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

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

The day-ahead demand forecast for EPE was off by 3.2% on average (mean absolute percentage error) over 695 hours from 21 August to 20 September 2026, and 82% of hours landed within 5% of the reading. Its bias was -1.9%: it ran low on average, an under forecast. The largest miss was 272 MW (15.7%) too low at 17 Sept 2026, 21:00 MDT (UTC-06:00). Dates and times are local (America/Denver).

Key Facts

  • The day-ahead demand forecast for EPE was off by 3.2% on average (mean absolute percentage error) over 695 hours from 21 August to 20 September 2026, and 82% of hours landed within 5% of the reading. Its bias was -1.9%: it ran low on average, an under forecast. The largest miss was 272 MW (15.7%) too low at 17 Sept 2026, 21:00 MDT (UTC-06:00).
  • Across 53 US grids ranked by average error over their own latest 30 day windows, EPE came 19 (1 is the smallest error).
  • On average the forecast differed from reported demand by 49 MW, against average demand of 1,505 MW.
  • The forecast was above reported demand in 23% of compared hours.

Forecast Error at a Glance

695 hours from 21 August to 20 September 2026
Average error3.2%
Bias-1.9%
Hours within 5%82%
Worst miss272 MW

Average error is the mean absolute percentage gap between the forecast and reported demand. Bias is the signed mean (-30 MW per hour on average): the forecast ran low on average, an under forecast. The worst miss was 272 MW (15.7%) too low at 17 Sept 2026, 21:00 MDT (UTC-06:00): forecast 1,455 MW, reported 1,727 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)
EPE day-ahead demand forecast and reported demand by hour Hourly reported demand and the day-ahead forecast for EPE over the last 7 days of the window, to 20 Sept 2026, 19:00 MDT (UTC-06:00). Gaps are hours with a missing, zero or implausible report. 0 625 1,250 1,875 2,500 13 Sept, 20:0014 Sept, 20:0015 Sept, 20:0016 Sept, 20:0017 Sept, 20:0018 Sept, 20:0019 Sept, 20:00
Hourly reported demand and the day-ahead forecast for EPE over the last 7 days of the window, to 20 Sept 2026, 19:00 MDT (UTC-06:00). Gaps are hours with a missing, zero or implausible report.
Data to 2026-09-20
EPE day-ahead demand forecast and reported demand by hour
Local hourReported demandDay-ahead forecast
13 Sept, 20:001,787 MW1,742 MW
13 Sept, 21:001,639 MW1,613 MW
13 Sept, 22:001,485 MW1,472 MW
13 Sept, 23:001,342 MW1,335 MW
14 Sept, 00:001,215 MW1,231 MW
14 Sept, 01:001,138 MW1,145 MW
14 Sept, 02:001,088 MW1,071 MW
14 Sept, 03:001,206 MW1,036 MW
14 Sept, 04:001,193 MW1,027 MW
14 Sept, 05:001,224 MW1,049 MW
14 Sept, 06:001,277 MW1,098 MW
14 Sept, 07:001,297 MW1,129 MW
14 Sept, 08:001,322 MW1,206 MW
14 Sept, 09:001,280 MW1,291 MW
14 Sept, 10:001,371 MW1,407 MW
14 Sept, 11:001,503 MW1,534 MW
14 Sept, 12:001,620 MW1,671 MW
14 Sept, 13:001,714 MW1,797 MW
14 Sept, 14:001,865 MW1,894 MW
14 Sept, 15:001,910 MW1,967 MW
14 Sept, 16:002,010 MW2,006 MW
14 Sept, 17:002,052 MW1,985 MW
14 Sept, 18:001,956 MW1,918 MW
14 Sept, 19:001,843 MW1,808 MW
14 Sept, 20:001,750 MW1,706 MW
14 Sept, 21:001,644 MW1,569 MW
14 Sept, 22:001,506 MW1,422 MW
14 Sept, 23:001,342 MW1,285 MW
15 Sept, 00:001,200 MW1,185 MW
15 Sept, 01:001,113 MW1,146 MW
15 Sept, 02:001,079 MW1,068 MW
15 Sept, 03:001,041 MW1,031 MW
15 Sept, 04:001,038 MW1,021 MW
15 Sept, 05:001,076 MW1,046 MW
15 Sept, 06:001,123 MW1,098 MW
15 Sept, 07:001,137 MW1,132 MW
15 Sept, 08:001,171 MW1,191 MW
15 Sept, 09:001,230 MW1,276 MW
15 Sept, 10:001,278 MW1,384 MW
15 Sept, 11:001,395 MW1,508 MW
15 Sept, 12:001,579 MW1,625 MW
15 Sept, 13:001,653 MW1,759 MW
15 Sept, 14:001,717 MW1,868 MW
15 Sept, 15:001,860 MW1,946 MW
15 Sept, 16:002,096 MW1,986 MW
