Constellation says it will supply the State Department with electricity from a wind power project planned in Pennsylvania and a $50 million solar energy project it plans to build in New Jersey.
The solar panels will be built by a federal prison service that provides job skill training to inmates and market-priced goods for the federal government.
The utility says it will deliver at estimated 120,000 megawatts a year to the State Department -- and other federal facilities -- including part of the White House campus.
President Obama has set a goal of reducing the federal government's direct greenhouse gas emissions 28 percent by 2020.
Constellation says the new contract will hep the State Department do its part to reach that target.