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Data as of 2026-09-20
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Built 2026-09-21 (21 September 2026)

SWPW Demand Forecast Accuracy: Error, Bias and Worst Miss, 21 August to 20 September 2026

The day-ahead demand forecast for SWPW was off by 14.5% on average (mean absolute percentage error) over 719 hours from 21 August to 20 September 2026, and 33% of hours landed within 5% of the reading. Its bias was +14.1%: it ran high on average, an over forecast. The largest miss was 1,418 MW (45.8%) too high at 14 Sept 2026, 18:00 CDT (UTC-05:00). Dates and times are local (America/Chicago).

Key Facts

  • The day-ahead demand forecast for SWPW was off by 14.5% on average (mean absolute percentage error) over 719 hours from 21 August to 20 September 2026, and 33% of hours landed within 5% of the reading. Its bias was +14.1%: it ran high on average, an over forecast. The largest miss was 1,418 MW (45.8%) too high at 14 Sept 2026, 18:00 CDT (UTC-05:00).
  • Across 53 US grids ranked by average error over their own latest 30 day windows, SWPW came 49 (1 is the smallest error).
  • On average the forecast differed from reported demand by 457 MW, against average demand of 3,179 MW.
  • The forecast was above reported demand in 86% of compared hours.

Forecast Error at a Glance

719 hours from 21 August to 20 September 2026
Average error14.5%
Bias+14.1%
Hours within 5%33%
Worst miss1,418 MW

Average error is the mean absolute percentage gap between the forecast and reported demand. Bias is the signed mean (+445 MW per hour on average): the forecast ran high on average, an over forecast. The worst miss was 1,418 MW (45.8%) too high at 14 Sept 2026, 18:00 CDT (UTC-05:00): forecast 4,517 MW, reported 3,099 MW.

Source: U.S. Energy Information Administration (EIA). (US Government work, public domain) Data as of 2026-09-20. Accuracy is computed by World Power Monitor from the operator's hourly forecast and reported demand.

