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

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

The day-ahead demand forecast for BPA was off by 1.7% on average (mean absolute percentage error) over 695 hours from 21 August to 20 September 2026, and 100% of hours landed within 5% of the reading. Its bias was +0.9%: it ran high on average, an over forecast. The largest miss was 3,807 MW (116.0%) too high at 11 Sept 2026, 09:00 PDT (UTC-07:00). Dates and times are local (America/Los_Angeles).

Key Facts

  • The day-ahead demand forecast for BPA was off by 1.7% on average (mean absolute percentage error) over 695 hours from 21 August to 20 September 2026, and 100% of hours landed within 5% of the reading. Its bias was +0.9%: it ran high on average, an over forecast. The largest miss was 3,807 MW (116.0%) too high at 11 Sept 2026, 09:00 PDT (UTC-07:00).
  • Across 53 US grids ranked by average error over their own latest 30 day windows, BPA came 3 (1 is the smallest error).
  • On average the forecast differed from reported demand by 110 MW, against average demand of 6,720 MW.
  • The forecast was above reported demand in 66% of compared hours.

Forecast Error at a Glance

695 hours from 21 August to 20 September 2026
Average error1.7%
Bias+0.9%
Hours within 5%100%
Worst miss3,807 MW

Average error is the mean absolute percentage gap between the forecast and reported demand. Bias is the signed mean (+54 MW per hour on average): the forecast ran high on average, an over forecast. The worst miss was 3,807 MW (116.0%) too high at 11 Sept 2026, 09:00 PDT (UTC-07:00): forecast 7,089 MW, reported 3,282 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, 18:00 PDT (UTC-07:00)
BPA day-ahead demand forecast and reported demand by hour Hourly reported demand and the day-ahead forecast for BPA over the last 7 days of the window, to 20 Sept 2026, 18:00 PDT (UTC-07:00). Gaps are hours with a missing, zero or implausible report. 0 2,500 5,000 7,500 10,000 13 Sept, 19:0014 Sept, 19:0015 Sept, 19:0016 Sept, 19:0017 Sept, 19:0018 Sept, 19:0019 Sept, 19:00
Hourly reported demand and the day-ahead forecast for BPA over the last 7 days of the window, to 20 Sept 2026, 18:00 PDT (UTC-07:00). Gaps are hours with a missing, zero or implausible report.
Data to 2026-09-20
BPA day-ahead demand forecast and reported demand by hour
Local hourReported demandDay-ahead forecast
13 Sept, 19:006,879 MW6,890 MW
13 Sept, 20:006,807 MW6,846 MW
13 Sept, 21:006,511 MW6,592 MW
13 Sept, 22:006,206 MW6,276 MW
13 Sept, 23:005,865 MW5,959 MW
