Huaneng Power International, the listed unit of the nation's largest power producer China Huaneng Group, posted a 38 per cent year-on-year rise in power output in the first half of the year to 118.84 billion kilowatt hours. The company attributed the growth to the low-base effect of last year's first-half and the contribution from newly operating and acquired power plants. BOC International analyst Peter Yao Sheng noted second-quarter output was only 2.9 per cent higher than in the first quarter, lower than that of rivals Huadian International Power and China Power International Development.