Hi, I am a builder and many of my customers have asked me about these units.
Here are the mainconsiderations:
1. It makes sense to operate a unit that provides hotwater only when you need it rather than storing and re-heating hotwater in an ongoing fashion, thereby shoveling money thru the chimney.
2. Determine how you use your hotwaterconsumption
b) kitchen use
you will probably have not much problem with b) since washing dishes on utensils in the sink is not a major item anymore. Dishwashers now have their own hotwatersupply system.
That leaves a)
you have to understand how the tankless system works. Basically cold water enters a coilsystem that is heated either with gas or electricity.
Critical is the incoming temperature of the water. The colder the more energy is used to supply hot water to the endpoint of use. The capacity to heat that cold water to the desired temperature is regulated by the demand of flow.
Simply put: if you allow the unit more time to heat the waterflow the more hot water you get out of the spout. If you require more quantity than the unit can heat while flowing thru the coil the outflowing water will be reduced in temperature.
In real house-use terms: If you like to feel the "Niagara"flow from your shower you either have to have a "large" capacity heater or the water will be hot enough but lacks the strong flow you are used from your old standby tank system. It becomes a matter of adjusting your use of showering.
For new construction the installation is straight forward.
In Renovation you have to consider probably new supplylines (either gas or electric), check if you have enough room in your electrical panel, upgrade gasline, if gas is used chimneysize and location can be a considerable expense. You cannot run an additional 100 000 BTU heater into your existing chimney per se, meaning you have to come up with additional space which means more renovation cost to enclose and run new chinmey line
We come from Europe and we have had tankless heaters all the time. it did not bother us We also liked the Northamerican way of showering.
In the long run it comes down to operating costs and what you are willing to spend for your comfort.
I have not checked these units for some years now and they probably came up with some solutions for the NA market.
Bosch has always been our favourite product.