Many studies have approved that optimising the cutting parameters is effective for reducing the energy consumption of machining operations of machine tools. However, this technique to reduce the end face turning energy consumption (EFTEC), where the material removal rate is variable, has not received attention. Besides, the energy consumed for the spindle speed changes was ignored in previous research. Aiming to fill these gaps, an integrated EFTEC model is developed considering the spindle speed changes. In terms of optimisation, the EFTEC model is discretised according to the allowable accuracy of the machine tool. Simulated annealing is adopted to search for the optimal values of cutting parameters that lead to the minimum EFTEC. In the case study, nine parts with changing diameters and cutting depths are machined by a lathe (CK6153i). According to the experiments, simulated annealing has more than 96% probability of obtaining the global optima. The optimum achieves a 14.03% EFTEC reduction for a case. The relationship between the design parameters and the optimal cutting parameters is discussed. A case shows that 2.43% of the machining time increases suffer from the EFTEC optimisation.