“Market conditions and increased [operational] costs led us to reluctantly conclude that we had no option other than to shut down the plant,” said Leo Denault, Entergy’s chairman and chief executive officer in a statement.

Low wholesale energy prices—driven by record-low natural-gas prices and a state proposal to provide above-market prices to Canadian utilities for hydropower to meet up to a third of Massachusetts’ electricity demand—set the decision in motion.

Another factor was a series of unplanned shutdowns that led to a downgrading of the plant on Sept. 2 by the Nuclear Regulatory Commission, placing it among the least safe of the nation’s 99 operating reactors.

Gov. Charlie Baker (R) stated that his administration will work closely with Pilgrim and federal regulators to ensure the shutdown is managed as safely as possible. “We will continue to work with ISO and the other New England governors to ensure that Massachusetts and New England [have] the baseload capacity [required] to meet the electric generation needs of the region.”

Baker said the Pilgrim shutdown not only poses a potential energy shortage but highlights the need for clean, reliable, affordable energy proposals. His administration has put forth a program based on hydroelectricity and other renewable resources. “The closure of Pilgrim will be a significant loss of carbon-free electricity generation and will offset progress Massachusetts has made in achieving the 2020 greenhouse-gas emission reduction goals, making it more challenging to hit these targets,” Baker said.