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

Portugal Demand Forecast Accuracy: Error, Bias and Worst Miss, 23 August to 20 September 2026

The day-ahead demand forecast for Portugal was off by 1.5% on average (mean absolute percentage error) over 686 hours from 23 August to 20 September 2026, and 98% of hours landed within 5% of the reading. Its bias was -0.2%: it ran close to balanced on average. The largest miss was 521 MW (7.1%) too low at 8 Sept 2026, 16:00 WEST (UTC+01:00). Dates and times are local (Europe/Lisbon).

Key Facts

  • The day-ahead demand forecast for Portugal was off by 1.5% on average (mean absolute percentage error) over 686 hours from 23 August to 20 September 2026, and 98% of hours landed within 5% of the reading. Its bias was -0.2%: it ran close to balanced on average. The largest miss was 521 MW (7.1%) too low at 8 Sept 2026, 16:00 WEST (UTC+01:00).
  • Across 47 European bidding zones ranked by average error over their own latest 30 day windows, Portugal came 4 (1 is the smallest error).
  • On average the forecast differed from reported demand by 91 MW, against average demand of 5,908 MW.
  • The forecast was above reported demand in 41% of compared hours.

Forecast Error at a Glance

686 hours from 23 August to 20 September 2026
Average error1.5%
Bias-0.2%
Hours within 5%98%
Worst miss521 MW

Average error is the mean absolute percentage gap between the forecast and reported demand. Bias is the signed mean (-17 MW per hour on average): the forecast ran close to balanced on average. The worst miss was 521 MW (7.1%) too low at 8 Sept 2026, 16:00 WEST (UTC+01:00): forecast 6,853 MW, reported 7,374 MW.

