Grid bottlenecks hinder electricity trading

09.09.2025

Source: E & M powernews

The EU agency Acer criticizes the expansion of the electricity grid. Many countries have not reached the target of providing 70 percent of their transmission capacity for cross-border trade.

The Agency for the Cooperation of European Energy Regulators (Acer) published its monitoring report for 2025 on electricity capacities and congestion management in Copenhagen on September 8. Acer Director Christian Zinglersen presented the results at the informal meeting of the Energy Ministers of the Council under the Danish Presidency in Copenhagen.

The report focuses on the legally prescribed 70 percent rule from the 2019 Clean Energy Package, which obliges European transmission system operators (TSOs) to make at least 70 percent of their physical transmission capacity available for cross-border electricity trading by the end of 2025. According to Acer, this is intended to prevent price peaks, reduce barriers to trade and facilitate the integration of renewable energies.

According to the agency, grid operators have only made limited progress to date. In the so-called core region, TSOs had only provided an average of 54% of the available capacity on the most heavily loaded lines in 2024. This means that the deadline of the end of 2025 is at risk of not being met. "The 70 percent rule is crucial to increase the resilience of the electricity supply and to better connect the markets," the report warns.

580 million euros wasted

The analysis also shows concrete economic effects: If the grid operators had met the 70 percent target in 2024, additional welfare gains of at least 580 million euros would have been possible in the core region alone. In addition, implementation could have avoided around half of the most severe price peaks in south-eastern Europe in the summer of 2024.

According to Acer, only the Czech Republic and Slovenia already meet the 70% target. The worst performers are Romania with only 33 percent and Austria with 37 percent of its grid capacity for international electricity trading.

In order to eliminate bottlenecks, the grid operators resorted to remedial measures such as redispatching in 2024. According to Acer, they spent around 4.3 billion euros to redirect around 60 billion kWh - a volume comparable to Austria's annual consumption. The costs for these interventions therefore continued to rise.

Acer's recommendations

Acer recommends that member states prioritize investments in grid expansion and non-wire alternatives such as flexible load control. In addition, TSOs and nominated electricity market operators (NEMOs) should improve their methods for calculating and allocating capacities. Finally, the full implementation of the EU framework for congestion management is necessary in order to coordinate grid congestion more efficiently.

In addition to the analysis, Acer published an interactive dashboard that breaks down data on cross-border electricity trading, congestion costs and progress on the 70 percent rule. The agency emphasizes that greater market integration is crucial to integrate the growing amounts of renewable energy into the grids and further reduce the EU's dependence on fossil imports.

Dividing up the German electricity bidding zone

Germany has only opened up 50 percent of its grid capacity for cross-border trading because grid expansion is progressing too slowly. Acer therefore advocates splitting the single Germany-Luxembourg bidding zone into five bidding zones. This should significantly reduce congestion in the grid areas.

The EU's aim is to decarbonize its electricity supply system and reduce its independence from fossil fuel imports. This process could be accelerated by the new grid infrastructure both within and across national borders. In addition to the electricity grids, electricity generation from renewable sources must also be doubled by 2030, according to the EU target.

The Acer Report 2025 is available for download as a PDF.

Author: Susanne Harmsen