On 11 February 2026, ACER issued its Opinion on the Winter Supply Outlook 2025/2026, published by the European Network of Transmission System Operators for Gas (ENTSOG). 

What’s in ENTSOG’s Outlook?

This year’s Outlook is particularly timely in light of the recent EU measure phasing out Russian gas imports. Against this backdrop, ENTSOG’s Outlook evaluates the gas system readiness for winter 2025/2026, considering a gradual phase-out of Russian gas. 

• EU entered winter with lower gas storage (83%) than last year (94%), but still has sufficient gas to meet demand.
• Storage levels are expected to remain above 30% by the end of winter, even if remaining Russian flows via TurkStream are fully disrupted.
• LNG availability is the main supply risk, as LNG now covers around 40% of EU gas demand.
• In a low-LNG scenario, gas storage could be depleted by the end of winter, potentially requiring demand reduction measures.

What does ACER say?

ACER welcomes ENTSOG’s extensive testing of the gas system, including cold winter scenarios, supply disruptions and updated infrastructure data. It also recognises the clear inclusion of the Russian gas phase-out in the Outlook, as well as consideration of the remaining gas dependency in the electricity sector, as highlighted in ACER’s security of supply Monitoring Report (November 2025).

However, ACER notes that a more holistic assessment of security of supply requires shifting the focus from infrastructure (which is currently not the main bottleneck) towards supply challenges and diversification. 

What does ACER recommend?

ACER recommends that ENTSOG, in its future outlooks, adjust its analysis to better reflect supply risks and market dynamics by:

• Shifting the analysis towards gas supply availability and LNG market dynamics, rather than infrastructure resilience.
• Assessing LNG supply based on EU regasification capacity and destination-free global LNG volumes, as reflected in the high-LNG scenario, rather than capping LNG supply in the reference and low-LNG scenarios only based on historic averages.

Today, ACER publishes its Opinion on the Integrated Model report for EU electricity, gas and hydrogen infrastructure planning, submitted in October 2025 by the European Network of Transmission System Operators for Electricity (ENTSO-E) and for Gas (ENTSOG) and prepared with support from the European Network of Network Operators for Hydrogen (ENNOH).

The Trans-European Energy Infrastructure (TEN-E) Regulation requires ENTSO-E and ENTSOG to jointly develop a consistent and progressively integrated model to support coordinated infrastructure planning across the three sectors (electricity, gas and hydrogen), and underpin future EU-level Ten-Year Network Development Plans (TYNDPs).

Why is an integrated modelling framework needed for EU energy infrastructure planning?

Europe’s energy transition is increasingly blurring the boundaries between electricity, gas and hydrogen systems. Decisions in one sector directly affect infrastructure needs and costs in the others. To address this, EU law requires a shift from isolated, single-sector planning towards more coherent sectoral integration of the modelling governance, processes, tools and data used in electricity, gas and hydrogen network planning.

Such an integrated modelling framework aims to ensure that EU infrastructure plans are based on consistent assumptions, aligned methodologies and comparable cross-sector assessments. It should future-proof planning and inform project-level investment decisions from a system-wide perspective.

What does ACER say about the proposed integrated modelling framework for energy infrastructure planning?

ACER’s Opinion assesses whether the ENTSOs’ submission provides a sufficiently robust basis for more coherent, cross-sector infrastructure planning at EU level.

The report is a useful starting point, with some progress beyond joint scenario development, including the creation of a dedicated cross-sector working group with balanced representation across the three sectors.

However, ACER finds the report does not clarify how the integrated modelling framework will contribute to greater consistency and integration of EU infrastructure planning through concrete milestones. The report falls short in the following areas:

• Cross-sector integration requirements are unclear, leaving implementation discretionary.
• Key integration steps are deferred to a long-term roadmap with vague timelines and under-ambitious actions.
• Stakeholder consultation was limited, with key elements excluded (draft report and roadmap).

