in Kentucky, Pennsylvania, and West Virginia.
Lignite - A brownish-black coal of the lowest rank, it is mined in North Dakota, Montana and Texas.
Subbituminous - A dull black coal ranking between lignite and bituminous, it is mined chiefly in Montana and Wyoming.
Cogeneration (Cogen) - The simultaneous production of electric energy and useful thermal energy for industrial, commercial, heating or cooling purposes.
Combustion Turbine - An electric generating unit in which the prime mover is a gas turbine engine.
Conductor - A substance or body that allows an electric current to pass continuously along it.
Consumer Price Index (CPI) - Average change in prices over time in a fixed market basket of goods and services. The Bureau of Labor Statistics publishes CPIs for two population groups: (1) A CPI for all Urban Consumers (CPI-U) which covers approximately 80 percent of the total population and (2), a CPI for Urban Wage Earners and Clerical Workers (CPI-W) which covers 32 percent of the total population.
Cycle - In one cycle of alternating electric current, the current goes from zero potential or voltage to a maximum in one direction, back to zero, then to a maximum in the other direction and then back again to zero. The number of such complete cycles made each second determines the frequency of the current. (Direct current does not fluctuate from positive to negative and hence cycles or frequency can apply only to alternating current).
Degree-Day - A unit measuring the extent to which the outdoor mean (average of maximum and minimum) daily dry-bulb temperature falls below (in the case of heating) or rises above (in the case of cooling) an assumed base. The base is normally taken as 65 degrees Fahrenheit for heating and for cooling unless otherwise designated. One degree-day is counted for each degree of deficiency below (for heating) or excess over (for cooling) the assumed base, for each calendar day on which such deficiency or excess occurs.
Demand - The rate at which electric energy is delivered to or by a system, part of a system, or a piece of equipment. It is expressed in kilowatts, kilovoltamperes or other suitable unit at a given instant or averaged over any designated period of time. The primary source of "Demand" is the power-consuming equipment of the customers.
Demand Costs - Costs that are related to and vary with power demand (i.e., kW), such as fixed production costs, transmission costs, and a portion of distribution costs.
Demand-Side Management (DSM) - The planning, implementation, and monitoring of utility activities designed to influence customer use of electricity in ways that will produce desired changes in a utility's load shape (i.e., changes in the time pattern and magnitude of a utility's load). Utility programs falling under the umbrella of DSM include: load management, customer generation, and innovative rates. DSM includes only those activities that involve a deliberate intervention by the utility to alter the load shape. These changes must produce benefits to both the utility and its customers.
Distribution - The act or process of delivering electric energy from convenient points on the transmission or bulk power system to consumers. Also a functional classification relating to that portion of utility plant used for the purpose of delivering electric energy from convenient points on the transmission system to consumers, or to expenses relating to the operation and maintenance of distribution plant.
DPU - Department of Public Utilities
DSM - Demand Side Management
ECT - Enron Capital & Trade Resources
Edison Electric Institute (EEI) - The association of electric companies. Organized in 1933 and incorporated in 1970, EEI provides a principal forum where electric utility staff exchange information on developments in their business, and maintain liaison between the industry and the federal government. Its officers act as spokesmen for investor-owned electric utility companies on subjects of national interest.
EIS - Environmental Impact Statement
Electric and Magnetic Fields (EMF) - When energy flows through an energized conductor, two types of fields are created - electric and magnetic. The electric field is created by the voltage impressed on the conductors. The magnetic field is created by current in the conductors. Electric and magnetic fields surround the conductors. Electric and magnetic fields are frequently pictured as "lines of force" emanating in the vicinity of the transmission line. Electric fields are measured in units of volts per meter (v/m) or kilovolts per meter (kV/m). Magnetic fields are measured in units called gauss (G) or tesla (T). One gauss in equal to 10,000 tesla. Transmission line electric and magnetic fields are not constant or "static" fields. The fields created by alternating current (AC) voltages cycle above and below zero at the power frequency. North American AC power lines operate at 60 cycles per second (noted as Hertz or Hz). Voltage, current, and electric and magnetic fields each alternate at this frequency.
Electric Distribution - The delivery of electric energy to customers on the distribution system. Electric energy is carried at high voltages along transmission lines. For consumers needing lower voltages, it is reduced in voltage at a substation and delivered over primary distribution lines extending throughout the area where the electricity is distributed. For users needing even lower voltages, the voltage is reduced once again by a distribution transformer or a line transformer. At this point it changes from primary to secondary distribution voltage.
