How to calculate Wire B on the energy bill according to Law 14.300?

Updated October 8, 2025

If you want to understand how to calculate the "Fio B" (B-Financial Charge) on your energy bill, this guide is for you. Law 14.300, which regulates DG (distributed generation) in Brazil, establishes a progressive charge for energy injected into the grid. In this article, you'll learn:

• What is Wire B?

• How does this pricing affect the consumer?

• Practical examples to calculate the real impact on your electricity bill.

On January 7, 2022, the President Jair Bolsonaro sanctioned Bill 5829/2020, giving rise to Law 14.300, which regulates distributed generation in the country. On the one hand, entities celebrated the project's approval, on the other, integrators lamented.

The fact is that many simply do not understand how to calculate the impact of Fio B on energy bills, which is essential to effectively understand the concepts and how these calculations are carried out, so that they can actually position themselves and instruct their customers. .

Law 14.300 does not only deal with Fio B, but deals with conditions for future tariffs and also other matters, covering not only photovoltaic solar energy, but also incorporating other forms of energy generation interconnected to the SIN (National Interconnected System).

However, effectively understanding what Fio B is and its concepts is a great step forward for the entrepreneur. solar energy industry who wants to be engaged with the future of the segment.

To understand what the much talked about pricing of Wire B is about, it is necessary to initially understand what Wire B is. It is worth highlighting that the deduction of Wire B only impacts the amount of energy exported to the concessionaire's electrical grid, not impacts the energy generated and consumed instantly in the consumer unit.

Therefore, it is undoubtedly necessary to understand the concept of simultaneity, which determines the amount that will not be compensated, and consequently, how viable a project connected to the distributor's network will be.

What is Wire B?

To understand what Wire B is, we need to understand everything that makes up an end customer's energy bill. For the purposes of evaluating this article, we are directing our attention only to energy bills from customers falling within the Group B.

An energy bill is made up of the famous TE (Energy Tariff), referring to the energy consumption of the distribution system, and also the TUSD (Distribution System Usage Tariff). Finally, the additional tariff flag, the contribution to Public Lighting, the Tariff Subsidy (for rural properties) and others.

Wire B is included within the scope of TUSD, which is full of tariff components. However, in this article I mention TUSD Wire A, which are the costs linked to the maintenance and operation of transmission lines, and I also highlight TUSD Wire B, which are the costs linked to the use of the local concessionaire's distribution network infrastructure to homes, businesses, industries and rural properties.

When understanding what Fio B is, I will mention here article 27 of Law 14.300, which deals with the scaling of Fio B tariffs. The excerpt says:

“Art. 27. The energy billing of the participating units of the SECS not covered by art. 26 of this Law must consider the levy on all active electric energy compensated by the following percentages of the tariff components related to the remuneration of the assets of the distribution service, the quota of regulatory reintegration (depreciation) of the distribution assets and the cost of operation and maintenance of the distribution service:

I – 15% (fifteen percent) from 2023;

II – 30% (thirty percent) from 2024;

III – 45% (forty-five percent) from 2025;

IV – 60% (sixty percent) from 2026;

V – 75% (seventy-five percent) from 2027;

VI – 90% (ninety percent) from 2028;

VII – the rule set out in art. 17 of this Law from 2029.”

In this section of the Law, the scheduling of the Fio B charge is explained, always remembering that article 17 referred to in the VII year of the transition, deals with the delegation of power to ANEEL (National Electric Energy Agency) to determine the tariff rules that will regulate the class from the year 2029, resulting from the so-called “meeting of accounts” for valuing GD’s costs and benefits.

Therefore, anyone who started their approval process on or after January 7, 2023, is already subject to the new rules regarding non-compensation for Fio B. In other words, if your customer connected the project to the distribution network in 2023, they will start paying Fio B on their energy bill in a staggered manner over the years, as shown in the example below:

• Access Request filed on 1/7/2023: pay 15% of Fio B in 2023, 30% of Fio B in 2024 and so on until the seventh year of transition where you will be paying 90% of Fio B plus the percentage that ANEEL determine or not after the valuation of the benefits of the GD;
• Access Request filed on 1/7/2024 pays 30% of Fio B in 2024, 45% of Fio B in 2025 and so on until the seventh year of transition where it will be paying 90% of Fio B plus the percentage that ANEEL determine or not after the valuation of the benefits of the GD.

How is Wire B calculated with Law 14.300?

Does Wire B represent 28% of my energy bill? The answer is no, Wire B does not represent 28% of my energy bill.

The B Wire is an absolute value, calculated annually by the concessionaire and validated by ANEEL. The percentage of 28% was adopted as an average value for some analyses by entities in the sector, however it is essential that everyone understands how to value in absolute monetary units in R$.

