Actually, the DoE was created for National Security with respect to nuclear weapons and nuclear power.
The Department has four overriding National Security priorities: insuring the integrity and safety of the country’s nuclear weapons; promoting international nuclear safety; advancing nuclear non-proliferation; and, continuing to provide safe, efficient, and effective nuclear power plants for the United States Navy.
The Department of Energy was formed after the oil crisis on August 4, 1977 in order to end the United States dependence on foreign oil by President Jimmy Carter’s signing of legislation, The Department of Energy Organization Act of 1977.
The United States, eager to make a nuclear bomb before any other nation, started the Manhattan Project under the eye of the U.S. Army Corps of Engineers. After the war, the Atomic Energy Commission was created to control the future of the project.
In 1974, the AEC was abolished and gave way to Nuclear Regulatory Commission, which was tasked with regulating the nuclear power industry, and the Energy Research and Development Administration, which was tasked to manage the nuclear weapon, naval reactor, and energy development programs. Only a few years after that, the Energy Crisis called attention to unifying these two groups. The Department of Energy Organization Act of 1977, which Carter signed on August 4, 1977, created the Department of Energy, which assumed the responsibilities of the Federal Energy Administration, the Energy Research and Development Administration, the Federal Power Commission, and programs of various other agencies.
The department began operations on October 1, 1977.