Officials had planned to deactivate three units of the 330-megawatt New Castle plant in Pennsylvania, northwest of Pittsburgh, along with two units at the Avon Lake facility in Ohio by April 2015.
However, the utility is reviewing its portfolio for viable refueling since it merged with GenOn Energy last December.
NRG said both should be ready to come back online on or about May 2016 pending approvals.
The move was expected to save about 40 full-time jobs at New Castle alone and could create as many as 100 temporary construction positions during the conversion, NRG spokesman Dave Daier told the Pittsburgh Post-Gazette.
