The Brazilian government is set to launch its first-ever large-scale auctions for Battery Energy Storage Systems (BESS) in December 2026, creating a major new market expected to mobilize up to R$20 billion ($3.9 billion) in private investment, but the plan is immediately clouded by a regulatory dispute over who will ultimately pay the cost of the new infrastructure. The National Electric Energy Agency (ANEEL), Brazil’s federal electricity regulator, is finalizing the rules for the tenders, which are designed to integrate the country’s booming solar and wind power generation and inject reliability into the national grid.