Red Eléctrica (REE) published Spain’s demand access capacity maps for the transmission grid, for the first time on the 20th of February 2026. The data reveals a highly constrained grid, with 75% of transmission nodes already at capacity. Yet for BESS developers, the picture is more nuanced, as there is a dedicated storage capacity category highlights headroom that is not available to other demand types, and the February 2026 maps show where that opportunity is concentrated.

In this article, we look at:

The state of the grid and the existing storage pipeline
How the remaining capacity is allocated between free access and competitive tenders
Available BESS capacity at the node level
Available BESS capacity per region, and the factors that condition it

For additional information on this topic, reach out to the author - paulo@modoenergy.com

22 GW of BESS permits have already been granted

REE’s February 2026 publication reveals that 75% of transmission grid nodes have no remaining capacity for new connections. Only 25% of nodes retain any headroom, available through either priority access or competitive tender. The scale of already-granted permits explains much of that saturation: 22 GW of storage access and connection permits have been issued across the transmission network, alongside 19 GW for demand.

Spain’s installed BESS capacity was just 25 MW at the end of 2024, according to REE’s annual system report. The 22 GW of granted storage permits represents a pipeline of 880 times the current installed capacity. Projects holding permits have five years from the date of issue to enter service, meaning the clock on some of the earlier grants is already running.

Apart from this, there is an additional 16 GW of storage awaiting permit approvals, which further highlights the desire among BESS investors to enter the Spanish system.

Not all remaining capacity is directly accessible

The available capacity that remains after accounting for existing permits is not uniformly spread. REE distinguishes between capacity assignable by priority order (acceso libre), which is assigned on a first-come-first-served basis, and capacity reserved for competitive tender (concurso). Nodes where demand from multiple applicants exceeds available supply trigger the tender process under Real Decreto 1183/2020.

For demand, the first tender concluded on the 26th of February 2026, awarding 928 MW across five nodes to industrial projects linked to over €3.1 billion in committed investment. Selection criteria weighted both investment volume and proximity of the projected connection date, favouring projects with nearer commissioning timelines.

The distinction matters for project timelines. Free-access capacity can be granted directly once the technical conditions are met, while tender capacity requires an additional competitive process, ministerial order, and up to 12 months for the tender itself. Developers targeting nodes with tender-reserved capacity should account for this procedural overhead in their project schedules.

Node-level capacity is the operative metric for project siting

Apart from the available capacity through tenders, REE’s monthly publication now includes node-by-node access capacity data, updated within the first five working days of each month.

The available capacity at each node represents the maximum admissible demand that can be added to the node while ensuring a secure grid according to 3 criteria: static, dynamic, and short-circuit restrictions. The available capacity will be the lowest permissible according to all 3 of these criteria.

Considering the individual capacity in each node, the total available capacity amounts to 97.5 GW, with capacity in individual nodes (with available capacity) ranging from 4 MW to 1290 MW, across different voltage levels.

Connecting a battery reduces available capacity in nearby nodes

The 97.5 GW headline overstates the real opportunity. The dynamic security criterion limits how much demand can be disconnected in a single grid fault to 1.3 GW. Because a fault at one node can trigger disconnections at nearby nodes, the available capacity at any one node is partly shared with its neighbours. Connecting a battery at one node eats into the headroom of surrounding nodes.

We modelled three scenarios to illustrate this effect:

Faults do not affect nearby nodes. Total available capacity: 94.8 GW (below 97.5 GW because some nodes already share capacity under the static criterion).
Faults affect nodes in the same region. Regions share available capacity under the dynamic criterion. Available capacity drops to 44 GW
Faults affect nodes in the same region and neighbouring regions. Neighbouring regions share available capacity under the dynamic criterion. Available capacity falls again to 39 GW.

Each scenario shows a substantial reduction in effective available capacity as BESS connects to the system.

Readers should be cautious when interpreting these results, as the actual available storage capacity will depend on many factors:

The physical distribution of transmission grid nodes
The evolution of demand connected to the system
The implications of a fault in the transmission grid

However, this information which is only available to REE itself. The evolution of the actual available capacity will depend on all of these factors, which is why REE will update these values each month.

What this means for BESS development in Spain

Spain’s capacity maps arrive at a critical moment, with a current BESS pipeline of 22 GW. The 25% of nodes with remaining capacity will face competition from multiple user types simultaneously.

For BESS, the dedicated storage capacity category provides a structural advantage. The regional concentrations in Castilla y León, Andalucía, and Galicia point to where first-mover opportunities are largest. Regardless, node-level analysis will determine whether those regional aggregates translate into viable individual project sites, particularly given cascading effects in shared capacity zones.

However, the significant available capacity should not be a reason for BESS developers to rest on their laurels. As BESS enters the system, available capacity will decrease rapidly, given the impact of additional demand on the capacity of nearby grid nodes.