Long term planning of energy system’s development becomes closely connected to analysis of day- ahead power markets, market coupling and dynamics of integration of both, renewable energy sources and demand response technologies. In this study a scenario approach with minimization of marginal cost of generated electricity is used to investigate and quantify the influence of investments in generation units for the observed zone and the commitment of units in the surrounding zones. Dispa-SET software was used for modelling of a case study which included eight zones connected in the electricity market. Year 2016 was selected as referent, while future scenarios in 2030 are created with different strategic decision made in each of the zones. Results demonstrate the influence of different strategic pathways in different zones, through electricity generation and levels of storage capacities in the investigated zone and neighbouring zones and cross-border electrical energy flows. If most of the zones are pursuing unambitious strategies (2030a), marginal cost of electricity is double in comparison to the most ambitious case, while moderate approach in the most zones brings the cost reduction of 20%. Ambitious scenario 2030c for all zones results in the least cost of electricity, 30% of the cost in scenario 2030