08 Mar 2024
Zach Jennings

ESO publish MEL and MIL guidance for shift to 30-minute rule

The 30-minute rule comes into effect on March 11th. This will allow batteries to be dispatched in the Balancing Mechanism for up to 30 minutes rather than 15 currently. The change was initially due to be made on March 1st but was pushed back to allow providers time to adjust their systems for calculating and submitting MEL (Maximum Export Limit) and MIL (Maximum Import Limit) data.

There will be a two-week transition period for MEL and MIL submissions.

The ESO announced it will stagger the introduction of the 30-minute rule between March 11th and 25th. This means providers can submit either 15 or 30-minute data during this period. All providers must have transitioned to submitting 30-minute data by March 25th.

The ESO is asking providers to inform them when they plan to transition from submitting 15-minute MEL / MIL data to 30-minute data. Providers should email the ESO their intended date and time and the associated Balancing Mechanism Unit. The ESO will confirm this, and the unit will be available for 30-minute dispatches.

The ESO is taking this approach to minimize the likelihood of issues with new submission data causing problems with BM dispatch.

MEL and MIL redeclarations need to be adjusted for the 30-minute redeclaration

The new rule means providers need to adjust their MEL and MIL redeclarations when dispatched in the Balancing Mechanism.

Providers will need to calculate the state of charge of their battery at the end of a Bid or Offer and determine the new MEL/MIL. Once the state of charge (SoC) of the battery drops below the level where the current MEL is no longer valid, they should redeclare the new MEL.

The ESO has stated it would not currently enforce the guidance above but would monitor the data submissions.

Providing feedback and sending transition information to the ESO

The ESO has welcomed feedback on this approach and is encouraging providers with concerns to email

The ESO has requested providers to send their transition information in the following format.
Subject Line: Transition to 30-Minute Rule
Email Content: Intended date and time of transition to the 30-minute rule and the BMU affected.

Additionally, the ESO highlighted the importance of previous guidance on reducing total MEL and MIL data submissions during the upcoming transition period. Our summary of that guidance can be found here.