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

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

The day-ahead demand forecast for Greece was off by 4.0% on average (mean absolute percentage error) over 687 hours from 23 August to 20 September 2026, and 67% of hours landed within 5% of the reading. Its bias was +2.6%: it ran high on average, an over forecast. The largest miss was 1,143 MW (17.0%) too high at 29 Aug 2026, 12:00 EEST (UTC+03:00). Dates and times are local (Europe/Athens).

Key Facts

  • The day-ahead demand forecast for Greece was off by 4.0% on average (mean absolute percentage error) over 687 hours from 23 August to 20 September 2026, and 67% of hours landed within 5% of the reading. Its bias was +2.6%: it ran high on average, an over forecast. The largest miss was 1,143 MW (17.0%) too high at 29 Aug 2026, 12:00 EEST (UTC+03:00).
  • Across 47 European bidding zones ranked by average error over their own latest 30 day windows, Greece came 27 (1 is the smallest error).
  • On average the forecast differed from reported demand by 264 MW, against average demand of 6,434 MW.
  • The forecast was above reported demand in 71% of compared hours.

Forecast Error at a Glance

687 hours from 23 August to 20 September 2026
Average error4.0%
Bias+2.6%
Hours within 5%67%
Worst miss1,143 MW

Average error is the mean absolute percentage gap between the forecast and reported demand. Bias is the signed mean (+173 MW per hour on average): the forecast ran high on average, an over forecast. The worst miss was 1,143 MW (17.0%) too high at 29 Aug 2026, 12:00 EEST (UTC+03:00): forecast 7,848 MW, reported 6,705 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, 14:00 EEST (UTC+03:00)
Greece day-ahead demand forecast and reported demand by hour Hourly reported demand and the day-ahead forecast for Greece over the last 7 days of the window, to 20 Sept 2026, 14:00 EEST (UTC+03:00). Gaps are hours with a missing, zero or implausible report. 0 2,000 4,000 6,000 8,000 13 Sept, 15:0014 Sept, 15:0015 Sept, 15:0016 Sept, 15:0017 Sept, 15:0018 Sept, 15:0019 Sept, 15:00
Hourly reported demand and the day-ahead forecast for Greece over the last 7 days of the window, to 20 Sept 2026, 14:00 EEST (UTC+03:00). Gaps are hours with a missing, zero or implausible report.
Data to 2026-09-20
Greece day-ahead demand forecast and reported demand by hour
Local hourReported demandDay-ahead forecast
13 Sept, 15:005,545 MW5,863 MW
13 Sept, 16:005,452 MW5,950 MW
13 Sept, 17:005,436 MW6,023 MW
13 Sept, 18:005,597 MW6,028 MW
13 Sept, 19:005,767 MW6,005 MW
