IPP — solar BW5 (Generator) — IDM re-bid window
gen_ipp_solar_bw5_01
When a variable plant's day-ahead forecast slips beyond −5% at the IDM gate, the seller can re-bid in the intraday market rather than fall straight into the (more expensive) balancing/imbalance settlement.
Implied under-delivery penalty: SMP × 1.15 or an R2 000/MWh floor, whichever is higher. The floor binds when the SMP is below R1 739,13/MWh. Illustrative, basis pending NERSA (Trading Rules R2 §07 placeholder).
Re-bid window · hour 10
IDM gate timestamp: 2026-05-29T11:25:00Z
Day-ahead award 1399.0 MWh; forecast slipped -18.6% to 1138.4 MWh available — a shortfall of 260.6 MWh. Do nothing and the imbalance bill is R521200.00. There is 840.5 MWh of residual demand to re-bid into at an IDM SMP of R851.80/MWh.
24-hour forecast-slip ledger
| Hr | DAM award | Slip | Revised | Shortfall | Imbalance (do nothing) | Re-bid? |
|---|---|---|---|---|---|---|
| 00 | 0.0 | -8.2% | 0.0 | — | — | — |
| 01 | 0.0 | -8.1% | 0.0 | — | — | — |
| 02 | 0.0 | -0.1% | 0.0 | — | — | — |
| 03 | 0.0 | -17.8% | 0.0 | — | — | — |
| 04 | 0.0 | -6.3% | 0.0 | — | — | — |
| 05 | 0.0 | -6.8% | 0.0 | — | — | — |
| 06 | 0.0 | -13.4% | 0.0 | — | — | — |
| 07 | 407.0 | 3.4% | 420.9 | — | — | — |
| 08 | 790.0 | -15.5% | 667.2 | 122.8 | R245666.67 | eligible |
| 09 | 1127.0 | -4.1% | 1080.5 | 46.5 | R93100.00 | — |
| 10 | 1399.0 | -18.6% | 1138.4 | 260.6 | R521200.00 | eligible |
| 11 | 1590.0 | 0.8% | 1603.3 | — | — | — |
| 12 | 1688.0 | -14.4% | 1445.4 | 242.6 | R485133.33 | eligible |
| 13 | 1688.0 | 0.2% | 1692.0 | — | — | — |
| 14 | 1590.0 | 3.0% | 1637.3 | — | — | — |
| 15 | 1399.0 | -8.8% | 1275.3 | 123.7 | R247366.67 | eligible |
| 16 | 1127.0 | -8.9% | 1026.3 | 100.7 | R201466.67 | eligible |
| 17 | 790.0 | -8.3% | 724.1 | 65.9 | R131866.67 | eligible |
| 18 | 407.0 | 1.7% | 414.1 | — | — | — |
| 19 | 0.0 | -2.8% | 0.0 | — | — | — |
| 20 | 0.0 | -19.5% | 0.0 | — | — | — |
| 21 | 0.0 | -18.5% | 0.0 | — | — | — |
| 22 | 0.0 | -5.8% | 0.0 | — | — | — |
| 23 | 0.0 | 0.5% | 0.0 | — | — | — |