The term "Watergy" was coined by the Alliance to Save Energy to describe the strong link between water and energy in municipal water systems. The Watergy approach helps cities realize significant energy, water and monetary savings through technical and managerial improvements in water supply and wastewater treatment systems, creating efficiencies that provide consumers with quality service with a minimum of water and energy. Efficiency in the water sector involves both the end use of water - such as efficient toilets, low-flow showerheads and reducing peak demand - as well as efficiencies in the supply of water. This paper focuses on the water supply system itself since in many cities most of the inefficiencies occur before the water even reaches the end user. Watergy principles have been applied in numerous cities around the world, demonstrating that water efficiency measures repay themselves quickly and yield many rewards: improvements in water service, immediate increased water delivery, reduced water and energy consumption, and more revenue for system upgrades and new customer connections. Opportunities abound throughout all stages of a water supply system. The most promising areas for intervention within water supply systems are: (i) improving the pumping system, (i) managing leaks, (iii) automating system operations, and (iv) regular monitoring (preferably with rigorous metering of end use). These improvements often pay for themselves in months, most do so within a year, and almost all recover their costs within three years. The pumping system is all important, since every liter of water that passes through the system represents a significant energy cost, a cost that is magnified by every liter lost to leaks. Pumping improvements range from lower cost measures like soft starters for motors, trimming impellers (when pumps are over-sized) and re-winding motors, to higher cost measures like replacing inefficient pumps with efficient ones and installing variable speed drives. System automation saves water, energy and operation costs, improves service, and lengthens equipment life. Automation handles operational functions in real time in response to changing situations. Examples are optimizing pressure in the network, triggering alarms in case of emergency, and turning off pumps. Regular monitoring of the system components, operations, and performance is essential targets. in order to track performance and evaluate it against a set of benchmarks and Incorporated as part of the larger O&M protocol, monitoring is a no- or low-cost efficiency enhancement within reach of all utility budgets. Effective management of leaks can save enormous quantities of water and energy. Leakage rates can be lowered dramatically with automated controls that reduce pressure in the network, especially at night. Pressure management is generally more cost-effective than expensive repairs to numerous leaks in buried pipes. This paper provides a comprehensive overview—suitable to all technical levels—to introduce the reader to the approaches and benefits of Watergy. It is intended for a wide audience ranging from municipal and water utility decision makers, to funding organizations, to technical utility staff who want a solid understanding of what a water efficiency program entails without a high level of technical detail.