How the “solar cat” became a billion-dollar threat to the Brazilian electrical system and put ANEEL on high alert after the explosion of photovoltaic energy, clandestine frauds, and the growing risk of network collapse

Accelerated growth of solar energy in Brazil exposed regulatory failures, increased pressure on the national electric system, and led ANEEL to tighten rules against clandestine expansions of photovoltaic plants

The expansion of solar energy in Brazil has completely transformed the urban and rural landscape of the country in recent years. Today, finding photovoltaic panels on the roofs of homes, businesses, farms, and large plants is already part of Brazilian routine. The sector experienced a true energy gold rush, driven by regulatory incentives, reduction in technological costs, and a growing search for savings on electricity bills.

However, behind this historic advance, a silent problem began to worry authorities, specialists, and operators of the national electric system: the growth of so-called “solar thefts.”

According to information released by Canal Solar in an article published by Marina Meyer Falcão, with collaboration from Enio Fonseca, the increase in clandestine expansions in photovoltaic systems started to represent a technical, financial, and regulatory risk for the National Interconnected System (SIN). The situation led the National Electric Energy Agency (ANEEL) to open, in 2026, a public consultation to tighten rules and increase sector oversight.

The case marks a new phase of Brazilian solar energy, in which accelerated growth begins to encounter structural challenges that require regulatory maturation and greater operational control.

Brazil surpasses 60 GW in solar energy and changes national electric matrix

The growth of photovoltaic generation in Brazil impresses even international market specialists. The country reached the mark of 60 GW of installed capacity, consolidating itself as the second-largest source of the national electric matrix and representing about 24.5% of all Brazilian energy capacity.

Furthermore, Brazil already has more than 4 million solar photovoltaic systems installed in homes, companies, rural properties, and large plants.

Between 2021 and 2023, the leap was considered vertiginous. During this period, solar generation went from occupying a modest share in the electric sector to accounting for significant portions of the instantaneous energy consumed in the country.

The numbers reveal the speed of this transformation:

• 2023: production of 50,633 GWh;
• 2024: generation of 70,996 GWh;
• 2025 and 2026: annual production exceeding 80,000 GWh.

Another relevant data point shows that almost 58% of the energy produced in 2024 came from distributed micro and mini-generation (MMGD), a model where consumers also become energy producers.

The annual expansion of solar energy reached approximately 70%, drastically altering the operational profile of the National Interconnected System.

However, while the sector celebrated historical growth records, distortions began to emerge that now concern the government, distributors, and regulatory bodies.

What is the “solar cat” and why it concerns authorities

The so-called “solar cat” occurs when owners clandestinely expand their photovoltaic systems without authorization from the responsible distributor or without approval from the granting authority.

In practice, many consumers install more solar panels or replace inverters with more powerful equipment without officially reporting the increase in generation capacity.

Although some of these irregularities occur due to technical ignorance or inadequate guidance from installation companies, experts warn that many cases involve deliberate expansions aimed at maximizing financial gains.

The problem has ceased to be just an isolated contractual infraction and has become a systemic threat.

This is because the National Electric System Operator (ONS) depends on operational predictability to maintain the balance between energy generation and consumption in real-time. When thousands of systems operate above the approved capacity, the operator loses visibility over the actual load of the electrical grid.

In practice, the system starts operating “in the dark.”

Furthermore, the uncontrolled oversupply of energy at certain times has been exacerbating phenomena already known in the international electric sector.

The “Duck Curve” and the growing risk for the electric system

The disorderly advance of solar energy has brought to Brazil a phenomenon known worldwide as the “Duck Curve.”

The name refers to the graphic shape of energy demand throughout the day. During the period of highest solar incidence, especially around noon, there is an explosion in photovoltaic generation. This drastically reduces the need for other energy sources.

On the other hand, in the early evening, when residential consumption increases and the sun disappears, solar production plummets abruptly.

This imbalance forces the electric system to quickly activate thermal and hydroelectric plants to compensate for the sudden loss of generation.

The problem becomes even more severe when clandestine expansions make it difficult to monitor the actual load.

Besides the operational impact, there is also a huge financial cost.

