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

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

The day-ahead demand forecast for AZPS was off by 9.8% on average (mean absolute percentage error) over 714 hours from 21 August to 20 September 2026, and 29% of hours landed within 5% of the reading. Its bias was -4.8%: it ran low on average, an under forecast. The largest miss was 4,278 MW (125.2%) too high at 22 Aug 2026, 19:00 MST (UTC-07:00). Dates and times are local (America/Phoenix).

Key Facts

  • The day-ahead demand forecast for AZPS was off by 9.8% on average (mean absolute percentage error) over 714 hours from 21 August to 20 September 2026, and 29% of hours landed within 5% of the reading. Its bias was -4.8%: it ran low on average, an under forecast. The largest miss was 4,278 MW (125.2%) too high at 22 Aug 2026, 19:00 MST (UTC-07:00).
  • Across 53 US grids ranked by average error over their own latest 30 day windows, AZPS came 44 (1 is the smallest error).
  • On average the forecast differed from reported demand by 603 MW, against average demand of 6,387 MW.
  • The forecast was above reported demand in 30% of compared hours.

Forecast Error at a Glance

714 hours from 21 August to 20 September 2026
Average error9.8%
Bias-4.8%
Hours within 5%29%
Worst miss4,278 MW

Average error is the mean absolute percentage gap between the forecast and reported demand. Bias is the signed mean (-343 MW per hour on average): the forecast ran low on average, an under forecast. The worst miss was 4,278 MW (125.2%) too high at 22 Aug 2026, 19:00 MST (UTC-07:00): forecast 7,696 MW, reported 3,418 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, 17:00 MST (UTC-07:00)
AZPS day-ahead demand forecast and reported demand by hour Hourly reported demand and the day-ahead forecast for AZPS over the last 7 days of the window, to 20 Sept 2026, 17:00 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, 18:0014 Sept, 18:0015 Sept, 18:0016 Sept, 18:0017 Sept, 18:0018 Sept, 18:0019 Sept, 18:00
Hourly reported demand and the day-ahead forecast for AZPS over the last 7 days of the window, to 20 Sept 2026, 17:00 MST (UTC-07:00). Gaps are hours with a missing, zero or implausible report.
Data to 2026-09-20
AZPS day-ahead demand forecast and reported demand by hour
Local hourReported demandDay-ahead forecast
13 Sept, 18:007,595 MW7,075 MW
13 Sept, 19:007,363 MW6,451 MW
13 Sept, 20:007,327 MW6,128 MW
13 Sept, 21:006,848 MW5,746 MW
13 Sept, 22:006,652 MW5,285 MW
13 Sept, 23:006,633 MW5,336 MW
14 Sept, 00:006,042 MW5,685 MW
