Aim of this paper is to investigate the advantages of en-ergy market by incorporating it into large power system modeling process. The authors discuss optimization of long-term sustainable development of large power systems under energy market conditions. The paper considers test case with ENTSO-E and IPS/UPS power system calculations under market conditions, including sustainable development optimization and cost-benefit evaluation. The paper also describes application of zonal energy price formation algo-rithms and interaction of power systems on energy im-port/export issues. The tool of the research is LDM-TG information technology, which is developed by the Institute of Physical Energetics, Latvia. The information technology provides the opportunity to perform dynamic optimization of system development together with operational state cal-culations.