(MENAFN- The Rio Times) On Sunday, August 10, 2025, Brazil's grid hit an odd kind of danger. Father's Day kept many people at home, temperatures were low, and electricity demand sagged just as rooftop and small solar plants poured midday power into local lines.

Around 11 a.m., distributed solar alone supplied roughly 23 gigawatts while national demand hovered near 58 gigawatts.

Because the system operator cannot dial rooftop output up or down, it swiftly curtailed centrally dispatched plants-mainly wind and utility-scale solar-to keep frequency stable and avoid a blackout.

That single morning captures a larger structural problem. Brazil built a highly interconnected system designed to balance big hydro, thermal, wind, and utility-scale solar.

In recent years, however, most new solar has arrived on rooftops and small commercial sites that feed directly into distribution grids, beyond the operator's real-time control.



The result is plenty of electricity when the sun is high and demand is soft-and a steep“sunset ramp” when solar fades and evening demand surges, forcing thermal plants to start hours early.

The financial hit is real. Curtailment wastes clean energy and slices revenue from wind and solar projects, chilling fresh investment.

Industry groups say billions of reais have already been lost, and roughly R$30 billion ($5.66 billion) in solar and wind developments are on hold as investors wait for clearer rules.

Behind the story is a planning gap. Transmission expansion was historically tied to demand growth, not to the rapid rise of behind-the-meter generation.

Incentives under Brazil 's distributed-generation law helped households and businesses shield themselves from high power prices, but the grid did not gain matching tools to manage all that midday supply.

Authorities are now moving on several fronts: giving distribution companies real operator roles to manage local resources, adding grid-scale batteries and demand-response programs, accelerating transmission works, and updating market signals so electricity is most valuable when it is most useful-especially around sunset.

Why it matters beyond Brazil: Many countries are racing toward the same future. Without smarter coordination, they will waste cheap clean power at noon and pay more at night. With it, rooftop solar remains an asset-cutting bills, strengthening reliability, and speeding the energy transition.

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