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

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

The day-ahead demand forecast for TEPC was off by 4.0% on average (mean absolute percentage error) over 719 hours from 21 August to 20 September 2026, and 74% of hours landed within 5% of the reading. Its bias was +0.4%: it ran close to balanced on average. The largest miss was 821 MW (55.4%) too high at 31 Aug 2026, 15:00 MST (UTC-07:00). Dates and times are local (America/Phoenix).

Key Facts

  • The day-ahead demand forecast for TEPC was off by 4.0% on average (mean absolute percentage error) over 719 hours from 21 August to 20 September 2026, and 74% of hours landed within 5% of the reading. Its bias was +0.4%: it ran close to balanced on average. The largest miss was 821 MW (55.4%) too high at 31 Aug 2026, 15:00 MST (UTC-07:00).
  • Across 53 US grids ranked by average error over their own latest 30 day windows, TEPC came 27 (1 is the smallest error).
  • On average the forecast differed from reported demand by 86 MW, against average demand of 2,118 MW.
  • The forecast was above reported demand in 51% of compared hours.

Forecast Error at a Glance

719 hours from 21 August to 20 September 2026
Average error4.0%
Bias+0.4%
Hours within 5%74%
Worst miss821 MW

Average error is the mean absolute percentage gap between the forecast and reported demand. Bias is the signed mean (+2 MW per hour on average): the forecast ran close to balanced on average. The worst miss was 821 MW (55.4%) too high at 31 Aug 2026, 15:00 MST (UTC-07:00): forecast 2,302 MW, reported 1,481 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 MST (UTC-07:00)
TEPC day-ahead demand forecast and reported demand by hour Hourly reported demand and the day-ahead forecast for TEPC over the last 7 days of the window, to 20 Sept 2026, 18:00 MST (UTC-07:00). Gaps are hours with a missing, zero or implausible report. 0 750 1,500 2,250 3,000 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 TEPC over the last 7 days of the window, to 20 Sept 2026, 18:00 MST (UTC-07:00). Gaps are hours with a missing, zero or implausible report.
Data to 2026-09-20
TEPC day-ahead demand forecast and reported demand by hour
Local hourReported demandDay-ahead forecast
13 Sept, 19:002,750 MW2,489 MW
13 Sept, 20:002,631 MW2,370 MW
13 Sept, 21:002,493 MW2,208 MW
13 Sept, 22:002,289 MW2,076 MW
13 Sept, 23:002,163 MW1,945 MW
14 Sept, 00:001,999 MW1,994 MW
14 Sept, 01:001,912 MW1,915 MW
14 Sept, 02:001,837 MW1,851 MW
14 Sept, 03:001,804 MW1,811 MW
14 Sept, 04:001,803 MW1,795 MW
14 Sept, 05:001,850 MW1,834 MW
14 Sept, 06:002,061 MW1,906 MW
14 Sept, 07:001,920 MW1,886 MW
14 Sept, 08:001,913 MW1,889 MW
14 Sept, 09:002,016 MW1,964 MW
14 Sept, 10:002,063 MW2,052 MW
14 Sept, 11:002,174 MW2,153 MW
14 Sept, 12:002,112 MW2,215 MW
14 Sept, 13:002,521 MW2,376 MW
14 Sept, 14:002,624 MW2,425 MW
14 Sept, 15:002,741 MW2,479 MW
14 Sept, 16:002,627 MW2,497 MW
14 Sept, 17:002,489 MW2,504 MW
14 Sept, 18:002,355 MW2,412 MW
14 Sept, 19:002,296 MW2,343 MW
14 Sept, 20:002,207 MW2,264 MW
14 Sept, 21:002,106 MW2,152 MW
14 Sept, 22:001,952 MW2,012 MW
14 Sept, 23:001,799 MW1,880 MW
15 Sept, 00:001,726 MW1,729 MW
15 Sept, 01:001,665 MW1,623 MW
15 Sept, 02:001,609 MW1,601 MW
15 Sept, 03:001,537 MW1,577 MW
15 Sept, 04:001,517 MW1,585 MW
15 Sept, 05:001,558 MW1,636 MW
15 Sept, 06:001,617 MW1,715 MW
15 Sept, 07:001,657 MW1,714 MW
15 Sept, 08:001,641 MW1,720 MW
15 Sept, 09:001,638 MW1,756 MW
15 Sept, 10:001,782 MW1,823 MW
15 Sept, 11:001,917 MW1,873 MW
15 Sept, 12:002,011 MW1,927 MW
15 Sept, 13:002,037 MW2,077 MW
15 Sept, 14:002,105 MW2,170 MW
15 Sept, 15:002,205 MW2,228 MW
15 Sept, 16:002,371 MW2,256 MW
15 Sept, 17:002,413 MW2,344 MW
15 Sept, 18:002,368 MW2,240 MW
