text: https://www.entsog.eu/sites/defa ult/files/2023-10/SO0052-23_Winter%20Supply%20Outlook%202023- 24%20with%20Summer%202024%20Overview.pdf

text: Opinion No 11/2023

text: ENTSOG WSO 2023/24 states that “The Reference Winter demand (from 1 October 2023 to 31 March 2024) is based on TSOs’ estimates and is provided on a monthly granularity level.” ENTSOG WSO 2023/24 sta tes that “The demand for the Cold Winter is ba sed on demand a ssumptions considered in ENTSOG’s Union-wide Security of Supply Simulation Report 2021, i.e., the historical highest winter demand since the winter 2009/10 on country level.” The “Cold Winter” demand values were a lso updated by ENTSOG to consider the la test market conversions from L-ga s to H-gas in Germany, Fra nce, a nd Belgium. https://eur-lex.europa .eu/lega l-content/EN/TXT/PDF/?uri=CELEX:32023R0706 Art. 7(1) of Regula tion

text: (EU) 2017/1938

text: Three different cases of LNG a vailability have been considered: reference LNG, low LNG a nd maximum LNG. In the WSO 2023/24 this sensitivity is ca lled “ma ximum stora ge ta rget”.

text: Opinion No 11/2023

text: st 11 a. The EU storage level on 1 October 2023 (ca. 1,100 TWh , 96% of overall storage st capacity) registered the highest stored amount in recent years. On 1 October 2023,

text: https://www.acer.europa.eu/Official_documents/Acts_of_the_Agency/Opinions/Opinions/ACER_Opinion_07- 2022_on_ENTSOG%E2%80%99s_Winter_Supply_Outlook_2022-2023.pdf https://www.entsog.eu/sites/default/files/2023-10/SO0053-23_Winter%20Supply%20Review%202022-23.pdf On 8 October 2023 the Balticonnector between Estonia a nd Finla nd, with a ca pacity of ca . 2.6 bcma, was decla red out of service due to a leak caused by a damaged pipe in the sea , which, a t the time of drafting this Opinion, is currently under investiga tion. This tota l includes ca . 7 TWh of ga s in stora ge in the UK a nd ca . 4 TWh of ga s in stora ge in Serbia .

text: Opinion No 11/2023

text: st The United Kingdom rea ched 71% on 1 October 2023.

text: Article 6

text: (a ) of Regula tion

text: (EU) 2022/1032

text: https://eur-lex.europa .eu/lega lcontent/EN/TXT/PDF/?uri=CELEX:32022R2301

text: Opinion No 11/2023

text: 15 (15)

text: Regulation (EU) 2022/1032

text: and

text: Regulation (EU) 2022/2301

text: set specific country storage filling trajectories for the preparation of winter 2022/23 and winter 2023/24. The Regulations require that gas storages must be filled up to at least 80% of their capacity st before 1 of November 2022 and at 90% for the following winter periods.

text: https://eur-lex.europa .eu/lega l-content/EN/TXT/PDF/?uri=CELEX:32022R1032 https://eur-lex.europa .eu/lega l-content/EN/TXT/PDF/?uri=CELEX:32022R2301 Cf.

text: Article 6

text: b. https://www.acer.europa.eu/news-and-events/news/acer-publishes-consultancy-study-impact-eu-and-nationalga s-stora ge-regula tions https://www.a cer.europa .eu/Publica tions/ACER_MMR_2023_Ga s_ma rket_trends_price_drivers.pdf

text: Opinion No 11/2023

text: Seven Member States appointed a la st resort entity (other than market participants) whose role was primarily to procure and store gas quantities where the storage filling would be below the targeted levels, a nd the commercial use of the stora ges a nd the other measures in pla ce would prove not to be sufficient. In some of these countries, however, there was no need to trigger the la st resort filling service, or the volumes established were too small to effectively impa ct the ga s ma rket. Ta ble 2, p.20. Cf.

text: Article 6

text: b.

text: Opinion No 11/2023

text: WSO 2023/24, p.50. https://www.bruegel.org/a na lysis/europea n-union-rea dy-2023-24-winter-ga s-sea son According to the European Commission, “after the first three rounds, more than 44 bcm of ga s demand from European companies have been a ggregated a nd more than 52 bcm have been offered by international suppliers. After seeking the most competitive offers, Aggrega teEU has matched a total amount o f 34,78 bcm of ga s to cover Europea n dema nd.”. Source: https://energy.ec.europa .eu/topics/energy-security/eu-energy-pla tform_en ENTSOG Winter 2022/2023 Supply Review, p.20-24. Norwa y, Algeria a nd Ca spia n ga s. https://energy.ec.europa .eu/da ta -a nd-a na lysis/ma rket-a na lysis_en WSO 2023/24, p. 8 According to ARGUS Media, global liquefaction capacity is expected to increase by 1 TWh/y between October 2023 a nd Ma rch 2024, la rgely driven be more liquefa ction ca pacity a vaila ble from the Atla ntic ba sin: https://view.argusmedia.com/rs/584-BUW-606/images/ENG-Whitepaper-winter-2023-24-ma rket-preview.pdf ACER-CEER a nnua l report monitoring the interna l ga s ma rket in 2022 a nd 2023, p. 21 -22: https://www.a cer.europa .eu/Publica tions/ACER_MMR_2023_Ga s_ma rket_trends_price_drivers.pdf

text: Opinion No 11/2023

text: https://timera -energy.com/crisis-over-europea n-ga s-ma rket-winter-outlook/ WSO 2023/24, p.14. WSO 2023/24, p.8. LNG supplies represented in winter 2022/23, 35.5% of EU ga s imports (Winter Review 2022/23, p. 21). https://www.reuters.com/business/energy/ukraine-has-no-plans-talk-with-russia-gas-transit-contract-renewalvoa -2023-08-17/

text: Opinion No 11/2023

text: According to Article 11(7) of Regula tion

text: (EU) 2017/1938

text: . I.e. the a mount of ga s needed to ensure a dequacy on the electrical power system considering the worst winter scena rios. ENTSO-E Winter Outlook 2023/24, p. 27-28: https://eepublicdownloads.entsoe.eu/clean-documents/sdcdocuments/sea sona l/WOR2023/1_Winter%20Outlook%202023 -2024_Report.pdf

text: Opinion No 11/2023

text: Council Regula tion

text: (EU) 2022/1369

text: of 5 August 2022 on coordinated demand-reduction measures for gas: https://eur-lex.europa .eu/lega l-content/EN/TXT/?uri=CELEX%3A32022R1369 The Union a lert ca n be declared by the Council, a cting on a proposal from the European Commission in case of a substantial risk of a severe ga s shortage or an exceptionally high ga s demand, or if five or more MSs have decla red an a lert at national level requesting the Commission to do so. This Regula tion foresees derogations for Member Sta tes depending on the level of interconnection a nd other a spects. Possible mea sures include reducing ga s consumed in the electricity sector, measures to encourage fuel switch in industry, national a wareness ra ising campaigns, targeted obliga tions to reduce heating a nd cooling a nd marketba sed measures such a s auctioning between companies. Measures that do not affect protected customers such as households and essential services for the functioning of society like critical entities, healthcare and defence should be a priority. Council Regula tion

text: (EU) 2023/706

text: of 30 Ma rch 2023 a mending

text: Regulation (EU) 2022/1369

text: a s regards prolonging the demand-reduction period for demand-reduction measures for ga s and reinforcing the reporting and monitoring of their implementation: https://eur-lex.europa.eu/legalcontent/EN/TXT/?uri=CELEX%3A32023R0706&qid=1697820043435

text: Opinion No 11/2023

text: The ACER-CEER annual report monitoring the internal ga s market in 2022 a nd 2023 suggests that future prices for ga s delivery in winter 2023/24 remain higher tha n the a verage of the five preceding winters (excluding 2021/22), thus indica ting tha t the ma rket still sees supply risks for winter sea son 2023/24, p. 14: https://www.a cer.europa .eu/Publica tions/ACER_MMR_2023_Ga s_ma rket_trends_price_drivers.pdf The IEA in its Medium-Term Gas Report 2023 expects that over half of the European industrial gas demand lost in 2022 will not be recovered by 2026, due to a ctivity downsize in EU, efficient investments made or substitution of natural ga s with other fuels : https://iea.blob.core.windows.net/assets/f2cf36a9-fd9b-44e6-8659c342027ff9a c/Medium -TermGa sReport2023-IncludingtheGa sMa rketReportQ4-2023.pdf WSO 2023/24, p.9-12. In comparison to winter 2023/24 which was quite mild a nd the -15% reduction targets were a pplied, the WSO 2023/24 seasonal ga s demand projection increases by +15.6% for a “Reference winter” a nd 25% for a “Cold winter”; the peak demand increases by +50% for a “Reference winter” and +56.6% for a “Cold winter”, respectively. The highest yearly consumption of natural ga s wa s recorded in 2010 (4,688 TWh) a nd ga s consumption has been decreasing since then. The highest winter demand was recorded during the winter 2009/10 (3,513 TWh vs ca . 3,000 TWh of WSO 2023/24). The highest peak demand consumption and 2-weeks peak demand consumption were recorded during the winter 2011/12 with respectively 29,452 GWh/d (vs ca 33,686 GWh/d of WSO 2023/24 "Reference Winter” high demand) and 27,644 GWh/d (vs ca 27,181 GWh/d of WSO 2023/24 "Reference Winter” high dema nd). Source: ACER a na lysis ba sed on Eurosta t a nd ENTSOG da ta . ACER a lso notes that a scenario based on demand reduction targets was a t lea st considered a s sensitivity in ENTSOG WSO 2022/23 while it wa s disrega rded for WSO 2023/24. ENTSO-E Winter Outlook 2023/24, p. 27-28: https://eepublicdownloads.entsoe.eu/clean-documents/sdcdocuments/sea sona l/WOR2023/1_Winter%20Outlook%202023 -2024_Report.pdf

