Under the rapid growth of world’s economy and population, the demand for water and energy has been increasing accordingly. Moreover, water and energy are interrelated and form a reinforcing feedback loop. Energy is used not only onsite of water supply systems, but also indirectly for producing materials used in the water systems. As a result, it is important to understand and evaluate the energy embodiment of water supply for sustainable water and energy management. This study uses the Economic Input-Output Life Cycle Assessment software to estimate and compare the embodied energy of one China water supply system (System A) and one US water supply system (System B). It has been found that System B in the US has comparable direct operational energy consumption with System A in China; however, System B consumes much more indirect energy and constructional energy than System A. Possible reasons for the higher indirect energy use in System B might be more administrative and engineering (maintenance and repairing) services involved, lower transportation efficiency, more self water usage within the system and higher labor rates. To satisfy the water demand for the large population, China’s water supply systems have to reduce direct energy consumption during the operation phase by conducting energy budget and adopting energy efficient technologies.