Learning Center

access charge: A fee levied for access to a utility's transmission or distribution system. It is a charge for the right to send electricity over another's wires and is not typically tied to the actual amount of power shipped.

acre-feet: The amount of water it takes to cover one acre to a depth of one foot. This measure is used to describe the quantity of storage in a reservoir or hydro system.  One million acre-feet (MAF) equals 504 second foot days (SFD).

administrator: The administrator of the Bonneville Power Administration (BPA). Under BPA's new corporate structure, the administrator's title is chief executive officer (CEO).

advance energy: Energy delivered at BPA's option to its Direct Service Industrial customers in lieu of restricting power at times when reservoirs are on a fixed operation. The energy is subject to return if BPA determines that firm commitments cannot be met because of advance energy deliveries.

aggregators: Brokers who seek to bring together customers to create a "load" so that they can buy power in bulk, making a profit on the sale.

alternating current (AC): An electric current that reverses direction of flow at regular intervals and has alternately positive and negative values.

anadromous fish: Fish (such as salmon and steelhead) that hatch in freshwater, migrate to the ocean, mature there, and return to freshwater to spawn.

ancillary services: Includes the provision of reactive power, frequency control and load following.

automatic generation control (AGC): Regulation of the power output of electric generators within a control area in response to changes in load, system frequency and other factors, to maintain the scheduled system frequency and interchanges with other control areas. (Automatically changing generation every 2 to 4 seconds to match the load)

average annual megawatt or average megawatt (aMW): A unit of energy output over a year that is equal to the energy produced by the continuous operation of one megawatt of capacity over a period of time. (Equal to 8,760 megawatt-hours).

average cost pricing: A pricing mechanism based on dividing the total cost of providing electricity incurred in a period by the number of units sold in the same period.

average system cost (ASC): The cost of a utility's generation and transmission system. Under the Residential Exchange provisions of the Northwest Power Act, a utility may sell power to BPA at the utility's average system cost and purchase the same amount of power back from BPA at a rate based on the costs of the Federal Base System.

avoided cost: A guideline for comparing the value of conservation and renewable resources with other resources. Literally, the cost a utility avoids by purchasing a conservation or renewable resource versus acquiring energy elsewhere.

baseload: A power plant that is planned to run continually except for maintenance and scheduled or unscheduled outages. Baseload also refers to the minimum load in a power system over a given period of time.

biomass conversion: The process by which organic materials, such as wood waste or garbage, are burned for direct energy or electrical generation, or by which these materials are converted to synthetic natural gas.

blackout: The disconnection of the source of electricity serving an area brought about by an emergency forced outage or other fault in the generation, transmission or distribution system.

British thermal unit (BTU): The amount of heat energy necessary to raise the temperature of one pound of water one degree Fahrenheit (3,412 BTUs are equal to one kilowatt-hour).

brownout: The partial reduction of electrical voltages. A brownout results in lights dimming and motor-driven devices slowing down.

bypass system: Structure in a dam that routes fish around rather than through the turbines.