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Methodology

Electricity demand and emission share

ASEAN’s power sector emission projections are based on The 8th ASEAN Energy Outlook, while data for the Philippines, Indonesia, and Viet Nam comes from each country’s respective national plans: the Philippines’ Power Development Plan 2023-2050, Viet Nam’s Adjusted Power Development Plan 2021-2030 and Indonesia’s National Electricity Master Plan 2025-2060. Emissions between 2025 and 2030 were calculated using the Compound Annual Growth Rate (CAGR) method.

Electricity demand projections for ASEAN were derived using a CAGR based on the 3.7% historical growth rate between 2022 and 2023. For the Philippines, Indonesia and Viet Nam, demand projections were sourced from the respective planning documents, with the Philippines’ from The Philippine Energy Plan Volume I 2023-2050. CAGR was applied to calculate demand growth for Indonesia and Viet Nam, while the Philippines’ projection was explicitly stated in the plan.

Solar PPA modelling and assumptions

System Advisor Model (SAM) was employed to simulate the internal rate of return of solar utility investment including systems with batteries. Specifically, PVWatts and single owners Power Purchase Agreement (PPA) models were selected for the simulation. 

Site selection: announced projects from Global Energy Monitoring (GEM) were used to scope only technically viable projects within the countries then we select the median solar irradiation projects of the regions based on Global Solar Atlas data as regional representations.

Cost assumptions for base case: Viet Nam was based on Viet Nam technology and storage catalogues 2023, Indonesia was based on Renewable Power Generation Costs in 2024 while the Philippines was based on Bloomberg assumption. Some financial parameters are taken from Loan Thi Do et al (2025). Cost is interpolated for the year of 2025. Generator fixed O&M costs are also drawn from these reports.

The IRR was used as an indicator for project profitability computed based on various parameters which base case assumptions drawn from publicly available sources: PPA price, CAPEX excluding land cost, operation and maintenance cost, annual land cost, inflation rate and bank interest rates. This study also conducts sensitivity analysis of these parameters on IRR. Battery capacity of Viet Nam uses the requirement of 10% solar capacity and 2 hours duration, or 1 MW/2 MWh based on regulations Philippines battery capacity is 20%, 4 hour duration based on DOE, which is same for Indonesia as of assumption of DEA

Acknowledgements

Contributors

Ember: Aditya Lolla, Shiyao Zhang, Tito Das, Matt Ewen, Jivan Zhen Thiru, Reynaldo Dizon, Ardhi Arsala Rahmani

We extend our thanks to Dadan Kusdiana, Secretary General Ministry of Energy and Mineral Resources, Indonesia, and Atem S. Ramsundersingh CEO, WEnergy Global Ptd Ltd (Singapore) for their quotes, and to our external reviewers—WEnergy Global, Gurin Energy, and Inovasi Dinamika Pratama.

Cover image

Aerial view of solar panels and highway in the Philippines.

Credit: Nothing Ahead / Pexels