The Installed Capacity (ICAP) for each Supplier is calculated by the ISO-NE from information provided by the Load Research & Analysis group at National Grid.  The reported ICAP is based on the aggregate of each Supplier’s customers’ contribution to the ISO-NE peak load during the preceding year.  The individual customers’ contributions (tags) are estimated annually.  The daily Supplier requirements are then calculated by tracking customer enrollment changes and shifting load accordingly. Customers’ contributions to ICAP are estimated from either their actual peak hour use, if interval data are available, or load profiles.   A number of adjustments are made to the individual customer peak contributions so that the total is reconciled to National Grid’s total demands (by Load Zone) at the time of the ISO-NE peak.  For each customer, an ICAP tag is calculated from the individual customer peak hour use (actual or estimated) and the following adjustments: 

1. Distribution line losses.  These vary by voltage level.
2. Transmission line losses, including an allocation of ISO-NE high voltage transmission losses.
3. Unaccounted for energy and losses factor, to reconcile the estimates to National Grid’s total demands (by Load Zone) at the time of the ISO-NE peak.