BHBA Demand Forecast Accuracy: Error, Bias and Worst Miss, 21 August to 20 September 2026
The day-ahead demand forecast for BHBA was off by 7.1% on average (mean absolute percentage error) over 719 hours from 21 August to 20 September 2026, and 29% of hours landed within 5% of the reading. Its bias was -6.9%: it ran low on average, an under forecast. The largest miss was 171 MW (15.7%) too low at 2 Sept 2026, 17:00 MDT (UTC-06:00). Dates and times are local (America/Denver).
Key Facts
- The day-ahead demand forecast for BHBA was off by 7.1% on average (mean absolute percentage error) over 719 hours from 21 August to 20 September 2026, and 29% of hours landed within 5% of the reading. Its bias was -6.9%: it ran low on average, an under forecast. The largest miss was 171 MW (15.7%) too low at 2 Sept 2026, 17:00 MDT (UTC-06:00).
- Across 53 US grids ranked by average error over their own latest 30 day windows, BHBA came 36 (1 is the smallest error).
- On average the forecast differed from reported demand by 65 MW, against average demand of 907 MW.
- The forecast was above reported demand in 5% of compared hours.
Forecast Error at a Glance
719 hours from 21 August to 20 September 2026Average error7.1%
Bias-6.9%
Hours within 5%29%
Worst miss171 MW
Average error is the mean absolute percentage gap between the forecast and reported demand. Bias is the signed mean (-63 MW per hour on average): the forecast ran low on average, an under forecast. The worst miss was 171 MW (15.7%) too low at 2 Sept 2026, 17:00 MDT (UTC-06:00): forecast 916 MW, reported 1,087 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, 19:00 MDT (UTC-06:00)Data to 2026-09-20
| Local hour | Reported demand | Day-ahead forecast |
|---|---|---|
| 13 Sept, 20:00 | 941 MW | 812 MW |
| 13 Sept, 21:00 | 909 MW | 795 MW |
| 13 Sept, 22:00 | 872 MW | 772 MW |
| 13 Sept, 23:00 | 842 MW | 743 MW |
| 14 Sept, 00:00 | 811 MW | 725 MW |
| 14 Sept, 01:00 | 791 MW | 713 MW |
| 14 Sept, 02:00 | 785 MW | 710 MW |
| 14 Sept, 03:00 | 798 MW | 709 MW |
| 14 Sept, 04:00 | 805 MW | 708 MW |
| 14 Sept, 05:00 | 825 MW | 718 MW |
| 14 Sept, 06:00 | 851 MW | 720 MW |
| 14 Sept, 07:00 | 885 MW | 744 MW |
| 14 Sept, 08:00 | 919 MW | 775 MW |
| 14 Sept, 09:00 | 929 MW | 783 MW |
| 14 Sept, 10:00 | 947 MW | 792 MW |
| 14 Sept, 11:00 | 952 MW | 805 MW |
| 14 Sept, 12:00 | 947 MW | 817 MW |
| 14 Sept, 13:00 | 943 MW | 826 MW |
| 14 Sept, 14:00 | 951 MW | 844 MW |
| 14 Sept, 15:00 | 971 MW | 859 MW |
| 14 Sept, 16:00 | 983 MW | 869 MW |
| 14 Sept, 17:00 | 977 MW | 869 MW |
| 14 Sept, 18:00 | 950 MW | 844 MW |
| 14 Sept, 19:00 | 944 MW | 844 MW |
| 14 Sept, 20:00 | 924 MW | 837 MW |
