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

NWMT Demand Forecast Accuracy: Error, Bias and Worst Miss, 21 August to 20 September 2026

The day-ahead demand forecast for NWMT was off by 2.0% on average (mean absolute percentage error) over 719 hours from 21 August to 20 September 2026, and 93% of hours landed within 5% of the reading. Its bias was -0.6%: it ran low on average, an under forecast. The largest miss was 335 MW (19.7%) too low at 28 Aug 2026, 08:00 MDT (UTC-06:00). Dates and times are local (America/Denver).

Key Facts

  • The day-ahead demand forecast for NWMT was off by 2.0% on average (mean absolute percentage error) over 719 hours from 21 August to 20 September 2026, and 93% of hours landed within 5% of the reading. Its bias was -0.6%: it ran low on average, an under forecast. The largest miss was 335 MW (19.7%) too low at 28 Aug 2026, 08:00 MDT (UTC-06:00).
  • Across 53 US grids ranked by average error over their own latest 30 day windows, NWMT came 7 (1 is the smallest error).
  • On average the forecast differed from reported demand by 27 MW, against average demand of 1,292 MW.
  • The forecast was above reported demand in 40% of compared hours.

Forecast Error at a Glance

719 hours from 21 August to 20 September 2026
Average error2.0%
Bias-0.6%
Hours within 5%93%
Worst miss335 MW