As a result, it remains unclear whether the proposed framework will deliver practical improvements in infrastructure needs assessments, investment decision-making or system-wide cost optimisation.

What does ACER recommend?

For better EU infrastructure planning, ACER calls on ENTSO-E and ENTSOG, together with ENNOH, to be more ambitious in their approach to integrated modelling:

• Clearly define assumptions, data and methodologies to be applied consistently across sectors.
• Identify which planning steps require joint cross-sector assessment and which can remain sector-specific.
• Apply shared reference networks and indicators in project-level cost-benefit analyses (CBAs).
• Strengthen consistency in identifying infrastructure gaps.
• Ensure cross-sector needs assessments and harmonised CBA pilots are conducted within the TYNDP 2028 cycle.
• Update the roadmap with more ambitious actions and firmer timelines.
• Conduct a more thorough public consultation on the revised model and roadmap.

ACER expects that consistency in input, assumptions and methodology is already applied in TYNDP 2028, even if some deliverables remain sector-specific.

What are the next steps?

ACER expects ENTSO-E and ENTSOG to implement these recommendations before submitting the report to the European Commission for approval. ACER calls for early and meaningful stakeholder engagement as the integrated modelling framework evolves.

Today, ACER releases its report on the Polish gas transmission tariffs directed at GAZ-SYSTEM S.A., Poland’s transmission system operator (TSO), which manages the country’s two transmission systems.

The report assesses the compliance of the proposed reference price methodology (RPM) with the requirements of the EU Network Code on Harmonised Transmission Tariff structures. 

What is the proposed tariff methodology?

The Polish TSO proposes to:

• Apply a postage stamp reference price methodology with a 50-50 entry-exit split, combined with discounts for LNG terminals, biomethane producers and gas storage facilities.
• Merge the two existing entry-exit zones of the National Transmission Network (NTS) and the Transit Gas Pipeline System (SGT), the two Polish transmission systems, into a single national zone with uniform tariff rules.
• Continue recovering allowed revenues for transmission services through capacity-based tariffs only, meaning users pay based on the network capacity they book, not the volume of gas they transport.
• Maintain the current two gas sub-systems (for low-methane and high-methane gas) within the NTS.
• Keep two non-transmission services (gas pressure reduction and gas compression) in place.

What are the key findings? 

After analysing the consultation document, ACER concludes that: 

• The proposed methodology meets EU requirements on transparency, cost-reflectivity, avoidance of cross-subsidisation, non-discrimination, volume risk and the prevention of cross-border trade distortions.
• Merging Poland's entry-exit zones will create a level playing field for all network users importing gas to the country.
• The Polish TSO considered ACER’s previous recommendations (for the NTS system and the SGT system), addressing past shortcomings and developing a methodology that complies with EU rules.

What does ACER recommend? 

ACER recommends that the Polish national regulator (URE), when adopting its final decision on the proposed methodology:

• Review the low-methane subsystem and assess costs and benefits of potential measures to better align it with EU requirements.
• Carry out some additional assessments and consider technical adjustments to fine-tune the methodology.

See all ACER reports on national tariff consultation documents. 

ACER publishes today its Opinion on the draft gas and hydrogen ten-year network development plan (TYNDP) 2024 submitted by the European Network of Transmission System Operators for Gas (ENTSOG) on 20 October 2025.

What is the TYNDP?

Every two years, ENTSOG publishes a TYNDP where it:

• identifies EU’s hydrogen infrastructure needs;

• assesses new infrastructure projects to ensure security of gas supply, market integration and competition. 

ENTSOG’s draft 2024 TYNDP provides a pan-European view on hydrogen infrastructure needs up to 2040, an assessment of the natural gas curtailments under various stress cases and lists promoters’ planned projects.

ACER’s role is to assess (in an Opinion to ENTSOG) the methodologies used in the TYNDP, its development process and outcomes as well as to provide suggestions for improvement.