13 Sept, 20:006,065 MW6,170 MW
13 Sept, 21:005,984 MW6,010 MW
13 Sept, 22:005,724 MW5,683 MW
13 Sept, 23:005,380 MW5,353 MW
14 Sept, 00:004,949 MW4,928 MW
14 Sept, 01:004,646 MW4,658 MW
14 Sept, 02:004,500 MW4,490 MW
14 Sept, 03:004,332 MW4,390 MW
14 Sept, 04:004,281 MW4,340 MW
14 Sept, 05:004,364 MW4,420 MW
14 Sept, 06:004,737 MW4,790 MW
14 Sept, 07:005,208 MW5,043 MW
14 Sept, 08:005,583 MW5,503 MW
14 Sept, 09:006,013 MW5,950 MW
14 Sept, 10:006,398 MW6,370 MW
14 Sept, 11:006,637 MW6,595 MW
14 Sept, 12:006,898 MW6,873 MW
14 Sept, 13:007,032 MW7,003 MW
14 Sept, 14:006,888 MW6,943 MW
14 Sept, 15:006,639 MW6,775 MW
14 Sept, 16:006,479 MW6,578 MW
14 Sept, 17:006,426 MW6,528 MW
14 Sept, 18:006,420 MW6,460 MW
14 Sept, 19:006,446 MW6,535 MW
14 Sept, 20:006,656 MW6,793 MW
14 Sept, 21:006,320 MW6,430 MW
14 Sept, 22:005,828 MW5,880 MW
14 Sept, 23:005,470 MW5,448 MW
15 Sept, 00:005,120 MW5,038 MW
15 Sept, 01:004,877 MW4,763 MW
15 Sept, 02:004,708 MW4,603 MW
15 Sept, 03:004,652 MW4,493 MW
15 Sept, 04:004,574 MW4,440 MW
15 Sept, 05:004,639 MW4,493 MW
15 Sept, 06:004,875 MW4,880 MW
15 Sept, 07:005,364 MW5,273 MW
15 Sept, 08:006,020 MW5,650 MW
15 Sept, 09:006,967 MW6,105 MW
15 Sept, 10:006,980 MW6,360 MW
15 Sept, 11:006,726 MW6,540 MW
15 Sept, 12:006,775 MW6,690 MW
15 Sept, 13:007,017 MW6,700 MW
15 Sept, 14:007,121 MW6,580 MW
15 Sept, 15:006,843 MW6,380 MW
15 Sept, 16:006,553 MW6,200 MW
15 Sept, 17:006,267 MW6,200 MW
15 Sept, 18:006,096 MW6,200 MW
15 Sept, 19:006,151 MW6,410 MW
15 Sept, 20:006,311 MW6,650 MW
15 Sept, 21:005,900 MW6,270 MW
15 Sept, 22:005,385 MW5,750 MW
15 Sept, 23:005,085 MW5,300 MW
16 Sept, 00:004,746 MW4,929 MW
16 Sept, 01:004,550 MW4,690 MW
16 Sept, 02:004,432 MW4,558 MW
16 Sept, 03:004,347 MW4,440 MW
16 Sept, 04:004,319 MW4,415 MW
16 Sept, 05:004,456 MW4,500 MW
16 Sept, 06:004,783 MW4,860 MW
16 Sept, 07:005,246 MW5,293 MW
16 Sept, 08:005,732 MW5,788 MW
16 Sept, 09:006,098 MW6,258 MW
16 Sept, 10:006,320 MW6,555 MW
16 Sept, 11:006,514 MW6,685 MW
16 Sept, 12:006,804 MW6,773 MW
16 Sept, 13:006,842 MW6,788 MW
16 Sept, 14:006,601 MW6,645 MW
16 Sept, 15:006,282 MW6,380 MW
16 Sept, 16:006,066 MW6,195 MW
16 Sept, 17:005,903 MW6,110 MW
16 Sept, 18:005,898 MW6,088 MW
16 Sept, 19:006,087 MW6,245 MW
16 Sept, 20:006,305 MW6,450 MW
16 Sept, 21:005,928 MW6,080 MW
16 Sept, 22:005,412 MW5,580 MW
16 Sept, 23:005,111 MW5,213 MW
17 Sept, 00:004,749 MW4,830 MW
17 Sept, 01:004,506 MW4,573 MW
17 Sept, 02:004,368 MW4,460 MW
17 Sept, 03:004,288 MW4,370 MW
17 Sept, 04:004,302 MW4,340 MW
17 Sept, 05:004,380 MW4,470 MW
17 Sept, 06:004,746 MW4,798 MW
17 Sept, 07:005,140 MW5,228 MW
