Was considering tankless water heater

[Ombligo]

ours is going on 12 years (takagi OS3 gas), mounted outside for direct venting. Like zoidberg the only complaint is it takes 2-3 minutes to get hot water to the master bath and kitchen (both are at the opposite end of the house) but that was an issue with the water tank as well.

Electric installation can be an issue if you need a new panel put in. I suggested to just have a propane tank buried in the yard for one - cheaper than electric work, even over time.

Pipes are going to be your issue though.That may make the idea a non-starter.