Energy efficiency is becoming an important objective for modern manufacturing industry. The aim of this work is to improve energy efficiency of an automated system. Since a majority of production processes are limited by an external bottleneck, the hypothesis of this work is that reducing the processing rate of the restricted processes can lead to saving in energy and resources. A methodology based on optimisation at process, cell and line levels is developed and evaluated over different scenarios.The developed methodology is then applied to a simulated production cell to study its efficacy quantitatively. In this particular case, the proposed approach yields a decrease in energy consumption of 49% at maximum production capacity. This decrease can be greater if there is an external factor such as low demand or another stage in the production line.