The main objective of sustainable energy strategy is to provide for the security of electricity supply required to underpin economic growth and increase the quality of living while minimizing adverse environmental impacts. Alongside with the implementation of sustainable development principle there is a prevailing interest in the issues relating to electricity market opening, particularly regarding the question of how market opening will affect CO2 emissions. It is obvious that the emission market has an environmental impact and represents a new factor in the calculation of marginal costs of electricity generation. Consequently, marginal costs of all fossil fuel fired power plants will see a relative increase depending on the carbon contents in fuel. For a marginal power plant, the increase in the market price equals additional costs associated with carbon content. Power plants not emitting CO2, such as nuclear plants and hydroelectric stations, will profit from increased market prices of electricity. The purpose of the present doctoral thesis is to determine the impact of additional costs of CO2 emissions on the costs of electricity generation and on the position of individual electricity generation technologies in the open electricity market. It gives a contribution to the development of scientific knowledge on sustainable development of the power system in general, and especially in open market conditions. In terms of implementation, the expected contribution could be the application of the developed models based on the inclusion of CO2 emission trading costs in the Croatian electricity market.