On 18 December 2025, ACER received two proposals from all electricity transmission system operators (TSOs) to amend the implementation frameworks for PICASSO and MARI, the EU platforms for exchanging balancing energy from frequency restoration reserves.

With its Decisions 12/2026 and 13/2026, ACER approved both proposals.

What are the implementation frameworks for balancing platforms?

Established under the Electricity Balancing (EB) Regulation, the implementation frameworks harmonise how balancing service providers (BSPs) participate in electricity balancing markets across EU Member States.

These markets allow TSOs to manage unexpected differences between electricity supply and demand. PICASSO coordinates cross-border exchanges of automatically activated balancing energy (e.g. in case of sudden need), while MARI coordinates manually activated balancing energy. Together, they enable TSOs to access balancing resources across borders and maintain system stability.

What did the TSOs propose?

The TSOs proposed to further harmonise the BSP prequalification process, which ensures that power generation or demand units meet the technical and operational requirements to participate in the market and provide balancing services. 

The proposals also introduce a common process for amending the implementation frameworks of PICASSO and MARI to further harmonise the terms and conditions for BSPs.

What did ACER decide? 

ACER approved the proposals, while introducing some amendments:

• A structured harmonisation process. Every two years, TSOs will run stakeholder surveys to identify areas where the terms and conditions for BSPs still need to be aligned across countries. TSOs will then develop a common proposal for further harmonisation and publicly consult on it.
• More harmonised prequalification requirements. ACER introduced additional requirements for switching, re-prequalification, termination of prequalification and data exchange. Given the limited experience with harmonised prequalification, some requirements will continue to be set at national level, with further harmonisation expected as TSOs gain more experience.
• More prequalification options. ACER introduced three prequalification options: activation testing, ex-post verification and a fast-track process. Compared with activation testing, the other two offer faster and easier market access, as balancing services are monitored during operation instead of tested upfront. TSOs can choose any or all three options, subject to approval by their national regulatory authority.
• Easier access for smaller market participants. ACER simplified the prequalification process for smaller participants to help ensure a level playing field. As existing processes were designed around large conventional generators, ACER adapted them to make it easier for all participants that can provide secure and reliable balancing services to enter the market and improve liquidity.

What are the next steps? 

TSOs have six months to submit a proposal to their national regulatory authority to align national terms and conditions with the new requirements. Once approved, TSOs will have 24 months to implement the harmonised prequalification process.

Today, ACER releases its report on the Irish gas transmission tariffs directed at the Commission for Regulation of Utilities (CRU), Ireland’s national regulatory authority (NRA).

The report assesses whether the proposed reference price methodology (RPM) complies with the requirements of the EU Network Code on Harmonised Transmission Tariff Structures (NC TAR). 

What is the proposed tariff methodology?

The Irish NRA proposes to:

• Apply a forward-looking matrix methodology based on marginal expansion costs, allocated between entry and exit points. Under this approach, differences between tariffs at network points would reflect the expected unit cost of expanding the pipeline, rather than historical costs.

• Apply the same tariff to all exit points serving domestic consumption and a single tariff to all future renewable gas production points, regardless of their location.

• Set rules on tariff discounts for any future storage and LNG facilities.

• Continue recovering allowed revenues for transmission services through a combination of capacity- and commodity-based tariffs. Capacity tariffs are charged for contracted network capacity, while commodity tariffs are based on transported gas volumes and recover the related costs.

• Treat the Corrib Linkline (the pipeline connecting the Corrib offshore gas field to the main ring of the Irish gas network) separately from the transmission service, recovering its costs through a separate tariff.

What are ACER’s key findings? 

After analysing the consultation document, ACER concludes that: 

• The proposed methodology meets the EU requirements on cost-reflectivity, transparency, avoidance of cross-subsidisation, non-discrimination, volume risk and prevention of cross-border trade distortions.

• The criteria for setting the flow-based charge are also met.

• The criteria for setting non-transmission tariffs are not fully met, as the Corrib Linkline is treated similarly to a non-transmission service but not formally classified as such.

• The capacity forecasts used in the methodology are based on Ireland's Network Development Plan for 2024, which may not fully capture more recent demand shifts.

What does ACER recommend? 

ACER recommends that the Irish regulator, when adopting its final decision:

• Improve the description of the revenue and tariff structure of the Corrib Linkline and formally classify its use as a non-transmission service.

• Update capacity forecasts using more recent estimates and, if these show cross-system flows, reassess the methodology against the relevant NC TAR principles.

ACER also recommends that, as part of its upcoming review of the tariff methodology, the Irish regulator assess whether a methodology based on forward-looking marginal expansion costs remains appropriate in the context of the energy transition and declining gas demand.

Next steps

The Irish NRA has until 16 December 2026 to adopt a motivated decision on the reference price methodology.

See all ACER reports on national tariff consultation documents. 

ACER has issued a favourable Opinion on the decisions by the Austrian and Slovenian energy regulators to prolong the existing exemption from establishing physical bi-directional capacity at the Murfeld/Ceršak interconnection point between the two countries. The renewed extension would run until November 2029.

The extension was proposed by the Austrian and Slovenian transmission system operators (TSOs) and approved by the national energy regulators. After reviewing the coordinated decisions, ACER endorsed the proposal.

What is bi-directional gas flow capacity?

Under the European Security of Gas Supply Regulation, TSOs must establish permanent physical capacity for gas transport in both directions (bi-directional capacity) at all cross-border interconnection points between Member States.

