ILOILO CITY — Rooftop solar is spreading across Philippine homes, businesses and other facilities, but the country’s transmission grid operator says a growing information gap could make it harder to manage the power system when sunlight suddenly changes.
The National Grid Corporation of the Philippines (NGCP) is calling for a mandatory policy to track installed rooftop solar systems, warning that the grid operator does not have a complete picture of how much privately generated solar capacity is connected to the system.
The issue was raised during a media forum in Iloilo City on September 24, where NGCP officials discussed how the rapid expansion of distributed solar is changing electricity patterns across the country.
Why NGCP Wants a Complete Solar Inventory
According to NGCP Assistant Vice President and head of public relations Cynthia Perez-Alabanza, the transmission operator can be left without sufficient information about privately installed solar systems.
That becomes particularly important when weather conditions change quickly.
If a large number of rooftop systems are producing electricity and clouds suddenly reduce solar generation, the resulting drop can resemble the unexpected loss of a large generating plant from the perspective of grid management, Alabanza explained.
For NGCP, knowing how much rooftop solar is actually connected to the system would make it easier to anticipate these changes and manage electricity supply and demand.
The transmission operator previously launched a voluntary data-sharing initiative involving distribution utilities and electric cooperatives, but Alabanza said a more enforceable government policy would provide a stronger foundation for long-term planning.
Solar Is Already Changing When Filipinos Use Electricity
The issue is emerging as rooftop and other solar installations become a larger part of the country’s electricity landscape.
NGCP officials said the growth of solar is already affecting electricity consumption patterns, with peak demand shifting from around 2 p.m. to 4 p.m.—a period when sunlight is beginning to weaken.
That transition matters because solar generation naturally varies with weather and time of day.
The challenge for grid operators is therefore not simply how much solar power exists, but when that power is available and how quickly generation can change.
Visayas Already Gets 10.3% of Its Power From Solar
The changing energy mix is particularly visible in the Visayas.
NGCP Assistant Vice President for Visayas Systems Operations Neil Martin Modina reported that solar accounted for 10.3% of the Visayas power supply as of May 14, 2026.
Coal accounted for 43.5%, while geothermal contributed 36.5%, according to the figures presented at the forum.
Those figures illustrate why grid planning is becoming more complicated as renewable sources occupy a larger share of the electricity mix.
Modina recommended that future energy-mix projections be assessed on a per-island basis, rather than treating the entire Visayas as one uniform system.
That approach could help account for differences in generation, demand and transmission conditions among individual islands.
NGCP Suggests Starting With Government Buildings
Rather than simply encouraging a rapid expansion of rooftop solar everywhere, Alabanza suggested that government facilities could provide an immediate focus.
Schools and barangay halls, for example, typically have significant electricity demand during daylight hours—the same period when solar generation is strongest.
She suggested that government facilities could therefore be a practical starting point for solar deployment, rather than pursuing installations in bulk without considering how their generation profiles fit into the grid.
The proposal comes alongside broader government efforts to expand rooftop solar.
The Department of Energy has been pushing to streamline the net-metering program, which allows qualified consumers with renewable-energy systems to use the electricity they generate and receive credits for excess electricity exported to the grid. The DOE said more than 20,000 consumers nationwide had joined the program in 2025.
This Is About Visibility, Not Stopping Rooftop Solar
The latest NGCP proposal does not mean the transmission operator is calling for an end to rooftop solar.
Instead, the central issue is visibility.
As more households and businesses generate electricity themselves, grid planners need reliable information about where those systems are located, how much capacity they have and how their output may change.
That information can help operators prepare for periods when solar generation falls sharply because of clouds, storms or the natural decline in sunlight later in the day.
The DOE’s own 2026 policies have continued to support rooftop solar adoption while retaining technical safeguards intended to protect distribution-system reliability.
The Bigger Challenge: More Renewable Energy, More Flexible Grid Management
The Philippines is pursuing a larger renewable-energy role in its electricity mix.
NGCP officials noted that the country is working toward the National Renewable Energy Program targets of a 35% renewable share by 2030 and 50% by 2040.
Reaching those targets will require more than installing additional solar panels.
It will also require better forecasting, accurate information about distributed generation, adequate transmission capacity and systems capable of responding when renewable output changes.
That challenge is particularly relevant in the Visayas, where the power system has already experienced supply pressures. Earlier this month, NGCP said the Visayas grid had recorded numerous yellow and red alerts in 2026 amid low available capacity, while the Department of Energy was pursuing additional battery-storage capacity and the return of several unavailable power plants.
Battery systems can help by storing electricity generated during periods of strong solar production and making energy available later when demand rises.
What Happens Next Could Shape the Philippines’ Solar Boom
The Philippines is moving toward a future in which more consumers generate at least some of their own electricity.
But the faster rooftop solar expands, the more important it becomes for grid operators to know exactly what is connected to the system.
NGCP’s call for mandatory reporting therefore highlights a central challenge of the country’s clean-energy transition: how to add more renewable generation without losing visibility over the grid that has to balance it.
For Filipino households and businesses considering rooftop solar, the latest development is not a warning against solar power. It is a sign that the country’s energy system is entering a phase where distributed generation is becoming significant enough to require more detailed planning and coordination.
And as solar’s share continues to grow, the question may no longer be simply how many panels the Philippines can install—but whether the grid can keep pace with everything happening above the rooftops.
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