ACER calls for improvements to the 2025 European Resource Adequacy Assessment (ERAA)

ACER approves the European Resource Adequacy Assessment proposed by the European Network of Transmission System Operators for Electricity (ENTSO-E) for 2025 (ERAA 2025). This draft ERAA was submitted in December 2025 for ACER’s review.

While this marks an important step towards securing Europe’s electricity supply, the ACER approval decision is accompanied by a letter addressed to ENTSO-E. The letter raises concerns about the assessment, in particular persistent methodological gaps and last-minute changes introduced by ENTSO-E shortly before submission, without proper stakeholder consultation. These include a supplementary approach to modelling investment behaviour, which led to a second, less robust set of results that ACER removed to ensure overall robustness.

As the ERAA is increasingly used to justify national measures (such as capacity mechanisms under the EU State aid framework), ACER emphasises the need to safeguard its technical integrity and ensure early, transparent cooperation. 

What does ACER say about the ERAA 2025? 

While the ERAA 2025 provides an important 10-year outlook on resource adequacy, ACER’s analysis identifies several critical areas where further improvements were needed:

• Address model inconsistencies between the investment and adequacy modules, which may otherwise systematically overstate adequacy concerns, leading to unnecessary or costly market interventions.
• Move towards a revenue-based investment module to better reflect whether market revenues can sustain existing capacity and support new investments, particularly in flexible resources (e.g. batteries).
• Reinforce procedural transparency to ensure significant changes are introduced in a timely manner and subject to proper stakeholder consultation. This includes greater transparency on ENTSO-E’s website on what is still a draft ERAA, hence subject to ACER's approval.

Without these improvements, the ERAA risks losing its usefulness as a reference for policy decisions.

What’s next? 

The ERAA 2025 was the last edition before the entry into force of the amended ERAA methodology (March 2026). From the upcoming 2026 edition, ENTSO-E will progressively integrate the amended methodology into future reports. 

ACER will hold a webinar on the updated ERAA methodology on 26 May 2026.

Full implementation of this methodology is needed to support the fast-track approval of capacity mechanisms under the Clean Industrial State-Aid Framework, such as indicating how much firm capacity is needed and calibrating technology-specific derating factors to determine how much each technology can be relied on to deliver when needed. 

Looking ahead, ACER identifies several priorities for ENTSO-E for the ERAA 2026:

• Adopt a revenue-based investment module to improve model coherence and provide a more realistic view of which capacities remain economically viable.
• Work on the full implementation of the amended methodology, introducing the "Trends and Projections" scenario to reflect the observed pace of the energy transition, and deliver capacity mechanism-related parameters to support the fast-track State aid approval process for capacity mechanisms.
• Ensure a more transparent and cooperative development process, including early alignment on methodological changes to ensure timely and efficient delivery of future ERAA annual assessments.
• Strengthen the hurdle rate method used in the assessment to better reflect investors’ risk aversion.