A study was conducted to determine the energy consumption in palm-kernel oil (PKO) processing operations as carried out in nine PKO mills in Nigeria. The mills were equally stratified into three categories to represent different mechanization levels and production capacities. Mathematical expressions were developed to evaluate the energy requirement for each of the seven readily defined unit operations, namely: palm-nut drying, palm-nut cracking, palm-kernel crushing, palm-kernel roasting, PKO expression, PKO sifting and PKO bottling/pumping. The equations were exploited to compute energy expenditure by the mills using measured input data. Empirical equation was developed for each unit operation to relate energy requirement to palm-nut/kernel input. The application test of the equations indicated that about 352 MJ, 232 MJ and 177 MJ was averagely needed to process 1000 kg of palm-nut in the small, medium and large-scale mill, respectively, while energy requirement for each unit operation in each mill category was also estimated. (c) 2006 Elsevier Ltd. All rights reserved.