In this paper the design and development of a database for the registration of power utilities’ customers and their energy behavior are described. The database also includes the customers’ devices and buildings, their demand curves, their tariffs, their connection with power and gas networks, as well as the measures of demand side management and energy saving, which can be implemented. The main purpose of this database is to support end-use models and load forecasting algorithms for individual customers or their respective clusters, to study the effects of energy efficiency programs and to evaluate the last ones financially. It can be a useful tool for retailers, distribution electricity companies or regulatory authorities of energy.