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INCANDESCENT LIGHT An electric lamp that is evacuated or filled with an inert gas and contains a filament (commonly tungsten). The filament emits visible light when heated to extreme temperatures by electric current through it. Incandescent light bulbs are one of the most inefficient ways to light a home. They produce a great deal of heat along with the light, and use three to four times as much energy for the same light output as compact fluorescent light bulbs.

INDUCTION MOTOR (AC) A type of electric motor that requires a high surge to start, and a stable voltage supply, making it a challenge to run using a solar-electric system.

INSOLATION The amount of sunlight reaching an area. Usually expressed in watts per square meter.

INTAKE In a hydro system, the structure that receives the water and feeds it into the penstock (pipeline). Usually incorporates screening or filtering to keep debris and aquatic life out of the system.

INVERTER A device that converts DC electricity (anywhere from 12 to 600 VDC) to AC electricity (typically 120/240 VAC).

ION An electrically charged particle or molecule.

ISC See SHORT CIRCUIT CURRENT.

IV CURVE The graphical representation of the current versus the voltage of a photovoltaic cell, module, or array as the load is increased from zero voltage to maximum voltage, under standard test conditions.