The company also told the regulatory panel that construction is on schedule and within budget.
The testimony by executive Jeffrey Burleson came during the commission's first semi-annual hearing to oversee the cost of the construction.
"The actual schedule itself is a Georgia Power Co. trade secret," Mr. Burleson told the five commissioners.
The commissioners reviewed copies of the secret data during the two-hour hearing. Lawyers for consumer and business groups who signed confidentiality agreements also have access to the secrets, but none questioned Mr. Burleson when given the chance to cross-examine him.
Projected construction costs dropped, Mr. Burleson said, because the company is avoiding some interest by charging its customers for the reactors before they begin operation. A law and a commission decision, both enacted earlier this year, allow the company to break from normal practice and pass along expenses to ratepayers while construction is in progress.
The company had argued consumers would see a savings, and Mr. Burleson said the lower cost projection proves it. Many consumer groups had fought the change, warning that frequent safety-design changes often drive up the price of reactors before operation.
Commission attorney Jeffrey Stair brought up the U.S. Nuclear Regulatory Commission's delay in issuing a license for the reactors because it wants more information about the building that would contain the radiation from the atmosphere. Mr. Burleson told him the construction schedule included enough flexibility that the delay would not throw off the overall timetable.
To try to keep a lid on costs, the commission required the company to issue semi-annual status reports and to pay for the commission to hire an independent firm to monitor construction. However, Georgia Power won't allow the monitor's employees to attend meetings where construction decisions are made.
Commissioner Lauren "Bubba" McDonald expressed his satisfaction with the progress.
Georgia Power estimates the average residential customer, who pays about $100 per month, will pay an extra $1.30 each month.
The charge will change based on the pace of construction, financing rates charged to the company and the price of fuel used to generate power at existing plants.
Based on the company's projected construction timeline, the monthly charge would rise by about $1.30 each of the six years the reactors are expected to be under construction, finally reaching $9 or so each month.