Typically, I will start the generator an hour before people start going to bed so that the AC can take some of the humidity/heat out of the boat. If you continue to run it through the night you should have sufficient charge on your house batteries to get you through the next day. I only run the engines to get in/out of mooring fields & marinas, so battery charging from engines is minimal. YRMV. <img src="http://www.traveltalkonline.com/forums/images/graemlins/Cheers.gif" alt="" />