ACER Opinion 17-2026 on the consistency of gas and hydrogen national NDPs with the EU TYNDP

No 17/2026

OPINION

on the natural gas and hydrogen national network development plans

28 September 2026

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Executive summary

National network development plans (NDPs) for natural gas and hydrogen are the primary instruments for identifying infrastructure needs and planning gas and hydrogen network investments in line with evolving supply and demand, national energy policy and EU-level

priorities. The 2024 Hydrogen and Decarbonised Gas Market Package comprises Regulation (EU) 2024/1789 (the Regulation) and Directive (EU) 2024/1788 (the Directive). This Opinion is issued pursuant to Articles 26(9) and 60(2) of the Regulation, under which ACER assesses the consistency of national gas and hydrogen NDPs for gas and hydrogen with the corresponding EU TYNDP. While ACER’s assessment reflects the new legal framework established by the Package, it was carried out before the 5 August 2026 deadline for Member States to transpose the Directive into national law. The findings should therefore be read in the context of the Package’s ongoing implementation.

Coordination across energy systems and borders is essential, but institutional, methodological, and lack of regulatory oversight may prevent effective alignment.

Effective coordination requires alignment between NDPs and the EU TYNDP as well as across electricity, gas and hydrogen systems. Misalignment at any of these levels can lead to inconsistent assumptions, inefficient investment decisions and delayed infrastructure development. Achieving such coordination is particularly challenging where planning frameworks are at different stages of development. ACER finds the NDPs broadly consistent with the EU TYNDP but sees scope to further strengthening consistency, the robustness and transparency in network planning. The alignment level between the EU and the national layer across sectors and Member States is divergent. A key factor underpinning this finding is that gas network development planning is well established across the EU, whereas hydrogen network planning frameworks remain at an early stage. Moreover, ACER identifies three main factors that currently weaken alignment between national and EU-level planning.

First, the implementation of the institutional frameworks for hydrogen planning remains

incomplete. Seventy-five per cent of Member States have neither designated nor certified an HNO. Poland is the only Member State reported as having completed the designation process in accordance with Article 71(2) of the Directive. Formal arrangements for hydrogen network planning remain incomplete in most Member States. In the meantime, in some Member States, gas TSOs appear to play a central role in hydrogen infrastructure development. Half of EU TYNDP projects are still not included in NDPs; hydrogen projects show particularly low inclusion at 38 per cent, though this represents progress from 33 per cent in 2024. Second, methodological differences continue to affect consistency. Approaches to scenarios, infrastructure needs assessment and projects as well as transparency vary across Member States and between national and EU-level planning. Not all national NDPs yet take account of the latest national energy and climate plans. Many NDPs lack a formal concept for identifying infrastructure needs and do not publish key project information including costs. Some NDPs are not publicly consulted and when they are, their results remain unpublished. At the same time, progress is evident in several areas, including the consideration of gas and hydrogen decarbonisation aspects and the use of market consultations.

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EU TYNDP projects included in NDP (left) and HNO status across EU Member States (right)

ACER identifies four areas for improvement to strengthen gas and hydrogen network development planning:

Institutional framework

• Gas and hydrogen NDPs should be prepared on a biennial basis and to the extent possible be time-aligned with the EU TYNDP development process. • The Member States should ensure timely and effective transposition and implementation of Directive (EU) 2024/1788 requirements for NRA oversight, approval and amendment of NDPs under Articles 55 and 78.

Planning transparency and consultation

• The Member States should ensure the timely and effective transposition and implementation of the consultation and transparency requirements already established by Directive (EU) 2024/1788. Beyond these minimum legal requirements, consultation should also cover key methodological elements, such as infrastructure needs assessments and cost-benefit analyses, where these are not already subject to consultation. Information on the consultation process and the NRA’s assessment of the NDP should be published. • Market consultations to assess future hydrogen demand should be introduced in the relevant Member States and considered in their NDPs. • Gas and hydrogen NDPs and the EU TYNDP should publish key project information. This includes a technical description, expected commissioning date, investment costs, and status. It should also show progress since the previous edition of the plan, any increase of transport capacity, and cross-refer to the EU TYNDP or NDP project code, as applicable.

Cross-border and cross-sectoral coordination

• The system operators should strengthen coordination and cooperation, including data exchange, in gas and hydrogen NDP preparation process.

• At least the central EU TYNDP scenario should be taken into account when developing scenarios for gas and hydrogen NDPs.

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Integration of decarbonisation measures

• The Member States should ensure timely and effective transposition and implementation of Directive (EU) 2024/1788’s requirements on project inclusion in the gas and hydrogen NDPs. In particular, NDPs should, among others, include key projects for the decarbonisation of the gas sector, such as decommissioning projects, projects for the repurposing of gas infrastructure for hydrogen and projects for biomethane injections into natural gas transmission system.

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Table of contents

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1. Background

1 The transition of the European energy system towards climate neutrality is set out in the European Green Deal, the Fit for 55 package and the Hydrogen and Decarbonised Gas Market Package. It requires a gradual decarbonisation of the gas sector and the development of infrastructure capable of transporting renewable (i.e. biomethane and green hydrogen) and lowcarbon gases (i.e. produced from non-renewable sources, following technological processes that drastically cut greenhouse gas emissions by at least 70% compared to fossil gas). Gas and hydrogen networks are expected to play an important role in ensuring security of supply, supporting the decarbonisation of hard-to-electrify industrial sectors and providing energy storage and system flexibility. In this context, timely and coordinated planning of gas and hydrogen networks is essential to ensure that infrastructure investments support energy transition in a cost-effective manner.

