Undergoing a profound transformation, Romania’s energy system is operating ever more often under critical conditions, in step with developments across Europe. Climate change and the evolving production–consumption mix heighten the risk of large-scale outages. From the Iberian Peninsula to the Balkans, incidents have multiplied, while Romania works steadily to strengthen its procedures and capabilities to avoid serious disruptions.
The new realities entail not only decarbonization — with the retirement of traditional generators that provided stability and inertia — but also the integration of a massive influx of unpredictable generation capacity: solar, wind and prosumers. At the same time, severe weather events are becoming more frequent and intense, while the diversification of trading regimes is adding new technical pressures. The most notable recent example is the blackout on the Iberian Peninsula, which left more than 40 million people in Spain, Portugal and southern France without power for over 10 hours. Romanian engineers followed this event closely, with some directly involved in the European task forces investigating its causes and extracting lessons for prevention and restoration
From routine outage to blackout
Romania’s power grid, like any other national system, faces incidents on a daily basis — from large conventional and renewable generators to prosumers and major consumers. Transelectrica operates around 10,000 kilometers of high-voltage lines, more than 80 substations and over 200 transformer stations. Beyond the transmission network, the operator also oversees the coordination of distribution systems, which together span hundreds of thousands of kilometers and include tens of thousands of substations. Every day, hundreds of thousands of automated responses and thousands of human decisions keep voltage and frequency in balance. In dispatching centers and in the field, thousands of engineers work continuously to ensure stability, by rerouting power flows and intervening promptly to correct faults.
Most outages are minor and pass almost unnoticed. But a failure at a large generator — or an unfortunate chain of faults and decisions — can trigger what experts call a blackout: a loss of supply across vast areas, affecting millions of consumers for extended periods.
Blackout: What it means technically vs. how it feels personally
According to ENTSO-E, the association of 40 transmission system operators from 36 European countries, a blackout is defined as an incident that results in the loss of more than half of consumption in a control area, or the complete absence of voltage for at least three minutes — both of which trigger system restoration plans. In Romania’s case, with a consumption of around 7,000 MW, the sudden disconnection of more than 3,500 MW would qualify as a blackout
For the public, technical criteria matter far less. A power outage of just a few minutes, even on a large scale, is perceived much like an ordinary fault: unpleasant, but not a crisis. The difference becomes tangible only when the outage stretches into hours or days, disrupting communications and other critical services. A telling example is the blackout experienced by the Republic of Moldova in November 2022. The separation of Ukraine’s grid from the European system, amid heavy bombardment of Ukraine’s transmission infrastructure, caused Moldova to lose almost 100% of demand and enter blackout automatically. Yet public perception was closer to that of a routine outage: in many localities the interruption lasted little more than an hour, and for citizens it felt little different from the blackouts they had already experienced in the past.
How restoration shapes the meaning of blackout
That is why restoration time is critical to how a blackout is experienced. With Romania’s support, the Republic of Moldova recovered very quickly. By contrast, Spain needed almost 24 hours to fully restore its much larger and more complex system, with crucial assistance from Morocco. One of the key lessons is the importance of autonomous generation capacity: plants such as the Aldeadávila hydropower facility in Salamanca played a decisive role in synchronizing and reviving the grid. For Spain, the incident also exposed the absence of backup thermal units available at critical moments and underscored how cross-border interconnections can make the difference between prolonged disruption and faster recovery.
Another lesson from the two cases concerns the duration of restoration. For consumers in the Republic of Moldova, the blackout was relatively minor, lasting under 60 minutes. In the Iberian Peninsula, however, the impact was much more severe. Even so, the first consumers were reconnected within an hour of the outage. Six hours later, about 35% of demand had been restored; after ten hours, more than 60% was back online. Sixteen hours after the breakdown, over 99% of consumers once again had access to grid electricity.
Transelectrica puts restoration readiness to the test
Over the past year, Transelectrica has conducted three major restoration drills, simulating real blackout recovery scenarios. On October 16, 2024, at Lotru, operators tested the independent start-up of the power plant, the supply of auxiliary equipment, and the resynchronization of the power island with the national grid. On April 8, 2025, at Porțile de Fier I, Romanian and Serbian teams started a generating unit with external feed from the Djerdap I hydropower plant, confirming the ability to use interconnections for black start. And on June 4, 2025, Transelectrica, together with Hidroelectrica and Bulgaria’s ESO-EAD, coordinated its most complex scenario so far: starting the Vidraru and Lotru plants without external supply, creating energy islands, and synchronizing them with each other and with the Bulgarian grid — validating both national procedures and cross-border cooperation.
Two further exercises are scheduled for this year, including one designed with greater public visibility. By involving journalists, Transelectrica aims to give the wider public a clearer picture of what network restoration entails and, in doing so, to reduce the risk of panic in the event of a real blackout.
Resilience begins with preparedness
A blackout is serious not only because it cuts off the power supply, but above all when it is accompanied by panic. Lack of information and uncoordinated reactions can magnify the technical impact and turn an outage into a social crisis. That is why it is essential to understand in advance that the risk of blackout can never be completely eliminated: even the most modern systems remain vulnerable to extreme weather, technical failures, human error, acts of war or cyber attacks.
People need to know that proven restoration procedures exist and that regular drills strengthen grid security. In a crisis, it is the preparedness of all stakeholders that makes the difference, as cooperation — from transmission operators and generators to large consumers, prosumers and the general public — is essential. A recent example illustrates this coordination: during the Easter period, authorities asked generators to adjust output to match very low consumption and prosumers to temporarily switch off inverters to avoid voltage and adequacy imbalances. The precautionary measure was understood and followed, helping the system adapt during the most sensitive hours of Sunday.
Such moments confirm that resilience is not only about infrastructure, but also about the coordinated behavior of the entire energy ecosystem. In a crisis, rapid and intelligent compliance by all actors — including consumers — can make the difference between a controlled outage and a crisis spiraling out of control.
These issues were extensively debated at the Technical Forum in the Energy Industry 2025, organized by the Association of Energy and Electrical Engineers (AIEE), where experts from companies, institutions and authorities examined both the technical challenges of restoring the power system and the role of public communication in crisis scenarios. Gabriel Avăcăriței, editor-in-chief of Energynomics, took part in the session dedicated to communication, emphasizing the importance of timely and accurate information for the population in the context of blackout risks