Indonesia must learn from the 2025 Iberian blackout

On 28 April 2025, the Iberian Peninsula was hit by the largest blackout Europe had seen in more than two decades. More than 55 million people in Spain and Portugal lost power. Airports and metro systems ground to a halt, while hospitals switched to emergency generators. 

The incident has important lessons for Indonesia, where recent blackouts have exposed the fragility of the country's grid. As renewable energy generation increases, Indonesia now has an opportunity to update electricity grid rules before a similar crisis occurs. 

The calm before the blackout 

Some media outlets drove the narrative that too much solar and wind destabilised Spain’s grid. That narrative is misleading. The evidence to contradict it has been available since the beginning of the investigation into the blackout. 

The European Network of Transmission System Operators for Electricity’s (ENTSO-E) preliminary report into the blackout, published in October 2025, is clear. The climate conditions on 28 April were typical for the time of year. Solar and wind output was aligned with previous days and comparable April dates. Electricity demand was at a normal level.  

The hypothesis that excess renewable generation caused the blackout can be discarded. Generation technologies, whether thermal, renewable or nuclear, do not bear responsibility. 

Voltage disturbance increased from 9:00AM. By 10:30AM, significant voltage excursions were recorded across Spain's main 400 kilovolt substations. Two oscillation events between 12:03PM and 12:22PM were detected and mitigated. By 12:30PM, the system appeared calm. It was not. 

ENTSO-E's final report, published in March 2026, introduces a key operational concept: Any indication that the grid is in a weakened state should create urgency to act before the next incident. Spain's grid showed warning signs for 3.5 hours before the collapse. Voltage instability that builds slowly is more dangerous than a sudden spike, because it can go unaddressed until it is too late. 

At 12:32:57PM, generation began tripping in southern Spain. By 12:33PM, 2.5 gigawatts (GW) of combined renewable and thermal power generation disconnected. The voltage surged from 400 kilovolts to 435 kilovolts, breaching maximum permissible limits. The frequency collapsed from 50 hertz to 47 hertz, a deviation 300 times greater than the design tolerance.  

Within 24 seconds, the Iberian Peninsula had fully desynchronised from the continental European power system. Neither ENTSO-E report explains why 2.5GW disconnected. That remains the single largest unresolved question in the investigation. 

A failure of response, not generation 

The transmission system operator’s (TSO) job is to ensure production meets load and to activate reserves when balance is threatened. 

Spain’s shunt reactors — equipment that absorbs excess reactive power and suppresses voltage rises — were not activated in time. Spain's grid operator, Red Eléctrica (REE), also had two frequency reserve mechanisms. Frequency containment reserve (FCR) must activate within 30 seconds of a frequency deviation. Frequency restoration reserve (FRR) must restore frequency to 50 hertz within 15 minutes.  

REE did not activate manual FRR until 12:06AM on 29 April, roughly 11.5 hours after the blackout. Grid restoration was completed in Portugal at 12:22AM and in Spain at 4:00AM, nearly 16 hours after the initial event. 

Had REE dispatched 1.5–2GW of generation within 30 seconds at 12:32PM, it could probably have avoided the subsequent event that led to the full blackout.  

Whether this was a failure to activate reserves in time, to size frequency reserves adequately or to detect the frequency deviation early enough remains unclear. IEEFA has recommended that ENTSO-E and TSOs, under the supervision of the EU Agency for the Cooperation of Energy Regulators, conduct an in-depth review of reserve sizing and responsiveness across Europe, not just Spain. 

ENTSO-E’s final report identified 15 factors that contributed to the blackout. These included voltage control failures, poorly calibrated equipment protection settings and insufficient reserve responsiveness. The share of renewable energy does not feature among them. REE’s public position, that no breach attributable to REE caused the outage, is difficult to reconcile with these findings. The Spanish government's independent committee reached broadly the same conclusions as ENTSO-E. 

Solar photovoltaic (PV) systems can actively support voltage. Modern inverters can absorb or inject reactive power in real time. The problem in Spain was that grid codes had not kept pace with the rapid expansion of solar. That is a governance failure, not a technology failure. 

The European Commission estimates that the EU transmission network will require €477 billion in investment by 2040. Italy's Terna became the first grid operator to issue bonds under the European Green Bond Standard in July 2025: a €750 million transaction nearly five times oversubscribed. European TSOs hold investment-grade ratings. Clearly, financing is not a constraint to grid investment; the constraint is regulatory ambition. 

What this means for Indonesia 

Solar supplies less than 1% of annual electricity generation on Java and Bali. In Spain, IEEFA estimates that solar was supplying roughly 20–25% of generation when the blackout happened. That gap gives Indonesia time to build the grid in step with renewables deployment, rather than scrambling to catch up.  

State-owned utility PT Perusahaan Listrik Negara (PLN) targets 7,321MW of new solar in Central Java alone under the accelerated scenario of its 2025–2034 Electricity Supply Business Plan (RUPTL).  

Indonesia had 853MW of rooftop solar capacity as of 2025, far below regional peers Vietnam (6.9GW), Thailand (3.6GW) and Malaysia (1.8GW). Java, Madura and Bali account for 1.85GW of the 2GW of rooftop solar that Indonesia aims to install by 2030. The binding constraint for Indonesia is financing for rooftop solar: Payback periods of 7–12 years are too long to drive unsubsidised adoption.  

Indonesia requires new grid-connected rooftop solar installations to be paired with smart meters. The smart metering rollout is an opportunity to provide PLN with real-time operational data on distributed solar, closing a PV visibility gap that ENTSO-E has identified as unresolved in Europe. 

PLN's RUPTL 2025–2034 allocates approximately USD24 billion to transmission expansion and upgrades over the decade, requiring an average annual investment of USD2.4 billion. PLN’s transmission investment has averaged only USD1.4 billion per year since 2019, revealing a financing gap that budget increases alone will not close.  

Planning for the integration of renewables and energy storage should be a core design objective of PLN’s transmission investment programme. The governance framework that should accompany the grid build-out is clear. Grid codes should require new solar connections to provide active voltage support, not just generate. Battery storage should be a condition of utility-scale solar approval from the outset, with a minimum storage-to-solar ratio embedded in PLN's interconnection requirements. Together, these requirements would put Indonesia's transmission network ahead of the governance failures that the Iberian blackout exposed. 

Global battery energy storage system costs have fallen sharply alongside solar, making both together the most economically rational choice. Alongside storage, Indonesia should consider demand-side management — adjusting load in response to frequency signals — as a grid balancing tool.  

PLN should review frequency reserves against the future power generation mix, not today's coal-dominated one. Grid codes should be subject to a regular, mandatory review cycle, not updated only when incidents force change. 

The 2025 Iberian blackout was a governance failure. Three independent investigations have confirmed it was not caused by the share of renewable energy in the system. Spain updated its grid codes after the blackout, triggering €17 billion in planned grid investments for 2025–2030. 

Indonesia has the chance to update Java's grid codes before any comparable event, not in response to a crisis, but as a deliberate choice that accompanies one of the most significant infrastructure build-outs in the country's energy history. The Iberian blackout is not a warning against solar. It is a warning about the rules that govern it.

Read this commentary summary in Bahasa Indonesia.