I was looking into a tankless when I needed to upgrade. From the research I had done at the time if you are on a well you do NOT want a tankless because it will actually use considerably more energy than a tank version because of the cold water coming from the well.
Interesting, I’ve never thought about it like that. Wouldn’t a tank version have to heat the same cold well water that a tankless would? I’d almost think that by introducing very cold well water to the tank with heated water would be less efficient than tankless because each time you add that cold well water, it brings down the whole tank temp and that process is continually repeating itself each time you turn on the tap.
Also, not sure if every system has this but my tankless system is fed by a 20 gallon in-line pre-charged well pressure tank. That tank pulls water from the well and the water sits (at room temp) next to the tankless heater until it is used. So most of the water heated by my tankless system is starting a bit below room temp, not the temp it comes out of the well.
I think the biggest issue with a tankless + well system setup is the fact you have to do a little more maintenance if you have hard water. Some quick google searches seem to have some mixed reviews and almost seems like the “tankless is a bad idea on a well” notion is more and more being called a misconception.