Guide
What is an Electricity Margin Notice?
The short answer
It’s NESO, Great Britain’s electricity system operator, asking generators to make more power available for a set period. It’s routine and nearly always cancelled. It isn’t a warning of power cuts, and there’s nothing for households to do.
What it means
NESO keeps a cushion of spare capacity above expected demand. When it forecasts less cushion than it would like for a period, it issues an Electricity Margin Notice, and generators respond by offering more power. It asks the market for a bigger cushion. It doesn’t mean there isn’t enough electricity.
A real example: 28 September 2026
- 00:30: NESO issued a notice for 16:00–19:00, with a stated shortfall of 1,400 MW.
- 12:00: it updated the shortfall to 104 MW, as more power came forward.
- 15:00: it cancelled the notice, before the period began.
How it fits with the other notices
| NESO’s notice | What it means | Grid Alert says |
|---|---|---|
| Electricity Margin Notice | NESO asks generators for more headroom. Nearly always cancelled. | All clear |
| Capacity Market Notice | An automatic signal that spare capacity may be low. | All clear |
| High Risk of Demand Reduction | A small chance of controlled cuts. Usually stood down. | Heads-up |
| Demand Control Imminent | NESO expects to ask for demand to be reduced shortly. | Get ready |
| Demand Control Rotation Protocol | Areas take turns to be switched off, block by block. | Depends on your rota letter |
Why you may hear more about them
The seven winters from 2019/20 had 8 margin notices between them, and last winter had none. NESO expects to use more system notices this winter, as it changes how it manages the links to our neighbours, and by our records 2026 has already had six margin-notice days since June. More notices don’t mean more danger: most are the system working as it should.
Be the first to know
Grid Alert turns NESO’s official warnings into one clear status for your home. It’s coming this winter, free on Android and iPhone.
Email when live