A system of interconnected generating facilities, transmission corridors and power lines that provide energy to a group of customers. These terms can refer to anything from a network that serves a single suburb or section of a city to a nation's entire power distribution system. Typically "grid" refers only to the high-voltage transmission network that transports large volumes of energy from production facilities to urban areas, industrial sites and end-use customers. "The grid" usually refers to the regional grids that serve the continental United States.

While individual companies may own or control parts of a national, regional or municipal grid, access to the grid comes with responsibilities as well as benefits. As an example, grid access allows owners of distribution infrastructure to acquire energy from many competing producers, but fair treatment must be given to customers in return for this right.

The US' national energy grid is divided into three discrete sections: East, West, and Texas. Each of these regional grids are electrically isolated so that problems in one grid can't affect another. Approximately 140 coordinated control centers manage energy flow within these three regional grids to insure that blackouts can be limited to relatively small service areas. Within these three regions, grids or sections of grids may be owned or controlled by transmission companies (TRANSCOs), dedicated companies who assume responsibility for grid management (GRIDCOs) or local/regional utilities.

While the grid is designed to function as a network and has web-like characteristics similar to the Internet, network usually refers only municipal/regional grids within the three main regional grids, or to specific sections of the grid.

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