WALC Demand Forecast Accuracy: Error, Bias and Worst Miss, 28 September to 28 October 2026

The day-ahead demand forecast for WALC was off by 16.4% on average (mean absolute percentage error) over 719 hours from 28 September to 28 October 2026, and 18% of hours landed within 5% of the reading. Its bias was +8.5%: it ran high on average, an over forecast. The largest miss was 494 MW (70.0%) too high at 27 Oct 2026, 18:00 MST (UTC-07:00). Dates and times are local (America/Phoenix).

Key Facts

The day-ahead demand forecast for WALC was off by 16.4% on average (mean absolute percentage error) over 719 hours from 28 September to 28 October 2026, and 18% of hours landed within 5% of the reading. Its bias was +8.5%: it ran high on average, an over forecast. The largest miss was 494 MW (70.0%) too high at 27 Oct 2026, 18:00 MST (UTC-07:00).
Across 53 US grids ranked by average error over their own latest 30 day windows, WALC came 47 (1 is the smallest error).
On average the forecast differed from reported demand by 140 MW, against average demand of 892 MW.
The forecast was above reported demand in 63% of compared hours.

Forecast Error at a Glance

719 hours from 28 September to 28 October 2026

Average error16.4%

Bias+8.5%

Hours within 5%18%

Worst miss494 MW

Average error is the mean absolute percentage gap between the forecast and reported demand. Bias is the signed mean (+62 MW per hour on average): the forecast ran high on average, an over forecast. The worst miss was 494 MW (70.0%) too high at 27 Oct 2026, 18:00 MST (UTC-07:00): forecast 1,200 MW, reported 706 MW.

Source: U.S. Energy Information Administration (EIA). (US Government work, public domain) Data as of 2026-10-28. 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 28 Oct 2026, 04:00 MST (UTC-07:00)

Hourly reported demand and the day-ahead forecast for WALC over the last 7 days of the window, to 28 Oct 2026, 04:00 MST (UTC-07:00). Gaps are hours with a missing, zero or implausible report.

Data to 2026-10-28

Show the data table (168 rows)

