Japan’s electrical capacity is third in the world behind the United States and China, but damage and precautionary shutdowns from Friday’s earthquake and tsunami are straining its ability to meet demand. The Tokyo Electric Power Co., which provides more than a quarter of Japan’s power, is generating about 75 percent of its peak weekday demand.
The power grid
Japan’s power grid connects all four islands. If one area is heavily damaged, plants in other areas can provide backup. Japan is not connected to nearby China or South Korea, so those countries cannot help with the power shortage.