14 Sept, 01:005,798 MW5,395 MW
14 Sept, 02:005,918 MW5,314 MW
14 Sept, 03:005,897 MW5,310 MW
14 Sept, 04:005,841 MW5,429 MW
14 Sept, 05:005,858 MW5,486 MW
14 Sept, 06:005,709 MW5,478 MW
14 Sept, 07:005,474 MW5,527 MW
14 Sept, 08:007,707 MW5,532 MW
14 Sept, 09:005,452 MW5,697 MW
14 Sept, 10:005,777 MW5,934 MW
14 Sept, 11:006,244 MW6,171 MW
14 Sept, 12:006,617 MW6,422 MW
14 Sept, 13:006,802 MW6,792 MW
14 Sept, 14:007,051 MW6,989 MW
14 Sept, 15:007,199 MW7,095 MW
14 Sept, 16:007,341 MW7,199 MW
14 Sept, 17:007,726 MW7,118 MW
14 Sept, 18:007,843 MW7,007 MW
14 Sept, 19:007,609 MW6,793 MW
14 Sept, 20:007,224 MW6,461 MW
14 Sept, 21:006,790 MW6,067 MW
14 Sept, 22:006,429 MW5,637 MW
14 Sept, 23:006,162 MW5,365 MW
15 Sept, 00:005,951 MW5,457 MW
15 Sept, 01:006,018 MW4,975 MW
15 Sept, 02:005,895 MW4,854 MW
15 Sept, 03:005,760 MW4,849 MW
15 Sept, 04:005,764 MW4,995 MW
15 Sept, 05:005,927 MW4,978 MW
15 Sept, 06:005,956 MW5,028 MW
15 Sept, 07:005,791 MW5,085 MW
15 Sept, 08:005,243 MW5,131 MW
15 Sept, 09:005,561 MW5,243 MW
15 Sept, 10:005,667 MW5,359 MW
15 Sept, 11:005,877 MW5,561 MW
15 Sept, 12:006,199 MW5,848 MW
15 Sept, 13:006,573 MW6,168 MW
15 Sept, 14:006,607 MW6,414 MW
15 Sept, 15:006,674 MW6,541 MW
15 Sept, 16:006,777 MW6,622 MW
15 Sept, 17:007,132 MW6,575 MW
15 Sept, 18:007,179 MW6,583 MW
15 Sept, 19:007,304 MW6,398 MW
15 Sept, 20:007,353 MW6,145 MW
15 Sept, 21:006,840 MW5,735 MW
15 Sept, 22:006,482 MW5,348 MW
15 Sept, 23:006,198 MW5,188 MW
16 Sept, 00:005,851 MW5,526 MW
16 Sept, 01:005,913 MW5,412 MW
16 Sept, 02:005,819 MW5,267 MW
16 Sept, 03:005,837 MW5,158 MW
16 Sept, 04:005,772 MW5,278 MW
16 Sept, 05:005,626 MW5,257 MW
16 Sept, 06:005,467 MW5,291 MW
16 Sept, 07:005,389 MW5,338 MW
16 Sept, 08:005,165 MW5,338 MW
16 Sept, 09:005,215 MW5,439 MW
16 Sept, 10:005,530 MW5,545 MW
16 Sept, 11:005,774 MW5,643 MW
16 Sept, 12:005,787 MW5,745 MW
16 Sept, 13:005,609 MW5,866 MW
16 Sept, 14:005,437 MW5,955 MW
16 Sept, 15:005,265 MW5,831 MW
16 Sept, 16:005,106 MW5,864 MW
16 Sept, 17:005,482 MW5,840 MW
16 Sept, 18:005,795 MW5,860 MW
16 Sept, 19:005,733 MW5,703 MW
16 Sept, 20:005,607 MW5,511 MW
16 Sept, 21:005,696 MW5,251 MW
16 Sept, 22:005,400 MW4,917 MW
16 Sept, 23:005,070 MW4,670 MW
17 Sept, 00:004,805 MW4,413 MW
17 Sept, 01:005,086 MW4,271 MW
17 Sept, 02:004,980 MW4,224 MW
17 Sept, 03:004,936 MW4,229 MW
17 Sept, 04:004,901 MW4,403 MW
17 Sept, 05:004,939 MW4,541 MW
17 Sept, 06:005,283 MW4,592 MW
17 Sept, 07:005,331 MW4,592 MW
17 Sept, 08:005,892 MW4,631 MW
17 Sept, 09:006,624 MW4,747 MW
17 Sept, 10:006,870 MW4,913 MW
17 Sept, 11:006,695 MW5,122 MW
