Today, ACER releases its Opinion on the All-Island Resource Adequacy Assessments for Ireland, Northern Ireland and the Single Electricity Market (SEM) as a whole. The assessment was jointly prepared by the transmission system operators (TSOs) of both jurisdictions (EirGrid and SONI), complementing the European Resource Adequacy Assessment (ERAA) 2025.

What is a resource adequacy assessment?

The ERAA evaluates electricity resource adequacy across the EU and provides a consistent framework to assess whether additional national measures are needed to ensure security of supply. It is carried out annually by the European Network of Transmission System Operators for Electricity (ENTSO-E) and reviewed by ACER.

Member States can complement the European analysis through national adequacy assessments (NRAAs) to reflect local conditions. When a national assessment identifies differences from the European assessment, ACER issues an opinion.

What did ACER find?

ACER finds that most differences between the All-Island Resource Adequacy Assessment and the ERAA are justified, as they reflect national trends and include additional modelling detail, enhancing accuracy. 

ACER also highlights two factors with a major impact on adequacy:

• The planned second North-South Interconnector is included only in the SEM-wide assessment, meaning its contribution to adequacy is not captured in all three analyses. Once operational (expected by 2031), it would help keep adequacy risks in the SEM within the reliability standard in 2033 and 2035, strengthening security of supply across the island and highlighting the importance of increased cross-zonal capacity for resource adequacy.
• The rapid growth of data centres in Ireland (which accounted for 22% of national electricity demand in 2024 and could reach 31% by 2034) poses a key adequacy risk. New policy updates now require data centres to provide onsite or nearby generation equal to peak demand, helping reduce grid reliance and improve flexibility during stress periods. Future adequacy assessments should better reflect both the demand impact of data centres and the extent to which policy measures can mitigate adequacy risks.

What are ACER’s recommendations?

To further strengthen the assessment, ACER recommends that TSOs:

• Include a viability assessment of adequacy resources in the central scenario to confirm the required resources are realistically available. 
• Ensure revenue consistency between market viability and dispatch models so that both tools reflect aligned market revenues and investment signals. 
• Consider multiple revenue streams in the assessment to provide a more robust evaluation of resource profitability. 
• Include the planned second North-South Interconnector in all the three analyses. 
• Consider greater operational flexibility for gas units during periods of scarcity. 
• Incorporate storage and demand response expansion, including flexibility from data centres, for all target years till 2035. 

What are the next steps?

ACER encourages TSOs to consider these recommendations to ensure a more accurate assessment of adequacy risks.

Europe has an EU-wide framework (called 'REMIT') to detect and deter market manipulation and abuse in wholesale energy markets. This framework counts on many parties collecting and monitoring data, all working together to ensure the integrity of Europe’s wholesale energy markets. National energy regulators are responsible for REMIT enforcement.

Today, ACER publishes its annual reports on energy market surveillance, covering:

• The preparedness of persons professionally arranging transactions (PPATs) to detect and report suspicious behaviour. PPATs are trading intermediaries such as energy exchanges, organised market places (OMPs) or brokers, who arrange or facilitate transactions in wholesale energy products.

• National regulatory authorities’ (NRAs’) analysis of suspicious transaction and order reports (STORs) submitted by PPATs, their enforcement actions and penalties.

Both reports are mandated by the 2024 revised REMIT Regulation, which expanded PPATs’ obligations for monitoring trading activity and reporting suspected market abuse to ACER and to the relevant national regulator.

What are ACER’s key findings?

ACER highlights the important role of PPAT market surveillance and NRA enforcement under the REMIT framework. 

ACER’s analysis shows that PPATs’ structural compliance with their REMIT obligations is improving. However, their market surveillance still needs to be strengthened to ensure fair, transparent and well-functioning wholesale energy markets across the EU.

ACER encourages PPATs to review and improve surveillance arrangements, systems and procedures, working in particular on the quality, completeness and timeliness of suspicious transaction and order reports (STORs) submitted via ACER’s Notification platform.

ACER also found that the number and quality of STORs submitted by PPATs in 2025 increased significantly, reaching 204 reports - double the previous year’s figure. In parallel, NRAs made steady progress in screening, prioritising and closing cases.

