The magnitude 7.4 earthquake that occurred last week off the north-eastern coast temporarily cut power to about two million households, including hundreds of thousands in Tokyo.
Wednesday's quake occurred in the same region devastated by an earthquake and tsunami in 2011, which ultimately led to the disastrous meltdown at the Fukushima Daiichi nuclear power plant.
Wednesday's quake hit six thermal plants, knocking them out of operation in areas served by Tepco and Tohoku Electric Power Co. The damage could leave some of them idle for weeks or even months, according to Koichi Hagiuda, minister of economy, trade and industry (METI).
In Tokyo, neon signs were turned off, the lights dimmed and thermostats dialled down after the government issued an urgent call to save energy, warning of blackouts caused by serious power shortages after the earthquake.
As snow fell in Tokyo and the temperature dropped to 2C, Tokyo Electric Power Co (Tepco) said demand...