GCPD Demand Forecast Accuracy: Error, Bias and Worst Miss, 28 September to 28 October 2026
The day-ahead demand forecast for GCPD was off by 2.9% on average (mean absolute percentage error) over 719 hours from 28 September to 28 October 2026, and 89% of hours landed within 5% of the reading. Its bias was -2.7%: it ran low on average, an under forecast. The largest miss was 75 MW (10.3%) too low at 28 Sept 2026, 20:00 PDT (UTC-07:00). Dates and times are local (America/Los_Angeles).
Key Facts
- The day-ahead demand forecast for GCPD was off by 2.9% on average (mean absolute percentage error) over 719 hours from 28 September to 28 October 2026, and 89% of hours landed within 5% of the reading. Its bias was -2.7%: it ran low on average, an under forecast. The largest miss was 75 MW (10.3%) too low at 28 Sept 2026, 20:00 PDT (UTC-07:00).
- Across 53 US grids ranked by average error over their own latest 30 day windows, GCPD came 15 (1 is the smallest error).
- On average the forecast differed from reported demand by 20 MW, against average demand of 714 MW.
- The forecast was above reported demand in 6% of compared hours.
Forecast Error at a Glance
719 hours from 28 September to 28 October 2026Average error2.9%
Bias-2.7%
Hours within 5%89%
Worst miss75 MW
Average error is the mean absolute percentage gap between the forecast and reported demand. Bias is the signed mean (-20 MW per hour on average): the forecast ran low on average, an under forecast. The worst miss was 75 MW (10.3%) too low at 28 Sept 2026, 20:00 PDT (UTC-07:00): forecast 653 MW, reported 728 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 PDT (UTC-07:00)Data to 2026-10-28
Show the data table (168 rows)
| Local hour | Reported demand | Day-ahead forecast |
|---|---|---|
| 21 Oct, 05:00 | 740 MW | 720 MW |
| 21 Oct, 06:00 | 763 MW | 744 MW |
| 21 Oct, 07:00 | 773 MW | 757 MW |
| 21 Oct, 08:00 | 779 MW | 756 MW |
| 21 Oct, 09:00 | 767 MW | 752 MW |
| 21 Oct, 10:00 | 751 MW | 744 MW |
| 21 Oct, 11:00 | 754 MW | 738 MW |
| 21 Oct, 12:00 | 753 MW | 733 MW |
| 21 Oct, 13:00 | 780 MW | 728 MW |
| 21 Oct, 14:00 | 747 MW | 724 MW |
| 21 Oct, 15:00 | 749 MW | 724 MW |
| 21 Oct, 16:00 | 748 MW | 724 MW |
| 21 Oct, 17:00 | 748 MW | 722 MW |
| 21 Oct, 18:00 | 753 MW | 725 MW |
| 21 Oct, 19:00 | 751 MW | 724 MW |
| 21 Oct, 20:00 | 750 MW | 721 MW |
| 21 Oct, 21:00 | 742 MW | 710 MW |
| 21 Oct, 22:00 | 732 MW | 698 MW |
| 21 Oct, 23:00 | 727 MW | 691 MW |
| 22 Oct, 00:00 | 724 MW | 695 MW |
| 22 Oct, 01:00 | 722 MW | 694 MW |
| 22 Oct, 02:00 | 724 MW | 697 MW |
| 22 Oct, 03:00 | 728 MW | 698 MW |
| 22 Oct, 04:00 | 737 MW | 717 MW |
| 22 Oct, 05:00 | 760 MW | 736 MW |
| 22 Oct, 06:00 | 785 MW | 753 MW |
| 22 Oct, 07:00 | 791 MW | 760 MW |
| 22 Oct, 08:00 | 792 MW | 761 MW |