ACER’s recommendations aim to support investment decisions and facilitate the efficient development of the European gas and hydrogen grid, in line with broader EU policy goals.

What are ACER’s main findings on the 2024 draft TYNDP?

ACER acknowledges several improvements:

• in the methodologies used for the TYNDP development;

• on how the Hydrogen Infrastructure Gaps Identification Report in the draft TYNDP reflects ACER’s  recommendations; 

• greater transparency regarding the technical information of the submitted projects; and

• clearer presentation of the results.

While recognising the complexity of the TYNDP process, ACER notes shortcomings:

• The late delivery of the 2024 TYNDP (submitted to ACER in Q4 2025) undermines the alignment with the selection of projects of common interest (PCIs) and projects of mutual interest (PMIs). PCIs and PMIs are both categories of cross-border energy infrastructure projects under the TEN-E Regulation. PCIs are located within the EU, whereas PMIs are between the EU and non-EU countries.

• Limited implementation scope: only one scenario of future possibilities was considered, and a cost-benefit analysis was conducted only for some projects.
• Insufficient data quality and transparency, including missing costs for many projects.

• Weak connection between Europe’s identified needs and the projects being proposed by project promoters.   

What are ACER recommendations? 

To finalise its 2024 TYNDP and prepare for future editions, ACER recommends ENTSOG to:

• Ensure a timely submission of the TYNDP by addressing the root causes of the recurring delays.

• Perform cost-benefit analyses for all scenarios and projects.

• Strengthen inputs, assumptions and cost data to ensure credible results.

• Improve transparency of project information and methodological choices.

• Make the plan needs-driven, with clearer justification for proposing the specific projects.

What are the next steps?

ENTSOG should take ACER’s recommendations into account to finalise the 2024 draft TYNDP and further improve its upcoming editions.

With the adoption of the 2024 EU hydrogen and gas decarbonisation package, ACER is tasked with carrying out a periodic cost comparison assessing the efficiency of gas transmission system operators (TSOs) across the EU. 

To kickstart this work, ACER engaged a consultant to propose a methodology to benchmark the efficiency of gas TSOs. ACER has taken into account the previous (voluntary) benchmarking studies of gas TSOs, and has consulted stakeholders extensively, including an ACER public consultation, a workshop and engaged experts to conduct an independent assessment (Expert Review) of the proposed methodology.  

The consultancy study, published today, provides general guidance for ACER in designing the methodology and procedures for phase II (data collection and validation) and phase III (modelling) of the ACER efficiency comparison. Some elements of the methodology have been adapted based on the input received from third parties.

Why does the cost-efficiency of gas TSOs matter?

Ultimately, gas consumers pay the costs of natural gas transmission networks through their bill. The TSOs’ allowed revenue is set by the national regulatory authority (NRA) and is recovered from network users through network tariffs, in line with the EU-wide Network Code on Harmonised Transmission Tariff structures.

Benchmarking compares the costs of a TSO (a monopoly) to other operators in the EU. ACER’s efficiency comparison, which is mandatory for all EU TSOs, will help ensure that TSOs’ costs and the resulting tariffs across Europe are efficient. 

Why is TSO cost-comparison increasingly relevant in a decarbonised gas context?

The gas sector is evolving, with lower gas demand, the rise of renewable gases and planning for hydrogen. This may require new investment while the decreasing use of existing gas infrastructure is already driving gas network tariff increases across Member States. This ACER tool aims to provide efficiency scores in a reliable and transparent manner, reflecting different national realities and allowing for different regulatory approaches.

What’s next?

• January 2026: The second phase of the ACER efficiency comparison will start. ACER will request TSOs to submit the data that will be used for modelling in the third phase, as well as carry out a validation process to remove any reporting errors and ensure a high data quality. As part of the validation, TSOs or NRAs are expected to audit the reported data. ACER will consult with TSOs on the data that will be requested and the overall process.
• Between late Q4 2026 – early Q1/2027: The third phase will be launched to focus on the modelling of the ACER efficiency comparison. Stakeholders will be consulted on the model specifications and process in the course of 2027.
• By 5 August 2027: Completion of the first ACER efficiency comparison. Following the first publication, ACER should repeat the calculation every four years. 

