My Noritz Tankless water heaters are not efficient when used only in the kitchen where the hot water is needed intermittantly during the whole time one is cooking and cleaning up. Even when washing a sink full of dishes. After you wash a couple of items and want to rinse you either have to keep the water flowing almost full force or wait for the unit to turn again and heat the water. All the while wasting water. We have a unit just for the kitchen and we waste all sorts of water either leaving it running or waiting for it to heat.
The second heater is for the bathrooms and it works just fine for the showers and tubs. But, when you are shaving the hot water has to stay on constantly or you turn it on full force for at least 8 to 10 seconds to keep the water hot while shaving(unless you like shaving with luke warm to cold water toward the end of your shave by just turning on the water enough to wash your razor).
I've had the heaters for about 5 months and our water bill is higher just for the two of us and we're using the same water company(the rates haven't changed).
I would consider the heat pump water heaters if I could go back in time.
All the hipe about "continuous and instant" hot water needs to be thoughly analyzed by the customer before deciding if a tankless heater will actually save any money.
Review about: Tankless Gas Water Heater.