Chubu Electric Power Co., which halted its two functioning nuclear reactors after an earthquake last week, said the closure is costing ¥400 million a day.
Chubu said the Hamaoka plant, which powers Nagoya, Japan's third-biggest city, will take at least three to four weeks to restart.
The company will incur additional costs as it increases oil- and gas-fired generation to make up for lost output, spokeswoman Emi Kawashita said Tuesday.
The 1,137-megawatt No. 4 reactor and the 1,267-megawatt No. 5 unit shut down automatically after the magnitude 6.5 temblor struck central Japan on Aug. 11. A third reactor, the 1,100-megawatt No. 3 unit, was shut down for regular maintenance at the time of the quake.