The Japanese government called on households and businesses in Tokyo and surrounding areas to reduce their electricity usage between 3 p.m. and 6 p.m. Monday due to heightened demand amid soaring temperatures.
The call came after the industry ministry issued its first-ever power supply advisory Sunday urging people in Tokyo Electric Power Company Holdings Inc.'s service area to take energy-saving steps such as turning off lights that are not in use.
At the same time, the Ministry of Economy, Trade and Industry called for continued and appropriate use of air conditioners due to the heightened risk of heatstroke.
TEPCO's service area covers Tokyo and eight nearby prefectures, including eastern Japan's Kanto region that endured record-high June temperatures on Saturday and Sunday. High atmospheric pressure has continued into Monday and numerous regions in the service area are expected to see temperatures of 35 C or more.
The power supply advisory is issued when an area's reserve power supply capacity ratio is projected to fall below 5 percent. The lowest level necessary for stable supply is said to be 3 percent.
For Monday, the reserve rates are forecast to be 4.7 percent from 4 p.m. to 4:30 p.m. and 3.7 percent from 4:30 p.m. to 5 p.m.
The advisory could be upgraded to a stricter warning if temperatures rise further, leading to tighter supply and demand conditions.
Other major electricity suppliers across Japan, including Tohoku Electric Power Co. serving the country's northeast and Chubu Electric Power Co. in central Japan, are expected to see significant power demand this summer.
Reserve rates in July are projected to be 3.1 percent in the Tohoku, Tokyo and Chubu areas, and 3.8 percent in regions including western and southwestern Japan.
The ministry's system for power usage advisories was introduced following a review into the response to high demand in March this year, when a powerful earthquake in the country's northeast region caused some power plants to halt.