TIDC Demand Forecast Accuracy: Error, Bias and Worst Miss, 21 August to 20 September 2026
The day-ahead demand forecast for TIDC was off by 3.4% on average (mean absolute percentage error) over 717 hours from 21 August to 20 September 2026, and 80% of hours landed within 5% of the reading. Its bias was -0.4%: it ran close to balanced on average. The largest miss was 98 MW (19.1%) too high at 27 Aug 2026, 18:00 PDT (UTC-07:00). Dates and times are local (America/Los_Angeles).
Key Facts
- The day-ahead demand forecast for TIDC was off by 3.4% on average (mean absolute percentage error) over 717 hours from 21 August to 20 September 2026, and 80% of hours landed within 5% of the reading. Its bias was -0.4%: it ran close to balanced on average. The largest miss was 98 MW (19.1%) too high at 27 Aug 2026, 18:00 PDT (UTC-07:00).
- Across 53 US grids ranked by average error over their own latest 30 day windows, TIDC came 23 (1 is the smallest error).
- On average the forecast differed from reported demand by 14 MW, against average demand of 385 MW.
- The forecast was above reported demand in 38% of compared hours.
Forecast Error at a Glance
717 hours from 21 August to 20 September 2026Average error3.4%
Bias-0.4%
Hours within 5%80%
Worst miss98 MW
Average error is the mean absolute percentage gap between the forecast and reported demand. Bias is the signed mean (-2 MW per hour on average): the forecast ran close to balanced on average. The worst miss was 98 MW (19.1%) too high at 27 Aug 2026, 18:00 PDT (UTC-07:00): forecast 611 MW, reported 513 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, 16:00 PDT (UTC-07:00)Data to 2026-09-20
| Local hour | Reported demand | Day-ahead forecast |
|---|---|---|
| 13 Sept, 17:00 | 382 MW | 424 MW |
| 13 Sept, 18:00 | 385 MW | 422 MW |
| 13 Sept, 19:00 | 382 MW | 411 MW |
| 13 Sept, 20:00 | 372 MW | 396 MW |
| 13 Sept, 21:00 | 353 MW | 372 MW |
| 13 Sept, 22:00 | 330 MW | 345 MW |
| 13 Sept, 23:00 | 304 MW | 316 MW |
| 14 Sept, 00:00 | 284 MW | 300 MW |
| 14 Sept, 01:00 | 273 MW | 287 MW |
| 14 Sept, 02:00 | 266 MW | 277 MW |
| 14 Sept, 03:00 | 262 MW | 272 MW |
| 14 Sept, 04:00 | 266 MW | 275 MW |
| 14 Sept, 05:00 | 281 MW | 288 MW |
| 14 Sept, 06:00 | 309 MW | 314 MW |
| 14 Sept, 07:00 | 325 MW | 328 MW |
| 14 Sept, 08:00 | 325 MW | 334 MW |
| 14 Sept, 09:00 | 327 MW | 339 MW |
| 14 Sept, 10:00 | 329 MW | 349 MW |
| 14 Sept, 11:00 | 337 MW | 365 MW |
| 14 Sept, 12:00 | 354 MW | 389 MW |
| 14 Sept, 13:00 | 377 MW | 415 MW |
| 14 Sept, 14:00 | 402 MW | 441 MW |
| 14 Sept, 15:00 | 431 MW | 466 MW |
| 14 Sept, 16:00 | 453 MW | 484 MW |
| 14 Sept, 17:00 | 467 MW | 489 MW |
| 14 Sept, 18:00 | 466 MW | 480 MW |
