IID Demand Forecast Accuracy: Error, Bias and Worst Miss, 28 September to 28 October 2026
The day-ahead demand forecast for IID was off by 5.3% on average (mean absolute percentage error) over 695 hours from 28 September to 28 October 2026, and 71% of hours landed within 5% of the reading. Its bias was +2.9%: it ran high on average, an over forecast. The largest miss was 275 MW (73.7%) too high at 11 Oct 2026, 14:00 PDT (UTC-07:00). Dates and times are local (America/Los_Angeles).
Key Facts
- The day-ahead demand forecast for IID was off by 5.3% on average (mean absolute percentage error) over 695 hours from 28 September to 28 October 2026, and 71% of hours landed within 5% of the reading. Its bias was +2.9%: it ran high on average, an over forecast. The largest miss was 275 MW (73.7%) too high at 11 Oct 2026, 14:00 PDT (UTC-07:00).
- Across 53 US grids ranked by average error over their own latest 30 day windows, IID came 34 (1 is the smallest error).
- On average the forecast differed from reported demand by 21 MW, against average demand of 430 MW.
- The forecast was above reported demand in 59% of compared hours.
Forecast Error at a Glance
695 hours from 28 September to 28 October 2026Average error5.3%
Bias+2.9%
Hours within 5%71%
Worst miss275 MW
Average error is the mean absolute percentage gap between the forecast and reported demand. Bias is the signed mean (+11 MW per hour on average): the forecast ran high on average, an over forecast. The worst miss was 275 MW (73.7%) too high at 11 Oct 2026, 14:00 PDT (UTC-07:00): forecast 648 MW, reported 373 MW.
Source: U.S. Energy Information Administration (EIA). (US Government work, public domain) Data as of 2026-10-28. 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 28 Oct 2026, 04:00 PDT (UTC-07:00)Data to 2026-10-28
Show the data table (168 rows)
| Local hour | Reported demand | Day-ahead forecast |
|---|---|---|
| 21 Oct, 05:00 | 312 MW | 310 MW |
| 21 Oct, 06:00 | 339 MW | 329 MW |
| 21 Oct, 07:00 | 347 MW | 339 MW |
| 21 Oct, 08:00 | 368 MW | 355 MW |
| 21 Oct, 09:00 | 382 MW | 366 MW |
| 21 Oct, 10:00 | 412 MW | 388 MW |
| 21 Oct, 11:00 | 449 MW | 414 MW |
| 21 Oct, 12:00 | 483 MW | 454 MW |
| 21 Oct, 13:00 | 514 MW | 480 MW |
| 21 Oct, 14:00 | 553 MW | 515 MW |
| 21 Oct, 15:00 | 565 MW | 535 MW |
| 21 Oct, 16:00 | 574 MW | 541 MW |
| 21 Oct, 17:00 | 554 MW | 540 MW |
| 21 Oct, 18:00 | 532 MW | 511 MW |
| 21 Oct, 19:00 | 503 MW | 481 MW |
| 21 Oct, 20:00 | 470 MW | 449 MW |
| 21 Oct, 21:00 | 443 MW | 419 MW |
| 21 Oct, 22:00 | 411 MW | 386 MW |
| 21 Oct, 23:00 | 370 MW | 352 MW |
| 22 Oct, 00:00 | 334 MW | 328 MW |
| 22 Oct, 01:00 | 323 MW | 309 MW |
| 22 Oct, 02:00 | 305 MW | 294 MW |
| 22 Oct, 03:00 | 310 MW | 290 MW |
| 22 Oct, 04:00 | 301 MW | 293 MW |
| 22 Oct, 05:00 | 324 MW | 308 MW |
| 22 Oct, 06:00 | 352 MW | 332 MW |
| 22 Oct, 07:00 | 357 MW | 340 MW |
| 22 Oct, 08:00 | 367 MW | 353 MW |
| 22 Oct, 09:00 | 378 MW | 363 MW |
| 22 Oct, 10:00 | 389 MW | 375 MW |
