Hello we want to switch our tank for a tankless but the issue is we would have to install an electric one. The service to our house is 100 amp, so I have deduced we would need a 57 amp unit since a 75 amp would be too much load.

My question is this; the 57 amp model we want has a max GPM of 1.8, does that mean it will only let that much water through? Or does it mean from the amount of water that is flowing through, even if the rate is higher than 1.8, only 1.8 would be heated?

We are fine with waiting until the dishwasher is done to take a shower, but we need to know if the water we do get will be hot or if 8GPM is going through, only 1.8 gets heated so the shower will be warm at best? Our incoming water would be approximately 57° and the max temp output for the unit is listed as 105°.