NESO system warning
Electricity Margin Notice, 28 September 2026
Issued 00:26 · 28 September 2026 · cancelled 15:02 on 28 September 2026
Status
Cancelled
Stated shortfall
1,400 MW
Notices published
3
What this means
An Electricity Margin Notice is NESO asking the market for more generation. It is a routine signal that the forecast spare capacity for a given period is thinner than the operator wants, not a warning that the lights are about to go out — margin notices are issued, met by the market, and cancelled.
For how margin notices work and what actually triggers them, see electricity margin notices, explained.
The notices, as published
28 September 2026 00:26
From : Power System Manager – NESO Electricity Control Centre
ELECTRICITY MARGIN NOTICE
An ELECTRICITY MARGIN NOTICE has been issued by the National Energy System Operator to encourage market actions to increase System Margins.
For the period:
from 16:00 hrs to 19:00 hrs on Monday 28/09/2026
There is a reduced system margin. System margin shortfall 1400 MW
The current contingency requirement is 700 MW.
1900 MW of generation is excluded from the available system margin due to system constraints.
Maximum Generation Service may be instructed.
Trading Points, Control Points and Externally interconnected System Operators are requested to notify National Energy System Operator of any additional MW capacity.
Suppliers please advise National Energy System Operator of any additional Demand Control available.
The situation will be reviewed again by National Energy System Operator at 10:00 hours and an update issued.
This Notification of Issue of a GB Transmission System Warning - ELECTRICITY MARGIN NOTICE Issued at 00:30 hrs on 28/09/2026
Issued by Power System Manager NESO Electricity Control Centre
**************
Information Note:-
As the System Operator, National Energy System Operator are responsible for balancing the electricity system in the final hours before real-time. We have a number of routine tools we can use to help us do this, this toolkit includes ELECTRICITY MARGIN NOTICES. An ELECTRICITY MARGIN NOTICE is used to send a signal to the electricity market. It highlights that, in the short-term, we would like a greater safety cushion (margin) between power demand and available supply. It does not signal that blackouts are imminent or that there is not enough generation to meet current demand.28 September 2026 12:00
From : Power System Manager – NESO Electricity Control Centre
ELECTRICITY MARGIN NOTICE
An ELECTRICITY MARGIN NOTICE has been issued by the National Energy System Operator to encourage market actions to increase System Margins.
For the period:
from 16:00 hrs to 19:00 hrs on Monday 28/09/2026
There is a reduced system margin. System margin shortfall 104 MW
The current contingency requirement is 333 MW.
1500 MW of generation is excluded from the available system margin due to system constraints.
Maximum Generation Service may be instructed.
Trading Points, Control Points and Externally interconnected System Operators are requested to notify National Energy System Operator of any additional MW capacity.
Suppliers please advise National Energy System Operator of any additional Demand Control available.
The situation will be reviewed again by National Energy System Operator at 15:00 hours and an update issued.
This Notification of Issue of a GB Transmission System Warning - ELECTRICITY MARGIN NOTICE Issued at 12:00 hrs on 28/09/2026
Issued by Gabriel Diaz NESO Electricity Control Centre
**************
Information Note:-
As the System Operator, National Energy System Operator are responsible for balancing the electricity system in the final hours before real-time. We have a number of routine tools we can use to help us do this, this toolkit includes ELECTRICITY MARGIN NOTICES. An ELECTRICITY MARGIN NOTICE is used to send a signal to the electricity market. It highlights that, in the short-term, we would like a greater safety cushion (margin) between power demand and available supply. It does not signal that blackouts are imminent or that there is not enough generation to meet current demand.28 September 2026 15:02cancellation
From : Power System Manager – NESO Electricity Control Centre NOTIFICATION CANCELLATION of GB TRANSMISSION SYSTEM WARNING The GB Transmission System Warning ELECTRICITY MARGIN NOTICE issued for the period from 16:00 hrs to 19:00 hrs on Monday 28/09/2026 has been cancelled The following GB Transmission System Warnings remain in force None Notification Issued at 15:00 hrs on 28/09/2026 Issued by Power System Manager NESO Electricity Control Centre
Notice text is reproduced verbatim from NESO via the Elexon BMRS SYSWARN dataset. GridHz adds the grouping, timings and context above.