Electric Power Generation - The large-scale production of electricity in a central plant. A power plant consists of one or more units. Each unit includes an individual turbine generator. Turbine generators (turbines directly connected to electric generators) use steam, wind, hot gas or falling water to generate power.
Electric Space Heating - Space heating of a dwelling or business establishment or other structure using permanently installed electric heating as the principal source of space heating throughout the entire premises.
Electrification - The term describing emerging electric technologies such as electric vehicles, industrial process heating, and automation. These technologies have the potential for increasing the productivity, contributing to strategic load growth, or facilitating strategic conservation, peak clipping or load shifting. Examples include robotics and industry automation, microwave heating and drying, and freeze concentration of solutions.
Electron - An elementary particle with a unit negative charge. Electrons surround the positively charged nucleus and determine the chemical properties of the atom.
Energy Audit - A review of the customer's electricity and/or gas usage often including recommendations to alter the customer's electric demand or reduce energy usage. An audit usually includes a visit to the customer's facility.
Energy Efficiency Ratio (EER) - A figure of merit of air conditioning or refrigeration performance. The relative efficiency of an appliance in converting primary energy (e.g., electricity) to useful work (such as for cooling in the case of air conditioners) at the rated condition. EER (Btu/kWh) is the Btu per hour output provided by the unit, divided by the watts of electrical power input. The larger the EER, the more efficient the unit.
Environmental Protection Agency (EPA) - A federal agency created in 1970 to permit coordinated and effective governmental action for protection of the environment by the systematic abatement and control of pollution through integration of research monitoring, standard setting, and enforcement activities.
EPACT - Energy Policy Act of 1992.
FERC - Federal Energy Regulatory Commission.
Fossil Fuel Plant - A plant using coal, oil, gas and other fossil fuel as its course of energy.
FPA - Federal Power Act.
Giga - A prefix used to denotes 1,000,000,000 units (109 ).
Gigawatt (GW) - One gigawatt equals 1 billion watts, 1 million kilowatts or 1 thousand megawatts.
Gigawatthour (GWh) - One gigawatthour equals one billion watthours.
Ground - A connection from an electrical circuit to the earth for safety purposes.
Heat Rate - A measure of generating station thermal efficiency, generally expressed in Btu per net kilowatthour. It is computed by dividing the total Btu content of fuel burned for electric generation by the resulting net kilowatthour generation.
Investor-Owned Electric Utilities - Those electric utilities organized as tax-paying businesses usually financed by the sale of securities in the free market, and whose properties are managed by representatives regularly elected by their shareholders. Investor-owned electric utilities, which may be owned by an individual proprietor or a small group of people, are usually corporations owned by the general public.
IOU - Investor Owned Utility.
IPP - Independent Power Producer.
Isolation Transformer - An electrical device designed to reduce electrical noise and interference.
Kilo - A prefix used to denote 1,000 units (103).
Kilovar (kvar) - 1,000 reactive voltamperes.
Kilovolt (kV) - The unit of electric potential equal to 1,000 volts (defined herein).
Kilowatt (kW) - One kilowatt equals 1,000 watts (defined herein).
Kilowatthour (kWh) - The basic unit of electric energy equal to one kilowatt of power supplied to or taken from an electric circuit steadily for one hour. One kilowatthour equals 1,000 watthours.
Kilowatthours Per Capita - Net Generation in the United States divided by national population, or the corresponding ratio for any other area.
kWh - Kilowatt hour.
Least Cost Alternatives - The lowest cost option for providing for incremental demands. In least cost planning to serve electric demands, the least cost alternatives are often construed broadly to include demand-side management as well as various generation and purchased power options.
Line Conditioner - An electrical device designed to reduce electrical noise and provide constant output voltage.
Load - Any electrical device that uses power supplied by the source.
Load Factor - The ratio of the average load in kilowatts supplied during a designated period to the peak or maximum load in kilowatts occurring in that period. Load factor, in percent, also may be derived by multiplying the kilowatthours in the period by 100 and dividing by the product of the maximum demand in kilowatts and the number of hours in the period.
Loop - An electrical circuit that provides two sources of power to a load or substation so that if one source is deenergized the remaining source continues to provide power.
Market-Based Rates - Rates for service that are established through individual negotiations between the buyer and seller; i.e., rates for utility service that are not established by a regulator. FERC has increasingly allowed wholesale generators to charge market-based rates when they can show that they do not have market power.
Mega - A prefix used to denote 1,000,000 units (106).
Megawatt (MW) - One megawatt equals one million watts.
Mill - One mill is equal to one-tenth of a cent.
