There are many ways to improve your energy efficiency. You may find that you can make significant savings by focusing on equipment; lighting and heating that can be switched off at certain times. You can decide whether to manage this through procedures and behaviour change or whether to install automated systems such as movement triggered light switches. You could focus on bathroom lights that do not need to be on until people need them or you might tackle power consumption during shut down periods.
You could focus on a section, team or piece of equipment and work to optimise its energy consumption while maintaining (or improving) productivity rates. In addition to direct savings this could provide a blueprint for other optimisation projects.
You may also find that waste heat (or cooling) from one process can be used by another. While this will usually require some expenditure, the savings may pay for it.
You might find that heat/cooling is contributing to inefficiency. Lagging (insulation) may have fallen off, become damaged or is not effective for some other reason. Steam traps might be passing or leaking. These things are often easy to check regularly and any expense to fix them is usually recovered quickly from the savings.