| 14 Sept, 19:00 | 452 MW | 465 MW |
| 14 Sept, 20:00 | 433 MW | 445 MW |
| 14 Sept, 21:00 | 406 MW | 416 MW |
| 14 Sept, 22:00 | 374 MW | 381 MW |
| 14 Sept, 23:00 | 344 MW | 350 MW |
| 15 Sept, 00:00 | 322 MW | 318 MW |
| 15 Sept, 01:00 | 306 MW | 303 MW |
| 15 Sept, 02:00 | 295 MW | 292 MW |
| 15 Sept, 03:00 | 289 MW | 287 MW |
| 15 Sept, 04:00 | 289 MW | 289 MW |
| 15 Sept, 05:00 | 298 MW | 301 MW |
| 15 Sept, 06:00 | 319 MW | 323 MW |
| 15 Sept, 07:00 | 327 MW | 335 MW |
| 15 Sept, 08:00 | 329 MW | 337 MW |
| 15 Sept, 09:00 | 340 MW | 341 MW |
| 15 Sept, 10:00 | 343 MW | 351 MW |
| 15 Sept, 11:00 | 350 MW | 360 MW |
| 15 Sept, 12:00 | 376 MW | 383 MW |
| 15 Sept, 13:00 | 408 MW | 410 MW |
| 15 Sept, 14:00 | 444 MW | 438 MW |
| 15 Sept, 15:00 | 473 MW | 464 MW |
| 15 Sept, 16:00 | 500 MW | 481 MW |
| 15 Sept, 17:00 | 515 MW | 491 MW |
| 15 Sept, 18:00 | 507 MW | 482 MW |
| 15 Sept, 19:00 | 488 MW | 468 MW |
| 15 Sept, 20:00 | 464 MW | 449 MW |
| 15 Sept, 21:00 | 431 MW | 422 MW |
| 15 Sept, 22:00 | 394 MW | 386 MW |
| 15 Sept, 23:00 | 359 MW | 352 MW |
| 16 Sept, 00:00 | 333 MW | 324 MW |
| 16 Sept, 01:00 | 312 MW | 307 MW |
| 16 Sept, 02:00 | 297 MW | 296 MW |
| 16 Sept, 03:00 | 288 MW | 292 MW |
| 16 Sept, 04:00 | 291 MW | 295 MW |
| 16 Sept, 05:00 | 302 MW | 306 MW |
| 16 Sept, 06:00 | 319 MW | 327 MW |
| 16 Sept, 07:00 | 322 MW | 337 MW |
| 16 Sept, 08:00 | 320 MW | 339 MW |
| 16 Sept, 09:00 | 320 MW | 340 MW |
| 16 Sept, 10:00 | 322 MW | 343 MW |
| 16 Sept, 11:00 | 329 MW | 352 MW |
| 16 Sept, 12:00 | 348 MW | 371 MW |
| 16 Sept, 13:00 | 374 MW | 392 MW |
| 16 Sept, 14:00 | 402 MW | 417 MW |
| 16 Sept, 15:00 | 431 MW | 440 MW |
| 16 Sept, 16:00 | 448 MW | 460 MW |
| 16 Sept, 17:00 | 453 MW | 471 MW |
| 16 Sept, 18:00 | 437 MW | 467 MW |
| 16 Sept, 19:00 | 416 MW | 451 MW |
| 16 Sept, 20:00 | 397 MW | 431 MW |
| 16 Sept, 21:00 | 373 MW | 406 MW |
| 16 Sept, 22:00 | 349 MW | 374 MW |
| 16 Sept, 23:00 | 324 MW | 345 MW |
| 17 Sept, 00:00 | 306 MW | 320 MW |
| 17 Sept, 01:00 | 294 MW | 304 MW |
| 17 Sept, 02:00 | 284 MW | 294 MW |
| 17 Sept, 03:00 | 279 MW | 288 MW |
| 17 Sept, 04:00 | 282 MW | 290 MW |
| 17 Sept, 05:00 | 292 MW | 301 MW |
| 17 Sept, 06:00 | 315 MW | 322 MW |
| 17 Sept, 07:00 | 323 MW | 333 MW |
| 17 Sept, 08:00 | 322 MW | 334 MW |
| 17 Sept, 09:00 | 321 MW | 336 MW |
| 17 Sept, 10:00 | 322 MW | 340 MW |
| 17 Sept, 11:00 | 325 MW | 349 MW |
| 17 Sept, 12:00 | 331 MW | 365 MW |
| 17 Sept, 13:00 | 344 MW | 386 MW |
| 17 Sept, 14:00 | 361 MW | 409 MW |
| 17 Sept, 15:00 | 381 MW | 428 MW |
| 17 Sept, 16:00 | 400 MW | 441 MW |
| 17 Sept, 17:00 | 411 MW | 447 MW |
| 17 Sept, 18:00 | 408 MW | 441 MW |
| 17 Sept, 19:00 | 406 MW | 431 MW |
