Joel, I'm curious and you may know this..... I too have a 5500 watt gen set, 8250 starting watts. My water tank has dual 4500 watt heating elements. I didn't think my Gen set would run it but my neighbor was convinced it would and if it didn't, the breaker would trip. So, I made sure all other breakers were off and tried the water heater during my last outage (Irene). Hit the breaker for the water heater and it appeared to run fine. I let it run for an hour to heat the water and was able to take a hot shower.
My thinking is dual 4500 watt heating elements= 9,000 watts which exceeds my gen set. Maybe the elements don't require 9,000 watts to start??