The 2025 Consolidated Annual Activity Report outlines ACER’s regulatory work and achievements over the year. It also reviews how ACER delivered on its 2025 work programme. 

The report highlights ACER’s role in advancing the integration of the EU’s electricity and gas markets while safeguarding market integrity through surveillance activities under REMIT (the Regulation on Wholesale Energy Market Integrity and Transparency). 

It was adopted by ACER's Administrative Board on 28 May 2026, following approval by the Board of Regulators.

What were the main developments in 2025?

• Electricity markets: After several years of preparation, 2025 marked the launch of the 15-min market time unit for day-ahead and intra-day markets to better integrate renewable energy sources. Linked to this, ACER also worked to further foster demand response and flexibility, monitored related market barriers and the integration of additional transmission system operators (TSOs) into EU balancing platforms. During 2025, ACER also contributed to the investigation of major incidents, including the Iberian blackout. ACER also continued working on the implementation of the Network Code on Cybersecurity related to cross-border electricity flows.
• Gas and hydrogen markets: ACER took up new tasks under the recast Gas Regulation, focusing on the new provisions and advancing gas decarbonisation and the hydrogen market. This included developing a cost-efficiency comparison framework for natural gas TSOs and revising the Capacity Allocation Mechanisms and Interoperability Network Codes. ACER also continued to monitor wholesale gas and liquefied natural gas (LNG) markets and expanded its hydrogen market monitoring.
• Infrastructure & security of supply: ACER continued to assess EU infrastructure planning and possible improvements to the process, as set out in several opinions and reports. Other key monitoring reports identified best practices on transmission and distribution tariff methodologies. ACER also monitored security of supply within Europe and approved the European Resource Adequacy Assessment. A new workstream on flexibility was launched, with a first milestone reached in 2025 through ACER’s Decision on an EU-wide methodology to assess flexibility needs in Europe. 
• REMIT: ACER continued to improve and expand its market surveillance activities. In 2025, over 14,000 alerts were screened for potential market abuse and more than 1,300 cases shared with national regulatory authorities, leading to over €13 million in fines. ACER also collected more than 19 billion transaction records and published its first surveillance performance reports. It supported the implementation of revised REMIT and the European Commission’s preparation of the REMIT Implementing Regulation, as well as the Delegated Act for registered market participants and inside information platforms. ACER also launched the new REMIT Data Reference Centre and Inside Information Access Point.

In March 2026, ACER received a proposal from the European Network of Transmission System Operators for Electricity (ENTSO-E) to amend the methodology for the regional sizing of reserve capacity. After reviewing the proposal and exchanging with stakeholders, ACER has decided to amend the methodology.

What is the methodology about?

The methodology for the regional sizing of reserve capacity (first approved by ACER in 2023) allows regional coordination centres (RCCs) to assess the reserves needed at regional level, taking into account volumes shared between transmission system operators (TSOs) through bilateral agreements. 

This coordination helps reduce procurement costs and ensure a more efficient distribution of reserves across Europe. Based on their assessment, RCCs provide TSOs with recommendations on how to optimise reserve capacity volumes, leveraging the flexibility of the EU electricity system.

What’s new in the amended methodology?

As previously requested by ACER, the methodology now:

• Establishes that all RCCs must rely on data from the previous 12 months when assessing the minimum volume of reserves needed for the following year. This ensures the data used reflects the most relevant and frequent system conditions.
• Specifies, for each system operation region, how much reserve capacity is needed to cover positive and negative imbalances. 
• Introduces a 24-month rolling implementation deadline for assessing the short-term availability of reserve capacity (for sharing agreements established after 1 July 2026).
• Enhances transparency by strengthening and streamlining RCCs’ reporting obligations.

These changes will help RCCs size reserve capacity more efficiently, address TSOs’ operational risks and enhance the process’ transparency and coordination.

What are the next steps? 

As previously agreed, RCCs must implement the methodology’s main changes by 1 July 2026.

As the EU moves towards a decarbonised energy system, the role of gas is evolving. Reducing fossil gas dependence can support the EU’s 2050 climate neutrality target, while also raising important questions around security of supply, affordability and competitiveness.

ACER’s 2026 Monitoring Report on decarbonising the EU's gas market, published today, examines four key dilemmas:

1. Can renewable gases reduce gas import dependency while keeping energy prices affordable?
2. Will natural gas continue to shape electricity prices during the energy transition?
3. Can the EU decarbonise its gas sector without undermining industrial competitiveness?
4. How can methane emissions be tackled, given the potential for low-cost abatement but rising implementation risks?​

What did ACER monitoring find? 

ACER’s monitoring shows that gas decarbonisation can follow two main strategies: Displacing natural gas, by reducing demand or switching to renewables, and reducing its greenhouse gas footprint, for example through carbon capture, storage and measures to address methane leaks.

• Gas demand reductions are not guaranteed. EU gas demand reached 340 bcm in 2025, up 2% from 2024, which could slow progress towards the EU’s decarbonisation goals. Gas continues to provide system flexibility and remains important for industrial competitiveness.
• Gas still affects electricity prices and industry. Gas-fired power plants were economically competitive in 40% of hours in 2025, while low-carbon electricity systems paid on average 40% less than more carbon-intensive peers.
• Biomethane is promising but still limited. Biomethane is the most mature renewable gas option, but with 4.3 bcm of output in 2024, it represents only 2% of gas network injections.
• Methane emissions remain a supply-chain challenge. 85% of methane emissions linked to EU gas and oil consumption occur outside the EU, making implementation of the EU Methane Regulation key but challenging.

Together, these findings show that no single solution can decarbonise the gas sector. A balanced portfolio of technologies and policy measures will be needed, including electrification, biomethane, hydrogen, carbon capture and storage, methane emissions reduction and clean flexibility solutions.

Webinar

ACER will hold a webinar to present the main findings of this report. 

When? 24 September 2026 at 10:00 CET. 

Register for free.

On Thursday 16 July 2026, ACER will open a public consultation on an Annex to the Guideline on REMIT transaction reporting, covering energy derivative transactions.

What is it about?

REMIT is the EU-wide framework that detects and deters market manipulation and abuse in wholesale energy markets. The Regulation was revised in 2024 to keep pace with evolving market dynamics, and its secondary legislation was updated in April 2026 with new and revised obligations.

To reflect these regulatory developments, ACER is updating its guidance, including a new Guideline on REMIT transaction reporting (see ACER’s consultation).

Why are we consulting?

To complement the new Guideline, ACER has developed a dedicated Annex on the reporting of energy derivative transactions. The Annex:

• Clarifies the scope of reporting under REMIT and Regulation (EU) 648/2012 on over-the-counter (OTC) derivatives, central counterparties and trade repositories (‘EMIR’).
• Explains how REMIT reporting exemptions apply for derivatives that are already reported under EMIR.

ACER is seeking stakeholder input to ensure the Annex is clear, practical and supports consistent data reporting across the EU.

Have your say!

The public consultation runs from 16 July to 11 September 2026. Share your views.

ACER is hoping to hear from any interested parties, including but not limited to market participants, national regulatory authorities, registered reporting mechanisms (RRMs) and organised marketplaces (OMPs).

In this process, ACER will also cooperate and consult with the European Securities and Markets Authority (ESMA).