Brazil: ONS warns Aneel and Inmetro of rule conflict risk over solar panels

The largest solar power plant in Latin America is under construction in Pirapora, Minas Gerais, a project aimed at addressing Brazil’s lag in the solar industry. Credit: afp

The National System Operator (ONS) has warned of potential conflicts between regulations issued by two government agencies regarding solar panels: the National Electric Energy Agency (Aneel) and the National Institute of Metrology, Quality and Technology (Inmetro). The body responsible for overseeing electricity generation and distribution in Brazil expressed concern over a possible scenario of “legal, technical and regulatory uncertainty” for solar panels, which currently account for up to 45% of the power system and could increase the risk of blackouts.

The document, obtained by Estadão’s Coluna do Estadão, was signed on the 20th by Alexandre Nunes Zucarato, ONS’s Planning Director. “A piece of equipment (solar panel) could meet the requirements necessary for its commercialization in Brazil, but not the requirements demanded for its connection to the distribution grid, resulting in uncertainties for manufacturers, distributors and consumers,” the director stated.

When contacted, the ONS stated that it seeks to ensure the “safety and reliability” of the power system. The Aneel noted that its public consultation on the matter concludes on the 30th of next month. The Inmetro declared that it has taken into account the points raised by the ONS. The official statements from both agencies are available at the end of this report.

On one side, the Aneel is in the final phase of discussing the rules for the connection and operation of solar energy. The Inmetro, for its part, plans to review its standards only in 2027.

The two agencies regulate different stages of the solar energy generation process. While the Aneel defines the conditions under which solar panels can operate on distributor networks, the Inmetro sets technical requirements for the sale of these products.

Because the ONS does not directly control the generation from rooftop solar panels on homes and businesses, the curtailments fall on larger solar power plants that are part of the centralized system.

The power system must maintain a balance between energy generation and consumption to prevent blackouts. Last year, the country failed to utilize 20% of its solar and wind energy generation potential, primarily due to these interruptions.

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Read the ONS statement

Submitting technical input to industry regulators and agencies is a standard part of the operator’s institutional role, conducted routinely with a consistent focus on the safety and reliability of the Interconnected National System.

The submission to Inmetro underscores the need for the review of Ordinance No. 140/2022 to align with the update to Module 3 of the Electric Power Distribution Procedures for the National Electric System, which is currently under public consultation by Aneel. This coordination is particularly critical given the recent expansion of micro and mini distributed generation and the increasing share of inverter-based equipment in grid operations.

ONS also took part in the technical discussions that informed the development of the current Ordinance No. 140/2022. Institutional interaction at this stage is expected, as Aneel, with ONS support, is revising grid access requirements while Inmetro reviews equipment certification standards.

The aim is to foster alignment among the applicable requirements, thereby enhancing regulatory certainty for industry participants and facilitating the secure integration of distributed energy resources into the power grid.

Read the Aneel statement

At present, no established regulatory conflict exists between the agency’s standards and Inmetro’s rules concerning photovoltaic and energy storage equipment.

The document submitted by ONS highlights a potential future misalignment between the equipment compliance assessment requirements set by Inmetro and the technical requirements for the connection and operation of Distributed Energy Resources currently under discussion at Aneel.

Aneel’s Public Consultation No. 33/2026 is currently in the proposal review stage. The topics under analysis include monitoring, communication, protection, command response, and control of the power injected by resources connected to the grid. The public comment period for this consultation began on September 10, 2026, and will close on November 30, 2026.

The regulatory frameworks of Inmetro and Aneel operate within distinct and complementary scopes. While Inmetro establishes the compliance assessment requirements for equipment covered by its regulations, Aneel defines the requirements necessary for the safe connection and operation of these resources on distribution networks.

Aneel’s objective is for the modernization of the rules to safely incorporate the growing share of distributed generation and other distributed energy resources into the Brazilian power system.

Read the Inmetro statement

The Inmetro’s Compliance Assessment Directorate is currently reviewing the issues raised by ONS regarding the alignment between the revision of Inmetro Ordinance No. 140/2022 and the requirements proposed by ANEEL in Public Consultation No. 33/2026.

These inputs are under analysis by the Regulation and Regulatory Quality Division, within the framework of the working group established for this purpose. The review takes into account the regulatory and compliance assessment aspects involved, as well as the need for coordination with other agencies and stakeholders in the sector. Once this phase is completed, Inmetro may issue a formal position on the points raised, in accordance with the established regulatory procedures.

Finally, the revision of Ordinance No. 140/2022 is included in Inmetro’s Regulatory and Compliance Assessment Agenda for the 2026–2027 biennium, with processing scheduled for 2027. The process will consider relevant contributions and seek coherence between the requirements applicable to the equipment and those related to its grid connection, while respecting the institutional competencies of each agency.