Congressional Research Service. May 30, 2012.
Every President since Richard Nixon has sought to increase U.S. energy supply diversity. In recent years, job creation and the development of a domestic renewable energy manufacturing base have joined national security and environmental concerns as rationales for promoting the manufacturing of solar power equipment in the United States. The federal government maintains a variety of tax credits, loan guarantees, and targeted research and development programs to encourage the solar manufacturing sector, and state-level mandates that utilities obtain specified percentages of their electricity from renewable sources have bolstered demand for large solar projects.
http://www.fas.org/sgp/crs/misc/R42509.pdf [PDF format, 32 pages].