Historical data are shown with the inclusion of the 'old' regional entity names and that information is contained in file marked with the year 2004 or earlier. For the latest reporting, starting in 2005, the current year data are shown in the last row(s) of each file and those data are shown aligned with the updated regional entity names. Each file contains information on the three power grids and/or associated NERC regions. Any revisions to the data will be done within this same format. Data for all historical years are final. Projections for various data elements represent estimates made by industry for reliability planning purposes during the year referenced by the base-year notation found in the table. For data collected on a seasonal basis, summer is defined to cover the period June through September and winter covers December through February. The winter period does overlap the contiguous ending and starting dates for calendar years.

Some files contain both historical and projected data that are related to each other, but only within the year of the filing. For each advancing data year of the files containing both actual and projected data, the earliest projected year period is dropped and a ‘new year’ period added. In all cases, the projected data will change for all years provided within the year covering the filing. Files containing only historical data will be listed in the data sets under an “Actual Only” title.