Source: ENTSO-E Transparency Platform (transparency.entsoe.eu), CC BY 4.0. Aggregated and converted by World Power Monitor; ENTSO-E does not endorse this site. (ENTSO-E Terms of Use plus CC BY 4.0 for listed data items) 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, 13:00 WEST (UTC+01:00)
Portugal day-ahead demand forecast and reported demand by hour Hourly reported demand and the day-ahead forecast for Portugal over the last 7 days of the window, to 20 Sept 2026, 13:00 WEST (UTC+01:00). Gaps are hours with a missing, zero or implausible report. 0 2,500 5,000 7,500 10,000 13 Sept, 14:0014 Sept, 14:0015 Sept, 14:0016 Sept, 14:0017 Sept, 14:0018 Sept, 14:0019 Sept, 14:00
Hourly reported demand and the day-ahead forecast for Portugal over the last 7 days of the window, to 20 Sept 2026, 13:00 WEST (UTC+01:00). Gaps are hours with a missing, zero or implausible report.
Data to 2026-09-20
Portugal day-ahead demand forecast and reported demand by hour
Local hourReported demandDay-ahead forecast
13 Sept, 14:005,229 MW5,231 MW
13 Sept, 15:005,263 MW5,222 MW
13 Sept, 16:005,433 MW5,351 MW
13 Sept, 17:005,787 MW5,681 MW
13 Sept, 18:006,248 MW6,078 MW
13 Sept, 19:006,700 MW6,473 MW
13 Sept, 20:007,004 MW6,874 MW
13 Sept, 21:006,726 MW6,538 MW
13 Sept, 22:006,329 MW6,137 MW
13 Sept, 23:005,848 MW5,712 MW
14 Sept, 00:005,431 MW5,498 MW
14 Sept, 01:005,146 MW5,200 MW
14 Sept, 02:004,942 MW4,987 MW
14 Sept, 03:004,838 MW4,838 MW
14 Sept, 04:004,787 MW4,791 MW
14 Sept, 05:004,881 MW4,897 MW
14 Sept, 06:005,365 MW5,313 MW
14 Sept, 07:005,983 MW5,807 MW
14 Sept, 08:006,720 MW6,562 MW
14 Sept, 09:006,965 MW6,841 MW
14 Sept, 10:006,909 MW6,877 MW
14 Sept, 11:006,935 MW6,893 MW
14 Sept, 12:006,865 MW6,838 MW
14 Sept, 13:006,798 MW6,819 MW
14 Sept, 14:007,029 MW7,028 MW
14 Sept, 15:007,114 MW7,083 MW
14 Sept, 16:007,288 MW7,181 MW
14 Sept, 17:007,270 MW7,280 MW
14 Sept, 18:007,498 MW7,463 MW
14 Sept, 19:007,935 MW7,761 MW
14 Sept, 20:008,082 MW7,934 MW
14 Sept, 21:007,579 MW7,467 MW
14 Sept, 22:006,969 MW6,905 MW
14 Sept, 23:006,377 MW6,295 MW
15 Sept, 00:005,915 MW5,842 MW
15 Sept, 01:005,574 MW5,551 MW
15 Sept, 02:005,328 MW5,349 MW
15 Sept, 03:005,200 MW5,215 MW
15 Sept, 04:005,113 MW5,176 MW
15 Sept, 05:005,197 MW5,251 MW
15 Sept, 06:005,619 MW5,603 MW
15 Sept, 07:006,201 MW6,056 MW
15 Sept, 08:007,045 MW6,843 MW
15 Sept, 09:007,301 MW7,097 MW
15 Sept, 10:007,148 MW7,078 MW
15 Sept, 11:006,877 MW7,051 MW
15 Sept, 12:006,638 MW6,852 MW
15 Sept, 13:006,493 MW6,692 MW
15 Sept, 14:006,667 MW6,812 MW
15 Sept, 15:006,744 MW6,857 MW
15 Sept, 16:006,944 MW6,988 MW
15 Sept, 17:007,161 MW7,078 MW
15 Sept, 18:007,324 MW7,294 MW
15 Sept, 19:007,770 MW7,631 MW
15 Sept, 20:007,925 MW7,774 MW
15 Sept, 21:007,510 MW7,331 MW
15 Sept, 22:006,960 MW6,794 MW
15 Sept, 23:006,439 MW6,253 MW
16 Sept, 00:006,006 MW5,864 MW
16 Sept, 01:005,673 MW5,572 MW
16 Sept, 02:005,439 MW5,369 MW
16 Sept, 03:005,320 MW5,243 MW
16 Sept, 04:005,176 MW5,196 MW
16 Sept, 05:005,349 MW5,275 MW
16 Sept, 06:005,776 MW5,643 MW
16 Sept, 07:006,297 MW6,091 MW
16 Sept, 08:006,855 MW6,773 MW
16 Sept, 09:007,000 MW6,818 MW
16 Sept, 10:006,711 MW6,672 MW
16 Sept, 11:006,661 MW6,561 MW
16 Sept, 12:006,436 MW6,417 MW
16 Sept, 13:006,315 MW6,325 MW
