The Holy Grail for solar energy are the development of transparent, see-through solar panels that resemble glass and can be used as windows, but at the same time convert sunlight into electricity. In a new study, published in the journal Nature Energy, researchers from Michigan State University, in the United States, have investigated the efficiency of current solar technologies, and have determined that transparent panels could be scaled-up to cover the estimated 5-7 billion square metres of glass surfaces in the United States, potentially providing around 40 percent of the country's energy needs. Similar analysis conducted by the U.S. Department of Energy last year, has estimated that rooftop solar has the potential to meet the same amount of power by using conventional panels. By these estimates, the new study suggests that the two types of technologies — running in unison — could effectively provide all of the U.S.'s power needs. To find out more check out Emergence of highly transparent photovoltaics for distributed applications.