| 22 Oct, 11:00 | 399 MW | 388 MW |
| 22 Oct, 12:00 | 427 MW | 406 MW |
| 22 Oct, 13:00 | 446 MW | 425 MW |
| 22 Oct, 14:00 | 452 MW | 434 MW |
| 22 Oct, 15:00 | 450 MW | 447 MW |
| 22 Oct, 16:00 | 455 MW | 446 MW |
| 22 Oct, 17:00 | 440 MW | 442 MW |
| 22 Oct, 18:00 | 425 MW | 428 MW |
| 22 Oct, 19:00 | 398 MW | 411 MW |
| 22 Oct, 20:00 | 383 MW | 392 MW |
| 22 Oct, 21:00 | 356 MW | 369 MW |
| 22 Oct, 22:00 | 333 MW | 343 MW |
| 22 Oct, 23:00 | 295 MW | 315 MW |
| 23 Oct, 00:00 | 286 MW | 286 MW |
| 23 Oct, 01:00 | 276 MW | 272 MW |
| 23 Oct, 02:00 | 261 MW | 263 MW |
| 23 Oct, 03:00 | 264 MW | 259 MW |
| 23 Oct, 04:00 | 262 MW | 265 MW |
| 23 Oct, 05:00 | 277 MW | 281 MW |
| 23 Oct, 06:00 | 311 MW | 305 MW |
| 23 Oct, 07:00 | 314 MW | 309 MW |
| 23 Oct, 08:00 | 321 MW | 314 MW |
| 23 Oct, 09:00 | 334 MW | 320 MW |
| 23 Oct, 10:00 | 333 MW | 325 MW |
| 23 Oct, 11:00 | 348 MW | 337 MW |
| 23 Oct, 12:00 | 367 MW | 358 MW |
| 23 Oct, 13:00 | 402 MW | 372 MW |
| 23 Oct, 14:00 | 440 MW | 389 MW |
| 23 Oct, 15:00 | 433 MW | 403 MW |
| 23 Oct, 16:00 | 435 MW | 415 MW |
| 23 Oct, 17:00 | 417 MW | 424 MW |
| 23 Oct, 18:00 | 415 MW | 416 MW |
| 23 Oct, 19:00 | 403 MW | 399 MW |
| 23 Oct, 20:00 | 382 MW | 380 MW |
| 23 Oct, 21:00 | 360 MW | 362 MW |
| 23 Oct, 22:00 | 346 MW | 338 MW |
| 23 Oct, 23:00 | 316 MW | 310 MW |
| 24 Oct, 00:00 | 291 MW | 287 MW |
| 24 Oct, 01:00 | 281 MW | 272 MW |
| 24 Oct, 02:00 | 269 MW | 260 MW |
| 24 Oct, 03:00 | 260 MW | 255 MW |
| 24 Oct, 04:00 | 264 MW | 254 MW |
| 24 Oct, 05:00 | 271 MW | 260 MW |
| 24 Oct, 06:00 | 285 MW | 272 MW |
| 24 Oct, 07:00 | 288 MW | 272 MW |
| 24 Oct, 08:00 | 303 MW | 282 MW |
| 24 Oct, 09:00 | 310 MW | 288 MW |
| 24 Oct, 10:00 | 323 MW | 297 MW |
| 24 Oct, 11:00 | 335 MW | 310 MW |
| 24 Oct, 12:00 | 348 MW | 334 MW |
| 24 Oct, 13:00 | 384 MW | 355 MW |
| 24 Oct, 14:00 | 417 MW | 377 MW |
| 24 Oct, 15:00 | 433 MW | 405 MW |
| 24 Oct, 16:00 | 446 MW | 423 MW |
| 24 Oct, 17:00 | 453 MW | 422 MW |
| 24 Oct, 18:00 | 425 MW | 415 MW |
| 24 Oct, 19:00 | 400 MW | 395 MW |
| 24 Oct, 20:00 | 372 MW | 373 MW |
| 24 Oct, 21:00 | 348 MW | 351 MW |
| 24 Oct, 22:00 | 336 MW | 327 MW |
| 24 Oct, 23:00 | 307 MW | 303 MW |
| 25 Oct, 00:00 | 281 MW | 281 MW |
| 25 Oct, 01:00 | 272 MW | 266 MW |
| 25 Oct, 02:00 | 252 MW | 255 MW |
| 25 Oct, 03:00 | 253 MW | 248 MW |
| 25 Oct, 04:00 | 248 MW | 246 MW |
| 25 Oct, 05:00 | 250 MW | 251 MW |
| 25 Oct, 06:00 | 262 MW | 256 MW |
| 25 Oct, 07:00 | 267 MW | 255 MW |
| 25 Oct, 08:00 | 275 MW | 267 MW |
| 25 Oct, 09:00 | 280 MW | 274 MW |
| 25 Oct, 10:00 | 305 MW | 286 MW |
| 25 Oct, 11:00 | 318 MW | 302 MW |
| 25 Oct, 12:00 | 354 MW | 330 MW |
| 25 Oct, 13:00 | 373 MW | 356 MW |
| 25 Oct, 14:00 | 411 MW | 385 MW |
| 25 Oct, 15:00 | 450 MW | 415 MW |
| 25 Oct, 16:00 | 453 MW | 437 MW |
| 25 Oct, 17:00 | 450 MW | 443 MW |
| 25 Oct, 18:00 | 436 MW | 434 MW |
| 25 Oct, 19:00 | 409 MW | 410 MW |
| 25 Oct, 20:00 | 376 MW | 390 MW |