2 Network development plans (NDPs) are the primary planning instruments for assessing and identifying network investments needs aligned with energy policy goals and the evolving needs of energy users. As the energy sector transforms, network planning must increasingly consider the repurposing of existing gas infrastructure, the development of the hydrogen infrastructure and the growing interdependencies between gas, hydrogen and electricity networks.

3 Network planning takes place at both national and EU level. National gas transmission system operators (TSOs) and hydrogen network operators (HNOs) prepare national network development plans (NDPs), while the European Network of Transmission System Operators for Gas (ENTSOG) develops the EU-wide ten-year network development plan (EU TYNDP). At present, the EU TYNDP covers both gas and hydrogen infrastructure. Following the establishment of European Network of Network Operators for Hydrogen (ENNOH), separate EUlevel planning processes for gas and hydrogen infrastructure are expected to be developed under the responsibility of ENTSOG and ENNOH, respectively.

4 In this evolving context, coordinated and coherent infrastructure planning at national and EU level is essential to avoid the risk of either overinvestment, insufficient network capacity or uncoherent planning of trans-European investments. Strengthening the consistency across network planning processes is, therefore, key to ensure efficient infrastructure development.

5 This Opinion is issued pursuant to Articles 26(9) and 60(2) of the Regulation. Under Article 26(9), ACER reviews national natural gas NDPs to assess their consistency with the EU TYNDP for natural gas. Under Article 60(2), ACER provides an opinion, where relevant, on national hydrogen transmission NDPs to assess their consistency with the EU TYNDP for hydrogen. Where ACER identifies inconsistencies, it recommends amendments to the relevant national NDP or to the corresponding EU TYNDP, as appropriate.

6 This assessment was conducted before the 5 August 2026 deadline for Member States to transpose the Directive into national law.

2. ACER assessment

7 ACER’s assessment draws on responses from NRAs to two questionnaires. The first covers methodological aspects of gas and hydrogen NDPs. The second checks how consistent draft EU TYNDP 2026 projects are with the NDPs. The main findings are presented in this Opinion, while detailed information collected from NRAs is provided in the Annex. A C E R O P I N I O N N O 1 7 / 2 0 2 6

2.1. Widely established gas NDPs, emerging hydrogen NDPs

8 Gas transmission networks in the EU are operated by 47 certified gas TSOs. Almost all gas TSOs are obliged to prepare a NDP. Under the previous Gas Directive , the NDP obligation applied specifically to TSOs operating under the independent transmission operator model. This may explain why the TSOs in Finland and Sweden are not subject to such a requirement. One TSO in Belgium and one in Bulgaria are also currently exempted under the applicable national frameworks because they operate only interconnectors.

9 This situation is expected to change following transposition of the Directive. Article 55(1) requires all gas TSOs and transmission HNOs to participate in the national NDP framework, irrespective of the unbundling model.

10 In most Member States where gas NDPs are prepared, a single transmission-level gas NDP is developed irrespective of the number of TSOs operating within the country. France is the sole exception, with separate NDPs prepared by the two TSOs.

11 As regards hydrogen network planning, Poland is the only Member State with a certified and designated HNO in line with Article 71(2) of the Directive. In Belgium, the HNO was certified and designated according to the national law and is undergoing reassessment in light of the Directive. In four additional Member States (Denmark, Hungary, Luxembourg and Spain), HNOs have been designated or entrusted with hydrogen network operator functions at national level, including on a provisional basis in Hungary and Spain, but have not been reported to be designated or certified in accordance with Article 71 of the Directive. , A C E R O P I N I O N N O 1 7 / 2 0 2 6 Figure 1: Hydrogen Network Operator designation and certification status across EU, 2026

12 In all Member States with a designated HNO, the HNO prepares a hydrogen NDP. In Denmark and Hungary, the HNO and the TSO prepare a joint integrated gas and hydrogen NDP, with separate chapters showing network maps for each sector. In Belgium, Luxembourg, Poland and Spain, gas and hydrogen NDPs are separate deliverables.

13 Most Member States have not yet set up a hydrogen network planning framework, nor designated or certified an HNO. Sometimes, another entity, usually the gas TSO, carries out HNO-related functions, such as hydrogen infrastructure development studies or representing their countries within ENNOH. However, there are also Member States where the development of hydrogen infrastructure is not included in any gas or other system operators’ NDP .

14 ACER finds that, while the NDPs are the well-established instruments for gas infrastructure planning, hydrogen network planning frameworks are still emerging. Nevertheless, ACER welcomes the inclusion of hydrogen network infrastructure in the NDPs of other system operators, particularly gas TSOs, which currently appear to play a central role in some Member States in advancing hydrogen infrastructure planning.

2.2. Legal effect of NDPs

15 The legal effect of gas NDPs varies across Member States. In approximately half of the Member States , gas NDPs are legally binding in respect of at least some of the investments they contain. In others, they serve primarily as indicative planning instruments and do not create an obligation A C E R O P I N I O N N O 1 7 / 2 0 2 6 to implement the projects listed. In Cyprus, Germany and Greece, approved gas NDPs are binding in respect of all included projects and impose an obligation on TSOs to implement them.

