Imbalance Pricing

Imbalance Pricing

Pricing and related data used in BSC processes includes:

  • System Sell Price and System Buy Price
  • Market Index Price and Volume
  • Parameters used in the calculation of System Prices (Energy Imbalance Price):
    • NIV – Net Imbalance Volume
    • PAR – Price Average Reference Volume
    • DMAT – De Minimis Acceptance Threshold
    • CADL – Continuous Acceptance Duration Limit
    • MIDS – Market Index Definition Statement
    • LoLP – Loss of Load Probability
    • VoLL – Value of Loss Load
    • RSP – Reserve Scarcity Price
    • Utilisation Price

Where can I find wholesale prices of electricity in Great Britain?

There are price reporting agents outside of ELEXON that can provide this information. ELEXON’s System Prices are for Energy Imbalances after the delivery point rather than  wholesale trading prices.

System Sell Price and System Buy Price

The System Sell Price (SSP) and System Buy Price (SBP) are the ‘cash-out’ or ‘Energy Imbalance’ prices that are used to settle the difference between contracted generation or consumption and the amount that was actually generated or consumed in each half hour trading period.

Pricing data and values

SSP is paid to BSC Trading Parties who have a net surplus of imbalance energy, and SBP is paid by BSC Trading Parties who have a net deficit of imbalance energy.

These prices are designed to reflect the prices associated with the Balancing Mechanism Bids and Offers selected by National Grid to balance the energy flows in the Transmission System, as well as reserve scarcity.

How are System Sell Price and System Buy Price calculated?

For each half hour trading period, the ‘cash-out’ or ‘energy imbalance’ prices (System Sell Price and System Buy Price) will be associated with Balancing Mechanism Bids and Offers accepted by National Grid as well as the Balancing Services used for that specific half hour.

Imbalance Pricing Guidance

Where can I get System Sell Price and System Buy Price data?

Indicative SSP and SBP are reported on (BMRS).

As Settlement data is retrieved and information becomes finalised, more accurate data is published on the ELEXON Portal. You can obtain SSP and SBP (in £/MWh) and the Net Imbalance Volume (NIV) (in MWh) for every Settlement Period in a particular day.

Market Index Data Volume and Price

Market Index Data (MID) is used in the calculation of the Market Index Price for each Settlement Period, and reflects the price of wholesale electricity in the short-term market. You can find an explanation of how it is calculated and used in the Market Index Definition Statement (MIDS).

MID Volume (in MWh) and Price (in £/MWh) for every Settlement can be obtained from the ELEXON Portal.

System Prices (Energy Imbalance Price) parameters

Net Imbalance Volume (NIV)

NIV is the imbalance volume (in MWh) of the total system for a given Settlement Period. It is derived by netting Buy and Sell Actions in the Balancing Mechanism. Where NIV is positive, this means that the system is short and would normally result in the SO accepting Offers to increase generation/decrease consumption. Where NIV is negative, the system is long and the SO would normally accept Bids to reduce generation/increase consumption. It is subject to change via Standard Settlement Runs.

Price Average Reference (PAR) Volume

The Price Averaging Reference (PAR) volume is used to tag Bid-Offer acceptances such that a maximum volume of PAR MWh is used to set the Energy Imbalance Price. The value of PAR is 50MWh and may only be amended by an Approved Modification.

De Minimis Acceptance Threshold (DMAT)

The De Minimis Acceptance Threshold is a parameter used to eliminate Bid/Offer acceptances of small volume (currently less than 1 MWh).

This value is written into the text of BSC Section T Paragraph 1.7  the BSC Panel may review it from time to time.

Proposed revisions to the value of DMAT are consulted upon with the Transmission Company and Trading Parties before a Panel determination is made, and are subject to Ofgem’s approval.

Continuous Acceptance Duration Limit (CADL)

CADL is used to flag short duration Bid-Offer acceptances, associated with system balancing actions in the Energy Imbalance Price calculation.

A Bid-Offer acceptance relating to any given Balancing Mechanism (BM) Unit will be flagged in the system price calculation if it has duration of less than the CADL value in minutes, currently 15 minutes.

CADL is defined in BSC Section T Paragraph 3.1B.

The BSC Panel may revise the value of CADL after consulting with BSC Parties but subject to Ofgem’s approval.

Loss of Load Probability (LoLP)
The LoLP is a measure of system reliability calculated by the System Operator (SO) for each Settlement Period. The System Operator’s methodology is set out in the Loss of Load Probability Calculation Statement.

Value of Loss Load (VoLL)
The VoLL price is an assessment of the average value that electricity consumers attribute to the security of supply. It is currently set at £3,000/MWh.

Reserve Scarcity Price (RSP)
Both accepted BM and non-BM Short Term Operating Reserve (STOR) Actions are included in the calculation of System Prices as individual actions, with a price which is the greater of the Utilisation Price for that action or the RSP. The RSP function is based on the prevailing system scarcity, and is calculated as the product the VoLL and the LoLP for each Settlement Period.

Utilisation Price
The price (in £/MWh) sent by the SO in respect of the utilisation of a STOR Action which:
(i) in relation to a BM STOR Action shall be the Offer Price; and
(ii) in relation to a Non-BM STOR Action shall be the Balancing Services Adjustment Cost.

Market Index Definition Statement (MIDS) Parameters

The Market Index Definition Statement (MIDS) defines two main parameters. These are the Individual Liquidity Threshold (ILT) and (time and product) weightings.

Market Index Data is used in Settlement to calculate a price, expressed in £/MWh in respect of each Settlement Period, which reflects the price of wholesale electricity in Great Britain in the short-term market.

The Market Index Definition Statement (MIDS) defines the parameters for use by the Market Index Data Provider (MIDP) in the provision of Market Index data (MID) to the Settlement Administration Agent (SAA).

The Individual Liquidity Threshold (ILT) and (time and product) weightings parameters are published on the ELEXON Portal.

The Market Index Definition Statement is reviewed by the BSC Panel at least once a year. Any proposed changes are consulted upon with BSC Parties and other interested Parties before the Panel determines that a change is to be made. A change to the MIDS is subject to approval by Ofgem.


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