Two environmental groups say the power Indian Point generates can be replaced with renewable energy when the plant closes, potentially doubling the energy output of the plant by 2030. Entergy, which runs the nuclear plant, announced a deal with the state last month to shut down one unit in 2020 and another in 2021.

As long as the state adopts policies that encourage energy efficiency and clean energy, the power from Indian Point can be replaced by wind and solar power without adding carbon pollution or risking reliability, according to a study commissioned by Riverkeeper and the Natural Resources Defense Council. The groups recruited a research firm to study energy options for the state.

"We've got four years to increase our efficiency in the energy use and provide for even more wind and solar and hydro, and these are all coming forward faster than we expected," said Riverkeeper President Paul Gallay. "And the demand for power has flattened out faster than we've expected." 

According to the study, the state has already adopted policies that will help move toward using renewable energy sources, such as the "50 Percent by 2030" clean energy standard that was enacted in August. 

Other goals include increasing energy efficiency in buildings and building a new transmission line from Canada to New York City.