This policy brief examines how Energy Service Companies (ESCOs) can be scaled to accelerate ASEAN’s transition to low-carbon buildings through energy efficiency (EE). It highlights EE as the region’s most cost-effective decarbonisation pathway, capable of reducing building-sector emissions, avoiding costly grid investments, and strengthening energy security amid rapid urbanisation and rising cooling demand. The brief explains the ESCO value proposition, integrated, performance-based services covering audits, financing, implementation, and measurement and verification, which lowers upfront costs and makes energy savings bankable for building owners.