Climate change and global decarbonization goals necessitate a transition to renewable energy, especially in developing countries like Indonesia. North Sumatra, a province with vast renewable potential hydro, geothermal, biomass, and solar plays a strategic role in Indonesia's energy transition roadmap toward Net Zero Emissions (NZE) by 2060. This study explores optimized pathways for achieving 100% renewable electricity generation in North Sumatra, considering both the mainland and the isolated Nias Island. Using the Low Emissions Analysis Platform (LEAP) and NEMO optimization tool, three scenarios were modeled: Business As Usual (BAU), Government Policy Reference (REF), and 100% Renewable Energy Target (RE100). Each scenario incorporates techno-economic, environmental, and policy constraints based on regional data and national planning documents (RUPTL, RUEN, and RUED). The BAU scenario assumes no emission constraint or renewable targets, leading to a fossil fuel-dominated future. The REF scenario, a backcasting approach, aligns with provincial targets, emphasizing renewable energy development and limiting fossil-based generation. The RE100 scenario enforces the renewable targets of 30% in 2030,70% in 2050, and 100% in 2060. Results show that in Region 1 (Sumatra mainland), RE100 achieves the lowest emissions (2.8 million tonnes CO2) in 2060, with a diversified renewable portfolio and a cost of production of 8.4 cent kWh. Meanwhile, in Region 2 (Nias), RE100 achieves full renewable penetration by 2050, with the lowest emission output (17.8 thousand tonnes CO2) and a cost of production of 12.56 cent kWh. These findings confirm that RE100 is the most effective pathway for North Sumatra and Nias Island to meet renewable energy and emission reduction targets. With optimized energy planning and technology diversification, the region can align with Indonesia's national commitment to achieving 100% renewable energy and Net Zero Emission by 2060. © 2025 IEEE.