The U.S. solar industry is on course for a new growth record in 2015, according to a new report that finds that solar photovoltaic installations now exceed 20 gigawatts in capacity and could surpass an unprecedented 7 gigawatts this year alone across all segments. A gigawatt is equivalent to 1 billion watts and can power some 164,000 homes, according to the Solar Energy Industries Association (SEIA). The new report, from GTM Research and SEIA, covers the second…