Direct Normal (DNI) solar radiation (kWh/m2/day) for the Southwestern USA, showing the most suitable areas for large-scale Concentrated Solar Power (CSP) development. Data was filtered to exclude areas off-limits to development, lands with slopes >5%, and areas with <5 kWh/m2/day solar power prospects. More information can be found at http://www.nrel.gov/csp/modeling_analysis.html