| Date | GFS | IFS | GEFS | AIFS |
|---|---|---|---|---|
| Oct 17 | 8.5 / 3.0 | 7.5 / 3.1 | 8.1 / 3.1 | 7.6 / 3.5 |
| Oct 18 | 13.6 / 0.8 | 12.0 / 0.8 | 13.7 / 0.8 | 11.6 / 1.0 |
| Oct 19 | 11.5 / 0.7 | 10.3 / 0.8 | 11.8 / 0.6 | 8.7 / 1.0 |
| Oct 20 | 9.5 / 0.9 | 8.8 / 0.9 | 9.6 / 0.7 | 7.0 / 1.3 |
| Oct 21 | 7.5 / 1.2 | 6.5 / 1.1 | 7.8 / 1.0 | 4.6 / 1.7 |
| Oct 22 | 7.6 / 1.7 | 6.4 / 1.5 | 7.7 / 1.3 | 4.4 / 2.4 |
| Oct 23 | 7.4 / 2.1 | 6.3 / 1.8 | 7.8 / 1.5 | 4.0 / 2.9 |
| Oct 24 | 7.0 / 2.3 | 6.9 / 1.8 | 7.7 / 1.7 | 4.5 / 3.1 |
| Oct 25 | 7.5 / 2.3 | 8.0 / 1.7 | 7.6 / 1.8 | 5.7 / 3.0 |
| Oct 26 | 8.3 / 1.9 | 8.4 / 1.6 | 7.8 / 1.5 | 6.2 / 2.5 |
| Division | Weight | Power Burn | States |
|---|---|---|---|
| South Atlantic | 24.0% | 24.0% | DE, DC, FL, GA, MD, NC, SC, VA, WV |
| West South Central | 17.7% | 17.7% | AR, LA, OK, TX |
| Middle Atlantic | 13.5% | 13.5% | NJ, NY, PA |
| East North Central | 11.1% | 11.1% | IL, IN, MI, OH, WI |
| East South Central | 8.9% | 8.9% | AL, KY, MS, TN |
| West North Central | 7.7% | 7.7% | IA, KS, MN, MO, NE, ND, SD |
| Pacific (CONUS) | 7.3% | 7.4% | CA, OR, WA |
| Mountain | 6.3% | 6.3% | AZ, CO, ID, MT, NV, NM, UT, WY |
| New England | 3.5% | 3.5% | CT, ME, MA, NH, RI, VT |
Power-weighted degree days (PWCDD) aggregate temperature data by where natural gas is actually burned to make electricity. They directly proxy power-burn demand — the dominant marginal driver of summer gas demand. While GWDD weights heating-heavy regions (Midwest, Mid-Atlantic) and POPDD weights where people live, PWCDD weights where gas-fired generation runs.
The result: South Atlantic (24.0%) and West South Central (17.7%) dominate the index — FPL, SOCO, Duke, and ERCOT carry the summer power burn. East North Central drops from 20% (GWDD) to 11%, reflecting the Midwest's smaller gas-fired generation share. This re-weighting is the entire point: PWCDD captures cooling-driven Bcf/d more accurately than either GWDD (heating bias) or POPDD (population bias).
All four models — GFS, IFS, GEFS, AIFS — run on the same cycle so HDD and CDD splits are apples-to-apples across models. Weights derived from 3 years of summer natural gas generation across 47 balancing authorities, mapped to the 9 EIA census divisions. CONUS only.