The nine utilities that own nuclear power plants need a total of ¥1.2 trillion a year just to maintain their idled reactors, according to the latest government estimate.
Antinuclear lawmakers disclosed the estimate, which was developed by the Ministry of Economy, Trade and Industry, at a meeting Thursday in Tokyo.
The power companies can't avoid the huge costs associated with their nuclear plants as they are unable to immediately slash personnel expenses or write off depreciation fees.
In the estimate, compiled at the request of the lawmakers, METI did not break down how much money each utility needs to maintain the rectors.
All nine firms include nuclear-related expenses in their billing, meaning consumers ultimately have to shoulder such costs.
Forty-eight of Japan's 50 functional commercial reactors are offline amid heightened concerns over the safety of nuclear energy in light of the Fukushima triple-meltdown disaster, which started in 2011. The reactors also face new safety standards.