Weekly Storage and S/D Brief - Week Ending 9/18/2026

Week Ending September 18, 2026

SynMax Analytics | Published September 23, 2026

Headline

SynMax models a +54 Bcf injection for the week ending September 18, up 10 Bcf from the prior week's EIA-reported +44 Bcf build and a fresh seasonal high. As in the prior week, the loosening is demand-led: total demand fell -2.30 Bcf/d WoW to 111.55 Bcf/d as power burn retreated -1.90 Bcf/d to 44.05 Bcf/d, with cooling demand fading deeper into the shoulder season. Supply eased more modestly (-0.66 Bcf/d to 119.32 Bcf/d) as dry gas production slipped -0.48 Bcf/d to 112.37 Bcf/d and Canadian pipeline imports gave back -0.18 Bcf/d to 6.95 Bcf/d. The daily surplus widened to 7.73 Bcf/d. If confirmed, working gas storage would stand at 3,352 Bcf, 147 Bcf below last year's pace but a comfortable +109 Bcf (+3.4%) above the five-year average.

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Model accuracy: Across the full window since July 3 (ten weeks, CONUS), the SynMax storage-number model has averaged a mean absolute error (MAE) of 2.9 Bcf, with a small positive (over-injection) bias of +1.3 Bcf.

The accuracy table reflects the latest SynMax supply and demand models and may differ modestly from the official weekly storage-number call scored directly against EIA releases.

Primary Driver: Cooling Demand Fades Further into the Shoulder Season

The defining feature of the week ending September 18 was a continued pullback in cooling demand. Total demand fell -2.30 Bcf/d WoW to 111.55 Bcf/d, led by a -1.90 Bcf/d decline in CONUS electric power burn to 44.05 Bcf/d as national cooling degree days rolled further into the shoulder season. National population-weighted CDDs eased to 9.2 from 10.9 the prior week.

The retreat rotated south and west this week. Power burn fell hardest in the South Central (-1.23 Bcf/d to 13.74) as Texas and Gulf Coast heat finally relaxed, and in the Pacific (-1.01 Bcf/d to 2.40). By contrast, the East (+0.45 Bcf/d to 18.30) and Midwest (+0.10 Bcf/d to 6.09) firmed slightly as a brief late-season warm-up lingered across the Mid-Atlantic and Great Lakes. Despite the WoW decline, national power burn still ran a solid +2.95 Bcf/d above the year-ago 41.11 Bcf/d, confirming cooling load remains ahead of last year even as it fades.

On the supply side, the picture eased modestly. Total gross supply slipped -0.66 Bcf/d to 119.32 Bcf/d as dry gas production edged down -0.48 Bcf/d to 112.37 Bcf/d off its summer high and Canadian pipeline imports gave back a further -0.18 Bcf/d to 6.95 Bcf/d. With demand falling more than three times as fast as supply, the weekly balance loosened further and the injection climbed to a fresh seasonal high.

Weather Context

National population-weighted CDDs averaged 9.2 for the week ending September 18, down from 10.9 the prior week but still above the year-ago 7.4:

• National cooling demand faded week-over-week as the last of summer's heat broke across Texas and the West, pulling the national CDD count into single digits
• The cooldown was concentrated in the South and West this week (South Central and Pacific led the retreat), while the East and Midwest held marginally warmer
• Year-over-year, the +1.8 CDD gap (9.2 vs 7.4) continues to map onto the +2.95 Bcf/d YoY increase in power burn, keeping cooling load ahead of last year despite the seasonal fade

Supply & Demand Factor Changes (WoW)

Note: Canadian pipeline imports are treated as a supply source; Canadian pipeline exports are treated as demand (gas leaving the domestic market). The Balancing Factor captures the residual between independently modeled supply and demand components and is reported below the totals — it is folded into the implied change but excluded from Total Supply and Total Demand.

Secondary Factors

Res/Com: A Modest Bullish Offset

Combined Res/Com demand ticked up +0.35 Bcf/d to 8.62 Bcf/d as early-season heating load stirred in the northern tier — the largest bullish (tightening) mover of the week outside of production. Even so, its gain was far too small to offset the ~1.9 Bcf/d collapse in power burn, and the net demand picture loosened sharply.

LNG Feedgas, Mexico Exports & Industrial

Total LNG feedgas eased -0.34 Bcf/d to 19.06 Bcf/d off the prior week's high as Gulf Coast terminals dipped from full utilization, a bearish (loosening) factor. Pipeline exports to Mexico softened -0.17 Bcf/d to 6.95 Bcf/d as cross-border cooling demand cooled. Industrial demand was flat at 22.01 Bcf/d, a non-factor in the weekly balance.

Regional Power Burn

The heat rotated out of the South and West this week: the South Central and Pacific together shed more than 2 Bcf/d of power burn as Texas and Western heat relaxed, while the East and Midwest firmed marginally. Every region except the Pacific still ran at or above year-ago levels, holding the CONUS YoY gain at +2.95 Bcf/d.

Methodology & Data Sources

Storage change is modeled as Total Supply (Dry Gas Production + Canadian Pipeline Imports + LNG Imports) minus Total Demand (all consumption sectors + LNG feedgas exports + pipeline exports), with the Balancing Factor added as a calibration residual, multiplied by seven days. The EIA storage week runs Saturday through Friday (the week ending September 18 covers Saturday September 12 through Friday September 18). Canadian pipeline imports are treated as a supply source supplementing domestic production; Canadian pipeline exports are treated as demand. The Balancing Factor (+0.04 Bcf/d this week) represents the residual between independently modeled supply and demand components and calibrates the injection estimate against EIA actuals.

Data sources: SynMax daily production model (hdl.daily_production), SynMax demand model (hdl.gas_demand, baseline scenarios), SynMax LNG feedgas model (hdl.lng_feed_gas), EIA Weekly Natural Gas Storage Report, NOAA GFS/HRRR weather data.

Disclaimer: This report is produced by SynMax Analytics for informational purposes only. Modeled figures are estimates and may differ from official EIA releases. Past model accuracy does not guarantee future performance.