text: Opinion No 11/2023

text: ENTSO-E Winter Outlook 2023/24 considers a n energy sa vings scenario which aim at reflecting the energy sa ving measures foreseen by the European Council Regulation 2022/1854, under

text: Article 3

text: (-10% of total monthly gross electricity consumption) a nd

text: Article 4

text: (a t lea st -5% over the identified pea k hours). WSO 2023/24, p. 8: Brunsbüttel Hafen and Stade FSRUs in Germany, Musel LNG terminal in Spa in and Le Ha vre FSRU in Fra nce. Concerning Musel LNG termina l, see a lso Annex III.

text: Opinion No 11/2023

text: https://a cer.europa .eu/Publica tions/ACER_10_Ga s_Congestion_Report.pdf https://a cer.europa .eu/Publica tions/ACER_Specia l_Report_Congestion2023.pdf https://ga sda shboa rd.entsog.eu/ 54 https://app.powerbi.com/view?r=eyJrIjoiY2NhNzQ3ODctZmI2ZC00MzAzLTk1ZWEtZWIxYmMzZGEyMTk xIiwidCI6IjgxMDU4NGZkLTY5ZjktNDEzNy1hNmExLWMwZTMzMjgwYjE1YyIsImMiOjh9

text: Article 13

text: . For stora ges, AGSI pla tform https://agsi.gie.eu/. For LNG termina ls, ALSI pla tform https://a lsi.gie.eu/ While the na tural ga s demand is a n input to the WSO a nd it is considered inelastic in the simulations, winter 2022/23 showed that part of the demand reduction, especially in the industrial sector, was triggered by extreme high prices. Such considera tions should be included when defining the dema nd input. ACER Opinion No 11/2021 on ENTSOG Winter Supply Outlook 2021/2022, p.8.

text: Opinion No 11/2023

text: For exa mple, the ALSI platform publishes capacity forecast data for the upcoming 6 months which could be considered when building the reference LNG supply scena rio: https://a lsi.gie.eu/ca pa city-foreca st

text: Opinion No 11/2023

text: See section 3.4 of the Opinion, on ma in risk fa ctors for upcoming winter.

text: Opinion No 11/2023 also during the remaining winter season and national competent authorities to monitor and favour a withdrawal pattern that would safeguard the continuity of gas deliveries throughout the whole winter. This Opinion is addressed to ENTSOG. Done at Ljubljana, on 14 December 2023.

text: Opinion No 11/2023

text: st 60

text: Source: AGSI+ pla tform (https://agsi.gie.eu/), 1.10.2023 data, pla tform a ccessed on 24.11.2023. According to the AGSI+ pla tform the da ta for Ita ly wa s ma rked a s “estima ted” a t the time of a ccess.

text: Opinion No 11/2023

text: Storage filling data based on AGSI+ data; storage targets based on 1 of November target as defined in

text: Regulation (EU) 2022/2301

identifier: ACER Opinion No 11/2023

title: ACER Opinion 11-2023 on ENTSOG’s Winter Supply Outlook 2023-2024

text: PUBLIC

text: OPINION No 11/2023 OF THE EUROPEAN UNION AGENCY FOR THE COOPERATION OF ENERGY REGULATORS of 14 December 2023 on ENTSOG’s Winter Supply Outlook 2023/2024

text: THE EUROPEAN UNION AGENCY FOR THE COOPERATION OF ENERGY REGULATORS, Having regard to

text: Regulation (EU) 2019/942

text: of the European Parliament and of the Council of 5 June 2019 establishing a European Union Agency for the Cooperation of Energy Regulators (‘ACER’), and, in particular,

text: Article 4(3)

text: (b) thereof, Having regard to

text: Regulation (EC) No 715/2009

text: of the European Parliament and of the Council of 13 July 2009 on conditions for access to the natural gas transmission networks and repealing

text: Regulation (EC) No 1775/2005

text: , and, in particular, Articles

text: and

text: thereof, Having regard to the outcome of the consultation with ACER’s Gas Working Group, Having regard to the favourable opinion of the Board of Regulators of 13 December 2023, delivered pursuant to

text: Article 22(5) of Regulation (EU) 2019/942

text: , Whereas:

text: 1. INTRODUCTION

text: (1) On 17 October 2023, the European Network of Transmission System Operators for Gas (‘ENTSOG’) published the Winter Supply Outlook 2023/2024 (‘WSO 2023/24’) pursuant to

text: Article 8(3)

text: (f) of

text: Regulation (EC) No 715/2009

text: , which also includes a preliminary outlook for the summer 2024. (2) Pursuant to

text: Article 4(3)

text: (b) of

text: Regulation (EU) 2019/942

text: , ACER may provide an Opinion to ENTSOG on, inter alia, relevant documents referred to in Article 8(3) of Regulation

text: 2. SUMMARY OF THE DOCUMENT

text: (3) In the WSO 2023/24, ENTSOG undertakes an assessment of the resilience of the European gas network for the upcoming winter (October 2023 to March 2024). ENTSOG’s analysis investigates the ability of the gas infrastructure to dispatch the necessary supply volumes to meet gas demand, and especially to deal with high demand situations, provided that gas supply is available. The Outlook is based on assumptions of gas supply potentials, on historical gas supplies during the last 5 years (or based on TSO information), and it looks into the possible evolution of gas supplies and underground gas storage (‘UGS’) utilisation levels during the upcoming winter withdrawal season. Based on these assumptions the WSO 2023/24 assesses the readiness of the gas infrastructure for the winter season.

text: (4) ENTSOG simulates the ability of the gas infrastructure system to ensure supply and 2 3 demand adequacy under a “Reference winter” and a “Cold winter” . The “Cold Winter” assessment is complemented by a sensitivity which considers the voluntary target for Member States to reduce their natural gas consumption by 15% . The WSO 2023/24 also simulates “stress tests” of the gas infrastructure under two cases of high demand linked to cold weather, namely under a “Peak day” and a “2-week cold spell”.

text: (5) On the supply side, in line with its obligation under the EU Security of gas supply Regulation , ENTSOG has undertaken an assessment of a full disruption of a single supply source, specifically, for WSO 2023/24, Russian piped gas. Furthermore, ENTSOG, for the first time has analysed how different levels of LNG availability could impact the risk of demand curtailment and the amount of gas remaining in storage at the end of the winter.

text: (6) Compared to the previous outlooks, this WSO 2023/24 also includes a sensitivity analysis to check if the gas infrastructure system is sufficiently flexible to achieve storage levels exceeding 30% at the end of the withdrawal period .

text: (7) In line with its Summer Supply Outlook 2023 and ACER recommendation on WSO 2022/23 , ENTSOG extended the analysis by also including an overview of summer 2024, thus covering the full gas year from October 2023 to September 2024.

text: (8) On 17 October 2023, ENTSOG also published a report on the European gas supply and demand for the past Winter 2022/23 , which aims to provide an ex-post analysis of the gas demand and supply in the previous seasons. The report was published on a voluntary basis along with the WSO 2023/24.

text: 3. ASSESSMENT OF THE DOCUMENT

text: (9) ACER welcomes the timely publication of the WSO 2023/24 and accompanying documents ahead of the winter season. ACER appreciates the analysis of the historical gas supply, demand patterns and use of storages, as well as of the possible evolution of storage levels for the upcoming winter and summer resulting from the assumptions and simulations contained in the Outlook.

text: (10) ACER welcomes the inclusion of additional sensitivity analyses of the level of LNG potential imports reaching Europe, as the availability of sufficient LNG volumes is one of the main risk factors for the upcoming winter and summer seasons.

text: (11) ACER welcomes the inclusion of a sensitivity analysis on the maximum level of gas in storage that could be reached at the end of the winter period.

text: (12) ACER finds the inclusion of a section on the Balticonnector pipeline disruption relevant (Chapter 6).

text: 3.1. ENTSOG main findings and analytical framework

text: (13) ACER takes note and underlines the importance of the following main findings contained in the WSO 2023/24:

text: all Members States had already reached the 90% filling target objective set out in the EU gas storage regulation .

text: b. The European gas infrastructure, including projects to be commissioned over the upcoming winter, offers sufficient flexibility to dispatch the necessary supply volumes to meet demand in Europe and reach “safe” storage levels, assuming that there is efficient cooperation among the different Member States and that sufficient gas reaches the EU.

