The Crystal River nuclear power plant has been out of order for three years, after its containment building was damaged in 2009.
The plant, owned by Progress Energy, will cost about $1.5 billion to return to working order, said engineering consulting firm Zapata.
"Progress Energy's prior assessment had indicated that the repair costs would be between $900 million and $1.3 billion with those cost trends rising," said company spokesperson Suzanne Grant.
She said Zapata confirmed those estimates.
The consulting firm also reported that costs could be as high as $3.5 billion and could take eight years, depending on the methods used to fix the building.
If the dome above the building is damaged while the walls are being repaired, for example, it will have to replaced -- costing time and money.
There are risks associated with repairing the plant, Grant said. The company won't start work on the building until a plan of action is formed.
A timetable for repairing the plant has not been determined, she said.
Retiring the plant is an option, too.
Florida Senator Mike Fasano voiced concerns about both the risks and high costs of repairing the nuclear plant.
He worries that the plant isn't insured for enough money and that costs could be passed on to consumers.
"So we're talking billions of dollars to fix a problem that Progress Energy created," Fasano said. "And who's going to fix that?"
Katherine Hahn edited this story online.