17 Sept, 12:007,139 MW5,349 MW
17 Sept, 13:007,041 MW5,652 MW
17 Sept, 14:006,778 MW5,980 MW
17 Sept, 15:006,290 MW6,050 MW
17 Sept, 16:006,004 MW6,201 MW
17 Sept, 17:006,137 MW6,231 MW
17 Sept, 18:00n/a6,217 MW
17 Sept, 19:006,381 MW6,013 MW
17 Sept, 20:006,367 MW5,732 MW
17 Sept, 21:005,934 MW5,402 MW
17 Sept, 22:005,676 MW5,015 MW
17 Sept, 23:005,478 MW4,793 MW
18 Sept, 00:005,425 MW4,760 MW
18 Sept, 01:005,304 MW4,603 MW
18 Sept, 02:005,222 MW4,477 MW
18 Sept, 03:005,132 MW4,497 MW
18 Sept, 04:005,113 MW4,619 MW
18 Sept, 05:005,094 MW4,684 MW
18 Sept, 06:005,078 MW4,729 MW
18 Sept, 07:004,717 MW4,745 MW
18 Sept, 08:004,250 MW4,783 MW
18 Sept, 09:004,378 MW5,000 MW
18 Sept, 10:004,446 MW5,237 MW
18 Sept, 11:004,769 MW5,472 MW
18 Sept, 12:005,286 MW5,812 MW
18 Sept, 13:005,472 MW6,183 MW
18 Sept, 14:005,581 MW6,499 MW
18 Sept, 15:005,767 MW6,601 MW
18 Sept, 16:005,991 MW6,741 MW
18 Sept, 17:006,463 MW6,640 MW
18 Sept, 18:006,805 MW6,541 MW
18 Sept, 19:006,960 MW6,171 MW
18 Sept, 20:006,699 MW5,729 MW
18 Sept, 21:006,351 MW5,444 MW
18 Sept, 22:006,010 MW5,079 MW
18 Sept, 23:005,560 MW4,642 MW
19 Sept, 00:005,156 MW4,658 MW
19 Sept, 01:005,030 MW4,550 MW
19 Sept, 02:004,933 MW4,431 MW
19 Sept, 03:005,002 MW4,272 MW
19 Sept, 04:004,912 MW4,196 MW
19 Sept, 05:004,886 MW4,254 MW
19 Sept, 06:004,857 MW4,366 MW
19 Sept, 07:004,122 MW4,438 MW
19 Sept, 08:003,616 MW4,524 MW
19 Sept, 09:003,831 MW4,826 MW
19 Sept, 10:004,184 MW5,167 MW
19 Sept, 11:004,534 MW5,521 MW
19 Sept, 12:004,785 MW5,860 MW
19 Sept, 13:005,137 MW6,220 MW
19 Sept, 14:005,518 MW6,529 MW
19 Sept, 15:006,041 MW6,836 MW
19 Sept, 16:006,430 MW6,910 MW
19 Sept, 17:007,006 MW6,881 MW
19 Sept, 18:007,218 MW6,400 MW
19 Sept, 19:007,045 MW6,032 MW
19 Sept, 20:006,370 MW5,679 MW
19 Sept, 21:005,952 MW5,278 MW
19 Sept, 22:005,593 MW4,930 MW
19 Sept, 23:005,272 MW4,600 MW
20 Sept, 00:004,982 MW4,519 MW
20 Sept, 01:004,965 MW4,332 MW
20 Sept, 02:004,882 MW4,203 MW
20 Sept, 03:004,902 MW4,080 MW
20 Sept, 04:004,898 MW4,048 MW
20 Sept, 05:004,914 MW3,920 MW
20 Sept, 06:005,270 MW3,915 MW
20 Sept, 07:005,756 MW3,988 MW
20 Sept, 08:006,524 MW4,064 MW
20 Sept, 09:006,846 MW4,351 MW
20 Sept, 10:006,900 MW4,726 MW
20 Sept, 11:007,019 MW5,148 MW
20 Sept, 12:006,606 MW5,574 MW
20 Sept, 13:006,269 MW5,933 MW
20 Sept, 14:006,439 MW6,264 MW
20 Sept, 15:006,490 MW6,544 MW
20 Sept, 16:006,825 MW6,692 MW
20 Sept, 17:007,024 MW6,627 MW

Assumptions

  • Only hours with both a forecast and a positive demand reading count (714 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.