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

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

The day-ahead demand forecast for CAISO was off by 8.6% on average (mean absolute percentage error) over 719 hours from 21 August to 20 September 2026, and 54% of hours landed within 5% of the reading. Its bias was -8.0%: it ran low on average, an under forecast. The largest miss was 11,666 MW (29.8%) too low at 8 Sept 2026, 10:00 PDT (UTC-07:00). Dates and times are local (America/Los_Angeles).

Key Facts

  • The day-ahead demand forecast for CAISO was off by 8.6% on average (mean absolute percentage error) over 719 hours from 21 August to 20 September 2026, and 54% of hours landed within 5% of the reading. Its bias was -8.0%: it ran low on average, an under forecast. The largest miss was 11,666 MW (29.8%) too low at 8 Sept 2026, 10:00 PDT (UTC-07:00).
  • Across 53 US grids ranked by average error over their own latest 30 day windows, CAISO came 42 (1 is the smallest error).
  • On average the forecast differed from reported demand by 2,870 MW, against average demand of 32,203 MW.
  • The forecast was above reported demand in 14% of compared hours.

Forecast Error at a Glance

719 hours from 21 August to 20 September 2026
Average error8.6%
Bias-8.0%
Hours within 5%54%
Worst miss11,666 MW

Average error is the mean absolute percentage gap between the forecast and reported demand. Bias is the signed mean (-2,647 MW per hour on average): the forecast ran low on average, an under forecast. The worst miss was 11,666 MW (29.8%) too low at 8 Sept 2026, 10:00 PDT (UTC-07:00): forecast 27,536 MW, reported 39,202 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)
CAISO day-ahead demand forecast and reported demand by hour Hourly reported demand and the day-ahead forecast for CAISO 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 10,000 20,000 30,000 40,000 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 CAISO 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
CAISO day-ahead demand forecast and reported demand by hour
Local hourReported demandDay-ahead forecast
13 Sept, 19:0032,914 MW33,051 MW
13 Sept, 20:0032,280 MW32,350 MW
13 Sept, 21:0031,183 MW31,225 MW
13 Sept, 22:0029,176 MW29,567 MW
13 Sept, 23:0027,869 MW27,447 MW
14 Sept, 00:0026,046 MW25,917 MW
14 Sept, 01:0025,114 MW24,612 MW
14 Sept, 02:0024,321 MW23,613 MW
14 Sept, 03:0024,042 MW23,022 MW
14 Sept, 04:0024,029 MW23,264 MW
14 Sept, 05:0024,900 MW24,241 MW
14 Sept, 06:0026,521 MW26,011 MW
14 Sept, 07:0028,202 MW26,997 MW
14 Sept, 08:0032,162 MW26,737 MW