| 14 Sept, 21:00 | 900 MW | 813 MW |
| 14 Sept, 22:00 | 866 MW | 783 MW |
| 14 Sept, 23:00 | 839 MW | 750 MW |
| 15 Sept, 00:00 | 820 MW | 749 MW |
| 15 Sept, 01:00 | 804 MW | 736 MW |
| 15 Sept, 02:00 | 792 MW | 727 MW |
| 15 Sept, 03:00 | 792 MW | 726 MW |
| 15 Sept, 04:00 | 800 MW | 732 MW |
| 15 Sept, 05:00 | 826 MW | 759 MW |
| 15 Sept, 06:00 | 847 MW | 786 MW |
| 15 Sept, 07:00 | 870 MW | 818 MW |
| 15 Sept, 08:00 | 885 MW | 853 MW |
| 15 Sept, 09:00 | 886 MW | 862 MW |
| 15 Sept, 10:00 | 886 MW | 868 MW |
| 15 Sept, 11:00 | 896 MW | 867 MW |
| 15 Sept, 12:00 | 903 MW | 871 MW |
| 15 Sept, 13:00 | 913 MW | 879 MW |
| 15 Sept, 14:00 | 923 MW | 892 MW |
| 15 Sept, 15:00 | 924 MW | 905 MW |
| 15 Sept, 16:00 | 928 MW | 910 MW |
| 15 Sept, 17:00 | 919 MW | 896 MW |
| 15 Sept, 18:00 | 892 MW | 864 MW |
| 15 Sept, 19:00 | 896 MW | 854 MW |
| 15 Sept, 20:00 | 891 MW | 846 MW |
| 15 Sept, 21:00 | 862 MW | 820 MW |
| 15 Sept, 22:00 | 834 MW | 787 MW |
| 15 Sept, 23:00 | 810 MW | 757 MW |
| 16 Sept, 00:00 | 792 MW | 742 MW |
| 16 Sept, 01:00 | 734 MW | 729 MW |
| 16 Sept, 02:00 | 729 MW | 721 MW |
| 16 Sept, 03:00 | 775 MW | 722 MW |
| 16 Sept, 04:00 | 790 MW | 728 MW |
| 16 Sept, 05:00 | 814 MW | 753 MW |
| 16 Sept, 06:00 | 841 MW | 777 MW |
| 16 Sept, 07:00 | 859 MW | 802 MW |
| 16 Sept, 08:00 | 898 MW | 826 MW |
| 16 Sept, 09:00 | 905 MW | 826 MW |
| 16 Sept, 10:00 | 908 MW | 832 MW |
| 16 Sept, 11:00 | 922 MW | 836 MW |
| 16 Sept, 12:00 | 931 MW | 843 MW |
| 16 Sept, 13:00 | 936 MW | 851 MW |
| 16 Sept, 14:00 | 946 MW | 859 MW |
| 16 Sept, 15:00 | 943 MW | 869 MW |
| 16 Sept, 16:00 | 962 MW | 876 MW |
| 16 Sept, 17:00 | 965 MW | 864 MW |
| 16 Sept, 18:00 | 943 MW | 838 MW |
| 16 Sept, 19:00 | 930 MW | 842 MW |
| 16 Sept, 20:00 | 924 MW | 840 MW |
| 16 Sept, 21:00 | 883 MW | 817 MW |
| 16 Sept, 22:00 | 849 MW | 786 MW |
| 16 Sept, 23:00 | 821 MW | 757 MW |
| 17 Sept, 00:00 | 803 MW | 734 MW |
| 17 Sept, 01:00 | 798 MW | 725 MW |
| 17 Sept, 02:00 | 788 MW | 716 MW |
| 17 Sept, 03:00 | 790 MW | 719 MW |
| 17 Sept, 04:00 | 796 MW | 727 MW |
| 17 Sept, 05:00 | 822 MW | 753 MW |
| 17 Sept, 06:00 | 846 MW | 777 MW |
| 17 Sept, 07:00 | 874 MW | 798 MW |
| 17 Sept, 08:00 | 901 MW | 828 MW |
| 17 Sept, 09:00 | 911 MW | 834 MW |
| 17 Sept, 10:00 | 914 MW | 843 MW |
| 17 Sept, 11:00 | 924 MW | 854 MW |
| 17 Sept, 12:00 | 931 MW | 872 MW |
| 17 Sept, 13:00 | 924 MW | 891 MW |
| 17 Sept, 14:00 | 926 MW | 909 MW |
| 17 Sept, 15:00 | 923 MW | 924 MW |
| 17 Sept, 16:00 | 922 MW | 932 MW |
| 17 Sept, 17:00 | 906 MW | 917 MW |
| 17 Sept, 18:00 | 890 MW | 881 MW |
| 17 Sept, 19:00 | 892 MW | 873 MW |
| 17 Sept, 20:00 | 883 MW | 859 MW |
