Kashima Kyodo Electric Power has resumed operations at its 350MW gas and oil-fired unit No 4 at its thermal power plant in eastern Japan.
Kyodo has now resumed full operations from three of its four units at the plant.
Units No 1 and 3 have already been restarted, while the 350MW unit No 2 has been suspended, reports Reuters.
Kyodo Electric Power supplies half of its power generated to Tokyo Electric Power.
The unit was shut after a massive earthquake of 9.0 magnitude hit Japan on 11 March 2011.