Georgia Power’s much-delayed nuclear power plant expansion is slated to come under scrutiny ahead of schedule as the result of a split decision by Georgia’s utility regulators.

The Georgia Public Service Commission this week voted 4-1 to review costs of the $16 billion-plus expansion of Plant Vogtle near Augusta, which has fallen more than 3 years behind schedule and $3 billion over budget.

The review will ultimately determine whether customers or Georgia Power parent Southern Co. and its investors should bear extra costs. Customers are already paying financing costs in their bills.

The decision to start the review came after Georgia Power asked the PSC to approve its portion of a settlement with construction contractors.

Three years ago, the PSC had decided to defer a review of any overruns until the first new reactor was in operation. Commissioner Stan Wise proposed moving forward, suggesting that it will remove a cloud over the project.

“Nothing is gained by deferring action to a future commission, (but) the industry does have something to lose if we do not act,” he said. “With this country’s move away from coal and some are even attacking natural gas, I believe we need to send a message across this country that nuclear power is viable and supported by the regulators in their respective states.”

“This Commission approved this project and this Commission should live up to its obligation to recognize schedule and price changes.”

The commission gave Georgia Power and PSC staff six months to bring it a mutually agreed-on settlement. But the review could take more than a year if an agreement is not reached, the PSC said.

Meanwhile, Southern Co. announced separately that the executive who’s run the Vogtle expansion has been named to head its national wholesale energy arm. Joseph “Buzz” Miller will become president and chief executive of Southern Power on March 7. He replaces 32-year veteran Oscar C. Harper IV, who is retiring.

Miller has been Georgia Power’s vice president of nuclear development and Southern Nuclear’s president of nuclear development.

Georgia Power CEO Paul Bowers praised Miller for “exceptional guidance and direction,” on the project.

He’ll be replaced by Mark D. Rauckhorst, named executive vice president of construction for the Vogtle project. He has been vice president of construction since 2011.

Also Tuesday, Southern Co. said its fourth-quarter profit was depressed by overruns at another construction project — a high-tech “clean coal” plant in Mississippi.

Profit fell 4.2 percent to $271 million, Southern said, in part on a $113 million charge for higher costs at the Mississippi plant. Similar charges also affected the year-earlier quarter and full-year financial results for 2015 and 2014.

Southern said its full-year 2015 profit was $2.4 billion, vs. $2 billion in 2014. Revenue declined 5 percent to $17.5 billion due to lower fuel costs passed on to customers, Southern said.