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05 Nov 2021
Neil Weaver

How STOR works - Modo Academy


At certain times of the day, National Grid Electricity System Operator, or ESO, needs to access extra power, either in the form of increased generation or reduced demand. This enables the ESO to manage greater than forecast demand on the transmission system within a relatively short period of time. To do this, the ESO needs fast on-demand generation. 

The ESO buys Short Term Operating Reserve, or STOR, to achieve this. STOR is a balancing service in which the provider delivers standby or emergency power when required. The ESO procures the amount of capacity it thinks it might need via auction. These are day-ahead auctions, for availability the following day.

Accepted participants are paid in two ways: firstly, an availability fee per hour for being ready to respond if needed, and then a further utilisation fee for delivered energy if and when they are actually required. Both Balancing Mechanism registered and non-Balacing Mechanism providers are able to participate in STOR. Balancing Mechanism providers are informed of their instruction to dispatch via a Bid-Offer Acceptance, or BOA. To find out more about how this system works, please see our Balancing Mechanism explainer video. Non-Balancing Mechanism providers are informed of their instructions to dispatch via the ESO’s Ancillary Services Dispatch Platform.

To learn more about how STOR works, and to see the rest of our Modo Academy series, be sure to check out the Modo platform.