Local hour	Reported demand	Day-ahead forecast
21 Oct, 05:00	823 MW	640 MW
21 Oct, 06:00	848 MW	858 MW
21 Oct, 07:00	811 MW	738 MW
21 Oct, 08:00	844 MW	903 MW
21 Oct, 09:00	820 MW	887 MW
21 Oct, 10:00	913 MW	849 MW
21 Oct, 11:00	978 MW	909 MW
21 Oct, 12:00	1,099 MW	1,027 MW
21 Oct, 13:00	1,126 MW	951 MW
21 Oct, 14:00	1,176 MW	1,027 MW
21 Oct, 15:00	1,144 MW	995 MW
21 Oct, 16:00	1,009 MW	832 MW
21 Oct, 17:00	1,232 MW	1,080 MW
21 Oct, 18:00	1,206 MW	1,223 MW
21 Oct, 19:00	1,059 MW	1,264 MW
21 Oct, 20:00	1,073 MW	1,137 MW
21 Oct, 21:00	1,175 MW	1,087 MW
21 Oct, 22:00	1,009 MW	901 MW
21 Oct, 23:00	833 MW	759 MW
22 Oct, 00:00	816 MW	754 MW
22 Oct, 01:00	783 MW	699 MW
22 Oct, 02:00	769 MW	690 MW
22 Oct, 03:00	775 MW	682 MW
22 Oct, 04:00	766 MW	708 MW
22 Oct, 05:00	774 MW	961 MW
22 Oct, 06:00	833 MW	901 MW
22 Oct, 07:00	808 MW	806 MW
22 Oct, 08:00	1,019 MW	786 MW
22 Oct, 09:00	1,059 MW	838 MW
22 Oct, 10:00	1,019 MW	815 MW
22 Oct, 11:00	1,015 MW	880 MW
22 Oct, 12:00	1,065 MW	938 MW
22 Oct, 13:00	1,064 MW	896 MW
22 Oct, 14:00	1,054 MW	837 MW
22 Oct, 15:00	1,069 MW	793 MW
22 Oct, 16:00	988 MW	798 MW
22 Oct, 17:00	1,141 MW	1,042 MW
22 Oct, 18:00	1,125 MW	1,118 MW
22 Oct, 19:00	1,160 MW	1,147 MW
22 Oct, 20:00	925 MW	1,012 MW
22 Oct, 21:00	853 MW	969 MW
22 Oct, 22:00	904 MW	902 MW
22 Oct, 23:00	696 MW	865 MW
23 Oct, 00:00	706 MW	769 MW
23 Oct, 01:00	771 MW	759 MW
23 Oct, 02:00	715 MW	776 MW
23 Oct, 03:00	687 MW	739 MW
23 Oct, 04:00	682 MW	738 MW
23 Oct, 05:00	745 MW	791 MW
23 Oct, 06:00	678 MW	736 MW
23 Oct, 07:00	666 MW	661 MW
23 Oct, 08:00	723 MW	780 MW
23 Oct, 09:00	754 MW	810 MW
23 Oct, 10:00	756 MW	844 MW
23 Oct, 11:00	803 MW	873 MW
23 Oct, 12:00	848 MW	860 MW
23 Oct, 13:00	868 MW	827 MW
23 Oct, 14:00	866 MW	799 MW
23 Oct, 15:00	817 MW	803 MW
23 Oct, 16:00	789 MW	804 MW
23 Oct, 17:00	1,013 MW	1,145 MW
23 Oct, 18:00	1,072 MW	1,124 MW
23 Oct, 19:00	1,046 MW	1,147 MW
23 Oct, 20:00	1,070 MW	1,097 MW
23 Oct, 21:00	849 MW	1,050 MW
23 Oct, 22:00	823 MW	1,015 MW
23 Oct, 23:00	711 MW	975 MW
24 Oct, 00:00	891 MW	728 MW
24 Oct, 01:00	832 MW	731 MW
24 Oct, 02:00	704 MW	740 MW
24 Oct, 03:00	700 MW	710 MW
24 Oct, 04:00	713 MW	782 MW
24 Oct, 05:00	725 MW	796 MW
24 Oct, 06:00	726 MW	712 MW
24 Oct, 07:00	724 MW	572 MW
24 Oct, 08:00	933 MW	582 MW
24 Oct, 09:00	873 MW	582 MW
24 Oct, 10:00	894 MW	628 MW
24 Oct, 11:00	864 MW	610 MW
24 Oct, 12:00	891 MW	596 MW
24 Oct, 13:00	908 MW	624 MW
24 Oct, 14:00	962 MW	655 MW
24 Oct, 15:00	975 MW	708 MW
24 Oct, 16:00	944 MW	663 MW
24 Oct, 17:00	1,073 MW	956 MW
24 Oct, 18:00	1,073 MW	987 MW
24 Oct, 19:00	1,078 MW	919 MW
24 Oct, 20:00	959 MW	784 MW
24 Oct, 21:00	938 MW	789 MW
24 Oct, 22:00	940 MW	863 MW
24 Oct, 23:00	767 MW	832 MW
25 Oct, 00:00	646 MW	769 MW
25 Oct, 01:00	625 MW	741 MW
25 Oct, 02:00	631 MW	732 MW
25 Oct, 03:00	683 MW	746 MW
25 Oct, 04:00	672 MW	821 MW
25 Oct, 05:00	660 MW	825 MW
25 Oct, 06:00	668 MW	777 MW
25 Oct, 07:00	671 MW	666 MW
25 Oct, 08:00	881 MW	849 MW
25 Oct, 09:00	805 MW	835 MW
