ERC, the energy regulator of the Philippines, has approved an application from the world’s largest solar-plus-battery project under construction to develop and own its own transmission network.

The MTerra Solar Project, under development by Terra Solar Philippines Inc. (TSPI), a wholly owned subsidiary of SP New Energy Corp, is a 3.5 GW solar and 4.5 GWh battery energy storage system (BESS) spread between the municipalities of Nueva Ecija and Bulacan on the island of Luzon. The project is being implemented in two phases, the first of which will consist of approximately 2.5 GW of solar alongside 3.3 MWh of BESS.

ERC’s approval, signed off last week, permits the project to connect to the Luzon grid via its own dedicated point-to-point transmission facilities that are being constructed by TSPI. The commission’s decision says the connection will be made through a bus-in connection to the existing 500 kV Nagsaag-San Jose transmission line, as well as through another bus-in connection to the planned San Isidro 500 kV substation.

However, it denies TSPI’s request to operate and maintain the transmission facilities, outlining that responsibility will remain with National Grid Corp. of the Philippines (NGCP), subject to applicable charges to TSPI.

The commission’s decision also outlines a potential delay in connection to the forthcoming San Isidro substation, as NGCP is yet to file approval for the project’s capital expenditure application. Based on the Philippines’ Transmission Development Plan, ERC expects the substation to be completed between 2031 and 2040.

According to an inspection of TSPI’s transmission facilities in September, ERC says construction of the subject facilities is ongoing and 90% completed. The commission’s decision determines the total costs of the facilities at PHP 14.2 billion ($244.4 million).

In July, a project update revealed that 54% of the first phase of works had been completed within eight months of construction, marking progress ahead of schedule. At the time, 778 MW of solar had been installed, making it already the largest solar installation in the Philippines.

The first phase, which also includes a 500 kV transmission line to the Nagsaag-San Jose connection, is due for completion in 2026.