Decarbonisation of ASEAN Energy Systems: Optimum Technology Selection Model Analysis up to 2060 - Updated 2025

This report examines long-term decarbonisation pathways for ASEAN energy systems through 2060 using an optimal technology selection model developed by the Institute of Energy Economics, Japan (IEEJ). Updated for 2025, the analysis incorporates revised macroeconomic and energy service demand assumptions, as well as enhanced geographic information system (GIS)-based assessments of renewable energy potential across the region. The results reaffirm that energy efficiency improvements and electrification of end-use sectors, underpinned by a low-carbon power supply, remain central to ASEAN’s decarbonisation strategy. At the same time, the analysis underscores the need for a diversified technology portfolio to address rapidly growing energy demand and the region’s continued structural reliance on fossil fuels. Transitional options – including fuel switching from coal to natural gas, co-firing with biomass, hydrogen, and ammonia, and the deployment of carbon capture, utilisation, and storage (CCUS) in fossil fuel-based power generation – play a critical role in reducing emissions during the transition period. A key enhancement in this edition is the inclusion of a detailed country-level analysis for Viet Nam. This case study demonstrates how national circumstances can significantly shape decarbonisation pathways, technology choices, and system costs, even within a common regional framework. By providing a cost-optimal, system-wide assessment of decarbonisation pathways at both regional and national levels, this study offers a quantitative ‘second opinion’ to support ASEAN countries in developing realistic energy transition road maps and engaging in constructive dialogue with international partners, while balancing decarbonisation objectives with economic growth and energy security.