Photovoltaic rooftops could supply over one third of Vitoria Gasteiz energy needs

Photovoltaic rooftops could supply over one third of Vitoria Gasteiz energy needs
by Hugo Ritmico
Madrid, Spain (SPX) Apr 30, 2025

In a new study by the University of the Basque Country (UPV/EHU), researchers found that rooftop solar installations in Vitoria-Gasteiz could supply up to 38% of the city's annual electricity consumption. The analysis highlights rooftop photovoltaic systems as a key renewable energy strategy for urban decarbonization, especially where land availability is limited.

The research assessed the energy potential of rooftops across the capital of Alava-Araba, concluding that half of the total rooftop area is viable for solar installations. "In contrast to large-scale photovoltaic projects in rural zones, we aimed to understand the capacity of already urbanized environments, avoiding further land use impacts," said lead researcher Alex Tro.

A major advance in this study is the deployment of a new high-precision methodology developed by Ekopol at UPV/EHU. This approach leverages open-source Geographic Information Systems (GIS) software to assess rooftop potential using detailed local data rather than generalized assumptions. The tool incorporates variables such as building orientation, shading, tilt, solar radiation, ambient temperatures, and the projected efficiency and lifespan of photovoltaic panels.

Unlike standard assessments focused solely on economic return, the study introduces an energy viability filter based on Energy Return on Investment (EROI). This ensures that only rooftops capable of generating more energy than is consumed during panel installation and operation are considered viable. "This innovative criterion allows us to exclude technically possible but energetically inefficient installations," Tro explained.

Findings also show that solar generation potential is significantly higher on the city's outskirts, where rooftops are less obstructed by surrounding buildings. Central areas, dense with tall structures, pose greater challenges due to shadowing and spatial limitations.

The methodology, which uses publicly accessible data, is designed to be easily replicated for urban energy planning in other cities. It calculates solar output potential down to each square meter of rooftop area, offering a practical planning tool for municipalities and energy agencies.

Tro emphasized that while rooftop photovoltaics offer meaningful contributions, they are not a standalone solution. "Even under ideal implementation scenarios, solar rooftops alone cannot satisfy current urban energy demands. Real progress will also require systemic changes, such as shifting consumption habits and embracing an eco-social transition," he said.

Research Report:A methodology for assessing rooftop solar photovoltaic potential using GIS open-source software and the EROI constraint