Just don't fall for electric...go with gas only...

We have a Noritz (natural gas) and it works very well. If you have specific questions, I'll try to answer them. We've had it about three years and no problems.

We have a Rheem gas one. Only had it a few months but love it so far.

We have had tankless water heaters for 25 years. We have a Takagi gas model right now. It is excellent with none of the problems we have had in the past. Those problems included : issues with o rings, pilot lights blowing out on windy days, and a thermocouple that we could not get locally. A week wait for a thermocouple or a pilot light blown out when your husband is out of town takes some of the joy out of the unit. If you have a gas model, you will need air vents to the unit. We solved that by using louvered doors. They are more expensive to put in. You will see a considerable savings in energy, and you never run out of hot water.

Ours is a Noritz N-084M, 8.4 gal/min at 45 deg temp rise. It's a large unit and runs two showers with ease. I installed it myself, which was a bit of a pain.

In our case, the so-called savings were not worth the up-front cost of the tankless, the new gas meter and line to the street, plus larger supply line to the unit.

I do love how it works though and am happy with the results... just not the cost.

We have two Rinnais, one on each side of the exterior of our home. They have been installed for almost 3 years now and we have had absolutely no problems. They work perfectly. We are about to start the remodel of another house, we will be installing a Rinnai!