Improving energy consumption in the palm oil milling process is regarded as one of the sustainable palm oil elements. Thus, this study highlights the use of ASPEN Plus-response surface methodology (RSM) approach to simulate and optimise the energy consumption of sterilisation process based on exergy analysis (i.e. exergy destroyed) and chemical reaction. ASPEN Plus V8.6 was employed to simulate the sterilisation process and then optimised using RSM. The validation of simulation results with experimental results demonstrating error values of less than 5.0%. Comparison of outlet stream simulation results with mill’s data also showed deviation values less than 10.0%. These indicated that the actual values were in good agreement with model prediction. For optimisation, three variables were considered, namely pressure, steam mass flow and sterilisation time. For conventional steriliser operated at 2.8 bar, 90 min and 14 580 kg/hr steam mass flow, the exergy destroyed was 5259.3 MJ/hr. Under optimised conditions at 5 bar pressure, 70 min and 17 550 kg/ hr steam mass flow, the exergy destroyed was 3493.9 MJ/hr. In comparison to conventional conditions, the heat loss was reduced by 33.6%. This approach is considered sustainable as it could predict the performance of industrial process without impacting processing time, cost and resources consumption.