Starting in January of this year, those who had their solar energy system approved after January 7, 2023, will see a reduction in their electricity bill. This is because, since 2023, these consumers have stopped offsetting a progressively smaller portion of the energy generated by their photovoltaic systems.
Law 14.300/2022, which created the Legal Framework for Distributed Generation, established a tariff transition schedule that reduces, year by year, the compensation for the Fio B tariff component.
The percentage that consumers started being charged began at 15% in 2023, rose to 30% in 2024, reached 45% in 2025, and, as of January of this year, will be 60%. (See table below).
In practice, this means that only 40% of the B Wire will continue to be deducted from the electricity bill of those who have a solar energy system and whose photovoltaic system was approved after January 7, 2023, resulting in a higher cost for those who generate their own energy.
The financial impact on these users' bills varies depending on the distributor, since the cost of Fio B (a specific type of electricity connection) differs in each region. It's important to note that consumers whose photovoltaic systems were approved before January 7, 2023, are not affected by the Fio B transition rule.
But what is Wire B?
Fio B is a portion of the energy tariff used to pay for the operation of the electrical grid. It is part of the TUSD (Tariff for Use of the Distribution System), which is charged to all consumers who use the grid, whether or not they have solar energy.
In practice, Fio B is the amount that compensates energy distributors, such as CPFL, Enel, Cemig, and Copel, for the services they provide. This item does not appear separately on the electricity bill under the name "Fio B," but it is included in the total TUSD value.
The revenue collected from Fio B is allocated to the maintenance of the electrical grid infrastructure, including poles, wires, transformers, and substations.
These resources also compensate maintenance and service teams, the operation of control centers, as well as investments in the modernization and expansion of the network. Part of the amount is also used to remunerate investments made by the distributors themselves.
What will the new compensation for Fio B look like?
To illustrate, let's consider a distributed generation (DG) system installed in the concession area of CPFL Paulista, which had its connection budget issued after January 7, 2023. Let's assume that the photovoltaic system injects 1.000 kWh into the grid.
With the changes planned for 2026, 60% of the value of Fio B (equivalent to R$ 0,1239 per kWh) will no longer be compensated. Therefore, when offsetting these 1.000 kWh injected, the consumer will no longer receive a credit of R$123,90 due to the 60% of Fio B that is not compensable.
Uncertainty regarding the rules after the transition period.
Although Law 14.300 establishes the phasing out of non-compensation for Fio B until 2028, the scenario from 2029 onwards is still uncertain. The definitive regulation of the valuation of energy generated by distributed generation systems, that is, how this energy will be remunerated in the long term, has not yet been finalized by [the relevant authority/organization]. ANEEL (National Electric Energy Agency).
The expectation was that the methodology would be defined by July 2024, 18 months after the publication of the law, as per the legal deadline. However, this timeline was not met due to delays by the CNPE (National Council for Energy Policy) in publishing the guidelines that would guide the regulation.
The delay has direct impacts on consumers, investors, and companies in the solar energy sector, who do not know how the remuneration for energy injected into the grid will be calculated after 2029, when the compensation system will cease to apply to those who joined the distributed generation system from 2023 onwards.
The uncertainty directly affects project pricing, hindering economic feasibility analyses and discouraging new investments in distributed generation. As a belated response, the ANEEL The Public Consultation Process No. 23/2025 opened in early December 2025, an initial stage with no guarantee of a short-term outcome.
The process aims to gather international experiences and proposals on how to value the costs and benefits of distributed generation (DG), but the public consultation is expected to extend until March 2026, with no official timeline for the completion of the regulation.
Meanwhile, consumers continue to await structural definitions for the future of distributed generation in Brazil, while delays in the implementation of the law itself raise questions about regulatory governance and the institutions' commitment to legal certainty.
Discover the Advanced Course on Solar Power Plant Design up to 3MW
all the content of Canal Solar is protected by copyright law, and partial or total reproduction of this site in any medium is expressly prohibited. If you are interested in collaborating or reusing part of our material, please contact us by email: redacao@canalsolar.com.br.
Answers of 8
Dear,
I have always been radically against the generation of surplus energy, although I recognize that it is very difficult to obtain 100% simultainity between generation and consumption. With the advent of Grid Zero technology and, above all, with the drop in investment in battery storage, such injection becomes unfeasible. In the end, those who lose in the medium and long term are the concessionaires and distributors. Engineer, professor, master in science in electrical engineering, designer in solar generation, electric vehicle charging stations, energy efficiency and areas related to the academic training in electrical engineering.
I believe the power companies pushed for this tax, and as always in Brazil, we Brazilians will foot the bill. More taxes and terrible service.
In fact, the TUSD charge has existed for a long time, even before solar entered the scene. Even worse, I think, is the COSIP; this charge is incredibly unacceptable, it has no rules, they charge based on consumption, not to mention the tariff flags that should be excluded for those who invest in solar, and the hidden sector charges… the B wire charge came to cover up the other fees, people get lost… it's very complicated…
And with investment in networks, reverse flow should be banned up to 75 kWp, so that small producers are not harmed again…
In a way, I even agree with not compensating for part of wire B, as long as it's invested in the SMART GRID, etc., etc.
and with investment in networks, that reverse flow be banned up to 75 kWp
In the end, most will use a hybrid system, connected to the grid and batteries, giving the middle finger to the power companies. In the end, they'll regret not having this extra energy in their systems.
It keeps creating fees and difficulties for generation.
Those who make garbage don't pay anything, they just absorb it.
do not inject,
Let us, the solar and wind power generation companies, help the system; we've invested heavily in that.
Don't create more fees.