Glossary of Electric Terms
Below are general definitions to terms frequently used in the electric utility industry. These electricity terms and others are located on the U.S. Energy Information Administration (EIA) Web site. You can also visit our Electrical Safety World site for kids, teachers and the general public.
Base load: The minimum amount of electric power delivered or required over a given period of time at a steady rate.
Base Rate: That portion of the total electric rate covering the general costs of doing business unrelated to fuel expenses
Btu (British Thermal Unit): A standard unit for measuring the quantity of heat energy equal to the quantity of heat required to raise the temperature of 1 pound of water by 1 degree Fahrenheit.
Circuit: A conductor or a system of conductors through which electric current flows.
Combined Cycle: An electric generating technology in which electricity is produced from otherwise lost waste heat exiting from one or more gas (combustion) turbines. The exiting heat is routed to a conventional boiler or to a heat recovery steam generator for utilization by a steam turbine in the production of electricity. This process increases the efficiency of the electric generating unit.
Commercial Operation: Commercial operation begins when control of the loading of the generator is turned over to the system dispatcher.
Deregulation: The elimination of regulation from a previously regulated industry or sector of an industry.
Distribution: The delivery of electricity to retail customers (including homes, businesses, etc.).
Distribution System: The portion of an electric system that is dedicated to delivering electric energy to an end user.
Generation: The process of producing electricity by transforming other forms of energy such as steam, heat or falling water. Also, the amount of electricity produced, expressed in kilowatt-hours (kWh) or megawatt-hours (MWh).
Generator: A producer of electricity, both literally and figuratively
Independent Power Producers: Entities that are also considered nonutility power producers in the United States. These facilities are wholesale electricity producers that operate within the franchised service territories of host utilities and are usually authorized to sell at market-based rates. Unlike traditional electric utilities, Independent Power Producers do not possess transmission facilities or sell electricity in the retail market.
Kilowatt (kW): One thousand watts.
Kilowatthour (kWh): One thousand watthours.
Megawatt (MW): One million watts.
Megawatthour (MWh): One million watthours.
Outage: The period during which a generating unit, transmission line, or other facility is out of service.
Regional Transmission Organization: A utility industry concept that the Federal Energy Regulatory Commission embraced for the certification of voluntary groups that would be responsible for transmission planning and use on a regional basis.
Substation: Facility equipment that switches, changes, or regulates electric voltage.
Transformer: An electrical device for changing the voltage of alternating current.
Transmission: The movement or transfer of electric energy over an interconnected group of lines and associated equipment between points of supply and points at which it is transformed for delivery to consumers, or is delivered to other electric systems. Transmission is considered to end when the energy is transformed for distribution to the consumer.
Transmission System (Electric): An interconnected group of electric transmission lines and associated equipment for moving or transferring electric energy in bulk between points of supply and points at which it is transformed for delivery over the distribution system lines to consumers, or is delivered to other electric systems.
Wholesale Power Market: The purchase and sale of electricity from generators to resellers (who sell to retail customers), along with the ancillary services needed to maintain reliability and power quality at the transmission level.
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