The paper describes the software tool implemented by Melentiev Energy Systems Institute SB RAS, aimed to solve wide range of energy issues. In this article, the Computing and Information System (CIS) means a software tool that provides collection, transfer, processing, storage, geo-visualization, and output of digital technical and economic data of different energy/power entities. Besides, this tool is incorporated within a mathematical model for optimization of expansion and operating modes of power systems. The paper discusses the example of how data storage and data representation in object-oriented database assist to improve efficiency of research prospective electric power systems expansion and operation.