This is not to be confused with renewable energy. Energy Efficiency (EE) mentioned here is the process of reducing your existing energy cost without affecting your core business function. Renewables focuses on acquiring green energy via natural methods such as wind turbines, solar, etc.
Energy is a must, nothing can be produced without it. It is also a cost that can no longer be taken for granted. In your business you are good at your specialty, probably not as good at determining the energy cost saving opportunities that exist. This is a specialized field.
The combination of Industrial Engineering and EE makes a lot of sense. Now the cost saving projects can be properly aligned with production requirement instead of hampering them. Applying the minimum input energy to the key or bottleneck process means you can work out what can be switched off when not required. This must take into account the buffer stock requirements, line balancing, optimum batch sizing, stop and start implications.
Besides switching things off when you can, there is technology that can replace your existing less energy efficient technology for future cost reduction benefits. This needs to be viable of course, and backed by a realistic business case.
Consider the way you pump, stop and start motors, flow throttling methods, oversize equipment, fuel type and efficiency, to mention a few.