14 Sept, 09:0033,676 MW25,864 MW
14 Sept, 10:0033,184 MW25,263 MW
14 Sept, 11:0033,560 MW25,206 MW
14 Sept, 12:0033,491 MW25,732 MW
14 Sept, 13:0032,186 MW26,999 MW
14 Sept, 14:0032,635 MW29,275 MW
14 Sept, 15:0033,276 MW31,568 MW
14 Sept, 16:0034,353 MW33,581 MW
14 Sept, 17:0034,826 MW35,206 MW
14 Sept, 18:0034,849 MW35,919 MW
14 Sept, 19:0033,908 MW35,449 MW
14 Sept, 20:0033,027 MW34,241 MW
14 Sept, 21:0031,951 MW32,899 MW
14 Sept, 22:0029,769 MW30,727 MW
14 Sept, 23:0027,820 MW28,345 MW
15 Sept, 00:0026,769 MW26,397 MW
15 Sept, 01:0025,244 MW25,108 MW
15 Sept, 02:0024,393 MW23,954 MW
15 Sept, 03:0023,965 MW23,310 MW
15 Sept, 04:0023,645 MW23,343 MW
15 Sept, 05:0024,575 MW24,276 MW
15 Sept, 06:0026,310 MW25,842 MW
15 Sept, 07:0027,835 MW26,784 MW
15 Sept, 08:0031,470 MW26,448 MW
15 Sept, 09:0033,821 MW25,415 MW
15 Sept, 10:0033,575 MW24,634 MW
15 Sept, 11:0033,109 MW24,209 MW
15 Sept, 12:0033,038 MW24,608 MW
15 Sept, 13:0032,815 MW25,774 MW
15 Sept, 14:0032,252 MW27,528 MW
15 Sept, 15:0032,661 MW29,736 MW
15 Sept, 16:0033,434 MW31,824 MW
15 Sept, 17:0033,870 MW33,693 MW
15 Sept, 18:0033,774 MW34,181 MW
15 Sept, 19:0033,103 MW33,882 MW
15 Sept, 20:0032,637 MW33,111 MW
15 Sept, 21:0031,908 MW31,932 MW
15 Sept, 22:0029,442 MW29,813 MW
15 Sept, 23:0027,142 MW27,639 MW
16 Sept, 00:0026,079 MW25,868 MW
16 Sept, 01:0025,210 MW24,675 MW
16 Sept, 02:0024,364 MW23,543 MW
16 Sept, 03:0024,098 MW22,978 MW
16 Sept, 04:0023,873 MW22,992 MW
16 Sept, 05:0024,775 MW23,898 MW
16 Sept, 06:0026,676 MW25,494 MW
16 Sept, 07:0027,990 MW26,464 MW
16 Sept, 08:0030,756 MW26,140 MW
16 Sept, 09:0032,155 MW25,099 MW
16 Sept, 10:0032,529 MW24,061 MW
16 Sept, 11:0032,192 MW23,294 MW
16 Sept, 12:0031,347 MW23,204 MW
16 Sept, 13:0031,130 MW24,132 MW
16 Sept, 14:0030,612 MW25,598 MW
16 Sept, 15:0030,134 MW27,554 MW
16 Sept, 16:0030,863 MW29,357 MW
16 Sept, 17:0031,167 MW31,064 MW
16 Sept, 18:0031,438 MW31,715 MW
16 Sept, 19:0031,306 MW31,672 MW
16 Sept, 20:0030,965 MW30,960 MW
16 Sept, 21:0030,313 MW29,992 MW
16 Sept, 22:0028,706 MW28,294 MW
16 Sept, 23:0026,701 MW26,316 MW
17 Sept, 00:0025,864 MW25,471 MW
17 Sept, 01:0024,792 MW24,278 MW
17 Sept, 02:0024,344 MW23,400 MW
17 Sept, 03:0023,640 MW22,862 MW
17 Sept, 04:0023,652 MW22,979 MW
17 Sept, 05:0024,779 MW24,001 MW
17 Sept, 06:0026,537 MW25,684 MW
17 Sept, 07:0027,844 MW26,646 MW
17 Sept, 08:0030,044 MW26,387 MW
17 Sept, 09:0031,901 MW25,443 MW
17 Sept, 10:0032,115 MW24,143 MW
17 Sept, 11:0033,379 MW23,237 MW
17 Sept, 12:0033,319 MW22,988 MW
17 Sept, 13:0032,662 MW23,534 MW
17 Sept, 14:0032,196 MW24,719 MW
