Units produce hot water based on the incoming water temperature. A unit advertised with 11GPM of hot water is based on an inlet water temperature being about 70 degrees (Southern Texas, Florida, or Hawaii as an example). In Reno we base the incoming water temperature at 40 degrees (cold part of winter). So an "11GPM" unit will produce 5.2-5.3 GPM of 120 degree water at 80 degrees temperature rise - OR it can be viewed as operating 3 showers simultaneously while someone is doing the dishes.