Southeast Asia's reliability challenge is changing. Electricity demand is rising at the same time as renewable generation is taking a larger role in the energy mix. For utilities and policymakers, the question is therefore no longer simply whether sufficient capacity exists, but whether the power system has the capabilities required to respond as demand, renewable output and grid conditions change.

For Pieter Hokkeling, that distinction matters because reliability and decarbonisation are too often framed as competing goals. In his view, they can and must be advanced together. Achieving this requires a holistic, system-level approach to power system planning and the right combination of renewables, storage and flexible generation.

"The challenge is not choosing between cleaner power systems and reliable power systems," says Hokkeling. "It is designing systems that can achieve both outcomes simultaneously."

Reliability beyond installed capacity

Historically, reliability was largely assessed according to whether sufficient generation capacity was available to meet peak demand. That approach was suited to power systems dominated by large, dispatchable thermal plants operating as baseload power against relatively predictable demand patterns.

Southeast Asia is now moving into a different operating environment. Electricity consumption is increasing due to industrial development, urbanisation and the expansion of digital infrastructure, including data centres. At the same time, variable renewable generation is taking on a larger role within the energy mix.

“The amount of installed capacity tells only part of the story, Hokkeling explains. “What matters more is whether the system can respond effectively as operating conditions change.”

A ower system may have sufficient megawatts available on paper and still encounter operational constraints when renewable output changes rapidly, demand rises unexpectedly or the grid requires additional support. Reliability therefore depends increasingly on how different generation assets perform under changing conditions, not simply on whether they are technically available.

This calls for a more comprehensive assessment of system capabilities. Planners need to consider fast starting, repeated ramping, efficient part-load operation, reserve provision, frequency and voltage support, black-start capability and fuel resilience. Together, these capabilities determine whether a power system can accommodate a more variable generation mix while continuing to provide reliable electricity to industry, businesses and consumers.

Different assets, complementary roles

The discussion about future generation is often framed as a choice between renewable energy and firm capacity. This framing misses the fact that different technologies have distinct, complementary roles within a reliable power system.

"A megawatt of solar, a megawatt of storage, and a megawatt of dispatchable generation do not provide the same system service," states Hokkeling.

Renewables provide low-carbon electricity when wind and solar resources are available. Battery storage can respond rapidly to short-term imbalances and shift energy across time. Flexible generation such as reciprocating engines serves another essential role. It can start and stop quickly, adjust output as conditions change, provide reserves and support the grid during periods of low renewable generation or unexpectedly high demand.

"The real question is not renewables versus firm capacity," says Hokkeling. "It is whether the system has the right portfolio of capabilities."

This requires a more careful assessment of firm capacity itself. "Not all firm capacity is equal; what we need in a high renewables system is flexible firm capacity," says Hokkeling. If flexibility is missing, renewable deployment can run into curtailment, congestion, and reliability concerns.

The value of an asset therefore depends not only on how many megawatts it represents, but also on how quickly, efficiently and repeatedly it can respond. From a system perspective, the objective is not to maximise one technology or source of generation, but to develop an optimal combination of assets that can meet demand, integrate an increasing share of renewables and maintain grid stability and reliability under a wide range of operating conditions.

Making better use of existing flexibility

As demand grows and more variable renewables are added in Southeast Asia's electricity systems, new investments in generation and infrastructure will be needed. However, before deciding how much new capacity to add, planners should take a system-level approach to establish what the existing system is already capable of providing.

In many power systems, some degree of operational flexibility may already exist within the generation fleet but is not always fully recognised, contracted or rewarded. Existing plants may be capable of faster response, more frequent ramping or more efficient part-load operation than current dispatch arrangements require. Improvements to forecasting, operating rules and grid codes may also allow these capabilities to be used more effectively.

This creates an important distinction between flexibility that genuinely needs to be added and flexibility that is already technically available but remains underutilised. If services such as reserve provision, repeated ramping or part-load operation are not captured in planning models, procurement arrangements or market structures, valuable capabilities can remain largely invisible even though the assets are already connected to the system. "The planning challenge is to make sure those capabilities are visible, valued and deployed where they deliver the greatest benefit to the system," Hokkeling says.

Optimising existing assets does not remove the need for new investment. As electricity demand and renewable penetration increase, additional flexible generation and grid infrastructure will be required where current capabilities are insufficient. However, understanding the existing system first provides a more disciplined basis for deciding what should be optimised, upgraded or added.

