The National Energy System Operator (NESO) is a government-owned energy system operator for Great Britain, designated as the Independent System Operator and Planner (ISOP) under the Energy Act 2023. NESO is the licensed electricity system operator and balances supply and demand in real time. It has strategic planning roles for electricity networks, and planning and forecasting roles for gas transmission systems.

NESO began operating on 1 October 2024 after the UK government acquired the electricity system operator division of National Grid plc for £630 million. As of December 2025, the chair is Dr Paul Golby and the chief executive is Fintan Slye.

The electricity system operator function in Great Britain was historically performed within the National Grid group. In July 2021, the UK government and Ofgem consulted on proposals to create a new, impartial Future System Operator to support decarbonisation while maintaining security of supply and minimising costs for consumers. The consultation proposed that the new body should take on the main existing electricity system operator roles and should also have longer-term strategic planning and forecasting roles in gas.

Further policy consultation in 2023 described the Future System Operator as intended to be established in public ownership, with operational independence from day-to-day government control, and as a trusted body at the centre of the gas and electricity systems. In March 2024, the Department for Energy Security and Net Zero and Ofgem published a statutory consultation on licences and other regulatory changes for the National Energy System Operator. The consultation covered proposed electricity system operator and gas system planner licences and related changes to implement the new arrangements.

The Energy Act 2023 created a statutory framework for an Independent System Operator and Planner (ISOP) and gave the Secretary of State powers to designate a body to carry out those functions. The framework also provided for new regulatory arrangements, including licences connected to electricity system operation and energy system planning roles.

On 13 September 2024, the Department for Energy Security and Net Zero and Ofgem published a decision notice setting out final decisions to establish NESO and transfer the electricity system operator function into public ownership. The notice provided for the designation of NESO as the ISOP, the granting of a new Gas System Planner licence to NESO, and the replacement of National Grid Electricity System Operator's existing arrangements with a new Electricity System Operator licence. These measures came into effect at midnight on 1 October 2024.

NESO carries out electricity system operator functions in Great Britain, and has energy system planning and forecasting roles under legislation and Ofgem licences.

As the licensed electricity system operator, NESO balances the electricity system in real time so that supply meets demand.