Using detailed light detection and ranging data for 128 cities nationwide, along with improved data analysis methods and simulations tools, analysts at NREL have updated their estimate of total U.S. technical potential for rooftop photovoltaic systems to 1,118 GW of capacity and 1,432 TWh of annual energy generation, equivalent to 39% of nation's electricity sales. Analysis appears in "Rooftop Solar Photovoltaic Technical Potential in the United States: A Detailed Assessment."