SHERIDAN, WYOMING - March 31, 2026 - Gas shippers and large energy users in Slovakia face a tougher tariff-planning environment in 2026 because ACER has found that key elements of the country's proposed gas transmission pricing framework cannot yet be confirmed as aligned with EU tariff rules, creating potential changes to cost recovery, cross-border trade conditions, and final regulatory decisions. ACER's report reviews the reference price methodology proposed by Eustream, Slovakia's transmission system operator, for the 2026-2027 multi-year tariff period and sets out where the Slovak regulator ÚRSO should tighten the approach before adoption.
What ACER reviewed
The proposal would replace the current methodology and introduce new tariffs in the middle of the ongoing tariff period. Eustream said exceptional circumstances, specifically a large drop in cross-system flows, justify the change. The package also includes a tariff increase of more than 70%, making the review material for network users that rely on predictable transmission charges for contracting and route economics.
Eustream proposed a uniform postage stamp reference price methodology with an ex-ante entry-exit split for 2026-2027. It also proposed to continue recovering transmission revenues through a combination of capacity-based charges, paid for reserved network capacity, and commodity-based charges linked to transported gas volumes. Capacity tariffs at all entry and exit points, including domestic points, would be adjusted through benchmarking intended to lower tariffs and improve competitiveness, using a broad set of European transmission system operator tariffs, including tariffs from Northwestern Europe, as reference points.
Where ACER found non-compliance risks
ACER concluded that the proposal meets the EU requirement on non-discrimination, but it could not confirm compliance with transparency, cost-reflectivity, avoidance of cross-subsidisation, volume risk management, and prevention of cross-border trade distortions. The agency tied those concerns mainly to the proposed benchmarking adjustment, stating that the approach does not meet the standards set by the EU Network Code on Harmonised Transmission Tariff Structures.
ACER also found the proposed commodity-based charges non-compliant. The Slovak framework would retain two such charges: a flow-based charge paid in kind, where part of the transported gas is used to cover the fee, and a complementary revenue recovery charge linked to the Slovakia-Poland gas interconnector. The specific compliance issue identified by ACER is that the flow-based charge is adjusted by a discount for domestic flows, which EU rules do not allow.
Business impact
Procurement leads at gas suppliers and industrial energy buyers now need to model 2026 transport costs against more than one regulatory outcome, because ÚRSO may have to narrow or revise the benchmarking method before final approval. That affects budget cycles, route selection, and contract pricing, especially for companies exposed to Slovak entry and exit points or using the network for regional transit. Supply chain and trading teams should also reassess assumptions tied to domestic-flow discounts, since ACER has recommended phasing out the non-compliant reduction in the flow-based tariff.
Regulatory affairs teams and operations directors at shippers, storage operators, and cross-border traders face a second decision layer: whether the final tariff design will preserve predictable cost signals at points where actual pipeline competition exists, or whether a broader benchmark set will be curtailed. ACER's recommendation to limit benchmarking adjustments to points with clearly identified competition raises the importance of point-by-point economics rather than systemwide averages. For businesses using the Slovakia-Poland interconnector, the treatment of the complementary revenue recovery charge also remains relevant to cross-border sourcing and long-term network planning, because the final methodology will shape how interconnector-related costs are recovered during the 2026-2027 tariff period.