Where building this bi-directional capacity is not justified, temporary exemptions may be granted following a detailed assessment and consultation with stakeholders, other Member States and the European Commission.

What is ACER’s assessment?

• The TSOs carried out the consultation and decision-making process in a timely and coordinated manner.
• The coordinated decisions comply with the Regulation’s requirements and justify prolonging the exemption.
• Current market signals do not indicate a need for bi-directional capacity from Slovenia to Austria.
• Building such capacity without market demand would result in inefficient investments, as costs would significantly outweigh the expected benefits for Austria’s security of supply.

On this basis, ACER considers the four-year extension justified, provided there are no significant changes in market conditions or infrastructure developments in the meantime.

What are the next steps?

ACER has submitted its Opinion to the Austrian and Slovenian energy regulators, as well as to the European Commission.

Within four months of receiving ACER Opinion, the European Commission may request modifications to the decisions.

The EU Agency for the Cooperation of Energy Regulators (ACER) is pleased to announce Mr Christof Lessenich as its next Director.

ACER, an EU Agency, is central to supporting well-functioning, integrated and resilient European energy markets that deliver clean, affordable and secure energy across Europe. The Director’s role is to head up and lead the Agency.

Christof Lessenich, a German national, brings more than two decades of experience in EU energy and competition policy. Since 2021, he has headed the Internal Energy Market Unit at the European Commission’s DG Energy, leading work on EU electricity and gas markets. Previously, he held senior positions at the European Commission’s DG Competition. Earlier in his career, he worked as a solicitor in private practice. Mr Lessenich holds a PhD in Law from the University of Bonn and an LLM from the University of Cambridge.

The appointment process for the ACER Director involved his selection by the ACER Administrative Board following an open recruitment process, a favourable opinion from the Board of Regulators and Mr Lessenich’s statement and questioning today (10 September) before the European Parliament’s ITRE Committee.

The Director’s term of office is five years, renewable once for up to five additional years. Mr Lessenich’s exact start date will be announced soon. Meanwhile, Mr Volker Zuleger continues to serve as the ACER Director ad interim, having succeeded the former Director Mr Christian Zinglersen.

ACER published its Opinion on Portugal’s National Resource Adequacy Assessment (NRAA).

The NRAA is part of the country’s electricity security of supply monitoring report, the RMSA-E 2025 (Relatório de Monitorização da Segurança de Abastecimento), and complements the European Resource Adequacy Assessment (ERAA) 2025.

What is a resource adequacy assessment?

The ERAA assesses whether the EU has enough electricity resources to meet demand and 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 this European analysis with national assessments (NRAAs) that reflect local conditions. When a national assessment differs from the European one, ACER issues an opinion.

What did the Portuguese NRAA find?

Unlike the ERAA 2025, which found no adequacy concerns for Portugal, the national assessment identified adequacy risks in all target years from 2028 to 2035.

The NRAA projects that Portugal’s loss of load expectation (i.e. the number of hours per year when demand is expected to overcome supply) will exceed the country’s 1.46-hour reliability standard. This is expected to increase over the years:

• slightly in 2028;
• by about five times in 2030; and
• by nearly fifty times in 2035.

The projected increase assumes electricity demand growing much faster than the resources needed to meet it. Compared with the reference ERAA, the NRAA assumes:

• higher demand from new energy-intensive consumers, particularly data centres;
• slower deployment of renewables;
• lower availability of pumped-hydro storage, based on historical data;
• conservative assumptions on long-term battery deployment; and 
• the shift of the Tapada do Outeiro gas-fired power plant into an out-of-market reserve, taking offline about a quarter of Portugal’s thermal capacity, normally highly available during scarcity times.

Figure: Portugal’s projected installed electricity capacity, 2028-2035

The Portuguese NRAA assumes considerably slower growth in installed electricity capacity than the ERAA 2025, with a gap of around 15 GW by 2030 and 12 GW by 2035. This is largely due to assumptions of slower wind and solar deployment in the national assessment.

Source: ACER based on the NRAA and ERAA 2025.

What are ACER’s key findings? 

ACER finds that the projected resource adequacy risks are mainly driven by assumptions of strong demand growth, while new capacity, including demand-side response, is assumed to lag behind.

At the same time, the NRAA does not adequately assess how the market could respond to increasing electricity supply scarcity. Its economic viability analysis shows that existing gas-fired generation capacity would remain highly profitable, especially long-term, as tighter supply could push prices up. However, the NRAA does not examine whether these price signals could attract investments in new resources, including batteries and demand response, and offers only a limited projection of their potential contribution to security of supply.

The national assessment also overlooks cross-border factors, such as Spain’s recently approved capacity remuneration mechanism, that could affect how much electricity Portugal can import during scarcity periods.

As a result, the NRAA may overestimate Portugal’s adequacy gap by not fully accounting for resources that could realistically enter the market or be available cross‑border.

What does ACER recommend?

To strengthen Portugal’s assessment, ACER recommends:

• Applying the economic viability assessment in line with the ERAA methodology.
• Assessing the potential for new market-based investments, particularly batteries and demand response.
• Reflecting the contribution of currently ‘out-of-market' resources, such as the Tapada do Outeiro gas-fired power plant.
• Using more realistic demand response projections.

Overall, ACER considers that a robust adequacy assessment should capture new investments that could be delivered in response to market conditions, in addition to current resource development trends.

What are the next steps? 

ACER encourages the Portuguese authorities to consider its feedback to improve the assessment.