Hong Kong-based China Light & Power said mainland power supplies could exceed demand next year and for the two following years as new plants come on line. Speaking at a Singapore energy conference, CLP Power Asia Executive Director Stefan Robertson said while China would add 30,000 megawatts of power supply a year, demand growth would slow, resulting in excess capacity. China has said it wants to double power generation capacity to about 900,000 megawatts by 2020 from 400,000 mW now.