16 By contrast, where hydrogen infrastructure is already included in NDPs, the planned investments are generally indicative with no implementation obligations. Germany is the only Member State that reported that prospective HNOs would be required to implement investments included in the NDP.

2.3. Biennial NDP frequency for timely and consistent plans

17 Regular updates of NDPs and their underlying data are essential for re-assessing grid investment needs in an evolving context. Article 55(1) of the Directive requires gas and hydrogen NDPs to be prepared at least every two years. Most Member States already follow a biennial cycle, in line with the frequency of the EU TYNDP. However, several countries currently prepare NDPs annually or every four years.

18 ACER recommends timely implementation of the Directive’s biennial planning requirement and alignment with the EU TYNDP cycle. This would improve consistency between national and EUlevel planning while avoiding unnecessary administrative burden and the risk of delays associated with more frequent cycles. In this regard, ACER welcomes the plans in Finland, Ireland and Slovenia to move from annual to biennial NDP cycles.

19 ACER also welcomes the use of the same publication frequencies for gas and hydrogen NDPs in Belgium and Poland where separate gas and hydrogen NDPs are prepared. Applying the same planning cycle to both plans supports consistency between gas and hydrogen infrastructure planning. Additional information on frequencies, NDPs’ organization and the recent challenges experienced by the NRAs in relation to NDPs are provided in Tables 2 and 6 of the Annex.

20 Time alignment between national and EU-level planning is important for effective infrastructure development. The EU TYNDP should build on NDPs , while NDPs may use ENTSOs’ scenarios or other elements from the EU TYNDP process. Misaligned planning cycles increase the risk of using outdated data. ACER highlights the benefits of synchronising NDP and EU TYNDP preparation, particularly for key building blocks such as scenarios or needs assessment. Achieving this alignment requires improvements to the EU TYNDP process, especially timely development of scenarios as also emphasized in ACER Opinion 04/2025.

2.4. Strong regulatory oversight for effective infrastructure planning

21 Effective regulatory oversight is essential to ensure that network development planning by ENTSOG, TSOs and HNOs is transparent, non-discriminatory and consistent with market needs, security of supply, efficient system development and the EU’s energy and climate objectives. A C E R O P I N I O N N O 1 7 / 2 0 2 6

22 At EU level, ACER exercises several functions in relation to network development planning. It provides opinions on the EU TYNDPs and monitors their implementation in accordance with Regulation (EU) 2019/942 and the Regulation. ACER also reviews national gas NDPs and provides opinions on national hydrogen transmission NDPs, where relevant, to assess their consistency with the corresponding EU TYNDPs. Where inconsistencies are identified, ACER recommends amendments to the relevant national NDP or to the corresponding EU TYNDP, as appropriate, pursuant to Articles 26(9) and 60(2) of the Regulation.

23 At national level, the level of scrutiny exercised by NRAs and other stakeholders over gas NDPs varies across Member States. Depending on national legislation, this may include approving NDPs, directly applying or requesting amendments, issuing formal acts such as opinions, monitoring implementation, or participating in consultation processes. In some cases, the NRA has no formal role beyond being informed of the NDP. ACER finds that in approximately half Member States, the NRA has the authority to approve or reject TSO’s draft gas NDPs and apply or request amendments. In the remaining countries, the NRA’s role is more limited and typically consists of being consulted or carrying out a non-binding review . In Luxemburg and Sweden, the NRA has no formal role in the NDP process.

24 No NRA indicated that the roles, responsibilities or processes for the development of hydrogen NDPs differ or are expected to differ from those applicable to gas NDPs.

2.4.1. Strengthened role for the NRAs in the planning process

25 The Hydrogen and Decarbonised Gas Market Package and Regulation (EU) 2022/869 on guidelines for trans-European energy infrastructure provide the overarching legal and regulatory framework for the development of gas and hydrogen markets and networks in the EU. Articles 55 and 78 of the Directive, part of the Hydrogen and Decarbonised Gas Market Package, has assigned NRAs additional responsibilities, in particular to approve and amend the NDPs. NRAs must check whether the NDPs comply with the requirements of the Directive, cover all investment needs; and are consistent with the EU-wide TYNDPs and the gas EU-wide simulations of disruption scenarios and national risk assessments.

26 ACER finds that the transposition of the Directive’s provisions on NRA’s oversight over NDPs is ongoing in many Member States. Only the NRA in Poland reported that provisions for hydrogen have mostly already been transposed into their national laws. Nevertheless, NRAs often reported that they already perform some of the corresponding activities, irrespective of the formal transposition status. The implementation of the relevant hydrogen-related planning provisions remains at an earlier stage than that of comparable gas-sector provisions.

27 ACER notes that, in the absence of a national regulatory framework for hydrogen network planning, some NRAs are unable to assess hydrogen development projects. ACER reiterates its call on Member States to transpose the Hydrogen and Decarbonised Gas Market package into the national legislation and establish a framework for hydrogen network planning. A C E R O P I N I O N N O 1 7 / 2 0 2 6

2.4.2. Most recent NRA review of NDPs

28 The most recent NRA reviews of NDPs illustrate the importance of effective regulatory scrutiny of network development planning. In Member States where NRAs already exercise approval or amendments powers, that scrutiny has enabled concerns regarding project justification, costs and consistency with national policy objectives to be addressed before projects proceed: • In Austria, the proposed NDP was rejected by the NRA, because for some projects, the cost increase assumptions were insufficiently substantiated, the technical necessity and economic viability were not demonstrated and the requirements for climate-neutrality by 2040 were violated. • In France, the NDP itself has not been rejected, the NRA has rejected individual projects through its annual approval of TSO investment plans. • In Germany, the NRA rejected some projects and asked for formal amendments. • In Italy, during the last approved NDP’s review process, the NRA rejected some projects.

