Abstract Injection molding machines consume a large amount of energy in the production process, during which the power units are the most significant factor. In order to understand the energy consumption of injection molding machines driven by different types of electro-hydraulic power units, the energy efficiencies of the asynchronous motor, the servo motor and the hydraulic pump under different working conditions are firstly analyzed. Then, the power consumptions of five different types of electro-hydraulic power units during different injection molding stages are compared and analyzed. Finally, the energy consumptions of the injection molding machine during a working cycle driven by these five power units are tested and analyzed respectively. The results indicate that the power unit using a fixed displacement pump driven by an asynchronous motor has the largest energy consumption. Compared to this power unit, the energy consumptions of other units, i.e. a fixed displacement pump driven by a speed variable asynchronous motor, a variable displacement pump driven by an asynchronous motor or driven by a speed variable asynchronous motor, and a fixed displacement pump driven by a servo motor, can be reduced by 47%, 69%, 78% and 87% respectively.