The Visayas grid will be under a Yellow Alert from 5 p.m. to 8 p.m. Saturday due to tight power supply margins, the National Grid Corp. of the Philippines (NGCP) said.

The grid operator said available capacity is expected to reach 2,487 megawatts against a peak demand of 2,337 MW during the alert period.

NGCP said 21 power plants are contributing to a total of 821.5 MW in unavailable capacity, including eight plants on forced outage and 13 operating at reduced capacities.

The Yellow Alert was attributed mainly to the unavailability of the Visayas' large coal-fired plants TVI 1 and TVI 2, as well as limited power imports from Mindanao due to the maintenance outage of GNPK 2.

NGCP said a Yellow Alert is issued when the operating margin is insufficient to meet the transmission grid's contingency requirement.

The grid operator has repeatedly issued alerts in the Visayas in recent weeks amid plant outages, reduced generation capacity and high electricity demand.