Purchased Energy Rate

We are working on a project consisting of several offices and residential buildings, but LEED boundary is considered only one of the office building. There are 4 ground source heat pumps intended to provide heating and cooling for the whole project, which is considered as "upstream equipment". therefore, we are thinking to follow option1 or as an alternative path applying ASHRAE 90.1-2007 addendum ai. However, I'm confused how to determine the purchased energy rate when the local purchased energy rates is not available. The rates must account for the total costs associated with maintaining the district equipment, and generating and delivering the energy to the project site. Do I need to create another testing model that includes all the buildings outside the LEED boundary to calculate the performance (cost $ /electricity consumption KWh) of the upstream equipment? Or is there any other method to get the rate? Thanks in advance.