Within highly mechanised agricultural productions systems such as the Australian cotton industry, operational energy inputs represent a major cost to the growers. In this paper, a framework to assess the operational energy inputs of various production systems and the relative performance of a grower within an adopted system is developed. It divides energy usage of cotton production into six broadly distinct processes, including fallow, planting, in-crop, irrigation, harvesting and post harvest. This enables both the total energy inputs and the energy usage of each production processes to be assessed. This framework is later implemented and incorporated into an online energy assessment tool (EnergyCalc). Using the developed software, seven farm audits are conducted. It is found that overall, depending on the management and operation methods adopted, the total energy inputs for these farms range from 3.7 to 15.2 GJ/ha of primary energy, which corresponds to $80-310/ha and 275-1404 kg CO2 equivalent/ha greenhouse gas emissions. Among all the farming practices, irrigation water energy use is found to be the highest and is typically 40-60% of total energy costs. Energy use of the harvesting operation is also significant, accounting for approximately 20% of overall direct energy use. If a farmer moves from conventional tillage to minimum tillage, there is a potential saving of around 10% of the overall fuel used on the farm. Compared with cotton, energy uses by other crops are generally much smaller, due to less intensive management practices, and reduced irrigation requirements. (C) 2009 Elsevier Ltd. All rights reserved.