Hi,
How much water do you think will be used?
As long as it has a good reliable thermostat on it I generally preffer a little extra capacity on the heater - but that's because I live in a cold house in a cool country.
I do have the wireless thermometer reading sitting 18 inches from my nose as I type just to double check everything.
So, in closing, put me down as a "don't know".
dr del