| 17 Sept, 21:00 | 869 MW | 832 MW |
| 17 Sept, 22:00 | 844 MW | 798 MW |
| 17 Sept, 23:00 | 825 MW | 761 MW |
| 18 Sept, 00:00 | 812 MW | 731 MW |
| 18 Sept, 01:00 | 799 MW | 719 MW |
| 18 Sept, 02:00 | 788 MW | 713 MW |
| 18 Sept, 03:00 | 788 MW | 713 MW |
| 18 Sept, 04:00 | 789 MW | 723 MW |
| 18 Sept, 05:00 | 801 MW | 748 MW |
| 18 Sept, 06:00 | 834 MW | 772 MW |
| 18 Sept, 07:00 | 868 MW | 799 MW |
| 18 Sept, 08:00 | 891 MW | 828 MW |
| 18 Sept, 09:00 | 909 MW | 840 MW |
| 18 Sept, 10:00 | 914 MW | 848 MW |
| 18 Sept, 11:00 | 929 MW | 854 MW |
| 18 Sept, 12:00 | 943 MW | 859 MW |
| 18 Sept, 13:00 | 956 MW | 860 MW |
| 18 Sept, 14:00 | 975 MW | 860 MW |
| 18 Sept, 15:00 | 997 MW | 860 MW |
| 18 Sept, 16:00 | 995 MW | 857 MW |
| 18 Sept, 17:00 | 967 MW | 848 MW |
| 18 Sept, 18:00 | 904 MW | 824 MW |
| 18 Sept, 19:00 | 872 MW | 827 MW |
| 18 Sept, 20:00 | 857 MW | 825 MW |
| 18 Sept, 21:00 | 833 MW | 806 MW |
| 18 Sept, 22:00 | 818 MW | 776 MW |
| 18 Sept, 23:00 | 794 MW | 750 MW |
| 19 Sept, 00:00 | 777 MW | 739 MW |
| 19 Sept, 01:00 | 779 MW | 730 MW |
| 19 Sept, 02:00 | 769 MW | 720 MW |
| 19 Sept, 03:00 | 759 MW | 720 MW |
| 19 Sept, 04:00 | 758 MW | 727 MW |
| 19 Sept, 05:00 | 770 MW | 751 MW |
| 19 Sept, 06:00 | 776 MW | 767 MW |
| 19 Sept, 07:00 | 799 MW | 794 MW |
| 19 Sept, 08:00 | 838 MW | 828 MW |
| 19 Sept, 09:00 | 852 MW | 844 MW |
| 19 Sept, 10:00 | 851 MW | 853 MW |
| 19 Sept, 11:00 | 865 MW | 863 MW |
| 19 Sept, 12:00 | 869 MW | 876 MW |
| 19 Sept, 13:00 | 870 MW | 881 MW |
| 19 Sept, 14:00 | 869 MW | 885 MW |
| 19 Sept, 15:00 | 876 MW | 884 MW |
| 19 Sept, 16:00 | 878 MW | 883 MW |
| 19 Sept, 17:00 | 882 MW | 865 MW |
| 19 Sept, 18:00 | 857 MW | 831 MW |
| 19 Sept, 19:00 | 843 MW | 831 MW |
| 19 Sept, 20:00 | 849 MW | 828 MW |
| 19 Sept, 21:00 | 825 MW | 810 MW |
| 19 Sept, 22:00 | 808 MW | 784 MW |
| 19 Sept, 23:00 | 789 MW | 756 MW |
| 20 Sept, 00:00 | 767 MW | 740 MW |
| 20 Sept, 01:00 | 749 MW | 727 MW |
| 20 Sept, 02:00 | 744 MW | 718 MW |
| 20 Sept, 03:00 | 742 MW | 715 MW |
| 20 Sept, 04:00 | 749 MW | 715 MW |
| 20 Sept, 05:00 | 755 MW | 727 MW |
| 20 Sept, 06:00 | 764 MW | 727 MW |
| 20 Sept, 07:00 | 782 MW | 751 MW |
| 20 Sept, 08:00 | 818 MW | 784 MW |
| 20 Sept, 09:00 | 842 MW | 796 MW |
| 20 Sept, 10:00 | 845 MW | 802 MW |
| 20 Sept, 11:00 | 852 MW | 805 MW |
| 20 Sept, 12:00 | 853 MW | 807 MW |
| 20 Sept, 13:00 | 845 MW | 806 MW |
| 20 Sept, 14:00 | 836 MW | 809 MW |
| 20 Sept, 15:00 | 831 MW | 810 MW |
| 20 Sept, 16:00 | 848 MW | 814 MW |
| 20 Sept, 17:00 | 864 MW | 808 MW |
| 20 Sept, 18:00 | 852 MW | 786 MW |
| 20 Sept, 19:00 | 856 MW | 790 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.