States that require utilities to increase renewable energy see an expansion of renewable energy facilities and generation -- including wind and other renewable sources, but especially solar -- according to new research from Indiana University and two other institutions.

IU's Sanya Carley led a team of researchers including Nikolaos Zirogiannis, an assistant scientist at IU, and law professors Lincoln Davies of the University of Utah and David B. Spence of University of Texas at Austin. The group closely examined the history and evolution of state renewable portfolio standards and interviewed more than 40 experts about renewable portfolio standards implementation.

Their findings are newly published in the peer-reviewed journal Nature Energy, in an article titled "Empirical evaluation of the stringency and design of renewable portfolio standards."

The regulations, which require utilities to increase the percentage of energy they sell from renewable sources by a specified amount and date, have been adopted in varying forms by about 30 states. For example, New York requires 50 percent of all electricity sold in 2050 to come from solar.

Read more at Indiana University