GB Grid Stability Digest
The week on the grid — 7–13 September 2026
Issue 2026-w37
Frequency spent 11 minutes outside 50 ± 0.2 Hz across 15 separate excursions, the longest 5.3 minutes, ranging 49.744 Hz–50.225 Hz.
The system imbalance price peaked at £277/MWh in settlement period 39 on 2026-09-13.
The system price went negative in 14 settlement periods, bottoming at −£67/MWh.
Vital signs
| This week | vs last week | |
|---|---|---|
| Inertia min / avg / max | 123.7 / 157.3 / 207.7 GVA·s | ▼ −0.3 GVA·s (min) |
| Frequency range | 49.744–50.225 Hz · 45.4 hours beyond ±0.1 Hz | ▼ −0.001 Hz (min) |
| Peak wind + solar share | 70.6% (Sat 14:45) | ▲ +1.1 pp |
| Peak demand | 25.1 GW (Fri 01:15) | ▲ +2.5 GW |
| System price max / min | £277/MWh / −£67/MWh | ▲ +£37/MWh (max) |
Event of the week
PEHE-1, a SSE Thermal Generation fossil gas unit, went out unexpectedly at Thu 01:30, taking 1180 MW off the system — back after 45.5 hours. REMIT gives the cause as "Maintenance"; 4 other unplanned losses over 300 MW were reported in the week.
Learn: Battery storage and grid balancing
Grid-scale batteries respond to frequency deviations in under a second — far faster than thermal plant. They’re now a core part of GB’s stability toolkit.
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Data: Elexon BMRS · NESO · Carbon Intensity API · Sheffield Solar · All issues
Free to reuse with attribution (CC BY 4.0).