TAL Demand Forecast Accuracy: Error, Bias and Worst Miss, 21 August to 20 September 2026
The day-ahead demand forecast for TAL was off by 3.4% on average (mean absolute percentage error) over 719 hours from 21 August to 20 September 2026, and 80% of hours landed within 5% of the reading. Its bias was -1.2%: it ran low on average, an under forecast. The largest miss was 79 MW (14.4%) too low at 6 Sept 2026, 18:00 EDT (UTC-04:00). Dates and times are local (America/New_York).
Key Facts
- The day-ahead demand forecast for TAL was off by 3.4% on average (mean absolute percentage error) over 719 hours from 21 August to 20 September 2026, and 80% of hours landed within 5% of the reading. Its bias was -1.2%: it ran low on average, an under forecast. The largest miss was 79 MW (14.4%) too low at 6 Sept 2026, 18:00 EDT (UTC-04:00).
- Across 53 US grids ranked by average error over their own latest 30 day windows, TAL came 21 (1 is the smallest error).
- On average the forecast differed from reported demand by 14 MW, against average demand of 406 MW.
- The forecast was above reported demand in 30% of compared hours.
Forecast Error at a Glance
719 hours from 21 August to 20 September 2026Average error3.4%
Bias-1.2%
Hours within 5%80%
Worst miss79 MW
Average error is the mean absolute percentage gap between the forecast and reported demand. Bias is the signed mean (-6 MW per hour on average): the forecast ran low on average, an under forecast. The worst miss was 79 MW (14.4%) too low at 6 Sept 2026, 18:00 EDT (UTC-04:00): forecast 471 MW, reported 550 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, 21:00 EDT (UTC-04:00)Data to 2026-09-20
| Local hour | Reported demand | Day-ahead forecast |
|---|---|---|
| 13 Sept, 22:00 | 428 MW | 395 MW |
| 13 Sept, 23:00 | 393 MW | 364 MW |
| 14 Sept, 00:00 | 364 MW | 361 MW |
| 14 Sept, 01:00 | 341 MW | 338 MW |
| 14 Sept, 02:00 | 322 MW | 319 MW |
| 14 Sept, 03:00 | 309 MW | 306 MW |
| 14 Sept, 04:00 | 305 MW | 310 MW |
| 14 Sept, 05:00 | 311 MW | 318 MW |
| 14 Sept, 06:00 | 330 MW | 319 MW |
| 14 Sept, 07:00 | 343 MW | 323 MW |
| 14 Sept, 08:00 | 360 MW | 345 MW |
| 14 Sept, 09:00 | 388 MW | 369 MW |
| 14 Sept, 10:00 | 420 MW | 402 MW |
| 14 Sept, 11:00 | 458 MW | 444 MW |
| 14 Sept, 12:00 | 496 MW | 483 MW |
| 14 Sept, 13:00 | 522 MW | 507 MW |
| 14 Sept, 14:00 | 540 MW | 521 MW |
| 14 Sept, 15:00 | 555 MW | 538 MW |
| 14 Sept, 16:00 | 557 MW | 552 MW |
| 14 Sept, 17:00 | 557 MW | 554 MW |
| 14 Sept, 18:00 | 543 MW | 542 MW |
| 14 Sept, 19:00 | 515 MW | 521 MW |
| 14 Sept, 20:00 | 494 MW | 494 MW |
| 14 Sept, 21:00 | 458 MW | 469 MW |
| 14 Sept, 22:00 | 450 MW | 436 MW |