14 Sept, 00:005,720 MW5,744 MW
14 Sept, 01:005,570 MW5,609 MW
14 Sept, 02:005,546 MW5,546 MW
14 Sept, 03:005,537 MW5,546 MW
14 Sept, 04:005,711 MW5,712 MW
14 Sept, 05:006,035 MW6,106 MW
14 Sept, 06:006,470 MW6,644 MW
14 Sept, 07:006,740 MW6,886 MW
14 Sept, 08:006,805 MW6,900 MW
14 Sept, 09:006,771 MW6,886 MW
14 Sept, 10:006,824 MW6,870 MW
14 Sept, 11:006,751 MW6,874 MW
14 Sept, 12:006,735 MW6,882 MW
14 Sept, 13:006,766 MW6,891 MW
14 Sept, 14:006,752 MW6,883 MW
14 Sept, 15:006,742 MW6,894 MW
14 Sept, 16:006,916 MW6,963 MW
14 Sept, 17:007,090 MW7,100 MW
14 Sept, 18:007,117 MW7,174 MW
14 Sept, 19:007,106 MW7,259 MW
14 Sept, 20:007,026 MW7,179 MW
14 Sept, 21:006,640 MW6,853 MW
14 Sept, 22:006,355 MW6,471 MW
14 Sept, 23:006,006 MW6,149 MW
15 Sept, 00:005,783 MW5,961 MW
15 Sept, 01:005,661 MW5,802 MW
15 Sept, 02:005,612 MW5,738 MW
15 Sept, 03:005,602 MW5,724 MW
15 Sept, 04:005,731 MW5,849 MW
15 Sept, 05:006,088 MW6,202 MW
15 Sept, 06:006,522 MW6,683 MW
15 Sept, 07:006,751 MW6,933 MW
15 Sept, 08:006,817 MW6,966 MW
15 Sept, 09:006,826 MW6,904 MW
15 Sept, 10:006,818 MW6,880 MW
15 Sept, 11:006,769 MW6,841 MW
15 Sept, 12:006,792 MW6,819 MW
15 Sept, 13:006,736 MW6,811 MW
15 Sept, 14:006,713 MW6,775 MW
15 Sept, 15:006,711 MW6,770 MW
15 Sept, 16:006,812 MW6,875 MW
15 Sept, 17:006,884 MW7,008 MW
15 Sept, 18:006,986 MW7,064 MW
15 Sept, 19:007,035 MW7,117 MW
15 Sept, 20:007,006 MW7,055 MW
15 Sept, 21:006,659 MW6,757 MW
15 Sept, 22:006,336 MW6,414 MW
15 Sept, 23:006,027 MW6,083 MW
16 Sept, 00:005,858 MW5,893 MW
16 Sept, 01:005,732 MW5,717 MW
16 Sept, 02:005,695 MW5,656 MW
16 Sept, 03:005,681 MW5,650 MW
16 Sept, 04:005,811 MW5,790 MW
16 Sept, 05:006,165 MW6,152 MW
16 Sept, 06:006,605 MW6,639 MW
16 Sept, 07:006,843 MW6,880 MW
16 Sept, 08:006,880 MW6,902 MW
16 Sept, 09:006,788 MW6,902 MW
16 Sept, 10:006,768 MW6,876 MW
16 Sept, 11:006,773 MW6,888 MW
16 Sept, 12:006,777 MW6,953 MW
16 Sept, 13:006,878 MW7,032 MW
16 Sept, 14:006,790 MW7,101 MW
16 Sept, 15:007,010 MW7,195 MW
16 Sept, 16:007,160 MW7,359 MW
16 Sept, 17:007,292 MW7,433 MW
16 Sept, 18:007,310 MW7,416 MW
16 Sept, 19:007,296 MW7,390 MW
16 Sept, 20:007,115 MW7,263 MW
16 Sept, 21:006,728 MW6,915 MW
16 Sept, 22:006,359 MW6,536 MW
16 Sept, 23:006,182 MW6,182 MW
17 Sept, 00:005,754 MWn/a
17 Sept, 01:005,642 MWn/a
17 Sept, 02:005,554 MWn/a
17 Sept, 03:005,515 MWn/a
17 Sept, 04:005,675 MWn/a
17 Sept, 05:006,001 MWn/a
17 Sept, 06:006,434 MWn/a
17 Sept, 07:006,679 MWn/a
17 Sept, 08:006,768 MWn/a
17 Sept, 09:006,721 MWn/a
17 Sept, 10:006,735 MWn/a
17 Sept, 11:006,779 MWn/a
