What are Regional Transmission Organizations (RTOs) and Independent System Operators (ISOs)?

In the United States, wholesale electricity markets are run by 7 grid operators known as Regional Transmission Organizations (RTOs) and Independent System Operators (ISOs). RTOs and ISOs are sometimes compared to air traffic controllers—they coordinate, control, and monitor the electric grid across many states (such as PJM Interconnection and ISO-New England) or in just one state (such as the New York Independent System Operator, the Electric Reliability Council of Texas, and the California ISO). Other operators include the Midcontinent Independent System Operator (MISO) and the Southwest Power Pool (SPP).