Fifteen years ago, Pennsylvania adopted its alternative energy portfolio standard (AEPS), setting modest goals for investor-owned utilities and retail suppliers to include renewable power sources in their power supply mix. The goals are so modest—just 18% renewables by 2020 to 2021 (compared, for example, to neighboring Maryland’s goal of 25% by 2020 and New Jersey’s goal of 50% by 2030)—that it seems Pennsylvania utilities may have little trouble meeting the AEPS standard.

But in Pennsylvania and elsewhere, consumer demand for renewable power—along with a recent uptick in crude oil prices, abundant natural gas and changing energy market dynamics—is driving a profound change in the nation’s electricity mix, with April marking the first time that the country derived more of its electric power from renewables than coal.