Recent yellow and red alerts in the Philippine power grid are being driven more by aging coal plants than by variable renewable energy, the Institute for Climate and Sustainable Cities (ICSC) said on February 10. In a position paper, the group emphasized that true reliability depends on the grid’s flexibility to respond to sudden changes in supply and demand.

“The goal of any power system should not be to eliminate variable resources, but to build a flexible system that can thrive amid this natural variability,” the ICSC said.

Coal currently accounts for roughly 60% of the country’s electricity generation. Many of these plants are decades old and increasingly prone to forced outages due to maintenance issues, equipment failures, or extreme heat. When large coal units suddenly go offline, the grid must dispatch quick-start, diesel-fired generators, which are costlier and can push electricity prices higher while triggering alerts.

“System reliability does not depend on any individual generator operating continuously for 24 hours. Instead, it depends on the grid’s ability, as a whole, to meet demand at all times despite these sources of variability,” ICSC added.

Daily electricity demand also fluctuates with weather and industrial activity, creating spikes or drops in consumption. Solar and wind generation, though variable, follow predictable cycles, and modern forecasting allows operators to anticipate changes. In contrast, unplanned coal outages are harder to manage and more disruptive.

ICSC, a Philippine-based non-government climate and energy policy group, called for a stronger focus on flexibility, including fast-acting generators, storage, grid modernization, and improved interconnections, to ensure reliable and cost-efficient electricity.

As the Philippines balances coal dependence with renewable growth, how should policymakers and utilities prioritize grid flexibility?  

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