15 Sept, 19:002,302 MW2,187 MW
15 Sept, 20:002,214 MW2,118 MW
15 Sept, 21:002,093 MW2,025 MW
15 Sept, 22:001,932 MW1,903 MW
15 Sept, 23:001,811 MW1,795 MW
16 Sept, 00:001,746 MW1,722 MW
16 Sept, 01:001,668 MW1,649 MW
16 Sept, 02:001,623 MW1,633 MW
16 Sept, 03:001,598 MW1,605 MW
16 Sept, 04:001,590 MW1,602 MW
16 Sept, 05:001,625 MW1,644 MW
16 Sept, 06:001,662 MW1,728 MW
16 Sept, 07:001,681 MW1,717 MW
16 Sept, 08:001,730 MW1,726 MW
16 Sept, 09:001,777 MW1,775 MW
16 Sept, 10:001,854 MW1,825 MW
16 Sept, 11:001,875 MW1,855 MW
16 Sept, 12:001,870 MW1,871 MW
16 Sept, 13:002,019 MW1,978 MW
16 Sept, 14:002,126 MW2,001 MW
16 Sept, 15:002,118 MW2,007 MW
16 Sept, 16:002,117 MW2,034 MW
16 Sept, 17:002,063 MW2,047 MW
16 Sept, 18:001,959 MW2,021 MW
16 Sept, 19:001,929 MW2,005 MW
16 Sept, 20:001,866 MW1,935 MW
16 Sept, 21:001,780 MW1,866 MW
16 Sept, 22:001,689 MW1,755 MW
16 Sept, 23:001,602 MW1,671 MW
17 Sept, 00:001,522 MW1,541 MW
17 Sept, 01:001,455 MW1,485 MW
17 Sept, 02:001,421 MW1,429 MW
17 Sept, 03:001,404 MW1,413 MW
17 Sept, 04:001,426 MW1,427 MW
17 Sept, 05:001,483 MW1,483 MW
17 Sept, 06:001,534 MW1,559 MW
17 Sept, 07:001,591 MW1,564 MW
17 Sept, 08:001,587 MW1,565 MW
17 Sept, 09:001,599 MW1,562 MW
17 Sept, 10:001,652 MW1,622 MW
17 Sept, 11:001,746 MW1,684 MW
17 Sept, 12:001,860 MW1,761 MW
17 Sept, 13:001,974 MW1,944 MW
17 Sept, 14:002,098 MW2,084 MW
17 Sept, 15:002,231 MW2,203 MW
17 Sept, 16:002,358 MW2,303 MW
17 Sept, 17:002,399 MW2,396 MW
17 Sept, 18:002,330 MW2,309 MW
17 Sept, 19:002,242 MW2,243 MW
17 Sept, 20:002,125 MW2,162 MW
17 Sept, 21:002,006 MW2,047 MW
17 Sept, 22:001,865 MW1,910 MW
17 Sept, 23:001,748 MW1,792 MW
18 Sept, 00:001,656 MW1,650 MW
18 Sept, 01:001,599 MW1,564 MW
18 Sept, 02:001,554 MW1,533 MW
18 Sept, 03:001,520 MW1,512 MW
18 Sept, 04:001,520 MW1,518 MW
18 Sept, 05:001,565 MW1,564 MW
18 Sept, 06:001,617 MW1,655 MW
18 Sept, 07:001,642 MW1,640 MW
18 Sept, 08:001,656 MW1,655 MW
18 Sept, 09:001,711 MW1,684 MW
18 Sept, 10:001,820 MW1,764 MW
18 Sept, 11:001,934 MW1,865 MW
18 Sept, 12:002,071 MW1,932 MW
18 Sept, 13:002,206 MW2,176 MW
18 Sept, 14:002,339 MW2,300 MW
18 Sept, 15:002,460 MW2,393 MW
18 Sept, 16:002,572 MW2,486 MW
18 Sept, 17:002,586 MW2,544 MW
18 Sept, 18:002,453 MW2,442 MW
18 Sept, 19:002,304 MW2,350 MW
18 Sept, 20:002,166 MW2,250 MW
18 Sept, 21:002,064 MW2,125 MW
18 Sept, 22:001,926 MW1,980 MW
18 Sept, 23:001,794 MW1,833 MW
19 Sept, 00:001,681 MW1,689 MW
19 Sept, 01:001,615 MW1,603 MW
19 Sept, 02:001,554 MW1,554 MW
19 Sept, 03:001,512 MW1,512 MW
19 Sept, 04:001,481 MW1,493 MW
19 Sept, 05:001,487 MW1,513 MW
19 Sept, 06:001,489 MW1,551 MW
19 Sept, 07:001,506 MW1,533 MW
19 Sept, 08:001,539 MW1,567 MW
19 Sept, 09:001,609 MW1,637 MW
19 Sept, 10:001,724 MW1,736 MW
19 Sept, 11:001,837 MW1,847 MW
19 Sept, 12:001,965 MW1,983 MW
19 Sept, 13:002,092 MW2,199 MW
19 Sept, 14:002,213 MW2,347 MW
19 Sept, 15:002,350 MW2,435 MW
19 Sept, 16:002,461 MW2,520 MW
19 Sept, 17:002,479 MW2,566 MW
19 Sept, 18:002,366 MW2,424 MW
19 Sept, 19:002,243 MW2,312 MW
19 Sept, 20:002,104 MW2,190 MW
19 Sept, 21:001,973 MW2,070 MW
19 Sept, 22:001,850 MW1,911 MW
19 Sept, 23:001,735 MW1,801 MW
20 Sept, 00:001,641 MW1,674 MW
20 Sept, 01:001,561 MW1,573 MW
20 Sept, 02:001,499 MW1,514 MW
20 Sept, 03:001,464 MW1,478 MW
20 Sept, 04:001,443 MW1,451 MW
20 Sept, 05:001,450 MW1,466 MW
20 Sept, 06:001,450 MW1,469 MW
20 Sept, 07:001,445 MW1,491 MW
20 Sept, 08:001,483 MW1,516 MW
20 Sept, 09:001,567 MW1,608 MW
20 Sept, 10:001,712 MW1,726 MW
20 Sept, 11:001,867 MW1,821 MW
20 Sept, 12:002,009 MW1,945 MW
20 Sept, 13:002,182 MW2,138 MW
20 Sept, 14:002,325 MW2,284 MW
20 Sept, 15:002,431 MW2,359 MW
20 Sept, 16:002,507 MW2,432 MW
20 Sept, 17:002,539 MW2,509 MW
20 Sept, 18:002,428 MW2,429 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.