Short term operating reserve (STOR) is a service that provides additional active power from generation or demand reduction. 

At certain times of the day, we may need access to sources of extra power to help manage actual demand on the system being greater than forecast or unforeseen generation unavailability. 

Where it is economic to do so, we will procure sources of extra power ahead of time through the STOR service. Providers of the service help to meet the reserve requirement either by providing additional generation or demand reduction. 

The service is open to Balancing Mechanism (BM) and non-BM participants (any technology) with a connection to either the electricity transmission or distribution network with the ability to increase generation or reduce demand by at least 3MW. 

STOR is procured through a daily pay-as-clear auction process for contracts lasting one day. The auction closes at 05:00 for delivery the following service day (05:00-05:00) covering the Firm or ‘Committed Windows’. Providers submit their availability, prices and MW offering prior to the auction.  

 

Technical requirements

STOR Units must have the capability to: 

  • offer a minimum of 3 MW of generation or steady demand reduction. This can be aggregated from more than one site 
  • respond to an instruction within a maximum of 20 minutes 
  • sustain the response for a minimum of two hours 
  • respond again with a recovery period of not more than 1200 minutes 

It is not possible to provide other services at the same time as providing STOR, however, outside of STOR contracted Committed Windows, it is possible to provide other services, as long as doing so does not interfere with your ability to deliver STOR. 

Providers must have the required systems in place to be dispatched – For BM providers this is through the Balancing Mechanism, for non-BM providers instructions and metering data will be through the Platform for Ancillary Services (PAS). 

Rich text

This section contains information on the new Platform for Ancillary Services project.

For any queries relating to PAS, please contact [email protected]

New providers

There are two possible routes to market for STOR:

Committed STOR

Route to market open to both Balancing Mechanism (BM) and non-Balancing Mechanism participants.

A committed service provider must be available to deliver STOR during all availability windows.

The only acceptable reason for unavailability is when the unit or site is technically unable to provide the service.

Optional STOR

  • Route to market is only open to non-BM (Balancing Mechanism ) reserve providers.
  • Optional STOR providers are able to submit MW and utilisation prices via the Platform for Ancillary Services.

We're not obliged to accept and buy all of the services offered, and will not make availability payments for rejected services.

Procurement

From 1 April 2021 STOR is procured through a daily pay-as-clear auction process. The auction closes at 05:00 for service delivery the following day 05:00-05:00

Pre-qualification 

Interested parties must contact [email protected] to register their interest in providing STOR. 

Pre-qualification requirements are to be fully compliant and tested for the Platform for Ancillary Services (PAS) or live in the Balancing Mechanism (BM). 

Providers will need to sign up to the STOR Services Terms by submitting STOR registration form A & B along with a STOR Data Template which captures the unit’s technical and operational details.  

Once this has been completed NGESO will issue Form C. Providers can then participate in the daily Auction and logins to the Auction Platform will be provided. 

Existing providers

NGESO’s objective is to operate the transmission system economically, and the assessment is made consistent with that.

STOR is procured on a daily basis in an auction for contracts lasting one day. Providers submit their availability prices and MW offering prior to the day ahead auction, which is then cleared to secure firm capacity for STOR for lowest availability cost.

We consider the alternative costs for securing short term operating reserve closer to real time, and will compare all STOR bids against the economic costs of procuring the same volume of reserve from alternative sources.

A STOR bid will only be accepted where we consider that the total costs of securing and operating the system are lower with the bid, than without it.

For further details and examples of how the auction works, you can find the STOR assessment principles in the documents library.

There are three types of payment for the STOR service:

Availability payment

This payment is for being available to provide the service within the committed availability window.

Utilisation payment

This payment is for delivering the service when instructed by us. This includes the energy delivered in ramping up to and down from the contracted volume.

Proof of delivery from metered data, which is taken automatically from the unit or sent to National Grid via Excel.

Providers submit their prices for the committed availability window and utilisation during the auction.

Optional utilisation payment

Non-BM providers are able to offer STOR outside the defined availability windows. For these optional periods, they can offer optional utilisation prices should we wish to use the service. No availability payments are made for optional periods.

