China's five biggest power generators lost a total of 140 million yuan ($21.64 million) in their wind power businesses in July, according to statistics from The China Electricity Council (CEC), 21st Century Business Herald reported Thursday.

This is the first time a loss has been reported this year. The profit figure was 820 million yuan down from June, the report said.

However, of the five power companies, China Guodian Corp, China Huadian Corp and China Power Investment Corp denied a loss in their wind power business in July. China Huaneng Group and China Datang Corp did not disclose their figures.

"Wind is weak in July, August and September, so the profits will drop. This is decided by the seasonal characteristics of the wind power industry," Li Shusheng, chairman of CECIC Wind Power Investment Co, told the newspaper.

Wind resource varies in different seasons. July is the start of the trough season of wind resource, the report said.