i agree the question is how much but also how hot all of the water needs to be... you wash dishes hotter than you wash bodies. If the intake from the street is 3/4 to 1" which i believe most residental is. There is a max flow depending on pressure... where wdrp has accounted for pressure regulation.. at least they said they have there will be a max flow for design if that water could be heated to 150 degrees (roughly 100 degrees delta T) as it flows through the unit i would think that would be enough hot water for the wanderport girl to do her laundry as she takes a nice hot shower