Short Term Operating Reserve

Who can participate?










Service Description

Short Term Operating Reserve (STOR) is a service for the provision of additional active power from generation and/or demand reduction. There are two forms of the STOR service Committed and Flexible.

Committed service providers undertake to offer service availability in all of the required availability windows in each season and upon accepting the tender, National Grid commits to buy all services offered. Both BMU and Non-BMU are able to tender Committed service.

Whilst Flexible service providers are not obliged to offer services in all availability windows and National Grid is not obliged to accept and buy all the services offered and only Non-BMU is able to tender for the Flexible service.

Why is it needed?

At certain times of the day National Grid needs reserve power in the form of either generation or demand reduction to be able to deal with actual demand being greater than forecast demand and plant breakdowns. National Grid procures part of this requirement ahead of the day through STOR, where it believes it is economic to do so.

Major Technical Requirements

A STOR provider must be able to:

  • Offer a minimum of 3MW or more of generation or steady demand reduction (this can be from more than one site);
  • Deliver full MW within 240 minutes or less from receiving instructions from National Grid;
  • Provide full MW for at least 2 hours when instructed;
  • Have a Recovery Period after provision of Reserve of not more than 1200 minutes (20 hours);
  • Be able to provide STOR at least 3 times a week.

Procurement Process

STOR is procured via competitive tender with three tender rounds per year. All the interested parties have to fulfil the pre-qualification by signing onto the framework agreement before participating in tender.

The need for STOR varies across the year, the time of week and time of day, being a function of the system demand profile at that time. To reflect it, National Grid splits a year into six Seasons which include both Working Days (including Saturdays) and Non Working Days (Sundays and most Bank Holidays), and specifies the periods in each day that STOR is required. Tenders can tender in for one or more of those seasons. The tender will contain all of the required technical parameters associated with the service, as well as the Availability and Utilisation Prices. Tenders are then assessed by National Grid and either accepted or rejected. Accepted tenders are binding on both parties.


Payment Structure: there are two forms of payment that National Grid will make as part of the service:

Availability Payments (£/MW/h): service providers are paid to make their unit/site available for the STOR service within an Availability Window.

Utilisation Payments (£/MWh): service providers are paid for the energy delivered as instructed by National Grid. This includes the energy delivered in ramping up to and down from the Contracted MW level. For BMU service providers this payment will be effected through the Balancing Mechanism.

BSAD: The calculation of BSAD will include the option fees paid to all service providers. STOR Option Fees feed into the calculation of Buy Price Price Adjuster in accordance with the BSAD Methodology.

Providers may request the instructed volume from non-BMU providers in relation to the utilisation of STOR to be included in the calculation of ABSVD.

Summary of Further Information

STOR Invitation to Tender Pack, STOR Market Information Reports and STOR Relevant Documents can be found through the link below