text: c. However, under specific scenarios of high demand, some possible demand curtailments are identified by ENTSOG, along with the low level of gas in stock at the end of the winter and some infrastructure bottlenecks emerging within Europe. Such stressful situation is further aggravated in case of low LNG availability and/or in case of a full disruption of Russian gas supply.

text: d. Additional storage flexibility could be achieved by using Ukrainian storage facilities, provided that those volumes can be injected and subsequently withdrawn during the winter season and if market participants are willing to make use of it.

text: e. According to the WSO 2023/24 results, at least 46% of working gas volume would be needed at the end of the winter to meet the summer demand and to reach the 90% st target in all Members States on 1 November 2024. Such level would not be achieved in case of a “Reference Winter” with low LNG imports or in case of a “Cold Winter” (unless a -15% demand reduction is applied).

text: f. A sensitivity conducted on the Balticconector disruption shows that its prolonged unavailability (i.e. through the whole winter) limits the possibility for Finland to cooperate with its neighbouring countries but it does not pose a significant risk to the security of gas supply in the region nor to the possibility of adequately filling the storages.

text: (14) ACER takes note of the following conclusions contained in the WSO 2022/23:

text: a. High storage levels, the current gas infrastructure system and new projects to be commissioned, enhanced cooperation and additional LNG import capacities can efficiently reduce the dependence on Russian gas supply, and partially mitigate the risk of demand curtailment in case of a full and prolonged Russian pipeline disruption.

text: b. Without demand reduction, most countries would be exposed to significant risk of demand curtailment in case of a “Cold winter”.

text: c. However, demand reduction alone might not be enough. Ensuring sufficient LNG imports are essential to prevent demand curtailments and to ensure adequate filling of gas storages.

text: d. Some infrastructure bottlenecks within EU remain. Between France and Spain, between Poland and Lithuania, and between Southern -East Europe and Central Europe.

text: e. Early and significant withdrawal of gas from storages will result in low storage levels at the end of the winter season, having a negative impact on the flexibility of the gas system and on the preparedness for the next winter season 2023/24.

text: 3.2. Gas storage filling levels in view of EU Gas Storage Regulation

text: (16) ACER welcomes that the EU collective 90% storage filling rate objective was already st achieved in mid-August, nearly 2-months ahead of the 1 of November deadline. Where possible, NRAs have checked the accuracy of storage filling levels reported in ENTSOG’s Winter Outlook.

text: Regulation (EU) 2022/1032

text: states that “Member States shall take all necessary measures […] to meet the filling targets […]” and introduces a set of measures which each Members States could adopt to reach those targets. The recently published ACER consultancy study “On the impact of EU and national gas storage regulations” shows that the measures implemented in the Members States effectively helped to reach the storage filling levels at national and European level. Measures like financial incentives for storage users, stockholding obligations, institution of last resort storage entities and use-it-or-lose-it mechanisms, allowed to reach an adequate level of preparedness, despite the discouraging market signals. The study also shows that such measures came at a cost, and that gas prices moved upward also due to the strong competition among countries to refill their storages before the regulatory filling target dates .

text: (18) Also based on the difficulties and risks observed in implementing these measures, the ACER consultancy study emphasizes the need to further improve the transparency and verifiability of the measures as well as the need to strengthen coordination between Member States with and without storages to avoid Member States without gas storages

text: to face constraints in accessing gas sources. The ACER consultancy study also underlines the need for making the last resort mechanism more efficient, by ensuring carefully planning of the conditions when the last resort entity acts, the volume requirements, and by introducing risk reduction mechanisms which can interact with existing market rules and do not increase wholesale prices (e.g., price hedging by the designated entity).

text: (19) The study will be followed up by a Council of European Energy Regulators (CEER) study which will review the agreements and the burden -sharing mechanism between Member States that have storage facilities and the ones that do not have them. The followup study will identity best practices and propose recommendations to design storage filling obligations with the aim to enhance their effectiveness and efficiency in the future.

text: (20) ACER highlights the critical importance of counting on adequate storage levels at the end of the winter season to cover still possible high demand or system stress situations. ACER concurs with ENTSOG that early and significant withdrawal from storages has a negative impact on the flexibility of the gas system and can increase the exposure to supply risks towards the end of the winter. ACER takes note of ENTSOG’s view that a st 46% aspirational target for storage filling level on 1 April 2024 will be needed to ensure preparedness for the upcoming winter 2024/25.

text: (21) As the actual use of imports and/or storage is eventually determined by market participants, ACER expects storage users to prudently withdraw gas from storage during this winter. Furthermore, ACER calls on national competent authorities to monitor and take measures, starting with market-based incentives and measures, to favour a gas withdrawal pattern that enables safeguarding the continuity of gas deliveries during the next winter.

text: (22) ACER understands that the WSO 2023/24 considers the strategic reserves set out by national legislation, allowing for “more realistic” simulations. The ACER consultancy study “on the impact of EU and national gas storage regulations” shows that in some countries the introduction of strategic reserves was a measure implemented following the adoption of

text: Regulation (EU) 2022/1032

text: . In other countries the use of strategic reserves was already existing but was amended after the adoption of

text: Regulation (EU) 2022/1032

text: (23) Additionally, to the role of storages, ENTSOG also considers the role of tanks from LNG regasification terminals which would offer additional short-term flexibility to cover the peak-demand and short-term cold spells .

text: 3.3. The role of LNG and other supply sources to replace Russian piped gas

text: (24) Since the start of the Russian aggression against Ukraine, Europe has succeeded in reducing its dependency from Russian gas. Despite the significant reduction in Russian imports, while some countries are now completely independent, in 2023 some other countries continued to rely on Russian gas imports, both through pipelines and LNG .

text: (25) In April 2022, the European Commission launched the EU Energy Platform, AggregateEU, to support demand aggregation and joint purchase of gas. The creation of this platform aimed at facilitating the reduction of European dependence from Russian gas.

text: (26) LNG has been the main gas source to replace significant gas imports from Russia and this is likely to continue in the future. Increased high LNG imports (822 TWh in winter 2022/23 vs 639 TWh in winter 2021/22) were necessary to partially offset the decline in Russian gas pipeline imports from Russia, as other gas pipeline sources have limited flexibility to increase supply. With the majority of LNG cargos not tied to long-term contracts, these incremental LNG volumes remain subject to global price fluctuations. The European Commission quarterly gas market reports show that for most of the first quarter of 2023, as well as for most of 2022, Europe offered price premiums compared to Asia. On one hand the upward pressure on prices might be lower during winter 2023/24 thanks to the availability of more LNG regasification and more liquefaction capacities , as well as, thanks to the alleviation of some cross-border congestions within Europe . On the other hand, both the European gas and LNG markets are still expected to be characterised by volatility across this winter, and likely the next one as well, with

text: price risk skewed to the upside , especially in case of unforeseen events (see section 3.4 on risks factors for this winter).

text: (27) The WSO 2023/24 assumes that LNG imports could be increased up to the maximum of current EU LNG import regasification capacities plus additional LNG import capacities expected to come online soon . Although the EU regasification terminals have in general sufficient spare regasification capacity, there are variations in the available spare capacity across Member State and LNG terminals. Additionally, there might be scheduling constraints for LNG cargos deliveries in some LNG terminals this winter. The arrival of LNG cargoes to EU LNG terminals depends on commercial decisions, as LNG market is global and spot LNG cargoes will be destined where demand offers the highest price . Besides available LNG regasification capacity, sufficient transmission capacities are necessary to make fully use of the LNG import potential across Europe.

text: 3.4. Risks factors for this winter

text: Main risk factors for upcoming winter

text: (28) ACER notes the continuation of risk factors present since the start of the Russian aggression against Ukraine for the upcoming winter season:

text: a. High uncertainty about the availability of Russian gas supply, in particular concerning LNG from Russia (today still counting 15%-19% of overall EU LNG imports), and about the flows through Ukraine, also beyond 2024 due to the expiration and possible non-renewal of the transit contract between the two countries ;

text: b. Limited additional gas volumes from other major sources of gas pipeline imports to go significantly beyond the contracted/booked volumes;

text: c. Existence of limited cross-border capacities in the EU to accommodate new gas flows from the West and LNG terminals which previously came from the East;

text: d. Increase in Asian’s gas demand due to economic recovery or unavailability of other sources such as hydro or nuclear, possibly driving upwards global LNG demand and prices, and impacting the price levels and availability of LNG imports to the EU;

text: e. Operational incidents, outages or accidents in major supply routes or in upstream production sites limiting availability of gas supply, in particular LNG, to the EU market;

text: f. A colder than usual winter, driving up gas demand;

text: g. Lack of implementation of gas demand reduction targets; and

text: h. A low storage filling level at the end of the winter, limiting the deliverability of storages and complicating the replenishment of storages during summer 2024.

text: (29) The materialisation of these risk factors may lead to supply scarcity which would firstly impact wholesale gas prices, leading to some demand reduction, in particular for industrial consumers. Forced gas demand reductions would come next and involuntary demand curtailment of non-essential gas consumers would be a last resort emergency measure.

