Japan's overstretched electricity grid is likely to receive another Arctic blast in the coming days, which is already pushing up wholesale prices and may stress generators as they struggle to keep units running after the weekend's powerful quake.

While the world's third-biggest economy is unlikely to see millions plunged into blackouts as in the United States currently, the country narrowly avoided power cuts only last month in another wintry spell.

Utilities and independent power providers got another jolt at the weekend when a 7.3-magnitude earthquake struck off the coast of Fukushima Prefecture and sent plants into automatic shutdown, briefly knocking out power for nearly 1 million people.