GB Grid Stability Digest
The week on the grid — 12–18 October 2026
Issue 2026-w42
Frequency spent 21 minutes outside 50 ± 0.2 Hz across 23 separate excursions, the longest 4 minutes, ranging 49.751 Hz–50.279 Hz.
The system imbalance price peaked at £263/MWh in settlement period 16 on 2026-10-14.
Wind and solar peaked at 71.3% of GB generation at Tue 14:31.
Vital signs
| This week | vs last week | |
|---|---|---|
| Inertia min / avg / max | 127.7 / 156.2 / 204.4 GVA·s | ▲ +1.4 GVA·s (min) |
| Frequency range | 49.751–50.279 Hz · 53 hours beyond ±0.1 Hz | ▲ +0.011 Hz (min) |
| Peak wind + solar share | 71.3% (Tue 14:31) | ▼ −3.6 pp |
| Peak demand | 22.4 GW (Wed 01:15) | ▼ −0.5 GW |
| System price max / min | £263/MWh / £0/MWh | ▼ −£152/MWh (max) |
Event of the week
PEHE-1, a SSE Thermal Generation fossil gas unit, went out unexpectedly at Sat 22:20, taking 930 MW of its 1180 MW off the system — back after 30 minutes. REMIT gives the cause as "Plant Fault - Steam Turbine"; 4 other unplanned losses over 300 MW were reported in the week.
Balancing auctions
NESO's day-ahead auction bought £4.58m of frequency response and reserve across 7 delivery days this week.
| Avg price | vs last week | |
|---|---|---|
| Dynamic Containment Low | £4.93/MW/h | ▼ £0.51 |
| Dynamic Containment High | £3.41/MW/h | ▲ £0.05 |
| Dynamic Moderation Low | £10.48/MW/h | ▲ £0.26 |
| Dynamic Moderation High | £0.44/MW/h | ▼ £1.92 |
| Dynamic Regulation Low | £18.14/MW/h | ▲ £0.15 |
| Dynamic Regulation High | −£12.63/MW/h | ▼ £5.24 |
| Positive Quick Reserve | £5.36/MW/h | ▲ £0.51 |
| Negative Quick Reserve | £4.81/MW/h | ▲ £0.41 |
| Positive Balancing Reserve | £1.58/MW/h | ▼ £1.40 |
| Negative Balancing Reserve | £0.00/MW/h | unchanged |
| Positive Slow Reserve | £1.35/MW/h | ▼ £1.01 |
Dynamic Regulation High cleared below zero: providers pay to deliver it, because absorbing energy from the grid charges their batteries for free.
Daily auction analysis →Demand flexibility
NESO called 12 Demand Flexibility Service events this week (4 turn-down and 8 turn-up) and bought 581 MWh of flexibility for £115k. That is 2% of the 33,500 MWh it asked for.
| This week | vs last week | |
|---|---|---|
| Events | 12 | ▲ 4 |
| Cost | £115k | ▼ £28k |
| Avg accepted price | £198.19/MWh | ▼ £4.11 |
| Largest provider | Octopus Energy Limited (44% of MWh) |
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.
Read the explainer →Get this in your inbox
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Data: Elexon BMRS · NESO · Carbon Intensity API · Sheffield Solar · All issues
Free to reuse with attribution (CC BY 4.0).