The controversial Indian Point nuclear plant near New York will close in 2021, a casualty of low energy prices and relentless criticism by environmentalists, the power company announced Monday.

Under an agreement with New York State, Entergy plans to shut down one of the two operating units at Indian Point by April 30, 2020, and the second unit will close a year after that.

Entergy attributed the decision to close the decades-old plant to shifting energy economics. Among the changes, power prices fell as much as 45 percent due to natural gas from the Marcellus Shale formation in New York and Pennsylvania, part of the American shale boom.

"Key considerations in our decision to shut down Indian Point ahead of schedule include sustained low current and projected wholesale energy prices that have reduced revenues, as well as increased operating costs," said Bill Mohl, president of Entergy wholesale commodities.

Entergy said it would look for other opportunities for the 1,000 workers employed at Indian Point.

New York Governor Andrew Cuomo and environmentalists applauded the news since the plant, located within 30 miles of New York, has long been a concern due to safety problems and worries that an accident at the aging facility could affect some 20 million people.

"For 15 years, I have been deeply concerned by the continuing safety violations at Indian Point, especially given its location in the largest and most densely populated metropolitan region in the country," Cuomo said in a statement Monday.

"This administration has been aggressively pursuing and incentivizing the development of clean, reliable energy, and the state is fully prepared to replace the power generated by the plant at a negligible cost to ratepayers."

Entergy officials have defended the plant's safety record but nonetheless have been on the receiving end of blistering criticism at public meetings in the region.

Environmentalists last year criticized the company over the degrading of hundreds of stainless steel bolts that they said raised questions about the viability of the plant. They have also said the cooling system harms ocean wildlife in the Hudson River.

"This agreement provides what we've been fighting for decades: a definite early closing date for Indian Point - our biggest existential threat in the region," Paul Gallay, president of Riverkeeper, a leading environmental group in the Hudson River region said Monday.

"It's a win for the safety of our communities, a win for the Hudson River and all the rich variety of life within it, and a win for a clean sustainable energy future."