Slovakia – November 03, 2026 -- The EU Agency for the Cooperation of Energy Regulators (ACER) has found that Eustream's proposed gas transmission tariffs, which would raise charges by more than 50% midway through the current tariff period, do not comply with the EU Network Code on Harmonised Transmission Tariff Structures (NC TAR).
Eustream cites collapse in cross-system flows for mid-period change
Eustream, Slovakia's transmission system operator, proposed a new reference price methodology and tariffs for January 2026 to December 2027. The operator pointed to exceptional circumstances, specifically a large drop in cross-system flows. The plan combines a uniform postage stamp methodology with an ex-ante entry-exit split.
Revenue would continue to come from capacity-based charges and commodity-based charges. Eustream would adjust capacity tariffs at all entry and exit points, including domestic ones, by benchmarking against a wide set of European operators, including those in Northwestern Europe. The aim is to lower tariffs and make them more competitive.
Slovak regulator cut tariffs in April, then ended the procedure on 8 October
In April, Slovak regulator ÚRSO approved lower tariffs than Eustream had proposed, to apply from 1 May 2026. On 30 June, Eustream launched a new consultation proposing the same tariffs as before, with only minor methodological changes. ÚRSO discontinued the tariff proposal procedure on 8 October 2026, which also ended the methodology proceeding. A 40-day appeal period applies. ACER said the discontinuation does not release it from its obligation to publish the analysis.
ACER cannot confirm five compliance criteria and rejects commodity charges
ACER's findings remain largely unchanged from its February 2026 report. The proposal meets the non-discrimination requirement. ACER could not confirm compliance on transparency, cost-reflectivity, avoidance of cross-subsidisation, volume risk and prevention of cross-border trade distortions. It attributes this mainly to the benchmarking adjustment, which falls short of the network code's standards.
The proposed commodity-based charges are non-compliant. Eustream would keep two: a flow-based charge paid in kind, and a complementary revenue recovery charge meant to help recover the costs of the Slovakia-Poland gas interconnector. ACER objects to the discount for domestic flows applied to the flow-based charge, which EU rules do not allow.
ACER sets three conditions should ÚRSO resume the procedure
If the procedure resumes, ACER recommends that ÚRSO limit benchmarking adjustments to points with clear pipeline competition, so tariffs reflect market conditions and stay predictable for network users. It also recommends measures to improve alignment with the network code despite current obstacles to full compliance, and a phase-out of the non-compliant flow-based tariff discount.