The National Grid Corporation of the Philippines (NGCP) is pushing for a mandatory system to track and report rooftop solar installations, warning that unrecorded systems could complicate grid management.

During a media forum Thursday, NGCP assistant vice president and Public Relations Department head Cynthia Perez-Alabanza said the grid operator does not have complete data on the growing number of privately installed rooftop solar systems.

“If there are enough solar installations that NGCP does not know about and there is a sudden cloud cover, it’s as if a large plant connected to the grid falls and NGCP has to manage it,” Alabanza said.

She said sudden weather changes can cause solar generation to drop sharply, resulting in an unexpected change in the amount of electricity available to the grid.

NGCP launched a voluntary data-sharing initiative with distribution utilities and electric cooperatives last year. Alabanza said, however, that an enforceable government policy would give the grid operator more reliable data for long-term planning and operations.

The rapid growth of solar generation has also shifted electricity consumption patterns in the Visayas, with peak demand moving from around 2 p.m. to 4 p.m., when solar output is already starting to decline.

Alabanza suggested prioritizing solar installations in government facilities, including schools and barangay halls, where electricity demand generally coincides with daylight hours.

“Personally, I think solar for government offices is a good starting point. Maybe that’s a better immediate application rather than in bulk,” she said.

Alabanza said NGCP is also prepared to provide technical data if the government revisits the country’s energy mix, particularly on managing the variability of renewable sources.

“We will also give input on how variability should be managed because, at the end of the day, we will be the ones to ensure that the quality coming from intermittent sources is coming out well,” she said.

Meanwhile, NGCP assistant vice president for Visayas Systems Operations Neil Martin Modina said solar accounted for 10.3 percent of the Visayas power supply as of 14 May.

Coal remained the largest source at 43.5 percent, followed by geothermal at 36.5 percent.

Modina recommended assessing future energy mix projections on a per-island basis to account for differences in generation capacity, demand and grid conditions.

The recommendation comes as the country pursues its National Renewable Energy Program targets of a 35 percent renewable energy share by 2030 and 50 percent by 2040.