A new federal report says solar energy could provide as much as forty percent of the nation's electricity in fifteen years but it would require billions of dollars in federal investment the energy department says the US installed a record fifteen gigawatts of solar generating capacity last year it shifts toward renewable dominant power grid to address the threat of climate change solar now represents just over three percent of the electrical supply but energy secretary Jennifer grant Holmes says solar could produce enough to power all homes in the U. S. by twenty thirty five to do that however the department's renewable energy laboratory says the country would need to quadruple its annual solar capacity installing thirty gigawatts per year between now and twenty twenty five double the current rate and sixty gigawatts double again over the following five years Ben Thomas Washington