text: (30) In addition, Member States may decide to prioritise the gas supply to certain critical gas-fired power plants over the gas supply to certain categories of protected customers, if the lack of gas supply to such critical gas-fired power plants either could result in severe damage to the functioning of the electricity system or would hamper the production and/or transportation of gas. In this sense, ENTSO-E’s Winter Outlook 2023/24 assesses 37 38 the critical gas volume for electricity generation in Europe , finding that the critical gas volume decreases approximately by 10% compared with winter 2022 /23, due to more favourable conditions such as higher nuclear availability in Europe and higher hydro availability, as well as due to a stagnant demand.

text: (31) This situation calls for continued vigilance with respect to gas supply situation and for monitoring the implementation of the EU gas demand reduction regulation.

text: WSO 2023/24 Supply Disruption Scenarios

text: (32) ACER finds adequate that the Outlook’s “reference case” reflects the currently reduced Russian imports limited to Ukraine and Turkstream routes to the EU. ACER welcomes that ENTSOG includes in its assessment a full disruption of the piped gas supply from Russia, investigating its potential impact on the storage filling level at the end of the winter and gas demand curtailment for the “Reference Winter” and “Cold Winter” scenarios.

text: (33) The WSO’s simulations show that storages cannot reach the 30% filling level at the end of the winter season in case of a “Cold Winter”, and that the European countries would face demand curtailment. Under a prolonged disruption of the pipeline supply from Russia, the assessment reveals insufficient LNG capacity as well as infrastructure bottlenecks between Southern Europe and Central Europe, which do not allow for better cooperation. Under high demand situations and disruption of Russian pipeline imports, the situation is aggravated, and the assessment under a “Cold Winter” shows also bottlenecks between Poland and Lithuania and between South -Eastern Europe with the rest of Europe.

text: (34) ACER agrees with ENTSOG that the full disruption of Russian gas is undoubtedly the main risk for the upcoming winter. However, this scenario could be aggravated by disruption scenarios for sources other than Russia, which are nevertheless less likely to occur (e.g., gas supplies from Algeria, prolonged disruption of Norwegian gas supplies via offshore pipeline such as Europipe, Norpipe, Zeepipe, Franpipe). Such additional extreme combined scenarios would provide useful insights regarding the readiness of the European gas infrastructure to deal with less likely but high impact disruption situations.

text: 3.5. Demand assumptions in view of EU Gas Demand Reduction

text: (35) On 5 August 2022, the European Union adopted a Regulation on a coordinated demandreduction measures for gas to increase the Union level of preparedness as regards gas supply disruptions, in view of a significant risk that a complete halt of Russian gas supplies may materialise soon. This regulation recommends a voluntary reduction of natural gas demand by at least 15% which may become mandatory by a declaration of a “Union alert” . Member States have flexibility in choosing the demand reduction measures . On 28 March 2023, Member States agreed to extend the voluntary 15% gas demand reduction target until March 2024 .

text: (36) ACER notes that the “Reference Winter” demand shows an increase of ca. 16% compared to the demand registered for the winter 2022/23 , while being lower than the average of the previous 5 years (-8% vs the average of winters 2017/18 - 2021/22). ACER

text: understands that the “Reference Winter” demand data was provided by TSOs on a monthly granularity level but it is not entirely clear if and how ENTSOG checks the TSOs demand projections and if they are consistent with the aggregated demand at EUlevel. In this regard, it is not clear if the TSO demand projections consider, for example, that sustained high levels of wholesale gas prices can and have eroded gas demand, in particular for energy-intensive industries . ACER also notes that the “Reference Winter” demand is calculated in a different way than the “Reference Summer” demand, with only the latter considering the 15% reduction.

text: (37) ACER finds the Outlook’s seasonal demand projection and the peak demand projections

text: in particular, too high , especially when compared to the historical demand evolution and the observed continuing decrease in gas demand.

text: (38) In ACER’s views, ENTSOG should have preferably used a “baseline scenario” of gas demand for the winter outlook built upon the European Union targets of reduction of gas demand, which would be consistent with the Union Regulation on coordinated demandreduction measures for gas .

text: (39) In addition, demand reduction measures in the power sector can have a relevant impact on the overall gas demand via reduced consumption of gas-fired power plants. In its Winter Outlook 2023/24 , ENTSO-E assesses that the amount of gas needed to ensure adequacy on the electrical power system (critical gas volume (CGV)) could be further decreased by 10% if energy saving measures to reduce total consump tion and peak

text: demand would be implemented . Such cross-sectoral insights should be reflected in the ENTSOG WSOs.

text: 3.6. Network topology

text: (40) ENTSOG periodically upgrades the topology of its network model based on capacities provided by TSOs to reflect the technical capacities that are available for the upcoming winter. The WSO 2023/24 topology includes four new LNG infrastructures but does not provide a complete list of all the infrastructures considered in the assessment.

text: (41) ACER welcomes that the WSO also considers non-EU countries in the WSO perimeter. In some cases, non-EU countries are considered through predefined exogenous input either assumed by ENTSOG (e.g., Serbia) or provided by the relevant TSO of the concerned country (e.g., Ukraine). ACER invites ENTSOG to seek ways to further cooperate with non-EU countries and with the Energy Community to extend, where possible, the geographical perimeter of the simulations to other relevant countries (e.g., Moldova and Ukraine).

text: (42) ENTSOG considered “enhanced capacities” as provided by some TSO, which would allow to maximise the flows in the case of disruption of full Russian pipeline supply. According to the TSOs, those capacities would increase interconnection capacities between Germany and Austria, Belgium, the Czech Republic, and the Netherlands, as well as between Spain and France, allowing central Europe to access more LNG imports. However, there is lack of transparency in the WSO on the actual capacity, the conditions under which those capacities could be made available and on the actual required investments.

text: (43) ACER encourages once again ENTSOG to provide more clarity in the Outlook on the timestamp of the network topology as well as to publish, together with all the main relevant data, the full list of capacities considered in the WSO 2023/24, thus also including the considered upcoming projects and the enhanced capacities.

text: 3.7. Maximisation of gas import and cross-border capacities

text: (44) The war in Ukraine is leading to a significant rerouting of gas across Europe, increasing supplies from West to East substituting traditional East-West flows. ENTSOG has identified transmission capacity limitations to move gas from West to East in case of disruption scenarios of Russian pipeline gas, which hamper some Central Eastern European countries to satisfy their gas demand and reach adequate level of storage filling targets at the end of the winter 2023/24 and in case of a full disruption of Russian gas. Part of such flow changes could be accommodated by TSOs re-allocating existing

text: transmission capacities to new expected flow patterns. ACER recommends ENTSOG to provide an update of such re-allocated capacities and to TSOs to maximise the availability of capacities to accommodate new flow configurations.

text: (45) As stated in the ACER report on “Congestion in the EU Gas Markets” and in the ACER special report on “Addressing congestion in North-West European gas markets” , ACER urges the affected TSOs to take appropriate and coordinated cross -border actions to maximise capacities and manage contractual and physical congestions, and it invites ENTSOG to publicly report on the actions undertaken by the affected TSOs and to specify how much additional capacity has been made available in this way.

text: 3.8. Monitoring tools of gas supply situation

text: (46) ACER praises once again ENTSOG for providing monitoring tools and initiatives beyond its legal tasks, which provide real value for monitoring the gas security of supply situation, such as the European gas flow dashboard , the Seasonal Supply Outlook Monitoring , and the support to Gas Coordination Group assessments. ACER notes that associations of storage and LNG facilities have implemented updated transparency platforms for LNG facilities and gas storage facilities as required by

text: Regulation (EU) 2022/2576

text: which include links to tariffs information for LNG and storage facilities. ACER encourages ENTSOG and Gas Infrastructure Europe (GIE) to continue making these useful monitoring tools operational and developing new functionalities at their own initiatives or based on the requests of stakeholders or authorities.

text: 3.9. Implementation of previous ACER recommendations

text: (47) ACER finds no reference in the Outlook as regards possible implementation of its previous recommendations on seasonal outlooks, namely consider using a scenario based on expected gas supply and booked capacities; consider levels of winter demand which better incorporates exogenous factors such as demand reduction targets , demand elasticity triggered by future gas prices or fuel switch behaviours (e.g. under peak demand situations some sectors might switch to other fuels than gas) . However, ACER firmly believes that improvement in the WSO assumptions and methodology would be instrumental to better identify potential risks (and remedies) to which Member States

text: would be exposed in case of a tight gas supply situation, triggering timely anticipatory measurements.

text: (48) ACER encourages ENTSOG to consider developing, in consultation with stakeholders, such methodological improvements for future Outlooks in order to improve the robustness of the Outlook’s assessments. ENTSOG should devote, as a matter of priority, more resources to improve, even further, the methodology for the security of gas supply and preparedness assessments,

text: HAS ADOPTED THIS OPINION:

text: 1. ACER is of the view that ENTSOG’ Winter Supply Outlook 2023/2024 contributes to the objectives of

text: Regulation (EU) 2019/942

text: and

text: Regulation (EC) No 715/2009

text: in terms of contributing to non-discrimination, effective competition, and the efficient and secure functioning of the internal natural gas market.

