Midcontinent Independent System Operator

The Midcontinent Independent System Operator (MISO) was established in 1998 as Midwest Independent Transmission System Operator, Inc., an independent and member-based non-profit organization, and was approved as the nation's first RTO by FERC in 2001. The organization is headquartered in Carmel, Indiana with operation control centers in Carmel, Eagan, Minnesota, and Little Rock, Arkansas.

MISOs members include 54 transmission owners with more than 75,000 miles of transmission lines. Members include investor-owned utilities, public power utilities, and cooperatives, such as: Entergy, AES Indiana, International Transmission Company, Great River Energy, Xcel Energy, and City Water Light and Power.

MISO began its operation on "Day 1", a development phase between 1998 and 2005. Throughout this period, the company initiated and built up transmission services to increase grid reliability. MISO was established as an ISO in 1998 after voluntary discussions led to its formation. One year later, the first board of directors was elected. By the end of 2000, the organization had more than 70 employees. In 2001, FERC approved MISO as the nation's first RTO.

In 2005, MISO announced the opening of the MISO Energy Markets. The new services ushered in MISO's "Day 2" development phase, providing a wholesale electricity market that settles $2 billion in transactions each month. During this period, MISO grew its employee base to more than 600 staff, and moved the corporate headquarters and operations center under one roof in Carmel, Indiana.

In addition to Day-Ahead and Real-Time markets, MISO operates an ancillary services market that began on January 6, 2009. This market provides energy and operating reserves and regulation and response services supporting reliable transmission services.

The name was changed from Midwest Independent Transmission System Operator, Inc. to Midcontinent Independent System Operator in April 2013.

In December 2024, the MISO board of directors approved a transmission plan calling for a 765-kV transmission “backbone” in the area served, assisting in managing power load increases, changing generation resources and reacting to adverse weather. The estimated investment for the project is $30 billion (US) and, with regulatory review and approval, will be operational from 2032 to 2034. Long range net benefits are projected at $23 billion to $72 billion over 20 years.

Technology

MISO uses a computer model called a State Estimator that analyzes real-time conditions of the MISO power grid. The system has been in operation since December 31, 2003. It serves as the primary management tool for the reliability of transmission facilities throughout the organization's footprint. The State Estimator is one of the world's largest computer systems and provides 303,800 data points that are updated every 5 seconds.

Operations

As the primary RTO in the Midwest and South United States, MISO carries out operational responsibilities to maintain energy flow.

Grid management and reliability

Data is evaluated by reliability coordinators and reliability analysts, monitoring the grid 24/7. Projecting power movement in real-time, MISO's control room staff monitors and manages activity on the electric transmission system.

MISO performs regional planning in accordance with FERC principles. As of 2015 MISO infrastructure planning had four primary objectives: