The Gafanhoto power plant was the starting point for Cemig. Built by the State government in 1952, Gafanhoto Hydroelectric power plant was of great economic importance as it provided for the implementation and development of the Industrial District of Contagem, the largest industrial region in Minas Gerais.  

After that, there came the hydroelectric power plants of Itutinga, Piau, Salto Grande, Cajuru and the Três Marias Plant, a hallmark of national engineering in the construction of great dams. Its multi-purpose reservoir not only generates electric energy and allows river traffic to continue under drought conditions but also serves as a regional water supply for urban areas and irrigation.

During the 60s and with the support of both the U.N. Development Program and the World Bank, the hydroelectric potential of the state's river basins was assessed and the most feasible sites identified, which led to the construction of Jaguara, Volta Grande, São Simão, Emborcação and Nova Ponte Plants. Today, Cemig operates 48 power plants, of which 44 are hydroelectric, 3 are fuel-oil thermal plants and a small wind power plant, totaling an installed capacity of 5,704 MW.

The construction of new power plants, through consortia with other companies from the private sector is aimed at the supplying of electric energy to the country's market. The power plants of Queimado, Aimorés, Pai Joaquim and Irapé are currently under construction.