Energy service companies (ESCOs) in China have been adopting various energy conservation measures, thus playing a significant role in mitigating carbon dioxide emissions. The efficiencies of such measures vary across China, yet a comprehensive decision-supporting tool that guides the selection of measures according to geographical characteristics is lacking. This study aims to develop an efficiency evaluation framework using data envelopment analysis (DEA) to guide the selection of the most efficient ESCO measures in different parts of China. Data from 1304 ESCO projects in six parts of Mainland China were examined using DEA to determine the efficiency of 15 energy-saving measures in the manufacturing and building sectors. The results indicate that reconstruction of industrial boiler furnaces is the most energy-efficient measure in the manufacturing sector, while energy management systems are the most efficient measure in the building sector. The variation in the statuses of economic development and the climate conditions of the six areas of China are the major factors for the differences in efficiency. A decision-making tool for guiding the selection of the ESCO measures with the most efficient technologies for specific regions and end-uses is developed to provide comprehensive information to both investors and the ESCOs.