In 2003, China's integrated electricity utility - the State Power Corporation (SPC) - was unbundled and dismantled into five generation groups and two grid companies in an effort to increase competition and improve efficiency. In this paper, we study the impact of this deregulation reform on the operational efficiency for a balanced panel of 34 large power plants for the period 1997-2010. We find that on average these power plants have converged to the technological frontier over the sample period. Controlling for substantial heterogeneity in the technical profile, we also find that the unbundling reform has boosted productivity of China's large thermal power plants; however, the presumably differential impacts of the reform on the previously SPC-managed power plants and the independent power producers in our sample are insignificant. © 2013 Elsevier B.V.