Croatia’s energy strategy is set in line with European trends in the pursuit of a significant increase in the share of electricity produced from renewable sources. With regard to the practice of the leading countries in the world in terms of the level of integration of renewable sources, the paper presents basic technical and economic assumptions, as well as possible ways of solving potential problems that are expected during the operation of systems with increased penetration of renewable sources. Special emphasis is placed on the integration of wind power plants, given the current greatest interest in their construction, which are regularly planned with large installed powers, are connected to the transmission network and have a significant impact on the systemic aspects of the EES operation. On the other hand, we can also expect a strong development of various distributed sources of lower power, which will be connected to the distribution network, and in this way fundamentally change the current features of the passive distribution network.