GB Grid Stability Digest
The week on the grid — 6–12 July 2026
Issue 2026-w28
The system price went negative in 27 settlement periods, bottoming at −£31/MWh.
Wind and solar peaked at 65% of GB generation at Sun 13:15 — the highest share in the 3 weeks the digest has tracked.
System inertia ranged from 121.5 GVA·s to 155.3 GVA·s (average 133.3 GVA·s).
Vital signs
| This week | vs last week | |
|---|---|---|
| Inertia min / avg / max | 121.5 / 133.3 / 155.3 GVA·s | ▼ −3.7 GVA·s (min) |
| Frequency range (sampled) | 50.070–50.070 Hz · none beyond ±0.1 Hz | ▼ −0.027 Hz (min) |
| Peak wind + solar share | 65% (Sun 13:15) | ▲ +11.4 pp |
| Peak demand | 21.6 GW (Sun 07:45) | ▲ +1.9 GW |
| System price max / min | £210/MWh / −£31/MWh | ▲ +£17/MWh (max) |
A quiet week
System inertia fell to 121.5 GVA·s at Sun 14:45 — the lowest weekly minimum in the 3 weeks the digest has tracked. The system imbalance price peaked at £210/MWh in settlement period 41 on 2026-07-10. Nothing cleared the bar for an event — no frequency excursion beyond 50 ± 0.3 Hz, no system price above £300/MWh, no unplanned loss over 500 MW, no archive record.
Partial data coverage this week (17 of 168 hours) — coverage grows as snapshot history accumulates.
Worth reading
Learn: Interconnectors and stability
GB trades power with its neighbours over HVDC links. Imports displace domestic generation — which changes how much inertia is on the system.
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Data: Elexon BMRS · NESO · Carbon Intensity API · Sheffield Solar · All issues
Free to reuse with attribution (CC BY 4.0).