After all, there are large variations from concessionaire to concessionaire as the value of TUSD Fio B depends on an analysis of the population density of each concession network (calculated by the concessionaire). The more optimized the UCs (Consumer Units) x Concession Area relationship, the cheaper the TUSD Fio B value should be.

For example: CPFL Paulista has a large volume of consumer units within its concession area, meaning that the total cost of TUSD Fio B is diluted across many units, thus reducing the final cost of using the distribution system infrastructure between all consumers in this region.

Equatorial Pará has a very comprehensive Consumer Units x Concession Area relationship, meaning there is a smaller number of consumer units (compared to CPFL Paulista) for a concession area spread over a very large territorial area. This impacts the final costs of using the structure, with this same cost being divided by few consumer units, therefore increasing the final value of the TUSD Fio B.

Practical Simulations

For comparative purposes we have (data from January 10, 2022).

Calculation of Wire B at CPFL Paulista

• B1 Conventional residential rate: R$ 0,82
• Tusd Wire B: R$ 0,1480
• Percentage of TUSD Fio B over the Tariff: 18%

Calculation of Wire B in Equatorial Pará

• B1 Conventional residential rate: R$ 0,76
• Tusd Wire B: R$ 0,3768
• Percentage of TUSD Fio B on the Tariff: 50%

According to the data above, when comparing the state of São Paulo in the concession area of ​​CPFL Paulista and the state of Pará in the concession area of ​​Equatorial Pará, it is possible to note that TUSD Fio B has a very different impact on the different states and concession areas of the country, and it is up to each one to individually assess this impact according to the concession area of ​​their customers.

To find the value of TUSD Fio B, it is necessary to consult the results of the tariff distribution processes. ANEEL and download the tariff structure of the distributor of the concession area under consultation. Using an Excel spreadsheet in the TA Application tab, it will be possible to find the TUSD Fio B.

Understanding the concept of simultaneity

When any company is called upon to provide a quote for a photovoltaic system, various data are taken into consideration to determine the sizing and proposal to the end customer. However, the most used method, in a simple and objective way, is the sizing of the system based on the potential customer's historical consumption data.

When a photovoltaic system is designed, the simultaneity factor is rarely taken into consideration by the company that quotes the system. But this scenario changes a lot and it is necessary to understand and analyze simultaneity in a post-Law vacancy scenario.

What is simultaineity or simultaneous consumption?

Let's create a hypothetical scenario by creating the characters José, Maria and family.

Imagine that Mr. José is a family man, married to Mrs. Maria and they have 2 children. Every day of the week, Mr. José, Ms. Maria and their family wake up at 6 am, have their coffee, and at 7 am everyone leaves the house. Mr. José and Mrs. Maria go to work, where they stay until 18pm and their children go to full-time school where they stay until 17:30pm.

During the day, while no one is home, the home's energy consumption is very low, limited to the television, water cooler and refrigerator connected to the sockets. From 17:30 pm onwards, when the children arrive from school, consumption starts to increase.

Baths in electric showers began and more constant use of other equipment began. The air conditioning units in the living room and children's bedrooms are turned on, and this consumption pattern remains until 6am. The graph below expresses the energy consumption of Mr. José and Mrs. Maria's family over 24 hours on a normal weekday.

After several increases in the family's energy bill, they decide to purchase a photovoltaic solar energy system. The solar energy system designed to meet its consumption was a 4,5 kWp system with two 1,5 kW micro inverters, totaling a nominal power of 3 kW.

On a cloudless day in spring, Senhor João's solar energy system begins operations at 06 am, reaching peak power at 9:45 am. It remains in this operating state until 14pm and ends its operating cycle at 18pm. The energy generation by the system acquired by Mr. José is shown in the graph below:

To understand what simultaneous consumption or simultaneity is, we need to analyze the graphical representation of daily consumption X generation as follows:

The graph above has three important regions that need to be highlighted, which are:

1. Region of active consumption outside the moment of generation;
2. Injected energy region;
3. Concurrency Region.

The graph below serves to illustrate and facilitate understanding of what each area represents.

In the area shaded by the red pen we have the active consumption of the network. In the scenario evaluated, the family has a large consumption during the period in which they are at home. This consumption represents the period in which the family is continuously using the electricity distributor's network.

In the area shaded by the green pen we have the Injected energy. In the conventional logic of a residential system, what happens is the generation of excess energy during the day to accumulate credits that will be deducted from consumption during periods of little solar generation (beginning of the day and at night). In this way, this area represents the energy that is “left over” during the day and is injected into the electricity distribution network, which will be consumed instantly by someone in the neighborhood.

