Solar radiation levels in the Southwest are some of the best in the world, and the BLM manages more than 20 million of public lands with excellent solar potential in 6 states: California, Nevada, Arizona, New Mexico, Colorado and Utah. State renewable energy portfolios, investment tax credits for solar energy projects, volatile oil prices, and international concern about global warming have all contributed toward public and industry interest in utility-scale solar energy development. Solar energy projects can provide significant amounts of electricity while emitting virtually no greenhouse gases, but they require large areas of relatively flat land, and some technologies use substantial amounts of water—a scare commodity in the arid climates where the solar resources are the best. At this time, there are about 80 projects, totaling 685,000 acres, proposed on public land primarily in Arizona, California, and Nevada.