15 Sept, 17:001,928 MW1,969 MW
15 Sept, 18:001,855 MW1,899 MW
15 Sept, 19:001,751 MW1,799 MW
15 Sept, 20:001,663 MW1,701 MW
15 Sept, 21:001,552 MW1,567 MW
15 Sept, 22:001,503 MW1,418 MW
15 Sept, 23:001,301 MW1,285 MW
16 Sept, 00:001,151 MW1,185 MW
16 Sept, 01:001,095 MW1,088 MW
16 Sept, 02:001,062 MW1,032 MW
16 Sept, 03:001,021 MW997 MW
16 Sept, 04:001,003 MW988 MW
16 Sept, 05:001,020 MW1,007 MW
16 Sept, 06:001,085 MW1,053 MW
16 Sept, 07:001,087 MW1,076 MW
16 Sept, 08:001,133 MW1,126 MW
16 Sept, 09:001,168 MW1,192 MW
16 Sept, 10:001,222 MW1,290 MW
16 Sept, 11:001,300 MW1,400 MW
16 Sept, 12:001,407 MW1,515 MW
16 Sept, 13:001,513 MW1,642 MW
16 Sept, 14:001,637 MW1,741 MW
16 Sept, 15:001,815 MW1,811 MW
16 Sept, 16:001,812 MW1,839 MW
16 Sept, 17:001,773 MW1,815 MW
16 Sept, 18:001,776 MW1,730 MW
16 Sept, 19:001,625 MW1,643 MW
16 Sept, 20:001,507 MW1,556 MW
16 Sept, 21:001,372 MW1,447 MW
16 Sept, 22:001,289 MW1,318 MW
16 Sept, 23:001,188 MW1,199 MW
17 Sept, 00:001,122 MW1,109 MW
17 Sept, 01:001,065 MW1,037 MW
17 Sept, 02:001,028 MW1,004 MW
17 Sept, 03:001,010 MW974 MW
17 Sept, 04:00998 MW969 MW
17 Sept, 05:001,025 MW991 MW
17 Sept, 06:001,073 MW1,040 MW
17 Sept, 07:001,069 MW1,056 MW
17 Sept, 08:001,096 MW1,110 MW
17 Sept, 09:001,159 MW1,175 MW
17 Sept, 10:001,315 MW1,273 MW
17 Sept, 11:001,359 MW1,386 MW
17 Sept, 12:001,480 MW1,509 MW
17 Sept, 13:001,768 MW1,634 MW
17 Sept, 14:001,793 MW1,740 MW
17 Sept, 15:001,841 MW1,821 MW
17 Sept, 16:001,894 MW1,874 MW
17 Sept, 17:001,852 MW1,857 MW
17 Sept, 18:001,807 MW1,759 MW
17 Sept, 19:001,672 MW1,671 MW
17 Sept, 20:001,557 MW1,573 MW
17 Sept, 21:001,727 MW1,455 MW
17 Sept, 22:001,328 MW1,322 MW
17 Sept, 23:001,165 MW1,199 MW
18 Sept, 00:001,076 MW1,103 MW
18 Sept, 01:001,010 MW1,023 MW
18 Sept, 02:00977 MW958 MW
18 Sept, 03:00961 MW930 MW
18 Sept, 04:00954 MW926 MW
18 Sept, 05:00974 MW948 MW
18 Sept, 06:001,031 MW995 MW
18 Sept, 07:001,044 MW1,017 MW
18 Sept, 08:001,094 MW1,067 MW
18 Sept, 09:001,120 MW1,133 MW
18 Sept, 10:001,258 MW1,231 MW
18 Sept, 11:001,320 MW1,345 MW
18 Sept, 12:001,421 MW1,464 MW
18 Sept, 13:001,544 MW1,584 MW
18 Sept, 14:001,683 MW1,703 MW
18 Sept, 15:001,800 MW1,782 MW
18 Sept, 16:001,826 MW1,815 MW
18 Sept, 17:001,807 MW1,785 MW
18 Sept, 18:001,732 MW1,672 MW
18 Sept, 19:001,687 MW1,575 MW
18 Sept, 20:001,577 MW1,477 MW
18 Sept, 21:001,408 MW1,372 MW
18 Sept, 22:001,316 MW1,265 MW
18 Sept, 23:001,199 MW1,167 MW
19 Sept, 00:001,098 MW1,079 MW
19 Sept, 01:001,020 MW1,048 MW
19 Sept, 02:00977 MW985 MW
19 Sept, 03:00955 MW945 MW
19 Sept, 04:00931 MW923 MW
19 Sept, 05:00926 MW913 MW
19 Sept, 06:00930 MW918 MW
19 Sept, 07:00933 MW916 MW
19 Sept, 08:00973 MW973 MW
19 Sept, 09:001,043 MW1,048 MW
19 Sept, 10:001,146 MW1,155 MW
19 Sept, 11:001,252 MW1,273 MW
19 Sept, 12:001,350 MW1,394 MW
19 Sept, 13:001,483 MW1,504 MW
19 Sept, 14:001,570 MW1,603 MW
19 Sept, 15:001,680 MW1,692 MW
19 Sept, 16:001,834 MW1,728 MW
19 Sept, 17:001,740 MW1,715 MW
19 Sept, 18:001,720 MW1,621 MW
19 Sept, 19:001,587 MW1,554 MW
19 Sept, 20:001,475 MW1,452 MW
19 Sept, 21:001,366 MW1,347 MW
19 Sept, 22:001,268 MW1,244 MW
19 Sept, 23:001,170 MW1,149 MW
20 Sept, 00:001,071 MW1,067 MW
20 Sept, 01:00968 MW1,014 MW
20 Sept, 02:00915 MW942 MW
20 Sept, 03:00886 MW901 MW
20 Sept, 04:00857 MW875 MW
20 Sept, 05:00841 MW861 MW
20 Sept, 06:00833 MW858 MW
20 Sept, 07:00826 MW844 MW
20 Sept, 08:00875 MW894 MW
20 Sept, 09:00952 MW965 MW
20 Sept, 10:001,051 MW1,068 MW
20 Sept, 11:001,175 MW1,188 MW
20 Sept, 12:001,302 MW1,316 MW
20 Sept, 13:001,432 MW1,432 MW
20 Sept, 14:001,557 MW1,541 MW
20 Sept, 15:001,641 MW1,618 MW
20 Sept, 16:001,688 MW1,669 MW
20 Sept, 17:001,706 MW1,666 MW
20 Sept, 18:001,638 MW1,610 MW
20 Sept, 19:001,537 MW1,530 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.