My Gen. was around 5000 watt. I would turn on the fridge a while then switch to living room lights and cable and tv and 2nd floor lights, then switch to oil burner for heat if needed. PIA but worked.
I've not used the backfeed system yet but the generator ran the side by side refrigerator, a small window unit, an 18" fan and three 13 watt CFL lamps for a few days after Irma all at the same time.