The U.S. Energy Information Administration estimated that working gas in underground storage across the Lower 48 states was 3,415 billion cubic feet (Bcf) as of September 25, 2026, in a report released October 1. The net weekly increase was 64 Bcf. Stocks were 138 Bcf below the same week a year earlier and 79 Bcf above the 2021–25 five-year average. These are weekly stock estimates, not production or consumption flows.

Working gas is the volume that can be withdrawn from storage, excluding cushion gas that remains in a facility. EIA reports totals for the Lower 48 and separately for the East, Midwest, Mountain, Pacific and South Central regions. Regional figures can differ slightly from the national total when added because of independent rounding. That note is part of how to read the table and should not be mistaken for evidence of a data error.

The regional picture was uneven. East stocks were 840 Bcf, 4.6% above their five-year average; Midwest stocks were 984 Bcf, 2.9% above. South Central held 1,048 Bcf, 2.4% below its average, and inventories in salt caverns there were 15.5% below their five-year average. Pacific stocks were 8.9% above average and Mountain stocks 6.4% above. A national surplus does not mean every market had the same cushion.

The report estimates weekly inventory changes using a survey and publishes a coefficient of variation and standard error to describe sampling uncertainty. The coefficient of variation for total stocks was 0.4%, and the standard error for the net weekly change was 0.7 Bcf. Those measures do not erase the estimated 64 Bcf injection, but they show that reported levels are not exact meter readings. The degree of uncertainty also varies across regions.

The weekly estimate describes storage entering the final part of the autumn injection season before winter heating demand. Inventories change with weather, production, pipeline flows, LNG exports and power-sector demand. A single week’s high stock relative to average does not prove winter prices will decline or that every region will have excess supply. EIA’s October 1 report measures conditions on Friday, September 25; its release date is not the observation date.

Market participants can compare the estimate with the prior week, year-earlier level and five-year seasonal average. These answer different questions: the weekly change tracks near-term injection, the annual comparison places stocks against the previous season, and the five-year comparison shows their seasonal position. None is a price forecast by itself. The main analytical point is that national stocks exceeded average while South Central, especially salt-cavern storage, remained below its benchmark.