South Africa's electricity through the day
Averaged over 1 621 days, demand runs from 20 609 MW at 02:00 to 28 609 MW at 18:00. The grid has to find 8 001 MW between the quietest hour and the evening peak, every day.
The evening peak
Demand climbs through the afternoon and tops out at 18:00, when people get home and solar output has already collapsed. The grid covers it with the expensive plant it holds in reserve: diesel peakers average 928 MW at 18:00 against 118 MW at 03:00, and pumped storage generates 1 540 MW at 18:00 from water it pumped uphill overnight. Coal barely moves, from 18 670 MW in the small hours to 20 293 MW at the peak.
The solar window
Utility-scale solar PV produces from about 06:00 to 18:00 and peaks at 1 623 MW around 11:00. That is the middle of the day, not the evening, which is why solar on its own does little for the 18:00 problem. Wind is steadier, between 1 069 and 1 542 MW across the day, and it is the one renewable still producing at the peak.
When the grid is cleanest
Carbon intensity is lowest at 794 g/kWh at 18:00 and highest at 880 g/kWh at 04:00. The difference is solar: around midday it pushes the coal share down, and overnight almost everything comes from coal. If a load can be moved, the middle of the day is the cleanest time to run it.
Hour by hour
| Hour | Demand | Coal | Wind | Solar PV | Diesel | Pumped storage | CO2 |
|---|---|---|---|---|---|---|---|
| 00:00 | 21 188 | 18 881 | 1 231 | 0 | 159 | 6 | 875 |
| 01:00 | 20 764 | 18 716 | 1 178 | 0 | 128 | 2 | 877 |
| 02:00 | 20 609 | 18 670 | 1 146 | 0 | 118 | 1 | 879 |
| 03:00 | 20 809 | 18 813 | 1 140 | 0 | 118 | 0 | 880 |
| 04:00 | 21 903 | 19 288 | 1 161 | 0 | 143 | 12 | 880 |
| 05:00 | 23 742 | 19 737 | 1 180 | 3 | 319 | 366 | 866 |
| 06:00 | 25 003 | 19 899 | 1 173 | 104 | 430 | 713 | 847 |
| 07:00 | 25 482 | 19 732 | 1 142 | 490 | 410 | 618 | 830 |
| 08:00 | 26 152 | 19 577 | 1 104 | 1 067 | 426 | 811 | 806 |
| 09:00 | 26 251 | 19 394 | 1 069 | 1 426 | 416 | 731 | 796 |
| 10:00 | 25 988 | 19 202 | 1 073 | 1 572 | 388 | 571 | 795 |
| 11:00 | 25 713 | 19 066 | 1 112 | 1 623 | 362 | 438 | 796 |
| 12:00 | 25 487 | 18 996 | 1 170 | 1 613 | 342 | 360 | 797 |
| 13:00 | 25 324 | 18 966 | 1 243 | 1 560 | 334 | 287 | 798 |
| 14:00 | 25 459 | 19 036 | 1 317 | 1 456 | 351 | 347 | 798 |
| 15:00 | 25 959 | 19 265 | 1 387 | 1 278 | 405 | 534 | 796 |
| 16:00 | 26 777 | 19 664 | 1 448 | 939 | 515 | 714 | 800 |
| 17:00 | 27 589 | 20 065 | 1 508 | 427 | 735 | 1 058 | 802 |
| 18:00 | 28 609 | 20 293 | 1 542 | 97 | 928 | 1 540 | 794 |
| 19:00 | 28 271 | 20 228 | 1 530 | 4 | 889 | 1 505 | 801 |
| 20:00 | 26 826 | 19 985 | 1 485 | 0 | 757 | 980 | 824 |
| 21:00 | 24 940 | 19 694 | 1 415 | 0 | 535 | 337 | 850 |
| 22:00 | 23 213 | 19 457 | 1 352 | 0 | 336 | 114 | 868 |
| 23:00 | 21 922 | 19 138 | 1 290 | 0 | 218 | 24 | 873 |
Averaged over every hour Eskom has published since April 2022, so no single unusual day moves the figures. Times are South African Standard Time. Rooftop solar sits behind the meter and is not included, so the real midday solar contribution is larger than shown here.