Iloilo ranks high in solar, lacks full registration

By Francis Allan L. Angelo

A groundbreaking solar mapping tool has revealed that Iloilo City harbors immense rooftop solar potential, with 8.7 megawatts (MW) of solar capacity detected—but more than half of this remains unregistered, according to findings from the Institute for Climate and Sustainable Cities (ICSC).

The tool, called the Solar Power Estimation of Capacities and Tracking Using Machine Learning (SPECTRUM), was officially launched on July 15, 2025, in Quezon City.

Developed by ICSC, the web-based platform is designed to provide granular, city-level visualizations of installed rooftop solar capacity across the Philippines using machine learning and satellite data.

According to the tool’s estimates, only 3.91 MW of rooftop solar installations in Iloilo City are officially registered, leaving 4.79 MW – more than 55% – unregistered.

That brings the city’s solar registration rate to just 44.9%, highlighting a critical gap between the actual installed base and formal energy reporting mechanisms.

Iloilo City’s detected capacity places it among the top urban solar adopters nationwide. It ranks 10th for Commercial and Industrial (C&I) solar photovoltaic (PV) installations at 4.39 MW, and 8th for Residential PV installations with 4.30 MW, reflecting balanced growth across sectors.

However, the low registration rate presents a regulatory challenge.

“Despite being unregistered, these growing capacities could still contribute significantly to renewable energy generation targets,” said Jephraim Manansala, ICSC’s Chief Data Scientist. “That’s why we need a clearer, more granular view of what’s already on the ground.”

The platform also estimates that Iloilo City has over 1,145 hectares of total rooftop area, yet only 6.2 hectares are currently covered by solar panels, translating to a solar coverage rate of just 0.54%.

This points to vast untapped potential that could help the city transition faster toward clean energy.

Nationally, the SPECTRUM tool mapped 1,846.08 MW of rooftop solar capacity across 174 cities and municipalities, including 1,309.64 MW in Luzon, 472.48 MW in the Visayas, and 61.08 MW in Mindanao.

The capacity was broken down into:

• 1,398.25 MW for utility-scale solar projects(over 1 MW),
• 8 MW for residential systems(under 100 kW, typically under the Net-Metering Program),
• 03 MW for commercial and industrial installations(above 100 kW, under the Distributed Energy Resources or DER Program).

SPECTRUM uses high-resolution satellite imagery and a machine learning model trained on localized datasets. The model achieved an overall precision rate of 85.41%, a recall of 90.71%, and an F1 score of 87.98%, with utility-scale installations demonstrating the highest detection accuracy at 98.47%. Precision rates for residential and commercial/industrial installations were 87.6% and 87.1%, respectively.

According to Manansala, unregistered and behind-the-meter systems—solar facilities installed for self-consumption and not connected to the grid’s formal reporting mechanisms—are rising rapidly, especially in urban centers.

“Rooftop solar adoption is rapidly growing, especially for own-use installations in homes and businesses,” he said. “These challenge distribution utilities to adapt their operations and planning.”

The implications are significant for Iloilo City, where unregistered systems could disrupt accurate demand forecasting, Renewable Portfolio Standards (RPS) compliance, and the city’s broader energy transition goals.

“SPECTRUM helps us see what is otherwise invisible to regulators and planners,” said Angelo Kairos dela Cruz, ICSC’s Executive Director. “Solar energy is not just about sustainability—it’s about economic empowerment, especially for underserved and last-mile communities.”

National and local energy planners echoed the tool’s importance.

“Metrics are essential – they serve as our compass,” said Department of Energy (DOE) Undersecretary Felix William Fuentebella. “By consistently using a spectrum of tools to track these metrics, we can unite people and leaders – across barangays, provinces, cities, and the nation—around a shared vision.”

Former Maldives President Mohamed Nasheed, speaking as CVF-V20 Secretary General, emphasized that “data-informed knowledge is transformative power” for climate-vulnerable countries like the Philippines.

Iloilo City’s position in both residential and commercial rooftop solar rankings shows how strategic investments and awareness campaigns could drastically raise its contribution to renewable generation.

Nationwide, other cities outpace Iloilo in formal registrations. Bacolod City tops the list with a solar registration rate of 119.2%, followed by Santa Rosa (119.9%) and Calamba (85.9%). By contrast, Iloilo’s 44.9% underscores the urgent need for policies that formalize existing systems.

SPECTRUM aims to support stakeholders across the energy landscape:

• Local Government Units (LGUs)can use it to guide zoning and development aligned with real solar activity.
• Electric cooperatives and distribution utilitiescan refine demand projections and plan grid upgrades.
• Developers and solar providerscan identify new market opportunities.
• NGOs and academic institutionscan ground advocacy and research in spatially accurate data.

The platform also enables public access to city-level and aggregated national data via icsc.ngo/solar-mapper, though it cautions that results are not official and subject to limitations in satellite resolution, shading, and estimation methods.

The tool’s model assumes a conservative conversion of 1 hectare = 1 MW, which may not always reflect actual capacity due to differences in panel efficiency, layout, and installation types.

ICSC plans to expand the geographic coverage of SPECTRUM, enhance model precision with more localized training datasets, and revisit previously mapped areas to monitor growth over time.

“This project is not a one-time snapshot,” Manansala said. “We will continue to scale geographically, refine our model, and track solar adoption trends over the years.”

Iloilo City’s untapped rooftop solar capacity, if properly integrated into official energy planning, could position it as a regional leader in renewable energy, helping the country meet its long-term targets of 35% renewable energy share by 2030, 50% by 2040, and over 50% by 2050, as set in the Philippine Energy Plan.