16 Sept, 14:006,488 MW6,481 MW
16 Sept, 15:006,581 MW6,531 MW
16 Sept, 16:006,723 MW6,680 MW
16 Sept, 17:006,871 MW6,805 MW
16 Sept, 18:007,109 MW7,057 MW
16 Sept, 19:007,610 MW7,493 MW
16 Sept, 20:007,733 MW7,698 MW
16 Sept, 21:007,248 MW7,254 MW
16 Sept, 22:006,749 MW6,759 MW
16 Sept, 23:006,232 MW6,188 MW
17 Sept, 00:005,871 MW5,744 MW
17 Sept, 01:005,565 MW5,458 MW
17 Sept, 02:005,352 MW5,248 MW
17 Sept, 03:005,253 MW5,141 MW
17 Sept, 04:005,185 MW5,096 MW
17 Sept, 05:005,249 MW5,175 MW
17 Sept, 06:005,673 MW5,549 MW
17 Sept, 07:006,229 MW6,013 MW
17 Sept, 08:006,781 MW6,635 MW
17 Sept, 09:006,910 MW6,733 MW
17 Sept, 10:006,692 MW6,540 MW
17 Sept, 11:006,553 MW6,462 MW
17 Sept, 12:006,441 MW6,296 MW
17 Sept, 13:006,361 MW6,201 MW
17 Sept, 14:006,471 MW6,351 MW
17 Sept, 15:006,497 MW6,456 MW
17 Sept, 16:006,584 MW6,597 MW
17 Sept, 17:006,657 MW6,725 MW
17 Sept, 18:006,976 MW7,017 MW
17 Sept, 19:007,500 MW7,438 MW
17 Sept, 20:007,670 MW7,632 MW
17 Sept, 21:007,179 MW7,163 MW
17 Sept, 22:006,622 MW6,671 MW
17 Sept, 23:006,144 MW6,100 MW
18 Sept, 00:005,755 MW5,682 MW
18 Sept, 01:005,498 MW5,413 MW
18 Sept, 02:005,273 MW5,206 MW
18 Sept, 03:005,161 MW5,113 MW
18 Sept, 04:005,132 MW5,049 MW
18 Sept, 05:005,215 MW5,132 MW
18 Sept, 06:005,667 MW5,519 MW
18 Sept, 07:006,190 MW6,036 MW
18 Sept, 08:006,695 MW6,620 MW
18 Sept, 09:006,684 MW6,700 MW
18 Sept, 10:006,497 MW6,521 MW
18 Sept, 11:006,432 MW6,450 MW
18 Sept, 12:006,228 MW6,292 MW
18 Sept, 13:006,084 MW6,210 MW
18 Sept, 14:006,231 MW6,312 MW
18 Sept, 15:006,369 MW6,381 MW
18 Sept, 16:006,488 MW6,548 MW
18 Sept, 17:006,700 MW6,707 MW
18 Sept, 18:007,003 MW6,911 MW
18 Sept, 19:007,396 MW7,285 MW
18 Sept, 20:007,554 MW7,444 MW
18 Sept, 21:007,125 MW7,000 MW
18 Sept, 22:006,666 MW6,524 MW
18 Sept, 23:006,164 MW6,002 MW
19 Sept, 00:005,712 MW5,537 MW
19 Sept, 01:005,464 MW5,274 MW
19 Sept, 02:005,233 MW5,057 MW
19 Sept, 03:005,060 MW4,921 MW
19 Sept, 04:004,949 MW4,868 MW
19 Sept, 05:004,860 MW4,876 MW
19 Sept, 06:005,083 MW5,011 MW
19 Sept, 07:005,166 MW5,156 MW
19 Sept, 08:005,339 MW5,362 MW
19 Sept, 09:005,433 MW5,558 MW
19 Sept, 10:005,384 MW5,533 MW
19 Sept, 11:005,415 MW5,466 MW
19 Sept, 12:005,544 MW5,510 MW
19 Sept, 13:005,369 MW5,360 MW
19 Sept, 14:005,433 MW5,272 MW
19 Sept, 15:005,422 MW5,325 MW
19 Sept, 16:005,566 MW5,471 MW
19 Sept, 17:005,862 MW5,779 MW
19 Sept, 18:006,304 MW6,164 MW
19 Sept, 19:006,667 MW6,595 MW
19 Sept, 20:006,737 MW6,833 MW
19 Sept, 21:006,383 MW6,432 MW
19 Sept, 22:006,027 MW6,035 MW
19 Sept, 23:005,642 MW5,634 MW
20 Sept, 00:005,293 MW5,281 MW
20 Sept, 01:005,011 MW4,993 MW
20 Sept, 02:004,845 MW4,754 MW
20 Sept, 03:004,715 MW4,628 MW
20 Sept, 04:004,579 MW4,573 MW
20 Sept, 05:004,577 MW4,572 MW
20 Sept, 06:004,631 MW4,671 MW
20 Sept, 07:004,602 MW4,739 MW
20 Sept, 08:004,890 MW4,912 MW
20 Sept, 09:005,181 MW5,098 MW
20 Sept, 10:005,462 MW5,186 MW
20 Sept, 11:005,630 MW5,236 MW
20 Sept, 12:005,749 MW5,313 MW
20 Sept, 13:005,579 MW5,180 MW

Assumptions

  • Only hours with both a forecast and a positive demand reading count (686 of 686 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.
  • European figures are for the ENTSO-E bidding zone named on this page. US and European grids are ranked separately.