text: Scope of analysis and timely publication

text: 2. ACER welcomes ENTSOG’s timely publication of the Winter Supply Outlook 2023/2024. ACER appreciates that the scope and methodology of the Outlook has been expanded to consider the outage of major infrastructures, the Russian invasion of Ukraine and caused risks for imports to Europe, different level of LNG availability and the inclusion of a sensitivity on the maximum level of storages that could be reached at the end of the filling period.

text: Improvements to Winter Supply Outlook methodology

text: 3. ACER acknowledges ENTSOG’s efforts and additional analysis in the current winter supply outlook. However, ACER firmly believes that improvement in the WSO assumptions and methodology would be instrumental to better identify potential risks to which Member States would be exposed in case of a tight gas supply situation. ACER encourages ENTSOG to consider improving the WSO assumptions and methodology, in particular by including in the supply assumptions the expected gas supply and booked capacities rather than using a scenario only based on historical values, and to embed expected gas prices and gas price demand elasticity in the definition of the demand which is an exogenous input to the modelling.

text: 4. In the last years, both Winter Supply Outlook and the Summer Supply Outlook have become important reference documents for stakeholders. ACER recommends ENTSOG to proactively engage with stakeholders well in advance of the Supply Outlooks' preparation and to consult them on the proposed methodology to gain insights into expected improvements.

text: 5. ACER also highlights the importance of close cooperation between ENTSOG and ENTSO-E to ensure, where relevant, consistent assumptions and results in their respective seasonal assessments. ACER also encourages ENTSOG and ENTSO-E to align the timing of the publication of the respective Winter Supply Outlooks.

text: Gas demand projections and savings

text: 6. ENTSOG should have included a “baseline scenario” of gas demand for the winter outlook built upon the European Union targets for reduction of gas demand, which would be consistent with the Union Regulation on coordinated demand-reduction measures for gas.

text: Risks factors for this winter and upcoming injection season

text: 7. ACER agrees with ENTSOG that the simulated disruption of Russian gas is undoubtedly the main risk for the upcoming winter. However, this scenario could be aggravated by other source, which are nevertheless less likely to occur, yet not modelled in the Outlook. The presence of risk factors , given the continuity of the Russian war against Ukraine calls for continued vigilance with respect to the gas supply situation. ACER calls on ENTSOG and all actors to remain vigilant for the upcoming winter and to track closely these risk factors.

text: Transparency

text: 8. ACER urges ENTSOG to publish all the assumptions and decisions underling the input used in the WSO 2023/24. ENTSOG should collect and publish the assumptions used to define the enhanced capacities and to derive the demand data provided by the TSOs.

text: New infrastructure projects and maximisation of gas import and cross-border capacities

text: 9. ACER welcomes that new cross-border initiatives and new LNG regasification capacities have contributed to the security of supply of EU. It remains a priority that cross-border capacities ensure the preparedness of the EU gas infrastructure to transport gas supplies that reduce and replace Russian gas supplies. ACER invites TSOs to take appropriate and coordinated cross-border actions to maximise capacities and manage contractual and physical congestions.

text: Vigilance over EU storage filling levels

text: 10. ACER welcomes that the EU collective 90% storage filling rate objective was already achieved in August, and that storage filling levels have reached the 90% target in all st Member States well ahead 1 of November. Strengthened gas storage regulations and measures have played a role in the successful replenishment of storages.

text: 11. ACER highlights the critical importance of monitoring and keeping adequate storage levels towards the end of the winter season to cover for possible high demand or supply disruption situations. Early and significant withdrawal from storages results in low storage levels at the end of the winter season and increases the risk for the next replenishment season. Therefore, ACER expects storage users to prudently withdraw gas from storage

text: - SIGNED –

text: Fоr the Agency The Director

text: C. ZINGLERSEN

text: Annexes:

text: I: Storage filling levels per Member States on 1 October 2023

text: II: EU Storage filling levels on 1 November 2023 vs EU Regulation filling targets III: Incorrect or unclear information in ENTSOG’s Winter Outlook 202 3/2024

text: Annex I: Storage filling levels per Member States on 1 October 2023

text: Working gas Gas in volume storage Filling level of storage Country (TWh) (TWh) (%)

text: Austria 97.6 92.6 95 Belgium 9.1 8.4 92 Bulgaria 5.9 5.7 96 Croatia 4.8 4.6 97 Czech Republic 44.6 43.2 97 Denmark 9.8 9.0 92 France 134.4 126.2 94 Germany 254.1 244.1 96 Hungary 70.1 66.7 95 Italy 195.4 188.7 97 Latvia 22.6 20.9 92 Netherlands 142.4 137.1 96 Poland 37.5 37.3 100 Portugal 3.6 3.5 97 Romania 33.9 33.1 98 Slovakia 36.9 35.7 97 Spain 34.1 34.2 100 Sweden 0.1 0.1 95

text: EU 1136.8 1091.3 96

text: Annex II: EU Storage filling levels on 1 November 2023 vs EU Regulation filling targets.

text: Annex III: Incorrect or unclear information in ENTSOG’s Winter Outlook 2023 /2024

text: (1) In page 8, third paragraph of ENTSOG WSO 2023/24, it says: “The topology of the network model considers the existing European gas infrastructure, the firm technical capacities provided by TSOs, which include maintenance plans known as of September 2023 and new upcoming projects as of their respective expected start of commercial operations. For example: • Brunsbuettel Hafen and Stade FSRUs in Germany; • Musel LNG terminal in Spain; • Le Havre FSRU in France.”

text: CNMC notices that Musel LNG terminal, previously mothballed, entered into operation at the end of July 2023. (2) All “monthly supply mix” graphs in ENTSOG WSO 2023/24 (e.g., Figure 15) refer to GWh/d in the vertical axis while they refer to “sum of the month” in the horizontal axis. ENTSOG should ensure consistency in the way data are displayed and correct the graphs accordingly.


text: Table 1: LOLE in Spain: ERAA vs. NRAA and the Reliability Standard (hours)

text: Target year 2026 2028 2030 2035

text: Reliability Standard 1.50 1.50 1.50 1.50 ERAA 4.03 4.83 0.28 0.54 NRAA - 4.08 2.41 - Source: ACER based on ERAA 2024 and Spanish NRAA data Note: The Spanish NRAA models only two target years in the ED phase: 2028 and 2030

text: Table 2: Differences between the NRAA and ERAA: Impact on LOLE

text: Impact on LOLE # Where? What? (increase/decrease)

text: Regional scope (see Figure 1) inconclusive Structure 2 Inclusion of Balearic Islands and Ceuta increase 3 No curtailment sharing decrease Method 4 Less forced outage samples inconclusive 5 Lower capacity (see Figure 2) increase 6 Input data: storage Lower hydro pump availability increase 7 Longer battery duration decrease 8 Higher forced outage rate increase Input data: gas turbine 9 Fixed planned maintenance for all years increase 10 Input data: demand Hourly profile from ERAA 2025 increase Source: ACER based on Spanish NRAA

text: The LoLE impact in differences stem from the Spanish NRAA, for which Red Electrica conducted a comparative assessment based on modelling and its expertise to evaluate their effect on the LOLE results compared with ERAA (see Table 2 in the NRAA). Page 5 of 15

text: Figure 1: Spatial coverage: Spanish NRAA

text: Source: ACER based on Spanish NRAA data

text: Technical Annex to the ACER Decision No 07/2025

text: Figure 2: Difference in projected storage capacity in Spain (GW) for 2026, 2028, 2030, and 2035

text: NRAA ERAA

text: Hydro Pump

text: Batteries NRAA ERAA

text: 2035 2030 2028 2026 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 GW Source: ACER based on ERAA 2024 and Spanish NRAA data

text: Figure 3: Battery-to-RES capacity ratio in Spain versus EU average

text: 6% EU-27 Spain

text: Source: ACER based on ERAA 2024 and Spanish NRAA data Note: Battery capacity deployment in the EU, as outlined in the ERAA, broadly aligns with the NECP targets, which also account for future projects supported by state aid schemes. The Spanish NRAA assumptions, however, considers only currently planned battery deployment projects (all under state aid).

text: Approved under the State aid Temporary Crisis and Transition Framework and partially financed by the European Regional Development Fund.

text: In the ERAA 2024, storage capacity remains largely stagnant: only 3 GW batteries are expected to enter the EU electricity system, with most coming online only by 2035. 5 By 2030, the 8 GW resource gap in the Spanish NRAA relative to the ERAA results in approximately 6 GW more gas capacity remaining in the NRAA module (21537 MW in the NRAA versus 15721 MW in the ERAA). A simple capacity comparison suggests Spain experiences a net loss of 2 GW in the NRAA. Yet, assessing adequacy is far more complex. Battery storage contributes differently to system adequacy than gas turbines. Gas turbines can provide continuous output if fuel is available, while batteries are constrained by their limited energy capacity, typically able to deliver full power for only 2–4 hours. This duration may be shorter than actual scarcity periods, meaning batteries cannot always fully cover them. According to the Cost of New Entry report by the Spanish energy regulator, CNMC, the availability of resource capacity to deliver power during scarcity events is estimated at 27–70% for batteries, 73–82% for pumped hydro, and 82–83% for gas turbines. Thus, the higher reliability of gas turbines offsets the storage shortfall and higher demand peaks.

