How do governance arrangements affect renewable energy integration? This thesis addresses this question by focusing on grid flexibility. As wind and solar power grow worldwide, the main challenge is no longer building generation capacity but managing the unpredictability of these energy sources. While previous studies often see this as just an engineering issue, this research demonstrates that flexibility is influenced by governance shaped by policies, market designs, and institutional capabilities.The study compares Sweden and Türkiye, two different governance models facing similar renewable energy pressures. Analyzing policy documents, market rules, and institutional reports reveals significant differences in planning logic, market setup, and coordination. Sweden combines proactive grid investment, market-based pricing, and Nordic cooperation. Türkiye follows a different governance structure. Its system relies on reactive planning, centralized control, and administrative measures, which together constrain the conversion of its high technical potential into operational flexibility. By highlighting three specific mechanisms of price signals, planning coordination, and institutional adjustment, this work adds to sustainability transition studies. The main takeaway is that the clarity and consistency of market rules are much more important for renewable integration than just having a market structure.