[tcrist]

You can get one that runs the whole house but you need to watch what size you get because of what "olddog" mentioned about min waterflow.
We have family in Europe and they have smaller ones that service single uses/areas. They do not understand why we do not have them here. Saves on gas/elec trying to keep the water hot as in our water heaters that are normally in the garage way away from the water usage areas. Also there is the instant hot water idea. You are not waisting water waiting for your water to get hot.

Terry