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Idle Well: A stripper oil well that has temporarily stopped production.

Idled: Production has been stopped temporarily.

Imports (Electric Utility): Power capacity or energy obtained by one utility from others under purchase or exchange agreement.

Impoundment: A body of water confined by a dam, dike, floodgate or other artificial barrier.

Incandescent Lamp: An electric lamp in which a filament is heated by an electric current until it emits visible light.

Independent Power Producer (IPP): An IPP generates power that is purchased by an electric utility at wholesale prices. The utility then resells this power to end–use customers. Although IPPs generate power, they are not franchised utilities, or government agencies. IPPs usually do not own transmission lines to transmit the power that they generate.

Independent System Operator (ISO): A neutral operator responsible for maintaining instantaneous balance of the grid system. The ISO performs its function by controlling the dispatch of flexible plants to ensure that loads match resources available to the system.

Indigenous Energy Resources: Power and heat derived from sources native to Nebraska. These resources include oil, natural gas, geothermal, hydro, biomass, solar and wind energy. The term usually is understood to include cogeneration facilities.

Indirectly Conditioned Space: See Conditioned space, indirectly.

Industrial Sector: Manufacturing, construction, mining, agricultural, fishing and forestry establishments.

Infiltration: The uncontrolled inward leakage of air through cracks and gaps in the building envelope, especially around windows, doors and duct systems.

Infiltration Barrier: A material placed on the outside or the inside of exterior wall framing to restrict inward air leakage, while permitting the outward escape of water vapor from the wall cavity.

Infrastructure: Generally refers to the recharging and refueling network necessary to successful development, production, commercialization and operation of alternative fuel vehicles, including fuel supply, public and private recharging and refueling facilities, standard specifications for refueling outlets, customer service, education and training and building code regulations.

Injection (Petroleum): Forcing gas or water into an oil well to increase pressure and cause more oil to come to the surface. See Thermally Enhanced Oil Recovery.

In–Situ Combustion: An experimental means of recovering hard–to–get petroleum by burning some of the oil in its natural underground reservoir. Also called Fireflooding.

In–Situ Gasification: Converting coal into synthetic gas at the place where the coal is found in nature.

Insolation: The total amount of solar radiation (direct, diffuse and reflected) striking a surface exposed to the sky.

Insulation, Thermal: A material having a relatively high resistance of heat flow and used principally to retard heat flow. See R–value.

Integrated Resource Planning (IRP): A public planning process and framework within which the costs and benefits of both demand– and supply–side resources are evaluated to develop the least–total–cost mix of utility resource options. IRP has become a formal process prescribed by law in some states and under some provisions of the Clean Air Act Amendments of 1992.

Integrated Resource Planning Principals: The underlying principles of IRP can be distinguished from the formal process of developing an approved utility resource plan for utility investments in supply– and demand–side resources. A primary principle is to provide a framework for comparing a variety of supply– and demand–side and transmission resource costs and attributes outside of the basic provision (or reduction) of electric capacity and energy. These resources may be owned or constructed by any entity and may be acquired through contracts as well as through direct investments. Another principle is the incorporation of risk and uncertainty into the planning analysis. The public participation aspects of IRP allow public and regulatory involvement in the planning rather than the siting stage of project development.

Interconnection (Electric Utility): The linkage of transmission lines between two utilities, enabling power to be moved in either direction. Interconnections allow the utilities to help contain costs while enhancing system reliability.

Internal Combustion Engine: An engine in which fuel is burned inside the engine. A car's gasoline engine or rotary engine is an example of a internal combustion engine. It differs from engines having an external furnace, such as a steam engine.

Interruptable Service (Electric Utility): Electricity supplied under agreements that allow the supplier to curtail or stop service at times.

Intertie: A transmission line that links two or more regional electric power systems.

Investor–Owned Utilities: A private company that provides a utility, such as water, natural gas or electricity, to a specific service area. There are no investor–owned electric utilities in Nebraska, only publicly–owned systems. There are four investor–owned natural gas systems operating in Nebraska that provide services to some, but not all, Nebraskans:

Ion: An atom or group of atoms that is electrically charged.

IOU: An investor–owned utility. A company, owned by stockholders for profit, that provides utility services. A designation used to differentiate a utility–owned and operated for the benefit of shareholders from municipally–owned and operated utilities, regional public power districts and rural electric cooperatives and systems.

Isobutane: A normally gaseous branched–chain hydrocarbon (C4H10). It is a colorless paraffinic gas that boils at a temperature of 10.9 degrees Fahrenheit and is extracted from natural gas or refinery gas streams.