text: The mandatory FRC capacity provision limits the maximum operating power of generators, since they must maintain a portion of capacity available to increase output when needed to stabilise grid frequency. However, this obligation itself does not appear to significantly constrain market incentives – such as potential revenue streams – for storage development, given that the FCR requirement in Spain is quite low – limited to 400 MW. 7 Considering both large-scale and distributed storage. 8 See section 2.4.2 on storage in the Spanish implementation plan. 9 The root cause of the blackout has not yet been determined; however, it does not appear to be related to resource adequacy, as generation units were disconnected from the grid rather than unavailable. The loss of generating units capable of absorbing reactive power and stabilizing voltage led to a cascading failure, ultimately causing the widespread Iberian power grid blackout. The trends and projections scenario will be included in the ongoing revision of the ERAA methodology, which will provide information on its definition and modelling approach.

text: Figure 4: Frequency of ENS duration

text: 2-hour battery 4-hour battery 120 fully covers fully covers 2028 2030 these events at most events 100 full power nces 80 Bulk of ENS events 60 last three hours Occura 40 20 0 1 2 3 4 5 6 7 ENS length, hours

text: Source: ACER based on Spanish NRAA modelling results Note: In all Monte Carlo modelling runs – 36 weather scenarios x 5 forced outage samples – for every target year

text: Table 3: Differences between the NRAA and ERAA: Rationale and assessment

text: # Where? What? Reason Justified

text: Regional scope Regional scope justified Structure 2 Inclusion of Balearic Islands and Ceuta National specificities justified

text: No curtailment sharing Simplification justified Method 4 Less forced outage samples Simplification justified

text: Lower capacity Data update not justified Input data: 6 Lower hydro pump availability Data update justified Storage 7 Longer battery duration Data update justified

text: Higher forced outage rate Data update justified Input data: gas turbine 9 Fixed planned maintenance for all years Data update not justified

text: Input data: 10 Hourly profile from ERAA 2025 Data update justified Demand

identifier: ACER Opinion No 11/2025

publisher: Europeiska unionens byrå för samarbete mellan energitillsynsmyndigheter

sprak: en

title: ACER Opinion 11-2025 on the Spanish National Resource Adequacy Assessment

serie: yttranden

text: No 11/2025

type: rubrik

text: OPINION

text: on the National Resource Adequacy Assessment of Spain

text: 7 November 2025

text: A C E R O P I N I O N N O 1 1 / 2 0 2 5

type: stycke

text: Executive summary

text: Electricity

text: Regulation (EU) 2019/943

text: requires the European Network of Transmission System Operators for Electricity (ENTSO-E) to carry out the European resource adequacy assessments (ERAAs) on an annual basis. To complement ERAA, Member States may also carry out a national resource adequacy assessment (NRAA). If an NRAA identifies concerns not reflected in the European assessment, the Member State must explain the differences and submit the national assessment to ACER for opinion. Following the ERAA 2024, Spain conducted its NRAA, prepared by the transmission system operator (TSO), Red Electrica, and submitted to ACER on 8 September 2025. The NRAA complements the ERAA by reflecting Spain-specific electricity system developments.

text: Key Findings of the Spanish NRAA

text: The outcomes for 2028 are broadly consistent with ERAA. However, for 2030, the national assessment shows an adequacy concern, expressed in the loss of load expectation (LOLE), rising to 2.4 hours – above the 1.5-hour reliability standard – identifying a new adequacy concern in 2030 not reflected in the ERAA.

text: ACER’s Assessment of Differences

text: Structural adjustments in the NRAA (geographic focus and implicit modelling of Balearic Islands and Ceuta) were deemed justified and improve national relevance. Methodological simplifications (reduced forced outage samples, exclusion of curtailment sharing) cut complexity, impacting modelling results. These simplifications are considered reasonable given limited impact on adequacy results in the Spanish peninsular electricity system. Input data updates reflect conservative assumptions: • Spanish NRAA projects storage growth considerably below both ERAA levels and the National Energy and Climate Plan (NECP) policies. The assumption that only currently secured projects will materialise is unjustified, given the rising renewables deployment and evolving policy frameworks. • Modelling of the gas turbine fleet availability is more conservative, with higher rate and longer duration of forced outages. These constrains are based on historical data and are, therefore, justified. • Demand profiles were updated, aligning with those of ERAA 2025 that better represent demand seasonality. This adjustment is, therefore, justified. • The fixed 2026 gas turbine fleet maintenance profile is applied to all target years modelled. Such approach is not consistent with the ERAA 2024 and is, therefore, not justified.

text: Conclusion

text: ACER acknowledges that in recent years, battery deployment in Spain has not seen an increase that would necessarily suggest the NECP targets are attainable without regulatory intervention. Nevertheless, taking battery projects already under financial support as the sole basis for future capacity expansion is deemed overly conservative. ACER also finds that fixed maintenance profiles fail to capture anticipated changes in the Spanish electricity system. However, ACER notes that the impact of these unjustified differences on adequacy results appears to be low. Most deviations from the ERAA 2024 are related to national specificities and local conditions and hence are deemed justified. Overall, ACER finds the assessment is clear and well-executed, complementing the European assessment.

text: A C E R O P I N I O N N O 1 1 / 2 0 2 5

text: 1. Background

text: Article 20 of Regulation (EU) 2019/943

text: (Electricity Regulation) requires Member States to monitor resource adequacy within their territory based on the European Resource Adequacy Assessment (ERAA). It also allows them to complement the ERAA by conducting a National Resource Adequacy Assessment (NRAA) according to Article 24 of the Electricity Regulation. Either of the two assessments can identify resource adequacy concerns, but both assessments must be based on the ERAA methodology. The adequacy concerns identified through these assessments should be in the first place addressed by eliminating regulatory distortions or market failures, and, where it does not suffice, by introducing capacity mechanisms.

text: 2 According to Article 24(3) of the Electricity Regulation, where the NRAA identifies an adequacy concern that was not identified in the ERAA, the NRAA must include reasons for the divergence between the two assessments, including details of the sensitivities used and the underlying assumptions. The Member State must publish the NRAA and submit it to ACER for opinion. ACER’s opinion assesses, on a case-by-case basis, whether the differences between the two assessments are justified. ACER primarily considers the differences identified and reasoned by the Member State in the submission, but may also identify further differences, if they also have a material impact on the results.

text: 3 The national body that is responsible for the NRAA, which can be a Transmission System Operator (TSO) or a different body designated by the Member State, must take due account the ACER's opinion, and, where necessary, amend its assessment. Where it decides not to take ACER's opinion fully into account, it must publish a report with detailed reasons.

text: 4 The latest ERAA (ERAA 2024) was approved by the ACER Decision on 11 August 2025. To complement it, the Ministry for Ecological Transition and the Demographic Challenge of Spain (the Spanish Ministry) requested the Spanish TSO, Red Electrica, to conduct a National Resource Adequacy Assessment (Spanish NRAA or NRAA, published in September 2025).

text: 5 On 8 September 2025, the Spanish Ministry submitted its NRAA to ACER. The submission includes reasons for its divergence from the ERAA 2024, as well as the details of the sensitivities used and the underlying assumptions.

text: 6 This Opinion follows the submission of the Spanish NRAA and evaluates whether the differences between the Spanish NRAA and the ERAA 2024 are justified.

text: 7 This Opinion is addressed to the Spanish Ministry and issued in accordance with

text: Article 9(2) of Regulation (EU) 2019/942

text: and Article 24(3) of the Electricity Regulation.

text: 2. Summary of the Spanish NRAA

text: 8 The aim of the Spanish NRAA is to complement the ERAA 2024 by adopting different input assumptions and modelling approaches that more adequately reflect the technical performance of the Spanish electricity system – based on historical observations – and capture recent market trends in storage resource deployment in Spain.

text: 9 The modelling results of the central reference scenario are shown in Table 1. The NRAA identifies adequacy concerns in Spain in both 2028 and 2030, as the modelled Loss of Load Expectation (LOLE) exceeds the reliability standard of 1.5 hours. While 2028 LOLE is broadly consistent with the ERAA results, the 2030 LOLE of 2.41 hours represents a new adequacy concern identified in the Spanish NRAA only. A C E R O P I N I O N N O 1 1 / 2 0 2 5

text: 10 This divergence in the LOLE results is due to differences in the modelling assumptions between the Spanish NRAA and the ERAA 2024. These differences are discussed and assessed by ACER in the following section.

text: 3. ACER’s assessment

text: 11 ACER welcomes the Spanish NRAA and considers it a well-developed assessment of the Spanish electricity system, enriched with relevant country-specific details. The report provides a clear description of the methodological modelling assumptions, the differences to ERAA 2024 and the adequacy results. Also, the implementation of the Economic Viability Assessment (EVA) phase is well appreciated, as it allows to consider market-based resource development and thus provides a proper foundation for resource adequacy assessment.

