CHPD Demand Forecast Accuracy: Error, Bias and Worst Miss, 21 August to 20 September 2026
The day-ahead demand forecast for CHPD was off by 2.0% on average (mean absolute percentage error) over 719 hours from 21 August to 20 September 2026, and 96% of hours landed within 5% of the reading. Its bias was -0.5%: it ran low on average, an under forecast. The largest miss was 23 MW (10.6%) too low at 2 Sept 2026, 12:00 PDT (UTC-07:00). Dates and times are local (America/Los_Angeles).
Key Facts
- The day-ahead demand forecast for CHPD was off by 2.0% on average (mean absolute percentage error) over 719 hours from 21 August to 20 September 2026, and 96% of hours landed within 5% of the reading. Its bias was -0.5%: it ran low on average, an under forecast. The largest miss was 23 MW (10.6%) too low at 2 Sept 2026, 12:00 PDT (UTC-07:00).
- Across 53 US grids ranked by average error over their own latest 30 day windows, CHPD came 5 (1 is the smallest error).
- On average the forecast differed from reported demand by 4 MW, against average demand of 186 MW.
- The forecast was above reported demand in 37% of compared hours.
Forecast Error at a Glance
719 hours from 21 August to 20 September 2026Average error2.0%
Bias-0.5%
Hours within 5%96%
Worst miss23 MW
Average error is the mean absolute percentage gap between the forecast and reported demand. Bias is the signed mean (-1 MW per hour on average): the forecast ran low on average, an under forecast. The worst miss was 23 MW (10.6%) too low at 2 Sept 2026, 12:00 PDT (UTC-07:00): forecast 195 MW, reported 218 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, 18:00 PDT (UTC-07:00)Data to 2026-09-20
| Local hour | Reported demand | Day-ahead forecast |
|---|---|---|
| 13 Sept, 19:00 | 188 MW | 186 MW |
| 13 Sept, 20:00 | 186 MW | 184 MW |
| 13 Sept, 21:00 | 176 MW | 177 MW |
| 13 Sept, 22:00 | 166 MW | 166 MW |
| 13 Sept, 23:00 | 156 MW | 156 MW |
| 14 Sept, 00:00 | 152 MW | 156 MW |
| 14 Sept, 01:00 | 152 MW | 152 MW |
| 14 Sept, 02:00 | 150 MW | 150 MW |
| 14 Sept, 03:00 | 154 MW | 150 MW |
| 14 Sept, 04:00 | 158 MW | 156 MW |
| 14 Sept, 05:00 | 174 MW | 167 MW |
| 14 Sept, 06:00 | 185 MW | 181 MW |
| 14 Sept, 07:00 | 197 MW | 193 MW |
| 14 Sept, 08:00 | 197 MW | 197 MW |
| 14 Sept, 09:00 | 187 MW | 196 MW |
| 14 Sept, 10:00 | 187 MW | 191 MW |
| 14 Sept, 11:00 | 184 MW | 188 MW |
| 14 Sept, 12:00 | 182 MW | 186 MW |
| 14 Sept, 13:00 | 181 MW | 186 MW |
| 14 Sept, 14:00 | 189 MW | 186 MW |
| 14 Sept, 15:00 | 184 MW | 188 MW |
| 14 Sept, 16:00 | 187 MW | 190 MW |
| 14 Sept, 17:00 | 186 MW | 194 MW |
| 14 Sept, 18:00 | 189 MW | 195 MW |
| 14 Sept, 19:00 | 188 MW | 193 MW |
