We have a responsibility to keep the National Transmission System (NTS) within safe operating limits. This includes us acting as a balancer by taking energy balancing trades from the On The Day Commodity Market (OCM) and matching it with supply and demand needs. On these pages you will find out more about how we are balancing the NTS.

Margins Notices (MN) and Gas Deficit Warnings (GDW)

How we communicate potential or actual risks to the end-of-day National Transmission System (NTS) physical system balance.

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Operating Margins (OM)

How we use gas to manage short-term impacts of operational stresses (e.g. supply loss) where the market response is not sufficient, or during a gas system emergency.

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Unaccounted for Gas (UAG)

Gas that remains unallocated after accounting for all measured inputs and outputs from the system to ensure correct measurement and billing of its users.

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REMIT (regulation on wholesale energy markets integrity and transparency)

Market participants are obliged to publish ‘inside information’ in respect of businesses or facilities they own or control before they can trade on it.

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Demand Side Response (DSR)

A service developed by gas industry representatives to encourage daily metered (DM) consumers to offer to reduce their gas demand during times of system stress.

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On-the-Day Commodity Market (OCM)

The balancing market operated by the ICE Endex exchange. The OCM is the only market we can use for gas trading, so this is the platform we use in our role as residual balancer.

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Meter validation apps - NGage

Our free app for validating measurements, providing a more transparent picture of metering validation, assuring the gas community that we are monitoring meter assets.

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NTS linepack

The amount of gas within the system at any time, including the acceptable range over which the amount of gas in the network can vary.

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Safety monitors

How we define levels of storage that must be maintained through the winter period, how they function, and how they affect you.

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Network gas supply emergencies (NGSE)

Find more about our emergency arrangements and the processes relating to network gas supply emergencies (NGSE).

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End to end balancing services

Here, we provide an overview of the commercial elements of GB gas balancing activity.

This document outlines the commercial elements of GB gas balancing activity. We hope this guide is concise and easy to follow while giving an overview of gas transmission network balancing activity in Great Britain. 


As System Operator, National Grid and NTS shippers are incentivised to balance NTS inputs and outputs on a daily basis.

Under the Uniform Network Code (UNC), shippers are incentivised to balance their system inputs and outputs and make accurate nominations using the Gemini system.

Financial energy balancing charges, invoiced via Xoserve, may be incurred if shippers are unable to balance their portfolio by the end of the gas day.

The summary document 'Scheduling and Imbalance Charges' provides an overview of energy balancing charges.

Gas Deficit Warning (GDW) subscription service

National Grid offers a free text and email subscription service for Gas Deficit Warnings (GDW).

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Gas query directory

To help you efficiently find the right person to talk to in relation to specific National Transmission System operational gas queries, we have developed the following a contact list and directory. We have based it on the most common queries we receive from our customers. Its purpose is to make finding the right subject matter expert within National Grid, quicker and easier than ever before.

Please note that if your query relates to a home or domestic gas connection or meter exchange, please contact your network operator. You can find who your network operator is on the Energy Networks Association website.  

Download the directory

Transmission operational data

Data for industry analysts including operational data to reduce market uncertainty, ensure equal access to information, and increase information transparency.

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Constraint management

How we manage gas constraint actions and materials to help you understand localised system management.

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