I have a tank, but my girlfriend has a tankless heater in her house. It is pretty cool to turn on the shower or the water and have it be hot right away. She says it is more efficient than when she had a tank. Since it is only her, and occasionally me, in her house it makes more sense. Would have a lot wasted energy keeping water in a tank that sat around all day. So the real question is how much hot water do you use in a day, and how much do you need at one time. You can look up the limitations of a tankless heater. They can’t keep up with excessive demand at once. But if you fit the criteria, you could save a lot of money. When the tank in my place goes bad in a few years, I will probably replace it with tankless. But it’s just me, in my place so I don’t use a lot of hot water.