My son/ wife live in Connecticuut, in an area where natural gas is
not available. He has (had) a oil fired boiler, that provided both
heat AND hot water.

Most recently he has added a pellet stove insert, that WILL provide
(most of) their home heat. He is now considering a tankless water
heater, thus stop using that boiler for (only) their hot water.

Would an electric, tankless Water heater be a viable option ?? (The
oil boiler would then be a Back Up home heating option, but not used
daily/ year round).

He has spoken with a contractor. The contractor recommended a new,
"Expensive Propane Hot water install. That does not seem viable to
me, given that they use a limited amount of hot water daily.