| 17 Sept, 20:00 | 395 MW | 416 MW |
| 17 Sept, 21:00 | 376 MW | 393 MW |
| 17 Sept, 22:00 | 351 MW | 364 MW |
| 17 Sept, 23:00 | 328 MW | 338 MW |
| 18 Sept, 00:00 | 309 MW | 309 MW |
| 18 Sept, 01:00 | 294 MW | 292 MW |
| 18 Sept, 02:00 | 285 MW | 282 MW |
| 18 Sept, 03:00 | 281 MW | 276 MW |
| 18 Sept, 04:00 | 285 MW | 277 MW |
| 18 Sept, 05:00 | 295 MW | 287 MW |
| 18 Sept, 06:00 | 313 MW | 308 MW |
| 18 Sept, 07:00 | 322 MW | 323 MW |
| 18 Sept, 08:00 | 322 MW | 325 MW |
| 18 Sept, 09:00 | 322 MW | 323 MW |
| 18 Sept, 10:00 | 322 MW | 325 MW |
| 18 Sept, 11:00 | 328 MW | 334 MW |
| 18 Sept, 12:00 | 342 MW | 354 MW |
| 18 Sept, 13:00 | 363 MW | 378 MW |
| 18 Sept, 14:00 | 386 MW | 402 MW |
| 18 Sept, 15:00 | 408 MW | 423 MW |
| 18 Sept, 16:00 | 428 MW | 441 MW |
| 18 Sept, 17:00 | 438 MW | 448 MW |
| 18 Sept, 18:00 | 433 MW | 438 MW |
| 18 Sept, 19:00 | 421 MW | 428 MW |
| 18 Sept, 20:00 | 403 MW | 410 MW |
| 18 Sept, 21:00 | 382 MW | 385 MW |
| 18 Sept, 22:00 | 359 MW | 357 MW |
| 18 Sept, 23:00 | 334 MW | 329 MW |
| 19 Sept, 00:00 | 313 MW | 315 MW |
| 19 Sept, 01:00 | 296 MW | 296 MW |
| 19 Sept, 02:00 | 283 MW | 282 MW |
| 19 Sept, 03:00 | 274 MW | 273 MW |
| 19 Sept, 04:00 | 272 MW | 269 MW |
| 19 Sept, 05:00 | 275 MW | 272 MW |
| 19 Sept, 06:00 | 281 MW | 277 MW |
| 19 Sept, 07:00 | 284 MW | 280 MW |
| 19 Sept, 08:00 | 289 MW | 286 MW |
| 19 Sept, 09:00 | 294 MW | 294 MW |
| 19 Sept, 10:00 | 302 MW | 308 MW |
| 19 Sept, 11:00 | 315 MW | 326 MW |
| 19 Sept, 12:00 | 334 MW | 350 MW |
| 19 Sept, 13:00 | 358 MW | 379 MW |
| 19 Sept, 14:00 | 388 MW | 405 MW |
| 19 Sept, 15:00 | 415 MW | 429 MW |
| 19 Sept, 16:00 | 439 MW | 448 MW |
| 19 Sept, 17:00 | 451 MW | 455 MW |
| 19 Sept, 18:00 | 447 MW | 444 MW |
| 19 Sept, 19:00 | 428 MW | 426 MW |
| 19 Sept, 20:00 | 405 MW | 405 MW |
| 19 Sept, 21:00 | 382 MW | 379 MW |
| 19 Sept, 22:00 | 355 MW | 350 MW |
| 19 Sept, 23:00 | 328 MW | 322 MW |
| 20 Sept, 00:00 | 307 MW | 306 MW |
| 20 Sept, 01:00 | 290 MW | 289 MW |
| 20 Sept, 02:00 | 276 MW | 276 MW |
| 20 Sept, 03:00 | 266 MW | 268 MW |
| 20 Sept, 04:00 | 261 MW | 264 MW |
| 20 Sept, 05:00 | 260 MW | 262 MW |
| 20 Sept, 06:00 | 260 MW | 261 MW |
| 20 Sept, 07:00 | 257 MW | 259 MW |
| 20 Sept, 08:00 | 262 MW | 262 MW |
| 20 Sept, 09:00 | 271 MW | 266 MW |
| 20 Sept, 10:00 | 277 MW | 274 MW |
| 20 Sept, 11:00 | 278 MW | 286 MW |
| 20 Sept, 12:00 | 300 MW | 303 MW |
| 20 Sept, 13:00 | 307 MW | 325 MW |
| 20 Sept, 14:00 | 326 MW | 349 MW |
| 20 Sept, 15:00 | 357 MW | 373 MW |
| 20 Sept, 16:00 | 368 MW | 394 MW |
Assumptions
- Only hours with both a forecast and a positive demand reading count (717 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.