Average error is the mean absolute percentage gap between the forecast and reported demand. Bias is the signed mean (-9 MW per hour on average): the forecast ran low on average, an under forecast. The worst miss was 335 MW (19.7%) too low at 28 Aug 2026, 08:00 MDT (UTC-06:00): forecast 1,366 MW, reported 1,701 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, 19:00 MDT (UTC-06:00)
NWMT day-ahead demand forecast and reported demand by hour Hourly reported demand and the day-ahead forecast for NWMT over the last 7 days of the window, to 20 Sept 2026, 19:00 MDT (UTC-06:00). Gaps are hours with a missing, zero or implausible report. 0 375 750 1,125 1,500 13 Sept, 20:0014 Sept, 20:0015 Sept, 20:0016 Sept, 20:0017 Sept, 20:0018 Sept, 20:0019 Sept, 20:00
Hourly reported demand and the day-ahead forecast for NWMT over the last 7 days of the window, to 20 Sept 2026, 19:00 MDT (UTC-06:00). Gaps are hours with a missing, zero or implausible report.
Data to 2026-09-20
NWMT day-ahead demand forecast and reported demand by hour
Local hourReported demandDay-ahead forecast
13 Sept, 20:001,420 MW1,293 MW
13 Sept, 21:001,336 MW1,235 MW
13 Sept, 22:001,246 MW1,145 MW
13 Sept, 23:001,164 MW1,088 MW
14 Sept, 00:001,129 MW1,129 MW
14 Sept, 01:001,118 MW1,085 MW
14 Sept, 02:001,082 MW1,112 MW
14 Sept, 03:001,105 MW1,100 MW
14 Sept, 04:001,100 MW1,118 MW
14 Sept, 05:001,167 MW1,182 MW
14 Sept, 06:001,249 MW1,257 MW
14 Sept, 07:001,331 MW1,289 MW
14 Sept, 08:001,330 MW1,291 MW
14 Sept, 09:001,317 MW1,291 MW
14 Sept, 10:001,307 MW1,289 MW
14 Sept, 11:001,329 MW1,288 MW
14 Sept, 12:001,331 MW1,293 MW
14 Sept, 13:001,343 MW1,294 MW
14 Sept, 14:001,330 MW1,292 MW
14 Sept, 15:001,338 MW1,301 MW
14 Sept, 16:001,362 MW1,334 MW
14 Sept, 17:001,376 MW1,344 MW
14 Sept, 18:001,381 MW1,333 MW
14 Sept, 19:001,395 MW1,339 MW
14 Sept, 20:001,376 MW1,323 MW
14 Sept, 21:001,309 MW1,252 MW
14 Sept, 22:001,227 MW1,155 MW
14 Sept, 23:001,159 MW1,089 MW
15 Sept, 00:001,110 MW1,127 MW
15 Sept, 01:001,086 MW1,098 MW
15 Sept, 02:001,080 MW1,078 MW
15 Sept, 03:001,081 MW1,083 MW
15 Sept, 04:001,094 MW1,092 MW
15 Sept, 05:001,135 MW1,146 MW
15 Sept, 06:001,261 MW1,247 MW
15 Sept, 07:001,309 MW1,302 MW
15 Sept, 08:001,289 MW1,301 MW
15 Sept, 09:001,275 MW1,293 MW
15 Sept, 10:001,244 MW1,281 MW
15 Sept, 11:001,224 MW1,273 MW
15 Sept, 12:001,218 MW1,270 MW
15 Sept, 13:001,217 MW1,273 MW
15 Sept, 14:001,229 MW1,280 MW
15 Sept, 15:001,250 MW1,301 MW
15 Sept, 16:001,284 MW1,321 MW
15 Sept, 17:001,308 MW1,349 MW
15 Sept, 18:001,335 MW1,356 MW
15 Sept, 19:001,354 MW1,338 MW
15 Sept, 20:001,363 MW1,355 MW
15 Sept, 21:001,317 MW1,303 MW
15 Sept, 22:001,242 MW1,217 MW
15 Sept, 23:001,157 MW1,149 MW
16 Sept, 00:001,113 MW1,124 MW
16 Sept, 01:001,049 MW1,092 MW
16 Sept, 02:001,052 MW1,079 MW
16 Sept, 03:001,049 MW1,059 MW
16 Sept, 04:001,071 MW1,071 MW
16 Sept, 05:001,124 MW1,120 MW
16 Sept, 06:001,229 MW1,229 MW
16 Sept, 07:001,267 MW1,284 MW
16 Sept, 08:001,253 MW1,280 MW
16 Sept, 09:001,233 MW1,268 MW
16 Sept, 10:001,223 MW1,250 MW
16 Sept, 11:001,212 MW1,237 MW
16 Sept, 12:001,200 MW1,228 MW
16 Sept, 13:001,214 MW1,226 MW
16 Sept, 14:001,228 MW1,248 MW
