More than 20 billion yuan ($2.9 billion) has been spent over the past two years on increasing the capacity of Beijing's power grid to meet demand during the Olympics, State Grid Corp of China (SGCC) said Wednesday.

More than 100 transformer stations and nearly 1,000 km of transmission lines have been added to help boost capacity by about a third, SGCC, which overseas the power supply to 26 provinces, said.

During the Games, about 60,000 people will work on power systems, it said.

As the official energy partner of the Beijing Olympics, SGCC will ensure an uninterrupted supply during both the Olympics and Paralympics, its president Liu Zhenya said.

But doing so will be a big challenge, as summer is the peak season for power consumption, he said.

The Beijing municipal government has said consumption during the Olympics is set to reach a record high.

The city gets most of its energy from neighboring provinces, with 35 percent of its power and 45 percent of its coal coming from Shanxi, and more than 40 percent of its coal coming from the suppliers in Inner Mongolia autonomous region.

Although there is currently a nationwide coal shortage, authorities in Shanxi and Inner Mongolia have said they will do all they can to ensure supplies to Beijing.