page_title: 2011 Tōhoku earthquake and tsunami
section_title: Electricity
hierarchical_section_title: 2011 Tōhoku earthquake and tsunami / Damage and effects / Electricity
context_page_description: The 2011 earthquake off the Pacific coast of Tōhoku was a magnitude 9.0–9.1 undersea megathrust earthquake off the coast of Japan that occurred at 14:46 JST on Friday 11 March 2011, with the epicenter approximately 70 kilometers east of the Oshika Peninsula of Tōhoku and the hypocenter at an underwater depth of approximately 29 km.
  The earthquake is often referred to in Japan as the Great East Japan Earthquake and is also known as the 2011 Tōhoku earthquake, the Great Sendai Earthquake, the Great Tōhoku Earthquake, and the great earthquake of March 11.
  It was the most powerful earthquake ever recorded in Japan, and the fourth most powerful earthquake in the world since modern record-keeping began in 1900.
  The earthquake triggered powerful tsunami waves that may have reached heights of up to 40.5 meters in Miyako in Tōhoku's Iwate Prefecture, and which, in the Sendai area, traveled at 700 km/h and up to 10 km inland. Residents of Sendai had only eight to ten minutes of warning, and more than a hundred evacuation sites were washed away.
context_section_description: According to the Japanese trade ministry, around 4.4 million households served by Tōhoku Electric Power (TEP) in northeastern Japan were left without electricity. Several nuclear and conventional power plants went offline after the earthquake, reducing the Tokyo Electric Power Company's (TEPCO) total capacity by 21 GW. Rolling blackouts began on 14 March due to power shortages caused by the earthquake. TEPCO, which normally provides approximately 40 GW of electricity, announced that it could only provide about 30 GW, because 40% of the electricity used in the greater Tokyo area was supplied by reactors in the Niigata and Fukushima prefectures. The reactors at the Fukushima Daiichi and Fukushima Dai-ni plants were automatically taken offline when the first earthquake occurred and sustained major damage from the earthquake and subsequent tsunami. Rolling blackouts of approximately three hours were experienced throughout April and May while TEPCO scrambled to find a temporary power solution. The blackouts affected Tokyo, Kanagawa, Eastern Shizuoka, Yamanashi, Chiba, Ibaraki, Saitama, Tochigi, and Gunma prefectures. Voluntary reductions in electricity use by consumers in the Kanto area helped reduce the predicted frequency and duration of the blackouts. By 21 March 2011, the number of households in the north without electricity fell to 242,927.
  Tōhoku Electric Power was not able to provide the Kanto region with additional power because TEP's power plants were also damaged in the earthquake. Kansai Electric Power Company (Kepco) could not share electricity, because its system operated at 60 hertz, whereas TEPCO and TEP operate their systems at 50 hertz; the disparity is due to early industrial and infrastructure development in the 1880s that left Japan without a unified national power grid. Two substations, one in Shizuoka Prefecture and one in Nagano Prefecture, were able to convert between frequencies and transfer electricity from Kansai to Kanto and Tōhoku, but their capacity was limited to 1 GW. With damage to so many power plants, it was feared it might be years before a long-term solution could be found.
  To help alleviate the shortage, three steel manufacturers in the Kanto region contributed electricity produced by their in-house conventional power stations to TEPCO for distribution to the general public. Sumitomo Metal Industries could produce up to 500 MW, JFE Steel 400 MW, and Nippon Steel 500 MW of electric power Auto and auto parts makers in Kanto and Tōhoku agreed in May 2011 to operate their factories on Saturdays and Sundays and close on Thursdays and Fridays to help alleviate electricity shortages during the summer of 2011. The public and other companies were also encouraged to conserve electricity in the 2011 summer months (Setsuden).
  The expected electricity crisis in 2011 summer was successfully prevented thanks to all the setsuden measures. Peak electricity consumption recorded by TEPCO during the period was 49.22GW, which is 10.77GW (18%) lower than the peak consumption in the previous year. Overall electricity consumption during July and August was also 14% less than in the previous year. The peak electricity consumption within TEP's area was 12.46GW during the 2011 summer, 3.11GW (20%) less than the peak consumption in the previous year, and the overall consumption have been reduced by 11% in July with 17% in August compared to previous year. Japanese government continue to ask the public to conserve electricity for several years until year 2016, when it predicted that the supply will be sufficient to meet demand, thanks to the deepening of the mindset to conserve electricity among corporate and general public, addition of new electricity providers due to the electricity liberalization policy, increased output from renewable energy as well as fossil fuel power stations, as well as sharing of electricity between different electricity companies.
caption: Geographic divide between 50 hertz systems and 60 hertz systems in Japan's electricity distribution network