17 Sept, 15:0032,141 MW26,708 MW
17 Sept, 16:0031,735 MW28,516 MW
17 Sept, 17:0031,017 MW30,453 MW
17 Sept, 18:0031,083 MW31,215 MW
17 Sept, 19:0030,996 MW31,231 MW
17 Sept, 20:0030,627 MW30,633 MW
17 Sept, 21:0029,852 MW29,743 MW
17 Sept, 22:0028,285 MW28,085 MW
17 Sept, 23:0026,533 MW26,221 MW
18 Sept, 00:0025,512 MW24,958 MW
18 Sept, 01:0024,509 MW23,804 MW
18 Sept, 02:0023,784 MW22,796 MW
18 Sept, 03:0023,459 MW22,332 MW
18 Sept, 04:0023,101 MW22,448 MW
18 Sept, 05:0024,121 MW23,375 MW
18 Sept, 06:0025,440 MW24,828 MW
18 Sept, 07:0027,412 MW25,675 MW
18 Sept, 08:0030,434 MW25,235 MW
18 Sept, 09:0032,190 MW24,116 MW
18 Sept, 10:0031,206 MW22,972 MW
18 Sept, 11:0030,509 MW22,198 MW
18 Sept, 12:0030,048 MW22,074 MW
18 Sept, 13:0029,237 MW22,927 MW
18 Sept, 14:0029,040 MW24,441 MW
18 Sept, 15:0030,014 MW26,595 MW
18 Sept, 16:0030,833 MW28,661 MW
18 Sept, 17:0031,139 MW31,024 MW
18 Sept, 18:0031,276 MW31,663 MW
18 Sept, 19:0030,696 MW31,368 MW
18 Sept, 20:0030,252 MW30,637 MW
18 Sept, 21:0029,789 MW29,791 MW
18 Sept, 22:0028,202 MW28,189 MW
18 Sept, 23:0026,479 MW26,355 MW
19 Sept, 00:0025,352 MW25,359 MW
19 Sept, 01:0024,046 MW24,075 MW
19 Sept, 02:0023,144 MW22,939 MW
19 Sept, 03:0022,469 MW22,188 MW
19 Sept, 04:0022,198 MW21,880 MW
19 Sept, 05:0022,404 MW22,131 MW
19 Sept, 06:0023,065 MW22,619 MW
19 Sept, 07:0023,912 MW22,709 MW
19 Sept, 08:0027,003 MW22,305 MW
19 Sept, 09:0028,315 MW21,396 MW
19 Sept, 10:0028,178 MW20,450 MW
19 Sept, 11:0027,913 MW19,855 MW
19 Sept, 12:0027,679 MW20,136 MW
19 Sept, 13:0027,551 MW21,201 MW
19 Sept, 14:0026,665 MW23,230 MW
19 Sept, 15:0028,128 MW25,920 MW
19 Sept, 16:0029,674 MW28,473 MW
19 Sept, 17:0030,695 MW30,780 MW
19 Sept, 18:0030,738 MW31,693 MW
19 Sept, 19:0030,163 MW31,499 MW
19 Sept, 20:0029,455 MW30,656 MW
19 Sept, 21:0028,639 MW29,656 MW
19 Sept, 22:0027,223 MW28,112 MW
19 Sept, 23:0025,605 MW26,426 MW
20 Sept, 00:0024,813 MW24,705 MW
20 Sept, 01:0023,563 MW23,454 MW
20 Sept, 02:0022,649 MW22,333 MW
20 Sept, 03:0022,038 MW21,596 MW
20 Sept, 04:0021,560 MW21,226 MW
20 Sept, 05:0021,517 MW21,236 MW
20 Sept, 06:0022,093 MW21,602 MW
20 Sept, 07:0023,188 MW21,604 MW
20 Sept, 08:0026,639 MW21,580 MW
20 Sept, 09:0029,386 MW21,140 MW
20 Sept, 10:0029,490 MW20,729 MW
20 Sept, 11:0029,380 MW20,564 MW
20 Sept, 12:0028,118 MW20,944 MW
20 Sept, 13:0027,998 MW22,107 MW
20 Sept, 14:0028,337 MW23,867 MW
20 Sept, 15:0028,070 MW26,004 MW
20 Sept, 16:0028,322 MW28,039 MW
20 Sept, 17:0028,745 MW30,027 MW
20 Sept, 18:0028,795 MW30,447 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.