29 These examples should be considered in the context of the ongoing transposition of the Directive. Articles 55 and 78 strengthen the role of NRAs in national network development planning, including through scrutiny, approval and amendment powers. Member States were required to transpose the relevant provisions by 5 August 2026.

30 ACER therefore highlights the importance of the timely and effective implementation of the Directive’s requirements on regulatory oversight of NDPs. The examples above indicate that meaningful NRA scrutiny can help identify unsupported investment assumptions, insufficiently demonstrated infrastructure needs and inconsistencies with wider energy and climate objectives at an early stage of the planning process. ACER highlights the importance of strong regulatory oversight in the network development planning process.

2.5. Enhanced coordination, consultation and transparency for more aligned NDPs 2.5.1. Coordinated planning of the EU energy infrastructure

31 As the energy transition progresses, coordination among energy system operators is becoming increasingly important to ensure coherent infrastructure development across the energy system. The growing interdependence of electricity, gas and hydrogen systems results in investment needs in one sector often being driven by developments in another. This makes cross-sectoral coordination essential to align investment decisions, anticipate future demand and identify synergies and the most cost-efficient investments.

32 ACER finds that cooperation between the gas and other infrastructure operators is established in most Member States. Gas TSOs cooperate with other operators primarily through the preparation of the NDPs. In addition, multiple NRAs also reported that the TSO’s NDP is aligned with the latest NDPs in the neighbouring countries. A C E R O P I N I O N N O 1 7 / 2 0 2 6

33 At present, ENTSOG prepares the EU TYNDP for gas and hydrogen infrastructure, while ENTSO-E prepares the EU TYNDP for electricity. At national level, there is currently no integrated cross-sectoral NDP by TSO(s) and HNO(s) covering electricity, gas and hydrogen infrastructure. ACER welcomes that in Germany, the draft NDP was prepared by all gas TSOs and possible future HNOs for the first time in March 2026. As regards the gas and hydrogen sectors, an integrated gas and hydrogen NDP is prepared in Denmark, Hungary and Lithuania. Similarly, in several other countries, where the relevant regulatory framework has not yet been established, the gas NDPs include hydrogen infrastructure developments. Figure 2: Cross-sectoral scenarios in NDPs across EU, 2026

34 While the EU TYNDP already relies on jointly developed scenarios for electricity, gas and hydrogen , the adoption of similar cross-sectoral approaches at national level remains uneven across the EU. In Denmark, Germany, Italy, Lithuania, the Netherlands and Spain, gas and electricity TSOs jointly develop at least some scenarios for the electricity and gas sectors, typically also covering hydrogen . In Belgium, the joint scenario exercise is driven by the electricity TSO and the HNO, also coordinating with the gas TSO. Austria, France, Hungary and Romania reported joint scenarios for gas and hydrogen network planning, but not for electricity planning. ACER welcomes the recent introduction of joint electricity-gas-hydrogen scenario development in Lithuania and further welcomes that the same approach is planned in Austria.

35 Beyond the joint NDPs and scenario development processes, several NRAs reported other cross-sectoral efforts. These include joint consultation with industry and market participants to identify infrastructure needs for gas and hydrogen. They also include cooperation on the efficient use and potential repurposing of existing gas infrastructure for hydrogen. Separately, gas and electricity operators coordinate on infrastructure development and on optimal locations for hydrogen injections. ACER further notes that, pending the establishment of the hydrogen regulatory framework, gas TSOs often include hydrogen projects in their NDPs, which may support alignment between the development of these two sectors. A C E R O P I N I O N N O 1 7 / 2 0 2 6

36 ACER reiterates that transmission infrastructure development in the EU should evolve towards multi-sectoral planning, encompassing electricity, gas and hydrogen at both EU and, preferably, national level, to support more integrated infrastructure planning.

2.5.2. Transparency and consultation

37 Stakeholder engagement is key to ensuring that NDPs reflect the needs of network users and other stakeholders at both EU and national level. The Hydrogen and Decarbonised Gas Market Package already establishes extensive transparency and consultation requirements for both the EU TYNDPs and national NDPs.

38 At EU level, ENTSOG (and ENNOH, once established) must conduct extensive public consultations at an early stage and in an open and transparent manner when preparing the EU TYNDP, involving relevant market participants, NRAs, network users and other stakeholders. Draft plans must be published for comments, consultation documents and meeting minutes made public, and stakeholder input taken into account or reasons given where it is not followed.

39 At national level, Article 55 of the Directive requires stakeholder consultation on the scenarios underpinning gas and hydrogen NDPs and requires NRAs to consult actual and potential system users on the plans in an open and transparent manner and publish the results. Article 78 further requires NRAs to ensure that the overall national NDP process is open, transparent, efficient and inclusive.

