Glossary of electric industry, energy & cooperative terms

P

Patronage Capital
Annual revenue received above the cost of operations in a cooperative utility, assigned back to a member/consumer.

Peak Demand
The greatest demand placed on an electric system; measured in kilowatts or megawatts; also, the time of day or season of the year when that demand occurs.

Peak Load
The maximum demand for electric power that determines the generating capacity required by a utility. More generally, it is the maximum load consumed or produced over a stated period of time.

Peak Load Plant
A plant usually housing old, low-efficiency steam units; gas turbines; diesels; or pumped-storage hydroelectric equipment normally used during the peak-load periods.

Peak-Load Pricing
A system of charging higher rates for power used during high-use periods to discourage use at those times and reduce a system’s peak demand.

Peak-Shaving Plant
A power plant designed to operate during the system’s high-use period to reduce power supply shortages and demand charges.

Peaking Capacity
Capacity of generating equipment normally reserved for operation during the hours of highest daily, weekly, or seasonal loads. Some generating equipment may be operated at certain times as peaking capacity and at other times to serve loads on an around-the-clock basis.

Peaking Unit
A generation unit operated to provide capacity during times of maximum electricity demands. Peaking units are usually operated for short periods of time because they are the most expensive to run, can have a greater environmental impact or are not designed for long periods of operation. Nationwide, peaking units are usually oil- or gas-fired thermal generation units with lower capital costs than base-load or intermediate-load units. Peakers start producing electricity quickly and are used when all other units and energy sources are operating at maximum capabilities during peak hours or during unforeseen service disruptions.

Percent Difference
The relative change in a quantity over a specified time period. It is calculated as follows: the current value has the previous value subtracted from it; this new number is divided by the absolute value of the previous value; then this new number is multiplied by 100.

Petroleum
A mixture of hydrocarbons existing in the liquid state found in natural underground reservoirs, often associated with gas. Petroleum includes fuel oil No. 2, No. 4, No. 5, No. 6; topped crude; Kerosene; and jet fuel.

Petroleum (Crude Oil)
A naturally occurring, oily, flammable liquid composed principally of hydrocarbons. Crude oil is occasionally found in springs or pools but usually is drilled from wells beneath the earth's surface.

Photovoltaics
Technology that produces electric power directly from sunlight. A common application is in solar-powered pocket calculators, but various equipment remote from electric distribution lines also uses the technology.

Planned Generator
A proposal by a company to install electric generating equipment at an existing or planned facility or site. The proposal is based on the owner having obtained (1) all environmental and regulatory approvals, (2) a signed contract for the electric energy, or (3) financial closure for the facility.

Plant
A facility at which are located prime movers, electric generators, and auxiliary equipment for converting mechanical, chemical, and/or nuclear energy into electric energy. A plant may contain more than one type of prime mover. Electric utility plants exclude facilities that satisfy the definition of a qualifying facility under the Public Utility Regulatory Policies Act of 1978.

Plant Use
The electric energy used in the operation of a plant. Included in this definition is the energy required for pumping at pumped-storage plants.

Plant Use Electricity
The electric energy used in the operation of a plant. This energy total is subtracted from the gross energy production of the plant; for reporting purposes the plant energy production is then reported as a net figure. The energy required for pumping at pumped-storage plants is, by definition, subtracted, and the energy production for these plants is then reported as a net figure.

Power
The rate at which energy is transferred. Electrical energy is usually measured in watts. Also used for a measurement of capacity.

Power Broker
Entities that facilitate transactions between buyers and sellers of electricity at wholesale. Unlike power marketers they do not "take title" to electricity.

Power Exchange
The entity that will establish a competitive spot market for electric power through day- and/or hour-ahead auction of generation and demand bids.

Power Exchange Generation
Generation being scheduled by the power exchange.

Power Exchange Load
Load that has been scheduled by the power exchange and which is received through the use of transmission or distribution facilities owned by participating transmission owners.

Power Factor
The ratio of active power (watts) to the apparent power (kilovolt-amperes) used by an electrical device in an alternating current (AC) circuits. When the active power consumed (watts) is divided by the product of voltage (volts) times current (amperes), and the quotient is multiplied by 100, the result equals the power factor.

Power Factor Adjustment
A bill adjustment that accounts for the electric current utilities must produce for large and medium power user classes, but which is not actually put to any useful purpose. This extra current, while serving no useful purpose, still requires capacity from the electric system. Reducing the useless current helps to reduce unnecessary investment required to provide electric service and minimize heating losses in utility lines and equipment.

Power Marketers
Business entities engaged in buying, selling, and marketing electricity. Power marketers do not usually own generating or transmission facilities. Power marketers, as opposed to brokers, take ownership of the electricity and are involved in interstate trade. These entities file with the Federal Energy Regulatory Commission for status as a power marketer.

Power Plant
A station containing one or more electric generation units. The plant’s capacity is the sum of the capacities of each generating unit.

Power Pool
Two or more interconnected electric utility transmissions and distribution systems that are operated in an integrated manner. Utilities establish power pools to handle the combined load requirements, including maintenance of the utilities' systems, thereby enhancing the reliability and economic distribution of electricity through the region.

Preference Principle
Legislative requirement giving non-profit consumer-owned electric systems first purchase rights to federal hydroelectric power generated on the nation’s rivers and streams. Short term is Preference, acceptable on second reference.

Price
The amount of money or consideration-in-kind for which a service is bought, sold, or offered for sale.

Prime Mover
The engine, turbine, water wheel, or similar machine that drives an electric generator; or, for reporting purposes, a device that converts energy to electricity directly (e.g., photovoltaic solar and fuel cell(s)).

Profit
The income remaining after all business expenses are paid.

Public Authority Service to Public Authorities
Public authority service includes electricity supplied and services rendered to municipalities or divisions or agencies of State or Federal governments, under special contracts or agreements or service classifications applicable only to public authorities.

Public Street and Highway Lighting
Public street and highway lighting includes electricity supplied and services rendered for the purposes of lighting streets, highways, parks, and other public places; or for traffic or other signal system service, for municipalities, or other divisions or agencies of State or Federal governments.

Pumped-Storage Hydroelectric Plant
A plant that usually generates electric energy during peak-load periods by using water previously pumped into an elevated storage reservoir during off-peak periods when excess generating capacity is available to do so. When additional generating capacity is needed, the water can be released from the reservoir through a conduit to turbine generators located in a power plant at a lower level.

Purchased Power Adjustment
A clause in a rate schedule that provides for adjustments to the bill when energy from another electric system is acquired and it varies from a specified unit base amount.

Pure Pumped-Storage Hydroelectric Plant
A plant that produces power only from water that has previously been pumped to an upper reservoir.

Public Utility Regulatory Policies Act (PURPA)
The Public Utility Regulatory Policies Act of 1978, passed by the U.S. Congress. This statute requires States to implement utility conservation programs and create special markets for co-generators and small producers who meet certain standards, including the requirement that States set the prices and quantities of power the utilities must buy from such facilities. PURPA requires the nation's electric utilities to provide open access to transmission lines, for use by independent power producers and non-utility generators. It also requires utilities to produce excess power produced by cogeneration facilities. It was enacted in 1978 during the energy crisis brought on by the Arab Oil Embargo.

Q

Qualifying Facility (QF)
A cogeneration or small power production facility that meets certain ownership, operating, and efficiency criteria established by the Federal Energy Regulatory Commission (FERC) pursuant to the Public Utility Regulatory Policies Act (PURPA).

Back to top

Page last updated: Monday, October 24, 2011