Further updates will be provided along these process steps. 

ACER’s 2025 European hydrogen markets Monitoring Report looks at the latest sector developments and highlights the main regulatory and market challenges for the EU.

This year’s edition shows progress in electrolysers build-out and in advancing the EU’s regulatory framework. Yet, renewable hydrogen costs in 2024 remained four times higher than those of conventional hydrogen. This cost gap, together with incomplete national transposition of EU rules, is hindering market development. To overcome this, lower regulatory risks and more targeted funding are needed. 

What are the key findings? 

• Market growth remains insufficient to meet EU and national targets. Despite a 51% increase in electrolyser capacity to 308 MW in 2024, deployment remains way behind the 6 GW target for 2024 and 40 GW for 2030.
• Renewable hydrogen remains costly (four times higher than hydrogen from fossil fuels), with uncertain near to mid term cost reduction prospects.
• Delays in transposing EU rules at national level persist. Only 2 Member States have transposed the amended Renewable Energy Directive.
• A decarbonised electricity sector is key to renewable hydrogen. Electricity supply costs (excluding grid tariffs) may account for up to 50% of renewable hydrogen’s production costs.
• Rising electricity network tariffs may add pressure on costs. ACER’s 2024 Monitoring Report on electricity infrastructure development shows that electricity network costs could rise by 50-100% by 2050, also depending on how investments will align with evolving electricity grid demand. As electricity tariffs represent a significant share of renewable hydrogen’s production costs, this trend poses a substantial risk.
• Network development should align with evolving demand to reduce forecasted risks. Hydrogen networks are key to expanding the market, but infrastructure should be built gradually to match actual demand development.
• Low-carbon hydrogen could support market development, yet cost and technical uncertainties should be carefully assessed.
• The European Commission has already allocated over €20 billion to hydrogen through various programmes, and Member States have announced numerous additional support schemes. Accelerating the allocation of funding to advanced projects is key to increasing scale-up.

What are ACER’s recommendations?

• Accelerate the national transposition and implementation of the amended Renewable Energy Directive to ensure regulatory certainty and accelerate market development.
• Implement the (2024) Hydrogen and Gas Decarbonisation legislative package without delay to facilitate the deployment of infrastructure and a well-functioning hydrogen market.
• Prioritise and target funding towards projects in hard-to-abate sectors that are ready to transition to renewable and low-carbon hydrogen.
• Facilitate renewable hydrogen production through faster permitting and grid connection for both electrolysers and renewable electricity projects.
• Speed up decarbonisation of the power sector to lower electricity costs and enhance electrolyser utilisation.
• Enable flexibility in the electricity market, rethink electricity grid tariffs and grid incentives, as they can optimise electrolyser location and performance.
• Assess the risks of methane-based low-carbon hydrogen, including its underlying costs, infrastructure uncertainties and lock-in effects.
• Align hydrogen network development with market realities to manage market uncertainties and reduce the risk of stranded assets.

What’s next?

Register for ACER webinar: Progress in Europe’s hydrogen markets (Tuesday 9 December 2025 at 11:00 CET).

On 4 November 2025, the EU DSO Entity submitted its updated statutory documents to the European Commission and ACER. This revision follows the Hydrogen and Decarbonised Gas Market Package adopted in 2024, which extends the Entity’s membership to natural gas and hydrogen distribution system operators (DSOs). 

ACER already provided an Opinion on the previous version of the statutory documents in 2024. It will now review the updated submission and consult stakeholders before delivering its new Opinion to the Commission. 

What is the EU DSO Entity?

