Hungary is on track to exceed the EU gas storage obligation and to meet its national filling requirements this year, even if injections only match last year's pace.
Hungary has a derogation from the EU's storage rules that reduces its filling target to 35pc of five-year average demand instead of 90pc of working gas capacity, which trims its mandatory storage obligation to around 35TWh, or roughly 51pc of capacity, for some point between 1 October and 1 December. This means that Hungarian inventories will need to rise by under 11.5TWh to meet the EU filling obligations. Hungarian stocks of 23.7TWh as of Tuesday morning were at 35pc of capacity, below 26.1TWh on the same day a year earlier (see Hungarian stocks graph).
Assuming that the average injection rate equals last year's 136 GWh/d over the remaining 160 days of the injection season, Hungarian stocks would reach 45.5TWh by 1 October. This would be 4.3TWh lower than a year earlier, but 10.5TWh above the EU's minimum requirement for this year.
National storage obligations may accelerate stockbuilding earlier in the injection season by setting earlier mandatory deadlines. Hungarian law obliges different market participants to build storage reserves in domestic facilities.
Hungarian gas system operator FGSZ must ensure that 2.1TWh of gas is injected into domestic storage by 1 July. Universal service provider state-owned utility MVM, which supplies households, must hold 19.8TWh in Hungarian storages by 1 October. And trading firms active on the domestic market must hold storage volumes equal to 2pc of their contracted supply for the 2026–27 gas year. Trading firms must notify Hungarian energy regulator Mekh of how they will comply with this storage obligation by 1 May. Failure to comply may result in a procedural fine or criminal liability, making national regulations stricter than EU legislation.
Hungarian exports to Ukraine totalled 15.4TWh in May-September 2025, but flows towards Ukraine have been low in recent months. If this volume remains in the domestic market and is directed entirely to storage, end-of-season stocks could exceed 60TWh by 1 October, representing about 90pc of technical capacity and aligning with the EU's baseline storage target. This suggests that demand from neighbouring markets could have a significant impact on Hungarian stockbuilding this summer.
Inverse storage demand returns
An inverted forward curve and changing market conditions have made gas loan services attractive, a market participant told Argus.
State-owned storage operator HGS offered inverse storage services — under which market participants can use operator-owned gas for a fee, with volumes to be returned later during the agreed period — for October 2026–September 2027 in March, the operator told Argus. The full 1.2TWh on offer was booked, representing the maximum volume permitted under the operator's licence, HGS said.
This was the first inverse auction since summer 2025, because backwardation in the forward curve — with prompt prices at a premium to futures — is a precondition for the product to be economically attractive, HGS said. Only operators with regulatory approval may provide the inverse storage service, using their own working gas volumes reclassified from cushion gas.
A positive summer-winter spread encouraged the use of these services this spring. "We used this option in Hungary and Slovakia," a market participant told Argus.
Slovak gas storage operator Nafta offered 2TWh of inverse storage capacity for various delivery periods between 2026 and 2029 in March and April. No information on the auction results or fees is publicly available, according to a market participant.
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