Short-term operating reserve (STOR)

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.

Routes to market

There are two possible routes to market for STOR:

Committed service

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.

Flexible service

  • Route to market is only open to non-BM (Balancing Mechanism ) reserve providers.
  • A commitment to deliver STOR is submitted at the week-ahead stage.

Flexible service providers have more freedom around how many hours and when they wish to make the service available. The advantage of the flexible route is that it offers the ability to change availability frequently to reflect site and market conditions.

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


For the STOR service, the year is divided into six ‘seasons’. Each tender round covers particular seasons, incorporating the technical and price details for that period.

Providers are able to submit tenders for one or more seasons, up to a maximum of two complete financial years.

Before tendering (pre-qualification)

Interested parties must first fulfil the pre-qualification by signing onto a STOR framework agreement. This will capture the unit’s technical and operational details. Once a framework agreement has been signed, potential providers will be able to participate in tenders via the online platform, Ariba.