25 Oct, 10:00	812 MW	846 MW
25 Oct, 11:00	830 MW	896 MW
25 Oct, 12:00	875 MW	918 MW
25 Oct, 13:00	886 MW	943 MW
25 Oct, 14:00	878 MW	999 MW
25 Oct, 15:00	891 MW	990 MW
25 Oct, 16:00	778 MW	940 MW
25 Oct, 17:00	964 MW	1,067 MW
25 Oct, 18:00	928 MW	1,146 MW
25 Oct, 19:00	970 MW	1,109 MW
25 Oct, 20:00	850 MW	897 MW
25 Oct, 21:00	804 MW	860 MW
25 Oct, 22:00	717 MW	895 MW
25 Oct, 23:00	590 MW	862 MW
26 Oct, 00:00	535 MW	779 MW
26 Oct, 01:00	520 MW	737 MW
26 Oct, 02:00	497 MW	749 MW
26 Oct, 03:00	507 MW	782 MW
26 Oct, 04:00	556 MW	819 MW
26 Oct, 05:00	650 MW	843 MW
26 Oct, 06:00	768 MW	828 MW
26 Oct, 07:00	750 MW	808 MW
26 Oct, 08:00	811 MW	900 MW
26 Oct, 09:00	794 MW	902 MW
26 Oct, 10:00	793 MW	990 MW
26 Oct, 11:00	787 MW	1,042 MW
26 Oct, 12:00	801 MW	1,062 MW
26 Oct, 13:00	862 MW	1,108 MW
26 Oct, 14:00	931 MW	1,122 MW
26 Oct, 15:00	1,465 MW	1,127 MW
26 Oct, 16:00	818 MW	980 MW
26 Oct, 17:00	913 MW	1,067 MW
26 Oct, 18:00	966 MW	1,155 MW
26 Oct, 19:00	977 MW	1,070 MW
26 Oct, 20:00	827 MW	998 MW
26 Oct, 21:00	804 MW	961 MW
26 Oct, 22:00	748 MW	915 MW
26 Oct, 23:00	625 MW	775 MW
27 Oct, 00:00	524 MW	754 MW
27 Oct, 01:00	551 MW	745 MW
27 Oct, 02:00	497 MW	744 MW
27 Oct, 03:00	477 MW	784 MW
27 Oct, 04:00	499 MW	743 MW
27 Oct, 05:00	530 MW	753 MW
27 Oct, 06:00	707 MW	736 MW
27 Oct, 07:00	786 MW	710 MW
27 Oct, 08:00	694 MW	895 MW
27 Oct, 09:00	681 MW	836 MW
27 Oct, 10:00	687 MW	938 MW
27 Oct, 11:00	745 MW	1,047 MW
27 Oct, 12:00	724 MW	1,053 MW
27 Oct, 13:00	718 MW	1,064 MW
27 Oct, 14:00	758 MW	1,002 MW
27 Oct, 15:00	827 MW	1,005 MW
27 Oct, 16:00	701 MW	940 MW
27 Oct, 17:00	750 MW	1,112 MW
27 Oct, 18:00	706 MW	1,200 MW
27 Oct, 19:00	762 MW	1,153 MW
27 Oct, 20:00	821 MW	985 MW
27 Oct, 21:00	782 MW	965 MW
27 Oct, 22:00	612 MW	876 MW
27 Oct, 23:00	656 MW	783 MW
28 Oct, 00:00	571 MW	730 MW
28 Oct, 01:00	565 MW	736 MW
28 Oct, 02:00	560 MW	743 MW
28 Oct, 03:00	561 MW	777 MW
28 Oct, 04:00	554 MW	754 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.

Cite this page

APA 7

World Power Monitor. (2026). WALC Demand Forecast Accuracy: Error, Bias and Worst Miss. https://worldpowermonitor.com/forecast-accuracy/walc/

Plain text

World Power Monitor. WALC Demand Forecast Accuracy: Error, Bias and Worst Miss. Data as of 2026-10-28. Data from U.S. Energy Information Administration. https://worldpowermonitor.com/forecast-accuracy/walc/

BibTeX

@misc{wpm_forecast_accuracy_walc_2026,
  title = {{WALC Demand Forecast Accuracy: Error, Bias and Worst Miss}},
  author = {{World Power Monitor}},
  year = {2026},
  note = {Data as of 2026-10-28. Data from U.S. Energy Information Administration.},
  url = {https://worldpowermonitor.com/forecast-accuracy/walc/}
}

Permalink: https://worldpowermonitor.com/forecast-accuracy/walc/

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WALC Demand Forecast Accuracy: Error, Bias and Worst Miss, 28 September to 28 October 2026

Key Facts

Forecast Error at a Glance

Forecast and Reported Demand, Last 7 Days

Assumptions

Related