By Ms Busadee Santipitaks, Chief Executive Officer, Mekong River Commission Secretariat*

When you flip a light switch or charge your phone, you’re tapping into an intricate energy web that’s quietly transforming across Southeast Asia. With electricity demand projected to more than triple by 2050, the Mekong region is standing at a crossroads: continue relying on carbon-heavy sources or leap toward a greener, more flexible future.

As the world increasingly shifts towards renewable energy sources like solar and wind, however, due to their intermittency issues, the need for energy storage solutions becomes paramount. This is where pumped storage hydropower, with its ability to store excess energy and release when needed, could play an important complementary role. This technology, often described as a “giant water battery” or long duration energy storage, could become the cornerstone of the region’s transition to reliable, renewable, and resilient energy systems.

Pumped storage hydropower works on a simple yet powerful principle. When excess solar or wind energy is available, water is pumped from a lower reservoir to a higher one. When demand surges, like at night or during cloudy days, the stored water is released downhill to generate electricity. This approach doesn’t just store energy; it balances the grid and ensures consistent power supply, day and night, rain or shine.

Think about this: as the Mekong region increasingly embraces solar and wind power, how will pumped storage hydropower ensure a stable and reliable energy supply?

Addressing this challenge requires looking beyond individual energy projects and considering how water and energy systems can be planned together across the basin. Regional assessments can help identify opportunities to expand renewable energy while balancing environmental, social and economic considerations.

One recent basin-wide analysis conducted by the Mekong River Commission (MRC) and the Australian National University identified more than 18,000 potential pumped storage hydropower sites across the Lower Mekong Basin. The findings suggest that these sites – which are off-river, closed-loop pairs rather than new dams on the river itself – could provide far more storage than the region would ever need to support a fully renewable grid. Only a small fraction would ever be built; the real task is to identify the best sites.

What makes the Mekong especially promising is its natural alignment between solar and hydro energy sources. Solar power is plentiful during the dry season, compensating for reduced hydropower output. When integrated with pumped storage hydropower for stability, this combination could create a strong, climate-resilient power grid across Cambodia, Lao PDR, Thailand and Viet Nam.

The numbers help illustrate the scale of the opportunity. Conventional hydropower, for example, requires huge dams that flood vast areas of 3,316 square kilometres of land to manage flood and drought that could produce a lot of electricity of 44 TWh/year. But with solar energy available all over Mekong, pumped hydro energy storage facilities require as little as 3-20 square kilometres of land area and 230 square kilometres of solar panels, compared to the thousands of square kilometres needed for conventional dams. Using a system that mainly combines wind, solar, and pumped hydro energy storage is actually cheaper in the long run considering that renewable energy technology cost of system drops rapidly in recent years. Also, pumped storage hydropower projects have been seen provide less pressure on water demand when it combines with conventional hydropower too.

Greater regional cooperation, such as the Greater Mekong Subregion power trading frameworks and the ASEAN Power Grid including MRC, could unlock additional benefits for the Mekong countries. Power trading could become more efficient, renewable energy projects could expand at scale, and pumped storage facilities could help stabilise interconnected electricity systems. Existing reservoirs could also support multiple objectives, including energy generation, irrigation and flood management, while complementing and maximising the benefits of existing hydropower assets.

Across the Mekong region, Cambodia, Lao PDR, Thailand, and Viet Nam are all exploring wind power, with Viet Nam currently leading in installed capacity and project development, while the others continue to address infrastructure, financing and regulatory hurdles.

So, how do we ensure that new infrastructure, especially in greenfield sites, doesn’t disrupt ecosystems and displace communities?

The MRC’s proactive regional planning study, which shifts from reactive to proactive planning by identifying and assessing supplementary investment projects and enabling activities, will be essential to ensure that new energy infrastructure contributes to development pathways that meets growing energy demand while taking account of environmental sustainability, social well-being and transboundary considerations.

Pumped storage hydropower could become an important component of the Mekong region’s energy transition. It will be successful only if it is rooted in careful planning, informed by science, and grounded in the realities for  those who live along the river.

As Mekong countries lights up with ambition and innovation to pursue their clean energy and climate goals,  this is the chance to start powering the Mekong’s future with pumped storage hydropower – let’s do it right.

*About author

Ms. Busadee Santipitaks, appointed as the first female and fourth riparian CEO of the MRC Secretariat in January 2025, brings nearly four decades of diplomatic experience from Thailand’s Ministry of Foreign Affairs. She has served as Deputy Permanent Secretary, Ambassador to Australia, MFA Spokesperson, and Thailand’s Permanent Representative to ASEAN, with key postings in Brussels and New York. A strong advocate of multilateral and inclusive regional cooperation, she holds degrees from the University of Delhi and The Fletcher School, Tufts University.