This paper is dedicated to the analysis of power system long-term capacity expansion planning process. Long-term planning is usually used for strategic decision making and is in focus in these changing times when the goal of zero emissions by 2050 is put in place by the European Union. It is necessary to observe the possibilities and limitations of long-term modelling in quickly changing conditions and it is also necessary to see how big of an impact is of some parameters. One of the most important parameters in long-term planning are the technology prices. In the next 30 years it is foreseen that those technologies will develop rapidly, and that also their prices will decrease as a result. Also, fossil fuel plants will be shutting down all over Europe which will make a significant shift in base load and peak load energy. These changes have to be captured in modelling on time so that the consumers have a continued unlimited supply of electricity. This paper analyses the real impact of technology prices on long-term planning through various scenarios of change of solar and wind technologies, since they are the ones that are expected to make the most significant penetration in the future. The analysis is performed on the model of Republic of Croatia, made in modelling software PLEXOS, taking into account the foreseen demand by 2050. In the model all power plants that will be in operation in this period in Croatia are modelled in detail. The results show that the technology prices have only a partial impact while the model takes into account all other limitations and settings. However, it is reasonable to say that the classic long-term planning will have to be complemented with short-term analyses in the future to make sure that the system can endure such high penetrations of variable renewable energy sources.