40 ACER’s assessment illustrated on Figure 3 shows that at present, the TSOs publicly consult on draft NDP in about two thirds of Member States. In nine Member States, draft NDPs are subject to public consultation by both the TSO and the NRA, while in four Member States, the consultation is conducted by the NRA and in one Member State by the Ministry. In six Member States, public consultations are carried out on the specific planning building blocks, such as scenarios, projects or infrastructure needs. No public consultation on the NDP nor on any of its building block is currently carried out in Luxembourg. A C E R O P I N I O N N O 1 7 / 2 0 2 6 Figure 3: Consultations on national network development plans, EU-27, 2026

41 All draft or final NDPs are published except the hydrogen draft NDP in Spain. Furthermore, 11 NRAs reported that the results of the public consultations are also published, either in full, including comments and responses, or in summary form . Links to NDPs, consultation results and NRA scrutiny are included in Tables 4 and 12 of the Annex.

42 ACER recommends that Member States ensure the timely and effective transposition and implementation of the consultation and transparency requirements already established by the Directive, including the requirements for stakeholder consultation on the scenarios underpinning national NDPs, open and transparent consultation by NRAs on the NDPs, publication of consultation results, and an open, transparent, efficient and inclusive NDP process. Member States where no public consultation is currently carried out should ensure that the new framework is fully implemented.

43 Beyond these minimum legal requirements, ACER recommends that consultation also covers key methodological elements, such as infrastructure-needs assessments and cost-benefit analyses, where these are not already subject to consultation, and that information on the consultation process and the NRA’s assessment of the NDP be published. A C E R O P I N I O N N O 1 7 / 2 0 2 6 Increased efforts to better understand future hydrogen demand

44 Given the nascent stage of the hydrogen market, future hydrogen demand and supply remain uncertain. This makes engagement with potential network users essential for understanding and identifying future hydrogen infrastructure needs.

45 NRAs from 13 Member States reported that the interest of prospective hydrogen network users has been assessed through dedicated non-binding market consultations, typically conducted by the TSO or HNO. . Apart from Belgium where the NRA is informed of the consultation results and Poland where the NRA has a monitoring role, the NRAs play a limited or no role in this process. ACER welcomes the planned introduction of market consultations to assess hydrogen demand in Romania.

46 As regards the binding capacity booking procedures for hydrogen (i.e. open seasons), no open seasons or plans to introduce them were reported by NRAs in 2024 . ACER welcomes the subsequent introduction of open seasons in Denmark as well as the plans to introduce them in Belgium, France, Germany and Lithuania. The role of NRAs in these processes vary across Member States. In Denmark, the NRA approved the relevant methodology. In Belgium, open seasons are organized jointly by the HNO and the NRA and in Lithuania, the NRA is expected to play a supervisory role.

47 ACER considers important the coordinated development of hydrogen markets and infrastructure. ACER, therefore, recommends that hydrogen NDPs consider the outcomes of market consultations and open seasons to assess future hydrogen demand.

2.6. Methodological aspects in NDPs

48 At the EU level, the network development planning by ENTSOG follows three main steps: scenario development, identification of infrastructure needs and assessment of the costs and benefits of projects. At national level, the approach to these planning steps is determined nationally, in particular how scenarios are developed, whether and how the infrastructure needs are assessed and how projects are evaluated before their inclusion in NDPs.

2.6.1. Compatible NDP and EU TYNDP scenarios

49 The most recent EU TYNDP scenario development process resulted in a central scenario and two economic variants . According to ENTSO-E ang ENTSOG, the central scenario reflects the latest national strategies, updated National Energy and Climate Plans (NECPs), and EU policy objectives. The economic variants act as stress tests in assessing the resilience of the energy system under different macroeconomic conditions. The scenarios cover different time horizons up to 2050. A C E R O P I N I O N N O 1 7 / 2 0 2 6

50 At national level, the number of scenarios/visions used for the elaboration of NDPs ranges between one and seven scenarios . These scenarios’ time horizon spans around 10 years in the NDPs or all Member States, with some extending to 2040 (Poland for gas NDP), 2045 (Germany) and 2050 (Denmark, the Netherlands and Poland for the hydrogen NDP).

51 The alignment of scenarios with policy targets significantly varies between the Member States. 13 NRAs report alignment of the respective NDPs with the latest NECPs and 7 with Climateneutrality objectives set out in Article 2(1) of Regulation (EU) 2021/1119. 11 NRAs also reported alignment with other relevant scenarios at national level.

52 ACER reiterates the importance of NDPs and the EU TYNDP to be based on compatible scenarios. For this reason, at least the central EU TYNDP scenario should be taken into account at scenario development process for NDPs.

2.6.2. Assessing infrastructure needs

53 NRAs from 11 reporting Member States indicated a structured process in place to identify and quantify infrastructure needs, either as part of the NDP or through a separate planning process. In 6 of these Member States, needs are identified and quantified for both gas and hydrogen infrastructure within the NDPs. In the remaining 5, the assessment only covers gas infrastructure, carried out in three Member States within the NDP, and as a separate exercise in one . There are 7 additional Member States where infrastructure needs are considered through activities without a formal concept or metrics. In four of these Member States, these activities cover both gas and hydrogen infrastructure, while in the remaining three they are limited to gas infrastructure. In Estonia and Ireland, there is no activity to identify infrastructure needs. ACER welcomes Ireland’s plan to introduce it.

54 Infrastructure needs are mostly identified through a combination of bottom-up and top-down approaches. Bottom-up assessments are typically based on the needs of network users and offtakers as identified through market consultations or capacity requests, while top-down assessments consider broader policy and system-level drivers, such as decarbonisation objectives and security of supply. In many Member States, needs assessments are further supported by technical analyses, including network modelling, hydraulic simulations and system integrity assessments.

