This study investigated the energy productivity and input sensitivity of sweet sorghum (Sorghum bicolor (L) Moench), as compared with cotton and maize, at two coastal saline-alkali sites in Shandong Province, China. The data were collected quantitatively using a questionnaire for face-to-face interviewing of 116 farmers. The sorghum showed a lower energy input requirement than cotton and maize. The energy productivity indices were 12.4 and 9.2 for sweet sorghum, which were much higher than for cotton (3.1) at Wudi and maize (8.4) at Wendeng, respectively. Nitrogen fertilisation contributed the highest proportions (between 56% and 69% for the three crops) to the total energy consumption, as compared with the seed, labour, machinery, diesel fuel, phosphorus and potassium fertilisers, irrigation water, plastic film, and pesticides. All of the crops consumed much more non-renewable energy than renewable energy. According to the Cobb-Douglas production function, the diesel and nitrogen fertiliser energy inputs had a significantly positive impact on the sweet sorghum energy output. The energy crop showed an increasing return to scale, with cotton showing a constant and maize a decreasing return. These findings indicate that the sweet sorghum energy output is possible to be increased with further technical research and development. (C) 2012 Elsevier Ltd. All rights reserved.