Dwindling coal supplies have prompted eastern China's Anhui province to activate an emergency plan ahead of schedule, limiting electricity use by more than 5,000 local enterprises at peak times to allow residents to have supply.

Chief engineer at the Anhui Power Company Du Guihe told Xinhua Friday the province's power shortage may exceed one million kilowatts this summer, as some power plants have only three days of inventory, compared with the danger line of seven days.

Under the emergency plan, 5,600 enterprises are required to avoid power use at peak times while power-use caps have been imposed on another 301 companies, Du said.

Du did not say when the emergency measures will be lifted.

He said ensuring electricity supply during the summer will be a challenge as insufficient coal inventory, transport glitches, adverse weather and higher prices might aggravate the situation and cause inventory to fall even further.

The usual benchmark for thermal coal inventory at Chinese coal-fired power plants is set at 15 days of supply.

Du said current inventory at local pillar coal power plants stood at 750,000 tonnes, enough for seven days of power generation.

According to Anhui Power's projections, the province's maximum power load in summer may hit 18.3 million kilowatts, up 15 percent from a year earlier. But local installed power generation capacity is 17.45 million kilowatts.

The shortfall can be cut to 600,000 kilowatts if power is imported from other provinces, Du said.

In April, because of a severe drought, hydro-power-dependent Yunnan and Guizhou provinces in China's southwest suffered power shortages.