I put alternators on the the pressure wash engine and use that for power for the inverter/batteries. I run 3 or 4 cylinder diesels for the my pressure washer and last one I had them install a 270 amp 12v alternator off the front crank, so when the engine is running the second alternator is running. My other engine I run the alternator off the rear pulley opposite the pump. Problem I have with that setup is I run a clutched setup so I can start the engine and engage the pump once the engine warms up. I can also stop the pump without stopping the engine as well, only thing I have to remember to do is turn off the burner as it can kill the batteries if I leave it too long. I also run a battery switch and so I can run from the truck if needed, but it used $3-5 an hour, my pressure washer engine is $.45-.60 an hour, so I don't run the truck unless in a pinch. I ran a stand alone generator though for many years, easy to do, reliable, and easily replaceable if something goes wrong and you need to keep going. Also you can sometimes run an extension cord from an outlet and just use the customers power and save your fuel.