The ISO grid
The ISO manages the flow of electricity for about 80 percent of California and a small part of Nevada, which encompasses all of the investor-owned utility territories and some municipal utility service areas. There are some pockets where local public power companies manage their own transmission systems.
The ISO is the largest of about 38 balancing authorities in the western interconnection, handling an estimated 35 percent of the electric load in the West. A balancing authority is responsible for operating a transmission control area. It matches generation with load and maintains consistent electric frequency of the grid, even during extreme weather conditions or natural disasters.