The green flag has become a rarity
À medida que o El Niño aquece as águas do Pacífico e comprime as chuvas sobre o Norte e Nordeste do Brasil, o sistema elétrico nacional enfrenta uma temporada de seca que pode elevar as contas de energia de milhões de lares. O que em 2023 foi um ano inteiro de bandeira verde — sem sobretaxa — tornou-se, em 2026, uma memória distante: a bandeira amarela já foi acionada em maio, e o setor projeta períodos prolongados de bandeira vermelha ao longo da estação seca. É a tensão antiga entre clima e infraestrutura, agora agravada pela imprevisibilidade crescente dos padrões atmosféricos.
- O El Niño está suprimindo as chuvas nas regiões que alimentam as hidrelétricas brasileiras, pressionando reservatórios já abaixo do conforto operacional.
- O subsistema Sul opera a apenas 46,40% da capacidade, enquanto o Sudeste e Centro-Oeste chegam a 65,62% — margens estreitas para enfrentar seis meses de seca.
- A bandeira tarifária passou de verde para amarela em maio, sinalizando que o período de energia sem sobretaxa chegou ao fim mais cedo do que em anos anteriores.
- O setor elétrico projeta acionamentos frequentes da bandeira vermelha ao longo de 2026, revertendo o alívio tarifário que marcou 2023.
- Para as famílias de menor renda, que comprometem parcela maior do orçamento com energia, o impacto será desproporcional e sem mecanismo de amortecimento previsto.
O sistema elétrico brasileiro entra em uma temporada delicada. Com o fim das chuvas de abril e o início dos meses secos, os operadores de energia já se preparam para um período em que as contas de luz devem subir com mais frequência e intensidade do que em 2025.
O responsável é o El Niño, padrão climático que aquece o Oceano Pacífico e reduz as precipitações sobre o Norte e Nordeste do Brasil — justamente as regiões que abastecem as hidrelétricas do país. Com menos chuva, os reservatórios baixam, as turbinas giram menos e o sistema precisa recorrer a fontes de geração mais caras. Esse custo extra chega ao consumidor na forma de bandeiras tarifárias.
Os números são reveladores. O subsistema Sudeste e Centro-Oeste opera a 65,62% da capacidade; o Sul, a apenas 46,40%. São margens apertadas para atravessar uma seca de seis meses. O Norte e o Nordeste têm reservatórios mais cheios, mas são exatamente as regiões mais vulneráveis à supressão de chuvas provocada pelo El Niño.
A Agência Nacional de Energia Elétrica já deu o primeiro sinal: após meses de bandeira verde em 2026, acionou a bandeira amarela para maio. A trajetória é clara — em 2025, a bandeira vermelha mais severa vigorou por apenas um mês; agora, o setor se prepara para acionamentos muito mais frequentes ao longo do ano.
Para milhões de brasileiros, especialmente os de menor renda, isso significa que a energia elétrica vai consumir uma fatia maior do orçamento mensal. As bandeiras tarifárias refletem o custo real da geração — e quando o sistema está sob pressão, esse custo sobe sem filtro.
Brazil's electricity system is entering a precarious season. As April's rains ended and the dry months began, the country's power operators started preparing for what could be a costly stretch ahead—one where households and businesses will likely see their energy bills climb more often and higher than they did last year.
The culprit is El Niño, the Pacific weather pattern that warms ocean waters and disrupts rainfall across the tropics. In Brazil's case, it means less rain falling over the North and Northeast regions, which feed the hydroelectric dams that supply much of the nation's electricity. Fewer rains mean lower reservoir levels, which means less water to turn turbines, which means the grid has to buy expensive backup power. That cost gets passed to consumers through tariff increases.
The numbers tell the story. The Southeast and Center-West subsystem—home to São Paulo and much of Brazil's industrial base—is operating at 65.62 percent of capacity. The South, which includes Rio Grande do Sul and Santa Catarina, sits at just 46.40 percent. These are not comfortable margins heading into a six-month dry season. The North and Northeast reservoirs are fuller, but they're the regions most vulnerable to El Niño's rainfall suppression, so that advantage could evaporate quickly.
The National Electric System Operator and the National Electric Energy Agency have already begun signaling the shift. Through the first months of 2026, consumers paid nothing extra—the tariff flag stayed green, meaning no surcharge. But in late April, the agency switched to a yellow flag for May, adding a modest charge to every kilowatt-hour consumed. It was a warning. The green flag, which dominated all of 2023, has become a rarity.
The trajectory is unmistakable. In 2025, the most severe red flag—the highest tariff tier—was activated for just one month. The sector is now bracing for red flags to appear far more frequently this year. The pressure is structural, not temporary. Hydroelectric systems that once seemed robust are now operating closer to their limits, and climate patterns are becoming less predictable.
For millions of Brazilian households, especially those with tight budgets, this means energy costs will consume a larger share of monthly income. The poorest families, who spend a higher percentage of earnings on utilities, will feel it most acutely. There is no mechanism to soften the blow—the tariff flags are designed to reflect the actual cost of generation, and when the grid is stressed, that cost rises.
Notable Quotes
The sector projects sustained pressure on tariffs through the 2026 dry season, reversing the full-year green flag conditions of 2023— National Electric System Operator and sector analysts
The Hearth Conversation Another angle on the story
Why does El Niño specifically threaten Brazil's power system more than other countries?
Because Brazil depends on hydroelectric dams for the majority of its electricity. When El Niño suppresses rainfall in the North and Northeast, the reservoirs that feed those dams drop. Other countries with diverse energy sources—coal, gas, nuclear—can adjust. Brazil's grid is hostage to water.
The Southeast is at 65 percent capacity. That sounds okay. Why is that a problem?
It's not okay for a dry season. That 65 percent needs to last six months without significant rainfall. If El Niño hits as expected, it could drop another 10 or 15 percent. Then you're in crisis territory, buying expensive emergency power.
So the yellow flag in May is just the beginning?
Yes. It's the system saying the easy days are over. Yellow means costs are rising. Red means they're rising sharply. The sector expects red to become routine, not exceptional.
Who decided that consumers should bear this cost directly through tariff flags?
The tariff flag system was designed to reflect real generation costs. When the grid is stressed, power is expensive to produce. The theory is that passing that cost through encourages conservation. But it also means poor families pay more when nature doesn't cooperate.
Could this have been prevented?
Not this year—the rain already fell or didn't. But over decades, Brazil could have diversified its energy sources, invested in wind and solar, or built more storage. Instead, the system remained dependent on hydro. Now the bill is coming due.