On March 13, two days after the massive earthquake and tsunami crippled Tokyo Electric Power Co.'s Fukushima No. 1 nuclear plant, utility executives summoned more than 100 reporters to its head office in Tokyo to brief them on what Japan has never experienced except for a few years of chaos right after World War II — rolling blackouts.

It was a measure to restrict electricity supply faced with power shortages after a major nuclear plant and a few thermal stations were crippled by the quake and tsunami.

"We are truly sorry for our customers and members of the public," Tepco President Masataka Shimizu said.