The global electricity transition presents a persistent challenge: expanding renewable energy does not always lead to lower carbon emissions, stronger electricity-system reliability, or lower total system costs. This study compares the electricity-transition pathways of France and Germany to identify the factors behind their different outcomes and to develop an integrated policy framework for Indonesia's long-term electricity decarbonization. The study compares the long-term performance of nuclear- and renewable-based electricity systems, examines the structural factors that shape transition outcomes, and develops an adaptive framework for reliable, affordable, and low-carbon electricity development. The research uses a descriptive-analytical approach and a comparative longitudinal design covering 1970–2022. The analysis draws on secondary data from international energy databases, government publications, and scientific literature. Comparative historical analysis, techno-economic assessment, geological resource evaluation, and institutional diagnostics based on the DPSIR framework support the analysis. Three findings stand out. First, rapid renewable expansion does not necessarily produce the lowest carbon intensity. Second, lower generation costs for renewable technologies do not automatically translate into lower whole-system electricity costs because high renewable penetration requires additional storage, transmission, reserve generation, and balancing capacity. Third, electricity systems that retain standardized firm low-carbon generation show greater long-term operational stability than systems that rely predominantly on variable renewable resources. Based on these findings, the study proposes the Integrated Firm Low-Carbon Transition Framework (IFLTF), which combines renewable energy, firm low-carbon generation, supporting infrastructure, and institutional capacity within a single transition strategy. The study argues that Indonesia's electricity decarbonization strategy should consider national resource conditions, institutional capacity, and long-term infrastructure requirements alongside renewable deployment.