Many professionals make mistakes when it comes to passing on the savings that their clients will have with the installation of the solar plant, especially after the change brought about by Law 14.300 / 2022. Therefore, you need to pay attention and adjust your calculations as we will show below.
Law 14.300/2022 determines that, in the year 2025, the compensation of the TUSD Fio B component increases from 30% to 45% for consumers who had photovoltaic systems approved (Connection Budget issued) by the concessionaire as of January 7, 2023.
As a result, as of January 1, 2025, these CUs (consumer units) will pay 45% of Fio B to offset the energy injected into the distribution grid. These projects are classified as GD II. This change is part of the staggered tariff transition that began in 2023, as established by Law 14.300:
Fio B tariff value
It is important to highlight that the compensation rules after this transition period, that is, from 2029 onwards, have not yet been defined by ANEEL. Many people use the value of the Fio B tariff as 28% of the total tariff to calculate DG (distributed generation) solar energy projects. However, this idea does not reflect reality.
It is important to emphasize that the value of Fio B varies according to each electricity concession area, being influenced by regional conditions and the number of consumers served in the concession area. And that this value of 28% represented an average of all concession areas at the time when changes to the distributed generation (DG) rules began to be discussed in mid-2019.
What will the new compensation for Fio B look like?
To understand the real impact of this change, the Canal Solar carried out an exclusive survey based on data from ANEEL (National Electric Energy Agency), analyzing how the new compensation for Wire B will be.
The table below considers the ten electricity distributors with the largest number of photovoltaic systems installed in Brazil. It is important to note that the taxes included in the electricity bill were not considered in the calculation.
This analysis details how the new TUSD Fio B compensation impacts consumer costs in each of these concession areas, highlighting regional particularities and variations in TUSD, Fio B and Energy Tariff (TE) rates.
| Concession area | Fair TUSD + TE (R$/kWh) |
Wire B (R$/kWh) | Wire B in the tariff | Non-compensable value 45% of Wire B (R$/kWh) | Non-compensable % of the B-strand of the tariff |
| Cemig-D | R$0,80 | R$0,25 | 30,96% | R$0,11 | 13,93% |
| RGE | R$0,72 | R$0,21 | 28,97% | R$0,09 | 13,04% |
| Copel-DIS | R$0,63 | R$0,15 | 24,30% | R$0,07 | 10,94% |
| CPFL Paulista | R$0,70 | R$0,19 | 26,77% | R$0,08 | 12,04% |
| Energisa MT | R$0,85 | R$0,30 | 35,50% | R$0,14 | 15,98% |
| Neoenergia Coelba | R$0,82 | R$0,32 | 39,25% | R$0,14 | 17,66% |
| Equatorial GO | R$0,75 | R$0,27 | 36,47% | R$0,12 | 16,41% |
| Neoenergia Elektro | R$0,71 | R$0,20 | 27,69% | R$0,09 | 12,46% |
| Energisa MS | R$0,87 | R$0,32 | 36,32% | R$0,14 | 16,34% |
| Equatorial PA | R$0,94 | R$0,39 | 41,51% | R$0,18 | 18,68% |
* Data extracted from ANEEL on 07/01/2025. The values presented do not consider taxes and were rounded to 2 decimal places. The concession areas were selected considering the number of consumer units with photovoltaic systems installed
To illustrate, let's consider a distributed generation (DG) system installed in the concession area of Equatorial-PA, which had its Connection Budget issued after January 7, 2023. Let's assume that the photovoltaic system injects 1.000 kWh into the grid. With the changes this year, 45% of the value of the B Wire (equivalent to R$ 0,18 per kWh) is no longer compensated.
Thus, instead of receiving a credit of R$ 0,94 for each kWh injected, the consumer will actually receive a reduced credit of R$ 0,76 per kWh injected into the grid, not considering taxes. In other words, their energy credits will be reduced by 18,68%. Therefore, by offsetting these 1.000 kWh injected, the consumer will forgo a credit of R$ 180,00 due to the 45% non-compensable portion of the B Wire.
Note that the weight of Fio B in the Equatorial-PA tariff is 41%, that is, much higher than the 28% commonly used, so it is worth doing the right calculation according to the conditions of the distributor where the project is being installed.
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Answers of 4
From what I understand in this table, in the case of Energisa MT, wire B represents 35,5%. It was calculated as 35,5% on (TUSD + TE), but wire B is part of the TUSD portion. Shouldn't the correct approach be to calculate 35,5% only on the TUSD and not on the TUSD + TE?
Hi, good afternoon. This article is very comprehensive.
But the link to download the spreadsheet isn't working. It just stays on the page and I can't find any download button.
Hi Thais, I suggest you access the most up-to-date article on the subject:https://canalsolar.com.br/consumidores-60-do-fio-b-2026/
The tax itself is unfair, but it still doesn’t make it impossible to install a photovoltaic system. It will just take longer for the system to “pay for itself.”