Battery energy storage systems (BESS) and renewable energy sources are complementary technologies from the power system viewpoint, where renewable energy sources behave as flexibility sinks and create business opportunities for BESS as flexibility sources. Various stakeholders can use BESS to balance, stabilize and flatten demand/generation patterns. These applications depend on the stakeholder role, flexibility service needed from the battery, market opportunities and obstacles, as well as regulatory aspects encouraging or hindering integration of storage technologies. While developed countries are quickly removing barriers and increasing the integration share of BESS, this is seldom the case in developing countries. The paper identifies multiple case opportunities for different power system stakeholders in Croatia, models potential BESS applications using real-world case studies, analyzes feasibility of these investments, and discusses financial returns and barriers to overcome.