Solar photovoltaic (PV) installations in the U.S. topped 4.78 GW in 2013, an increase of 41 percent over 2012, according to the annual market review and outlook published today by the Solar Energy Industries Association (SEIA) and GTM Research. The industry won't quite maintain that torrid pace in 2014, but watch for progress on a number of important fronts, from long-anticipated investment innovation to a rebound in the midsize project sector to addressing changes to federal investment tax credits.