Spain publishes new network access rules, redefining connection of demand and storage

Spain’s Official State Gazette on Wednesday published the Resolution of December 1, 2025, issued by the National Commission of Markets and Competition (CNMC), establishing detailed specifications for determining access capacity to Spain’s electricity networks. The resolution introduces new technical criteria that will transform how demand and storage facilities connect to the grid.

The resolution defines the methodology for calculating access capacity for demand facilities – including consumption, self-consumption with generation, and storage in demand mode – whether for new connections or modifications to existing permits. These rules apply to:

• Direct consumers connected to the transport network
• Distribution operators requesting access or connection permits
• Storage or self-consumption facilities operating in demand mode

As part of the new framework, network operators must publish monthly “access capacity maps”, detailing available, occupied, and permissible capacity at each node and zone. The first maps for demand capacity will be released on February 2, 2026, and will continue to be published monthly.

If a request exceeds defined thresholds – such as representing more than 10% of a node’s short-circuit power during peak hours or surpassing certain MW levels – an acceptability report from the transmission network operator will be required, even for connections made via distribution networks.

The resolution formally defines demand access capacity per node (substation) and per zone. It also distinguishes between:

• Firm access capacity: for consumers, self-consumption with generation, and distribution networks
• Flexible access capacity: for storage facilities in demand mode

General power limits for the peninsular system are established as:

• Generation and storage (consumption mode): 600 MW at 400 kV; 400 MW at 220 kV
• Demand: 500 MW at 400 kV; 300 MW at 220 kV
• Storage (consumption mode): 600 MW at 400 kV; 400 MW at 220 kV

The resolution allows exceptional exceedances of these maximum power values provided the safety of the system is not compromised.

To evaluate applications, the CNMC introduces a short-circuit power criterion (CAWSCR), limiting the total permissible power at each node or zone when connected demand could affect electrical safety. A dynamic stability criterion is also included, ensuring that granted capacity does not violate transient or dynamic system stability requirements.

These rules provide a clear framework for integrating demand, storage, and hybrid facilities into Spain’s electricity transport network while maintaining system safety and operational stability.

MITECO’s new FAQs

Maeanwhile, Spain’s Ministry for the Ecological Transition and the Demographic Challenge (MITECO) has released a new set of frequently asked questions (FAQs) clarifying how installed capacity should be calculated for administrative authorizations under Royal Decree 997/2025, the recently approved framework establishing urgent measures to strengthen the electricity system.

As announced during the AEPIBAL Day event held last week in Valladolid, the guidance addresses the treatment of installed capacity for battery energy storage systems (BESS) – including both stand-alone and hybrid configurations.

The FAQs outline which power ratings must be used when determining installed capacity for permitting purposes and introduce a revised definition applicable to both storage and generation assets. Because an installation may include multiple electrical park modules, generation modules, and storage modules, the document first defines the installed power of each module before setting out the criteria for determining the installed power of the overall installation.

In particular, a module’s power is defined as the maximum active power of the most limiting element connected in series. The installed power of the entire installation is then calculated as the sum of the installed powers of its modules, with specific provisions for cases in which a single limiting element applies to all modules.

MITECO also clarifies which elements can be considered limiting factors. While the decree lists accepted limiting elements, components that stem from inadequate design or are clearly intended to bypass regulatory requirements cannot be treated as limiting. As such, switches, disconnectors, and conductors may never be considered limiting factors.

The FAQs further specify that the installed power of an electricity generation module is the maximum active power it can achieve, while the installed power of an electrochemical storage module is the maximum active power the module itself can deliver. The document also details the methodology for calculating installed capacity in hybrid installations.