The EU DSO Entity was created in 2019 by the Clean Energy Package to facilitate cooperation among European electricity DSOs. The 2024 Regulation broadened the Entity’s scope to include natural gas and hydrogen DSOs, making it necessary to update and resubmit the Entity’s statutes, rules of procedure and other statutory documents to ensure fair and balanced representation of all participating operators. 

This update reflects the EU’s integrated approach to energy networks, supporting system efficiency and cooperation across transmission and distribution. ACER’s role is to ensure a fair and balanced representation across all operators considering the interests of distribution system users (e.g. generators, prosumers and consumers, aggregators, suppliers, and storage operators).

What are the next steps? 

To inform its Opinion, ACER will conduct a consultation to gather inputs from organisations representing all stakeholders, particularly distribution system users (including consumers).

The consultation will run from 21 November to 19 December 2025.

After receiving the proposal, ACER has four months to provide its Opinion to the European Commission.

This report on gas network use provides a comprehensive overview of capacity booking and usage trends in the EU, exploring how diversified supply, demand shifts and evolving capacity booking strategies are reshaping gas flows across the EU.

This monitoring report compares gas capacity use and booking data from 2021 to mid-2025 and analyses the main market shifts triggered by the energy crisis in 2022 (e.g. phase-out of Russian natural gas, increase in liquefied natural gas (LNG) imports, and lower gas demand). It also examines the impact of ending Russian gas transit via Ukraine as of 1 January 2025 on flow dynamics and capacity use across Southeast Europe.

What are the key findings? 

The EU’s integrated gas system has proven resilient to the energy crisis, reconfiguring its gas flows in response to changing supply and demand patterns. 

• Europe’s reliance on Russian gas pipeline imports has fallen from circa 40% to 6% of total imports since 2021.
• Since the end of 2021, gas flows have reversed direction at 40% of gas interconnection points across the EU, driven by the phasing out of Russian pipeline gas.
• Lower gas demand and increasing LNG’s supply reduced transit flows in some countries, leading to fewer capacity bookings and putting upward pressure on tariffs.
• Capacity bookings are adapting to new gas market conditions. Many long-term legacy contracts are expiring or have been terminated due to the Russian invasion of Ukraine. Instead shippers are now securing capacities on alternative routes through auctions underpinned by the EU-wide capacity allocation mechanism (CAM) network code.
• Lower pipeline congestion at EU level, but some supply bottlenecks persist. Infrastructure upgrades and lower gas demand have eased the peak congestion that affected Northwest Europe in 2022. Since 2024, high network use in Southeast Europe (including increased gas volumes to Ukraine in 2025 following the end of Russian gas transit), created significant congestion risks at several interconnection points in the region.

What are ACER’s recommendations?

• Transmission system operators (TSOs) should enhance transparency and coordination in gas capacity optimisation.
• National regulators should ensure a full and consistent application of the EU rules (CAM network code) without exceptions to maintain a transparent, predictable, and standardised capacity allocation process, fostering competition and integration of EU gas market.
• Future gas infrastructure investment by Member States should be targeted to solve persistent bottlenecks, align with the EU’s energy and climate goals and ensure security of supply. Regulators must ensure transparent and efficient distribution of congestion revenues to reduce and stabilise tariffs for European network users.

What are the next steps?

ACER will provide its next key developments in European gas wholesale markets report in early 2026. See the Q3 2025 monitoring report, also published this week.  

Published today, ACER’s latest report on key developments in European gas wholesale markets examines key trends in gas supply, demand and market prices during the final months of the gas summer season (July to September 2025). The analysis helps inform policies aimed at ensuring secure and competitively priced gas in the EU. 

What trends did ACER monitoring find? 

