Jurisdiction(s):
United Kingdom

Related legal acts

Key definition

System Operator definition

What does System Operator mean? In energy and utilities practice, “system operator” describes the entity that runs an electricity or gas transmission system in real time, balancing supply and demand, issuing dispatch instructions, managing constraints and outages, and maintaining security of supply. The term is widely used in licences, industry codes and regulatory practice rather than as a single universal statutory definition; related defined terms such as “transmission system operator (TSO)” appear in UK and Irish legislation and EU‑derived rules. Great Britain: the Electricity System Operator (ESO) function has been undertaken by National Grid ESO, separate from transmission owners; government and Ofgem are establishing an independent...

Great Britain: 2019 split creating NGESO and NGET as TO - licence changes, ring-fencing, code changes and unbundling certification (Archived)

Published by a LexisNexis Energy expert

Practice notes

ARCHIVED: This Practice Note is archived and no longer maintained.

Background and scope

For a comprehensive overview of the nature and functions of the companies within the National Grid plc group, refer to Practice Note: The role of National Grid in the great britain energy market.

This Practice Note sets out, in detail, how the Transmission Owner (TO) and system operator (SO) roles and licences were unbundled in 2019 between National Grid Electricity Transmission plc (NGET) and National Grid Electricity System Operator Limited (NGESO).

The National Energy System Operator (NESO) will be a new, independent public body established under the Energy Act 2023, which received Royal Assent on 26 October 2023. NESO’s remit includes operating the Great Britain electricity system, i.e. taking on the SO function previously carried out by NGESO. Once NESO becomes operational, NGESO will no longer exist. Accordingly, the material in this Practice Note is historical. For further detail on NESO, see Practice Note: The National Energy System Operator (NESO).

However, for the purpose of this Practice Note the principal point is that, before 1 April 2019, the National Grid plc subsidiary, National Grid Electricity...

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Web page updated on 21/05/2026

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