The ONS (National Electric System Operator) presented a favorable assessment of the management of the SIN (National Interconnected System) throughout 2025, evaluating that the year was marked by the maintenance of supply security even in a context of profound transformations in the electricity sector.
According to a note distributed to the press this Monday (29), the coordinated operation of generation and transmission allowed the load to be met continuously, despite relevant climatic events, changes in consumption patterns and accelerated growth of variable renewable sources.
The Director-General of ONS, Marcio Rea, stated in 2025 that there had been progress in projects that reinforced ONS's commitment "to an increasingly modern operation, attuned to the evolutions and transformations that the electricity sector is undergoing in Brazil and the world."
Throughout the year, the Brazilian electrical system operated under challenging conditions, combining periods of heightened hydrological stress, episodes of intense rainfall, and significant variations in solar and wind power generation, according to a statement from the ONS (National System Operator).
Nevertheless, the Operator believes that the planning, real-time monitoring, and operational response actions were sufficient to preserve the system's reliability and prevent more impactful failures.
The report also highlights that the increasing complexity of the National Interconnected System (SIN) demands ever more integrated action between agents, operation centers, and sectorial bodies. In this scenario, the operator reinforces that anticipating scenarios and making preventive decisions were crucial for the results achieved in 2025.
Integration of renewables
Without mentioning the curtailment issue, which has caused billions in losses to renewable energy generation agents, one of the central points of the report presented by the ONS (National System Operator) was the integration – considered by the operator as "safe" – of these sources, especially solar and wind, whose share continued to grow throughout the year.
The ONS (National System Operator) merely stated that the system managed to absorb high volumes of variable generation without compromising stability, thanks to the coordinated use of hydroelectric plants, which "continue to play a fundamental role in modulating supply."
Hydropower plants were highlighted as a key element in compensating for the intermittency of renewables, allowing for rapid adjustments in generation according to fluctuations in wind and solar radiation. Furthermore, the ONS (National System Operator) pointed to advancements in operational procedures and the use of forecasting tools, which contributed to more precise and reliable decisions.
The report also mentions the response to extreme events, such as storms and sudden load variations, which required rapid responses to restore the system. According to the operator, the accumulated experience and continuous improvement of operating protocols helped reduce risks and maintain service to consumers.
Another point was the coordination with transmission agents, considered essential for managing a system of continental dimensions. The ONS (National System Operator) emphasized, but without addressing the current bottlenecks of the SIN (National Interconnected System), that the reliability of the transmission network was crucial for the system's good performance, allowing for the flow of generation and service to different regions of the country.
Next Steps
Despite the positive assessment, the ONS (National System Operator) acknowledges that challenges are likely to intensify in the coming years. The expectation is for continued growth in renewable energy sources, changes in consumption patterns, and greater exposure to extreme weather events, factors that will demand even more flexibility and responsiveness from the electrical system.
The operator points out that strengthening medium- and long-term planning will be fundamental to addressing these challenges, as will advancing solutions that increase the system's flexibility. Among the topics gaining relevance are improving forecasting models, demand response, and evolving operational mechanisms to handle scenarios of excess generation during certain periods.
According to the ONS (National System Operator), the 2025 results demonstrate that the SIN (National Interconnected System) has a solid foundation, but also highlight the need for constant evolution. The assessment reinforces the view that the ongoing energy transition imposes new challenges on the system's operation, requiring continuous investments in technology, training, and institutional coordination.
Upon completing the assessment, the operator evaluates that the experience of 2025 serves as a benchmark for future cycles, indicating that security of supply will increasingly depend on efficient integration between sources, robust transmission, and the ability to anticipate and manage risks in an increasingly complex electrical system.
Other key points for 2025 mentioned in the ONS report:
- Completion of the Manaus-Boa Vista (RR) Interconnection;
- Announcement of the results of the Added Value project, with estimated savings of R$ 12,6 billion;
- Launch of the ONS Award for Quality in Operation;
- Results of the Energy Operation Plan (PEN 2025), horizon 2025-2029;
- Results of the Medium-Term Electrical Operation Plan for the National Interconnected System (PAR/PEL 2025);
- Establishment of the Emergency Plan for Managing Surplus Energy in the Distribution Network approved by ANEEL.
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