Milli - A prefix that divides a basic unit by 1,000.
NERC - North American Electric Reliability Council.
NOPR - Notice of Proposed Rulemaking
NRC - Nuclear Regulatory Commission.
Nuclear Energy - Energy produced in the form of heat during the fission process in a nuclear reactor. When released in sufficient and controlled quantity, this heat energy may be used to produce steam to drive a turbine-generator and thus be converted to electrical energy.
Nuclear Power - Power released in exothermic (a reaction which gives off heat) nuclear reactions which can be converted to electric power by means of heat transformation equipment and a turbine-generator unit.
NUG - Non-Utility Generator.
Ohm - The unit of measurement of electrical resistance. It is that resistance through which a difference of potential, or electromotive force, of one volt will produce a current of one ampere.
PBR - Performance based rates.
Power Conditioner - Any device whose main function is to provide acceptable electrical power to the load it is protecting.
Power Factor - The ratio of real power (kW) to apparent power (kVA) at any given point and time in an electrical circuit. Generally, it is expressed as a percentage ratio.
Power Pool - Two or more interconnected electric systems planned and operated to supply power in the most reliable and economical manner for their combined load requirements and maintenance programs.
Power Surge - A sudden change in an electrical system's voltage that is capable of damaging electrical equipment. The most severe surges are caused by lightning.
Proton - An elementary nuclear particle with a positive electric charge located in the nucleus of an atom.
PSC - Public Service Commission.
PUC - Public Utilities Commission.
PUHCA - Public Utility Holding Company Act of 1935.
PURPA - Public Utility Regulatory Policy Act of 1978.
QF - Qualifying Facility.
R-Value - In thermal insulation, the thermal resistance of insulation materials or constructions.
Rate Base - The value established by a regulatory authority, upon which a utility is permitted to earn a specified rate of return. Generally, this represents the amount of property used and useful in public service and may be based on the following values or combinations thereof; fair value, prudent investment, reproduction cost, or original cost; and may provide for the inclusion of cash working capital, Construction Work in Progress, Materials and Supplies, and deductions for: Accumulated Provision for Depreciation, Customer Advances for Construction, and Accumulated Deferred Income Taxes and Accumulated Deferred Investment Tax Credits.
Rate Class - A group of customers identified as a class and subject to a rate different from the rates of other groups. See also Classes of Electric Service.
Reliability - The guarantee of system performance at all times and under all reasonable conditions to assure constancy, quality, adequacy and economy of electricity. It is also the assurance of a continuous supply of electricity for customers at the proper voltage and frequency.
Renewable Energy - Any source of energy that is continually available or that can be renewed or replaced. Examples include wind, solar, geothermal, hydro, photovoltaic, wood and waste. Nonrenewable energy sources include coal, oil, and gas which all exist in finite amounts.
Residential with Electric Space Heating - A subdivision of the residential classification that includes those customers who use electricity as the principal source of space heating throughout the entire premises from permanently installed electric heating equipment.
Sag - A period of lower than normal voltage, causing motor heating and disk drive problems.
Seasonal Energy Efficiency Ratio (SEER) - Standard measurement of the overall efficiency of a heat pump or air conditioner during the cooling season. It is the total season heat removed (Btu) divided by the total electrical energy input (watthours) during the same period. The larger the SEER, the more efficient the unit.
Service Drop - The overhead conductors between the electric supply, such as the last pole, and the building or structure being served.
Service Entrance - The equipment installed between the utility's service drop, or lateral, and the customer's conductors. Typically consists of the meter used for billing, switches and/or circuit breakers and/or fuses, and a metal housing.
Static - Electrical charge that builds up due to friction between two materials.
Summer Peak - The greatest load on an electric system during any prescribed demand interval in the summer (or cooling) season, usually between June 1 and September 30.
Substation - An assemblage of equipment for the purposes of switching and/or changing or regulating the voltage of electricity. Service equipment, line transformer installations, or minor distribution and transmission equipment are not classified as substations. See also Switching Station.
Surge - A period of higher than normal voltage, causing incandescent lights to burn out and other problems.
Surge Arrester - A device which protects lines and equipment against voltage surges caused by lightning or abnormal system conditions which can damage cable or equipment insulation. The surge arrester is connected from the line to ground to provide a conducting path. This limits the voltage on lines or equipment and dissipates excess energy harmlessly.
Switching Station - An assemblage of equipment for the sole purpose of tying together two or more electric circuits through switches or circuit breakers, selectively arranged to permit a circuit to be disconnected in an emergency, or to change the electric connections between the circuits. A type of substation.
