The estimate presented to TVA in early April, revealed the project requires an additional $1.5bn to $2bn to complete, bringing the total cost to complete the unit at nearly $4.5bn, with the most likely estimate of $4.2bn.
The seven-month long analysis of the construction project identified corrective actions for project management and a cost estimate and milestone schedule.
TVA president and CEO Tom Kilgore said the company expects Watts Bar Unit 2 to be among the best operating and most economical nuclear generating facilities of the 21st century.
"The safe and quality completion of Watts Bar Unit 2 will help us deliver a balanced mix of energy sources and increase our supply of emission-free electricity," added Tom.
Estimated completion of the project is between September and December 2015 and currently site improvement works are under way.
