What do you mean by equipment loads? Running hours? Please give examples.
Ok, I think you need to use the object link & network to get load summation. Somebody needs to test. Do you use functional hierarchy?
Are you a SAP PM user, expert user, analyst, or IT person? Why do you need the sum figure from SAP PM? Can you not get it from the generated power meter there and also from calculation? Can you not explore in the testing region whether it's possible once you interlinked and networked your equipment such as generators?
What industry are you in, is it power generation?