The deal will attract an investment of about $244m.

Gregory combine cycle gas turbine plant has a power generation capacity of about 400MW and steam capacity of over one million pounds per hour, which is equivalent of 160MW of electricity.

NRG Energy president and chief executive officer David Crane said, "The addition of what is, in effect, a six heat rate, fast start, gas-fueled plant at a significant discount to replacement cost is an invaluable addition to our Texas fleet, particularly at this time with market rules and supply conditions in Texas placing a premium on flexible operations."

Majority of the electricity produced at the plant is sold to Electric Reliability Council of Texas (ERCOT), while a small percentage is provided to the Corpus Christi Sherwin Alumina plant along with steam and processed water.

NRG Energy Gulf Coast region president John Ragan said the long-term steam contract further complement’s the company’s wholesale and retail position in the state.

"Adding Gregory to NRG’s existing portfolio of cogeneration and combined cycle plants also increases our ability to share expertise and best practices across Texas and the nation," Ragan added.

The deal is expected to close in the third quarter of 2013, following the relevant approvals and customary closing conditions.