Georgia Power does not owe Plant Vogtle’s main contractors $425 million in disputed costs, the utility said in a lawsuit filed against Westinghouse Electric Co. and a subsidiary of the Shaw Group.

The lawsuit is the fourth between the Vogtle nuclear expansion project’s owners and vendors, and the outcomes could eventually trickle down to customer bills. In the suit, Georgia Power says the vendors are at fault for changes in building certain components as well as delays in the project’s schedule and should pay for the associated costs.

It’s unclear how long it will take to resolve the lawsuits and other ongoing cost disputes. Georgia Power said in a separate document filed Wednesday that the utility has filed the suits to protect its customers but warned that they eventually may be on the hook to pay more for Vogtle.

“We have not agreed with the amount of these proposed adjustments, nor that we have any responsibility for any costs of schedule delays related to these issues,” Georgia Power said in the document, which reviews the cost and schedule of Vogtle for the first six months of 2012.

Georgia Power customers currently pay for the financing costs of the utility’s $6.1 billion portion of the project. Georgia Power said it would not formally ask for customers to pay more for two nuclear reactors until those disputes are resolved, but that the company “may conclude that the projected cost should be revised to reflect additional costs.”

Any increase to the project costs must be approved by the Georgia Public Service Commission.

The utility again warned that the dates that the reactors are expected to start producing electricity have slipped six months to November 2016 and 2017. The six-month delay has increased the projected cost of the utility’s share of the project by 1 percent to $6.2 billion, but the utility has not asked the PSC to recoup those costs at this time.

Georgia Power also may ask customers to pay the company’s costs of negotiating the terms of $3.4 billion in federal loan guarantees for Vogtle – even if the utility doesn’t receive the government’s deal after all.

Through a federal loan program, taxpayers are guaranteeing more than $8 billion in loans for Vogtle’s expansion.

If the loan guarantees don’t come through, the company said it would ask to recoup the costs of the money spent trying to get the loans. The amount would be included in the utility’s request for new electricity rates, which it will make with the Georgia Public Service Commission in 2013.

Georgia Power has discussed challenges with negotiating the terms of the federal loan guarantees in previous documents filed with the PSC. Much of that information was redacted from the public until recently.