According to the Aggregated Gas Storage Inventory (AGSI), the pan-European gas storage platform, as published on the Energy Map portal, 11.01 bcm of gas was stored in the Ukraine’s underground gas storage (UGS) facilities as of the end of the gas day on 30 September. Including 4.64 bcm of long-term stored gas, total gas stocks amounted to 15.65 bcm.
This figure was nearly 1.1 bcm (7.2%) above the baseline target of 14.6 bcm set by the Ministry of Energy for the start of the heating season.
Long-term stored gas comprises 942 mcm of gas that Ukrtransgaz transferred to fixed assets between 2022 and 2025 and used as cushion gas, as well as 3.7 bcm of working gas stored in UGS facilities to compensate for the shortage of cushion gas. These figures are based on Ukrtransgaz’s 2025 financial statements.
In September, 0.91 bcm of gas was injected into UGS facilities, 25.8% less than in August 2026 and 41.1% less than in September 2025.
The average daily injection rate in September was 30.4 mcm. This was 0.6% below the average rate for the 2026 injection season (30.6 mcm) and 22.7% below the average rate for the 2025 injection season (39.4 mcm).
The significant difference in injection volumes between 2025 and 2026 was mainly due to the substantial volumes of gas imports in 2025, which have been almost absent this year. This is clearly evident from the data on physical gas flows entering Ukraine’s gas transmission system (GTS): in April–September 2025, these flows amounted to 3.57 bcm, compared with 0.23 bcm over the same period this year.
The start of the injection season is defined as the first day of three consecutive days on each of which net injections (injections minus withdrawals) exceed 1 mcm, provided that net injections remain positive for the following seven days. Under this criterion, the 2026 injection season began on 11 March, while the 2025 injection season lasted from 17 April to 3 November.
The main reason for the significant decline in gas injections in the second half of September was the re-export of gas previously injected into Ukrainian UGS facilities in the customs warehouse regime. The re-export is evidenced by the emergence of significant commercial gas flows out of Ukraine’s GTS to Hungary and Poland. According to data from the Gas Transmission System Operator of Ukraine (GTSOU), the significant increase in gas transmission volumes along these routes coincided with a decline in gas injections in storage facilities. Commercial gas flows to Hungary amounted to 118 mcm during 18–30 September, i.e. the period of the sharp decline in injection volumes, of which 116.1 mcm was transported under the customs warehouse regime. In contrast, no gas was re-exported to Hungary during 1–17 September.Commercial gas flows to Poland totaled 39.3 mcm during 18–30 September, with the entire volume transported under the customs warehouse regime. During 1–17 September, the corresponding volume was 1.5 mcm.
The decrease in gas injection volumes is linked to the use of virtual gas exchange operations provided under the Gas Transmission System Code. Under this mechanism, instead of physically withdrawing gas stored in UGS facilities under the customs warehouse regime and intended for re-export, physical injection volumes are reduced by an amount equivalent to the corresponding re-export flow in the opposite direction. The gas remains in storage, but ownership changes. According to industry experts, these re-export operations are carried out by companies of Naftogaz Group.
* To convert energy units (TWh, GWh) into volume units (bcm, mcm), a conversion factor of 10.595 kWh/m³ was used.
For days for which the data administrator did not provide injection data for the gas day, linear interpolation was used (the arithmetic mean of the injection figures for the days immediately preceding and following the date for which data was unavailable).