What providers can expect to be paid

Providers submit their own prices for availability and utilisation during the auction. These prices will inform the economic assessment to determine which parties are accepted.

Related documents

STOR is procured through a daily pay-as-clear auction process for contracts lasting one day. The auction closes at 05:00 for delivery the following service day (05:00-05:00) covering the Firm or ‘Committed Windows’. Providers submit their availability prices and MW offering prior to the auction.  

Committed Windows 

Typically, the service is used over two pre-defined windows: 

  • morning window; and 
  • evening peak window. 

Providers successful in the daily auction are required to be available to operate at their contracted volume during both these Committed Windows. 

STOR may be required outside of these Committed Windows and providers are able to offer this as an Optional STOR service (only open to non-BM providers). 

There are three types of payment for the STOR service: 

  • Availability payment - for being available to provide the service in Committed Windows. 
  • Utilisation payment - for delivering the service when instructed by us, covering the energy delivered in ramping up to and down from the contracted volume. 
  • Optional utilisation payment - for delivering the Optional STOR service when instructed by us. No availability payments are made for optional periods. 

STOR dispatch 

BM providers will be dispatched through the Balancing Mechanism, while non-BM providers will be instructed and metered through the Platform for Ancillary Services (PAS). 

Both Balancing Mechanism (BM) and non-BM participants with a connection to either the electricity transmission or distribution network are able to provide STOR.

The service is open to any technology with the ability to increase generation or reduce demand by at least 3 MW.

There are particular times of the day when the STOR service is more likely to be required. These are known as ‘committed windows’.

Providers are required to be available to operate at their contracted volume during these windows.

Committed windows

Providers are required to be available to operate at their contracted volume during these windows.

Availability windows

Typically, the service is used over two pre-defined windows:

  • morning window; and
  • evening peak window.

Optional STOR may be required outside of these times.

STOR dispatch

BM providers will be dispatched through the Balancing Mechanism, while non-BM participants will be instructed and metered through the Platform for Ancillary Services (PAS)).

Document library

All previous documents relating to STOR are available here to download.

For the latest information and documents, please visit the relevant sections within the STOR menu.

For more generalised help and guidance documents, please see the Balancing Services help and guidance documents.

If you have any further enquiries, please call 01926 654611 or email [email protected].

STOR post-tender reports

Latest news and updates

STOR Season 18 Committed Windows for 2024/25

This document sets out the STOR Season 18 Committed Windows applicable from 1 April 2024 for the STOR day ahead and legacy long-term STOR services.

STOR Season 17 Committed Windows for 2023/24

This document sets out the STOR season 17 (2023/24) Committed Windows applicable from 1 April 2023 for the STOR day ahead service and legacy Long Term contracts.

STOR Season 16 Committed Windows for 2022/23

This document sets out the STOR Season 16 (2022/23) Committed Windows applicable from 1 April 2022 for the STOR day ahead service and Long Term contracts

NGESO response – Article 18 EBGL consultation for proposed changes to the auction algorithm

On 1 October 2021 we have written to Ofgem notifying of proposed changes to the STOR daily auction algorithm (as required under EBGL Article 18). The letter includes Article 18 consultation comments from market participants and NGESO’s responses.

STOR - Algorithm Changes (Q&A)

Download the question and answers from 11 August webinar

STOR - Algorithm Changes (slides)

Download the slides from 11 August webinar

STOR - Algorithm Changes (webinar)

Watch our webinar from 11 August

Update on STOR day ahead auctions

We have today 29 July 2021 published a letter notifying of proposed changes to the STOR daily auction algorithm

Salesforce Platform webinar: Bulk upload functionality (1 July)

Watch the recording of our Bulk upload Salesforce Platform "Show and Tell" webinar.

Salesforce platform webinar (24 February)

Watch the recording of our STOR Day Ahead Procurement Salesforce Platform "Show and Tell" webinar.

STOR Season 15 Committed Windows (10 February)

Find out more about the new STOR Season 15 (2021/2022) Committed Windows, applicable from 1 April 2021 for the new STOR Day Ahead service and for any existing Long Term STOR contracts.

STOR Day Ahead Procurement webinar (15 January)

Watch the recording of our STOR Day Ahead Procurement webinar.

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