I have one of the Honda 2kw EU2000i generators. Weighs about 50 lbs with gas (1 gal tank). It has an automatic throttle that revs it up with heavy load, or runs low with a light load.I hook it to my shore power cable with an adapter, and tie it to the mast. It is very quiet, and you barely notice it down below. I've only used it a few times, but it will run both the battery charger and the water heater. In the fall it it just as easy to run the engine, as the water will heat up by the time you charge the batts and it warms the cabin, but perhaps in the summer when you don't want the engine heat it would be worthwhile.