text: 12 The differences between the Spanish NRAA and the ERAA 2024 fall into three categories: (i) structural, (ii) methodological and (iii) input data. Each difference is listed in Table 2, along with its impact on LOLE. A detailed description of these differences is provided later in this section. A C E R O P I N I O N N O 1 1 / 2 0 2 5

text: 3.1. Structure

text: Difference #1 Regional scope (see Section 4.2.2 in the NRAA)

text: 13 Description: An NRAA is an assessment with a regional scope compared to the pan-European ERAA. In the Spanish NRAA, coverage is highlighted in Figure 1: Spain in red and the other modelled countries in pink. Power imports from non-modelled (white) bidding zones are only possible when electricity prices approach the price cap and are constrained by net transfer capacity.

text: 14 Relevance: Reducing the geographical scope in electricity system modelling reduces complexity, enabling faster and more resource-efficient analyses while allowing for a deeper focus on a specific region.

text: 15 Assessment: The reduced spatial coverage in the NRAA includes the relevant set of countries – Spain’s direct neighbours, Portugal and France – along with other bidding zones that may have a significant impact on Spanish power grid’s cross-border exchanges. Combined with simplified import assumptions from non-modelled bidding zones, this leads to only a minor impact on LOLE compared with the pan-European ERAA result and is, therefore, considered justified. Difference #2 Inclusion of Balearic Islands and Ceuta (see Section 4.2.4 in the NRAA)

text: 16 Description: Balearic Islands and Ceuta are additional electricity systems with power connections to the Spanish peninsular electricity network, which are implicitly modelled in the Spanish NRAA.

text: 17 Relevance: Improved representation of the Spanish electricity system bringing it closer to reality.

text: 18 Assessment: The inclusion of the additional electricity systems connected to the peninsular grid enhances the representation of the Spanish system and is hence justified.

text: 19 It is noted that in the NRAA, meeting demand in these newly added regions is given priority over the Spanish peninsular electricity system, which was not the case in the ERAA 2024. In the event of power shortage, electricity supply to these regions takes precedence. Under this assumption, the LOLE in the peninsular Spanish electricity system might increase. The largest absolute increase in LOLE this difference brings is 1.6 hours in 2028. A C E R O P I N I O N N O 1 1 / 2 0 2 5

text: 3.2. Method

text: Difference #3 No curtailment sharing (see Section 4.2.1 in the NRAA)

text: 20 Description: The curtailment sharing mechanism applied in the ERAA 2024 ensures that energy shortages are fairly distributed across bidding zones whose domestic capacity is not sufficient to meet local demand. This reflects the actual functioning of the spot markets. However, the curtailment sharing feature is not included in the Spanish NRAA.

text: 21 Relevance: Curtailment sharing is embedded in the EUPHEMIA algorithm for day-ahead electricity trade among EU bidding zones. It spreads the impact of network constraints more evenly. When applied to future electricity system modelling, this feature is essential in multibidding-zone simulations to ensure accurate Energy Not Served (ENS) results in markets facing resource scarcity.

text: 22 Assessment: Curtailment sharing significantly impacts the LOLE results. In ERAA 2024, its application led to more than doubling the average LOLE per bidding zone as explained in ACER’s ERAA 2024 Decision.

text: 23 ACER observes that in the Spanish NRAA, curtailment sharing impact may be limited. The Spanish electricity system on the Iberian Peninsula may experience a lower curtailment sharing effect, as it is connected to only two other bidding zones – Portugal and France. Moreover, according to the ERAA 2024 , Spain shows a low correlation of scarcity events with its neighbours, which indeed could limit the curtailment sharing impact. Additionally, due to this difference the largest absolute LOLE decrease compared to the ERAA 2024 is 0.8 hours in 2028. This confirms the low impact of the curtailment sharing. Given this limited impact on LOLE, its omission in the NRAA is justified. Difference #4 Less forced outage samples (see Section 4.2.3 in the NRAA)

text: 24 Description: In the ERAA 2024, each weather scenario is simulated with 15 different forced outage samples, whereas the Spanish NRAA reduces this to 5 samples per scenario.

text: 25 Relevance: Repetitive forced outage runs (15 in ERAA) provide robust LOLE results accounting for uncertainty, capturing a wide range of potential outcomes and providing a more realistic analysis.

text: 26 Assessment: Red Electrica ran its NRAA modules with 5 forces outage samples and compared the results with the ERAA, which uses 15 samples. The difference in LOLE was minor – the reduced sample count lowered LOLE by 0.1 hours in 2028. This limited impact on LOLE justifies the use of this simplified approach. The approach is also in line with ACER’s request to streamline the ERAA methodology by reducing computational complexity with a limited impact on the robustness of the results.

text: 3.3. Input data: Storage

text: Difference #5 Lower capacity (see sections 5.2.1 and 5.2.2 in the NRAA)

text: 27 Description: Initial assumptions for storage capacity, before the EVA phase, are much lower in the Spanish NRAA than in the ERAA 2024, as shown in Figure 2. The NRAA assumes that only the currently planned hydro pump and battery projects will be commissioned within the study horizon. All these projects are supported by State aid schemes. A C E R O P I N I O N N O 1 1 / 2 0 2 5

text: 28 The NRAA accounts for 2.5 GW of storage capacity already procured under the Spanish State aid scheme . With this assumption, the storage capacity in the NRAA is around 8 GW lower in 2030 and 16 GW lower in 2035 compared with the ERAA, and compared with the Spanish National Energy and Climate Plan (NECP) targets in its storage assumptions.

text: 29 This assumption in the Spanish NRAA is not in line with the projected growth trend of storage capacities in the EU. To illustrate this, the battery-to-RES (Renewable Energy Sources) capacity ratio is shown in Figure 3. At the EU level, this ratio gradually increases in the coming years, indicating that battery deployment speed in relative terms overtakes RES, providing additional flexibility to manage both RES surpluses and shortages. In contrast, the NRAA assumes that about 1.5 GW of battery capacity entering the market in 2028 would remain unchanged until 2035. With RES deployment rising rapidly over the same period, this results in a declining batteryto-RES capacity ratio in Spain, highlighting a growing gap compared to the European average.

text: 30 The EVA modelling phase is expected to address the battery deployment shortfall. However, despite batteries being included among the capacity expansion options, the NRAA shows no new battery deployments. This outcome likely stems from the inadequate representation of the business case of batteries. Notably, balancing revenues, which represent a consequent share of current batteries revenues, are not explicitly modelled. ACER finds it unlikely that there will be no market-based development of batteries in the next 10 years in Spain. A C E R O P I N I O N N O 1 1 / 2 0 2 5

text: 31 The need to better represent the business model of non-fossil flexible resources – an area where both the ERAA 2024 and the Spanish NRAA currently fall short – has been highlighted in ACER`s ERAA 2024 decision and also pointed out as an area for improvement in ACER’s request to streamline the ERAA methodology.

text: 32 The Spanish NRAA is not asked to improve the EVA module in the current assessment; however, the combination of low initial storage capacity assumptions and the unchanged modelling approach is likely to result in an underestimated outlook for battery deployment (see Figure 3).

text: 33 Relevance: A well-projected initial resource capacity, in particular for batteries, is essential as it forms the starting point for the EVA phase, where the business case for non-fossil flexibility is currently under-developed. Thus the EVA modelling phase likely underinvests in non-fossil flexible technologies and rather retains (does not de-invest) existing gas turbines longer in the system. As the NRAA decommissions fewer gas units than the ERAA, it offsets the impact of the differences on the adequacy results .

text: 34 Even if the EVA in the Spanish NRAA smoothens the impact on the adequacy results, the initial assumptions on the expected storage development tilt the capacity mix towards fossil generators. This, in turn, may impact the assessment of the indicative objectives for non-fossil flexibility that Member States are expected to establish under the Electricity Market Design

text: Regulation (EU) 2024/1747

text: 35 Assessment: Storage capacity expansion (pump hydro and battery) in the Spanish NRAA is projected far below the ERAA 2024 levels which broadly follows Spanish NECP – 8.6 GW in the NRAA compared to 16.6 GW in the ERAA by 2030. The storage expansion assumed in the NRAA is limited to currently planned projects, with no additional growth assumed over the next decade with or without State aid schemes.

text: 36 According to the ERAA methodology, projected storage expansion should align with the NECPs and be updated to reflect recent market trends. While current situation provides a reasonable basis for assessing energy systems over the next few years, they may further evolve over a longer time horizon, where recent patterns may no longer hold.

text: 37 The assumption that market conditions alone may not yet be sufficient to attract investment is supported by Spain’s relatively low level of battery penetration to date. Key underlying factors include: • Limited price arbitrage revenues: Due to the specificities of the Spanish electricity system, the wholesale price spreads are lower compared to countries such as Germany, which has a high level of battery deployment. In 2025 (till 3 October), the average daily maximumminimum day-ahead price spread in the Spanish wholesale electricity market is calculated by ACER at 103 €, compared with 138 € in Germany (ENTSO-E Transparency Platform data). A C E R O P I N I O N N O 1 1 / 2 0 2 5 • Regulatory conditions: The mandatory, non-remunerated contribution of generators to the Frequency Containment Reserve (FCR) constrain storage deployment (see ACER’s market monitoring report on regulatory barriers).

