Energy system modeling in South and Southeast Asia: Progress, gaps, and opportunities

As the global energy system pivots toward security and sustainability, the South and Southeast Asian regions stand at a critical juncture: balancing rapid demand growth, infrastructure needs, and global climate goals. This review systematically examines how energy system models have been applied across countries in the region, evaluating their coverage of low-carbon technologies, storage options, carbon removal, and demand-side dynamics, while identifying key gaps between national policy commitments and the modeling literature. This study draws on a systematic review of 97 peer‑reviewed modeling studies published between 2000 and 2025. The analysis maps coverage across sectoral, temporal, spatial, and technological patterns, categorizes the primary modeling tools used, and evaluates how well these categorizations align with declared national energy targets. Key findings reveal that, so far, the models are overwhelmingly focused on the electricity sector, using solar, wind, hydro, and biomass, while long-duration storage and carbon removal technologies remain underrepresented. Demand-side flexibility, cross-border trade, socioeconomic co-benefits, and just transition metrics also remain underexplored. Many models stop at national scales and long-term horizons, limiting their utility for subnational planning and near-term policy design. While India, Indonesia, and Vietnam lead in modeling exercises, countries such as Brunei, Cambodia, Myanmar, and Sri Lanka lack comparable studies. This study confirms that energy system modeling capacity and application in South and Southeast Asia have advanced over the past years, and future research should integrate demand-side solutions, advanced storage and flexibility options, together with negative emissions technologies, multisector coupling, regional grid interconnections, and socioeconomic drivers to better understand the equitable and just transition pathways. • Energy system modeling efforts in South and Southeast Asia have progressed significantly. • Low-carbon technologies like CCS, hydrogen, and ocean energy remain underexplored. • Models need to include cross-border regional power interconnections and trade. • Models focus less on demand-side solutions and advanced storage compared to supply-side solutions. • There is a need for integrating equity and just-transition dimensions.