DALIAN, Liaoning - China's constraints on electricity supplies will help greatly boost United Company Rusal PLC's sales to the country, said a senior company official.

"We expect aluminum exports to China will start to increase substantially next year," said Oleg Mukhamedshin, deputy CEO.

The gap between demand and supply in China will create an opportunity of 4 million tons a year for the company by 2015, he said.

China, the world's largest producer and consumer of aluminum, is currently balanced in terms of aluminum output and use.

Rusal's sales to China grew 15 percent in the first half and will continue to increase over the next decade because of the country's fast urbanization and industrialization, Mukhamedshin said.

"The construction, automobile and aerospace industries in China are expected to be the growth engines for aluminum producers."

Production capacity in China might total 25 million tons this year, while output could reach 20 million tons, according to Bloomberg News.

Rusal expects its overall revenue for the second half of 2011 to remain flat, despite a 67 percent fall in the second quarter caused by rising costs and a stronger rouble.

There will be a switch in the driver of Rusal's market growth from Europe to China, Mukhamedshin said.

The overseas market generates 80 percent of Rusal's revenue, with Europe contributing half of that.

About 50 percent of the producers in China are operating at high cost because they face high electricity costs by global standards, Mukhamedshin said.

Rusal has located 80 percent of its production capacity in Siberia, where it can take advantage of hydropower, which provides cheaper electricity than that generated by coal.

Overcapacity in the aluminum industry has been a concern for the Chinese government in recent years. China has since 2003 been trying to rein in excess aluminum capacity.

Aluminum smelting accounts for about 6 percent of China's total electricity use, according to the data provider Shanghai Metals Market.