55 ACER finds that in Belgium, Ireland, Poland and Slovenia, infrastructure needs are identified and quantified using target cross-border capacities. In several other Member States, different metrics are applied, including location-, area- or border-specific needs (Austria, Belgium, Latvia, Lithuania) and system-wide indicators such as total gas import requirements (Cyprus, Croatia, Spain).

56 ACER sees room for wider and more systematic application of infrastructure needs assessments at national level. A C E R O P I N I O N N O 1 7 / 2 0 2 6

2.6.3. Projects in NDPs

2.6.3.1. Types of infrastructure projects’ assessments

57 The approaches used to assess projects differ significantly across Member States. In 11 Member States , cost-benefit analysis (CBA) is applied to gas NDP projects, while Estonia is the only Member State where CBA is applied to both gas and hydrogen infrastructure projects. In three other Member States , projects are assessed through different methods, such as feasibility studies or economic evaluations. In several Member States, however, projects are not subject to a formal economic assessment.

58 The evaluation of the value of cost of disruption of gas supply in NDPs remains limited and has been only reported for Italy and Lithuania. ACER reiterates that despite the challenging nature of such assessments, these assessments would be highly relevant for assessing the impact of potential gas supply disruptions. 2.6.3.2. Project inclusion in NDPs

59 ACER notes that meeting market demand for capacity and predefined policy scenarios are the main drivers for gas network development. 12 NRAs reported that network development is primarily market-driven, while eight indicated that it is driven by predefined scenarios. Three NRAs identified maintaining a high level of availability of existing network capacity as the main driver.

60 Gas transmission pipelines and compressor stations are included in NDPs of all TSOs. In addition, NDPs in 11 Member States include biomethane injection projects, while those in six and four Member States also cover LNG terminals and underground storage, respectively. A C E R O P I N I O N N O 1 7 / 2 0 2 6 Figure 4: Number of EU27 NDPs including hydrogen and repurposing projects, 2026

61 NDPs in 12 Member States include gas asset replacement projects. ACER welcomes the progress made in the recent two years in the inclusion of decommissioning and repurposing projects. Regarding repurposing and decommissioning, ACER finds a more nuanced picture across three project types. Nine Member States include projects that can or are to be repurposed, ten Member States identify projects deemed necessary due to repurposing and eight Member States identify projects that can or are to be decommissioned. 14 Member States have included at least one type of repurposing or decommissioning project in their NDPs, increasing from eight in 2024 . ACER also finds that a methodology for decommissioning or repurposing at the transmission level is applied in Germany. According to this methodology, TSOs are obliged to consider repurposing existing gas pipelines for hydrogen use. New hydrogen pipelines may only be approved where repurposing is not technically or economically feasible.

62 ACER finds that the treatment of biomethane in NDPs differs considerably across Member States. In 11 Member States, NDPs include dedicated biomethane projects. These mainly involve network adaptations to enable biomethane injection into the transmission network, direct transmission-level injection connection points and reverse-flow capacity from distribution to transmission networks. In 4 Member States, biomethane is considered in the scenario process, while in further four it is considered as a driver for network reinforcement without being reflected as dedicated NDP projects.

63 As regards the inclusion of hydrogen developments in NDPs, ACER finds that hydrogen pipelines are covered or considered in the NDPs in 11 Member States. Additionally, projects of repurposing existing gas pipelines to dedicated 100 % hydrogen pipelines are covered in NDPs in 6 Member States. Compressor stations, network adaptations to enable hydrogen blending into gas networks, national hydrogen production infrastructure and hydrogen injection connection points are each covered or considered in 4 Member States. Some NRAs also reported the inclusion of A C E R O P I N I O N N O 1 7 / 2 0 2 6 hydrogen underground storage, hydrogen distribution networks and suitable locations for powerto-X developments.

64 ACER finds that in 5 Member States, new gas infrastructure investments are required to comply with hydrogen-ready technical standards. This enables their future use for both natural gas and hydrogen.

65 ACER supports the inclusion of decommissioning and repurposing projects in gas NDPs in accordance with Article 55 of the Directive. Including such projects in NDPs is important in view of the evolving role natural gas will play during the energy transition. 2.6.3.3. Project-specific information in NDPs

66 EU TYNDP provides project-specific information including the commissioning year, maturity, implementation schedule and status, associated costs (for a limited number of projects) and information on inclusion in NDPs, where applicable.

67 The level of project-specific information included in NDPs varies across Member States . Overall, the level of detail provided for hydrogen projects is lower than for gas projects.

68 ACER finds that similarly to the EU TYNDP, project cost information is not publicly available in NDPs of several Member States. The highest level of cost transparency is observed in Belgium, Bulgaria, Cyprus, Estonia, Italy, Latvia, the Netherlands, Portugal and Slovenia, where investments costs of all or most projects are publicly available. In Austria ,Germany, France, Lithuania and Romania, only the total investment cost is publicly available. In Croatia, Czech Republic, France, Lithuania and Poland, project costs are available to the NRA but not disclosed publicly. Hungary and Spain apply a particularly low level of cost transparency, as only the total investment cost is available to the NRA and no cost information is publicly available.

