As an energy efficiency engineer, your job is to provide technical expertise and help with the development of energy-saving plans for customers in industrial, commercial, and residential areas. The most important part of this is determining the best way to improve the efficiency of your client's energy systems. As part of this, you audit their use of electricity, calculate the most efficient way to power something, and use modeling software to see if solar panels make sense for a particular structure. Most clients want to see savings on their energy bills, so while helping them achieve those savings, you also recommend other ways to go green, such as installing Energy Star-compliant equipment.