Forecast and Reported Demand, Last 7 Days

Local time, to 20 Sept 2026, 20:00 CDT (UTC-05:00)
SWPW day-ahead demand forecast and reported demand by hour Hourly reported demand and the day-ahead forecast for SWPW over the last 7 days of the window, to 20 Sept 2026, 20:00 CDT (UTC-05:00). Gaps are hours with a missing, zero or implausible report. 0 1,250 2,500 3,750 5,000 13 Sept, 21:0014 Sept, 21:0015 Sept, 21:0016 Sept, 21:0017 Sept, 21:0018 Sept, 21:0019 Sept, 21:00
Hourly reported demand and the day-ahead forecast for SWPW over the last 7 days of the window, to 20 Sept 2026, 20:00 CDT (UTC-05:00). Gaps are hours with a missing, zero or implausible report.
Data to 2026-09-20
SWPW day-ahead demand forecast and reported demand by hour
Local hourReported demandDay-ahead forecast
13 Sept, 21:003,697 MW4,211 MW
13 Sept, 22:003,491 MW4,032 MW
13 Sept, 23:003,266 MW3,795 MW
14 Sept, 00:003,039 MW3,495 MW
14 Sept, 01:002,883 MW3,352 MW
14 Sept, 02:002,754 MW3,265 MW
14 Sept, 03:002,689 MW3,194 MW
14 Sept, 04:002,652 MW3,172 MW
14 Sept, 05:002,667 MW3,187 MW
14 Sept, 06:002,769 MW3,272 MW
14 Sept, 07:002,921 MW3,536 MW
14 Sept, 08:002,962 MW3,500 MW
14 Sept, 09:003,026 MW3,460 MW
14 Sept, 10:003,097 MW3,509 MW
14 Sept, 11:003,099 MW3,618 MW
14 Sept, 12:003,099 MW3,766 MW
14 Sept, 13:003,099 MW3,890 MW
14 Sept, 14:003,099 MW4,100 MW
14 Sept, 15:003,099 MW4,238 MW
14 Sept, 16:003,099 MW4,362 MW
14 Sept, 17:003,099 MW4,464 MW
14 Sept, 18:003,099 MW4,517 MW
14 Sept, 19:003,099 MW4,484 MW
14 Sept, 20:003,099 MW4,479 MW
14 Sept, 21:003,099 MW4,359 MW
14 Sept, 22:003,099 MW4,215 MW
14 Sept, 23:003,099 MW3,957 MW
15 Sept, 00:002,606 MW3,017 MW
15 Sept, 01:002,571 MW2,848 MW
15 Sept, 02:002,537 MW2,735 MW
15 Sept, 03:002,503 MW2,668 MW
15 Sept, 04:002,471 MW2,626 MW
15 Sept, 05:002,469 MW2,628 MW
15 Sept, 06:002,533 MW2,708 MW
15 Sept, 07:002,658 MW2,843 MW
15 Sept, 08:002,705 MW2,913 MW
15 Sept, 09:002,700 MW2,940 MW
15 Sept, 10:002,709 MW3,004 MW
15 Sept, 11:002,700 MW3,109 MW
15 Sept, 12:002,727 MW3,250 MW
15 Sept, 13:002,790 MW3,350 MW
15 Sept, 14:002,852 MW3,512 MW
15 Sept, 15:002,919 MW3,598 MW
15 Sept, 16:002,998 MW3,657 MW
15 Sept, 17:003,092 MW3,759 MW
15 Sept, 18:003,143 MW3,798 MW
15 Sept, 19:003,148 MW3,770 MW
15 Sept, 20:003,124 MW3,690 MW
15 Sept, 21:003,044 MW3,580 MW
15 Sept, 22:002,933 MW3,429 MW
15 Sept, 23:002,767 MW3,204 MW
16 Sept, 00:002,615 MW2,889 MW
16 Sept, 01:002,507 MW2,757 MW
16 Sept, 02:002,451 MW2,660 MW
16 Sept, 03:002,404 MW2,600 MW
16 Sept, 04:002,385 MW2,558 MW
16 Sept, 05:002,400 MW2,572 MW
16 Sept, 06:002,479 MW2,662 MW
16 Sept, 07:002,618 MW2,753 MW
16 Sept, 08:002,648 MW2,787 MW
16 Sept, 09:002,641 MW2,789 MW
16 Sept, 10:002,675 MW2,815 MW
16 Sept, 11:002,717 MW2,894 MW
16 Sept, 12:002,817 MW3,021 MW
16 Sept, 13:002,904 MW3,110 MW
16 Sept, 14:003,043 MW3,212 MW
16 Sept, 15:003,158 MW3,282 MW
16 Sept, 16:003,259 MW3,366 MW
16 Sept, 17:003,291 MW3,430 MW
16 Sept, 18:003,302 MW3,481 MW
16 Sept, 19:003,263 MW3,512 MW
16 Sept, 20:003,241 MW3,470 MW
16 Sept, 21:003,169 MW3,378 MW
16 Sept, 22:003,060 MW3,259 MW
16 Sept, 23:002,894 MW3,040 MW
17 Sept, 00:002,719 MW2,863 MW
17 Sept, 01:002,589 MW2,726 MW
17 Sept, 02:002,507 MW2,625 MW
17 Sept, 03:002,454 MW2,555 MW
17 Sept, 04:002,436 MW2,518 MW
17 Sept, 05:002,455 MW2,529 MW
17 Sept, 06:002,547 MW2,608 MW
17 Sept, 07:002,708 MW2,690 MW
