After leaving the White House to work on the Al Gore Presidential primary campaign in Washington DC, Iowa and Texas, Cargas rejoined the administration as a Special Assistant in the U.S. Department of Energy in the Office of Fossil Energy under Secretary of Energy Bill Richardson.
In 2008, Houston Mayor Bill White hired Cargas as the Senior Assistant City Attorney for Energy of the City of Houston responsible for advising the Mayor on all aspects of energy procurement and energy transactional matters.