The National Grid Corporation of the Philippines (NGCP) placed the Visayas grid under yellow and red alerts from Tuesday afternoon to evening.  

In its Visayas Grid Alert advisory, NGCP announced yellow alerts from 3 p.m. to 5 p.m. and 7 p.m. to 8 p.m., with a red alert issued from 5 p.m. to 7 p.m. on 15 September.

“A yellow alert is issued when the operating margin is insufficient to meet the transmission grid’s contingency requirement,” NGCP said in its advisory.

Groups calls battery storage deployment

The Institute for Climate and Sustainable Cities (ICSC) has proposed the deployment of distributed renewable energy and battery storage systems to address recurring grid alerts and high Wholesale Electricity Spot Market (WESM) prices in the Visayas.

The region has recorded 134 yellow or red alert days in 2026 as of September 14, consisting of 94 yellow alerts and 40 red alerts, highlighting persistent power supply constraints.

“Battery energy storage systems should not be treated merely as a short-term fix to the unfolding power crisis in Visayas—they are the core solution on both the short and long-term,” said Alberto Dalusung III, ICSC’s Energy Transition Advisor.

“When paired with renewable energy, battery storage directly bridges the critical supply gap without waiting years for new generation and transmission projects to be built. We can act now because these technologies can be deployed rapidly to meet our immediate energy needs,” Dalusung added.

ICSC said the frequent grid alerts were largely driven by unplanned and extended outages of large coal-fired power plants, whose shutdowns can remove hundreds of megawatts from the system at a time.

Among the plants that have experienced significant outages are Therma Visayas Inc. Unit 1, which has been offline for 125 days since May 3; TVI Unit 2, which has been offline for six days since September 9 after previously being out of service for 161 days from March 24 to August 31; and Panay Energy Development Corp. Unit 3, which has been offline for 16 days since August 29.

TVI 1, with a capacity of 150 megawatts (MW), was expected to return on September 15, while TVI 2, also with a 150-MW capacity, has no indicative return date. PEDC 3, likewise with a 150-MW capacity, was previously targeted to return by October 3 but its return has been pushed to the end of October.

Cebu Energy Development Corp. Unit 1, with an 82-MW capacity, was also offline for 42 days from July 24 to September 3.

ICSC said the loss of capacity from large coal units becomes more critical when several plants are unavailable at the same time, particularly during peak demand hours when the grid has less reserve capacity.

It added that power sharing between grids may not be enough to address the problem when neighboring systems are also experiencing supply constraints.

“Unplanned and extended outages from coal power plants are the primary driver of these frequent grid alerts, particularly during peak demand hours when the system has the least room to absorb the loss of a large generating unit,” ICSC said.

The group said the solution should focus on flexible generation and storage rather than relying solely on additional large baseload power plants.

It said distributed renewable energy paired with battery storage could provide the flexibility needed to respond quickly to sudden supply shortages.

According to ICSC, rooftop solar can serve local electricity demand during the day, while battery energy storage systems can provide fast-responding power during peak hours.

“These resources do not replace large generators or transmission infrastructure; rather, they add a critical layer of resilience around them,” the group said.

ICSC also welcomed plans for battery energy storage system (BESS) facilities in the Visayas, noting that simulations by the Department of Energy (DOE) showed that 200 MW of battery storage capacity could reduce the occurrence of yellow and red alerts by half.

The group said accelerating distributed generation and battery storage could provide a faster response to afternoon and evening supply shortages while complementing existing thermal power facilities.