17 Sept, 08:002,799 MW2,740 MW
17 Sept, 09:002,841 MW2,759 MW
17 Sept, 10:002,847 MW2,777 MW
17 Sept, 11:002,883 MW2,831 MW
17 Sept, 12:002,983 MW2,936 MW
17 Sept, 13:003,021 MW3,016 MW
17 Sept, 14:003,075 MW3,094 MW
17 Sept, 15:003,165 MW3,167 MW
17 Sept, 16:003,255 MW3,237 MW
17 Sept, 17:003,317 MW3,303 MW
17 Sept, 18:003,316 MW3,367 MW
17 Sept, 19:003,271 MW3,405 MW
17 Sept, 20:003,255 MW3,377 MW
17 Sept, 21:003,195 MW3,297 MW
17 Sept, 22:003,084 MW3,178 MW
17 Sept, 23:002,916 MW2,981 MW
18 Sept, 00:002,739 MW2,725 MW
18 Sept, 01:002,624 MW2,593 MW
18 Sept, 02:002,525 MW2,508 MW
18 Sept, 03:002,466 MW2,453 MW
18 Sept, 04:002,444 MW2,418 MW
18 Sept, 05:002,455 MW2,445 MW
18 Sept, 06:002,532 MW2,531 MW
18 Sept, 07:002,664 MW2,652 MW
18 Sept, 08:002,743 MW2,710 MW
18 Sept, 09:002,793 MW2,739 MW
18 Sept, 10:002,845 MW2,801 MW
18 Sept, 11:002,903 MW2,867 MW
18 Sept, 12:003,003 MW2,985 MW
18 Sept, 13:003,125 MW3,082 MW
18 Sept, 14:003,278 MW3,132 MW
18 Sept, 15:003,352 MW3,226 MW
18 Sept, 16:003,384 MW3,236 MW
18 Sept, 17:003,417 MW3,266 MW
18 Sept, 18:003,373 MW3,295 MW
18 Sept, 19:003,243 MW3,223 MW
18 Sept, 20:003,172 MW3,202 MW
18 Sept, 21:003,074 MW3,143 MW
18 Sept, 22:002,977 MW3,056 MW
18 Sept, 23:002,839 MW2,899 MW
19 Sept, 00:002,677 MW3,332 MW
19 Sept, 01:002,555 MW3,218 MW
19 Sept, 02:002,472 MW3,132 MW
19 Sept, 03:002,422 MW3,074 MW
19 Sept, 04:002,378 MW3,018 MW
19 Sept, 05:002,363 MW3,027 MW
19 Sept, 06:002,388 MW3,076 MW
19 Sept, 07:002,454 MW3,164 MW
19 Sept, 08:002,487 MW3,157 MW
19 Sept, 09:002,530 MW3,303 MW
19 Sept, 10:002,590 MW3,351 MW
19 Sept, 11:002,650 MW3,373 MW
19 Sept, 12:002,728 MW3,476 MW
19 Sept, 13:002,858 MW3,567 MW
19 Sept, 14:002,930 MW3,661 MW
19 Sept, 15:002,981 MW3,736 MW
19 Sept, 16:003,069 MW3,766 MW
19 Sept, 17:003,079 MW3,922 MW
19 Sept, 18:003,104 MW3,942 MW
19 Sept, 19:003,057 MW3,876 MW
19 Sept, 20:002,999 MW3,850 MW
19 Sept, 21:002,928 MW3,783 MW
19 Sept, 22:002,831 MW3,689 MW
19 Sept, 23:002,695 MW3,555 MW
20 Sept, 00:002,551 MW3,301 MW
20 Sept, 01:002,453 MW3,199 MW
20 Sept, 02:002,379 MW3,076 MW
20 Sept, 03:002,320 MW3,048 MW
20 Sept, 04:002,287 MW3,028 MW
20 Sept, 05:002,278 MW3,035 MW
20 Sept, 06:002,302 MW3,067 MW
20 Sept, 07:002,349 MW3,089 MW
20 Sept, 08:002,374 MW3,187 MW
20 Sept, 09:002,410 MW3,223 MW
20 Sept, 10:002,451 MW3,351 MW
20 Sept, 11:002,488 MW3,473 MW
20 Sept, 12:002,548 MW3,630 MW
20 Sept, 13:002,620 MW3,714 MW
20 Sept, 14:002,702 MW3,829 MW
20 Sept, 15:002,799 MW3,899 MW
20 Sept, 16:002,890 MW3,942 MW
20 Sept, 17:002,985 MW3,972 MW
20 Sept, 18:003,078 MW3,994 MW
20 Sept, 19:003,081 MW3,910 MW
20 Sept, 20:003,063 MW3,849 MW

Assumptions

  • Only hours with both a forecast and a positive demand reading count (719 of 720 hours in the window). Missing and zero values, and readings under 30% or over 3 times the grid's own median for the window, are treated as reporting faults and left out.
  • Error is (forecast minus reported demand) divided by reported demand; average error uses absolute values so high and low misses do not cancel. Bias keeps the sign and does cancel.
  • Reported demand is preliminary and may be revised. A 30 day window is a short sample and one heat wave or holiday can move these figures.
  • US figures are for the EIA balancing authority or region named on this page. US and European grids are ranked separately.