Financial feasibility study of BESS vs Diesel

Article published in Magazine Canal Solar – Vol. 6, No. 6, October/2025

With the collaboration of Geraldo Silveira

As this is a recent topic in the solar sector and increasingly common in investment circles, it is important to be aware of all the nuances involved in this type of project.

Therefore, before we delve into the financial comparison between the use of BESS and diesel generators, it is extremely important to pay attention to the topics that are correlated to this topic as they will serve as a basis for understanding the premises for financial return.

Therefore, in the first part of this article, to level knowledge, topics will be covered on charging for captive market consumers, the use of diesel systems, energy storage systems, and financial return metrics.

Customer pricing system for the captive market.

The Brazilian market's customer pricing system is divided into two types of consumers, which are called free contracting environment consumers and regulated contracting consumers.

The focus of this article is on Group A's captive market customers. Therefore, to keep the article from becoming too long, we will only consider considerations related to this type of consumer.

The Brazilian market's tariff modalities for captive customers are defined by the Normative Resolution ANEEL No. 1000/2021 and in Module 7 of the Tariff Regulation Procedures – Proret.

Group A Consumers: with the exception of underground distribution network customers, who are referred to as AS-type customers, Group A customers are those served with voltages above 2.3 kV. These are subdivided according to their voltage level:

• Subgroup A1: voltage greater than or equal to 230 kV;
• Subgroup A2: voltage greater than or equal to 88 kV and less than or equal to 138 kV;
• Subgroup A3: voltage equal to 69 kV;
• Subgroup A3a: voltage greater than or equal to 30 kV and less than or equal to 44 kV;
• Subgroup A4: voltage greater than or equal to 2,3 kV and less than or equal to 25 kV.

These customers are charged amounts related to power demand and energy consumption. This article will understand that the term "energy" in the context of pricing includes the charges for the use of the distribution/transmission system (TUSD/TUST) and the charges for the use of electricity (TE).

Energy billing for these consumers is defined according to the tariff subgroup and tariff station.

Regarding the tariff station, these customers are charged for consumption at the peak tariff station – a daily period of 3 consecutive hours, with the exception of Saturdays, Sundays and national holidays – and the off-peak tariff station – a daily period consisting of consecutive hours and complementary to peak hours.

Due to the high energy demand in the power distribution system during peak hours, energy consumption at this rate is more expensive compared to energy consumption at the off-peak rate. Regarding the types of tariff subgroups, two subgroups are defined:

• Blue Hourly Pricing: Available for all tariff subgroups within Group A, with differentiated energy consumption and power demand rates according to the tariff period. It's important to remember that this customer needs to request two demand values;
• Green Hourly Pricing: available only to A3a, A4 and AS consumers, with differentiated energy consumption rates according to tariff station and a single power demand rate.

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The opinions and information expressed are the sole responsibility of the author and do not necessarily represent the official position of the author. Canal Solar.