More than 1,000 firms in Shanghai have been ordered to halt operations during peak periods of electricity usage for two days amid a continuing heatwave.
The demand for electricity in the city has at times been a million kilowatts above capacity.
As a result, the firms were told to stagger operations yesterday and today to avoid using power at the beginning and end of the working day in order to guarantee households enough electricity.
The order followed breakdowns at two city power plants. Workers had already repaired a generating unit at the Wujing plant, which had failed after an unspecified accident, but a generator at the Shidongkou plant also broke down on Sunday, reports said.
As of Sunday, Shanghai had seen 40 consecutive days of high temperatures - above 35 degrees Celsius - approaching a 50-year-old record. In 1953, Shanghai had 42 consecutive days of high temperatures.
The city has already ordered firms to halt operations or ration power at least twice this summer as soaring temperatures brought higher than expected demand.
Its electricity usage reached 12.24 million kilowatts on Sunday, up more than 4.2 million kilowatts from the same day last year.
But Shanghai is not alone. Some 16 provinces and cities in the east and south of the country have faced power shortages this summer.
As a result, Zhongneng Power Industry Fuel Company, the nation's five biggest power producers and 34 provincial power networks have set up an industry group to guarantee supply of coal amid strong demand, Xinhua said.
Analysts say electricity shortages have arisen in part from an over-reliance on coal-fired power plants. Planned hydropower stations and natural gas-fired power plants should help address the shortage in the next three years.
Last month the mayor of Shanghai, Han Zheng, said a new power station was due to come on line and that the Three Gorges dam would begin delivering electricity to the city next year.
The new power station will increase the output available by 900,000 kilowatts.