Glossary of terms

Here you can find the meanings of abbreviations, acronyms, and industry terms that we use. 


A2O - Application to offer  

ACER - Agency for the Cooperation of Energy Regulators

ANS - Active Notification System  

ASEP - Aggregated system entry point  

AQ - Annual quantity  

ARA - Annual report and accounts  

Average Winter - The average winter condition that has applied over the last 86 years



BBL - Balgzand - Bacton Line 

bcm - Billion cubic meters 

BEIS - Department for Business, Energy and Industrial Strategy


CAM - Capacity Allocation Mechanism  

CHP - Combined heat and power  

CLoCC - Customer low-cost connections  

Close-Out Date - The last date for information revision on gas flow quantities on the NTS

Closing Linepack (CLP) - The volume of gas held within the NTS at the end of the gas day (06:00hrs)

CM - Capacity Market 

Cold day - A day approaching 0 degrees CWV

Combined Cycle Gas Turbines - A unit where electricity is generated by a gas powered turbine and a second turbine

Composite weather variable (CWV) - A weather variable that is linearly related to non-daily metered gas demand

Compressor - Compressors are used to move gas around the network through high pressure pipes 

CSAT - Customer Satisfaction 

CSEP - Connected system entry point  

CV - Calorific value  

CWV - Composite weather variable  

Cycling rates - The average number of times a reservoir’s working gas volume can be turned over during a specific period of time


D - The gas day  

DA - Day ahead 

DAI - Day-ahead interruptible  

DECC - Department of Energy and Climate Change

DFN - Daily flow notification(s)  

DFO - Delivery facility operator(s)  

DM - Daily metered 

DMC - Daily metered consumer(s)  

DN - Distribution network  

DNO - Distribution network operator  

DSR - Demand side response  


EBI - Energy balancing invoice  

ECQ - Emergency curtailment quantity  

ENA - Energy Networks Association 

ENTSO-G - European Network of Transmission System Operators for Gas  

EOD - End of day  

ETR - European Transparency Regulation


FCF - Firm curtailment factor  

FCO - Full connection offer  

FES - Future Energy Scenarios


GCD - Gas charging discussion  

GDW - Gas deficit warning  

GFOP - Gas Future Operability Planning  

GHG - Greenhouse Gas  

GMRS - Gas Market Reporting System  

GS(M)R - Gas Safety (Management) Regulations  

GSO - Gas System Operator  

GT - Gas transporter  

GTO - Gas Transmission Owner  

GTYS - Gas Ten Year Statement  

GWh - Giga Watt hours that is 1,000,000,000 Watt hours


HAP - Highest accepted price  

HSE - Health and Safety Executive


ICF - Interruptible curtailment factor  

ICO - Initial connection offer  

IECR - Incremental entry capacity release  

Interconnector - Natural gas pipe lines that connect gas transmission systems from other countries to the NTS

IP - Interconnection point  



Kwh - Kilowatt hour


LAP - Lowest accepted price  

LDZ - Local distribution zone  

Linepack - the amount of gas within the system at any time  

LNG - Liquefied natural gas  

Load - The energy demand experienced on a system

Locational balancing actions - A physical market transaction pursuant to which the originating user agrees to make a flow change 

LRS - Long range storage  


Margin - The difference between the level of demand and supply that is available to meet it

Marginal generation (MG) - The less favourable commercial generation option when all the options are ranked in an economic merit order

MCM - Million cubic meters  

MIPI - Market Information Provision Initiative  

MN - Margins notice  

MRS - Medium range storage  

MSEC - Monthly system entry capacity  

MW - Megawatt


NBP – National balancing point  

NDM - Non-daily metered   

NGP - National Grid Property

NGSE - Network gas supply emergencies  

NOA - Network Options Assessment

NSL - Network sensitive load  

NSS - Non Storage Supply 

NTS - National Transmission System  


Obligated - The amount of Baseline Capacity, and any Incremental Capacity that exists, that National Grid is required to make available on every day of the year

OCM - On-the-day commodity market  

Ofgem - Office of Gas and Electricity Markets

OM - Operating Margins  

OPN - Offtake profile nominations  

OTC - Over the counter  

OUG - Own use gas  


PARCA - Planning and Advanced Reservation of Capacity Agreement  

PCLP - Projected closing linepack  

Peak - Denotes the maximum power requirement of a system at a given time, or the amount of power required to supply customers at times when need is greatest

Peak day - The highest demand for gas, or electricity, on any day in that year

PMC - Pipeline Maintenance Centre  

PRI charge - Physical renomination incentive charge  

Projected Closing Linepack - The predicted volume of gas held within the NTS at the end of the gas day (06:00hrs)


QSEC - Quarterly system entry capacity  


RB - Residual Balancer 

REMIT - Regulation on wholesale energy markets integrity and transparency  

RIIO - Revenue = Incentives + Innovation + Outputs  regulatory framework

RMSEC - Remaining monthly system entry capacity  


Safety Monitor - A system to ensure that sufficient gas is held in storage to support those gas consumers whose premises cannot be physically and verifiably isolated from the gas network within a reasonable time period

Safety Monitor Space Requirements - The percentage of all the assumed storage space which is required to satisfy the Safety Monitor

SAP - System average price  

SCCA - Storage curtailment compensation arrangements  

SF - Scaling factor 

SFN - Storage flow notification  

SMP - System marginal price  

SND - Seasonal normal demand  

SO - System operator  

SOF - System Operability Framework

SOQ - Supply Offtake Quantity 

SRS - Short range storage  

SSAT - Stakeholder satisfaction


TO - Transmission owner  

TPC - Transmission Planning Code  

TSS - Transportation Support Services  


UAG - Unaccounted for Gas  

UKCS - United Kingdom Continental Shelf 

UNC - Uniform Network Code  

Undiversified - Undiversified demand is used where location is important, such as for network models


VIP - Visual Improvement Provision

VLDMC - Very large daily metered consumer  


WAP - Weighted average price  

WCD - Weather corrected demand 

WCF - Weather correction factor  

WD - Within day