Most people I see bring genny's to run x-mas lights, power a blender, and don't really use much or to charge batterys, like go-ped batteries, or some kinda electric car batteries.
Modern alternators do put out like 60% at idle now, not like the old days where they put out very little. 12volt batteries take the charge better using an alternator anyway, than useing a charger that plugs into 120volt A/C.
Plus you can have a deep cycle battery in the camp, as a camp battery to use to fill up air mattresses, charge phones, cameras, e-cig chargers, etc. It sucked listening to the neighbors genny to run his x-mas lights, it was a waste.
The car I brought you couldn't hear from 5 feet away. We have used our car as a genny for the last few years on the playa, and it works out well for us.