Brazil’s electricity regulator, ANEEL (Agência Nacional de Energia Elétrica) has postponed a decision on rules for energy storage systems after director Fernando Mosna requested more time to examine how such systems should be charged transmission and distribution use-of-system tariffs.

During its board meeting on Tuesday (August 12), the agency had appeared close to approving a 30% cap on the reduction of the amount of transmission and distribution system usage charges (known as MUST/D) for generators seeking to hybridize their assets with storage. The proposed limit had been raised from 20% in the technical department’s initial recommendation.

In his vote, rapporteur director Daniel Danna argued that storage facilities should pay transmission charges under the same framework as other market participants, in line with existing legislation. “It should be up to the developer to decide on the contracting arrangement best aligned with their business model,” Danna said. “This regulatory choice corrects a negative externality inherent in dominant-profile proposals that ends up discouraging efficient network use during off-peak operations.”

Danna said he saw no reason at present to introduce a separate tariff structure specifically for storage projects, making the argument that making energy storage pay the same grid usage fees as other participants incentivizes them to operate more efficiently.

However, he acknowledged that ANEEL should study the topic further for potential inclusion in its 2027–2028 regulatory agenda.

Mosna criticised the idea of deferring the tariff debate to a future agenda and initially suggested that Danna withdraw the proposal from the board’s schedule to allow more analysis. Danna responded that his position was already well-formed. When the vote was taken, the other directors — including ANEEL’s general director, Sandoval Feitosa — supported Danna’s proposal, but Mosna formally requested to review the case (“pedido de vistas”), halting the process without a set date for resumption.

Higher ceiling for transmission use reduction

The rapporteur’s proposal also expanded the MUST/D from 20% to 30% for generation plants adding storage.

According to an ANEEL technical note, a simulation suggests that for a plant with a maximum contracted transmission demand of 100 MW, a 30% reduction in MUST/D would correspond to storing 18.3% of total generation. The agency noted that, in general, there is no technical feasibility to reduce peak grid injection much beyond 40%.