| 14 Sept, 20:00 | 186 MW | 190 MW |
| 14 Sept, 21:00 | 176 MW | 183 MW |
| 14 Sept, 22:00 | 165 MW | 173 MW |
| 14 Sept, 23:00 | 157 MW | 163 MW |
| 15 Sept, 00:00 | 150 MW | 154 MW |
| 15 Sept, 01:00 | 145 MW | 151 MW |
| 15 Sept, 02:00 | 143 MW | 149 MW |
| 15 Sept, 03:00 | 148 MW | 151 MW |
| 15 Sept, 04:00 | 151 MW | 156 MW |
| 15 Sept, 05:00 | 161 MW | 166 MW |
| 15 Sept, 06:00 | 176 MW | 179 MW |
| 15 Sept, 07:00 | 183 MW | 189 MW |
| 15 Sept, 08:00 | 188 MW | 192 MW |
| 15 Sept, 09:00 | 186 MW | 193 MW |
| 15 Sept, 10:00 | 187 MW | 192 MW |
| 15 Sept, 11:00 | 184 MW | 190 MW |
| 15 Sept, 12:00 | 183 MW | 187 MW |
| 15 Sept, 13:00 | 184 MW | 184 MW |
| 15 Sept, 14:00 | 182 MW | 182 MW |
| 15 Sept, 15:00 | 178 MW | 184 MW |
| 15 Sept, 16:00 | 184 MW | 186 MW |
| 15 Sept, 17:00 | 185 MW | 189 MW |
| 15 Sept, 18:00 | 188 MW | 190 MW |
| 15 Sept, 19:00 | 188 MW | 190 MW |
| 15 Sept, 20:00 | 186 MW | 189 MW |
| 15 Sept, 21:00 | 179 MW | 183 MW |
| 15 Sept, 22:00 | 168 MW | 173 MW |
| 15 Sept, 23:00 | 158 MW | 164 MW |
| 16 Sept, 00:00 | 154 MW | 154 MW |
| 16 Sept, 01:00 | 152 MW | 150 MW |
| 16 Sept, 02:00 | 149 MW | 149 MW |
| 16 Sept, 03:00 | 152 MW | 150 MW |
| 16 Sept, 04:00 | 157 MW | 156 MW |
| 16 Sept, 05:00 | 170 MW | 167 MW |
| 16 Sept, 06:00 | 186 MW | 180 MW |
| 16 Sept, 07:00 | 195 MW | 190 MW |
| 16 Sept, 08:00 | 191 MW | 192 MW |
| 16 Sept, 09:00 | 187 MW | 188 MW |
| 16 Sept, 10:00 | 187 MW | 186 MW |
| 16 Sept, 11:00 | 184 MW | 184 MW |
| 16 Sept, 12:00 | 184 MW | 184 MW |
| 16 Sept, 13:00 | 187 MW | 185 MW |
| 16 Sept, 14:00 | 190 MW | 186 MW |
| 16 Sept, 15:00 | 196 MW | 188 MW |
| 16 Sept, 16:00 | 198 MW | 192 MW |
| 16 Sept, 17:00 | 203 MW | 193 MW |
| 16 Sept, 18:00 | 196 MW | 194 MW |
| 16 Sept, 19:00 | 196 MW | 195 MW |
| 16 Sept, 20:00 | 192 MW | 191 MW |
| 16 Sept, 21:00 | 183 MW | 183 MW |
| 16 Sept, 22:00 | 170 MW | 173 MW |
| 16 Sept, 23:00 | 157 MW | 162 MW |
| 17 Sept, 00:00 | 154 MW | 155 MW |
| 17 Sept, 01:00 | 149 MW | 152 MW |
| 17 Sept, 02:00 | 147 MW | 150 MW |
| 17 Sept, 03:00 | 151 MW | 150 MW |
| 17 Sept, 04:00 | 153 MW | 155 MW |
| 17 Sept, 05:00 | 166 MW | 165 MW |
| 17 Sept, 06:00 | 183 MW | 177 MW |
| 17 Sept, 07:00 | 192 MW | 187 MW |
| 17 Sept, 08:00 | 189 MW | 189 MW |
| 17 Sept, 09:00 | 188 MW | 189 MW |
| 17 Sept, 10:00 | 182 MW | 189 MW |
| 17 Sept, 11:00 | 185 MW | 189 MW |
| 17 Sept, 12:00 | 184 MW | 189 MW |
| 17 Sept, 13:00 | 191 MW | 192 MW |
| 17 Sept, 14:00 | 194 MW | 195 MW |
| 17 Sept, 15:00 | 198 MW | 201 MW |
| 17 Sept, 16:00 | 206 MW | 205 MW |
| 17 Sept, 17:00 | 210 MW | 208 MW |
| 17 Sept, 18:00 | 202 MW | 207 MW |
| 17 Sept, 19:00 | 201 MW | 203 MW |