69 ACER reiterates its recommendation that NDPs should include and publish key project information, including technical description, expected commissioning date, investment costs , status, progress since the previous NDP, increase of transport capacity, where relevant. ACER further considers that investment cost information should also be included in the EU TYNDP, as it is essential for assessing and evaluating investment proposals. A C E R O P I N I O N N O 1 7 / 2 0 2 6

2.7. Gas decarbonisation aspects 2.7.1. Programs to phase-out or decrease natural gas demand

70 Phasing out fossil natural gas is a key part of the energy transition. Renewable electricity, renewable and low-carbon gases and energy efficiency measures are expected to replace fossil natural gas demand over time. Figure 5: EU27 Member States with policy measures for gas demand reduction, 2026

71 NRAs from 13 Member States reported the existence of programs or policy measures aimed at phasing out or reducing natural gas demand, relying on measures to electrify the heating sector and improve energy efficiency. Common measures include restrictions on new gas connections and fossil fuel boilers. Others include support for building renovation and renewable heating technologies, modernisation of district heating systems, and broader climate and energy strategies promoting the gradual replacement of fossil natural gas with renewable and low-carbon energy sources. Several Member States have also adopted long-term targets or strategies for reducing natural gas consumption, while some have introduced specific regulatory measures facilitating the gradual decommissioning of gas infrastructure and the transition to renewable gases.

2.7.2. Biomethane injections into gas transmission networks

72 As a sustainable alternative to natural gas, biomethane plays an important role in achieving the EU’s energy transition objectives. The RePowerEU plan sets a target of increasing biomethane production to 35 bcm by 2030, representing a substantial increase compared with current production levels.

73 ACER observes clear progress in biomethane integration over the past two years. The number of NRAs reporting physical biomethane injection into the gas transmission system has increased A C E R O P I N I O N N O 1 7 / 2 0 2 6 from 7 to 10 . Similarly, the number of Member States where gas NDPs include investments to enable or expand the direct injection of biomethane into the transmission network has risen from 7 to 11 . These developments indicate a growing readiness of gas transmission networks to accommodate increasing biomethane production.

74 Compared to 2024, ACER observes no change in the number of Member States where gas network operators are required to prioritise direct injection of biomethane into the gas transmission network. Such an obligation remains in place in 4 Member States. Furthermore, in 11 Member States gas TSOs must provide a connection point for direct biomethane injection upon request by a network user.

75 In ACER’s view, all gas NDPs should include infrastructure investments for biomethane injections to support its integration into the EU’s gas transmission network. In this respect, ACER calls for closer cooperation among TSOs, DSOs and biomethane producers to ensure that network development is aligned with biomethane production growth. Priority access and connection for biomethane injections into gas transmission network, together with appropriate incentives for biomethane production, are important enablers for achieving the EU’s biomethane targets.

2.7.3. Hydrogen blending in gas transmission networks

76 Unlike biomethane, which can be readily accommodated in the existing gas network, hydrogen blending presents a range of technical, operational and economic challenges. These include impacts on the operation of gas infrastructure, the performance of natural gas end-use applications and the interoperability of cross-border gas systems. In light of these challenges, the Regulation recognises hydrogen blending as a measure of last resort, as hydrogen is an expensive commodity.

77 The Regulation leaves freedom to Member States to determine whether hydrogen blending is permitted in their national gas systems and, if so, the maximum blending level. To preserve the functioning of the EU internal market and avoid barriers to cross-border gas trade arising from differences in gas quality, it also establishes a Union-wide dispute settlement mechanism that covering hydrogen blending of up to 2% at cross-border interconnection points.

78 ACER welcomes the significant progress over the last two years of hydrogen injection acceptance into natural gas transmission networks. The number of Member States where such injections are allowed has doubled, with Belgium, Czech Republic, Lithuania, Romania and Slovenia introducing this possibility since ACER’s 2024 assessment. The hydrogen concentration limit range has widened from 0.1% in Latvia to 20% in Germany . More details on the hydrogenrelated developments is provided in Table 31 of the Annex.

2.7.4. Recent and planned hydrogen pipeline developments

79 The EU has set high policy ambitious as regards hydrogen in the EU Hydrogen Strategy, Fit for 55 Package and the updated REPowerEU plan. Demand of 20 million tons of green hydrogen is targeted by 2030, with half expected to be produced in the EU and half imported from outside the EU. Achieving such large-scale hydrogen demand requires a dedicated EU hydrogen pipeline network composed of new dedicated pipelines and repurposed existing gas pipelines transporting pure hydrogen. A C E R O P I N I O N N O 1 7 / 2 0 2 6

80 ACER finds that the EU hydrogen infrastructure remains at an early stage of development. Since 2022, no additional Member States have reported existing hydrogen pipeline systems connecting industrial sites. Such infrastructure is currently in place only in Belgium, Germany, the Netherlands and Spain. In 7 additional Member States, hydrogen pipelines are planned to be developed in the future.

2.8. Consistency of projects in gas and hydrogen NDPs and the EU TYNDP

81 This part of the assessment is based on the draft EU TYNDP 2026 project list published by ENTSOG and the inputs provided by NRAs between April and May 2026.

82 The draft EU TYNDP 2026 project list contains 345 projects classified into four categories, natural gas, hydrogen, smart gas grid and “other”. Table 1 presents the number and share of projects per category. ACER observes a growing representation of hydrogen projects in the EU TYNDP project portfolio. Their share increased from 62 % in the 2024 cycle to 70 % in 2026, while the share of gas projects declined from 29 % to 22 %. A C E R O P I N I O N N O 1 7 / 2 0 2 6

2.8.1. Inclusion of EU TYNDP projects in NDPs

83 Half of the draft EU TYNDP 2026 projects are included in the corresponding NDPs. This continues the broadly stable trend of the planning cycles since 2022, following a marked decline from the higher inclusion rates observed in earlier editions. The inclusion rate is the lowest for hydrogen (38 %) and the highest for natural gas projects (88 %). The relatively low inclusion rate of hydrogen projects may be explained by the limited availability of hydrogen NDPs and the limited incorporation of hydrogen projects in other national plans such as gas NDP. As hydrogen planning framework continues to develop, greater alignment in terms of project inclusion in the EU TYNDP and NDPs can be expected over time.