In the area shaded by the blue pen we have simultaneous consumption (Simultaneity). This area represents the energy that is consumed simultaneously during the generation period, that is, the unit generates energy and consumes it simultaneously. This energy does not pass through the energy meter, therefore, Wire B will not be charged for this portion.

The area shaded in blue is the main point of need for understanding to quantify the impacts of Fio B on consumers' energy bills, as simultaneous consumption is not subject to charging so far, as it does not require use of the local network. energy distributor and also does not provide energy on the local grid.

In the understanding of the defenders of Law 14.300, the use of the local concessionaire's infrastructure in periods where there is no energy injection (area hatched in red pen) must be charged in the Fio B payment method for this period of consumption.

A very conflicting point of Law 14.300 is that the energy injected into the grid (area shaded in green) also relieves the distribution system and the consumer does not benefit from providing this relief, he will only have the obligation to pay Wire B, not being a two-way street between energy consumer and distributor.

Therefore, the calculation of the percentages of Fio B will be determined based on the injection of active energy into the local energy distributor's electrical network.

Connect to other insights

Law 14.300: What is it and how to calculate the simultaneity factor?

Calculating Wire B in practice

We finally arrive at the central point of this article, which is discovering how to effectively calculate the impact of Wire B on the energy bills of a B1 residential customer. We are also considering that the TUSD Fio B and the supply tariff will not change over the years to facilitate understanding. For calculation purposes, we did not isolate the ICMS deduction in TUSD compensation, so that the scenario is as close to the real one.

Also for calculation purposes, we will simulate the impacts on an energy bill in the state of São Paulo (CPFL Paulista) and the same impact on an energy bill in the state of Pará (Equatorial Pará).

• Simulation data: Conventional three-phase residence B1;
• Family consumption profile: For this study, we will adopt the same consumption as that of Mr. José and Mrs. Maria's family, mentioned above;
• Average monthly consumption: 1000 kWh;
• Average simultaneous consumption: 200 kWh;
• Average distribution network consumption: 800 kWh;
• Standard Wire B: corresponds to Wire B collected on January 10th on the website ANEEL;
• Proportional tariff: corresponds to the value in reais of Fio B multiplied by the tariff percentage corresponding to the reference year;
• Distribution network consumption: corresponds to the minimum three-phase tariff of 100 kWh multiplied by the energy tariff with taxes;
• Account Law 14.300: corresponds to the simulated average consumption of the distributor's network (800 kWh) multiplied by the proportional value of wire B to be paid.

In the simulation, the year 2029 was not considered, because the additional tariff (or not) that will be determined by the ANEEL until June 2023, the date on which the 18 months for valuing the benefits and costs of GD are completed.

Many doubts still exist regarding the cost of availability. The example above is not quantified for new entrants after the expiration of the law's vacancy period. Therefore, I will mention Article 16 of Law 14.300 in a commented way to exemplify why the availability cost no longer exists:

“Art. 16. For compensation purposes, the injected energy, surplus energy or energy credit must be used up to the limit in which the value in currency related to the billing of the consumer unit is greater than or equal to the minimum billable value of energy established in current regulations.”

This section of the law eliminates the duplicate availability cost, which has always been questioned, and implements such elimination immediately for all those referred to in article 26.

This deals with consumers who already have solar energy projects or who are going to submit an access opinion up to the vacancy limit, therefore, the doubling of the availability cost that was previously charged in monetary units and also in credits is immediately eliminated. compensation. Now you will only be charged in monetary units.

However, we must also understand another section that is a paragraph within Art. 16.

“§ 1 For consumer units participating in the SCEE not covered by the caput of art. 26 of this Law, the minimum billable value of energy must be applied if the consumption measured in the consumer unit, disregarding compensation from the SCEE, is lower than the minimum billable consumption established in current regulations.”

This paragraph of article 16 is fundamental to understanding what new accounts look like. To understand it, I'll break it down:

“§ 1 For consumer units participating in the SCEE not covered by the caput of art. 26 of this Law”

This section refers to all those who are not beneficiaries of the acquired right of the current rules, that is, those who requested their access opinion after the vacancy:

“the minimum billable value of energy must be applied if the consumption measured in the consumer unit, disregarding compensation from the SCEE, is lower than the minimum billable consumption established in current regulations.”

In a simplified way, this text says that, when defining whether there will be a minimum tariff or not, the active consumption registered will be observed. I will give a practical example.

Examples of a three-phase residence, whose minimum billable value is calculated based on 100 kWh.

• Residence consumed 80 kWh from the grid.

Regardless of the quantity injected, the amount corresponding to 100 kWh must be invoiced. This is because 80 kWh is less than the minimum billable quantity.

• Residence consumed 200 kWh from the grid and injected 200 kWh into the grid.

