Flexibility and grids: understanding available grid capacity, connection queues and what can be done

The development of electricity grids and the flexibility needs of an electricity system are deeply interlinked. When grids expand too slowly and become congested, network flexibility needs tend to increase. Grid constraints can also affect system flexibility needs when they lead to the curtailment of intermittent renewable generation or limit the participation of flexibility providers through prequalification.[1] A lack of transparency in available grid capacity might further complicate this interaction. Finally, grids can delay the achievement of flexibility targets when new flexibility service providers are waiting in grid connection queues.

In this instalment, we look at the interaction between grids and flexibility from three angles. First, we describe how information on available grid capacity is currently shared with end‑users. Second, we discuss why bottlenecks may arise not only from physical capacity limitations but also from grid connection processes themselves. Finally, we provide a high-level overview of the approaches that can be considered to address grid capacity constraints and grid connection queues.

Transparency on available grid capacity

A recent study by Fraunhofer for the European Commission states that, although grid congestion is starting to emerge as a challenge for system operators, most Member States have not yet experienced systemic congestion issues at the national scale.[2] At the same time, transparency on network constraints and grid availability is increasing across Europe. This trend is linked to the provisions of the Electricity Market Design reform, which require distribution and transmission system operators to ‘publish in a transparent manner clear information on the capacity available for new connections in their area(s) of operation’. [3]

To fulfil these requirements, system operators are increasingly developing hosting capacity maps to indicate areas with available grid capacity in their networks. These maps show not only where new (flexible) users may be able to connect without delay, but also where congestion is already present and flexibility could be particularly valuable. In practice, however, the design and features of these hosting capacity maps are currently very diverse. Differences can be observed, for example, in colour codes, granularity, user groups, interaction between system operators, and the consideration of congestion management tools or future grid investments.[4] In addition, system operators may apply different approaches when calculating available grid capacity. In a recent FSR working paper, we identified seven factors where different assumptions might be applied, and we qualitatively assessed the potential impact of overlooking these factors on the calculation of available grid capacity (i.e. whether there is a tendency to over- or underestimate it). Finally, it is worth noting that, as part of the Grid Action Plan, the EU DSO Entity and ENTSO-E are developing a portal on grid hosting capacities, where links to all hosting capacity websites, supporting definitions and good practices will be shared.[5]

Bottlenecks arising from grid connection processes

Beyond grid capacity, grid connection processes are increasingly becoming a bottleneck for new flexibility providers to start delivering their services. It is important to note that these queues do not necessarily depend on the physical availability of network capacity. When no grid capacity is available, new requests naturally enter a queue. However, queues can also arise in areas where remaining capacity exists when the number of connection requests grows faster than system operators can process them.

The aforementioned study by Fraunhofer for the European Commission reports that at least 15 Member States already face problems with grid connection queues at distribution level. Similar observations appear in a report by BCG, which compares the size of connection queues for demand, generation and storage projects at transmission level across different regions of the world. Three notable cases discussed in this report are Italy, the United Kingdom and Finland, which have queue sizes that are approximately 12, 15 and 30 times larger than their respective national peak loads in 2024. Beyond illustrating that queue problems can be significant, these figures also point to another issue associated with grid connection procedures: the presence of speculative or immature applications, also called “zombie”, “ghost” or “paper” projects. This challenge was also acknowledged in the European Commission’s Guidance on efficient and timely grid connections, which was published as part of the European Grids Package.

Approaches to address grid capacity constraints and grid connection bottlenecks

Several approaches can be considered to address the bottlenecks described above. Broadly, these measures fall into two categories: ensuring sufficient grid capacity and establishing efficient grid connection procedures. The former can reduce both grid congestion and the length of connection queues, while the latter primarily targets the processing of applications within the queue.[6]

Ensuring sufficient grid capacity involves both making better use of existing infrastructure and enabling efficient and timely buildout of new infrastructure. Existing grid capacity can be used more efficiently through grid tariff incentives, flexible connection agreements, congestion management (i.e., local flexibility markets) and releasing reserved but unused grid capacity. In parallel, the efficient and timely buildout of new infrastructure can be enabled through a combination of reduced deployment times, more coordinated and forward-looking network planning and anticipatory investments. It must be noted that uncertainty around how the perceived risks of anticipatory investments should be mitigated and shared seems to remain a barrier to their widespread deployment. The Commission’s Guidance on anticipatory investments can be seen as a first step towards creating more favourable conditions at Member State level.

Establishing efficient grid connection procedures involves both managing the size of the queue and revisiting the queue evaluation process. Measures to manage the queue size include introducing fees, milestones or maturity criteria to reduce speculative behaviour, removing invalid applications from the queue, and ensuring capacity requests reflect realistic project needs. In addition, the process of evaluating applications can be accelerated through deadlines, standardisation, digitalisation and targeted exceptions. Finally, the order in which connection requests are processed is also increasingly under discussion. The Commission’s Guidance on efficient and timely grid connections, for example, provides an overview of alternatives to the first‑come‑first‑served principle that Member States can consider.

[1] A more detailed description of network and system flexibility needs can be found in the first instalment of this Topic of the Month: https://fsr.eui.eu/flexibility-in-power-systems-whats-there-beyond-the-buzzword/.

[2] More specifically, the study gathers data and compares practices from all 27 EU Member States through desk research and interviews, focusing on distribution grids and covering: 1) network planning, 2) network tariff design and regulatory incentives, and 3) treatment of grid connection requests.

[3] See Regulation (EU) 2024/1747 Article 50 on the requirements for transmission system operators and Directive (EU) 2024/1711 Article 31 on the requirements for distribution system operators.

[4] For a more detailed comparison of grid hosting capacity maps across Europe, see for example Eurelectric (2023), “Power System of the Future: Keys to delivering capacity on the distribution grid”, available at https://www.eurelectric.org/wp-content/uploads/2024/06/report-block-1_part-1-grid-capacity_final-draft_3082023.pdf; Ember & RAP (2024), “Transparent Grids for All. Grid(un)lock: Hosting Capacity Maps”, available at https://ember-energy.org/latest-insights/transparent-grids-for-all/; and European Commission & Fraunhofer (2025), “Study on network development planning, tariff structures and connection requests for electricity distribution grids”, available at https://data.europa.eu/doi/10.2833/9351025.

[5] For more information, see https://www.entsoe.eu/grid-action-plan-on-hosting-capacities/.

[6] However, grid connection queue management tools could in some cases also address grid congestion, for example, if flexible resources that can mitigate grid congestion get priority treatment in the queue.