| 22 Oct, 09:00 | 781 MW | 758 MW |
| 22 Oct, 10:00 | 776 MW | 745 MW |
| 22 Oct, 11:00 | 770 MW | 741 MW |
| 22 Oct, 12:00 | 766 MW | 739 MW |
| 22 Oct, 13:00 | 764 MW | 743 MW |
| 22 Oct, 14:00 | 763 MW | 730 MW |
| 22 Oct, 15:00 | 762 MW | 728 MW |
| 22 Oct, 16:00 | 769 MW | 725 MW |
| 22 Oct, 17:00 | 774 MW | 729 MW |
| 22 Oct, 18:00 | 774 MW | 736 MW |
| 22 Oct, 19:00 | 767 MW | 731 MW |
| 22 Oct, 20:00 | 762 MW | 726 MW |
| 22 Oct, 21:00 | 748 MW | 713 MW |
| 22 Oct, 22:00 | 735 MW | 700 MW |
| 22 Oct, 23:00 | 728 MW | 691 MW |
| 23 Oct, 00:00 | 724 MW | 687 MW |
| 23 Oct, 01:00 | 721 MW | 684 MW |
| 23 Oct, 02:00 | 715 MW | 676 MW |
| 23 Oct, 03:00 | 717 MW | 681 MW |
| 23 Oct, 04:00 | 718 MW | 687 MW |
| 23 Oct, 05:00 | 744 MW | 707 MW |
| 23 Oct, 06:00 | 764 MW | 721 MW |
| 23 Oct, 07:00 | 768 MW | 733 MW |
| 23 Oct, 08:00 | 767 MW | 737 MW |
| 23 Oct, 09:00 | 752 MW | 739 MW |
| 23 Oct, 10:00 | 736 MW | 730 MW |
| 23 Oct, 11:00 | 728 MW | 725 MW |
| 23 Oct, 12:00 | 719 MW | 717 MW |
| 23 Oct, 13:00 | 710 MW | 713 MW |
| 23 Oct, 14:00 | 700 MW | 704 MW |
| 23 Oct, 15:00 | 694 MW | 702 MW |
| 23 Oct, 16:00 | 687 MW | 704 MW |
| 23 Oct, 17:00 | 685 MW | 703 MW |
| 23 Oct, 18:00 | 692 MW | 707 MW |
| 23 Oct, 19:00 | 690 MW | 711 MW |
| 23 Oct, 20:00 | 690 MW | 710 MW |
| 23 Oct, 21:00 | 689 MW | 702 MW |
| 23 Oct, 22:00 | 685 MW | 701 MW |
| 23 Oct, 23:00 | 681 MW | 703 MW |
| 24 Oct, 00:00 | 678 MW | 679 MW |
| 24 Oct, 01:00 | 680 MW | 681 MW |
| 24 Oct, 02:00 | 678 MW | 682 MW |
| 24 Oct, 03:00 | 682 MW | 695 MW |
| 24 Oct, 04:00 | 693 MW | 700 MW |
| 24 Oct, 05:00 | 708 MW | 723 MW |
| 24 Oct, 06:00 | 723 MW | 730 MW |
| 24 Oct, 07:00 | 735 MW | 732 MW |
| 24 Oct, 08:00 | 736 MW | 732 MW |
| 24 Oct, 09:00 | 721 MW | 719 MW |
| 24 Oct, 10:00 | 705 MW | 708 MW |
| 24 Oct, 11:00 | 691 MW | 701 MW |
| 24 Oct, 12:00 | 680 MW | 690 MW |
| 24 Oct, 13:00 | 672 MW | 678 MW |
| 24 Oct, 14:00 | 662 MW | 665 MW |
| 24 Oct, 15:00 | 654 MW | 658 MW |
| 24 Oct, 16:00 | 653 MW | 654 MW |
| 24 Oct, 17:00 | 661 MW | 658 MW |
| 24 Oct, 18:00 | 672 MW | 663 MW |
| 24 Oct, 19:00 | 675 MW | 664 MW |
| 24 Oct, 20:00 | 674 MW | 665 MW |
| 24 Oct, 21:00 | 674 MW | 662 MW |
| 24 Oct, 22:00 | 669 MW | 660 MW |
| 24 Oct, 23:00 | 664 MW | 657 MW |
| 25 Oct, 00:00 | 661 MW | 658 MW |
| 25 Oct, 01:00 | 663 MW | 661 MW |
| 25 Oct, 02:00 | 665 MW | 657 MW |
| 25 Oct, 03:00 | 667 MW | 659 MW |
| 25 Oct, 04:00 | 667 MW | 666 MW |
| 25 Oct, 05:00 | 676 MW | 678 MW |
| 25 Oct, 06:00 | 685 MW | 685 MW |
| 25 Oct, 07:00 | 696 MW | 690 MW |
| 25 Oct, 08:00 | 705 MW | 692 MW |
| 25 Oct, 09:00 | 698 MW | 689 MW |
| 25 Oct, 10:00 | 684 MW | 679 MW |
| 25 Oct, 11:00 | 676 MW | 669 MW |
| 25 Oct, 12:00 | 672 MW | 657 MW |
| 25 Oct, 13:00 | 669 MW | 649 MW |
| 25 Oct, 14:00 | 668 MW | 639 MW |
