By Brazil Stock Guide – Brazil discarded about 20% of the renewable energy it could have generated in 2025, according to a technical assessment of the country’s power system that highlights structural constraints amid rapid expansion of solar and wind capacity.
The findings are detailed in the Annual Curtailment Balance 2025, a report published by energy analytics consultancy Volt Robotics. The study shows that Brazil’s interconnected power system operated close to its lower safety limit on 16 days last year due to excess electricity supply — compared with just one such day in 2024.
Curtailment, the forced reduction of power generation despite available resources, affected mainly solar and wind plants. Average curtailed generation reached 4,021 megawatts over the year, representing energy that could not be absorbed by the grid.
Record curtailment concentrated in late 2025
The report indicates that curtailment intensified sharply in 2025, with August, September and October recording the highest monthly volumes ever observed. In several episodes, Brazil discarded in a few weeks an amount of renewable electricity comparable to the monthly output of large hydroelectric plants.
Volt Robotics classifies curtailment into three categories. Energy-based curtailment occurs when supply exceeds demand. Electrical curtailment is linked to transmission constraints, including maintenance or failures. Reliability-based curtailment is imposed to prevent system instability, even when transmission infrastructure is technically available.
Grid risks driven by excess supply
One of the most significant findings is the increase in critical operating days. In 2025, 16 days saw curtailment exceeding 80% of reference generation, a threshold that signals operation near the system’s safety floor. In 2024, that condition was met only once.
According to the report, the rapid growth of renewable generation — particularly solar — outpaced the system’s ability to adapt. This led Brazil’s National Grid Operator to implement an emergency operating plan with institutional backing from the electricity regulator, including provisions to curtail generation at small plants connected to distribution networks.
Sundays emerge as stress point
The analysis shows that many critical events occurred on Sunday mornings, when electricity demand drops as commercial and industrial activity slows. At the same time, solar output remains high and is often reinforced by favorable wind conditions.
This combination resulted in surplus power, stressed network limits and repeated forced cuts. Sundays effectively became a recurring stress test for the Brazilian power system in 2025.
Operational measures limited year-end risks
Curtailment risks typically increase at the end of the year, when demand falls during holidays and collective vacations. In 2025, however, operational decisions helped prevent a more severe outcome.
On Christmas Day, Thursday (25), thermal generation dispatch averaged 6.7 gigawatts, declining to 6.3 gigawatts on Thursday (1) in early January 2026. By contrast, on Sunday (26) of October — one of the 16 critical days — thermal dispatch reached 11 gigawatts, contributing to heightened system stress.
Economic impact estimated at R$6.5 billion
Beyond operational challenges, the report estimates that renewable curtailment caused economic losses of R$6.5 billion in 2025. Regulated contracts suffered revenue losses and penalties, while generators operating in Brazil’s free power market were exposed to price volatility and had to purchase electricity to meet contractual obligations.
Volt Robotics concludes that curtailment has become a recurring feature rather than an isolated event, underscoring structural limitations in a system originally designed for scarcity rather than surplus renewable generation.
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