Efficient water and energy use in water distribution systems is being limited by the lack of sufficient data about water and related energy consumption. Therefore, it is crucial to provide updated and continuous feedback information to water users. This paper describes relevant use cases to improve efficient water use and related energy consumption by water utilities and consumers through the use of smart metering technologies. A systematic approach was established to obtain a comprehensive list of possible functionalities, using the concept of use case. For the consumer domain, six high-level and 18 detailed-level use cases were obtained. For the water utility domain, seven high-level and 20 detailed-level use cases were described. The high-level use cases with higher priority to be implemented in the iWIDGET system were also identified based on the contribution of different target audiences. The list of use cases covers a comprehensive range of possible usages that can be built upon the exploitation of data related to water and energy use in water distribution systems and in households, which may be of further use as a guide for similar studies.