| 14 Sept, 23:00 | 394 MW | 395 MW |
| 15 Sept, 00:00 | 351 MW | 348 MW |
| 15 Sept, 01:00 | 326 MW | 323 MW |
| 15 Sept, 02:00 | 309 MW | 306 MW |
| 15 Sept, 03:00 | 297 MW | 294 MW |
| 15 Sept, 04:00 | 294 MW | 299 MW |
| 15 Sept, 05:00 | 303 MW | 312 MW |
| 15 Sept, 06:00 | 325 MW | 328 MW |
| 15 Sept, 07:00 | 340 MW | 336 MW |
| 15 Sept, 08:00 | 354 MW | 351 MW |
| 15 Sept, 09:00 | 381 MW | 381 MW |
| 15 Sept, 10:00 | 419 MW | 416 MW |
| 15 Sept, 11:00 | 467 MW | 451 MW |
| 15 Sept, 12:00 | 497 MW | 482 MW |
| 15 Sept, 13:00 | 527 MW | 506 MW |
| 15 Sept, 14:00 | 552 MW | 527 MW |
| 15 Sept, 15:00 | 576 MW | 544 MW |
| 15 Sept, 16:00 | 571 MW | 553 MW |
| 15 Sept, 17:00 | 590 MW | 544 MW |
| 15 Sept, 18:00 | 545 MW | 525 MW |
| 15 Sept, 19:00 | 522 MW | 504 MW |
| 15 Sept, 20:00 | 525 MW | 476 MW |
| 15 Sept, 21:00 | 488 MW | 443 MW |
| 15 Sept, 22:00 | 461 MW | 403 MW |
| 15 Sept, 23:00 | 420 MW | 363 MW |
| 16 Sept, 00:00 | 384 MW | 367 MW |
| 16 Sept, 01:00 | 377 MW | 342 MW |
| 16 Sept, 02:00 | 341 MW | 327 MW |
| 16 Sept, 03:00 | 321 MW | 316 MW |
| 16 Sept, 04:00 | 317 MW | 312 MW |
| 16 Sept, 05:00 | 322 MW | 327 MW |
| 16 Sept, 06:00 | 341 MW | 341 MW |
| 16 Sept, 07:00 | 349 MW | 342 MW |
| 16 Sept, 08:00 | 355 MW | 346 MW |
| 16 Sept, 09:00 | 379 MW | 364 MW |
| 16 Sept, 10:00 | 406 MW | 382 MW |
| 16 Sept, 11:00 | 431 MW | 407 MW |
| 16 Sept, 12:00 | 456 MW | 437 MW |
| 16 Sept, 13:00 | 487 MW | 464 MW |
| 16 Sept, 14:00 | 504 MW | 486 MW |
| 16 Sept, 15:00 | 527 MW | 502 MW |
| 16 Sept, 16:00 | 490 MW | 507 MW |
| 16 Sept, 17:00 | 511 MW | 504 MW |
| 16 Sept, 18:00 | 496 MW | 492 MW |
| 16 Sept, 19:00 | 480 MW | 476 MW |
| 16 Sept, 20:00 | 468 MW | 454 MW |
| 16 Sept, 21:00 | 427 MW | 425 MW |
| 16 Sept, 22:00 | 386 MW | 393 MW |
| 16 Sept, 23:00 | 370 MW | 360 MW |
| 17 Sept, 00:00 | 345 MW | 323 MW |
| 17 Sept, 01:00 | 316 MW | 300 MW |
| 17 Sept, 02:00 | 290 MW | 283 MW |
| 17 Sept, 03:00 | 273 MW | 269 MW |
| 17 Sept, 04:00 | 268 MW | 265 MW |
| 17 Sept, 05:00 | 275 MW | 280 MW |
| 17 Sept, 06:00 | 300 MW | 297 MW |
| 17 Sept, 07:00 | 319 MW | 308 MW |
| 17 Sept, 08:00 | 331 MW | 319 MW |
| 17 Sept, 09:00 | 359 MW | 342 MW |
| 17 Sept, 10:00 | 383 MW | 372 MW |
| 17 Sept, 11:00 | 416 MW | 407 MW |
| 17 Sept, 12:00 | 443 MW | 436 MW |
| 17 Sept, 13:00 | 467 MW | 457 MW |
| 17 Sept, 14:00 | 497 MW | 478 MW |
| 17 Sept, 15:00 | 507 MW | 485 MW |
| 17 Sept, 16:00 | 512 MW | 488 MW |
| 17 Sept, 17:00 | 528 MW | 494 MW |
| 17 Sept, 18:00 | 503 MW | 486 MW |
| 17 Sept, 19:00 | 493 MW | 467 MW |
| 17 Sept, 20:00 | 455 MW | 441 MW |
| 17 Sept, 21:00 | 427 MW | 411 MW |
| 17 Sept, 22:00 | 404 MW | 381 MW |
