The National Electric System Operator (ONS), the National Electric Energy Agency (ANEEL) and the Energy Research Company (EPE) have jointly released a technical note with the figures for remaining grid capacity for the connection of energy storage systems. The document, announced by ONS on September 30, 2026, focuses on the 2026 capacity reserve auctions and is available on the official websites of the three institutions. For those developing battery projects in Brazil, it is one of the most relevant references in the competitive process.
What the technical note presents
The core of the document is information on how much can still be connected to the grid for storage projects. In general terms, remaining capacity, also called connection margin, indicates the space available at system substations and busbars to receive new projects without compromising the safe operation of the grid. This data depends on electrical studies that consider the current system configuration, planned works and projects that already have guaranteed access.
The fact that the publication is joint deserves attention. Each institution plays a specific role in the sector:
- ONS: responsible for operating the National Interconnected System and for grid performance studies;
- ANEEL: the regulatory agency that runs the auctions and sets the sector's rules;
- EPE: responsible for energy planning and for the technical qualification of projects in the auctions.
The coordinated action of the three entities gives the document the status of an official reference for designing bids.
Why connection margin matters in capacity auctions
Capacity reserve auctions, known by the acronym LRCAP, procure available power to ensure demand is met at times of greatest system stress. Battery energy storage systems, known as BESS (Battery Energy Storage Systems), fit this product well, since they can charge during periods of slack and inject energy quickly when the grid needs it.
In auctions of this kind, a good technical project and a competitive price are not enough. The chosen connection point must have room to receive the power offered. When several projects compete for the same busbar or the same electrical region, the available margin becomes a limiting factor, and bids located at saturated points may be left out even if they are economically attractive. That is why the release of these figures is a decisive step in the auction preparation cycle.
How to use the document in project strategy
With the official figures in hand, development teams can cross-reference the list of points with available connection capacity against factors such as land availability, environmental licensing, equipment logistics and interconnection costs. Projects already underway can be reassessed, and possible access alternatives can be compared based on official data rather than only on in-house estimates.
What changes in practice for the BESS market
The publication of the technical note has direct effects on different links in the storage value chain:
- Developers: gain an official basis to choose access points, prioritize sites and calibrate the power offered, reducing the risk of registering projects at locations without grid space.
- EPCs: can bring forward engineering studies, substation layouts and connection budgets for the sites with the greatest chance of feasibility.
- Battery and inverter manufacturers: can see more clearly where demand is likely to concentrate and prepare technical and commercial offers aligned with project size.
- Service and component suppliers: transformers, control systems, civil works and logistics get a more concrete signal for planning service capacity.
In ENLACE's assessment, the moment calls for a careful reading of the document and quick decisions. Connection margin is a finite and contested resource, and those who align location, engineering and commercial strategy earliest are likely to reach the auction with stronger, more competitive bids.