16 Sept, 15:001,246 MW1,278 MW
16 Sept, 16:001,268 MW1,303 MW
16 Sept, 17:001,287 MW1,335 MW
16 Sept, 18:001,300 MW1,342 MW
16 Sept, 19:001,306 MW1,327 MW
16 Sept, 20:001,306 MW1,327 MW
16 Sept, 21:001,251 MW1,276 MW
16 Sept, 22:001,181 MW1,190 MW
16 Sept, 23:001,112 MW1,122 MW
17 Sept, 00:001,083 MW1,070 MW
17 Sept, 01:001,048 MW1,052 MW
17 Sept, 02:001,052 MW1,044 MW
17 Sept, 03:001,055 MW1,041 MW
17 Sept, 04:001,071 MW1,065 MW
17 Sept, 05:001,139 MW1,115 MW
17 Sept, 06:001,228 MW1,218 MW
17 Sept, 07:001,289 MW1,275 MW
17 Sept, 08:001,277 MW1,271 MW
17 Sept, 09:001,277 MW1,254 MW
17 Sept, 10:001,265 MW1,235 MW
17 Sept, 11:001,253 MW1,223 MW
17 Sept, 12:001,251 MW1,228 MW
17 Sept, 13:001,258 MW1,242 MW
17 Sept, 14:001,275 MW1,286 MW
17 Sept, 15:001,288 MW1,325 MW
17 Sept, 16:001,299 MW1,361 MW
17 Sept, 17:001,321 MW1,402 MW
17 Sept, 18:001,327 MW1,414 MW
17 Sept, 19:001,347 MW1,397 MW
17 Sept, 20:001,342 MW1,369 MW
17 Sept, 21:001,287 MW1,301 MW
17 Sept, 22:001,204 MW1,224 MW
17 Sept, 23:001,142 MW1,147 MW
18 Sept, 00:001,104 MW1,104 MW
18 Sept, 01:001,075 MW1,071 MW
18 Sept, 02:001,059 MW1,059 MW
18 Sept, 03:001,054 MW1,054 MW
18 Sept, 04:001,069 MW1,064 MW
18 Sept, 05:001,100 MW1,107 MW
18 Sept, 06:001,184 MW1,187 MW
18 Sept, 07:001,259 MW1,248 MW
18 Sept, 08:001,259 MW1,260 MW
18 Sept, 09:001,242 MW1,260 MW
18 Sept, 10:001,234 MW1,257 MW
18 Sept, 11:001,235 MW1,262 MW
18 Sept, 12:001,243 MW1,269 MW
18 Sept, 13:001,283 MW1,289 MW
18 Sept, 14:001,320 MW1,316 MW
18 Sept, 15:001,331 MW1,339 MW
18 Sept, 16:001,350 MW1,364 MW
18 Sept, 17:001,366 MW1,378 MW
18 Sept, 18:001,373 MW1,363 MW
18 Sept, 19:001,363 MW1,339 MW
18 Sept, 20:001,347 MW1,316 MW
18 Sept, 21:001,290 MW1,273 MW
18 Sept, 22:001,208 MW1,203 MW
18 Sept, 23:001,154 MW1,140 MW
19 Sept, 00:001,113 MW1,103 MW
19 Sept, 01:001,100 MW1,067 MW
19 Sept, 02:001,071 MW1,062 MW
19 Sept, 03:001,056 MW1,065 MW
19 Sept, 04:001,052 MW1,064 MW
19 Sept, 05:001,064 MW1,081 MW
19 Sept, 06:001,111 MW1,111 MW
19 Sept, 07:001,146 MW1,146 MW
19 Sept, 08:001,211 MW1,178 MW
19 Sept, 09:001,239 MW1,196 MW
19 Sept, 10:001,244 MW1,193 MW
19 Sept, 11:001,250 MW1,182 MW
19 Sept, 12:001,240 MW1,176 MW
19 Sept, 13:001,217 MW1,165 MW
19 Sept, 14:001,205 MW1,167 MW
19 Sept, 15:001,195 MW1,174 MW
19 Sept, 16:001,211 MW1,185 MW
19 Sept, 17:001,238 MW1,218 MW
19 Sept, 18:001,250 MW1,229 MW
19 Sept, 19:001,269 MW1,247 MW
19 Sept, 20:001,261 MW1,264 MW
19 Sept, 21:001,214 MW1,220 MW
19 Sept, 22:001,149 MW1,155 MW
19 Sept, 23:001,091 MW1,106 MW
20 Sept, 00:001,059 MW1,073 MW
20 Sept, 01:001,042 MW1,035 MW
20 Sept, 02:001,039 MW1,025 MW
20 Sept, 03:001,012 MW1,034 MW
20 Sept, 04:001,025 MW1,030 MW
20 Sept, 05:001,044 MW1,039 MW
20 Sept, 06:001,083 MW1,074 MW
20 Sept, 07:001,130 MW1,104 MW
20 Sept, 08:001,174 MW1,136 MW
20 Sept, 09:001,170 MW1,161 MW
20 Sept, 10:001,159 MW1,162 MW
20 Sept, 11:001,170 MW1,160 MW
20 Sept, 12:001,181 MW1,163 MW
20 Sept, 13:001,180 MW1,170 MW
20 Sept, 14:001,188 MW1,185 MW
20 Sept, 15:001,205 MW1,213 MW
20 Sept, 16:001,233 MW1,255 MW
20 Sept, 17:001,283 MW1,305 MW
20 Sept, 18:001,300 MW1,319 MW
20 Sept, 19:001,306 MW1,305 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.