In the present study two different sets of assumptions for future power production scenarios, one based on conventional technologies and another assuming a more sustainable energy oriented electricity production, for the Baltic States are analysed to identify, the possible marginal electricity sources which could be used in consequential Life Cycle Assessment (LCA) studies in these countries. The environmental impacts of electricity production often account for a major portion of the total environmental burden in LCAs of many products and services. It is known that the environmental impacts Of electricity production vary significantly, between different energy sources, thus the choice of input data could significantly influence the final results of LCA studies. Therefore, it is important that the LCA practitioners and those who draw conclusions based on LCA studies have both an understanding about data sensitivity issues and the development of energy systems. In this article the implications of marginal data choices in LCA are discussed on the basis of a case study on energy production from municipal waste incineration in the Baltic States.