1xpert/iStock via Getty Images DTE Energy (NYSE:DTE) is the largest utility in the State of Michigan, incorporated in 1995. Its four wholly-owned subsidiaries are DTE Electric (founded in 1903 as the Detroit Edison Company), DTE Gas (founded in 1849 as City of Detroit Gas), DTE Vantage, and DTE Energy Trading (started in 1998). Vantage operates renewable natural gas projects and provides energy consulting services. DTE Electric has 2.3 million customers in southeast Michigan, which includes the City of  ...