| 25 Oct, 15:00 | 668 MW | 633 MW |
| 25 Oct, 16:00 | 670 MW | 633 MW |
| 25 Oct, 17:00 | 675 MW | 643 MW |
| 25 Oct, 18:00 | 684 MW | 655 MW |
| 25 Oct, 19:00 | 683 MW | 657 MW |
| 25 Oct, 20:00 | 680 MW | 658 MW |
| 25 Oct, 21:00 | 671 MW | 652 MW |
| 25 Oct, 22:00 | 661 MW | 644 MW |
| 25 Oct, 23:00 | 652 MW | 636 MW |
| 26 Oct, 00:00 | 650 MW | 636 MW |
| 26 Oct, 01:00 | 650 MW | 633 MW |
| 26 Oct, 02:00 | 655 MW | 631 MW |
| 26 Oct, 03:00 | 662 MW | 635 MW |
| 26 Oct, 04:00 | 669 MW | 644 MW |
| 26 Oct, 05:00 | 692 MW | 660 MW |
| 26 Oct, 06:00 | 713 MW | 681 MW |
| 26 Oct, 07:00 | 721 MW | 696 MW |
| 26 Oct, 08:00 | 726 MW | 703 MW |
| 26 Oct, 09:00 | 725 MW | 703 MW |
| 26 Oct, 10:00 | 724 MW | 698 MW |
| 26 Oct, 11:00 | 720 MW | 693 MW |
| 26 Oct, 12:00 | 710 MW | 690 MW |
| 26 Oct, 13:00 | 702 MW | 685 MW |
| 26 Oct, 14:00 | 692 MW | 679 MW |
| 26 Oct, 15:00 | 693 MW | 676 MW |
| 26 Oct, 16:00 | 694 MW | 678 MW |
| 26 Oct, 17:00 | 693 MW | 686 MW |
| 26 Oct, 18:00 | 704 MW | 691 MW |
| 26 Oct, 19:00 | 701 MW | 690 MW |
| 26 Oct, 20:00 | 698 MW | 688 MW |
| 26 Oct, 21:00 | 690 MW | 680 MW |
| 26 Oct, 22:00 | 675 MW | 672 MW |
| 26 Oct, 23:00 | 669 MW | 665 MW |
| 27 Oct, 00:00 | 670 MW | 660 MW |
| 27 Oct, 01:00 | 669 MW | 661 MW |
| 27 Oct, 02:00 | 672 MW | 659 MW |
| 27 Oct, 03:00 | 678 MW | 670 MW |
| 27 Oct, 04:00 | 688 MW | 673 MW |
| 27 Oct, 05:00 | 712 MW | 694 MW |
| 27 Oct, 06:00 | 733 MW | 712 MW |
| 27 Oct, 07:00 | 738 MW | 723 MW |
| 27 Oct, 08:00 | 732 MW | 725 MW |
| 27 Oct, 09:00 | 727 MW | 722 MW |
| 27 Oct, 10:00 | 723 MW | 713 MW |
| 27 Oct, 11:00 | 712 MW | 708 MW |
| 27 Oct, 12:00 | 707 MW | 698 MW |
| 27 Oct, 13:00 | 700 MW | 688 MW |
| 27 Oct, 14:00 | 687 MW | 677 MW |
| 27 Oct, 15:00 | 687 MW | 674 MW |
| 27 Oct, 16:00 | 685 MW | 676 MW |
| 27 Oct, 17:00 | 691 MW | 680 MW |
| 27 Oct, 18:00 | 703 MW | 690 MW |
| 27 Oct, 19:00 | 699 MW | 689 MW |
| 27 Oct, 20:00 | 697 MW | 686 MW |
| 27 Oct, 21:00 | 688 MW | 680 MW |
| 27 Oct, 22:00 | 675 MW | 670 MW |
| 27 Oct, 23:00 | 670 MW | 664 MW |
| 28 Oct, 00:00 | 670 MW | 652 MW |
| 28 Oct, 01:00 | 670 MW | 656 MW |
| 28 Oct, 02:00 | 669 MW | 653 MW |
| 28 Oct, 03:00 | 668 MW | 656 MW |
| 28 Oct, 04:00 | 675 MW | 666 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.
Related
Cite this page
APA 7
World Power Monitor. (2026). GCPD Demand Forecast Accuracy: Error, Bias and Worst Miss. https://worldpowermonitor.com/forecast-accuracy/gcpd/
Plain text
World Power Monitor. GCPD 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/gcpd/
BibTeX
@misc{wpm_forecast_accuracy_gcpd_2026,
title = {{GCPD 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/gcpd/}
} Permalink: https://worldpowermonitor.com/forecast-accuracy/gcpd/
The Copy buttons add today's date as the access date.