Glossary of terms

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


AAHEDC - Assistance for areas with high electricity distribution  

ACER - Agency for the Cooperation of Energy Regulators

ACS - Average cold spell

AI - Artificial Intelligence   

ANM - Active Network Management 

ARA - Annual report and accounts  

Arduous Forecast - A forecast that assumes a generator variability and wind variability against a 1 in 20 and ACS demand forecast

AS - Ancillary Services 



BCA - Bilateral connection agreement  

BEGA - Bilateral embedded generation agreement  

BEIS - Department for Business, Energy and Industrial Strategy

BELLA - Bilateral embedded licence exemptible large power station agreement  

Bipole outages - A combined outage on two associated poles on an interconnector

BM - Balancing Mechanism  

BMU - Balancing Mechanism Unit 

BMRSBalancing Mechanism Reporting System  

BOA - Bid Offer Acceptance 

BS - Balancing Services 

BSAD - Balancing Services Adjustment Data

BSC - Balancing and Settlement Code  

BSSG - Balancing services standing group 

BSUoS - Balancing Services Use of System 


C&S - Contracts and Settlements Team 

CACM - Capacity allocation and congestion management

CACoP - Code Administration Code of Practice  

CBR - Contingency balancing reserve

CBSG - Commercial balancing services group  

CES - Commercial Engineering Services  

CDM - Customer demand management 

CF - Charging Futures 

CfD - Contract for Difference 

ChUG - Charging user group  

Clean Forecast - A forecast that uses data that is largely unadjusted

CM - Capacity Market 

CMN - Capacity Market Notices  

CSAT - Customer Satisfaction 

CUSC - Connection and Use of System Code  


DA - Day ahead 

Darkness peak - Peak evening electricity demand which coincides with lighting up in winter 

DCC - Demand connection code

DECC - Department of Energy and Climate Change

DER - Distributed Energy Resource 

DISBSAD - Disaggregated Balancing Services Adjustment Data

DN - Distribution network  

DNO - Distribution network operator  

DRC - Data Registration Code 

De-rated Generation Availability - Submitted generator data which has been reduced to allow for shortfalls and breakdowns, including imports 

De-rated Margin - The average excess of available generation capacity over peak demand, expressed in percentage terms

De-rating Factor - A percentage applied to notified availability data submitted by power stations to allow for short falls and breakdowns

DSO - Distribution System Operator 

DSR - Demand side response  

DTU - Demand turn up


E&R - Emergency and Restoration

ECIT - Extending Competition in Transmission 

EDL - Electronic dispatch logging

Electricity Forward Agreement - A contract calling for the delivery of and payment for electric power in a future period

EFC - Equivalent Firm Capacity 

EFCC - Enhanced Frequency Control Capability  

EFR - Enhanced frequency response  

EGBL - Electricity balancing guidelines

Embedded - Any generation which is connected directly to the local distribution network, as well as combined heat and power schemes of any scale

Emergency Assistance Service - The potential to change interconnector flows in an emergency situation to a more favourable security of supply position for GB

EMR - Electricity Market Reform  

ENA - Energy Networks Association 

ENC - European network codes  

ENCC - Electricity National Control Centre 

ENTSO-E - European Network of Transmission System Owners for Electricity

ERPS - Enhanced reactive power service  

ESO - Electricity System Operator  

ETO - Electricity Transmission Owner  

ETR - European Transparency Regulation

ETYS - Electricity Ten Year Statement  

EV - Electric vehicles  


FBSR - Future Balancing Services Roadmap 

FCA - Forward capacity allocation

FES - Future Energy Scenarios

FFR - Firm frequency response  

FR - Frequency response 


GBSQSS - GB Security and Quality of Supply Standard 

GC - Grid Code  

GCDF - Grid code development forum  

Generator capacity - The total capacity of all generators

GSG - CUSC governance standing group  

GTMA - Grid Trade Master Agreement

GW - Gigawatt


HSE - Health and Safety Executive

HVDC - High voltage direct current


Interconnector - Electric lines or other electrical plants based within Great Britain which convey electricity between Great Britain and another country or territory


JESG - Joint European stakeholder group  

JPC - Joint planning committee  


Kw - Kilowatt  

Kwh - Kilowatt hour  


LCDP - Large Combustion Plant Directive 

LDTEC - Limited duration transmission entry capacity  

Load - The energy demand experienced on a system

LOLE - Loss of Load Expectation


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

Maximum Generation Service - A facility that allows access to capacity which is outside of the generator's normal operating range in emergency circumstances for up to 2 hours

MBSS - Monthly balancing services summary

MFR - Mandatory frequency response  

MODIS - Market Operation Data Interface System  

MW - Megawatt 


NBM - Non Balancing mechanism unit 

NDP - Network Development Policy 

NETS - National Electricity Transmission System  

NGET - National Grid Electricity Transmission 

NGP - National Grid Property

NISM - Notification of Insufficient System Margin 

NOA - Network Options Assessment

NRAPMNegative Reserve Active Power Margin 

NTS - National Transmission System


Ofgem - Office of Gas and Electricity Markets

OPMR - Operating Planning Margin Requirement 

ORPS - Obligatory reactive power service


PAS - Platform for Ancillary Services 

Peak - 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

PGBT - Pre-Gate Balancing Transaction 

Pumped Storage - Used for converting large quantities of electrical energy to potential energy

PV - Photovoltaic




Restricted - An estimate of the demand after any Customer Demand Management has occurred

RDP - Regional development plan 

REMIT - Regulation on wholesale energy markets integrity and transparency  

RES - Renewable Energy Source 

RfG - Requirements for generators

RIIO - Revenue = Incentives + Innovation + Outputs  regulatory framework


SBR - Supplemental balancing reserve

SF - Scaling factor  

SO - System operator 

SO to SO - System operator to system operator  

SOF - System Operability Framework

SONAR - System Operator Notification and Reporting System

SOQ - Supply offtake quantity  

SQSS - Security and Quality of Supply Standards  

SSAT - Stakeholder satisfaction

STC - System operator Transmission owner Code

STOR - Short-term operating reserve  

STTEC - Short-term transmission entry capacity (firm access service)


TCMF - Transmission charging methodology forum  

TEC - Transmission entry capacity  

TERRE - Trans European Replacement Reserve Exchange 

TNUoS - Transmission Network Use of System  

TO - Transmission owner  

TOGA - Transmission outage and generator availability 

TRW Transmission reinforcement works  

TSD - Transmission system demand 

TWRTransmission works register


UCA - Unit cost allowance


VIP - Visual Improvement Provision


- Watt

WD - Within day

Weekday peak demand - The highest electricity demand expected/observed during each week expected between Monday and Thursday

Winter Peak Demand - The highest electricity demand expected/observed during the winter