Capacity Calculation Region (CCR) · Glossary

A Capacity Calculation Region, or CCR for short, is called "Kapazitätsberechnungsregion" in the German version of EU law. The CACM Regulation (EU) 2015/1222 defines it as the geographical area in which coordinated capacity calculation is applied. Within such a region, the participating transmission system operators (TSOs) use common methodologies to determine how much cross-zonal capacity can be made available for electricity trading between neighbouring bidding zones. The term comes from European electricity market law. It is closely linked to market coupling, congestion management and coordinated security analysis.

A CCR groups together several bidding zones, their borders and the responsible transmission system operators. It is not a separate physical grid region. What matters is which bidding zone borders influence each other when trade flows occur. In a meshed alternating current grid, electricity does not follow the contractually agreed trading route but spreads according to the electrical properties of the lines. A transaction between two bidding zones can therefore load lines in a third zone. Such unscheduled flows are called loop flows. It is precisely because of these interactions that a coordinated calculation is needed instead of many separate individual calculations at each border.

What "capacity" means here

Capacity here does not mean the output of power plants. It refers to cross-border transmission capacity for trading. It is expressed in megawatts and determines how much electricity market participants may exchange between bidding zones without endangering grid security. This capacity is not a fixed value like the rated capacity of a line. It depends on load, generation, switching states, planned outages, safety margins and assumed contingencies. It is therefore recalculated repeatedly for different market time frames, for example for the day-ahead market and the intraday market. Under the CACM Regulation, the TSOs of each region must recalculate cross-zonal capacity within the intraday time frame on the basis of the latest available information.

Legal basis and determination of the regions

The basis is the CACM Regulation (EU) 2015/1222 of 24 July 2015. It is one of the European network codes and guidelines and governs capacity allocation and congestion management in the day-ahead and intraday time frames. Under Article 15, all TSOs had to develop a joint proposal for determining the regions. Two allocation rules apply: each bidding zone border belongs to exactly one CCR. Each TSO belongs at least to all regions in which it has bidding zone borders. A grid operator can therefore belong to several CCRs. This applies, for example, to operators whose grid has borders in different regions.

The regions are therefore not freely chosen by individual grid operators. Their determination must be approved by the authorities. The first determination was made in 2016 by a decision of the EU regulatory agency ACER. It has been amended several times since. ACER Decision 04/2021 of 7 May 2021 recast the determination that applied until then. Further amendments followed. Among other things, they included Norwegian borders in the Nordic and Hansa regions and created the Central Europe region. In it, the Core and Italy North regions are initially merged for day-ahead capacity calculation. After each approval, the TSOs of a region must submit common methodologies, for example for capacity calculation and for coordinated redispatching and countertrading.

Current configuration (status according to ACER, December 2025)

In December 2025, ACER named nine CCRs in the EU: Nordic, Hansa, Core, Italy North, Central Europe (CE), Greece-Italy (GRIT), South-West Europe (SWE), Baltic and South-East Europe (SEE). With Decision 10/2025, ACER approved further amendments. Core and Italy North are to be merged in the Central Europe region no longer only for day-ahead. This is joined by intraday capacity calculation, regional coordination of operational security, and coordinated redispatch and countertrading including cost sharing. In addition, the South-East Europe region was extended. The regions East-Central Europe, Italy-Montenegro and Eastern Europe were newly created. They incorporate borders and TSOs of the Contracting Parties of the Energy Community and neighbouring EU states. East-Central Europe is regarded as a transitional solution and is later to be absorbed into Central Europe. For Germany, the Core CCR is particularly important, in which capacity is calculated on a flow-based basis.

How the joint calculation works

The TSOs of a region calculate using a common grid model. It contains forecast generation and load, the grid topology, planned unavailabilities and operational limits. On this basis, it is checked how much trade is possible without overloading a network element. This also applies in the event that a relevant piece of equipment, such as a line or a transformer, fails. This principle is known as the N-1 criterion. For forecast uncertainties, a reliability margin is deducted. The CACM Regulation defines it as a reduction of cross-zonal capacity intended to cover uncertainties in the capacity calculation. In addition, each TSO can determine which remedial actions, such as switching measures, are included in the calculation.

There are two basic approaches to the calculation. In the coordinated net transmission capacity (NTC) approach, a tradable maximum value is set for each bidding zone border. This is easy to grasp, but only represents the interactions in highly meshed grids roughly. In flow-based capacity calculation, by contrast, it is calculated for critical network elements how strongly zonal trading positions affect them. The market then optimises within these limits. In regions with closely coupled power flows, such as parts of continental Europe, this method represents the physics more accurately but is harder to follow.

