SHANGHAI - Electricity shortages have been bringing more pain to East China as the mercury has climbed during the past week and power providers announced rationing in Shanghai, Zhejiang and Jiangsu.

In Zhejiang province, demand for power was predicted to reach 50 million kilowatts - an 18.9 percent year-on-year increase - while limitations in supply meant 5 million kilowatts of that wanted power would be unsatisfied, according to statistics from the Zhejiang Electricity Power Corporation of the State Grid.

Power consumed from the Shanghai Electricity Power Corporation of the State Grid peaked at 24.13 million kilowatts on July 4. In light of the sizzling demand, the corporation began rationing power this summer among some industrial users on that day.

The Shanghai municipal government has also approved a power-rationing plan for 3,000 non-industrial users. But the power rationing among householders, malls and offices is not mandatory.

The gap between the demand for power and the ability to supply it may widen further in East China. In May 2011, the demand for power reached 18 million kilowatts an hour in Shanghai, which was equal to the peak power demand from 2010, suggesting more power shortfalls are likely as the hotter summer months follow, according to Zhou Xiujie, a researcher with CIConsulting, an industry survey service, who spoke to Shanghai Securities News.

Rising temperatures are pushing up the demand for electricity as people fire up their air conditioners to counter the effect of days where the temperature nudges past 30 C.

In Shanghai, five days among the first 12 days of July were hotter than 37 C. On July 3, the mercury soared to 38.3 C, the highest temperature of the year so far, according to the Shanghai Meteorological Bureau. Some non-industrial users tried to help out by setting their air conditioners at 26 C when they might have preferred a colder temperature in a bid to reduce their electricity use.

"The temperature in the office is OK and our colleagues understand and want to help tackle the power shortage in this way," said Gong Shuli, a 38-year-old accountant, who works in a building that has set its air conditioners to work less hard, despite the high temperatures outside.

In Shanghai during the past three years there has been a 7 to 8 percent annual growth in the demand for electricity. The difference between what is being demanded and what the authorities are capable of supplying may reach 2.1 million kilowatt-hours this summer and the shortfall across the whole of China this summer could exceed 30 million kilowatts, according to the China Electricity Council.

Power supply authorities said they will strive to secure power supply for residential users.