For PPATs, ACER identified key areas in their surveillance practices where further improvements are needed:

• Strengthen functional independence and professionalisation of surveillance teams, including through appropriate training.
• Reduce reliance on basic monitoring tools in favour of more targeted ones.
• Expand surveillance coverage to potential breaches under REMIT Articles 3 and 4 (in addition to Article 5), across all markets and products.
• Enhance proactive engagement with market participants.
• Ensure timely and complete reporting of suspicious behaviour, focusing on effectiveness rather than formal compliance alone.

Read more.

For follow-ups by national regulators, ACER recommends: 

• Strengthening PPATs’ analysis of market behaviour by providing more detailed assessments of market participants’ conduct and its impact on the market.
• Further enhancing NRAs’ capacity (staff and IT resources) to manage the growing volume and complexity of cases.
• Maintaining and expanding engagement between NRAs and PPATs to further improve reporting quality.
• Ensuring timely communication with ACER to support effective coordination and case handling.

Read more.

What's next?

Don’t miss the ACER-European Commission REMIT event on 11 June. Register here.

ACER publishes its Opinions on requests from seven national regulatory authorities for derogations from applying EU gas network codes and guidelines at interconnection points with third countries. 

These requests have been submitted by the energy regulators of Bulgaria, Estonia, Hungary, Italy, Lithuania, Slovakia and Spain, and are addressed to the European Commission and ACER (in line with the Gas Regulation). 

The Regulation widens the scope of the existing EU gas network codes and guidelines, expanding their application to third countries’ entry and exit points, starting from 5 August 2026. 

If, for specific reasons (e.g. existing long-term contractual arrangements or legal difficulties in establishing a dispute resolution procedure with transmission network operators or natural gas suppliers established in third countries), the EU rules cannot be effectively implemented, national regulatory authorities can request a time-limited derogation.

What is the role of ACER?

After receiving the derogation requests, ACER had three months to provide its opinion to the European Commission. To inform its decision-making process, ACER conducted an extensive review of each request, held bilateral discussions with the relevant national regulatory authorities and applied a harmonised approach while considering the specifics of every Opinion.

For the details of each country, see the full text of the individual ACER Opinion. In brief, ACER considers that in Hungary and Bulgaria the relevant network codes have been implemented to the maximum extent possible to date, until certain EU rules are not implemented simultaneously by the neighbouring transmission system operators.

For Estonia, Italy, Lithuania, Slovakia and Spain, ACER has carefully examined the requests and their specific conditions, providing detailed inputs to the European Commission to support the Commission’s decision.

What are the next steps?

The European Commission will decide whether to grant the derogations, taking into consideration the input provided by ACER.

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.

ACER publishes its report on unit investment cost (UIC) indicators for energy infrastructure, updating the reference values last published in 2023. 

What are UIC indicators?

Transparent cost estimation is essential for planning energy networks. Standardised reference values for specific infrastructure costs can improve the quality and credibility of assessments and enable consistent comparisons across the EU.

Under the TEN-E Regulation, ACER is required to develop and publish a set of UIC indicators and corresponding reference values every three years. These indicators provide a common framework for assessing the investment costs of comparable energy infrastructure projects.

What did ACER observe?

The 2026 ACER report provides updated cost information for energy infrastructure, expressed per unit (kilometre, installed power, capacity). It analyses the factors influencing infrastructure costs over time, using cost data and technical information collected from project promoters between October 2025 and January 2026. The report also includes additional indicators and a sensitivity analysis based on an alternative methodology that accounts for cross-country differences in labour costs.

ACER’s analysis shows that: 

• Infrastructure costs have increased above inflation across most categories (e.g. electricity lines, cables and substations). As the indicators are based on historical data from commissioned projects, they do not fully reflect current price levels and may underestimate actual costs.
• Cost drivers point to increased exposure to price volatility and dependence on supply chains, particularly for materials from third countries, as well as other manufacturing-related costs.
• Data representativeness remains limited for several infrastructure categories, with inputs unevenly distributed across countries, which can affect the robustness of the indicators. Future updates would benefit from data covering a wider range of commissioned projects across countries and infrastructure categories.

Despite some limitations, the indicators provide valuable insights into infrastructure costs and support more transparent and informed planning decisions.

Looking ahead

As the assessment is based on historical data from commissioned projects, the indicators may not yet fully reflect recent cost developments. Further work is needed to better capture these cost developments in future updates, for example by exploring alternative methodologies or taking into account recent tender outcomes. ACER notes that regulatory oversight, stronger cooperation on supply chains and better use of existing infrastructure can alleviate bottlenecks.