The complex US grid

The American power grid is the world’s largest and most complex system of transmission, distribution and generation, providing 11GWh of electricity to consumers every day.

While it functions reliably and safely, and utilities have made many upgrades, the infrastructure design is largely from the 1950s. This limits its functionality and ability to take advantage of 21st-century renewables opportunities.

The transmission network has more than 716,000km of high-voltage (above 100kV) lines, most of which are owned by hundreds of utilities within defined service territories. Independent transmission companies control most of the rest. The network is open access to allow non-utility “merchant” generating plants to deliver and sell power to wholesale customers.

It consists of three major alternating current (AC) interconnections: east and west (divided by the Rocky Mountains) and Texas. These systems largely operate independently of each other, but have limited links between them.

Tres Amigas, a private company, is proposing a common interconnection in eastern New Mexico that would act as the nation’s first renewable-energy market hub. Utilities and transmission firms would be able to connect to the so-called “superstation”, and buy and sell green power from and to each of the three grids.