Line Loss Factors


Line Loss Factors are multipliers which are used to scale energy consumed or generated to account for losses on the UK’s Distribution Networks.

How it relates to you

As energy is transported from the point of production to the end user, some of it is lost. Under the BSC arrangements there are two ways in which these losses are accounted for:

  • Losses on the Distribution Networks
  • Losses on the Transmission System

Losses on the Distribution Networks are allocated through the use of Line Loss Factors (LLFs).

LLFs are applied in both Central Volume Allocation and Supplier Volume Allocation.

Authorised Signatory

You must be a Category ‘X’ signatory to submit LLFs together with other documents as set out in BSCP128. We also accept a Category ‘A’ authorised signatory that covers all categories.

Types of Licensed Distribution System Operators

The BSCP128 processes are different for LDSOs that calculate their own Line Loss Factors and those that mirror LLFs, particularly:


An LDSO operating a distribution network directly connected to the Transmission System in their own distribution license area.

Embedded LDSO

An LDSO operating an independent distribution network connected to a Host LDSO’s distribution network. Other scenarios are a nested network, where the embedded network connects via another Embedded LDSOs network to the Host LDSOs network.

Embedded LDSO which mirrors a Host LDSO’s LLFs

When an Embedded LDSO replicates the LLFs from the Host LDSO.

Processing LLFs

The LDSOs provides a LLF methodology statement that explains how they calculate the LLFs. This is reviewed against the principles in BSCP128.

If the methodology meets the principles, it is presented to the ISG and SVG for approval.

Once approved, the LDSOs can then calculate LLFs which then need to be audited by Elexon and approved by the ISG and SVG before being used in Settlement.

Self-assessment documents

Methodology Self-Assessment Document (MSAD) is a self-assessment document the LDSO completes on how the methodology complies with the BSCP128 Principles.

Calculations Self-Assessment Document (CSAD) is a self-assessment document the LDSO completes on how the LLF calculations comply with the approved methodology.

Calculating CVA LLFs

CVA LLFs are multipliers used to scale Meter readings taken at an Embedded site connected to the Distribution System and registered in Central Volume Allocation.

They are applied at a Metering System ID (MSID) level via site Aggregation Rules.

LDSOs must submit values on an annual basis for each site which requires CVA LLFs. They also must submit LLFs for any new sites registered within CVA that use LLFs in their Aggregation Rules.

 Calculating SVA LLFs

SVA LLFs are used in aggregation by the Half Hourly Data Aggregator for Half Hourly Metering Systems and Supplier Volume Allocation Agent for Non Half Hourly (NHH) Metering Systems.

There are roughly 30 million Metering Systems registered in the Supplier Meter Registration Service (SMRS) – the SVA sector of the electricity industry. Many of these are banded together into Line Loss Factor Classes (LLFCs).

The LDSOs must assign the Metering Systems to a given tariff for the purpose of Distribution Use of System (DUoS) charges.

All Metering Systems in a LLFC will have the same LLF values. LLFs differ depending on the time of the year.

The LDSOs need to submit SVA LLF values for all LLFCs on an annual basis, and also for a new LLFC when it is being registered.

Accessing the LLF data

The Elexon Portal holds the latest approved methodology statements and LLFs.

  • Portal site structure: LDSO Data > Losses > CVA Line Loss Factors
  • Portal site structure: LDSO Data > Losses > SVA Line Loss Factors

Changes to LLFCs initiated by Ofgem Review

The numbers of LLFCs in Market Domain Data (MDD) will increase on a large scale, as well as the number of valid set combinations. This is in response to Ofgem’s Targeted Charging Review (TCR).

This large increase in data could impact your network systems. BSC Parties who load LLF files may be impacted, as they will have to load significantly larger numbers of new LLFCs and valid set combinations.

Find out more about the changes and how this impacts you.


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