| 25 Oct, 21:00 | 355 MW | 364 MW |
| 25 Oct, 22:00 | 323 MW | 335 MW |
| 25 Oct, 23:00 | 295 MW | 305 MW |
| 26 Oct, 00:00 | 275 MW | 278 MW |
| 26 Oct, 01:00 | 256 MW | 266 MW |
| 26 Oct, 02:00 | 251 MW | 255 MW |
| 26 Oct, 03:00 | 246 MW | 251 MW |
| 26 Oct, 04:00 | 250 MW | 256 MW |
| 26 Oct, 05:00 | 268 MW | 272 MW |
| 26 Oct, 06:00 | 300 MW | 296 MW |
| 26 Oct, 07:00 | 316 MW | 303 MW |
| 26 Oct, 08:00 | 310 MW | 313 MW |
| 26 Oct, 09:00 | 323 MW | 319 MW |
| 26 Oct, 10:00 | 333 MW | 335 MW |
| 26 Oct, 11:00 | 355 MW | 355 MW |
| 26 Oct, 12:00 | 377 MW | 389 MW |
| 26 Oct, 13:00 | 409 MW | 414 MW |
| 26 Oct, 14:00 | 448 MW | 446 MW |
| 26 Oct, 15:00 | 479 MW | 474 MW |
| 26 Oct, 16:00 | 488 MW | 489 MW |
| 26 Oct, 17:00 | 479 MW | 493 MW |
| 26 Oct, 18:00 | 454 MW | 476 MW |
| 26 Oct, 19:00 | 432 MW | 446 MW |
| 26 Oct, 20:00 | 388 MW | 419 MW |
| 26 Oct, 21:00 | 352 MW | 388 MW |
| 26 Oct, 22:00 | 342 MW | 354 MW |
| 26 Oct, 23:00 | 316 MW | 319 MW |
| 27 Oct, 00:00 | 285 MW | 286 MW |
| 27 Oct, 01:00 | 269 MW | 272 MW |
| 27 Oct, 02:00 | 267 MW | 261 MW |
| 27 Oct, 03:00 | 258 MW | 256 MW |
| 27 Oct, 04:00 | 255 MW | 261 MW |
| 27 Oct, 05:00 | 281 MW | 277 MW |
| 27 Oct, 06:00 | 303 MW | 300 MW |
| 27 Oct, 07:00 | 314 MW | 308 MW |
| 27 Oct, 08:00 | 321 MW | 311 MW |
| 27 Oct, 09:00 | 320 MW | 313 MW |
| 27 Oct, 10:00 | 340 MW | 328 MW |
| 27 Oct, 11:00 | 348 MW | 348 MW |
| 27 Oct, 12:00 | 379 MW | 382 MW |
| 27 Oct, 13:00 | 407 MW | 406 MW |
| 27 Oct, 14:00 | 432 MW | 443 MW |
| 27 Oct, 15:00 | 466 MW | 472 MW |
| 27 Oct, 16:00 | 480 MW | 480 MW |
| 27 Oct, 17:00 | 472 MW | 486 MW |
| 27 Oct, 18:00 | 453 MW | 467 MW |
| 27 Oct, 19:00 | 435 MW | 438 MW |
| 27 Oct, 20:00 | 400 MW | 407 MW |
| 27 Oct, 21:00 | 378 MW | 378 MW |
| 27 Oct, 22:00 | 347 MW | 346 MW |
| 27 Oct, 23:00 | 318 MW | 314 MW |
| 28 Oct, 00:00 | 299 MW | 289 MW |
| 28 Oct, 01:00 | 279 MW | 272 MW |
| 28 Oct, 02:00 | 266 MW | 261 MW |
| 28 Oct, 03:00 | 258 MW | 256 MW |
| 28 Oct, 04:00 | 258 MW | 260 MW |
Assumptions
- Only hours with both a forecast and a positive demand reading count (695 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.
Related
Cite this page
APA 7
World Power Monitor. (2026). IID Demand Forecast Accuracy: Error, Bias and Worst Miss. https://worldpowermonitor.com/forecast-accuracy/iid/
Plain text
World Power Monitor. IID Demand Forecast Accuracy: Error, Bias and Worst Miss. Data as of 2026-10-28. Data from U.S. Energy Information Administration. https://worldpowermonitor.com/forecast-accuracy/iid/
BibTeX
@misc{wpm_forecast_accuracy_iid_2026,
title = {{IID Demand Forecast Accuracy: Error, Bias and Worst Miss}},
author = {{World Power Monitor}},
year = {2026},
note = {Data as of 2026-10-28. Data from U.S. Energy Information Administration.},
url = {https://worldpowermonitor.com/forecast-accuracy/iid/}
} Permalink: https://worldpowermonitor.com/forecast-accuracy/iid/
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