In Great Britain, the National Energy System Operator (NESO/Neso) has new rules (effective around 10 August 2026) allowing it to impose short-notice rolling/rotating power cuts (demand control) as a last-resort measure to prevent a full system collapse during electricity shortages.

Key details from reports (primarily The Telegraph and The Guardian):

NESO can now instruct distribution networks to disconnect enough demand in designated areas to cut electricity use by more than a fifth (or similar large shares), with typically eight hours’ notice. Cuts would last up to about three hours per area and rotate across the country to share the impact.

This is distinct from (and more flexible/quicker than) the government’s longstanding Electricity Supply Emergency Code, which requires Energy Secretary approval, is geared toward prolonged crises (over 24 hours), and has never been invoked. The new protocol is industry-led under Grid Code powers and designed for shorter-duration shortfalls.

NESO already had the ability to disconnect up to ~20% of power at as little as five minutes’ notice in imminent-collapse scenarios. The update expands options for rotating disconnections across more of the demand (with protected sites such as hospitals, water treatment works, and national-security facilities exempt).

NESO has described it as a “last-resort contingency measure” for “the most extreme and unlikely circumstances,” only after other tools (voltage reduction, industrial demand disconnection, etc.) are exhausted. It aims to stabilise the grid and avoid uncontrolled nationwide blackouts.

The changes were approved by the regulator Ofgem and came into effect the week of the reports.

Coverage notes the timing amid broader discussions of grid challenges (renewables integration, margins, weather extremes, etc.), though NESO frames the tool as prudent contingency planning rather than an indication of imminent risk.

No actual widespread use has been reported in the immediate coverage.

The Electricity Supply Emergency Code (ESEC) is the UK Government’s official guidance and framework for managing a prolonged electricity supply emergency in Great Britain. It outlines how to ration electricity fairly through planned “rota load disconnections” (rotating/rolling power cuts) while prioritising critical infrastructure.

It addresses situations defined under:

• Section 96(7) of the Electricity Act 1989 (a “civil emergency” — any natural disaster or other emergency that the Secretary of State believes is or may disrupt electricity supplies).
• Section 3(1)(b) of the Energy Act 1976 (an actual or threatened emergency affecting fuel or electricity supplies requiring exceptional government powers to control energy sources and availability).

The goal is equal distribution of available supply “as far as reasonably practicable,” while keeping Protected Sites (critical national infrastructure such as major hospitals with A&E, water treatment, air traffic control, and certain national-security or continuous-process sites) supplied for as long as possible. Protected Sites are listed on a formal Protected Sites List and must still reduce consumption where possible. Ordinary homes and most businesses cannot qualify as Protected Sites.

How It Works

Rota Load Disconnections: Distribution Network Operators divide their networks into roughly 18 “Load Blocks” (each ~5% of demand, labelled A–U or similar). Blocks are switched off in a rotating schedule, typically for nominal three-hour periods. Severity is scaled by “levels” (higher levels disconnect more blocks). Schedules are published via Activation Schedules issued by the National Energy System Operator (NESO).

Implementation requires government emergency powers (directions under the relevant Acts), usually after advice from the Department for Energy Security and Net Zero (DESNZ) Emergency Response Team and often involving COBR. It is intended for longer-duration shortfalls (typically more than a day), not sudden operational imbalances.

Public appeals for voluntary restraint would normally accompany it. Full restoration follows once generation can meet demand again.

ESEC is not used for day-to-day faults, storm damage, or rapid/short-notice generation shortfalls.

Those are handled by NESO under the Grid Code (including tools such as the newer Demand Control Rotation Protocol). ESEC has never been invoked in practice.

Recent Updates

The guidance was last substantially updated in April 2026 (following a 2023 review) and is published on GOV.UK.

It continues to be reviewed and tested by DESNZ with industry partners.

The full document (including detailed rota plans and Protected Site criteria) is available as a PDF from the official GOV.UK page for the Electricity Supply Emergency Code.

In short, ESEC is the government’s contingency plan for structured, fair electricity rationing during a sustained national or regional supply crisis.