I looked into a tankless water heater myself a year or so ago. While I liked the idea of not wasting energy, my plumber talked me out of it. The tankless HWH cannot provide enough water to handle more than one user at a time. If two people are taking showers at the same time, or if the dishwasher or clothes washer is running while you take a shower, there would not be enough hot water to handle it. Also he pointed out that they use more power when they are in use, so a new electric feed would need to be brought in and of course there also needs to be room on the service panel as well. This refers to electric HWHs; I don't have gas available, so that was not an option.