Planning for flexibility from the outset

One of the clearest lessons from Southeast Asia is that flexibility becomes more valuable as power systems become more complex. Across the region, electricity demand continues to rise while renewable generation forms a larger share of the energy mix. If flexibility is not built into planning, procurement and market rules early, countries risk discovering the need for it only after curtailment, reserve shortages, grid instability or reliability events appear.

Indonesia is a good example of why this matters. Power planning discussions in the country recognise flexible generation as part of the future system, and Wärtsilä already has a significant installed base there. Flexibility is therefore not just a future concept: in many cases, the assets, expertise and operating experience already exist. The planning challenge is to make sure those capabilities are visible, valued and deployed where they deliver the most system benefit.

Directing investments where they create the most system value

Grid investment, flexible generation and asset optimisation should not be treated as separate workstreams; they solve different parts of the same reliability challenge. The sequence of investment decisions matters. In the near term, utilities and system planners can improve forecasting, dispatch practices, operating rules and the use of existing generation assets.  New flexible capacity and network investment can then be directed towards the locations and requirements that these measures cannot adequately address.

This approach also changes how long-term investment decisions should be assessed. A power plant commissioned today may remain in operation for several decades, during that time, renewable penetration, demand patterns, fuel availability, market structures and policy requirements are all likely to evolve.

An asset that appears attractive based primarily on its initial capital cost may provide less value over its lifetime if it cannot adapt to changing conditions. Conversely, a flexible asset may deliver broader value by supporting renewable integration, responding to demand changes and providing essential grid services at different stages of the energy transition.

This is why Wärtsilä places particular emphasis on flexibility, modularity and future-fuel readiness. The relevant question is not simply how an asset will operate when it enters service, but whether it can continue to support system reliability as the generation mix, market environment and operational requirements around it change.

"The right investment is not simply the lowest-cost asset on day one,” says Hokkeling. “It is the asset that can continue to support reliability and decarbonisation as the system evolves."

Turning technical capability into usable value

Technical flexibility only benefits the power system if it can be called upon when needed and appropriately recognised in planning, procurement and market structures.

As Hokkeling notes, flexibility that already exists in the fleet is not always recognised, contracted or rewarded. A plant may be capable of fast starting, repeated ramping or reserve provision. However, if these capabilities are not reflected in how the asset is dispatched, contracted or compensated, their value to the system may remain unused.

A market structure that values primarily energy volume or installed capacity can overlook some of the capabilities required to integrate higher shares of renewable generation. Mechanisms that recognise the different capabilities provided by each asset can give planners a clearer view of what is already available and where further investment will create the greatest system value.

The technical and commercial dimensions of flexibility must therefore reinforce one another. Power systems cannot rely on capabilities that planning and market structures do not recognise. Equally, market mechanisms cannot create flexibility where the necessary physical capabilities do not exist.

Looking beyond day one

Increasingly discussions with customers start with the role an asset will play within the future power system, not simply how it will operate on day one," Hokkeling says. This means considering today’s requirements alongside the changes likely to take place over the asset’s lifetime.

"What do they need today? What changes when more renewables connect? What happens when market rules change? What fuels might be available later?" Hokkeling asks. "And how can today's investment avoid becoming tomorrow's constraint?"

The most successful projects are those that balance immediate operational needs with the ability to respond to future changes. This allows reliability and decarbonisation objectives to advance together rather than being treated as competing priorities.

For ASEAN's increasingly complex power systems, reliability will depend on more than adding sufficient capacity to meet future demand. The sector needs to move beyond discussing installed capacity in isolation and focus on overall system capability. Existing and future assets must be planned as part of an integrated system and capable of working together across a wider range of operating conditions.

The practical next step is to build flexibility into planning and procurement from the start. That means asking whether an asset can start quickly, ramp repeatedly, operate efficiently at part load, provide reserves, support grid stability and adapt to future fuels. It also means ensuring market mechanisms reward those capabilities.

Ultimately, reliability and decarbonisation are not competing objectives. The most resilient power systems of the future will likely be those that combine multiple technologies in ways that support reliability, affordability and emissions reduction at the same time. The reliability equation is therefore becoming less about the number of megawatts installed and more about whether the power system has the flexibility to use those megawatts effectively when conditions change.