Welcome to ECN Forums from one of the 'Jersey Guys'
As to your inquiry, the ESI for PS is a usual request. Basically, a 2 family with a 'house' panel you would take the 'calc loads for each apt, and the common areas and submit a total in KW.
Use the NEC load calcs within the '08 NEC for basic guides.
Have you spoke to the PSE&G wiring inspector? You do not have any 'area' of NJ in your profile.