17 Sept, 12:006,775 MWn/a
17 Sept, 13:006,879 MWn/a
17 Sept, 14:006,916 MWn/a
17 Sept, 15:006,999 MWn/a
17 Sept, 16:007,137 MWn/a
17 Sept, 17:007,247 MWn/a
17 Sept, 18:007,219 MWn/a
17 Sept, 19:007,221 MWn/a
17 Sept, 20:007,073 MWn/a
17 Sept, 21:006,752 MWn/a
17 Sept, 22:006,417 MWn/a
17 Sept, 23:006,063 MWn/a
18 Sept, 00:005,772 MW5,885 MW
18 Sept, 01:005,648 MW5,631 MW
18 Sept, 02:005,592 MW5,511 MW
18 Sept, 03:005,577 MW5,481 MW
18 Sept, 04:005,657 MW5,567 MW
18 Sept, 05:005,940 MW5,826 MW
18 Sept, 06:006,351 MW6,225 MW
18 Sept, 07:006,621 MW6,500 MW
18 Sept, 08:006,703 MW6,625 MW
18 Sept, 09:006,793 MW6,648 MW
18 Sept, 10:006,744 MW6,689 MW
18 Sept, 11:006,793 MW6,742 MW
18 Sept, 12:006,789 MW6,770 MW
18 Sept, 13:006,788 MW6,823 MW
18 Sept, 14:006,786 MW6,866 MW
18 Sept, 15:006,869 MW6,932 MW
18 Sept, 16:007,015 MW7,032 MW
18 Sept, 17:007,105 MW7,089 MW
18 Sept, 18:007,059 MW7,028 MW
18 Sept, 19:006,988 MW6,955 MW
18 Sept, 20:006,845 MW6,777 MW
18 Sept, 21:006,565 MW6,493 MW
18 Sept, 22:006,272 MW6,203 MW
18 Sept, 23:005,968 MW5,911 MW
19 Sept, 00:005,802 MW5,803 MW
19 Sept, 01:005,624 MW5,614 MW
19 Sept, 02:005,541 MW5,528 MW
19 Sept, 03:005,463 MW5,501 MW
19 Sept, 04:005,512 MW5,520 MW
19 Sept, 05:005,621 MW5,636 MW
19 Sept, 06:005,823 MW5,810 MW
19 Sept, 07:006,049 MW6,037 MW
19 Sept, 08:006,303 MW6,280 MW
19 Sept, 09:006,435 MW6,422 MW
19 Sept, 10:006,494 MW6,466 MW
19 Sept, 11:006,536 MW6,486 MW
19 Sept, 12:006,531 MW6,467 MW
19 Sept, 13:006,551 MW6,490 MW
19 Sept, 14:006,540 MW6,534 MW
19 Sept, 15:006,646 MW6,606 MW
19 Sept, 16:006,757 MW6,764 MW
19 Sept, 17:006,872 MW6,847 MW
19 Sept, 18:006,888 MW6,831 MW
19 Sept, 19:006,826 MW6,801 MW
19 Sept, 20:006,732 MW6,641 MW
19 Sept, 21:006,432 MW6,356 MW
19 Sept, 22:006,137 MW6,102 MW
19 Sept, 23:005,858 MW5,825 MW
20 Sept, 00:005,681 MW5,692 MW
20 Sept, 01:005,527 MW5,521 MW
20 Sept, 02:005,452 MW5,441 MW
20 Sept, 03:005,424 MW5,404 MW
20 Sept, 04:005,447 MW5,433 MW
20 Sept, 05:005,577 MW5,530 MW
20 Sept, 06:005,764 MW5,697 MW
20 Sept, 07:006,004 MW5,921 MW
20 Sept, 08:006,240 MW6,162 MW
20 Sept, 09:006,408 MW6,300 MW
20 Sept, 10:006,445 MW6,360 MW
20 Sept, 11:006,474 MW6,415 MW
20 Sept, 12:006,516 MW6,485 MW
20 Sept, 13:006,556 MW6,548 MW
20 Sept, 14:006,667 MW6,628 MW
20 Sept, 15:006,837 MW6,751 MW
20 Sept, 16:007,017 MW6,943 MW
20 Sept, 17:007,226 MW7,083 MW
20 Sept, 18:008,554 MW7,107 MW

Assumptions

  • Only hours with both a forecast and a positive demand reading count (695 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.