Grid collapse in Indonesia poses threat to renewables expansion

Plans to integrate tens of gigawatts of solar energy in Indonesia are bound to fail if the national transmission framework is not designed to withstand increasingly severe climate conditions, the Jakarta-based think tank Institute for Essential Services Reform (IESR) has said.

The province of North Sumatra in northwestern Indonesia has faced two major power disruptions within a month, including the collapse of a total 12 transmission towers.

On June 4, the 275 kV Galang–Simangkuk EHV transmission line, operational only since 2019, suffered structural failure, with three towers collapsing and two others suffering deformation. The incident followed issues on the 150 kV Tebing Tinggi–Sei Rotan HV transmission line earlier the same day, including six towers collapsing and one tower bending.

The events, which coincided with heavy rainfall and strong winds in the area, caused major disturbances to the regional power system and widespread outages that were not fully rectified until the next day. Prior to the incidents in June, eight provinces across Sumatra island also experienced power outages on May 22, with full systems restoration not reached until May 24.

While severe weather has been reported as the initial trigger in each instance, IESR CEO Fabby Tumiwa believes that using weather as the sole explanation is far from sufficient to account for the structural damage experienced on such a massive scale.

“Transmission towers are designed to withstand heavy rain, lightning, and strong winds that are common in Indonesia. A number of international standards are applied to transmission infrastructure,” Tumiwa said, “Therefore, the primary cause of this incident should not immediately be attributed solely to bad weather. The key question is why relatively new infrastructure experienced cascading failures under such weather conditions.”

IESR says the power disruptions also provide empirical evidence that grid resilience can no longer be treated as secondary to power generation development, particularly as Indonesia plans to ramp up its integration of renewable energy into the electricity system.

The country first unveiled plans to deploy 100 GW of solar, comprising 80 GW of off-grid and 20 GW of grid-connected solar, last year. In March, IESR released a report covering the work required to make the target a reality. The thinktank’s latest analysis says that without a transmission network designed to withstand increasingly unpredictable climate conditions, such targets will lose their most fundamental foundation.

IESR is calling on the government of Indonesia to conduct a technical review on the incidents to determine whether design flaws, material degradation or construction weaknesses contributed to the failure, as well as a national audit of the transmission network.

It also recommends a national grid resilience strategy is established and an investigation is launched into why the system failed to respond to local disturbances before they escalated into a regional crisis.

“In modern power systems, lightning, heavy rainfall, and strong winds are not extraordinary conditions. They are disturbance variables that must be incorporated from the outset into planning blueprints. The critical question is no longer why severe weather occurs, but why our transmission system is so fragile and unable to withstand such disturbances,” Tumiwa added.

“A thorough investigation must go beyond surface-level explanations and address the underlying technical issues, institutional shortcomings, and investment commitments that have left our electricity system vulnerable.”

Indonesia surpassed 1 GW of solar capacity in 2025, with total capacity reaching 1.49 GW.