A Notice of Inadequate System Margin is one of the tools National Grid use to maintain margins in the system and can happen at any time for a variety of reasons. Issuing a NISM does not mean that demand is about to outstrip supply: it is a notice to the market to bring forward further capacity. National Grid issue NISMs ahead of dispatching capacity from its supplementary balancing reserve, which will include 3.5GW of dispatchable generating capacity next winter. This will give any remaining capacity in the market first opportunity to respond but does not signal any significant risk of shortages. National Grid’s objective is to secure supplies and the NISM is an important tool to achieve that objective with minimum distortion to the market.