Fitch Ratings downgraded Oglethorpe Power Corp.'s $980.8 million of pollution control bonds and $3.05 billion of first mortgage bonds to BBB+ from A-, following the recent cost increase in the budget of the Vogtle nuclear expansion project in Georgia.

On Sept. 26, Vogtle-owners Georgia Power Co., Municipal Electric Authority of Georgia and Oglethorpe voted to continue building the project. Oglethorpe's exposure to the budget for the nuclear power plant has now increased to $7.5 billion budget, according to Fitch, up from $7.0 billion, based on its 30%, or 660 MW, ownership share in the project.

Fitch downgraded Oglethorpe's debt because additional cost increases and potential schedule delays are possible at the power plant given the ongoing nuclear construction risk, the lengthy timeline for completion and historically unreliable cost estimates. "As a minority owner, [Oglethorpe] has limited control over construction and the ultimate cost of the project," Fitch wrote.

The $980.8 million in pollution control bonds are issued by the development authorities of Appling, Burke, Heard and Monroe Counties. The rating agency affirmed its F2 rating on the $1 billion commercial paper program and removed Oglethorpe's long-term ratings from Rating Watch Negative and assigned it a Negative Outlook.

Georgia Power is a subsidiary of Southern Co.