GB Grid Stability Digest
The week on the grid — 5–11 October 2026
Issue 2026-w41
Frequency spent 11 minutes outside 50 ± 0.2 Hz across 10 separate excursions, the longest 6.5 minutes, ranging 49.740 Hz–50.235 Hz.
The system imbalance price peaked at £415/MWh in settlement period 38 on 2026-10-06.
The system price went negative in 20 settlement periods, bottoming at −£28/MWh.
Vital signs
| This week | vs last week | |
|---|---|---|
| Inertia min / avg / max | 126.2 / 158.2 / 233.6 GVA·s | ▼ −4.3 GVA·s (min) |
| Frequency range | 49.740–50.235 Hz · 45.3 hours beyond ±0.1 Hz | ▼ −0.050 Hz (min) |
| Peak wind + solar share | 74.9% (Sat 11:45) | ▲ +10.9 pp |
| Peak demand | 22.9 GW (Thu 01:15) | ▼ −0.2 GW |
| System price max / min | £415/MWh / −£28/MWh | ▲ +£65/MWh (max) |
Event of the week
KEAD-2, a Keadby Generation Limited fossil gas unit, went out unexpectedly at Fri 11:00, taking 840 MW off the system — back after 99 hours. REMIT gives the cause as "Planned Outage"; 4 other unplanned losses over 300 MW were reported in the week.
Balancing auctions
NESO's day-ahead auction bought £5.62m of frequency response and reserve across 7 delivery days this week.
| Avg price | vs last week | |
|---|---|---|
| Dynamic Containment Low | £5.44/MW/h | ▼ £0.20 |
| Dynamic Containment High | £3.36/MW/h | ▲ £0.14 |
| Dynamic Moderation Low | £10.22/MW/h | ▼ £1.00 |
| Dynamic Moderation High | £2.36/MW/h | ▲ £1.50 |
| Dynamic Regulation Low | £17.99/MW/h | ▼ £3.73 |
| Dynamic Regulation High | −£7.39/MW/h | ▲ £3.70 |
| Positive Quick Reserve | £4.85/MW/h | ▼ £1.22 |
| Negative Quick Reserve | £4.40/MW/h | ▲ £0.79 |
| Positive Balancing Reserve | £2.98/MW/h | ▼ £1.13 |
| Negative Balancing Reserve | £0.00/MW/h | — |
| Positive Slow Reserve | £2.36/MW/h | ▼ £1.59 |
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 8 Demand Flexibility Service events this week (3 turn-down and 5 turn-up) and bought 706 MWh of flexibility for £143k. That is 4% of the 19,800 MWh it asked for.
New on GridHz: every Demand Flexibility Service event analysed, half-hour by half-hour. See what NESO paid, who won, and the price above which NESO turned bids away.
| This week | |
|---|---|
| Events | 8 |
| Cost | £143k |
| Avg accepted price | £202.30/MWh |
| Largest provider | Infinis Limited (48% of MWh) |
Worth reading
- Early winter ENM rings alarm bells
Watt-Logic · 9 Oct — Set a free frequency alert →
Learn: Understanding RoCoF
Rate of Change of Frequency measures how fast grid frequency moves after a disturbance. Protection relays act on it, so operators keep it within tight limits.
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Data: Elexon BMRS · NESO · Carbon Intensity API · Sheffield Solar · All issues
Free to reuse with attribution (CC BY 4.0).