According to estimates mentioned in the original article, the tariff incentives granted to micro and mini distributed generation have generated an estimated impact of R$ 16 billion, a value currently redistributed through the Energy Development Account (CDE).

In practice, consumers who do not have the financial means to install solar panels end up indirectly bearing part of these costs in their electricity bills.

Experts point out that the scenario creates a socially unequal cross-subsidy model, increasing the pressure for regulatory changes.

ANEEL tightens rules and launches Public Consultation No. 009/2026

In light of the increase in irregularities, ANEEL decided to significantly expand control over the sector.

As published by Canal Solar, the agency opened Public Consultation No. 009/2026, based on Technical Note No. 148/2025-STD and reported by director Gentil Nogueira de Sá Júnior.

The deadline for submitting contributions was set until June 6, 2026.

The proposal establishes profound changes in the oversight of distributed generation and is based on four main pillars.

The first strengthens the role of distributors as effective operators of distribution systems (DSOs), expanding their technological oversight capacity of the network.

The second point authorizes harsher penalties for clandestine expansions, including immediate suspension of supply and energy injection.

Furthermore, ANEEL intends to allow distributors to deny new connection requests in regions where the technical stability of the network is already compromised.

Another relevant aspect involves the revision of mechanisms for compensating energy surpluses, aiming to discourage over-offers during low-demand periods.

The measure represents one of the largest regulatory changes ever discussed in the Brazilian distributed generation sector.

Legislation already considers clandestine expansions as fraud

Although regulatory tightening is under discussion, the practice is already considered irregular by current Brazilian legislation.

The sector is mainly governed by Law No. 14,300/2022, known as the Legal Framework for Distributed Generation.

The legislation defined transition rules for charging the use of electrical infrastructure, especially related to the so-called “Fio B,” responsible for distribution costs.

Additionally, ANEEL Normative Resolution No. 1,000/2021 establishes that any alteration with an increase in power injected into the network requires prior authorization from the distributor.

Article 8 of the resolution makes it clear that expansions without approval constitute a contractual breach and tariff fraud.

In this context, experts state that the sustainable growth of solar energy will increasingly depend on regulatory compliance, technological traceability, and smart oversight.

Brazilian regions face different challenges in solar expansion

The impacts of photovoltaic expansion vary significantly between Brazilian regions.

In the Southeast, especially in São Paulo and Minas Gerais, there are major urban bottlenecks and the highest volume of fraud in residential and commercial systems.

The Northeast has the best solar irradiation indices in the country and hosts large centralized generation parks. The excess production in the region creates increasing pressure on the transmission lines responsible for connecting the Northeast to the rest of the SIN.

In the South, the problem mainly affects systems linked to agribusiness and rural cooperatives, where voltage fluctuations can compromise more sensitive networks.

Meanwhile, the Midwest has become a priority focus for oversight due to the rapid growth of mini-plants linked to the agricultural and industrial sectors.

In the North Region, despite the smaller national participation, solar energy plays a strategic role in replacing isolated diesel-powered systems in areas of the Amazon.

The future of solar energy in Brazil will depend on regulatory balance

Solar energy has established itself as one of the main structural transformations of the Brazilian electric sector in recent decades.

Besides partially democratizing access to energy generation, the technology has driven billion-dollar investments, job creation, and carbon emission reduction.

However, experts warn that the continuity of this growth will directly depend on the institutional capacity to balance technological innovation with systemic security.

The rise of so-called “solar thefts” has highlighted the limits of a model that grew faster than the State’s own regulatory capacity.

ANEEL, by reinforcing oversight, monitoring, and accountability, seeks precisely to prevent the sector from entering operational and financial collapse.

In this sense, the maturation of distributed generation will require greater regulatory predictability, strengthening of the energy compliance culture, and intensive use of regulatory intelligence.

After all, in a strategic sector like electricity, preserving the stability of the network and the public interest will continue to be an absolute priority.

According to energy market experts, Brazil still has enormous photovoltaic growth potential. However, the future of the national energy transition will increasingly depend on the ability to ensure balance between expansion, legal security, tariff justice, and operational reliability.

Original source: Canal Solar.
Reference: Article published by Marina Meyer Falcão, with collaboration from Enio Fonseca, about the regulatory impacts of the so-called “solar theft” in Brazil in 2026.