Minimum capacity for trading: the 70 percent target

In addition to the CACM methodologies, Article 16(8) of the Electricity Market Regulation (EU) 2019/943 applies. Under it, TSOs may not arbitrarily limit the capacity made available for trading in order to resolve internal congestion. They must make available for cross-zonal trade at least 70 percent of the capacity of critical network elements, respecting security limits and taking contingencies into account. At most 30 percent may be used for reliability margins, loop flows and internal flows. This applies to both the NTC approach and the flow-based approach. The requirement has been binding since 1 January 2020. Member States were allowed to reach the values gradually until the end of 2025 through action plans or derogations. The 70 percent is a lower limit and not a maximum.

Distinction from related terms

Bidding zone: an area with a uniform wholesale price, provided that no congestion is represented within the zone. Germany and Luxembourg, for example, form a joint bidding zone. A CCR comprises several bidding zone borders and calculates the capacity between the zones.
Control area or grid area: the area of responsibility of an individual grid operator. The CCR, by contrast, is a coordination area of several TSOs. It does not replace their operational responsibility. Each TSO remains responsible for the security of its grid but must coordinate assumptions and procedures regionally.
Capacity market: a capacity market remunerates secured generation or load reduction capacity. It has nothing to do with the transmission capacity at issue in a CCR. Only the word "capacity" is the same.

Why CCRs matter for the electricity market

The European internal market is meant to have electricity generated where it is cheapest overall, as long as the grid remains secure. For this, capacities between bidding zones must be determined reliably and without discrimination. If they are calculated too cautiously, trade remains unused. Price differences between zones then remain larger, more expensive power plants run more often and renewable electricity is harder to integrate. If they are set too generously, the TSOs have to intervene after market closure with redispatch or countertrading. This causes costs, the distribution of which between countries can be contentious because the cause and effect of a congestion are often not in the same country. ACER therefore stresses that well-designed regions should improve the coordination of these processes and optimise trading capacity.

As the share of wind and solar power grows, regional capacity calculation becomes more important. High wind feed-in in the north, solar peaks in the south, power plant outages or load peaks can shift flows in the transmission grid quickly and over large areas. The calculation cannot predict these states exactly. But it must make robust assumptions and limit risks in a traceable way.

Typical misinterpretations

"Capacity is a political quota": Minimum requirements such as the 70 percent target set lower limits. The concrete value, however, results from a grid calculation under security conditions. Low values can be due to real congestion, safety margins, planned outages or methodological assumptions.
"A CCR eliminates congestion": A CCR calculates and coordinates. It does not build lines and does not shift bidding zone borders. It can make structural congestion visible and treat it uniformly. It is resolved by other instruments such as grid expansion, a different bidding zone configuration, flexible loads or storage.
"The values are exact": Capacity values act like hard figures in the market process. But they are based on forecasts and model assumptions. Their quality depends on data exchange, on the consistency of the grid models and on how uncertainty is handled.

Placement within congestion management and governance

In the CCR, two requirements are put into practice. The market needs clear capacity values so that bids can be coupled between bidding zones. Grid operation needs security limits so that trading does not create impermissible line loadings. Institutionally this is demanding, because several TSOs, national regulatory authorities, ACER and market processes work together. The interests of the countries continue to differ, for example regarding export possibilities, transit flows or redispatch costs. The joint methodology does not resolve these conflicts politically. But it forces assumptions, margins and calculation steps to be handled openly and in a coordinated manner. For understanding congestion management, the CCR is therefore central. This is where physical grid limits are translated into tradable market limits. A CCR is neither an additional electricity market nor a grid of its own, but the coordinated area in which this translation takes place.

Sources

Verordnung (EU) 2015/1222 der Kommission vom 24. Juli 2015 zur Festlegung einer Leitlinie für die Kapazitätsvergabe und das Engpassmanagement (CACM) — Europäische Union, EUR-Lex; 2015-07-24. Art. 2 Nr. 3 und Nr. 14, Art. 9, Art. 14, Art. 15, Art. 20, Art. 21, Art. 35
Europe reshapes capacity calculation regions to improve cross-border power flows — ACER (Agency for the Cooperation of Energy Regulators); 2025-12-17. Abschnitte „What are capacity calculation regions“, „What did ACER decide?“, „Next steps“
ACER Decision on the determination of capacity calculation regions: Annex I (ACER Decision 04/2021) — ACER; 2021-05-07. Präambel/Erwägungen zur Historie der Festlegung
ACER Recommendation No 01/2019 on the implementation of the minimum margin available for cross-zonal trade pursuant to Article 16(8) of Regulation (EU) 2019/943 — ACER; 2019-08-08. Erwägungen zu Art. 16 Abs. 8 lit. a und b
ACER Decision 11/2022 on alternative bidding zone configurations — ACER; 2022-08 (genaues Datum unbekannt). Abschnitt zum 70-%-Mindestziel, Fußnote 9

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Edited by eCMS on 11.11.2026 16:45