The California power grid is a network of long-distance, high-voltage transmission lines and substations that carry bulk electricity to local utilities for distribution to their customers. The mission of the Cal-ISO is to safeguard the reliable delivery of electricity and ensure equal access to the power grid.

Cal-ISO controls 75 percent of California's power grid, transmission systems formerly operated by the three investor-owned utilities in the state.

The Cal-ISO controlled portion of the Grid covers 124,000 square miles or three-quarters of the state.

164-billion kilowatt hours of electricity will be delivered each year, enough to serve the annual energy needs of 27 million Californians.

Power plants meeting up to 45,000 megawatts of peak demand are connected to the Cal-ISO grid, making the control area the second largest in the U.S. (Pennsylvania-New Jersey-Maryland Interconnection is the largest) and the fifth largest in the world.

Part of Cal-ISO's commitment to reliability requires a transmission planning role. Cal-ISO will plan grid enhancements to meet its high standards for reliability, at a minimum cost to consumers.

Transmission owners (investor-owned utilities) will file annual transmission expansion plans to accommodate the state's growing electricity needs. The Cal-ISO will review and either approve or make recommendations regarding the proposed additions. Recommendations that are not accepted will proceed to dispute resolution.

As part of a Coordinated Planning Process, the Cal-ISO will work with Regional Transmission Groups (RTG) and the Western Systems Coordinating Council (WSCC) to ensure expansion projects do not negatively impact the regional grid and transmission owners in other states.