The National Demand Forecast is made by the System Operator. The System Operator National Demand Forecast is based on historically metered generation output for Great Britain. This value includes transmission losses, but excludes Interconnector flows and demand from station transformers and pumped storage units.

The National Demand Forecast is comparable with the Initial National Demand Out-Turn INDO. All the forecasts are unrestricted, i.e. any notified customer demand management is included in the history.