Providing drinking water and wastewater treatment service to citizens requires energya lot of it. The twin problems of steadily rising energy costs and climate change have made the issues of energy management, energy efficiency, and energy sustainability the most salient issues facing drinking water and wastewater utilities today. Energy management, efficiency, and sustainability are at the heart of efforts across the entire sector to ensure that utility operations are ultimately sustainable in the future. More and more utilities are realizing that a systematic approach for managing the full range of energy challenges they face is the best way to ensure that those issues are addressed on an ongoing basis in order to reduce climate impacts, save money, and remain sustainable. In this chapter, we provide a basic primer on and review of energy. In the following chapter, we discuss in detail the efforts of the U.S. Environmental Protection Agency (USEPA) and numerous utilities to provide a systematic approach to reducing energy consumption and energy costs and developing alternative and renewable energy options.