What is a Capacity Market Notice and how is it triggered?

A Capacity Market Notice is a signal four hours in advance that there may be less generation available than National Grid Electricity System Operator (ESO), expects to need to meet national electricity demand on the transmission system taking into account additional operational reserve requirements. The notices are intended to be a signal that the risk of a System Stress Event in the GB electricity network is higher than under normal circumstances.

Capacity Market Notices are communicated automatically by National Grid ESO systems to this website and will typically be issued four hours ahead by using data that is provided by industry participants. The main trigger set by the UK Government is for a Capacity Market Notice to be issued to the industry where the level of available generation is within a 500MW threshold of National Grid ESO's requirement. In such instances the Capacity Market Notice will be communicated with a trigger detailing "Margin below threshold set out in Capacity Market Rules".

However, Capacity Market Notices can also be triggered in response to a "Demand Reduction Instruction" or "Low Frequency Disconnection" event. Where such events take place and a Capacity Market Notice is not already active a discrete Capacity Market Notice shall be issued for four hours' time.