| 17 Sept, 23:00 | 352 MW | 347 MW |
| 18 Sept, 00:00 | 343 MW | 314 MW |
| 18 Sept, 01:00 | 303 MW | 290 MW |
| 18 Sept, 02:00 | 279 MW | 273 MW |
| 18 Sept, 03:00 | 265 MW | 262 MW |
| 18 Sept, 04:00 | 259 MW | 256 MW |
| 18 Sept, 05:00 | 265 MW | 273 MW |
| 18 Sept, 06:00 | 291 MW | 289 MW |
| 18 Sept, 07:00 | 306 MW | 302 MW |
| 18 Sept, 08:00 | 327 MW | 319 MW |
| 18 Sept, 09:00 | 355 MW | 348 MW |
| 18 Sept, 10:00 | 387 MW | 378 MW |
| 18 Sept, 11:00 | 420 MW | 410 MW |
| 18 Sept, 12:00 | 453 MW | 445 MW |
| 18 Sept, 13:00 | 476 MW | 475 MW |
| 18 Sept, 14:00 | 504 MW | 496 MW |
| 18 Sept, 15:00 | 523 MW | 513 MW |
| 18 Sept, 16:00 | 527 MW | 528 MW |
| 18 Sept, 17:00 | 545 MW | 525 MW |
| 18 Sept, 18:00 | 517 MW | 507 MW |
| 18 Sept, 19:00 | 496 MW | 485 MW |
| 18 Sept, 20:00 | 458 MW | 452 MW |
| 18 Sept, 21:00 | 432 MW | 423 MW |
| 18 Sept, 22:00 | 418 MW | 400 MW |
| 18 Sept, 23:00 | 367 MW | 371 MW |
| 19 Sept, 00:00 | 350 MW | 333 MW |
| 19 Sept, 01:00 | 327 MW | 313 MW |
| 19 Sept, 02:00 | 303 MW | 297 MW |
| 19 Sept, 03:00 | 288 MW | 284 MW |
| 19 Sept, 04:00 | 278 MW | 276 MW |
| 19 Sept, 05:00 | 274 MW | 281 MW |
| 19 Sept, 06:00 | 276 MW | 287 MW |
| 19 Sept, 07:00 | 280 MW | 290 MW |
| 19 Sept, 08:00 | 294 MW | 305 MW |
| 19 Sept, 09:00 | 328 MW | 336 MW |
| 19 Sept, 10:00 | 369 MW | 368 MW |
| 19 Sept, 11:00 | 413 MW | 405 MW |
| 19 Sept, 12:00 | 456 MW | 438 MW |
| 19 Sept, 13:00 | 491 MW | 469 MW |
| 19 Sept, 14:00 | 513 MW | 493 MW |
| 19 Sept, 15:00 | 528 MW | 506 MW |
| 19 Sept, 16:00 | 533 MW | 516 MW |
| 19 Sept, 17:00 | 529 MW | 500 MW |
| 19 Sept, 18:00 | 511 MW | 466 MW |
| 19 Sept, 19:00 | 487 MW | 437 MW |
| 19 Sept, 20:00 | 467 MW | 412 MW |
| 19 Sept, 21:00 | 443 MW | 389 MW |
| 19 Sept, 22:00 | 416 MW | 362 MW |
| 19 Sept, 23:00 | 390 MW | 333 MW |
| 20 Sept, 00:00 | 362 MW | 360 MW |
| 20 Sept, 01:00 | 339 MW | 337 MW |
| 20 Sept, 02:00 | 321 MW | 319 MW |
| 20 Sept, 03:00 | 307 MW | 305 MW |
| 20 Sept, 04:00 | 295 MW | 293 MW |
| 20 Sept, 05:00 | 288 MW | 292 MW |
| 20 Sept, 06:00 | 288 MW | 297 MW |
| 20 Sept, 07:00 | 291 MW | 289 MW |
| 20 Sept, 08:00 | 304 MW | 294 MW |
| 20 Sept, 09:00 | 325 MW | 327 MW |
| 20 Sept, 10:00 | 348 MW | 363 MW |
| 20 Sept, 11:00 | 378 MW | 401 MW |
| 20 Sept, 12:00 | 411 MW | 435 MW |
| 20 Sept, 13:00 | 446 MW | 460 MW |
| 20 Sept, 14:00 | 481 MW | 476 MW |
| 20 Sept, 15:00 | 486 MW | 481 MW |
| 20 Sept, 16:00 | 473 MW | 480 MW |
| 20 Sept, 17:00 | 447 MW | 471 MW |
| 20 Sept, 18:00 | 419 MW | 452 MW |
| 20 Sept, 19:00 | 404 MW | 447 MW |
| 20 Sept, 20:00 | 395 MW | 443 MW |
| 20 Sept, 21:00 | 374 MW | 418 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.