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

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

The day-ahead demand forecast for SRP was off by 11.5% on average (mean absolute percentage error) over 719 hours from 21 August to 20 September 2026, and 41% of hours landed within 5% of the reading. Its bias was +10.1%: it ran high on average, an over forecast. The largest miss was 2,977 MW (82.1%) too high at 31 Aug 2026, 13:00 MST (UTC-07:00). Dates and times are local (America/Phoenix).

Key Facts

  • The day-ahead demand forecast for SRP was off by 11.5% on average (mean absolute percentage error) over 719 hours from 21 August to 20 September 2026, and 41% of hours landed within 5% of the reading. Its bias was +10.1%: it ran high on average, an over forecast. The largest miss was 2,977 MW (82.1%) too high at 31 Aug 2026, 13:00 MST (UTC-07:00).
  • Across 53 US grids ranked by average error over their own latest 30 day windows, SRP came 46 (1 is the smallest error).
  • On average the forecast differed from reported demand by 529 MW, against average demand of 5,406 MW.
  • The forecast was above reported demand in 76% of compared hours.

Forecast Error at a Glance

719 hours from 21 August to 20 September 2026
Average error11.5%
Bias+10.1%
Hours within 5%41%
Worst miss2,977 MW

Average error is the mean absolute percentage gap between the forecast and reported demand. Bias is the signed mean (+448 MW per hour on average): the forecast ran high on average, an over forecast. The worst miss was 2,977 MW (82.1%) too high at 31 Aug 2026, 13:00 MST (UTC-07:00): forecast 6,603 MW, reported 3,626 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)
SRP day-ahead demand forecast and reported demand by hour Hourly reported demand and the day-ahead forecast for SRP 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 2,000 4,000 6,000 8,000 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 SRP 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
SRP day-ahead demand forecast and reported demand by hour
Local hourReported demandDay-ahead forecast
13 Sept, 19:006,216 MW6,822 MW
13 Sept, 20:006,032 MW6,570 MW
13 Sept, 21:006,033 MW6,242 MW
13 Sept, 22:005,655 MW5,863 MW
13 Sept, 23:005,017 MW5,505 MW
14 Sept, 00:004,820 MW5,237 MW
14 Sept, 01:004,420 MW4,975 MW
14 Sept, 02:003,406 MW4,815 MW
14 Sept, 03:003,190 MW4,728 MW
14 Sept, 04:003,155 MW4,692 MW
14 Sept, 05:003,194 MW4,607 MW
14 Sept, 06:003,258 MW4,664 MW
14 Sept, 07:003,833 MW4,836 MW
14 Sept, 08:004,333 MW5,129 MW
14 Sept, 09:005,174 MW5,496 MW
14 Sept, 10:005,307 MW5,893 MW
14 Sept, 11:005,478 MW6,294 MW
14 Sept, 12:005,716 MW6,705 MW
14 Sept, 13:006,405 MW7,042 MW
14 Sept, 14:006,779 MW7,239 MW
14 Sept, 15:006,517 MW7,296 MW
14 Sept, 16:006,729 MW7,288 MW
14 Sept, 17:006,758 MW7,125 MW
14 Sept, 18:006,017 MW6,921 MW
14 Sept, 19:005,793 MW6,699 MW
14 Sept, 20:005,819 MW6,484 MW
14 Sept, 21:005,309 MW6,134 MW
14 Sept, 22:004,217 MW5,702 MW
14 Sept, 23:003,564 MW5,317 MW
15 Sept, 00:003,272 MW4,908 MW
15 Sept, 01:003,101 MW4,746 MW
15 Sept, 02:003,408 MW4,511 MW
15 Sept, 03:003,818 MW4,513 MW
15 Sept, 04:003,926 MW4,389 MW
15 Sept, 05:004,185 MW4,322 MW
15 Sept, 06:004,276 MW4,380 MW
15 Sept, 07:004,259 MW4,517 MW
15 Sept, 08:004,589 MW4,769 MW
15 Sept, 09:004,857 MW5,094 MW
15 Sept, 10:005,174 MW5,493 MW
15 Sept, 11:005,516 MW5,920 MW
15 Sept, 12:005,928 MW6,347 MW
15 Sept, 13:006,521 MW6,690 MW
15 Sept, 14:006,809 MW6,908 MW
15 Sept, 15:006,681 MW6,956 MW
15 Sept, 16:006,522 MW6,940 MW
15 Sept, 17:006,776 MW6,763 MW
15 Sept, 18:006,524 MW6,560 MW
15 Sept, 19:006,038 MW6,346 MW
15 Sept, 20:005,709 MW6,137 MW
15 Sept, 21:004,936 MW5,821 MW
