At least 920,000 customers of the Manila Electric Company (Meralco) experienced rotational brownouts on Wednesday evening, May 13, following tight power supply conditions in the Luzon grid.

In an advisory, Meralco said manual load dropping (MLD) or rotational power interruptions lasting about two to three hours affected households in parts of Batangas, Bulacan, Cavite, Laguna, Metro Manila, and Rizal, reported on Dos Por Dos on Thursday morning, May 14.

According to the National Grid Corporation of the Philippines (NGCP), power reserves became thin due to the forced shutdown of several power plants, resulting in a shortage of more than 3,000 megawatts of electricity supply.

The outages came after the National Grid Corporation of the Philippines (NGCP) placed the Luzon Grid under a "red alert" from 3:00 p.m. to 8:00 p.m. on May 13 due to insufficient power reserves. A yellow alert was also raised earlier from 2:00 p.m. to 3:00 p.m. and later from 8:00 p.m. to 10:00 p.m.

A Red Alert is the highest warning level issued by the grid operator, indicating that the available power supply is not enough to meet demand. Under this condition, rotational brownouts are implemented to prevent a full collapse of the power grid.

Meralco said the controlled outages were necessary to manage the limited supply and stabilize the system during peak demand hours.