ACER Opinion 02-2026 on ENTSOG's Winter Supply Outlook 2025/26

No 02/2026

OPINION

on the ENTSOG Winter Supply Outlook 2025/26

11 February 2026

A C E R O P I N I O N N O 0 2 / 2 0 2 6

Executive summary

1 The EU’s provisional agreement on stepwise phasing out Russian gas imports – reached by the Council and the European Parliament – marks a strategic shift towards a European energy system that is more secure and independent from Russia. In this context, ENTSOG’s Winter Supply Outlook 2025/26 provides an updated view of Europe’s infrastructure readiness to manage gas flows for the coming winter season. Despite the storage levels starting this winter at 83% (943 TWh), lower than the previous year (94%, 1082 TWh), ENTSOG’s reference scenario indicates that the EU gas infrastructure can distribute gas effectively while maintaining storage above 30% by the end of winter, even in case of full disruption of the remaining Russian pipeline supply via TurkStream.

2 ACER welcomes ENTSOG’s comprehensive stress-testing of the gas infrastructure and the inclusion of new facilities and updated maintenance patterns. Regarding supply assumptions, ACER appreciates the explicit integration of the Russian gas phase-out. However, ACER recommends refining the liquefied natural gas (LNG) modelling approach. In particular, instead of capping the LNG supply at historical levels, the maximum LNG supply could be based on the available regasification capacity and the global pool of destination-free LNG cargoes that could be redirected to Europe in periods of high-demand. This, in turn, requires more granular supply modelling, including the dispatch order of LNG cargos and their interaction with demand-side response.

3 ACER also suggests that looking ahead the methodology should evolve to complement infrastructure stress-testing with realistic cross-sectoral demand projections and credible supplymolecule adequacy assessments, while providing greater transparency on flows at gas entry points. This reflects the legal requirement for supply outlooks as well as geopolitical developments which have an impact on EU’s supply risks. As Russian imports are phased out entirely – by early 2026 (LNG) and autumn 2027 (pipeline gas) – the EU’s supply risks will increasingly depend on global LNG market dynamics rather than on the internal gas infrastructure bottlenecks, which tend to occur only under extreme conditions, such as a cold winter combined with a major supply disruption.

4 The rapid pace of geopolitical change and market development calls for continuous gas supply adequacy monitoring to ensure that the EU’s gas system remains resilient throughout the transition to full independence from Russian gas. A C E R O P I N I O N N O 0 2 / 2 0 2 6

1. Background

5 On 9 October 2025, the European Network of Transmission System Operators for Gas (ENTSOG) adopted its Winter Supply Outlook 2025/26 pursuant to Article 26(3)(g) of Regulation (EU) 2024/1789. Under Article 4(3)(b) of Regulation (EU) 2019/942, ACER may issue an opinion on ENTSOG’s winter and summer supply outlooks, taking into account the objectives of nondiscrimination, effective competition and the proper and secure functioning of the internal market for natural gas.

6 To date, the outlooks have primarily focussed on testing the ability of the European gas infrastructure to cope with different fixed supply, demand and disruption scenarios. While supply adequacy analysis is less in the focus. In its previous opinion (No 06/2025), ACER advocated a more market-oriented approach to modelling liquefied natural gas (LNG) supply and gas demand response. Considering the new Outlook, this Opinion reiterates ACER’s past recommendations that have not yet been implemented by ENTSOG.

7 This Opinion concerns the Winter Supply Outlook 2025/26 (the Outlook) and is issued pursuant to Article 4(3)(b) of Regulation (EU) 2019/942 and Article 26(3)(g) of Regulation (EU) 2024/1789. It is addressed to ENTSOG.

2. Procedure

8 ACER’s Gas Working Group provided its advice on 14 January 2026.

3. Summary of the Outlook

10 The Outlook assesses the ability of European gas infrastructure to cope with the upcoming winter season under different scenarios. Although storage levels on 1 October 2025 were lower than last year – 83% (943 TWh) compared to 94% (1082 TWh) – the reference supply-demand scenario indicates that the infrastructure can distribute gas effectively while maintaining storage levels above 30% at the end of the winter season (31 March 2026), even in the event of a full disruption of TurkStream (Russian) pipeline supply.

11 In terms of the applied methodology, the current Outlook does not introduce major methodological changes or new modelling assumptions to the reference scenario compared with the previous edition.

4. ACER’s assessment

12 Regulation 2024/1789 requires ENTSOG to adopt seasonal outlooks. Article 26(3)(g) explicitly refers to supply outlooks. However, the Outlook does not provide a fully developed assessment of the gas supply side. A C E R O P I N I O N N O 0 2 / 2 0 2 6

13 Implementing ACER’s recommendations presented below would allow for a more comprehensive consideration of both gas supply and demand dynamics in the seasonal outlooks.

14 Infrastructure: ACER welcomes ENTSOG’s comprehensive testing of gas infrastructure under a wide range of cold winter demand scenarios, supply disruptions, and Europipe II fault. Continuous modelling updates, including newly commissioned facilities and infrastructure maintenance plans, are also well appreciated.

