Kyushu Electric Power Co. is set to begin full-scale commercial operation of reactor No. 1 at its Sendai plant in Kagoshima Prefecture after the unit cleared a final inspection by the regulator on Thursday.

The plant's No. 1 reactor has been generating and feeding electricity to the grid on a trial basis since it went live on Aug. 11, becoming the nation's first reactor to resume operation under safety regulations adopted after the 2011 nuclear crisis.

Kyushu Electric Power plans to reactivate reactor No. 2 at the two-unit Sendai plant in mid-October.

The utility expects its earnings to improve by ¥15 billion a month when the two units are back online.

It projects posting a group net profit of ¥45 billion in the first half of the current business year through March, due to the restart of the No. 1 unit. It hopes to put its full-year earnings into the black for the first time in five years.

Before reactor No. 1 was reactivated in August, Japan had no nuclear power supply for nearly two years, as all commercial reactors were gradually taken offline in the wake of the Fukushima disaster.

Other power companies are also desperate to bring their reactors back online to reduce their fossil-fuel bills. However, analysts say the outlook remains uncertain as hurdles include the in-depth and lengthy safety screenings required by the regulator.