text: 38 Considering the above factors, limited battery development may be reasonable in the near term, yet future market dynamics are likely to shift with rapid deployment of RES and improvements in market conditions. The Spanish implementation plan – particularly the Energy Storage Strategy and potential capacity mechanisms – aims to address these deficiencies. The strategy targets 20 GW of storage capacity (including solar thermal) by 2030 and sets out measures for effective deployment, including defining legal requirements for storage, clarifying the role of market actors, reducing administrative barriers, and facilitating research and development initiatives.

text: 39 Moreover, the recent Iberian electricity system blackout – though unrelated to resource adequacy – has triggered policy developments that aim inter alia to facilitate storage deployment. In particular, the Spanish government Royal Decree-Law 7/2025 introduces measures aimed at enhancing the resilience of the Spanish electricity system by facilitating greater integration of storage and flexibility. This provides increased reassurance for meeting the policy targets.

text: 40 Given that the current EVA implementation does not fully capture the potential of battery technologies, the input assumptions regarding initial battery capacity deployment in future years should be considered concurrently. A realistic battery planning should start from the evolving landscape rather than rely solely on the EVA outcomes. This is also in line with the planned “trends and projections scenario” for adequacy assessments. This scenario aims to capture the actual pace of the energy transition, which develops further from current levels but could remain below the trajectories envisioned in the NECPs . For these reasons, the low storage assumptions applied prior to the EVA phase, while acceptable for 2028, can no longer be justified from 2030 onwards.

text: 41 Recommendation: The initial storage assumptions (prior to the EVA investment modelling), should consider the potential removal of barriers and the anticipated developments in the electricity system that could facilitate greater storage deployment in the coming years.

text: 42 Recommendation: In future assessments, consider incorporating into EVA multiple revenue streams available to storage resources – already covered under the ERAA methodology – such as intraday market energy arbitrage and grid support services. This becomes particularly important when the initial assumptions on storage capacity deployment are low. As the energy transition accelerates, the performance of EVA should evolve accordingly, to better reflect the business models of non-fossil flexible resources. A C E R O P I N I O N N O 1 1 / 2 0 2 5 Difference #6 Lower hydro pump availability (see Section 5.2.1 in the NRAA)

text: 43 Description: Introduction, of a weekly capacity availability constraint for hydro pump closed-loop technology, is based on historical records and is absent in ERAA.

text: 44 Relevance: The availability constraint slightly reduces the maximum hydro pump generation power, limiting it to 80-100% of installed capacity depending on the week of the year.

text: 45 Assessment: Aligning seasonal availability of the hydro pump capacity with actual observations in the last three years aligns the results with the real-world conditions and is, therefore, justified. Difference #7 Longer battery duration (see Section 5.2.2 in the NRAA)

text: 46 Description: Compared with the ERAA 2024, around 40% of batteries in the Spanish NRAA are modelled with a doubled storage duration – rising from 2 to 4 hours.

text: 47 Relevance: Accurately reflecting battery size – specifically, the duration it can sustain full power at full charge – is essential for modelling power scarcity events. This constraint directly affects the reliability of results, making battery discharge time a key parameter in adequacy assessments.

text: 48 Assessment: This update in assumptions builds on the data from ongoing projects provided by promoters during the public support scheme tendering process. This is in line with the actual capabilities of the battery units in the currently planned projects, and thus it is justified. Capturing these details is crucial, as battery duration directly determines its contribution to covering scarcity periods. As shown in Figure 4, a significant share of ENS events in Spain – 47% in 2028 and 62% in 2030 – last three hours or more.

text: 3.4. Input data: Gas turbines

text: Difference #8 Higher forced outage rate (see Section 5.2.3 in the NRAA)

text: 49 Description: The performance of the Spain’s gas-fired Combined Cycle Gas Turbine (CCGT) fleet has declined, with historical records from the past four years showing increases in both outage frequency and duration. To reflect these trends, the NRAA updates the relevant parameters by raising the CCGT forced outage rate from 5% to 9% and extending the mean repair time from one day to three. These updates reflect the technical availability of the CCGT fleet as observed in 2024. As a result, on average, 9% of the installed CCGT capacity is unavailable due to longer forced outages. A C E R O P I N I O N N O 1 1 / 2 0 2 5

text: 50 Relevance: Historical availability data is essential in power system modelling, as it enables more accurate estimates of future resource needs and system reliability.

text: 51 Assessment: Incorporating recent historical availability data on CCGT forced outages into the module improves accuracy and is therefore justified.

text: 52 ACER recommends that future assessments apply different CCGT forced outage rates per subtechnology as categorised in ERAA – specifically CCGT old 1, old 2, present 1, present 2, new and Carbon Capture and Storage (CCS). This distinction is particularly important for Spanish assessment, as a significant share of CCGT capacity is decommissioned during the EVA phase. Decommissioning begins with the least technically efficient and oldest power plants, which typically have the highest outage rates. Applying different outage rates per sub-technology ensures that the remaining generators after the EVA phase are not burdened by the poor performance characteristics of the decommissioned old units. Difference #9 Fixed planned maintenance for all years (see Section 5.2.3 in the NRAA) Description: ERAA 2024 assumes that the maintenance of CCGTs is optimised to avoid scheduling during periods of adequacy risk. However, in recent years, planned CCGT maintenance in Spain has also occasionally coincided with scarcity periods. Therefore, in the Spanish NRAA, the planned 2026 CCGT maintenance profile is used, and this profile is applied to all modelled target years. Relevance: Capturing the historical seasonal profile of planned maintenance – especially the unavoidable maintenance near scarcity periods – is crucial for accurate future electricity system modelling. It ensures realistic reliability assessment, as such maintenance can directly limit resource availability during critical times. Assessment: While applying the actual maintenance profile may be reasonable in the near term, it becomes less appropriate over longer horizons. The NRAA projections show that by 2030, periods of system stress in Spain increasingly shift toward December, driven by changes in electricity demand patterns and the evolving generation mix under the energy transition. Consequently, the actual 2026 maintenance schedule is arguably not aligned with expectations for 2030 and is therefore not justified. ERAA methodology requires planned outage schedules to be optimised to avoid maintenance during likely ENS periods, while still respecting the share of capacity that must undergo maintenance in winter.

text: 53 ACER recommends that the NRAA moves away from a fixed maintenance profile and considers adopting an approach based on optimised planned maintenance, allowing for partial overlap with scarcity periods, as observed historically. This would better align maintenance profiles with the evolving Spanish electricity system.

text: 3.5. Input data: Demand

text: Difference #10 Hourly profile from ERAA 2025 (see Section 5.2.4 in the NRAA)

text: 54 Description: The hourly demand profile in the Spanish NRAA is sourced from the ongoing ERAA 2025 and then adjusted to match the annual demand volume of the ERAA 2024. Hence, in this process only the hourly demand shape is updated.

text: 55 Relevance: In 2030, the annual Spanish demand in the ERAA 2025 (291 TWh) is higher than in the ERAA 2024 (270 TWh). The hourly demand profile from the ERAA 2025 is scaled down to align with the ERAA 2024 annual volume. This adjustment leads to reduction in annual peak demand across all weather scenarios – by -3 GW in 2028 and -2.2 GW in 2030. As a result, the demand-supply balance, previously affected by lower storage capacity, is partially restored.

text: 56 Assessment: On the one hand, combining modelling inputs from different ERAA editions in the Spanish NRAA is both challenging and difficult to justify, as demand does not evolve in isolation. A C E R O P I N I O N N O 1 1 / 2 0 2 5 On the other hand, compared to the ERAA 2024, the updated NRAA profile provides a more accurate representation of actual demand seasonality in Spain with peak demands shifting from summer towards winter. Furthermore, the ERAA 2025 demand represents the second generation of the ENTSO-E’s weather scenario approach, which in theory should bring improvements to demand forecasting. Overall, these factors make the updated demand profile justified.

text: 4. Conclusions

text: 57 Table 3 presents ACER’s assessment of whether the differences between the Spanish NRAA and the ERAA 2024 are justified.

text: 58 ACER considers most of the differences between the Spanish NRAA and the ERAA 2024 edition to be justified. However, ACER finds two differences – #5 and #9 – not justified. The previous section explains ACER’s position and offers recommendations for improvements. In particular to (i) review battery capacity assumptions in light of evolving market frameworks; and (ii) consider an optimised gas turbine maintenance schedule that could better reflect the evolution of the Spanish system.

text: 59 The overall impact of these two differences on adequacy results (LOLE) is, however, limited. The lower battery capacity and constrained gas turbine availability under the fixed maintenance profile are ultimately offset by the reduced gas turbine decommissioning observed in the EVA modelling phase, thereby keeping the overall impact on LOLE low. However, the precise effect on system adequacy can only be accurately quantified through dedicated adequacy modelling using sensitivity scenarios.

text: 60 Considering the above, overall, ACER is of the view that the Spanish NRAA provides robust adequacy findings. ACER also recognises that the extended geographical scope and EVA investment modelling is a good practice, on par with the ERAA 2024 module. A C E R O P I N I O N N O 1 1 / 2 0 2 5 This Opinion is addressed to the Ministry for Ecological Transition and the Demographic Challenge of Spain. Done at Ljubljana, on 7 November 2025. — SIGNED — V. ZULEGER, ACER Director ad interim

type: vagledning

utgivare: acer