84 ACER recommends that hydrogen project promoters consult the relevant national authorities before submitting their projects for inclusion in the EU TYNDP. In the absence of dedicated hydrogen NDPs, such engagement can provide valuable input on the relevance of proposed projects and their alignment with national planning strategies.

2.8.2. Consistency of project-specific information in the plans

85 ACER and NRAs reviewed project-specific information in the draft EU TYNDP 2026 project list at an early stage of the EU TYNDP development process. This enabled the NRAs’ views and comments to be communicated to ENTSOG in a timely manner, with the aim of improving the quality of the project data included in the EU TYNDP 2026 and allowing general comments to be addressed at an early stage.

86 Results of the review are provided in Part B of the Annex. They include information on the projects for which comments were provided, the general comments by the NRAs and one identified crossborder relevant planned and NRA-approved project in Austria that has not been included in the draft EU TYNDP project list . ACER calls on ENTSOG and project promoters to duly consider the NRAs’ remarks on draft EU TYNDP 2026 projects, in particular when intended to improve consistency between national and EU-level planning.

3. Conclusions

87 ACER reviewed gas and hydrogen NDPs to assess their consistency with the EU TYNDP, drawing primarily on information provided by NRAs and the draft EU TYNDP 2026 project list. This assessment was conducted before the 5 August 2026 deadline for Member States to transpose the Directive into national law. The findings should therefore be read in the context of the Directive’s ongoing implementation in the Member States.

88 The review identified the following main findings: • While gas network development planning is relatively well established across the EU, hydrogen network planning frameworks remain at an early stage. The governance, including designation and certification of HNOs and the responsibilities of the NRAs continues to evolve through the implementation of the Hydrogen and Decarbonised Gas Market Package. In the meantime, in some Member States, gas TSOs appear to play a central role in hydrogen infrastructure development. A C E R O P I N I O N N O 1 7 / 2 0 2 6 • There is some progress in in the consideration of gas decarbonisation aspects, such as the use of market consultations to assess future hydrogen demand and integration of biomethane and hydrogen into gas transmission systems. • Planning methodologies differ significantly, both across national NDPs, and between national and EU-wide planning, in gas and hydrogen sectors alike. The gap is visible in three aspects: the use of scenarios, the approaches to identify infrastructure needs and the evaluation and presentation of projects in NDPs.

89 ACER finds the NDPs broadly consistent with the EU TYNDP but sees scope to further strengthen their consistency and the robustness and transparency in network planning. The degree of alignment varies across sectors and Member States, reflecting, among other factors, differences in planning frameworks. ACER recommends that the entities responsible for preparing, reviewing and adopting NDPs consider the following recommendations: Institutional framework • Gas and hydrogen NDPs should be prepared on a biennial basis and to the extent possible be time-aligned with the EU TYNDP development process. • The Member States should ensure timely and effective transposition and implementation of Directive (EU) 2024/1788 requirements for NRA oversight, approval and amendment of NDPs under Articles 55 and 78. Planning transparency and consultation • The Member States should ensure the timely and effective transposition and implementation of the consultation and transparency requirements already established by Directive (EU) 2024/1788. Beyond these minimum legal requirements, consultation should also cover key methodological elements, such as infrastructure-needs assessments and cost-benefit analyses, where these are not already subject to consultation. Information on the consultation process and the NRA’s assessment of the NDP should be published. • Market consultations to assess future hydrogen demand should be introduced in the relevant Member States and considered in their NDPs. • Gas and hydrogen NDPs and the EU TYNDP should publish key project information. This includes a technical description, expected commissioning date, investment costs, and status. It should also show progress since the previous edition of the plan, any increase of transport capacity, and cross-refer to the EU TYNDP or NDP project code, as applicable. Cross-border and cross-sectoral coordination • The system operators should strengthen coordination and cooperation, including data exchange, in gas and hydrogen NDP preparation process. • At least the central EU TYNDP scenario should be taken into account when developing scenarios for gas and hydrogen NDPs. Integration of decarbonisation measures • The Member States should ensure timely and effective transposition and implementation of Directive (EU) 2024/1788’s requirements on project inclusion in the gas and hydrogen NDPs. In particular, NDPs should, among others, include key A C E R O P I N I O N N O 1 7 / 2 0 2 6 projects for the decarbonisation of the gas sector, such as decommissioning projects, projects for the repurposing of gas infrastructure for hydrogen and projects for biomethane injections into natural gas transmission system. ENTSOG and project promoters should duly consider ACER’s and NRA’s remarks on draft EU TYNDP 2026 project list for the finalisation of the draft EU TYNDP 2026. Done at Ljubljana, on 28 September 2026. — SIGNED — V. ZULEGER, ACER Director ad interim Annexes: • Annex I: Part A - National practices in natural gas and hydrogen network development plans Part B – Results of the consistency check of projects in the EU TYNDP and NDPs