CNMC rules Spain's new demand grid-access capacity methodology (EEDD) cannot apply retroactively to pre-map hybridization requests

In Resolución CFT/DE/163/26 (dated 17 September 2026, published 1 October 2026), the CNMC upheld a grid-access conflict filed by ISC GREENFIELD 7 against Red Eléctrica de España (REE), annulling REE's 1 April 2026 suspension of a request to hybridize a 60MW storage facility with the existing Valle 4 PV plant at the Valladolid Nuevo 220kV substation. CNMC determined that the capacity-evaluation criteria of the new 'Especificaciones de Detalle de Demanda' (EEDD, Resolución de 1 diciembre 2025) do not apply to access requests filed before the publication of the first capacity map on 20 February 2026, even though the shared-capacity-zone classification that triggered the suspension is itself a direct consequence of applying the new EEDD methodology. REE was ordered to re-evaluate the request under the pre-EEDD transitional criteria of Circular 1/2024 (security, regularity, quality of supply, sustainability and economic efficiency) within 15 business days of notification.

The ruling resolves a recurring legal dispute over the temporal scope of Spain's new demand-side grid access capacity methodology, directly affecting storage-hybridization and new-connection requests caught in 'shared capacity zones' where transport-distribution reference values remain unagreed beyond the EEDD's own two-month deadline. It is the second such CNMC ruling (after CFT/DE/063/26, 30 July 2026) against REE's application of the EEDD, creating a precedent that likely unlocks a backlog of suspended hybridization/storage connection applications nationwide and signals unresolved structural gaps in TSO-DSO coordination on shared-capacity-zone reference values.

This decision addresses a transitional-rules gap in Spain's newly implemented grid-access capacity allocation framework (EEDD de Demanda, effective from the first capacity map on 20 Feb 2026). The core design tension is that 'shared capacity zones'—a construct introduced by the EEDD methodology itself—were being used by the TSO to block legacy (pre-map) applications, effectively applying new, stricter rules retroactively. CNMC's interpretation (confirmed for a second time) protects regulatory predictability for developers who filed before the new regime took effect, but it also exposes an unresolved structural issue: TSO-DSO disagreement on reference values in shared nodes (here, Medina del Campo and Tordesillas) persists well past the two-month deadline set in the EEDD, leaving capacity allocation unresolved for affected substations. This is likely to generate further conflicts until the reference-value methodology between transport and distribution is fully settled, and raises operational-security considerations flagged by the System Operator regarding voltage-dip robustness if capacity is granted without full shared-zone visibility.

Ley 24/2013 del Sector Eléctrico (art. 33); RD 1183/2020 de acceso y conexión; Circular 1/2024 (disposición transitoria segunda); Resolución EEDD de Demanda de 1 diciembre 2025; Ley 39/2015 del Procedimiento Administrativo Común; Ley 3/2013 de creación de la CNMC

REE to re-evaluate GREENFIELD's access and connection request for Valle 4/BESS Valle under pre-EEDD transitional criteria within 15 business days of notification

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