Gas Turbine Plant: A plant in which the prime mover is a gas turbine. A gas turbine consists typically of an axial-flow air compressor, one or more combustion chambers, where liquid or gaseous fuel is burned and the hot gases are passed to the turbine and where the hot gases expand to drive the generator and are then used to run the compressor.

GCIM – Gas Cost Incentive Mechanism: Replaces the Reasonableness Review as a means of reviewing natural gas purchasing activities for retail core customers. The purpose of the GCIM is to provide market-based incentives to reduce the cost of gas to core customers and to provide appropriate objective standards against which to measure a utility’s performance in gas procurement and transportation functions on behalf of core customers.

Generation Company: A regulated or non-regulated entity (depending upon the industry structure) that operates and maintains existing generating plants. The generation company may own the generation plants or interact with the short-term market on behalf of plant owners. In the context of restructuring the market for electricity, the generation company is sometimes used to describe a specialized "marketer" for the generating plants formerly owned by a vertically integrated utility.

Geothermal Energy: Energy from the internal heat of the earth, which may be residual heat, friction heat, or a result of radioactive decay. The heat is found in rocks and fluids at various depths and can be extracted by drilling and/or pumping.

Geothermal Plant: A plant in which the prime mover is a steam turbine. The turbine is driven either by steam produced from hot water or by natural steam that derives its energy from heat found in rocks or fluids at various depths beneath the surface of the earth. The energy is extracted by drilling and/or pumping.

GHz – Gigahertz: A unit of frequency equal to one billion hertz (one billion cycles per second).

GIR – Gas Industry Restructuring: A long-term regulatory process, initiated in the mid-1980s by the California Public Utilities Commission, to change the fundamental structure of the state’s natural gas industry. The new structure, among other things, now allows gas customers to procure their own gas.

GO – General Order: A PUC order that sets standards, procedures, or guidelines applicable to a class of utilities, as distinguished from a decision affecting only a single utility.

Gopher: A tool used on the Internet that permits users to locate and retrieve information quickly throughout the Internet.

GPCD – Gallons per Capita per Day: The amount of water used on average by an individual each day. Total gpcd is calculated by dividing total water use in the area, including industrial and commercial uses, by the number of users. Residential gpcd is the number resulting from only considering domestic water use.

Gradient, hydraulic: The change of pressure per unit distance from one point to another in an aquifer. When an area is said to be “downgradient” it is at a lower level and water will flow in that direction.

GRC – General Rate Case: A proceeding in which the Commission takes a broad, in-depth look at a utility’s revenues, expenses, and financial outlook and considers quality of service and other factors to arrive at just and reasonable rates. These are the major regulatory proceedings that come before the Commission.

Greenhouse Effect: The increasing mean global surface temperature of the earth caused by gases in the atmosphere (including carbon dioxide, methane, nitrous oxide, ozone, and chlorofluorocarbon). The greenhouse effect allows solar radiation to penetrate but absorbs the infrared radiation returning to space.

Grid: The layout of an electrical distribution system.

Gross Generation: The total amount of electric energy produced by a generating facility, as measured at the generator terminals.

Groundwater: Subsurface water body in the zone of saturation, or more commonly, available groundwater is defined as: That portion of the water beneath the surface of the earth that can be collected with wells, tunnels, or drainage galleries, or that flows naturally to the earth’s surface via seeps or springs.

Groundwater Basin : An area enclosing a relatively distinct hydrologic body or related bodies of groundwater.

GSM - Global System for Mobile Communication: This is the current radiotelephone standard in Europe and many other countries except Japan and the U.S.

GW – Grid West: A member-based, non-stock, not-for-profit regional independent transmission organization. Grid West supervises the collective transmission facilities of its service area and is charged with nondiscriminatory coordination of market transactions, system-wide transmission planning, network reliability, and administration of the markets.

gWh – Gigawatt-hours: One billion watt-hours.