| 17 Sept, 20:00 | 193 MW | 198 MW |
| 17 Sept, 21:00 | 182 MW | 190 MW |
| 17 Sept, 22:00 | 170 MW | 178 MW |
| 17 Sept, 23:00 | 161 MW | 166 MW |
| 18 Sept, 00:00 | 151 MW | 155 MW |
| 18 Sept, 01:00 | 148 MW | 152 MW |
| 18 Sept, 02:00 | 148 MW | 150 MW |
| 18 Sept, 03:00 | 146 MW | 150 MW |
| 18 Sept, 04:00 | 151 MW | 154 MW |
| 18 Sept, 05:00 | 160 MW | 162 MW |
| 18 Sept, 06:00 | 177 MW | 174 MW |
| 18 Sept, 07:00 | 183 MW | 183 MW |
| 18 Sept, 08:00 | 186 MW | 186 MW |
| 18 Sept, 09:00 | 186 MW | 186 MW |
| 18 Sept, 10:00 | 186 MW | 187 MW |
| 18 Sept, 11:00 | 190 MW | 188 MW |
| 18 Sept, 12:00 | 190 MW | 188 MW |
| 18 Sept, 13:00 | 193 MW | 192 MW |
| 18 Sept, 14:00 | 198 MW | 195 MW |
| 18 Sept, 15:00 | 206 MW | 201 MW |
| 18 Sept, 16:00 | 212 MW | 205 MW |
| 18 Sept, 17:00 | 214 MW | 206 MW |
| 18 Sept, 18:00 | 205 MW | 203 MW |
| 18 Sept, 19:00 | 200 MW | 198 MW |
| 18 Sept, 20:00 | 191 MW | 195 MW |
| 18 Sept, 21:00 | 186 MW | 187 MW |
| 18 Sept, 22:00 | 170 MW | 177 MW |
| 18 Sept, 23:00 | 164 MW | 165 MW |
| 19 Sept, 00:00 | 156 MW | 157 MW |
| 19 Sept, 01:00 | 147 MW | 151 MW |
| 19 Sept, 02:00 | 148 MW | 149 MW |
| 19 Sept, 03:00 | 146 MW | 146 MW |
| 19 Sept, 04:00 | 149 MW | 147 MW |
| 19 Sept, 05:00 | 151 MW | 153 MW |
| 19 Sept, 06:00 | 161 MW | 159 MW |
| 19 Sept, 07:00 | 169 MW | 168 MW |
| 19 Sept, 08:00 | 174 MW | 174 MW |
| 19 Sept, 09:00 | 180 MW | 178 MW |
| 19 Sept, 10:00 | 182 MW | 180 MW |
| 19 Sept, 11:00 | 186 MW | 182 MW |
| 19 Sept, 12:00 | 189 MW | 183 MW |
| 19 Sept, 13:00 | 193 MW | 188 MW |
| 19 Sept, 14:00 | 201 MW | 192 MW |
| 19 Sept, 15:00 | 204 MW | 197 MW |
| 19 Sept, 16:00 | 211 MW | 201 MW |
| 19 Sept, 17:00 | 208 MW | 203 MW |
| 19 Sept, 18:00 | 204 MW | 199 MW |
| 19 Sept, 19:00 | 195 MW | 193 MW |
| 19 Sept, 20:00 | 191 MW | 189 MW |
| 19 Sept, 21:00 | 181 MW | 182 MW |
| 19 Sept, 22:00 | 172 MW | 172 MW |
| 19 Sept, 23:00 | 156 MW | 161 MW |
| 20 Sept, 00:00 | 154 MW | 156 MW |
| 20 Sept, 01:00 | 148 MW | 151 MW |
| 20 Sept, 02:00 | 146 MW | 148 MW |
| 20 Sept, 03:00 | 143 MW | 146 MW |
| 20 Sept, 04:00 | 147 MW | 147 MW |
| 20 Sept, 05:00 | 149 MW | 151 MW |
| 20 Sept, 06:00 | 157 MW | 157 MW |
| 20 Sept, 07:00 | 161 MW | 165 MW |
| 20 Sept, 08:00 | 177 MW | 172 MW |
| 20 Sept, 09:00 | 179 MW | 178 MW |
| 20 Sept, 10:00 | 184 MW | 180 MW |
| 20 Sept, 11:00 | 184 MW | 182 MW |
| 20 Sept, 12:00 | 187 MW | 186 MW |
| 20 Sept, 13:00 | 196 MW | 191 MW |
| 20 Sept, 14:00 | 199 MW | 197 MW |
| 20 Sept, 15:00 | 205 MW | 203 MW |
| 20 Sept, 16:00 | 210 MW | 208 MW |
| 20 Sept, 17:00 | 211 MW | 210 MW |
| 20 Sept, 18:00 | 207 MW | 207 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.