Report: US solar costs continue rapid decline. System costs have declined by a total of 85-95% since peaking a decade ago. Solar prices in the US in 2013 fell by a further 15% year on year, a study from the Department of Energy and Lawrence Berkeley National Laboratory has found.The report ‘Tracking the Sun’ is the seventh edition summarising PV prices from 1998, up to the first half of 2014, across the US.The study concluded that between 2012 and 2013 solar prices fell by 12-15% depending on system size, averaging US$0.07 per year.he report surveyed 300,000 residential, commercial and utility-scale solar systems, across 33 states, representing 80% of grid connected solar in the US and looks at the dollar cost per watt for solar.