GB Grid Stability Digest
The week on the grid — 21–27 September 2026
Issue 2026-w39
Frequency spent 30.8 minutes outside 50 ± 0.2 Hz across 42 separate excursions, the longest 2.5 minutes, ranging 49.796 Hz–50.241 Hz.
The system imbalance price peaked at £594/MWh in settlement period 43 on 2026-09-22.
The system price went negative in 17 settlement periods, bottoming at −£28/MWh.
Vital signs
| This week | vs last week | |
|---|---|---|
| Inertia min / avg / max | 127.9 / 165.8 / 220.1 GVA·s | ▲ +2.9 GVA·s (min) |
| Frequency range | 49.796–50.241 Hz · 45.2 hours beyond ±0.1 Hz | ▲ +0.041 Hz (min) |
| Peak wind + solar share | 72.7% (Wed 14:45) | ▼ −4.8 pp |
| Peak demand | 23.2 GW (Fri 01:15) | ▲ +0.3 GW |
| System price max / min | £594/MWh / −£28/MWh | ▲ +£319/MWh (max) |
Event of the week
LAGA-1, a EP UK INVESTMENTS LIMITED fossil gas unit, went out unexpectedly at Mon 07:30, taking 905 MW off the system — back after 60 minutes. REMIT gives the cause as "Turbine". The week's frequency low, 49.796 Hz, came 1 second after a separate 865 MW loss on LAGA-1.
Worth reading
Learn: Net-zero grid challenges
Decarbonising means replacing the heavy spinning plant that stabilised the grid for a century. Inertia is the quiet constraint on how fast that can happen.
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Data: Elexon BMRS · NESO · Carbon Intensity API · Sheffield Solar · All issues
Free to reuse with attribution (CC BY 4.0).