Energy Development Corporation (EDC) is planning to invest up to PHP 100 billion to expand and upgrade its Tongonan Geothermal Project (TGP) in Leyte, a move that could significantly increase geothermal power output in the Visayas.

In a filing with the Department of Environment and Natural Resources (DENR), EDC proposed modifications that would raise TGP’s total rated capacity to 967.224 megawatts (MW) from its current 637.21 MW. The project is one of the country’s largest geothermal complexes and a key power source for the Visayas grid.

EDC said the planned upgrades are intended to ensure long-term power production while improving efficiency. “The planned modifications at the TGP will secure long-term production, sustain supply to the Visayas grid, and improve efficiency by generating more power from the same steam resource,” the company said.

A major component of the proposal is the decommissioning of the existing Upper Mahiao Power Plant, which has been operating for nearly 30 years. EDC plans to replace it with a new facility with a capacity of 450 MW, more than three times the output of the current 136.5-MW plant.

The company is also seeking to upgrade the 180-MW Mahanagdong Power Plant through the installation of modular binary units, a technology designed to extract additional energy from geothermal fluids without expanding the plant’s footprint.

To support the higher output, EDC plans to drill 172 additional geothermal wells within the existing project area and upgrade current well pads. The company said these improvements are aimed at enhancing safety and reliability while minimizing the need for additional land use.

EDC is likewise proposing to expand its existing 10-MW battery energy storage system (BESS) in Tongonan to 30 MW, which would help stabilize electricity supply by storing excess power and releasing it when needed. It also plans to begin drilling activities at Alto Peak, which could contribute steam equivalent to around 30 MW of additional generating capacity.

According to the Environmental Management Bureau (EMB), the proposed project modifications are now undergoing the environmental impact assessment process, starting with a series of public scoping activities in Leyte. These sessions are intended to present the project to stakeholders and gather concerns and inputs that will define the scope of the project’s Environmental Impact Statement.

EDC said construction and commissioning of the new and upgraded facilities are expected to begin this year, with all proposed modifications targeted to be operational by 2029.

EDC is the renewable energy subsidiary of First Gen Corp. and currently has a total installed capacity of 1,480.19 MW, accounting for about 20% of the Philippines’ total renewable energy capacity.

As major geothermal upgrades move into the environmental review stage, how should policymakers and local communities weigh the benefits of long-term clean power supply against the potential impacts on host areas?

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