There are at least 1.47 million solar installations of varying sizes in the 48 contiguous U.S. states, from home rooftop panels to utility-owned solar power plants. That's the conclusion of DeepSolar, a machine learning algorithm developed by researchers at Stanford University that searches satellite images for solar panels. The count is higher than some previous estimates, like the OpenPV project's count of 1.02 million installations. The researchers, led by Ram Rajagopal, associate professor of civil and environmental engineering, and Arun Majumdar, professor of mechanical engineering, trained DeepSolar on a set of 370,000 satellite images, each covering a region measuring approximately 9 square meters (100 square feet), by indicating which ones included solar panels. The machine-learning program then figured out how to identify solar panels, spotting them correctly 93 percent of the time.