I actually called SETI and talked to them about using their tankless unit, according to them, their highest output unit could not supply enough hot water to run more than one thing at a time (shower, dishwasher, etc.). They did not get into multiple units in series, perhaps because of the cost. Since I have a dishwasher and several bathrooms, it was not viable for my situation. These units are big overseas, but remember this is America, where excess is best. 