• Wholesale prices and volatility declined, marking one of the calmest periods for European gas markets in recent years. Higher gas imports, stable consumption and orderly storage filling contributed to this stability.
• Gas storage: Injections into underground storage exceeded levels of the previous two summers. European stocks reached 82% capacity, below levels at the start of the last three heating seasons, leaving EU markets more reliant on imports this winter.
• LNG imports: Liquefied natural gas (LNG) imports rose by 38% year-on-year amid high storage demand and lower Russian pipeline supply. Stable demand from other major buyers and rising global LNG production contributed to lower prices despite higher import volumes.
• EU gas market integration drove gas flows in the right direction to Central and Eastern Europe: As LNG’s share of supply grew, gas flows were redirected eastward to markets with limited or no direct LNG access, reflecting wholesale market signals (from lower- to higher-priced hubs).

ACER releases two reports assessing whether the proposed reference price methodologies for the Croatian and Finnish natural gas transmission tariffs comply with the EU Network Code on Harmonised Transmission Tariff Structures.

The reports are addressed to:

• the Croatian national regulatory authority (NRA), Hrvatska energetska regulatorna agencija (HERA); and
• the Finnish natural gas transmission system operator (TSO), Gasgrid Finland Oy (Gasgrid).

ACER finds that Croatia’s proposal makes only minor adjustments to the previous well-functioning methodology (last updated in 2019), while Finland’s proposal retains its existing approach (2020) without addressing some of ACER’s earlier recommendations.

What is proposed?

Croatia proposes to:

• Keep the current postage stamp reference price methodology, with a 60/40% split between entry and exit points.
• Phase out the current tariff discount at the Krk LNG terminal entry point to the transmission system.
• Continue recovering all transmission revenues through capacity-based tariffs.
• Pre-set tariffs for a five-year period, with different tariff levels each year.

Finland proposes to:

• Keep the current postage stamp reference price methodology at domestic exit points.
• Remain in the Finnish-Estonian-Latvian (FinEstLat) market area, applying common entry tariffs and zero tariffs at interconnection points within the area.
• Establish a commodity-based connection capacity charge to recover costs fairly from users that consume gas only during peak periods. 
• Maintain the flow-based charge.
• Apply two non-transmission tariffs: a datahub charge and the Balticconnector underutilisation fee (charged when network users cut back their planned gas flows at short notice, beyond an allowed limit, on days of congestion).

What are ACER’s key findings and recommendations? 

Croatia 

After analysing the consultation document, ACER concludes that:

• The proposed methodology meets EU requirements on transparency, avoidance of cross-subsidisation, non-discrimination, volume risk and prevention of cross-border trade distortions.
• Compliance with the requirements on cost-reflectivity cannot be fully assessed, as it is unclear how the applied economic efficiency justification parameter affects the cost-reflectivity of the allowed revenue.
• The tariff methodologies for non-transmission services (the connection service and the 24 proposed non-standard services) lack sufficient details.

ACER recommends the Croatian NRA to:

• Ensure that the economic efficiency justification parameter does not compromise the principle of cost-reflectivity.
• Clarify how non-yearly bookings are handled in tariff setting.
• Align the tariff period with the Network Code’s requirements.

Finland

After analysing the consultation document, ACER concludes that: 

• The proposed methodology meets EU requirements on non-discrimination, volume risk and prevention of cross-border trade distortions.
• It partially meets the transparency requirements.
• Compliance with the requirements on cost-reflectivity and avoidance of cross-subsidisation cannot be fully assessed, mainly due to a lack of clarity on the effects of the market merger.
• The proposed connection capacity charge does not meet commodity charge criteria due to multiple factors, including its partial application to non-system user entities (e.g. distribution operators and their end-users).

ACER recommends the Finnish TSO to:

• Reconsider the new connection capacity charge to ensure it meets commodity charge criteria.
• Categorise the Balticconnector underutilisation fee as a balancing service, since it falls within the scope of the Network Code on Gas Balancing.

What are the next steps?

ACER encourages the Croatian NRA and the Finnish TSO to take these recommendations into account before adopting the final tariff methodologies.

See all ACER reports on national tariff consultation documents.