Glossary

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A
Ampere A unit of measure for an electrical current; the amount of current that flows in a circuit at an electromotive force of one Volt and at a resistance of one Ohm. Abbreviated as amp.
Audit (Energy) The process of determining energy consumption, by various techniques, of a building or facility.
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B
Barrel (petroleum) A volumetric unit of measure for crude oil and petroleum products equivalent to 42 U.S. gallons (306 pounds of oil, or 5.78 million Btu).
Boiler A vessel or tank where heat produced from the combustion of fuels such as natural gas, fuel oil, or coal is used to generate hot water or steam for applications ranging from building space heating to electric power production or industrial process heat.
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C
Capacitor An electrical device that adjusts the leading current of an applied alternating current to balance the lag of the circuit to provide a high power factor.
Capacity The load that a power generation unit or other electrical apparatus or heating unit is rated by the manufacture to be able to meet or supply.
Circuit A device, or system of devices, that allows electrical current to flow through it and allows voltage to occur across positive and negative terminals.
Circuit Breaker A device used to interrupt or break an electrical circuit when an overload condition exists; usually installed in the positive circuit; used to protect electrical equipment.
Combined-Cycle An electric generating technology in which electricity is produced from otherwise lost waste heat exiting from one 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.
Commissioning The process by which a power plant, apparatus, or building is approved for operation based on observed or measured operation that meets design specifications.
Conductor The material through which electricity is transmitted, such as an electrical wire, or transmission or distribution line.
Conduit A tubular material used to encase and protect one or more electrical conductors.
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D
Demand The rate at which electricity is delivered to or by a system, part of a system, or piece of equipment expressed in kilowatts, kilovoltamperes, or other suitable unit, at a given instant or averaged over a specified period of time.
Distribution System That portion of an electricity supply system used to deliver electricity from points on the transmission system to consumers.
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E
Efficacy The amount of energy service or useful energy delivered per unit of energy input. Often used in reference to lighting systems, where the visible light output of a luminary is relative to power input; expressed in lumens per Watt; the higher the efficacy value, the higher the energy efficiency.
Electric Energy The amount of work accomplished by electrical power, usually measured in kilowatt-hours (kWh).
Energy Charge That part of an electricity bill that is based on the amount of electrical energy consumed or supplied.
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F
Feeder A power line for supplying electricity within a specified area.
Fuse A safety device consisting of a short length of relatively fine wire, mounted in a holder or contained in a cartridge and connected as part of an electrical circuit. If the circuit source current exceeds a predetermined value, the fuse wire melts (i.e. the fuse 'blows') breaking the circuit and preventing damage to the circuit protected by the fuse.
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G
Generation (Electricity) The process of producing electric energy by transforming other forms of energy.
Gigawatt (GW) A unit of power equal to 1 billion Watts; 1 million kilowatts, or 1,000 megawatts.
Gigawatthour (GWh) One million kilowatt-hours.
Grid A common term referring to an electricity transmission and distribution system.
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H
Hertz A measure of the number of cycles or wavelengths of electrical energy per second.
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I
Installed Capacity The total capacity of electrical generation devices in a power station or system.
Insulator A device or material with a high resistance to electricity flow.
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J
Joule A metric unit of energy or work; the energy produced by a force of one Newton operating through a distance of one meter.
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K
Kilovolt-Ampere (kVa) A unit of apparent power, equal to 1,000 volt-amperes; the mathematical product of the volts and amperes in an electrical circuit.
Kilowatt (kW) A standard unit of electrical power equal to one thousand watts, or to the energy consumption at a rate of 1000 Joules per second.
Kilowatt-hour A unit or measure of electricity supply or consumption of 1,000 Watts over the period of one hour.
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L
Load The demand on an energy producing system; the energy consumption or requirement of a piece or group of equipment.
Load Factor The ratio of average energy demand (load) to maximum demand (peak load) during a specific period.
Load Profile or Shape A curve on a chart showing power (kW) supplied (on the horizontal axis) plotted against time of occurrence (on the vertical axis) to illustrate the variance in a load in a specified time period.
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M
Megawatt One thousand kilowatts, or 1 million watts; standard measure of electric power plant generating capacity.
Megawatt-hour One thousand kilowatt-hours or 1 million watt-hours.
Metric Ton (Tonne) A unit of mass equal to 1,000 kilograms or 2,204.6 pounds.
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N
Natural Gas A hydrocarbon gas obtained from underground sources, often in association with petroleum and coal deposits. It generally contains a high percentage of methane, varying amounts of ethane, and inert gases; used as a heating fuel.
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O
Off-Peak The period of low energy demand, as opposed to maximum, or peak, demand.
Outage The period during which a generating unit, transmission line, or other facility is out of service.
Overload To exceed the design capacity of a device.
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P
Peak Demand The maximum energy demand or load in a specified time period.
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R
Renewable Energy Energy derived from resources that are regenerative or for all practical purposes can not be depleted. Types of renewable energy resources include moving water (hydro, tidal and wave power), thermal gradients in ocean water, biomass, geothermal energy, solar energy, and wind energy.
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S
Short Circuit An electric current taking a shorter or different path than intended.
Substation An electrical installation containing power conversion (and sometimes generation) equipment, such as transformers, compensators, and circuit breakers.
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T
Transformer An electromagnetic device that changes the voltage of alternating current electricity. It consists of an induction coil having a primary and secondary winding and a closed iron core.
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.
Transmission and Distribution Losses The losses that result from inherent resistance in electrical conductors and transformation inefficiencies in distribution transformers in a transmission and distribution network.
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V
Volt A unit of electrical force equal to that amount of electromotive force that will cause a steady current of one ampere to flow through a resistance of one ohm.
Voltage The amount of electromotive force, measured in volts, that exists between two points.
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W
Watt The rate of energy transfer equivalent to one ampere under an electrical pressure of one volt. One watt equals one joule per second. It is the product of Voltage and Current (amperage).
Watt-hour A unit of electricity consumption of one Watt over the period of one hour.
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