As the amount consumed is greater than the minimum billable amount, there will be no minimum tariff charge, therefore, payment of 200 kWh multiplied by Fio B, multiplied by the percentage proportional to the year of project access request, is due.

Therefore, this section of the law is essential for everyone to understand, as it eliminates the charging of the availability cost as long as the consumer unit has consumed from the network at least the minimum billable consumption of the classification class, being 30 kWh for single-phase installations, 50 kWh for two-phase installations and 100 kWh for three-phase installations.

As we can see in the previous analysis, in the case of CPFL Paulista, where there is greater population density, Law 14.300 begins to be detrimental to the consumer's payback only after the fifth year. It's worth noting that this calculation only considers the B-line; depending on the decision to settle accounts, the result could be much worse even for areas with lower population density.

In the case of the state of Pará, the reversal of accounts already occurs in the second year of the law's transition, harming consumers' payback and meaning that in the sixth year of transition the amount paid by Fio B is 3,57 times greater than the amount that would be paid for the minimum tariff.

In the context of payback, much was said about increasing consumers' return on investment by just one year. In this context, we will also carry out a financial analysis of the investment, considering the current scenario and the future scenario. For valuation and technical analysis, the following data were taken into consideration:

• Data for simulation: Design for 1000 kWh hour;
• Investment: R$ 45.000,00;
• Analysis period: 25 years;
• CPFL energy rate: 0,82 cents;
• Equatorial Pará energy tariff: 0,76 cents;
• Generation reduction percentage: 20% in 25 years;
• Estimated maintenance cost: 1,5% of the investment value per year;
• Microinverter replacement: Value for purchasing 4 new microinverters for this system;
• Gross Financial Return: Amount saved in 300 months or 25 years;
• 25-year generation loss discount: Monetary value proportional to the 20% generation reduction over 25 years;
• Net Financial Return: Total amount saved in 300 months subtracting all costs in the same period;
• Important Note: For comparison and understanding purposes, annual inflation and monetary updates of the tariff were not considered, given that, with small variations, monetary corrections in the tariff occur in the same proportion as inflation. Variations in the acquisition costs of this same photovoltaic system over the years were also not considered.

In a simulation at CPFL Paulista, the current project (under current rules) has a payback period of 61 months. Those who installed a photovoltaic system in early 2023 have a payback period of 58 months. Those who installed their projects from 2024 onward have a payback period similar to the current one, with the payback period increasing year by approximately one month per year.

In cases like CPFL Paulista, where Fio B is relatively cheap in proportion to the total energy tariff, the impacts of the new Law are not so drastic.

The big problem is that those who acquired their systems from 2025 onwards may have a drastic variation in their payback depending on the decision of the ANEEL in relation to the settlement of accounts, which can maintain only the TUSD Fio B tariff, or can even implement alternative 5, where the consumer will not offset all the tariff components of an energy bill.

Pará Equatorial Simulation

In a simulation scenario in Equatorial Pará, the situation could be considered disastrous and catastrophic. Consumers who purchased a photovoltaic system in 2023 have a payback period increased by nine months, considering only the Fio B tariff.

Conclusions

Bill 5829/2019 was approved and became Law 14.300/2022. The topic continues to spark controversy and discussion among industry representatives. It's crucial that integrators understand how the bill impacts their situation to determine their position.

There are several inconsistencies in the political discourse and in the representation of the solar photovoltaic energy sector. One major inconsistency is associated with the democratization of clean energy, where several statements mention that the law facilitates and facilitates the acquisition of photovoltaic systems from the consumer's perspective, and also encourages integrators.

However, what we actually see is that the North and Northeast regions are being heavily penalized by the Fio B pricing. States like Pará, Maranhão, and Piauí were the first to suffer the impacts of the new pricing system. Therefore, the argument that Fio B benefits the poorest and democratizes the sector falls flat when we analyze that the state of Pará, for example, is in 23rd place in the poverty index with a staggering 19,2% poverty.

Meanwhile, the state of Maranhão, a major beneficiary of Law 14.300, ranks last in the country's poverty rankings, with a poverty rate of 26,3%. Therefore, the poorest are being hit the hardest. This is an example of incongruity.

This is a time for study, training, and unity among those who truly advocate for the solar energy market. Studying to draw their own conclusions about the law and the national scenario, training to provide advisory services to customers who require more technical solutions. And, finally, unity among those who truly represent the solar energy market. This unity will be crucial in limiting the project's negative impact on energy bills.

As a final conclusion, my recommendation is that we fully focus our attention on the valuation criteria and studies that ANEEL will do with regard to the benefits and costs of distributed generation.

The result of this study could even completely sink the solar energy market. If we do not engage in demanding representation in the analysis, if we do not get involved in public consultations, we can expect the worst.

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