For Akihiro Ondo, Managing Director and CEO of Mitsubishi Power Asia Pacific, the future role of ASEAN’s existing thermal plants will not be determined by age alone, but by whether plant owners act early enough to improve performance, build in flexibility and prepare assets for an evolving fuel mix.  

As electricity demand grows and more renewables come online, these decisions are becoming more important. As Ondo explains: “Energy resilience is more important now than ever. Across ASEAN, electricity demand is growing quickly due to economic growth, industrialisation and digitalisation.” 

In this edition of In-Between the Lines, he explains how lifecycle planning can help determine which assets may still play a responsible role and which should retire, before technical constraints and time pressure narrow the choices available. 

Existing capacity is not inherently transitional 

Existing thermal plants are frequently described either as essential sources of reliability or as obstacles to decarbonisation. In practice, their role depends on how they are operated and adapted as the power system changes. 

This is particularly important as more renewable energy enters ASEAN’s grids. “The role of thermal generation is changing. It is no longer just about providing baseload power. It also needs to respond quickly and support the grid when solar or wind power is not available,” Ondo explains. 

A plant that continues to run without improvements to efficiency, flexibility or emissions performance may become harder to reconcile with a lower-carbon system. But an asset that is assessed early, maintained strategically and adapted to changing requirements may provide the firm capacity needed while renewable generation and grid infrastructure continue to develop. 

The dividing line is not simply the age of the equipment. It is whether the plant has been given a credible pathway to operate flexibly. 

Planning must begin before the end of design life 

Decisions about existing plants are often made when equipment is approaching retirement or requires major maintenance. By then, however, some options may have narrowed. 

There is also no single pathway that applies to every asset. “There is no one-size-fits-all answer. Whether it's a new build, life extension, modernisation or retirement, every decision depends on the technical condition of the asset, the economics, and the regulatory environment, while ensuring the power system remains reliable,” Ondo says. 

Timing is becoming an increasingly important part of that decision. As Ondo explains, “One thing we are seeing today is that operators need to start planning much earlier. Given current market conditions and longer lead times for critical components, life extension and modernisation programs should be evaluated well before a plant reaches the end of its design life.” 

Early planning does not mean extending the life of every plant. Rather, it gives owners the time and information to compare their options. By assessing assets earlier, operators can weigh maintenance and upgrades against repowering, new-build projects or retirement, while considering reliability, cost and decarbonisation together. 

Modernisation can reposition an asset 

Vietnam’s O Mon 1 plant provides a practical example of how an existing facility can be adapted to changing energy needs.  

Originally designed to operate on oil, the plant is being upgraded to use natural gas. Mitsubishi Power is supplying new burners for the conversion and adding a selective catalytic reduction system to further reduce nitrogen oxide emissions. 

The project demonstrates that modernisation can give selected existing assets a different role in the energy system. “This shows that existing assets can also be modernised to improve efficiency, reduce emissions and continue providing reliable electricity for many years,” Ondo says. 

At the same time, new high-efficiency generation is being developed in the adjacent O Mon 4 GTCC project. 

The two projects illustrate how upgrading existing capacity and investing in new generation can work in parallel. As Ondo notes, “At the same time, just next door, we're supplying two advanced JAC gas turbines for the new O Mon 4 GTCC project, creating a good example of how upgrades and new investment can work together to support Vietnam's long-term energy transition.” 

This is particularly relevant in markets where electricity demand is growing quickly. Modernising selected assets can help maintain reliable supply while newer technologies and supporting infrastructure are developed. 

Designing for an uncertain fuel pathway 

Early planning becomes even more valuable when the future fuel mix remains uncertain. Hydrogen, ammonia and carbon capture may contribute to the decarbonisation of firm generation, but their commercial readiness and supporting infrastructure will vary considerably across ASEAN. 

Operators cannot assume that these options will become available at the same time or cost. But they can make investment decisions today that keep future options open. For example, turbines designed with the potential to co-fire hydrogen can help operators prepare for lower-carbon fuels before they are widely available. 

This reflects a broader role for gas-fired generation in the transition. As Ondo explains, “That's why high-efficiency gas-fired generation remains essential. It provides reliable, dispatchable power to support energy resilience today while creating a practical pathway to lower-carbon fuels such as hydrogen in the future.” 

This approach is not a commitment to one predetermined technology pathway. It is a way of avoiding premature constraints, particularly for assets expected to operate over several decades. 

From inherited asset to managed pathway 

Existing thermal capacity becomes harder to manage when decisions about its future are left until action is unavoidable. Operators may then face a narrower set of options: extend an asset with limited improvements, retire capacity before a suitable replacement is available, or absorb higher costs to make changes at short notice 

Starting earlier allows individual asset decisions to be considered as part of a wider transition involving generation, grids and fuel supply. As Ondo says, “The conversation should focus on planning earlier and taking a more integrated approach to generation, grid infrastructure and fuel supply, so the right capacity is in place when it's needed.”. 

Some plants will still retire. Others may be converted, modernised or prepared for future fuels. At the same time, renewable energy and firm generation will need to develop together. 

For Ondo, these should not be viewed as competing priorities. “At the same time, we need to continue accelerating clean energy deployment alongside investments in firm, flexible generation. These are complementary parts of the energy transition and need to be developed together to deliver reliable, affordable and lower-carbon power.” 

The relevant question is therefore not whether existing thermal generation belongs in the transition as a category. It is whether each asset has been examined early enough to determine what role, if any, it can responsibly perform. 

Doing so will require coordination across the energy system. As Ondo concludes: “Ultimately, securing the future of firm capacity will require close collaboration across governments, utilities, technology providers and the broader energy ecosystem.”