Europe | ACER to Release Open-Source Model to Assess Electricity Storage and Flexibility Needs

The European Union Agency for the Cooperation of Energy Regulators (ACER) is set to release a preliminary version of EU-Flex, an open-source electricity market model designed to assess flexibility needs across Europe. Scheduled for publication on 5 November 2026, the model will help identify gaps between the electricity system's flexibility requirements and the resources available to address them, including battery energy storage and demand-side flexibility.

The initiative will support the EU's first Union-wide assessment of electricity flexibility needs, planned for July 2027, as Europe continues to integrate growing volumes of renewable energy into its power system.

EU-Flex to Support Electricity System Planning

Electricity system flexibility refers to the ability of the power system to respond to changes in electricity generation, consumption and grid availability. As solar and wind power expand across Europe, flexibility resources are becoming increasingly important for balancing variable renewable generation with electricity demand.

Energy storage systems, demand response and cross-border electricity interconnections can all contribute to system flexibility. Batteries, for example, can store surplus electricity when generation is high and discharge it when demand rises or renewable output declines.

EU-Flex is intended to help assess the scale of flexibility required across the EU and identify potential gaps between these needs and available resources. Its findings will also help inform recommendations addressing flexibility challenges that extend beyond individual national markets.

Open-Source Model to Enable Industry Participation

ACER's preliminary release will include the model's source code, an explanatory paper, test-case input data and documentation describing the underlying methodology.

Making these materials publicly available will allow electricity market participants, researchers and system operators to examine the modelling approach, test its application and provide feedback before the EU-wide assessment is conducted.

The initiative is designed to improve transparency in how flexibility needs are evaluated and to identify potential limitations or areas for improvement in the model's methodology.

Consultation to Run Through December 2026

ACER's public consultation on the preliminary EU-Flex model is scheduled to run from 5 November to 17 December 2026. Transmission and distribution system operators, national regulators, public authorities, energy companies, researchers and other interested stakeholders are invited to participate.

Feedback on the accompanying paper and methodology will be collected through the formal consultation process, while technical feedback on the model will be submitted through ACER's public GitHub repository.

ACER will also hold an online webinar on 17 November 2026 to introduce EU-Flex, explain its main features and demonstrate how users can configure and run the model.

Implications for Europe's Energy Storage Market

The development of EU-Flex reflects the growing importance of flexibility planning as renewable energy deployment reshapes Europe's electricity system. By providing a common modelling framework, the initiative could help stakeholders better understand where additional flexibility resources may be needed and how cross-border system requirements interact.

For the energy storage sector, the assessment could provide useful context for evaluating the potential role of battery storage alongside demand response and other flexibility solutions. However, the model itself does not mandate specific storage capacity targets, approve individual projects or provide funding.

The results of the first EU-wide assessment, expected in July 2027, will contribute to the broader process of identifying flexibility needs and informing future policy and investment decisions across Europe.