The 10 countries in the Association of Southeast Asian Nations (ASEAN) are home to 615 million people, fast-growing economies and rising energy demand. Unevenly distributed fossil fuel resources are a challenge to the security of energy supply, as is deteriorating environmental conditions resulting from fossil fuel dependency. The region’s external costs caused by air pollution from fossil fuel combustion will increase by 35%, jumping from USD 167 billion in 2014 to USD 225 billion in 2025, according to an IRENA–ASEAN regional REmap analysis.