15 Sept, 22:004,640 MW5,446 MW
15 Sept, 23:004,658 MW5,114 MW
16 Sept, 00:004,648 MW4,833 MW
16 Sept, 01:004,269 MW4,649 MW
16 Sept, 02:004,106 MW4,445 MW
16 Sept, 03:003,870 MW4,339 MW
16 Sept, 04:004,107 MW4,351 MW
16 Sept, 05:004,437 MW4,280 MW
16 Sept, 06:004,565 MW4,330 MW
16 Sept, 07:004,381 MW4,426 MW
16 Sept, 08:004,398 MW4,607 MW
16 Sept, 09:004,972 MW4,845 MW
16 Sept, 10:005,499 MW5,090 MW
16 Sept, 11:005,613 MW5,304 MW
16 Sept, 12:005,543 MW5,534 MW
16 Sept, 13:005,306 MW5,720 MW
16 Sept, 14:004,954 MW5,803 MW
16 Sept, 15:004,541 MW5,789 MW
16 Sept, 16:004,215 MW5,694 MW
16 Sept, 17:004,262 MW5,502 MW
16 Sept, 18:004,418 MW5,399 MW
16 Sept, 19:004,585 MW5,396 MW
16 Sept, 20:004,495 MW5,347 MW
16 Sept, 21:004,258 MW5,142 MW
16 Sept, 22:003,767 MW4,856 MW
16 Sept, 23:003,930 MW4,588 MW
17 Sept, 00:003,910 MW4,111 MW
17 Sept, 01:002,923 MW4,007 MW
17 Sept, 02:003,332 MW3,868 MW
17 Sept, 03:003,421 MW3,806 MW
17 Sept, 04:003,612 MW3,891 MW
17 Sept, 05:003,891 MW4,032 MW
17 Sept, 06:003,844 MW4,131 MW
17 Sept, 07:003,934 MW4,230 MW
17 Sept, 08:004,362 MW4,369 MW
17 Sept, 09:004,396 MW4,560 MW
17 Sept, 10:004,352 MW4,814 MW
17 Sept, 11:004,385 MW5,095 MW
17 Sept, 12:004,703 MW5,402 MW
17 Sept, 13:004,890 MW5,663 MW
17 Sept, 14:005,016 MW5,854 MW
17 Sept, 15:005,206 MW5,974 MW
17 Sept, 16:005,138 MW6,098 MW
17 Sept, 17:005,123 MW6,019 MW
17 Sept, 18:005,059 MW5,835 MW
17 Sept, 19:004,735 MW5,712 MW
17 Sept, 20:004,600 MW5,500 MW
17 Sept, 21:004,510 MW5,257 MW
17 Sept, 22:003,760 MW4,960 MW
17 Sept, 23:003,764 MW4,678 MW
18 Sept, 00:003,247 MW4,402 MW
18 Sept, 01:002,458 MW4,253 MW
18 Sept, 02:002,233 MW4,062 MW
18 Sept, 03:002,101 MW3,973 MW
18 Sept, 04:002,382 MW4,038 MW
18 Sept, 05:002,541 MW4,143 MW
18 Sept, 06:003,054 MW4,228 MW
18 Sept, 07:003,195 MW4,354 MW
18 Sept, 08:003,645 MW4,539 MW
18 Sept, 09:004,442 MW4,795 MW
18 Sept, 10:004,214 MW5,089 MW
18 Sept, 11:004,070 MW5,443 MW
18 Sept, 12:004,312 MW5,788 MW
18 Sept, 13:004,930 MW6,064 MW
18 Sept, 14:006,360 MW6,258 MW
18 Sept, 15:006,696 MW6,342 MW
18 Sept, 16:006,706 MW6,348 MW
18 Sept, 17:006,655 MW6,142 MW
18 Sept, 18:006,271 MW5,855 MW
18 Sept, 19:005,451 MW5,566 MW
18 Sept, 20:004,920 MW5,291 MW
18 Sept, 21:004,499 MW5,010 MW
18 Sept, 22:004,506 MW4,707 MW
18 Sept, 23:004,533 MW4,435 MW
19 Sept, 00:004,386 MW4,599 MW
19 Sept, 01:003,911 MW4,418 MW
19 Sept, 02:003,216 MW4,125 MW
19 Sept, 03:002,795 MW3,984 MW
19 Sept, 04:002,706 MW3,890 MW
19 Sept, 05:002,795 MW3,853 MW
19 Sept, 06:002,900 MW3,841 MW
19 Sept, 07:003,430 MW4,005 MW
19 Sept, 08:003,656 MW4,271 MW
19 Sept, 09:003,498 MW4,611 MW
19 Sept, 10:003,719 MW4,972 MW
19 Sept, 11:004,017 MW5,381 MW
19 Sept, 12:004,591 MW5,773 MW
19 Sept, 13:004,894 MW6,093 MW
19 Sept, 14:005,427 MW6,338 MW
19 Sept, 15:005,256 MW6,493 MW
19 Sept, 16:005,423 MW6,504 MW
19 Sept, 17:004,993 MW6,316 MW
19 Sept, 18:005,132 MW5,975 MW
19 Sept, 19:004,637 MW5,630 MW
19 Sept, 20:004,851 MW5,338 MW
19 Sept, 21:004,755 MW5,020 MW
19 Sept, 22:004,685 MW4,700 MW
19 Sept, 23:004,532 MW4,430 MW
20 Sept, 00:004,302 MW4,415 MW
20 Sept, 01:004,059 MW4,166 MW
20 Sept, 02:003,895 MW3,923 MW
20 Sept, 03:003,739 MW3,757 MW
20 Sept, 04:003,651 MW3,685 MW
20 Sept, 05:003,590 MW3,634 MW
20 Sept, 06:003,477 MW3,613 MW
20 Sept, 07:003,255 MW3,774 MW
20 Sept, 08:003,214 MW4,054 MW
20 Sept, 09:003,670 MW4,404 MW
20 Sept, 10:004,055 MW4,795 MW
20 Sept, 11:004,390 MW5,214 MW
20 Sept, 12:004,771 MW5,621 MW
20 Sept, 13:005,090 MW5,975 MW
20 Sept, 14:005,294 MW6,260 MW
20 Sept, 15:005,580 MW6,459 MW
20 Sept, 16:005,755 MW6,550 MW
20 Sept, 17:005,910 MW6,424 MW
20 Sept, 18:005,863 MW6,157 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.