GB Grid Stability Digest
The week on the grid — 17–23 August 2026
Issue 2026-w34
The system price went negative in 15 settlement periods, bottoming at −£16/MWh.
The system imbalance price peaked at £350/MWh in settlement period 14 on 2026-08-17.
Wind and solar peaked at 51% of GB generation at Sat 13:00.
Vital signs
| This week | vs last week | |
|---|---|---|
| Inertia min / avg / max | 124.5 / 164.3 / 203.9 GVA·s | ▼ −0.6 GVA·s (min) |
| Frequency range (sampled) | 49.827–50.204 Hz · 140 samples beyond ±0.1 Hz | ▲ +0.013 Hz (min) |
| Peak wind + solar share | 51% (Sat 13:00) | ▼ −3.7 pp |
| Peak demand | 24.0 GW (Thu 01:15) | ▼ −0.2 GW |
| System price max / min | £350/MWh / −£16/MWh | ▲ +£1/MWh (max) |
Event of the week
Frequency moved outside 50 ± 0.2 Hz in 1 sampled reading this week, ranging 49.827 Hz–50.204 Hz (15-minute sampling).
Learn: Frequency events, explained
When a large generator trips, frequency falls until reserves respond. The depth of that dip — the nadir — depends directly on system inertia.
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Data: Elexon BMRS · NESO · Carbon Intensity API · Sheffield Solar · All issues
Free to reuse with attribution (CC BY 4.0).