Tariff Schedule - A document filed with the regulatory authority(s) specifying lawful rates, charges, rules and conditions under which the utility provides service to the public.
Therm - A unit of the heat content of gas equal to 100,000 Btu.
Thermal - A term used to identify a type of electric generating station, capacity, capability, or output in which the source of energy for the prime mover is heat.
Thermal Energy Storage - Storage of energy produced during one period that is used for heating or cooling during a later period. For example, chilled water may be produced electrically and later used to cool buildings, or solar energy may be used to produce hot water during the day that is used for heating at night. Other types of thermal storage might use ground, rock, or other materials to store energy.
Three-Phase Power Supply - Electric energy that is transmitted by three or four wires to the customer. Relatively high voltage customers usually receive three-phase power.
Transformer - An electromagnetic device for changing the voltage level of alternating-current electricity.
Transient/Spike - A high-voltage, extremely short and fast electrical pulse. These pulses can destroy electronic equipment instantly or over a period of time.
Transmission - The act or process of transporting electric energy in bulk from a source or sources of supply to other principal parts of the system or to other utility systems. Also a functional classification relating to that portion of utility plant used for the purpose of transmitting electric energy in bulk to other principal parts of the system or to other utility systems, or to expenses relating to the operation and maintenance of transmission plant.
Transmission Access - The ability of third parties to make use of transmission facilities owned by others (wheeling utilities) to deliver power to another utility.
Transmission Grid - An interconnected system of electric transmission lines that allows power to move from any point to another over multiple paths.
Turbine - A part in some electric generators that is spun by a force of energy (e.g., air, water, steam, or a combustion engine) in order to turn the generator. It generally consists of a series of curved vanes emanating from an axis that is turned by forcing a fluid past the vanes emanating from an axis that is turned by forcing a fluid past the vanes.
Unbundling - Selling various component parts of a product or service separately, usually at a price that reflects costs for only that component of the product or service. See also Functional Unbundling.
UPS - An acronymn for Uninterruptible Power Supply, a type of battery backup system designed to provide continuous power to critical electrical loads.
Utility Plant - All equipment used for the generation, transmission, and distribution of electricity, or an account in which record is kept of this equipment. Includes Plant in Service, Purchased or Sold, in Process of Reclassification, Leased to Others, Held for Future Use, Under Construction, and Acquisition Adjustments and Adjustment Accounts, without deduction of Accumulated Provision for Depreciation and Amoritization.
Value of Service - A utility pricing concept in which the usefulness or necessity of a service to a customer group replaces or supplements cost factors as a major influence on the rates charged to the group. In ratemaking, this means that the price charged reflects the service's value to the customer rather than its cost to the producer. Value of service need not equal the cost of service.
Var - The unit of reactive power. For a two-wire circuit, the product of the voltage times the current times the sine of the angular phase difference by which the voltage leads or lags the current. Vars and watts combine in a quadrature relationship to form voltamperes.
Volt - The unit of electromotive force or electric pressure analogous to water pressure in pounds per square inch. It is the electromotive force which, if steadily applied to a circuit having a resistance of one ohm, will produce a current of one ampere.
Voltage of a Circuit - The electric pressure of a circuit in an electric system measured in volts. It is generally a nominal rating based on the maximum normal effective difference of potential between any two conductors of the circuit.
Voltage Regulator - An electrical device that regulates voltage on distribution lines. It automatically raises and lowers the voltage to maintain required voltage levels for service.
Voltampere (VA) - The basic unit of Apparent Power. The voltamperes of an electric circuit is the mathematical product of the volts and amperes of the circuit. The practical unit of Apparent Power is Kilovoltampere (kVA), which is 1,000 voltamperes.
Watt - The electrical unit of real power or rate of doing work. The rate of energy transfer equivalent to one ampere flowing due to an electrical pressure of one volt at unity power factor. One watt is equivalent to approximately 1/746 horsepower, or one joule per second.
Watthour - The total amount of energy used in one hour by a device that requires one watt of power for continuous operation. Electric energy is commonly sold by the kilowatthour (defined herein).
Weatherization - A set of measures designed to reduce heat gain and/or heat loss (and thereby energy consumption). Common weatherization measures are weather stripping, ceiling and wall insulation, and storm windows and doors. Many utilities operate weatherization programs offering incentives such as low interest loans or rebates for these installations.
Winter Peak - The greatest load on an electric system during any prescribed demand interval in the winter (or heating) season, usually between December 1 of a calendar year and March 31 of the next calendar year.
Source: Edison Electric Institute