15 The assumption of international cooperation further strengthens the optimised use of the existing infrastructure, while cooperation among EU Member States typically becomes relevant only in emergency situations. Greater transparency would be achieved by explaining the impact of this assumption on the results, e.g. by indicating at which stage cooperation among the EU Member States becomes a necessity to ensure that supply can meet demand in Europe at each entry point.

16 ACER recommends ensuring greater transparency in the assumptions underlying the free-flow modelling approach, e.g. by showing regional dependency on gas entry points of the European gas infrastructure.

17 Demand: The reference winter gas demand volume is based on a TSO estimate, which is slightly higher compared to last winter (+4%).

18 ACER recommends using more realistic reference demand assumptions – reflecting the expected decline in demand and considering cross-sectoral energy trends. Recently, the gas demand has shown a declining trend year on year. Looking ahead, the electricity sector currently accounts for roughly one-third of the EU gas demand, and this share is expected to decline moderately by 2030 due to increased renewable deployment . ENTSO-E also publishes seasonal assessments of gas needs for power generation, which could support more coherent reference scenario building.

19 Supply: ACER welcomes the Outlook’s alignment with the phase-out roadmap of Russian gas supply and its modelling of Russian pipeline deliveries through TurkStream either as a last-resort source or as fully disrupted.

20 The sharp reduction in Russian supply since 2022 has been largely offset by increased LNG imports, which now cover roughly 40% of EU gas demand . The United States delivers the highest volumes of LNG to the EU, accounting for 60% of LNG imports in the third quarter of 2025 and resulting in a strong dependency for the EU. ENTSOG highlights access to adequate LNG supply as a key factor for European gas security. The Outlook’s `low-LNG supply` sensitivity analysis shows that insufficient LNG imports could lead to storage depletion by the end of winter, potentially requiring demand response measures to avoid shortfalls. This underscores the need A C E R O P I N I O N N O 0 2 / 2 0 2 6 to secure adequate LNG volumes, particularly under cold winter conditions or in the event of a major supply disruption.

21 ACER recommends capping LNG supply at a level of (i) the European LNG terminal regasification and network capacities (the high-LNG scenario); and (ii) global LNG volumes under 6 7 destination-free contracts , in addition to fixed-destination EU contracts . ACER recommends that this approach is considered as an input to a more refined supply-modelling methodology, as it reflects the global liquidity of LNG and the ability to redirect cargos to the highest-value market.

22 Market: The LNG supply dependency could be examined by only capping the EU LNG imports at the level of available regasification infrastructure capacity (the high-LNG scenario). Modelling results under this setup would indicate the maximum volumes of LNG that can be utilised. These volumes can then be analysed from a supply-adequacy perspective by comparing them with destination-free LNG volumes available on the global LNG market and with overall technical LNG availability, while also accounting for potential operational constraints, e.g. adverse sea conditions, that may delay LNG cargos.

23 Removing the fixed LNG supply scenarios (low, reference, high) and allowing the global LNG supply to respond to the scenario conditions (e.g. higher demand due to cold winter) would render the analysis more realistic. This change would allow the Outlook to focus on potential supply adequacy risks under extreme scenarios (stress test) such as cold winters and/or pipeline disruptions.

24 ACER recommends simulating how the gas market would behave under various modelled scenarios, e.g., by ordering gas supply routes and volumes by their typical dispatch merit order.

25 In practice, LNG is usually more expensive. Thus, it would be added to the supply mix after cheaper pipeline gas. Within each type of supply, additional volumes would cost more, reflecting how prices have behaved in the past . When supply becomes tight, demand response to increasing marginal sourcing prices could also be included as a possible reaction.

26 The current omission of demand response leads to an early demand curtailment to keep demand and supply balanced under extreme circumstances. This effect is further amplified by the application of curtailment prior to the use of strategic reserves in Europe, as about 11% of the gas storage in Europe remains unavailable in the Outlook.

27 ACER recommends reviewing the methodology underpinning the outlooks, considering experience accumulated so far and ACER`s recommendations. As EU gas infrastructure has matured and enabled substantial shifts in gas flows from east to west, more attention should be placed on global LNG supply availability for Europe. Complementing infrastructure stress testing with assessments of gas-molecule adequacy would address an emerging challenge: potential supply shortages due to the current market and geopolitical environment.

5. Conclusions

28 ACER welcomes ENTSOG’s continued monitoring of the EU gas infrastructure readiness for the coming season, under both reference and extreme conditions (cold winter, supply disruption). A C E R O P I N I O N N O 0 2 / 2 0 2 6

29 The Outlook is broadly consistent with the objectives of non-discrimination, effective competition, and the proper and secure functioning of the internal natural gas market. ACER urges ENTSOG to implement the recommendations outlined in Section 4 of this Opinion. This Opinion is addressed to ENTSOG. Done at Ljubljana, on 11 February 2026. — SIGNED — V. ZULEGER, ACER Director ad interim