More than 200,000 customers in the Manila Electric Co. (Meralco) franchise area experienced rotating power interruptions after the national grid was placed under “Red Alert” due to major plant outages and transmission line failures.

Meralco implemented emergency manual load dropping in the afternoon as peak demand reached 12,537 megawatts, surpassing the available capacity of 12,447 megawatts.

The rotating brownouts, which lasted an average of three hours, affected parts of Metro Manila, Batangas, Bulacan, Cavite, Laguna and Rizal.

The National Grid Corporation of the Philippines (NGCP) raised the Red Alert for the Luzon Grid from 3 p.m. to 8 p.m. after 4,681.6 megawatts became unavailable.

The Department of Energy (DoE) said the shortage was triggered by the tripping of the 500-kilovolt Tayabas-Ilijan and Dasmariñas-Ilijan transmission lines.

It disconnected the 1,200-megawatt Ilijan power plant and three EERI units. The deficit worsened later that morning when the 325-megawatt Masinloc Unit 3 went on a forced outage.

DoE Secretary Sharon Garin directed the NGCP to resolve the transmission issues and ordered the San Miguel Power Group to restore the Masinloc unit immediately.

“The DoE is managing both situations in real time,” Garin said. “Our directive is to restore normal conditions as quickly as possible.”

The Visayas Grid was also placed under Red Alert during the same period Tuesday. The NGCP cited that 12 plants in the Visayas have been on forced outage since March, leaving 862.3 megawatts unavailable.

To mitigate the crisis, Meralco activated its Interruptible Load Program, securing 240 megawatts of de-loading capacity from commercial and industrial customers who switched to their own generators.

Despite the grid instability, the NGCP announced Wednesday that transmission charges on May electricity bills are set to decline.

The average transmission rate fell 8.8 percent to P1.5983 per kilowatt-hour, down from P1.7526 in March. The decrease was driven by a 14.16 percent drop in transmission wheeling rates and a 5 percent reduction in ancillary services charges.

“For the May electric bill, NGCP charges only 60 centavos per kilowatt-hour for the delivery of its services,” the grid operator said.

The NGCP clarified that while ancillary services — reserve power used to stabilize the grid — make up the bulk of transmission costs, the company does not earn from those rates. The fees are remitted directly to the power generating companies.