17 Sept, 08:005,462 MW5,758 MW
17 Sept, 09:005,878 MW6,190 MW
17 Sept, 10:006,348 MW6,453 MW
17 Sept, 11:007,024 MW6,665 MW
17 Sept, 12:007,316 MW6,778 MW
17 Sept, 13:007,302 MW6,740 MW
17 Sept, 14:007,115 MW6,528 MW
17 Sept, 15:006,755 MW6,243 MW
17 Sept, 16:006,207 MW6,025 MW
17 Sept, 17:006,068 MW5,970 MW
17 Sept, 18:006,192 MW5,993 MW
17 Sept, 19:006,355 MW6,128 MW
17 Sept, 20:006,534 MW6,320 MW
17 Sept, 21:006,114 MW5,920 MW
17 Sept, 22:005,616 MW5,430 MW
17 Sept, 23:005,282 MW5,070 MW
18 Sept, 00:004,892 MW4,753 MW
18 Sept, 01:004,666 MW4,530 MW
18 Sept, 02:004,500 MW4,410 MW
18 Sept, 03:004,444 MW4,328 MW
18 Sept, 04:004,412 MW4,320 MW
18 Sept, 05:004,548 MW4,450 MW
18 Sept, 06:004,888 MW4,770 MW
18 Sept, 07:005,276 MW5,190 MW
18 Sept, 08:005,613 MW5,688 MW
18 Sept, 09:005,930 MW6,138 MW
18 Sept, 10:006,273 MW6,388 MW
18 Sept, 11:006,520 MW6,565 MW
18 Sept, 12:006,735 MW6,640 MW
18 Sept, 13:006,842 MW6,698 MW
18 Sept, 14:006,707 MW6,508 MW
18 Sept, 15:006,404 MW6,230 MW
18 Sept, 16:006,209 MW6,043 MW
18 Sept, 17:006,185 MW5,985 MW
18 Sept, 18:006,320 MW6,098 MW
18 Sept, 19:006,418 MW6,335 MW
18 Sept, 20:006,528 MW6,500 MW
18 Sept, 21:006,089 MW6,070 MW
18 Sept, 22:005,613 MW5,595 MW
18 Sept, 23:005,246 MW5,270 MW
19 Sept, 00:004,904 MW4,880 MW
19 Sept, 01:004,658 MW4,628 MW
19 Sept, 02:004,523 MW4,470 MW
19 Sept, 03:004,406 MW4,370 MW
19 Sept, 04:004,369 MW4,330 MW
19 Sept, 05:004,374 MW4,328 MW
19 Sept, 06:004,550 MW4,490 MW
19 Sept, 07:004,642 MW4,653 MW
19 Sept, 08:004,899 MW5,078 MW
19 Sept, 09:005,327 MW5,533 MW
19 Sept, 10:005,822 MW5,843 MW
19 Sept, 11:006,290 MW6,080 MW
19 Sept, 12:006,664 MW6,265 MW
19 Sept, 13:006,581 MW6,193 MW
19 Sept, 14:006,447 MW6,023 MW
19 Sept, 15:005,982 MW5,783 MW
19 Sept, 16:005,728 MW5,625 MW
19 Sept, 17:005,839 MW5,643 MW
19 Sept, 18:005,928 MW5,690 MW
19 Sept, 19:006,002 MW5,910 MW
19 Sept, 20:006,042 MW6,033 MW
19 Sept, 21:005,670 MW5,670 MW
19 Sept, 22:005,310 MW5,310 MW
19 Sept, 23:004,984 MW5,010 MW
20 Sept, 00:004,735 MW4,708 MW
20 Sept, 01:004,619 MW4,465 MW
20 Sept, 02:004,454 MW4,300 MW
20 Sept, 03:004,360 MW4,180 MW
20 Sept, 04:004,232 MW4,130 MW
20 Sept, 05:004,236 MW4,125 MW
20 Sept, 06:004,266 MW4,200 MW
20 Sept, 07:004,300 MW4,233 MW
20 Sept, 08:004,543 MW4,540 MW
20 Sept, 09:004,980 MW4,943 MW
20 Sept, 10:005,747 MW5,308 MW
20 Sept, 11:006,297 MW5,618 MW
20 Sept, 12:006,506 MW5,823 MW
20 Sept, 13:006,160 MW5,798 MW
20 Sept, 14:005,807 MW5,515 MW

Assumptions

  • Only hours with both a forecast and a positive demand reading count (687 of 687 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.