Jackson, Miss. Mississippi Power Co. now says the cost of its Kemper County project will top $5 billion.
A power generating plant, a coal mine and associated pipelines were originally predicted to cost about $2.8 billion.
The company revealed the new information Friday in a document it filed with the U.S. Securities and Exchange Commission. It showed projected costs through the end of November.
Mississippi Power says the project's concrete, underground piping, an electrical duct bank and structural steel work are 99 percent complete. It says process piping installation is 70 percent complete and cable installation is 69 percent complete.
The plant is expected to start operating in late 2014.
Mississippi Power is a subsidiary of Atlanta-based Southern Co.