ANEEL approves new rules for curtailment and establishes sharing of generation cuts between renewable sources

On October 6, 2026, the Collegiate Board of Directors of the National Electric Energy Agency (ANEEL) approved, within the scope of Public Consultation No. 45/2019, the new regulation applicable to the reduction or limitation of electricity generation, known as curtailment. The decision resulted in the issuance of ANEEL Normative Resolution No. 1,170/2026, published on October 9, 2026, and ended a regulatory discussion process that began seven years earlier.

The measure seeks to improve the operational criteria and the distribution of the impacts resulting from the generation cuts determined by the National Electric System Operator (ONS), especially in view of the expansion of renewable sources and the increase in episodes of energy oversupply in the SIN.

Among the main changes, the adoption of a new methodology for sharing generation cuts for energy reasons, until then separately between wind and solar plants, stands out. With the new regulation, the apportionment will cover these sources and hydroelectric plants without storage capacity that have turbinable spilled energy (EVT).

The implementation of this hydroelectric participation will occur gradually, with the application of factors of 25%, 50%, 75% and 100% on the respective potential generation references, in successive annual cycles. The first cycle will begin after the 18-month period foreseen for the definitive implementation of the regulation.

The rule also establishes a preferential order for cuts motivated by energy reasons, organized into three generation blocks. The first mainly includes thermoelectric plants whose reduction provides cost relief to the consumer. The second includes hydroelectric plants with reservoirs, certain thermoelectric plants and renewable sources subject to sharing the cuts. The third covers hypotheses in which the reduction in generation may increase the System Service Charges (ESS), in addition to certain modalities of energy importation.

In relation to cuts due to external unavailability or the need to meet electrical reliability requirements, the regulation preserves the ONS’s performance based on the effectiveness of the reductions to solve the identified restrictions. In the post-operation stage, however, it provides for the calculation of the amounts reduced by the ONS and their sharing among the eligible agents. The apportionment will observe sensitivity criteria and potential generation references, for accounting purposes by the Electric Energy Trading Chamber (CCEE).

Another relevant point concerns the self-production of electricity, including by equivalence. In these cases, when generation and consumption are located at the same connection point, the cuts for energy reasons should, as a rule, be limited to the portion of generation surplus to local consumption, in order to preserve the service of the industrial process. Exceptionally, for reasons of SIN security, the ONS may determine additional reductions, observing objective and transparent criteria provided for in the Network Procedures.

The implementation of the new regulation will occur in a staggered manner. After 90 days from the publication of the resolution, a transitional apportionment regime will begin, with financial effects, still without the grouping of wind, solar and hydraulic sources. Within 180 days of publication, a shadow operation phase should be initiated, of an informative nature, aimed at simulating the results of the new methodology. The full application of the model is expected to occur 18 months after publication.

During the shadow operation, alternative apportionment methodologies will also be evaluated. Among them are the treatment of the portion of hydroelectric generation necessary for the multiple uses of water resources and environmental restrictions and a differentiated model for wind and solar plants committed to reserve energy contracts. Any adoption of the alternative methodology related to hydroelectric restrictions will depend on a new public consultation and deliberation by ANEEL.

The regulation also provides for transparency and inspection mechanisms, including the disclosure of monthly reports by the ONS and the CCEE, the public availability of the calculation data and the performance of an independent audit. The ONS and the CCEE must submit proposals for the adequacy of their respective operational and marketing procedures within 90 days of the publication of the resolution.

The new rules change the distribution of risks associated with curtailment, especially for wind, solar and hydroelectric projects covered by the methodology. Its application may influence energy accounting, the exposure of agents to the short-term market and the structuring of contracts and new investments in generation.

Although the regulation seeks to provide greater predictability and balance to the management of generation cuts, it will be necessary to monitor their effects on the different agents, especially in the application of eligibility criteria and potential generation references and in the distribution of reduced amounts of energy.

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